A method of assessing operative and post-operative blood loss

A METHOD OF A S S E S S I N G OPERATIVE AND P O S T - O P E R A T I V E BLOOD LOSS

JAMES MclvoR, M.B., Ch.B., F.D.S.R.C.S. Eastman Dental Hospital, London 1

INTRODUCTION

THERE have been many assessments made of blood loss in surgery. Since 1955, seven papers dealing with blood loss in oral surgery have been published. The methods have varied--most popular have been the gravimetric and volumetric methods (Johnson, 1956; Connors, 1959; Rhymes & Williams, 1964). Gores et al. (I955), Berdon (1965) and Watts (1965) used a colorimetric method. Spengos (1963) approached the problem differently, and instead of collecting blood from the operative field as other investigators had, he measured the difference between pre- and post-operative plasma volumes. Rossi (1957) did not describe his method. Post-operative blood loss has been measured only once (Rhymes & Williams, 1964).

POSSIBLE METHODS

Most surgeons make some estimation of blood loss from the appearance of the operative field and the number of swabs used, etc. However, Thornton (1963) has stated that it is difficult for most observers to distinguish between a blood loss of 500 ml. and one of 15oo ml., and Bonica and Lyter (1951) in summarising the work of 17 other investigators concluded that the surgeon's estimate is always less than the actual loss.

L Grav imet r i c . (a) Pa t i en t Weighing. A special weighing table can be used to measure the pre- and post-operative weight of the patient. Allowance must be made for drains, dressings, infusions and evaporation. From the patient's loss of weight (I gram equals I ml. of blood) blood loss is calculated. It is difficult to measure small losses accurately with this technique, but it is considered by Thornton (1963) to be a useful check on other methods.

(b) Swab Weighing. Blood loss is confined to previously weighed swabs which are re-weighed immediately upon being discarded from the operative field. From their increase in weight blood loss is calculated.

Sources of error are fluids other than blood, e.g. saliva, and blood lost on instruments, gloves, drapes, gowns and by evaporation.

2. Volumetr ic . The volume of any fluid to be introduced into the operative field is measured pre-operatively and any excess fluid in the aspirator jar after the operation is assumed to be blood. Sources of error are aspirated fluids other than blood.

3. Color imetr ic . This technique, first described by Pilcher and Scheard in 1937, may be applied to blood-stained swabs, drapes, gowns, gloves and to blood collected by aspiration.

1 Present address: Depar tment of X-ray Diagnosis, Westminster Hospital, London, S.W.I.

A I

2 B R I T I S H JOURNAL OF ORAL SURGERY

Blood-stained swabs, etc., are washed two or three times and the washing fluid collected, together with the contents of the aspirator jar, in a container of almost unlimited size; many investigators have used containers with a volume of 4o litres. The washing fluid and fluid in the aspirator jar should contain an agent which will alter haemoglobin to a more permanent pigment such as methaemo- globin or cyanomethaemaglobin (when an immediate result is not required, swabs, etc., may be soaked for 24 hours as an alternative to washing). By measuring the haemoglobin concentration of the fluid in the container on a colorimeter, and its total Volume, its haemoglobin content can be calculated; and if the patient's pre-operative haemoglobin is known, the volume of patient's blood in the container can be calculated. The whole process can be automated to give a continuous reading of blood loss during operation, and an instrument which does this is now available (Rustad, 1963). Sources of error are variations in the patient's haemoglobin during operation, and failure to collect all blood lost from the operative field.

4. Labe l led Red Cells (Rankin et al., 1962). A sample of patient's blood is incubated with Cr ~1, after which the red cells are washed, measured for gamma radiation on a scintillation counter, and returned to the cardiovascular system. The concentration of Cr 51 in the peripheral blood is measured pre-operatively; and at the end of the operation all blood-stained swabs, drapes, etc., are measured gamma radiation and the volume of blood lost is calculated.

