A reply

Correspondence

Central neural blockade andthe compartment syndrome

I should like to comment on the reviewof central neural blockade in children(Anaesthesia 1998; 53: 980–1001). Lowerlimb orthopaedic surgery is cited as anindication for caudal epidural blockade.Such blocks, whilst indicated for electivesurgery, should be used with caution inthe emergency treatment of lower limbfractures. Compartment syndrome is arecognised complication of lower limbtrauma with the development of painbeing central to the diagnosis. Centralneural blockade provides excellentanalgesia but may delay the diagnosisby masking breakthrough pain andmimicking sensory abnormalities seenin late compartment syndrome [1, 2].Measurement of compartmental pres-sures serves only to confirm the diag-nosis of this clinical syndrome [3].

Recently, in our hospital, we had justsuch a case of a 6-year-old child whosustained a midshaft tibial fracture. Thiswas treated with external fixation and acaudal epidural injection using 15 ml of0.25% plain bupivacaine was performedat the end of surgery for postoperativeanalgesia. This provided the child withexcellent pain relief until 7 h after sur-gery when she experienced ever increas-ing pain despite intravenous opioids.Compartment syndrome was diagnosedseveral hours later and was confirmed byelevated compartmental pressures. Afour-compartment fasciotomy was per-formed successfully.

Regional blockade of the fracturedlimb, whilst providing the ideal of excel-lent pain relief in this young age group

[4], may contribute to the delay indiagnosis of this limb-threatening con-dition. It therefore seems prudent toavoid dense blockade in the at-risk limb.

O. RossMayday University Hospital,Thornton Heath,Surrey CR7 7YE, UK

References1 Hyder N, Kessler S, Jennings AG,

De Boer PG. Compartment syndromein tibial shaft fracture missed becauseof a local nerve block. Journal of Boneand Joint Surgery 1996; 78: 499–500.

2 Beerle BJ, Rose RJ. Lower extremitycompartment syndrome fromprolonged lithotomy position notmasked by epidural bupivacaine andfentanyl. Regional Anesthesia 1993; 18:189–90.

3 Martin JT. Compartment syndromes:concepts and perspectives for theanesthesiologist. Anesthesia andAnalgesia 1992; 75: 275–83.

4 Johnson CM. Continuous femoralblockade for analgesia in children withfemoral fracture. Anaesthesia andIntensive Care 1994; 22: 281–3.

A replyDr Ross is absolutely right to remind usthat regional anaesthetic techniquesshould be used with caution in theemergency treatment of limb fractures.He describes a situation which concernsmany people so much that they do notuse regional techniques to provideanalgesia after surgery for fractures. Idiscuss these cases with the orthopaedic

surgeon involved. My orthopaedic col-leagues are generally keen that goodanalgesia is provided for their patientsand are rarely concerned that the childwill develop a compartment syndrome.If there are features of the case whichconcern them, then a regional techniqueis not used and an alternative analgesictechnique is provided. The benefits ofregional anaesthesia under these circum-stances do not justify exposing the childto unnecessary risk but these techniquesdo not appear to worry my orthopaediccolleagues on most occasions.

E. DoyleEdinburgh Sick Children’s NHSTrust,Edinburgh EH9 1LF, UK

Caudal analgesia in children

We read with interest the review byRowney and Doyle (Anaesthesia 1998;53: 980–1001) on regional anaesthesiain children. However, we were disap-pointed that no reference was made tothe use of the cannula-over-needle tech-nique when performing single-shot cau-dals. This technique has been extensivelydescribed [1–5] and is used by manypaediatric anaesthetists in their dailypractice.

One of its main advantages is recogni-tion of correct placement. Inserting acannula into the caudal canal producesthree distinct ‘signs’. The presence of allthree confirms correct placement in theepidural space:1 by virtue of its size, there will be adefinite ‘give’ as the cannula passesthrough the sacrococcygeal ligament;

Anaesthesia, 1999, 54, pages 297–310................................................................................................................................................................................................................................................

297Q 1999 Blackwell Science Ltd

All correspondence should be addressed to Professor M. Harmer, Editor of Anaesthesia, Department of Anaesthetics, University of Wales College ofMedicine, Heath Park, Cardiff CF4 4XN, UK.

Letters (two copies) must be typewritten on one side of the paper only and double spaced with wide margins. Copy should be prepared in the usualstyle and format of the Correspondence section. Authors must follow the advice about references and other matters contained in the Notice toContributors to Anaesthesia printed at the back of each issue. The degree and diplomas of each author must be given in a covering letter personally signedby all the authors.

Correspondence presented in any other style or format may be the subject of considerable delay and may be returned to the author for revision. If theletter comments on a published article in Anaesthesia, please send three copies; otherwise two copies of your letter will suffice.

2 ease of advancement of the cannulawithin the epidural space;3 when sited correctly, there will be asignificant lack of resistance to injection,regardless of cannula gauge and size ofsyringe used.

Unlike a needle, once a cannula isinserted there is little chance of migra-tion or displacement whilst attaching asyringe, aspirating or injecting. Further-more the volume of local anaestheticrequired can be reduced when using along cannula [6].

Our current practice is to use a 22-or 20-gauge ‘Abbocath’ intravenouscannula, 32 mm in length and followArmitage’s regimen [7] for the desiredvolume of local anaesthetic. However,for a midthoracic block we use a51-mm, 20-gauge cannula and reducethe volume of local anaesthetic from1.25 to 1 ml.kgÿ1. To date we have nothad a dural tap.

D. MaloneyR. M. JonesC. GildersleveM. R. W. StaceyUniversity Hospital of Wales,Cardiff CF4 4XW, UK

References1 Owens WD, Slatter EM, Battit GE. A

new technique of caudal anaesthesia.Anesthesiology 1973; 39: 451–3.

2 Gutstein HB. Safe and accurateadministration of paediatric caudalblocks. Anesthesia and Analgesia 1995;81: 429.

3 Norman BJ. Identification of thecaudal epidural space. Anaesthesia 1997;52: 928–9.

4 McEwan AI, Black AE. Paediatricsurgery In: Morgan M, Hall GM, eds.Short Practice of Anaesthesia. London:Chapman & Hall Medical, 1998:337–59.

5 Peutrell JM, Prys-Roberts C. Regionalanalgesia and acute pain managementin children. In: Prys-Roberts C,Brown BR Jr, eds. International Practiceof Anaesthesia, Vol. 2. Oxford:Butterworth-Heinmann, 1996: 1–24.

6 Nakano M, Watanabe E, Yasuoka A,Shimzu Y, Yanagawa F. The reductionin the local anaesthetic dose requiredfor a caudal epidural block in infantsand children using a Teflon cannula.

Masui Japanese Journal of Anesthesiology1991; 40: 1783–6.

7 Armitage EN. Caudal block inchildren. Anaesthesia 1979; 34: 396.

A replyThe use of a cannula-over-needle tech-nique for single-shot caudal epiduralblockade is a well-described and widelyused technique which we should havedescribed in our article. We are gratefulto the correspondents for mentioningthis and describing the advantages ofthe technique.

E. DoyleEdinburgh Sick Children’s Hospital,Edinburgh EH9 1LF, UK

Oral versus rectal diclofenac forpostoperative tonsillectomypain in children

It is recognised that nonsteroidal anti-inflammatory drugs (NSAIDs) can beas effective as opioids for analgesia fol-lowing tonsillectomy [1]. Despite this,there is no consensus regarding dose,route or timing of delivery of thesedrugs. Diclofenac is commonly usedand in our hospital was given per-rectum after induction of anaesthesia.Because of their mode of action it hasbeen suggested that NSAIDs should begiven before tissue damage occurs toinhibit sensitisation of nocioceptors [2].Nordbladh studied children and adultshaving tonsillectomy and demonstratedimproved analgesic efficacy with theuse of pre-operative diclofenac givenrectally [3]. We wished to study thepostoperative analgesic effect of oraldiclofenac compared with our usualrectal route.

Following ethics committee approvaland parental consent, we studied 80children between 2 and 14 years of agepresenting for adenotonsillectomy ortonsillectomy. Patients were randomlyallocated to two groups: Group 1received rectal diclofenac (< 1 mg.kgÿ1)following induction of anaesthesia;Group 2 received the same dosage ofdiclofenac as an oral suspension 2 hbefore surgery. One anaesthetist usedthe same anaesthetic technique for allthe patients: intravenous induction with

propofol 4 mg.kgÿ1, fentanyl 1 mg.kgÿ1

and ondansetron 100 mg.kgÿ1. Intuba-tion was facilitated with suxamethonium0.5 mg.kgÿ1 and anaesthesia was main-tained with spontaneous ventilation ofoxygen, nitrous oxide and halothane viaa Humphrey breathing system. Rectalparacetamol (20 mg.kgÿ1) was given toall patients after induction of anaesthesia.

