OBSTETRIC ANAESTHESIA UPDATE · Role of tranexamic acid The CRASH-2 trial showed a reduction in...

8 July 2016 No. 16

OBSTETRIC ANAESTHESIA UPDATE

Dr Ian Kiwalabye

Moderator: Dr S Reddy

School of Clinical Medicine

Discipline of Anaesthesiology and Critical Care

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CONTENT

INTRODUCTION ...................................................................................................................... 3

AIRWAY ................................................................................................................................... 3

Difficult airway algorithm in obstetrics .................................................................................... 4

Key Features ...................................................................................................................... 4

OBSTETRIC HAEMORRHAGE ............................................................................................... 6

WHO guidelines On Post-partum Hemorrhage...................................................................... 7

Oxytocin .............................................................................................................................. 10

Fibrinogen ........................................................................................................................... 11

Role of tranexamic acid ....................................................................................................... 11

Transfusion management .................................................................................................... 12

PRE-ECLAMPSIA .................................................................................................................. 13

Definition ............................................................................................................................. 13

Prevention and management............................................................................................... 14

Anti-Hypertensive agents .................................................................................................... 15

Prevention Peri-induction hypertension ............................................................................... 15

CONCLUSION ........................................................................................................................ 16

REFERENCES ....................................................................................................................... 17

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OBSTETRIC ANAESTHESIA UPDATE

INTRODUCTION

This review is looking at some of the developments that have occurred in obstetric anaesthesia over the last few years. As this is obviously such a vast topic, I have chosen to concentrate on just a few areas of interest to me. I will be discussing the new “difficult airway algorithm” in obstetrics; the WHO guidelines on the management of post-partum haemorrhage including the use of oxytocin and fibrinogen; and some of the changes that have occurred in definition and management of pre-eclampsia. AIRWAY A study performed by Samsoon et al [1] found the incidence of failed or difficult intubation in obstetric patients to be 1:280, a rate eight times that found in the general surgical patient (non pregnant). Subsequent studies confirmed these findings and found a rate of between 1:224 and 1:443 [2-5]. This difficulty with intubation in obstetric patients can be attributed to patient, anaesthesia provider and system factors. Patient Factors: Physiological changes that occur during pregnancy and labour are known to contribute to the increased incidence of difficult airway, aspiration and hypoxia thus increasing morbidity and mortality in the obstetric population. Factors that increase the technical difficulty of intubation include increased oedema and friability of the airways, weight gain and labour. All this leads to an increase in the mallampati class [6, 7], whilst a 20% reduction in the functional residual capacity, increased breast size, enlargement of the uterus and an increase in the oxygen consumption result in shorter time to hypoxia between induction and securing the airway. Anaesthesia Provider Factors: A number of studies and reviews have noted that the amount of caesarean sections under spinal anaesthesia has increased compared with general anaesthesia [3, 4, 8-10]. Since the 1980s, cesarean sections performed under general anaesthesia have declined by more than 90% and now only constitute between 2, 5 and 5 % of operative deliveries. This has been hypothesized as another factor contributing to poor management of a difficult airway, as a result of the loss of skills in airway management and reduced training opportunities for junior doctors.[11] System factors: Studies have shown that the majority of failed intubations obstetrics occur in cases done as emergencies, out of the normal working hours and involve junior doctors.[2, 9]

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Difficult airway algorithm in obstetrics In light of the above factors, the difficult airway society developed the difficult airway algorithm to be used in parturients.

[8]

Key Features

1. The first section of the algorithm addresses the importance of advance planning, preparation and ensuring optimal conditions to perform a rapid sequence induction in the obstetric patient.

Pre oxygenation- During pre-oxygenation with a face mask to consider the use of

nasal cannula with 5L/min of oxygen during airway instrumentation. Cricoid pressure- It should be reduced or removed promptly, if difficulty with

laryngoscopy is encountered or placement of a supraglottic airway.

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[8] 2. The guidelines address situation were a difficult airway is encountered and the factors to

take into consideration when deciding to wake the patient or not. Indications to continue with surgery are: Maternal compromise that is refractory to resuscitation. Acute fetal compromise that is irreversible e.g. umbilical cord prolapse[8]

The indications that are given to wake the patient are: Periglottic airway swelling. Continued airway obstruction[8].

[8]

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If the decision is made to proceed with surgery, the guidelines place emphasis on issues that should be considered: Choice of airway device- face mask vs SGA Ventilation strategy- manual vs controlled Maintenance of anaesthesia Either to maintain or release cricoid pressure Ensure the drainage of gastric contents 2. In a scenario of “can’t intubate, can’t ventilate” the surgical cricothyroidotomy is advocated

over needle cricothyroidotomy, as the latter has been associated with high failure rates and is technically difficult in obese patients.