5. By Blood Volume Measu remen t . The difference between pre- and post-operative blood volumes should give a measure of operational haemorrhage. The several methods available are based on the same principle--a known quantity of dye or radio-active tracer is injected into a vein; after a delay of a few minutes to allow it to be evenly distributed throughout the cardiovascular fluid compartment, a sample of blood is withdrawn, and from the dilution of the injected substance, blood volume is calculated.

(a) Rad io -ac t ive Iodine. An intravenous injection of human albumin labelled with 1 TM or 113~ is distributed throughout the cardiovascular system within 15 minutes. When this time has elapsed a sample of venous blood is withdrawn and the plasma volume calculated. Blood volume is calculated from the haematocrit reading of a sample of venous blood.

1 TM has a shorter half-life than I TM and is therefore more suitable for quickly repeated blood volume estimations, but it requires more expensive procedures and apparatus.

An instrument with a built-in computer, the Volumetron (William & Fine, 1961) is now available which enables blood volumes to be measured simply and quickly using I TM labelled albumin--the answer being read off in litres a few minutes after insertion of the appropriate blood samples. Sources of error are the different haematocrit readings obtained on samples of blood drawn from different parts of the cardiovascular system, and the leaking of albumin from the cardiovascular fluid compartment.

(b) Rad io -ac t ive C h r o n i u m (Mollison & VeaU, 1955). A sample of patient's blood or compatible blood from a donor is labelled with Cr 51 as already described, and returned to the cardiovascular system. After a few minutes a sample of venous blood is withdrawn and the patient's total red cell volume calculated. From the haematocrit reading, total blood volume is calculated. This is an

METHOD OF ASSESSING OPERATIVE BLOOD LOSS 3

accurate method of measuring blood volume and therefore operative blood loss, but the technique is elaborate and requires expensive equipment.

(c) Radio-act ive Phosphorus (Reeve & Veall, 1949). As previously described for Cr 51, red cells may be labelled with p3~, measured for beta radiation and injected into the cardiovascular system. Blood volume is calculated from red cell volume. Owing to the short biological half-life of p3~, repeated estimations of blood volume are possible without having to increase the dose of p32. As a technique for measuring operative blood loss, it has the same advantage and disadvantages as Cr ~1.

6. O the r Techniques . Techniques for assessing operative blood loss which depend upon electrolyte conductivity (Le Veen & Rubricus, 1958) and serum specific gravity (Phillips et al., 1943) have been described, but are not commonly used. Plasma volume may be measured by labelling albumin with dyes such as Vital Red or Evans Blue instead of radio-active Iodine, but these methods have little application to the measurement of operative blood loss. Red cells from a compatible donor which have been tagged with Fe 55 or Fe ~9 can be used to measure blood volume, but their use has been largely abandoned as it involves the donor in a relatively high dose of radiation (Murray & Ports, 196o).

METHOD USED

The 45 patients studied were in-patients to whom a general anaesthetic was administered, and the method used was colorimetric.

(I) Between anaesthetising the patient and commencing the operation, 2 ml. of blood was withdrawn from an ante-cubital vein. No tourniquet was used. Three separate haemoglobin estimations were made on a portable colorimeter (E.E.L.) and the average taken. I f any two of the readings differed by more than 3 per cent., three more estimations were made and averaged.

(2) All blood lost during operation was either aspirated or confined to instruments, gloves and standard size swabs. After operation, the blood-stained instruments and gloves of the operators were wiped clean with a moistened swab. The aspirator was washed through with o-o 4 per cent. ammonium hydroxide (to oxidise haemoglobin to oxyhaemaglobin) until the fluid entering the jar was quite clear. All blood-stained swabs and the throat pack were placed in a container (usually a IOOO ml. beaker), the contents of the aspirator jar added, and the volume made up to about iooo ml. with ammonia. This was allowed to stand for between 20 and 30 hours when the oxyhaemoglobin concentration and volume of fluid were measured. In measuring the volume, allowance was made for the volume of swabs and other inclusions.