All patients were operated on by thesame surgeon using the same surgicaltechnique.

Nursing staff were blind to the routeof pre-operative analgesia and per-formed 2-hourly pain scoring. Post-operatively, all patients received oraldiclofenac 1 mg.kgÿ1 8-hourly and oralparacetamol 12.5 mg.kgÿ1 6 hourly.Oral codeine 1 mg.kgÿ1 was prescribedas a rescue analgesia and given if the painscore was above 2.

There was no difference between ourgroups in demographic data, type ofoperation or pre- and postoperativedoses of paracetamol and diclofenac.There was a significant difference inthe amount of rescue analgesia usedbetween the two groups (p� 0.004) inthe first 24 h. Nine patients in the PRgroup required rescue analgesia com-pared to only one patient in the oralgroup. None of our patients had a pro-blem with haemostasis and all were dis-charged home the following day.

We have concluded that the pre-operative oral administrationof diclofenacin our paediatric patients for tonsillec-tomy is safe and more effective than ifgiven PR following anaesthesia and wehave changed our practice.

A. SwanepoelP. SempleSt James’s Hospital,Leeds LS9 7TF, UK

References1 Bone ME, Fell D. A comparison of

rectal diclofenac with intramuscularpapaveretum or placebo for pain relieffollowing tonsillectomy. Anaesthesia1988; 43: 277–80.

2 Campbell WI, Kendrick R,Patterson C. Intravenous diclofenacsodium. Does its administration beforeoperation suppress postoperative pain?Anaesthesia 1990; 45: 763–6.

3 Nordbladh I, Ohlander B, Bjorkman

Correspondence Anaesthesia, 1999, 54, pages 297–310................................................................................................................................................................................................................................................

298 Q 1999 Blackwell Science Ltd

R. Analgesia in tonsillectomy: adouble-blind study on pre and postoperative treatment with diclofenac.Clinical Otolaryngology 1991; 16:554–8.

Acute pain service audit

A recent audit of the postoperative epi-dural service at our hospital has high-lighted an unexpected concern whichwe felt should be reported. It has beenwell established that with the appro-priate training of nursing staff, theadministration of epidural opioids andlocal anaesthetics on surgical wards issafe [1–3]. At the Northern GeneralHospital, patients with epidural infu-sions have been cared for on surgicalwards for 12 years. Nurses make fre-quent observations of various parametersaccording to a protocol, including painon a five-point score and sedation on afour-point score. Each patient is alsoreviewed daily by the acute pain team.Ward nurses must attend a 3-h trainingsession on epidural management and aminimum of 80% of nurses on each wardmust have attended for training beforethose wards are allowed to take patientswith epidural catheters in situ.

During a recent audit of our epiduralanalgesia service, the pain and sedationscores recorded by the acute pain teamwere compared with the observationsmade by ward nurses at approximatelythe same time. Although these two setsof figures were not taken exactly simul-taneously they were close enough toexpect good correlation. Twenty sets ofnotes belonging to patients who hadreceived postoperative epidural analgesiawere selected at random. Of these, 15had figures suitable for comparison,between whom the pain team hadmade a total of 34 visits. Of those whowere rejected, three had incomplete ormissing ward records and the other tworeceived epidurals over the weekend andso were not seen by the pain team. Theresulting 34 pairs of pain and sedationscores were analysed using MS Excel7.0, which gave correlation coefficientsof 0.4 for pain scores and of 0.02 forsedation scores.

From these results it is clear that

despite an extensive training programme,assessment of pain and sedation by wardnurses was not accurate. Since it is theresponsibility of nurses to report anyoversedated patient to medical staff,inaccuracy of their assessment mustpose a risk to patients. This problemwill be investigated further and besubject to repeat audit; however, it isunlikely that such unexpected inaccura-cies are restricted to this hospital andshould therefore be brought to theattention of those involved with epiduralservices elsewhere. We would suggestthat similar audits to validate the obser-vations made by ward nurses are essentialso that training can be adapted as appro-priate. Although nurse training is at issuehere, improvements in safety would onlybe ensured by an expansion of the acutepain service who would be able toreview patients more frequently, 7 daysa week and at night.

J. WigfullE. A. WelchewNorthern General Hospital,Sheffield S5 7AU, UK

References1 Ready BL, Loper KA, Nessly M,

Wild L. Postoperative epiduralmorphine is safe on surgical wards.Anesthesiology 1991; 75: 452–6.

2 Burstal R, Wegener F, Lantry G.Epidural analgesia: Prospective audit of1062 patients. Anaesthesia and IntensiveCare 1998; 26: 165–72.

3 Scott DA, Beilby DSN, McClymont C.Postoperative analgesia using epiduralinfusions of fentanyl with bupivacaine.A prospective analysis of 1014 patients.Anesthesiology 1995; 83: 727–37.

Combined spinal epiduralanaesthesia

The controversy surrounding the tech-nique of combined spinal epidural (CSE)anaesthesia persists [1, 2]. Advocates ofthe needle-through-needle techniquepoint to its simplicity and the need foronly one painful injection [3]. Detractorsof the technique may refer to worksuggesting the technique has a failurerate exceeding 10% [4] and to the fact

that dural puncture in particular may bedifficult to appreciate [5]. In practice,however, a major problem of theneedle-through-needle technique isthat it requires the subarachnoid injec-tion to be performed before epiduralcatheter insertion. This exposes thepatient to the effects of developing sub-arachnoid blockade while the epiduralcatheter is placed and secured. This cancause haemodynamic and blockade pro-blems particularly if there is difficulty inplacing the catheter and especially inobstetric patients as blockade developsso rapidly. Several reports attest to thisproblem [6, 7]. This practical problemhas the potential to lose all the advan-tages of the CSE technique. An epiduralneedle allowing insertion of an 18-gauge epidural catheter while the spinalneedle remains in situ has been reportedbut requires a 29-gauge spinal needle[8]. If the two-needle technique isused, the operator may insert the epi-dural catheter first and perform sub-arachnoid blockade at their leisure.However, this technique can be criti-cised because of the risk of damage tothe epidural catheter by the spinal needle[9] or vice versa [10].

A simple modification permits asafe technique. The subarachnoid spaceis identified with a pencil point needleas for normal spinal blockade. Oncecerebrospinal fluid is seen at the needlehub, the stylet is replaced. The epiduralcatheter is placed, either at the samespinal interspace or at one level cephalad.Once the epidural catheter is in place,the stylet is removed from the spinalneedle and the subarachnoid injectionis performed. The patient may be imme-diately positioned and the anaesthetist’sfull attention can be devoted to the devel-oping spinal blockade. I have reportedthis technique in fuller detail elsewhere[11] but as the technique is suitable fornonobstetric cases I hope it will be ofinterest to a wider audience.

I have audited my last 20 cases withthis technique. There have been no fail-ures of spinal or epidural. Fourteen caseshave been performed with both needlesat the same interspace, there have beenno unexpected high blocks, no back-ache, no postdural puncture headacheand one case of nonspecific headache.

Anaesthesia, 1999, 54, pages 297–310 Correspondence................................................................................................................................................................................................................................................


Of interest is the observation that on fiveoccasions there has been delay in epi-dural catheter insertion due to bloodappearing in the catheter (three occa-sions), pain on advancing the catheter(once) or inability to advance the catheter(once). Were the needle-through-needletechnique used in these circumstances,I believe the choices are to abandonthe CSE technique or to continuewhen routine anaesthetic practicewould demand resiting the epidural.

T. M. CookThe Gallery,Bathwick Hill,Bath BA2 6EQ, UK

References1 Collier CB, Turner MA. Are pencil

point needles safe for subarachnoidblock? Anaesthesia 1998; 53: 411.

2 Morris GN, Kinsella M, Thomas TA.Pencil-point needles and combinedspinal epidural block. Why needlethrough needle? Anaesthesia 1998; 53:1132.

3 Lyons G, Macdonald R, Mikl B.Combined epidural spinal anaesthesiafor Caesarean section. Through theneedle or in separate spaces?Anaesthesia 1992; 47: 199–201.

4 Collis RE, Baxandall ML,Srikantharajah ID, Edge G, KadimNIY, Morgan BM. Combined spinalepidural (CSE) analgesia: technique,management, and outcome of 300mothers. International Journal ofObstetric Anesthesia 1994; 3: 75–8.

5 Joshi GP, McCarroll MC. Evaluationof combined spinal–epiduralanaesthesia using two differenttechniques. Regional Anesthesia 1994;19: 169–74.

6 Roberts E, Brighouse D. Combinedspinal–epidural anaesthesia forCaesarean section. Anaesthesia 1992;47: 1006.

7 Hamilton MJG, Morgan BM.‘Needle-through-needle’ techniquefor combined spinal–extraduralanaesthesia in obstetrics. BritishJournal of Anaesthesia 1992; 68: 327.

8 Simsa J. Use of 29-gauge spinalneedles and a fixation device withcombined spinal epidural technique.Acta Anaesthesiologica Scandinavica1994; 38: 439–41.

9 Kestin IG. Spinal anaesthesia inobstetrics. British Journal of Anaesthesia1991; 66: 596–7.

10 Brownridge P. Spinal anaesthesia inobstetrics. British Journal of Anaesthesia1991; 67: 663.

11 Cook TM. Combined spinalextradural anaesthesia: a newtechnique. International Journal ofObstetric Anesthesia 1999; in press.

In their recent correspondence, Morriset al. described a separate needle techni-que for combined spinal epidural block(CSE) [1]. The authors suggest placingthe spinal 1 to 2 interspaces caudal to theepidural so that the theoretical risk ofpuncture of the catheter by the spinalneedle is avoided. Unfortunately, theyfail to support this with references.Indeed, it has been shown for bothlumbar [2] and thoracic [3, 4] epiduralcatheters that approximately 50% of thecatheter tips are directed caudad, wheninserted through a cephalad-orientatedTuohy needle. The sense of safetyclaimed by the authors may thereforebe false.

W. A. VisserUniversity Hospital Nijmegen,6500 HB Nijmegen,The Netherlands

References1 Morris GN, Kinsella M, Thomas T.

Pencil point needles and combinedspinal epidural block. Why needlethrough needle? Anaesthesia 1998; 53:1132.

2 Tiso RL, Thomas PS, Macadaeg K.Epidural catheter direction and localanesthetic dose. Regional Anesthesia1993; 18: 308–11.

3 Hendriks GWH, Hasenbos MAWM,Gielen MJM, Van Egmond J, BarentzJO. Evaluation of thoracic epiduralcatheter position and migration usingradiopaque catheters. Anaesthesia 1997;52: 457–9.

4 Visser WA, Liem TH, Van Egmond J,Gielen MJM. Extension of sensoryblockade after thoracic epiduraladministration of a test dose oflidocaine at three different levels.Anesthesia and Analgesia 1998; 86:332–5.

Epidural blood patch

It is generally agreed that epidural bloodpatch (EBP) can be used to treat duralpuncture headache (PDPH), providedbacteraemia is absent [1]. This letterconcerns three patients in whom sepsisor the threat of sepsis compromised theuse of an epidural blood patch.

Case 1: contamination of a blood culturebottle with a skin commensalThe patient had experienced an acci-dental lumbar puncture during theinsertion of an epidural. A blood patchwas performed to treat PDPH success-fully. The blood culture, taken routinelyduring the blood patch, revealed agrowth of staphylococcus epidermis.However, the patient always remainedasymptomatic.

Case 2: epidural blood patch followed bycoincident septicaemiaA primigravida, undergoing electiveCaesarean section, had received spinalanaesthesia with a 24G Sprotte needle.The first 3 days after delivery had beencomplicated by abdominal pain, pyrexiaand a polymorph leukocytosis. How-ever, by day 3, her only complaint wasof severe PDPH. On careful examina-tion, she was otherwise well. An epiduralblood patch was performed and thisrelieved her headache. That eveningshe felt generally unwell, with a pyrexiaof 39 8C. She had no signs of meningismand no other localising signs. On thefollowing day, the blood culture taken atthe time of the blood patch showed agrowth of Staphylococcus aureus, sensitiveto flucloxacillin, which she receivedfor 2 weeks. She made an uneventfulrecovery.

Case 3: epidural blood patch followed bypyrexia of unknown originThe patient received a blood patchwhen her PDPH failed to resolve after3 days. This was performed with somedifficulty and at first it gave no relief. Thatevening the headache became severe,with neck stiffness. She was apyrexialbut had a leukocytosis of 18 ×109 cmÿ3,with 70% neutrophils. She was treatedwith ciprofloxacin and metronidazolefor 5 days and had an uneventful recovery.



Postdural puncture headache can besevere. If unrelieved, it occasionally lastsfor weeks [2] and, very occasionally,subdural haematoma has occurred [3].Many patients request pain relief fromPDPH. Bed rest, analgesics and timemay relieve matters. Sumatriptan, anantimigraine drug, had been used,although not always successfully [4].Epidural blood patch is thought towork by compressing the dura, andclotting and sealing the dural puncture[5]. Early reports were promising [6] butit does not always work [2, 7]

These three cases demonstrate someof the complications of epidural bloodpatch. In cases 1 and 2, the patientsreceived blood contaminated from theskin (case 1) or a bacteraemia (case 2). Incases 2 and 3, a differential diagnosis hadto be made, to exclude meningitis. Incase 3, the blood patch did not work atfirst. All three patients were examinedcarefully before performing the bloodpatch, and appeared otherwise well andhad no signs of infection. All three bloodpatches were performed with scrupulousattention to asepsis. It is possible that awhite blood cell count performed priorto the blood patches might have fore-warned of the occult infection in cases 2and 3. However, white cell counts maybe elevated during pregnancy [8].

J. S. SpriggeWirral Hospital,Wirral L49 5PE, UK

References1 Reynolds F. Dural puncture and

headache. British Medical Journal 1993;306: 874–6.

2 Stride PC, Cooper GM. Dural tapsrevisited. A 20 year survey fromBirmingham Maternity Hospital.Anaesthesia 1993; 48: 247–55.

3 Edelman JD, Wingard DW. Subduralhaematomas after lumbar puncture.Anesthesiology 1980; 52: 166–7.

4 Carp H, Singh PJ, Vadhera R,Jayaram A. Effects of the serotonin-receptor agonist sumatriptan on postdural puncture headache: report of sixcases. Anesthesia and Analgesia 1994;79: 180–2.

5 Griffiths AG, Beards SC, Jackson A,Horsman EL. Visualisation ofextradural blood patch for post lumbar

puncture headache by magneticresonance imaging. British Journal ofAnaesthesia 1993; 70: 223–5.

6 Cullen SC. Treatment of post spinalheadache. Anesthesiology 1960; 21:565–6.

7 Berger CW, Crosby ET, Grodecki W.North American survey of themanagement of dural punctureoccurring during labour epiduralanalgesia. Canadian Journal ofAnaesthesia 1998; 45: 110–4.

8 Delgado I, Neubert R,Dudenhausen JW. Changes in whiteblood cells during parturition inmothers and newborn. Gynecology andObstetric Investigations 1994; 38:227–35.

Sevoflurane induction andacute epiglottitis

Fenlon and Pearce (Anaesthesia 1997;52: 285–6) have previously questionedthe suitability of sevoflurane for induc-tion of anaesthesia in acute epiglottitis.However, Milligan (Anaesthesia 1997;52: 810) reports the successful use in achild with such a condition. I haverecently used sevoflurane in a case ofadult epigiottitis.

A 44-year-old man presented with a12-h history of worsening sore throatand stridor. He was tachypnoeic andhad a reduced conscious level. His con-dition did not improve with nebulisedadrenaline or budesonide in the Acci-dent and Emergency department. Herequired ventilatory support and trachealintubation was considered necessary.The patient was pre-oxygenated, theninduced, whilst sitting upright, withincremental increases of sevoflurane to8% in oxygen. Anaesthesia was achievedwithin 2 min. Following an uneventfulinduction, airway obstruction and apnoeaoccurred when the patient was laidsupine. Immediate laryngoscopy was per-formed eliciting no response from thepatient. The larynx was visualised (grade2 view), as was the swollen epiglottis. Bythis time, the patient had started breath-ing and a tracheal tube was passed withease but did elicit a cough. Once intu-bation was confirmed clinically andby capnography, the patient was givenpropofol and vecuronium to maintain

anaesthesia as there were signs of emer-gence from the sevoflurane anaesthesia.

Patient tolerance of high concen-trations of sevoflurane has much tocommend it over halothane in this situa-tion; the rapid onset of anaesthesia washelpful but did lead to apnoea. Manage-ment of the rapid emergence, occurringsoon after the airway is secured, shouldbe considered prior to induction.