Oxyhaemoglobin concentration was measured on an E.E.L. colorimeter. It was often necessary to dilute this fluid still further with ammonia, so that it would give a reading when placed in the colorimeter, and this dilution was recorded. By applying the formula of Pilcher and Scheard (I937) , the volume of patients' blood in the container was calculated:

Vol. of solution in container ×E.E.L. Reading of solution

200 Blood loss =

E.E.L. Reading of venous blood diluted 200 times

4 BRITISH JOURNAL OF ORAL SURGERY

(3) The post-operative loss was measured by placing all swabs stained with blood during the post-operative 2o hours in approximately 5o0 ml. of ammonia. This was allowed to stand for between 2o and 3 o hours when volume and oxyhaemoglobin concentration were measured and the blood volume calculated as already described.

(4) Thirty-six to forty-eight hours post-operatively, a second venepuncture was performed as beforer and the patient's haemoglobin measured again. The results obtained from each case studied were therefore:

Pre-operative haemoglobin; Post-operative haemoglobin; Blood loss during operation; Blood loss post-operatively.

RESULTS

Of the 45 patients in the study, 30 had third molars removed, 5 had an unerupted canine or premolar removed and IO had multiple extractions performed. All were in-patients of the Oral Surgery Department of the Eastman Dental Hospital and received a general anaesthetic. There were six possible operators, in most cases two operators worked together and shared the operating.

The results were investigated according to age, sex and blood pressure, and in the case of female patients, menstrual history. Any special measures taken during operation to control haemorrhage were noted, as was the duration of operation and the use of local anaesthetic agents. The normal routine of operation was not altered.

400

300

Key

Blood Loss

in ml s.

]Post -Operat ive Blood Loss

Dperat ive Blood Loss

I - -

Z00

I00

50

Number of ii

Mo la r s I Z

E x t r a c t e d ,,,

FIG. I Histogram of blood loss of 3o patients, 15 male and 15 female, during and

following removal of wisdom teeth.

METHOD OF A S S E S S I N G OPERATIVE BLOOD LOSS 5

I. Th i rd Molars . Figure I is a histogram of the operative and post-operative blood loss of 3 ° patients, 15 male and 15 female, who had wisdom teeth removed. The cases are grouped according to the number of teeth removed and arranged within each group in order of the volume of blood lost.

The average blood loss during operation was 72 ml. and the average time of operation 28 minutes. There was no simple relationship between blood loss and age, sex, blood pressure, type of local anaesthetic agent (which was used in every case), duration of operation or menstrual history. Where operative blood loss exceeded IOO ml., as it did in six cases, haemorrhage seemed excessive at operation and measures were taken to control it. These measures varied between the application of pressure and the insertion of a Whitehead's varnish pack, depending upon the wish of the operator and the nature of the haemorrhage. In five cases, haemorrhage was from the bony socket of a recently extracted lower third molar, and in one case it was from the soft-tissue incision. In 6 of the 24 cases in which blood loss was less than IOO ml. operational haemorrhage seemed excessive and steps were taken to control it.

The average post-operative blood loss was 15 ml. In the case where it was measured as 260 ml. haemostasis was satisfactory when the patient left theatre, but he bled intermittently during the next few hours and after four hours quite profusely. At this stage a Whitehead's varnish pack was placed in the socket of the extracted lower right third molar and the haemorrhage stopped almost immediately.

The average fall in haemoglobin was 2-2 per cent. and the greatest 9 per cent. occurred in a patient who was menstruating. There were two patients operated upon while menstruating and both sustained relatively large falls in haemoglobi~

2. U n e r u p t e d Canines and P remola r s . Figure 2 is a histogram of the operative and post-operative blood loss of five patients who had an unerupted

Key

Blood Loss

in mls.