P. J. YoungsRoyal Devon and Exeter Hospital,Exeter EX2 5DW, UK

Global pollution – theanaesthetist’s contribution

In 1989, we founded the research groupfor anaesthesia and the environment. Atthat time, the pollution of the environ-ment with nitrous oxide and anaestheticgases was generally regarded as notworthy of note. However, increasingconcern about environmental pollutioncaused by anaesthesia has brought xenonback into discussion.

CFCs, CFsIt was decided at the Montreal andLondon conferences to reduce chloro-fluorocarbon (CFC) emissions globally.The states of the European Communityceased consumption of CFCs completelyon 1 July 1997. Hydrogen-CFCs like thevolatile anaesthetics halothane, enfluraneand isoflurane were only included in theagreements in 1992 (Copenhagen con-ference) and will be completely prohi-bited by the year 2030. The volatileanaesthetics desflurane and sevofluranecontribute less to the destruction of theozone layer as the substances containonly the relatively nonozone-damagingfluorine. In fact, the CFC substitute R134a has a similar structure to desflurane.As the greenhouse gas capacity of theFHCs is high, R 134 was introducedonly after adequate recycling systemshad been developed.

Nitrous oxideThe medical proportion of the nitrogenoxide emissions accounts for about 10%of the global total. Apart from its recog-nised ozone-depleting effect which arisesfrom the breakdown of N2O to NOx,



nitrous oxide is a potent greenhouse gas.Restrictions were established in theKyoto Conference in 1997.

Pollution of the working environmentPossible mechanisms of injury due tochronic exposure to anaesthetic gasesare considered to be carcinogenesis,mutagenicity, teratogenicity and reducedfertility. Various review articles have cri-ticised the results of studies showing thedamaging effects of chronic anaestheticgas exposure, pointing out that cofactorswere ignored. Such criticism overlooksthe fact that these cofactors (exposure tosmoke and fumes, stress, disturbances ofcircadian rhythm, confined workplaces)which are carcinogenic and teratogenicin animal studies also exist in the anaes-thetic workplace. These results do notjustify large-scale prospective studies butrather the total revision of the anaes-thetic workplace.

PropofolOn environmental grounds, some anaes-thetists favour the use of propofol.However, its breakdown leads to theformation of phenol, which is classifiedas ‘2’ on a list ranking from 0 to 3 (0: noenvironmental damage, 3: the highestenvironmental damage). Hence there isan environmental impact of total intra-venous anaesthesia with propofol.

XenonBesides the well-known favourablemedical aspects of xenon, it is our opi-nion that our responsibility includesenvironmental aspects of our work. Atthe last meeting of the Association ofLow Flow Anaesthesia (ALFA) held inBelgium, we were informed that allmajor gas suppliers intend to increasexenon production because of the needsof anaesthesia. Therefore we are hopefulthat xenon will find its way into generalanaesthetic practice.

T. MarxXenon Group,University of Ulm,89070 Ulm, Germany

Sudden death from inhalationof petrol vapour

In adults, hydrocarbon poisoning usuallyoccurs as a result of occupational expo-sure, intentional ingestion or accidentalaspiration during siphoning of fuels [1].Although the most common route ofexposure is by ingestion, inhalationalexposures have been described [2–4].We wish to report a case of cardiacarrest due to inhalation of petrolvapour during siphoning.

A 20-year-old male inserted a 2–2.5-m-long pipe into his car’s fuel tankfor the purpose of petrol siphoning intoa bucket. He kept on siphoning forabout 10–15 min intensely and thensuddenly collapsed. He was taken to anearby hospital in a state of cardio-pulmonary arrest. After being resusci-tated, he became haemodynamicallystable and was transferred to our inten-sive care unit. Neurological examinationrevealed coma with positive light reflexesbilaterally and flexion of extremities topainful stimuli. Mechanical ventilationand supportive therapy was started. Cer-ebral tomography showed extensive cer-ebral oedema. As there was no change inthe patient’s neurological condition at theend of 3 weeks, a diagnosis of vegetativestate as a result of delayed cardiopulmon-ary resuscitation was confirmed. Thepatient died of staphylococcus sepsis onthe 40th day after admission to the ICU.

Petrol siphoning is a common way toempty a fuel tank. Although a simpleand a common method, it may haveserious consequences when petrol isingested or inhaled. Cardiovascular toxi-city is not very common but several casesof sudden death after petrol siphoninghave been reported [2–4]. Inhalation ofhigh concentrations of vapour maycause cardiac arrhythmias presumablyas a result of myocardial sensitisationto circulating catecholamines [1]. It isreported that inhalation of petrol vapourrather than ingestion may cause suddendeath and as vaporisation increases withtemperature, siphoning should be morehazardous in summer [4]. As this inci-dent occurred in November, the factorof temperature did not play a major role.Stress or vigorous activity associatedwith siphoning or sniffing abuse of

petrol are said to be other contributingfactors in sudden death [4, 5].

In this case, we would like to empha-sise that the duration and the intensity ofsiphoning through an unusually longpipe increased the volume of petrolvapour inhaled. Since petrol siphoningis a worldwide method, one would expectmore sudden death cases. Thus, in addi-tion to a faulty method of siphoning, weassume that unknown constitutional fac-tors may play a role in this particular fataloutcome.

D. YorukogluS. SenB. SayginIbni Sina Hospital,Ankara, Turkey

References1 Lewander WJ, Linakis JG.

Hydrocarbons. In: Rippe J, Irwin R,eds. Intensive Care Medicine 2nd edn.Boston: Little Brown, 1991: 1278–84.

2 Bass M. Death from sniffing gasoline(letter). New England Journal of Medicine1978; 299: 203.

3 Bass M. Sudden sniffing death. Journalof the American Medical Association 1970;212: 2075–9.

4 Bass M. Sniffing gasoline (letter).Journal of the American MedicalAssociation 1986; 255: 2604–5.

5 Greer WER, Giovacchini RP. Sniffingup trouble. Inhalation of volatilesubstances. Journal of the AmericanMedical Association 1985; 254: 1721–2.

Magnesium sulphate for thecontrol of spasms in severetetanus

We are in total agreement with theprecautionary measures stressed by Pro-fessor James regarding the need forintensive care with ready availability ofventilatory facilities when controllingspasms of tetanus with magnesium ther-apy [1]. We have now managed 30patients with magnesium therapy onthe same regimen as used in our study[2], with early tracheostomy to protectthe patient from the dangers of reducedrespiratory reserve; 13 of the patientsrequired ventilatory support for varyingperiods of time.



Our experience differs from that ofProfessor James where he found that hispatients ‘rapidly became almost totallyparalysed’. It is unlikely that this couldbe due to the regional differences indisease profile. It would be interestingto know what his patient characteristicswere with regard to age, medical dis-eases (particularly lung pathology), andthe use of drugs such as diazepam. Inour experience, all 13 patients requir-ing ventilatory support were eitherelderly (> 65 years) or had respiratorypathology. We also found that if mag-nesium therapy was commenced in thepresence of sedation with diazepan,muscle weakness developed morerapidly.

Our experiences with repetitive stimu-lation (train of four) of the ulnar nervewere in agreement with the findings ofRamanathan [3] who showed progressiveincrease in the twitch height with mag-nesium therapy, in contrast to the fadeobtained with nondepolarizing relax-ants. Following Professor James’ letter,we measured the twitch height and thedegree of incremental response in twopatients using the ‘TOF Guard’. Areduction of up to 70% of the originaltwitch height was seen after the bolusand infusion of 2 g.hÿ1 of magnesium,but this was associated with sustainedtidal volumes of not less than 5 ml.kgÿ1,although the vital capacity was reduced.It was difficult therefore to find a corre-lation between tidal volumes and twitchheights. This could be explained onthe basis of the findings of Lee whostudied magnesium-induced neuromus-cular blockade in domestic pigs [4]. Hefound an increase in contractile forcewith tetanus and a relative sparing ofthe post-tetanic twitch. These findingsclearly distinguish the magnesium-induced neuromuscular block from thatof curariform blocks and postjunctionalirreversible nondepolarizing (alpha bun-garotoxin) types of neuromuscularblock. This tetanic sparing may implythat physiological functions which aretetanic in nature may well be lessaffected. The fact that the tetanic forcetakes a few seconds to reach maximummay also imply that sustained motionssuch as breathing may be less affectedthan knee jerk or cough. This we found

in our patients for even when the patel-lar reflex was absent, tidal volumes wereadequate.