200

10C

5C

Post-Operative Blood Loss

~ pe rative Blood Loss

FIG. 2

Histogram of blood loss during and following removal of buried canine or premolar tooth.


canine or premolar removed. The average blood loss was 26 ml. during operation and 5 ml. post-operatively. The average fall in haemoglobin was o.4 per cent.

3. Mul t ip le Extract ions . Figure 3 is a histogram of the operative and post-operative blood loss in IO patients who had multiple extractions performed. The cases are arranged in order of the number of teeth extracted.

The average blood loss was x25 ml. during operation and 15 ml. post- operatively for an average of 15 teeth extracted. The patient who sustained the greatest blood loss, 36o ml., had both unerupted lower third molars removed in addition to I5 normally erupted teeth. The average fall in haemoglobin was 3 per cent., the greatest fall, 8 per cent., occurred in a patient who was menstruating.

400

Pos t -Opera t ive Blood Loss

Operat ive Blood Loss

300

Blood Loss in mls.

200

1.00

50

Fie. 3 Histogram of blood loss during and following multiple extractions.

DISCUSSION

The relative accuracy of the various methods of estimating blood loss are difficult to assess as different methods give different results even when applied simultaneously to the same patient (Caceres & Whittenbury, I959; Thornton et aL, I963). Generally, methods depending upon the difference between pre- and post-operative blood volumes give higher losses than methods depending upon the collection of blood from the operative field. To explain these findings, Thornton (I963) suggested that not all the blood which escapes from the cardiovascular system at operation is lost from the body, but that some remains 'concealed' in the tissues at the site of operation and is not measured as blood

METHOD OF ASSESSING OPERATIVE BLOOD LOSS 7

lOSS by methods depending upon the collection of blood from the operative field. The method used in this series measured the volume of blood collected from

the operative field, and to test its accuracy, eight estimations were made on known volumes of fresh venous blood. In two experiments, a known volume of freshly drawn venous blood was aspirated from a beaker, half the volume before it clotted and half afterwards, and the aspirator washed through as described. In two experiments, a known volume of fresh venous blood was poured straight on to swabs where it clotted. The swabs then lay drying in an open beaker for I5 hours before being soaked for 2 4 hours in o.o 4 per cent. ammonium hydroxide when the blood contained in them measured as already described. Figure 4 is a graph

M e a s u r e d Volume of Blood in rnls. (Logarithmic

Scale)

60

40

zo

10

5

z

Z 5 i0 z0 40 60 Known Volume. of Blood in mls. (Logari thmic Scale)

FIG. 4 Graph of experimental results setting known blood volume against measured volume.

of these experimental results in which the known volume of blood is set against the measured volume. Aspiration resulted in a 'loss' of up to 2 ml. The other estimations were all within 2 per cent. of the known volume, which is similar to the experimental results of Pilcher and Scheard (I937).

Collection of blood during operation presented no special difficulty, but its collection during the post-operative period was less reliable, as some patients persisted in swallowing, particularly after multiple extractions. One patient vomited post-operatively and the vomitus contained fresh blood.

Should the patient's haemoglobin vary during operation, the method used in this study becomes less accurate, in proportion to the variation. Daily variations in haemoglobin which can be up to 8 per cent. (Haldane) (Wadsworth, I955) did not affect the results of this investigation, as haemoglobin concentration was estimated on a sample of blood taken a few minutes prior to the start of operation.


Variation during operation is unlikely unless the operation lasts several hours, by which time physiological haemodilation will have started, or unless the patient receives an intravenous infusion. The effect of an intravenous infusion would depend upon its haemoglobin concentration in relation to the patient's haemoglobin, the rate of infusion, and the rate at which the infused fluid diffused out of the cardiovascular fluid compartment so that its effect would bc difficult to predict; but any variations could bc taken into account, to some extent, by repeated haemoglobin cstirnations during operation. These circumstances did not arise in any of the cases studied, but could possibly occur in major oral surgery.

It was not expected that a relationship between haemoglobin fall and blood loss would emerge in individual cases, as most of the patients studied lost relatively small volumes of blood (Wadsworth, I955). But it was expected that the average fall in haemoglobin might be related to the average blood loss. If the three patients who were menstruating at the time of operation are left out, then the average blood loss of the remaining 42 cases was 96 ml., 8I ml. during operation and I5 ml. post-operatively. This group sustained an average fall in haemoglobin of 1.8 per cent. from an average pre-opcrative level of 9o'9 per cent. (Haldane), being an average fall of 2 per cent. of the pre-operative level. Theoretically, physiological haemodilution in the average individual with a blood volume of 5 litres should result in a i per cent. fall in haemoglobin for each 50 millilitres of blood lost (Keele & Nell, I965). This group sustained an average fall in haemoglobin of 2 per cent. for an average blood loss of 96 ml., so theoretically there is a reasonable correlation between average blood loss and average haemoglobin fall.

The three patients who were menstruating suffered relatively large falls in haemoglobin (average 7'3 per cent.) for relatively low blood losses (average 36 ml.). It is difficult to explain this on the basis of haemorrhage alone, even if it is assumed that menstrual blood loss was heavy in these cases.

Comparison of the results obtained in this study with those of other investiga- tions is possible in only a few cases. It would seem that the patients in this series, who had third molars removed, lost rather less blood during operation than the cases studied by Rossi (I957) and by Watts (r965) and that the patients who had multiple extractions performed suffered haemorrhages similar to those recorded by Gores et al. (i955) and Rhymes and Williams (r964) but substantially less than the losses recorded by other investigators. More interesting perhaps was the absence of any operational haemorrhages in excess of 34o ml. which is much less than the figures quoted by other investigators. Post-operative losses following multiple extractions were less than half the losses measured by Rhymes and Williams (I964).

Determination of all the factors involved in blood loss would require a larger series, but afew did emerge. (I) Blood loss during the removalof third molars was less than Ioo ml. unless the incision divided a submucosal artery or unless the inferior dental canal was damaged, and this was always apparent at operation. (2) Blood loss during multiple extractions was partly related to the number of teeth extracted and to the duration of operation. (3) Post-operative blood loss, although normally small, could be considerable.

METHOD OF A S S E S S I N G OPERATIVE BLOOD LOSS 9

CONCLUSIONS

Before speculating upon the possible ill-effects of haemorrhage in the cases sti)died, which ranged from 13 ml. to 360 ml., it might be mentioned that the average woman loses 45 ° ml. of blood each year from menstruation (Jacobs & Butler, 1965) and that blood donors lose 42o ml. of blood at a time and are usually fit to travel home unaccompanied an hour or so later. As all the patients in this series had a pre-operative haemoglobin level in excess of 75 per cent. (Haldane), it would seem unlikely that any one of them suffered seriously from haemorrhage, either from the immediate danger of oligaemic shock or from the possibility of a prolonged period of anemia following operation.

SUMMARY

The techniques available for measuring blood loss are described briefly and the colorimetric method used in this study is described in detail. Operative and post-operative blood losses for the 45 patients studied are shown on three histo- grams. 'Concealed' haemorrhage, the accuracy of the method used and the relationship between blood loss and haemoglobin fall are discussed: the effect of menstruation is noted. The results are compared with those of previous investigators and mention is made of the factors which seemed to affect haemorrhage. Finally, it is concluded that the blood losses recorded were relatively trivial.

A C K N O W L E D G E M E N T S

I am grateful to Professor H. C. Killey, Professor of Oral Surgery, Mr. N. L. Rowe, Consultant Oral Surgeon, and Mr. L. W. Kay, Senior Lecturer in Oral Surgery, at the Eastman Dental Hospital for their help and encouragement during the gathering of results and in the preparation of this paper; and to Mr. G. C. Blake, Senior Lecturer in Dental Bacteriology at the Eastman Dental Hospital, for his help and for access to laboratory facilities.