We are appreciative of the commentsmade by Professor James, for thoughventilatory support can be avoided inthe majority of young patients on mag-nesium therapy (17/30), the need forintensive care and ready availability ofventilatory support cannot be overemphasised.

D. AttygalleN. RodrigoNational Hospital of Sri Lanka,Sri Lanka

References1 James MFM. Magnesium sulphate for

the control of spasms in severe tetanus.Anaesthesia 1998; 53: 605.

2 Attygalle D, Rodrigo N. Magnesiumsulphate for the control of spasms insevere tetanus. Anaesthesia 1997; 52:956–62.

3 Ramanathan J, Baha MS, Pillai R,Angel JJ. Neuromuscular transmissionstudies in pre eclamptic womenreceiving magnesium sulfate. AmericanJournal of Obstetrics and GynecologyYear?; 158: 40–6.

4 Lee C, Zhang X, Kwan WF.Electromyographic andmechanomyographic characteristics ofneuromuscular block by magnesiumsulphate in the pig. British Journal ofAnaesthesia 1996; 76: 278–83.

Gastro-oesophageal refluxduring day case gynaecologicallaparoscopy

A paper entitled ‘Gastro-oesophagealreflux during day case gynaecologicallaparoscopy under positive pressure ven-tilation: laryngeal mask vs. tracheal intu-bation’ has recently been published [1].One would assume that the aim of aclinical trial is to prove or disprove a nullhypothesis; however, this study didneither. We should like to point outthat the number of patients included inthis clinical trial was woefully inadequatewhen one puts the data into a powercalculation to determine the number ofpatients needed to prove or disprove a

null hypothesis in a case-control study ofthis type.

Had Ho et al. used a suitable powercalculation, such as that published byJohn Rawles [2] in the British Journal ofCardiology earlier this year (using thesame incidences of 10% and 40%) itwould have been apparent that theyneeded to include over 120 patients:

n� 2 × ((1.96 ×50 ×75)

� (1.96 × (40 ×60)

� (10 ×90))2/(30)2� 120.25.

If, however, the extremely low inci-dence figures that they produced weresubstituted into this equation, thenumber would be closer to 830 patients:

n� 2 × ((1.96 ×13.3 ×93.35)

� (1.96 × (13.3 ×86.7))2/(6.65)2

� 831.8.

We are therefore left with a study thatdoes not clarify in any way whether theuse of a laryngeal mask is or is not asuitable alternative practice to trachealintubation for day case gynaecologicallaparoscopic procedures. Perhaps Ho etal. should reconsider their statement inthe discussion where they state that theysee little point in extending this other-wise interesting study.

M. T. W. LeeK. E. A. MorrisRoyal Hampshire County Hospital,Winchester SO22 5DG, UK

References1 Ho BYM, Skinner HJ, Mahajan RP.

Gastro-oesophageal reflux during daycase gynaecological laparoscopy underpositive pressure ventilation: laryngealmask vs. tracheal intubation.Anaesthesia 1998; 53: 910–24.

2 Rawles J. Understanding clinical trials:the number of patients required in aclinical trial. The British Journal ofCardiology 1998; 5: 170–1.

A replyMay we thank Drs Lee and Morris fortheir interest in our study. They essen-tially raise two points:1 calculation for the sample size for thestudy;



2 whether or not the study should havebeen extended.

We are pleased to respond to boththese issues as follows.

Point 1We are uncertain regarding what DrsLee and Morris actually mean by ‘suit-able power calculation’. In the formulaethat they have presented it is not clearwhat each number stands for. In theabsence of such essential informationwe find it difficult to infer whether theformulae are actually designed for non-parametric categorical data; we suspectnot. For the calculation of the samplesize in the study, we used the normo-gram and methodology for the categori-cal data which have a binary outcomevariable as described in the textbook byD. G. Altman (i.e. yes or no for gastro-oesophageal reflux [GOR]) [1]. On thebasis of published evidence we expectedthe incidence of GOR of 40% and 10%for two different groups, respectively.Thus the proportions to be comparedwere 0.40 (P1) and 0.10 (P2). Withthese specified values of proportions,we calculated the standardised differenceas (P1ÿ P2) divided by the square rootof P3 (1ÿ P3) where P3� (P1� P2)/2.The standardised difference was 0.7.For an 80% probability of detection ofdifference at significance level of 5%, thenormogram gives a sample size of < 60,with 30 in each group. Therefore, wefail to see how we can agree to thesuggestion that the number of patientsin our study was ‘woefully inadequate’.This suggestion, in our opinion, is woe-fully misplaced.

Point 2Another point they make is that thestudy ‘does not clarify in any waywhether the use of a laryngeal mask isor is not a suitable alternative practice totracheal intubation for day case gynaeco-logical laparoscopic procedures’. Wheredid we claim that the study aimed to doso? In order to answer the questionwhich Lee and Morris ask, the followingneed to be considered: (a) is the LMAassociated with more risk of GOR whencompared with a tracheal tube; (b) doesincreased GOR detected in the loweroesophagus of fasted patients translate

into increased incidence of regurgitationin the pharynx.

Our study was aimed at addressingonly the former point. Because wefound no incidence of GOR in theLMA group (zero out of 30) whencompared with a 13% incidence in thetracheal tube group (four out of 30), wefeel that it is reasonable to conclude thatLMA is not associated with a higherincidence of reflux when comparedwith a tracheal tube in the circumstancesin our study. The question then arises,would the results be any different if onerecruited over 800 patients as suggestedby Lee and Morris. Who knows? Thequestion we wish to raise is whether it isworth extending the study to over 800patients to prove that the use of trachealtubes is associated with a slightly higherrisk of GOR (as compared to LMA)when the airway in these patients isprotected anyway. The 0% incidence ofGOR in the LMA group, statistically,gives 95% confidence that the chanceof such an event is likely to be less that10% [2].

B. HoR. P. MahajanQueen’s Medical Centre,Nottingham NG7 2UH, UK

References1 Altman DG. Clinical trials. In: Practical

Statistics for Medical Research. London:Chapman & Hall, 1991: 438–59.

2 Hanley JA, Lippman-Hand A. Ifnothing goes wrong is everything allright? Journal of American MedicalAssociation 1983; 249: 1743–5.

The Combitube and cervicalspine immobilisation

We read with interest the paper byMercer and Gabbott describing the dif-ficulties inserting a Combitube inpatients whose cervical spine had beenimmobilised in a rigid cervical collar(Anaesthesia 1998; 53: 971–4). Whilstwe accept that it is important to identifypotential difficulties, the technique mustnot deviate from the current acceptedstandard of care, in this case reversing theaccepted teaching of ‘airway mainten-ance with cervical spine protection’. In

trauma patients, airway and ventilationare the first priorities [1]. A Combitube,or any other airway device, should beinserted and checked for position andfunction before the application of a rigidcervical collar while the spine is immo-bilised manually. If a collar has alreadybeen applied, it should be removed andthe cervical spine immobilised manuallywhile the airway is secured. This tech-nique has been found to be effective inimproving the view during laryngo-scopy when a collar has already beenapplied [2], and safe when used intrauma patients [3]. If a Combitubeis chosen to secure the airway andallow ventilation, following this regimenallows the chin to be elevated and facili-tate insertion atraumatically, at the sametime protecting the cervical spine. Wefirmly believe that in the trauma patient,the airway remains the first priority andonly when it is secure should a rigidcollar be used to immobilise the cervicalspine.

C. L. GwinnuttR. KishenHope Hospital,Salford M6 8HD, UK

References1 American College of Surgeons

Committee on Trauma. AdvancedTrauma Life Support for Doctors, 6th edn.Chicago: American College ofSurgeons, 1997.

2 Heath KJ. The effect on laryngoscopyof different cervical spineimmobilisation techniques. Anaesthesia1994; 49: 843–5.

3 Criswell JC, Parr MJA, Nolan JP.Emergency airway management inpatients with cervical spine injuries.Anaesthesia 1994; 49: 900–3.

A replyI agree entirely with the commentsmade. Airway management in traumapatients is always the first priority andit is my standard practice to remove thecervical collar and apply manual in-lineneck stabilisation whenever I deal withthe airway of a trauma victim. Our studyconfirms the importance of this fact foranybody attempting to manage the airwaywith a collar still in situ. Furthermore,



I agree that a collar should not be appliedin the first instance if the airway iscompromised. All this is standard teach-ing practice and we did not wish tosuggest otherwise.

However, it remains a fact that incertain circumstances, particularly in theprehospital environment, there may notalways be enough personnel available toeffectively stabilise the neck manually.Airway management in these situationsmay occur with the collar in situ and thisappears to be standard practice for theHelicopter Emergency Service inLondon [1]. Under these circumstances,aides such as the McCoy laryngoscopemay significantly improve the view atlaryngoscopy [2]. Nevertheless, all thoseinvolved in teaching trauma airway man-agement should continue to uphold thegold standard of removing or not apply-ing the cervical collar until the airway hasbeen secured, provided there are suffi-cient personnel available to manually sta-bilise the neck. I hope our study hasfurther supported this argument.

D. A. GabbottGloucestershire Royal NHS Trust,Gloucester GL1 3NN, UK

References1 Morlay A, Haji-Michael PG,

Mahoney P. Cervical spine controlduring pre-hospital tracheal intubationof trauma victims. Anaesthesia 1995;50: 661.

2 Gabbott DA. Laryngoscopy using theMcCoy laryngoscope after applicationof a cervical collar. Anaesthesia 1996;51: 812–4.

A close shave

It was with some concern that we readof Drs Ames’ and Vincent’s ingeniousairway management in the beardedacute trauma patient, which involvedwrapping cling film around the head(Anaesthesia 1998; 53: 1034–5). All suchpatients who require airway maintenanceare at risk not only from their primaryinjury, but also from any superimposedsecondary insult. It is our contentionthat the above strategy enhances thedanger of secondary injury for manyreasons including:

1 cervical spine immobilisation wouldbe exceedingly difficult;2 anatomical landmarks needed for anassistant to apply effective cricoid pres-sure would be obscured;3 laryngoscopy and the associated ante-rior mandibular displacement wouldbe restricted by layers of cellophane,increasing the incidence of failedintubation;4 internal and external jugular veinsmay be compressed by the technique,potentially increasing intracranial pres-sure in cases of head injury;5 the anaesthetist’s fingers gripping themandible could pierce and dislodge asingle layer of cling film, necessitatingat least several layers to be applied.During which time the patient receivesno supplementary oxygen therapy andrisks a hypoxic insult.

Most Accident and Emergency depart-ments already stock cling film, but its useseems relatively confined to the coverageof burned skin. Plaudits to Drs Ames andVincent for their innovation, but suchpractice should not be widely recom-mended in this clinical setting.

Airway maintenance in the presenceof facial hair can be problematic. In themanagement of the bearded acutetrauma patient, solutions involving con-siderable time locating and applying aswathe of cling film should be sub-stituted for trimming the offendingwhiskers with a ubiquitous razor.

E. W. MooreC. M. CowanRoyal Liverpool University Hospital,Liverpool L7 8XP, UK

Grading of direct laryngoscopy

The study by Yentis and Lee (Anaesthesia1998; 53: 1041–4) on the grading ofdirect laryngoscopy is a welcome contri-bution to the subject. It is to be hopedthat their improved system will be widelyadopted. However, the disadvantage ofmodifying a system (Cormack andLehane) which is itself already a sourceof misapplication is to risk furtherconfusion.

Clearly the main clinical purpose of agrading system for laryngoscopy is toforewarn (or reassure) subsequent anaes-

thetists. The easiest way to do thiswithout ambiguity is diagrammatically.I suggest that whichever scoring systemis adopted in any given hospital, a suit-able series of printed diagrams might beincorporated into the anaesthetic record.The simple line drawings used in Figure1 of the article would, as an example,be ideal for this purpose. Ticking theappropriate box is then all that would berequired to relay this important piece ofinformation.

M. P. DownDryburn Hospital,Durham DH1 5TW, UK

The intubating laryngeal mask(ILMA) in an emergency failedintubation

The intubating laryngeal mask (ILMA)may have a role in difficult intubation[1, 2] but its use has not been reportedin the emergency situation. We encoun-tered a case of ‘can’t intubate, can’tventilate’ in which the ILMA enabledeasy airway control and rapid trachealintubation.

A 67-year-old man was admitted tothe Accident and Emergency Unit witha Glasgow Coma Scale of 5. Trachealintubation was required for airway pro-tection and ventilation. Subarachnoidhaemorrhage was suspected and a CTscan arranged. Neck movement waslimited but the thyromental distancewas normal. After pre-oxygenation andapplication of cricoid pressure, a rapidsequence induction was performedusing thiopentone 50 mg and suxa-methonium 100 mg. The epiglottic tipwas visible on laryngoscopy but intu-bation was impossible even with a gum-elastic bougie. The oxygen saturationdecreased and so gentle mask ventilationwith cricoid pressure was attempted.Despite chin lift, jaw thrust, two-handed mask holding and a Guedelairway, the saturation continued to dete-riorate. A size 4 ILMA was inserted andthe cuff inflated with 30 ml air. Cricoidpressure was maintained except whenthe ILMA tip was inserted into thehypopharynx. The breathing systemwas connected directly to the ILMAand the patient’s lungs were ventilated.



The oxygen saturation improved imme-diately. The patient’s head was put in theneutral position. The ILMA handle waslifted and rotated cephalad to find theoptimal airway seal. The tracheal tubewas passed through but would not passmore than 2 cm from the epiglotticelevating bar. The ILMA position wasreadjusted by rotating out of the mouth< 6 cm and reinserting whilst maintain-ing cricoid pressure. The ILMA waspositioned as before and the trachealtube passed into the trachea confirmedby capnography and auscultation. TheILMA was removed by sliding it overthe tracheal tube using the ‘pusher’supplied. The ILMA was inserted by arelatively experienced user (greater than50 uses).

The CT scan showed a large sub-arachnoid haemorrhage too extensivefor intervention. The patient was trans-ferred to the intensive care unit forconservative management. The ILMAtracheal tube was replaced over abougie for a high-volume/low-pressurecuffed tracheal tube. After 24 h, brainstem death was diagnosed and life sup-port discontinued.

This is the first report of the ILMA ina ‘can’t intubate, can’t ventilate’ situa-tion. It immediately enabled oxygena-tion and airway protection. A laryngealmask (LMA) would have probablyenabled oxygenation but reliable tra-cheal intubation through the LMArequires fibreoptic bronchoscopy and along, 6.5-mm tracheal tube. The Amer-ican Society of Anesthesiologists’ diffi-cult airway algorithm includes the LMAas a conduit for fibreoptic bronchoscopyand as an emergency airway per se [3].The ILMA has several advantages overthe LMA. The stainless steel tube isshorter with a wide internal diameterallowing the passage of a standard length8-mm tracheal tube. The handle allowsthe ILMA position to be manipulatedwith respect to the glottis to enableventilation – there have been no reportsof failed ventilation to date. The ILMAmask has an epiglottic elevating barinstead of aperture bars for easy trachealtube passage. The guiding ramp directsthe tracheal tube into the tracheamaking fibreoptic control unnecessary.The tracheal tube connector is remov-

able allowing the ILMA removal overthe tube. One disadvantage is that theILMA tracheal tube cuffs are relativelyhigh pressure and one is reluctant to usethem for prolonged periods.

The horizontal line on the trachealtube indicates when the tip has reachedthe epiglottic elevating bar. Obstructionto tracheal tube passage 2 cm fromthis point is caused by contact with adownfolded epiglottis or the vestibularwall [4]. The recommendation, as usedin this case, is to withdraw the ILMA< 6 cm before reinserting [4].

H. G. WakelingA. BagwellDorset County Hospital,Dorchester DT1 2JY, UK

References1 Brain AIJ, Verghese C, Addy EV,

Kapila A. The intubating laryngealmask. I. Development of a new devicefor intubation of the trachea. BritishJournal of Anaesthesia 1997; 79:699–703.

2 Brain AIJ, Verghese C, Addy EV,Kapila A, Brimacombe J. Theintubating laryngeal mask. II. Apreliminary clinical report of a newmeans of intubating the trachea. BritishJournal of Anaesthesia 1997; 79: 704–9.

3 Benumof JL. Laryngeal mask airwayand the ASA difficult airwayalgorithm. Anesthesiology 1996; 84:686–99.

4 Brain AIJ, Verghese C, eds. TheIntubating Laryngeal Mask AirwayInstruction Manual, 1st edn.Maidenhead, UK: Intavent Ltd, 1998.

Awareness during cardiacanaesthesia

An anaesthetic technique that provideshaemodynamic stability is essential formost cardiac procedures. For many yearshigh-dose fentanyl anaesthesia has beenthe gold standard in many centres. Thedrawback to this technique is delayedonset of spontaneous respiration aftersurgery. The technique of total intra-venous anaesthesia with propofol andremifentanil provides the opportunityfor earlier extubation after cardiac sur-gery. Remifentanil has a constant context-

sensitive half-life of 3–5 min [1]. Thus,when a remifentanil infusion is stopped,the drug is rapidly cleared from thecirculation at a rate independent of theduration of the infusion. Therefore, it isimportant that the administration ofremifentanil is not inadvertently discon-tinued peri-operatively.