REFERENCES

BERDON, J. K. (1965). J. Periodont. 36, lO2. BONICA, J. J. & LYTER, C. S. S. (1951). Am. J. Surg. 81, 496. CACERES, E. & WHITTEMBURY, G. (1959). Surgery, 45, 681. CONNORS, J. J. (1959)- Ann. Dent. I8, 74. GORES, R. J., ROYER, R. Q. & MANN, F. (1955). ft. oral Surg. I3, 299. JACOBS, A. & BUTLER, E. B. (1965). Lancet, 2, 4o7. JOHNSON, R. L. (1956). ft. dent. Res. 35, 175. KEELE, C. A. & NEIL, E. (1965). Applied Physiology, Samson Wright, i l th ed., p. 136.

London: Oxford University Press. LE VEEN, H. H. & RUBRICUS, J. L. (1958). Surgery Gynec. Obstet. lO6, 368. MOLLISON, P. L. & VEALL, N. (1955). Br. J. Haemat. 1, 62. MURRAY, B. R. P. & POTTS, M. W. (196o). Guy's Hosp. Gaz. 74, 12o. PHILLIPS, R. A., Van SLYKE, D. D., DOLE, V. P., EMERSON, K., Jr., HAMILTON, P. B. &

ARCHIBALD, R. M. (1943). Bull. U.S. Army med. Dep. 7I, 66. PILCHER, F. & SCHEARD, C. (1937)- Proc. Staff Meet. Mayo Clin. I2, 209. RANKIN, G. L. S., VEALL, 1NI., HUNTSMAN, R. G. & LIDDELL, J. (1962). Lancet, 1, 567. REEVE, E. g. & VEALL, lxl. (1949). J. Physiol., Lond. lO8, 12. RHYMES, R. & WILLIAMS, C. (1964). J. Am. dent. Ass. 69, 346.

IO BRITISH JOURNAL OF ORAL SURGERY

RossI, D. J. (1957). Dent. Clin. N. Am. 349. RUSTAD, M. (1963). Lancet, I, 13o4. SPENGOS, M. N. (1963). Oral Surg. 16, 276. THORNTON, J. A. (I963). Ann. R. Coll. Surg. 33, 164. THORNTON, J. A., SAYNOR, R., SCHROEDER, H. G., TAYLOR, D. G. & VEREL, B. (1963).

Br. J. Anaesth. 35, 91. WADSWORTH, G. R. (1955). ft. Physiol., Lond. 129, 583. WATTS, K. D. (1965). Spring Meeting, British Association of Oral Surgeons. WILLIAMS, J. A. & FINE, J. (1961). New Engl. ~. Ailed. 264, 84z.

T H I R D I N T E R N A T I O N A L C O N F E R E N C E O N O R A L S U R G E R Y

THE Third International Conference on Oral Surgery--5oth Annual Meeting of the American Society of Oral Surgeons, will be held October 8-I2, I968, in New York City, New York, U.S.A.

Scientific Programme: Individuals interested in participating in the scientific sessions are invited to write directly to Dr. William Rakower, 57 W. 57th Street, New York, New York IOO19, U.S.A.

Research Programme : Individuals interested in presenting a research paper at the conference are invited to submit the title and synopsis of their presentation directly tO Dr. Walter C. Guralnick, i io Francis Street, Boston, Massachusetts oz2r 5, U.S.A.

Motion Picture Programme: Individuals having motion pictures in the field of oral surgery and wishing to present such at the Third International Conference on Oral Surgery are invited to submit a synopsis of the film's content along with the length of the presentation to Dr. Roger Gerry, Mt. Sinai Hospital Services, City Hospital Center, 79-Ol Broadway, Elmhurst, New York, I I373, U.S.A.

A method of assessing operative and post-operative blood loss

Documents

Transcript of A method of assessing operative and post-operative blood loss