We wish to highlight a potential causeof interruption of intravenous infusionsduring a subgroup of cardiac surgeryoperations. In cases where bicaval can-nulation is employed, such as mitralvalve surgery, it is important to ensurethat the tip of the central venous pressurecatheter is proximal to the superior venacaval snare. As shown in Fig. 1, if thecatheter is placed distal to the snare,anaesthetic drugs may be delivered to aspace not drained by the venous cannu-lae. If remifentanil is administered in thisway, lack of analgesia could rapidlyensue. This complication may beavoided by ensuring that remifentanil isadministered through an intravenouscatheter distant from the caval cannulae.

D. McAtamneyW. McBrideRoyal Victoria Hospital,Belfast BT12 6BA, UK

Reference1 Egan TD. Remifentanil

pharmacokinctics andpharmacodynamics. A preliminaryappraisal. Clinical Pharmacokinetics 1995;29: 80–94.



Figure 1 Schematic diagram showing aCVP catheter inserted beyond the SVCsnare in a procedure requiring both SVCand IVC cannulation.

Raynaud’s phenomenon andpropofol

Pain is a well-recognised accompanimentof propofol induction of general anaes-thesia and various measures to prevent it,including the addition of lignocaine andinjection into a vein in the antecubitalfossa rather than one in the dorsum of thehand [1], have been described, thoughnone is always effective. I recently anaes-thetised a 36-year-old man with severeRaynaud’s phenomenon, including ahistory of skin ulceration, for a laparo-scopic antireflux procedure, using apropofol 2% – lignocaine mixture,administered, perhaps inadvisedly, intoa vein on the dorsum of his hand. He notonly immediately complained of agonis-ing pain, but afterwards told me it wasthe worst pain of his life and he was onthe point of being quite unable to stophimself from screaming just before helost consciousness. Whilst such severepain is an occasional problem in otherpatients receiving propofol, perhaps anantecubital vein might be a wiser choicethan a hand in patients with knownRaynaud’s phenomenon. I have notfound any literature on this particularproblem.

A. GilstonLondon NW2 2EH, UK

Reference1 Stark RD, Binks SM, Dutka VN,

O’Connor KM, Arnstein MJA, GlenJB. A review of the safety andtolerance of propofol (‘Diprivan’).Postgraduate Medical Journal 1985; 61(Suppl. 3): 152–6.

An absolute contraindication tonitrous oxide

Nitrous oxide is a widely used, safe,anaesthetic without adverse effects inroutine clinical use. However, patientswho have a pre-existing vitamin B12 orfolate abnormality, whether inherited oracquired, are at particular risk of nitrousoxide toxicity [1]. This was broughtto my attention when asked to anaes-thetise a patient with the extremelyrare disorder, dihydropteridine reductase

(DHPR) deficiency. This is a rareinherited disorder of pterin metabolismand defective folate metabolism is animportant feature. It is suggested thatin patients with DHPR deficiency,accumulating dihydropterins (BH2)inhibit the enzymes important forfolate turnover, and thus render thepatient folate deplete [2].

Repeated or prolonged exposure tonitrous oxide may also cause folate dis-turbance. This agent inhibits methioninesynthase, the cofactor for which is themethylcobalamin form of vitamin B12.Nitrous oxide oxidises the cobalt in theB12 cofactor irreversibly from the mono-valent to the bivalent form, so that it canno longer function as a methyl carrier inthe transmethylation reaction.

Inactivation of methionine synthasecauses depletion of the two products ofthe reaction: methionine and tetra-hydrofolate.(a) Methionine is important as a methylgroup donor for a large number ofmethylation reactions including thoseinvolved in myelination. The effect ofnitrous oxide on methionine productionmay result in defective myelination andsubacute combined degeneration of thecord [1].(b) The effect on folate metabolismincludes trapping of reduced folatessuch as 5-methyl tetrahydrofolate, lossof folate in urine and a reduction intissue folate levels [3]. The consequencesinclude a decrease in thymidine synth-esis, an essential base in DNA, as theobligatory carbon donor for this reac-tion is 5,10 methylene tetrahydrofolatewhich is depleted. Interference withDNA synthesis is responsible for mega-loblastic changes and fetotoxicity attri-butable to nitrous oxide [4].

Nunn’s review of the interactionbetween nitrous oxide and vitamin B12

states that interference with thymidinesynthesis is to be expected in man after12 h of exposure to nitrous oxide, but mayappear within 2 h or less [1]. It appears thatthere is considerable individual variationand that critically ill patients may be moresusceptible. Therefore, any patient withimpaired turnover of methylfolate may beat increased risk when exposed to nitrousoxide, particularly if it is prolonged orrepeated at short intervals.

DHPR deficiency is very rare, but thecase highlights the need for cautionin other patients too. These wouldinclude those with rare inheriteddisorders of vitamin B12 or folatemetabolism, patients deficient in folateor vitamin B12 and patients taking anti-folate medication such as methotrexate[5]. Heightened awareness amongstanaesthetists of the interaction of nitrousoxide, vitamin B12 and folate meta-bolism and the selection of a nitrous-oxide-free technique in at-risk patientsmay prevent a rare, but easily avoidabledeleterious outcome

S. S. WyattR. S. GillSouthampton General Hospital,Southampton SO16 6XY, UK

References1 Nunn JF. Clinical aspects of the

interaction between nitrous oxide andvitamin B12. British Journal ofAnaesthesia 1987; 59: 3–13.

2 Smith I. Disorders oftetrahydrobiopterin metabolism. In:Fernandes J, Saudubray JM, Tada K,eds. Inborn Metabolic Diseases. Berlin:Springer, 1990: 183–97.

3 Chanarin I, Deacon R, Lumb M,Perry J. Cobalamin and folate: recentdevelopments. Journal of ClinicalPathology 1992; 45: 277–83.

4 Schilling RF. Is nitrous oxide adangerous anaesthetic for vitamin B12

deficient subjects. Journal of AmericanMedical Association 1986; 255: 1605.

5 Ueland PM, Refsum H, Wesenberg F,Kvinnisland S. Methotrexate therapyand nitrous oxide anaesthesia. NewEngland Journal of Medicine 1986; 314:1514.

Another cracking idea

I have been following with interest therecent correspondence regarding injuriesfrom propofol ampoules. I have sufferedseveral such injuries although none asserious as that of Dr Ali (Anaesthesia1997; 52: 1020). Following observationof the ampoule opening device suppliedby Zeneca I believe I have the answer tothe problem.



If the ampoule is held, as in Fig. 1,with the thumb levering against thebulge of the ampoule top then a sharpspike is almost invariably left on theampoule. If, however, the ampoule isheld as in Fig. 2, with the tip of thethumb against the constriction, then thetop will detach cleanly. This method hasthe advantage over that of Dr Smith(Anaesthesia, 1998; 53: 830) in that con-

trol is retained over the ampoule top andover the method recommended byZeneca in that the ampoule is openedaway from the user

I have used this method for approxi-mately 11 months without producing aspike or suffering injury.

W. J. MorrisonSouth Cleveland Hospital,Middlesborough TS4 3BW, UK

Humouring the patient

Every anaesthetist has his or her ownway of reassuring the patient beforesurgery. I am convinced, however, thathumour is an essential component ofthis vital professional duty, especiallyfor female patients. ‘When a manmakes her laugh, a woman feels pro-tected’ [1]. It would be interesting tohear of other colleagues’ views. I haveused the same approach to all patients formany years, whether it is with a high-risk patient before cardiac surgery, at oneextreme, or before examination undergeneral anaesthesia in a fit young personat the other. I also use it between theextremes of childhood and advancedold age. I tell the patient, or the parentsof a toddler, ‘There are three thingsyou (your child) mustn’t do today afterthe operation/procedure. Firstly, youmustn’t cook, secondly you mustn’tride a bicycle and thirdly you mustn’tdrink any whiskey! However, you maydance if you wish!’ This very rarely failsto bring a smile and very often even afrightened patient laughs, though withsome foreign patients the interpreter,family or professional, has the firstlaugh. Even a toddler is often comfortedby his/her parents’ laughter and embrace.I also warn patients that boredom aftermajor surgery is a sign of recovery, ‘sickpeople aren’t bored!’

A. GilstonLondon NW2 2EH, UK

Reference1 Ugo Bezzi. ‘Goat Island’. Cited by

Tripp RT, in The InternationalThesaurus of Quotations. PenguinBooks, 1976: 1055.

A slap on the back

A 52-year-old man was admitted toour intensive care unit for postoperativecare following an oesophagogastrectomy.Unfortunately he developed multi-organfailure requiring artificial ventilation,inotrope support and haemofiltration.By the seventh postoperative day, hisrespiratory function had deterioratedto the extent that prone positioningwas required to maintain oxygenation.Whilst he was prone an episode ofpulseless ventricular tachycardia was seento occur. As staff prepared for electricalcardioversion and return to the supineposition, a firm blow was deliveredbetween the shoulder blades. Sinusrhythm resumed immediately, togetherwith an arterial pulse.

This case illustrates that a dorsal blowwas effective in circumstances where aprecordial thump was indicated, butwould have been impossible to give. A‘postcordial’ thump should therefore beconsidered when cardiac arrest occurs inthe prone position

E. W. MooreM. W. DaviesRoyal Liverpool UniversityHospitals,Liverpool L7 8XP, UK

Prolonged pharyngealobstruction after the Heimlichmanoeuvre

It is well recognised that young children,the elderly and the mentally handicappedmay inhale or ingest a variety of foreignobjects, either deliberately or accidentally,resulting in obstructive syndromes whichmay present a diagnostic challenge to theclinician [1]. This is principally becausethese patients cannot communicate theirsymptoms to their carers. We present acase of a 28-year-old mentally handi-capped male who had persistent dyspha-gia after an earlier episode of choking,which was apparently relieved by theHeimlich manoeuvre

The patient presented with a 10-weekhistory of progressive dysphagia, regur-gitation of foodstuffs, 15 kg weight lossand drooling of saliva. He was thoughtto have serious gastrointestinal pathology



Figure 2

Figure 1

and elective oesophagogastroscopy wasarranged to investigate his symptoms.After pre-oxygenation with 100%oxygen by facemask, a rapid sequenceinduction of anaesthesia was performedusing intravenous thiopentone 500 mg,suxamethonium 100 mg and continuousapplication of cricoid pressure. Whilepreparing to intubate the trachea, acircular plastic object (40 mm diameter)was immediately visualised in the upperpharynx. It was easily removed witha Magill forceps and the airway wassecured with a tracheal tube. Oesophago-scopy proceeded uneventfully with nofurther abnormal findings.

The foreign body was a flat, circulardisc 40 mm diameter, a children’s toyknown as a ‘TazoTM’ which wasincluded as a promotional gift in apacket of potato crisps. The patienthad eaten it, being unable to dis-tinguish it from the food product. Sub-sequently, his carers recalled an episodeof choking whilst eating crisps 10 weekspreviously. A Heimlich manoeuvre wasperformed then which appeared torelieve his airway obstruction, althoughno foreign body or food bolus wasidentified.

The Heimlich manoeuvre [2] isaccepted as the best method of relievingacute upper airway obstruction by aforeign body. It is based on the principlethat sudden elevation of the diaphragmcompresses the lungs within the ribcage,increases pressure in the tracheobron-chial tree and thus forces the foreignbody out of the airway. In this case, itwas successful in relieving airwayobstruction, but the foreign body wasapparently dislodged into the pharynxwhere it remained, causing his symp-toms. Our patient did not suffer any life-threatening complications but deathshave been reported in mentally handi-capped patients as a result of PICA [3],and aspiration pneumonia [4], followingingestion of foreign bodies into theupper oesophagus

While the Heimlich manoeuvre maybe lifesaving in acute airway obstruction,failure to identify the offending foreignbody or food bolus at the time shouldgive rise to a high index of suspicion ofdisplacement to the pharyngo-oesopha-gus or lower airway. Symptoms such as

dysphagia, regurgitation and drooling ofsaliva with accompanying weight loss,or wheeze and unresolved lowerrespiratory tract infection mandateearly endoscopic investigation. Vigilancefor such symptoms is especially requiredby those with responsibility for patientswith communication difficulties. Finally,it is incumbent upon manufacturers offood products and snacks to alert respon-sible carers to the presence of extraneousobjects or toys that may be includedwith their products as part of a promo-tional exercise.

S. AndersonD. BuggyLeicester University GeneralHospital,Leicester LE5 4PW, UK

References1 Dallal HJ, Odun J, Ahluwalia NK.

Covert dysphagia in the mentallyhandicapped: two case reports and areview of published literature.Dysphagia 1996; 11: 194–7.

2 Heimlich HJ. A life saving manoeuvreto prevent food choking. Journal of theAmerican Medical Association 1975; 234:398–9.

3 McLoughlin IJ. PICA as a cause ofdeath in three mentally handicappedmen. British Journal of Psychiatry 1988;152: 842–5.

4 Mittleman M, Perek J, Kolkov Z,Lewinski U, Djaldetti M. Fatalaspiration pneumonia caused byan oesophageal foreign body. Annals ofEmergency Medicine 1985; 14: 365–7.

A gastronomic airwayassessment

Since airway assessment is such an inte-gral part of anaesthetic training, I thoughtyou may be interested in this simple aidememoire.

POTTED SPAMProtrusion at rest – i.e. degree of over-bite. A significant degree, i.e. under-development of the mandible, suggeststhere may be difficulty with intubation.Opening – i.e. mouth opening. Shouldbe greater than 4 cm. (The trainee can

measure their finger breadth – usually1–2 cm – to avoid having to carry a tapemeasure about.)Thyromental distance. Less than 6 cmfrom the thyroid cartilage to the mand-ible when the neck is extended suggeststhere may be difficulty intubating.Temperomandibular joints – affected insome forms of arthritis.Extension – i.e. neck extension. Shouldbe greater than 308.Dentition – False? Prominent? Caps/crowns?

Size – e.g. is the patient 100 kg?Protrusion on attempting to push thelower incisors out beneath the upperones – inability to push the mandibleforward from under the maxilla suggeststhere may be difficulty intubating.Should be greater than 2 mm protrusionpossible.Appearance. Does the patient have ashort fat neck? A jaw like a Neanderthal?A mouth like a keyhole?Mallampati – this can be 3 or 4 even inthe face of good mouth opening

The system does not prioritise, but atleast allows all points to be remembered.Apologies also to vegetarians or thosewith sophisticated taste buds

L. SanaiWestern Infirmary,Glasgow G12 9JA, UK

Music in theatre

The trouble with music in the operatingtheatre and anaesthetists (Anaesthesia1998; 53: 1137) is rhythm. This inevit-ably comes into conflict with rhythmicsignals from our monitoring equipmentunless it is so quiet as to be nonintrusive.Our nature is to suppress awareness ofregular stimuli but to respond immedi-ately to subtle variations in ventilatorsounds, ECG rate or the normal expira-tory valve noise if these are notobscured. Much of the music today isstrongly rhythmic or vocal and this actsmore-or-less like an aural fog, added totelephone calls, personal pagers, etc. Thepossibility of nonrhythmical music wasnot mentioned in a previous laboratory-based study [1]. However, advanced elec-tronic monitoring does allow warning



thresholds to be set and the anaesthetistis now less dependent on direct observa-tion, whether auditory or visual. It hasyet to be ascertained whether thisimproves safety [2].

M. R. NottRoyal West Sussex Hospital,Chichester PO19 4SE, UK

References1 Hawkesworth CRE, Sivalingam P,

Asbury AJ. The effect of music onanaesthetists’ psychomotor perform-ance. Anaesthesia 1998; 53: 192–200.

2 Adejumo SWA. Monitoring yoursoftware. Royal College of AnaesthetistsNewsletter 1998; 43: 31.

Erratum

Caudal epidurals: the ‘whoosh test’In the reply of Dr Buchan to an item of correspondence from Dr Atherton (Anaesthesia 1998; 53: 927–8), there was anerror in the section giving details of the fuller analysis of the diagnostic test results. In the beginning of the sectionsentitled ‘For clinical impression’ and ‘For whoosh test’, the words ‘correct’ and ‘incorrect’ in the first two sections ofthe first sentence of each have been transposed.

The beginning of the two sections should read:For clinical impression: +ve predictive (post-test likelihood of correct needle placement) = 93%; –ve predictive value

A (post-test likelihood of incorrect needle placement) = 78%; . . .For whoosh test: +ve predictive (post-test likelihood of correct needle placement) = 96%; –ve predictive value A (post-

test likelihood of incorrect needle placement) = 80%; . . .


Anaesthesia, 1999, 54, pages 297–310................................................................................................................................................................................................................................................

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