OBSTETRIC HAEMORRHAGE Post-partum haemorrhage is defined as blood loss of 500ml or more post vaginal delivery and 1000mls or more post caesarean section. Post-partum haemorrhage is one the leading causes of maternal death in low-income countries, accounting for nearly a quarter of the deaths globally [12] .Causes of post-partum haemorrhage are: Uterine atony (most common), genital tract trauma, retained placental tissue and grand multiparity. In South Africa the “Saving Mothers” report for the 2011-2013 triennium identified obstetric haemorrhage as one of the top 3 causes of maternal death. An increase of 24.7% in maternal deaths due obstetric haemorrhage was noted in the 2011-2013 saving mothers report since the last report was released. The cases were the primary cause of death was obstetric haemorrhage, 89% of them were preventable. [13]

[13]

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WHO guidelines On Post-partum Hemorrhage In 2013 the World health organization released revised recommendations on the prevention and treatment of post-partum hemorrhage. Measures to be taken to prevent PPH are actively managing the 3rd stage of labour and administration of prophylactic uterotonics .Oxytocin is the uterotonic of choice and in situations were it is not available ergometrine or misoprostol are to be given[12]. Cord traction and uterine massage are to be avoided as measures used to prevent PPH[12]. Regarding the treatment of PPH, oxytocin is the primary uterotonic to be administered. Ergometrine or prostaglandin to be give were oxytocin is not available or bleeding is not responding to it. Isotonic crystalloids are the fluids of choice and tranexamic acid should be administered. In the scenario were conservative measures have failed to stop the bleeding, surgical intervention is required.

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[12]

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Oxytocin Oxytocin is the uterotonic of choice for the management and prevention of uterine atony, leading to a reduction of the risk of post-partum hemorrhage by 40-50%.There has been no consensus on the dose to use for the prevention of uterine atony, studies have shown that adequate uterine tone is achieved with doses as low as 3IU[14] against the practice of administering doses of 20-40IU[15, 16]. This has been driven by the need to balance avoidance of uterine atony and the side effects of oxytocin use. The National Committee for Confidential Enquiries into Maternal Deaths in South Africa issued an alert regarding the continuing high levels of maternal deaths due to obstetric hemorrhage. Problems that were identified included: Insufficient use of prophylactic doses of oxytocin, excessive intravenous boluses of oxytocin and inadequate dosages of therapeutic oxytocin for treatment of established intraoperative bleeding due to an atonic uterus. In response to this the NCCEMD released a guideline on administration of oxytocin and other uterotonics.

[16]

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A recent double blinded randomized trial comparing a “rule of threes” algorithm against a continuous infusion of oxytocin. This was done on participants that were undergoing elective cesarean section. In this study sixty women were randomized to receive either 3IU of oxytocin versus a continuous bolus of oxytocin (30 IU/500mls). The tone of the uterus was assessed at the following time intervals: 3, 6, 9 and 12 minutes. Results showed that the regular assessment of uterine tone by the attending surgeon, and subsequent treatment of any atony used far lower doses of oxytocin than the standard practice of just letting an infusion pour in[17]. Fibrinogen Concentrations of fibrinogen, von willebrand factor, factor VII, factor VIII and FIX are noted to increase during pregnancy, while activity of both protein s and fibrinolysis is reduced. These changes result in a hypercoagulable state during pregnancy. The normal level of fibrinogen during pregnancy have been found to be between 4.5-5.8g/l. Studies have not that the level of fibrinogen determines the severity of PPH [18, 19]. As part of their guidelines for the management of severe perioperative bleeding, the European society of anaesthesiology recommends monitoring of fibrinogen. Concentrations below 2g/l identifies those at risk of severe postpartum haemorrhage. Although the cause for the reduction of fibrinogen concentration are not currently known, suggested theory is that intravascular fibrin is deposited post-delivery thus leading to increased early consumption of fibrinogen. Other theories include hemodilution as a result of high intravenous administration or loss of pro heamostatic factors. The recognition of hypofibrinogenemia correlating with severe PPH and the correction of hypofibrinogenemia has been investigated. Cryoprecipitate and fibrinogen concentrates have been used to replace fibrinogen. Review articles and studies have noted that the pre-emptive use of fibrinogen concentrate resulted in decreased transfusion requirement and increased fibrinogen concentration[19]. However a multicenter, double blinded randomized control trial looked at the pre-emptive administration of fibrinogen concentrate for postpartum haemorrhage. 249 subjects were enrolled in the study. The intervention group was assigned to receive 2 g of fibrinogen and the control group a placebo. The study showed that the transfusion rates between two groups were not different.[20] Role of tranexamic acid

The CRASH-2 trial showed a reduction in mortality due to haemorrhage in adult trauma patients that were empirically given tranexamic acid[21]. The European society of Anaesthesiology and WHO both recommend the use of tranexamic acid in patients with severe PPH. The EXADELI Trial, looked at the early administration of tranexamic acid to women with PPH. The group that did receive tranexamic acid were noted to have less blood loss compared to the control group (170mls Vs 221mls)[22]. Major limitations of the trial included: absence of a placebo, blinding of study and the clinical significance of the difference of the blood lost between the two groups. There is very little evidence on the effectiveness of tranexamic acid administration in the treatment of PPH[23]. Currently the WOMAN trail is investigating the role of tranexamic acid in the management of obstetric haemorrhage. The results of this trial are pending.

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Transfusion management Studies looking at the management of transfusion in obstetric patients with post-partum haemorrhage are few. A lot of the data related to management for massive transfusion is driven from studies of trauma patients. Different strategies have been proposed. 1. In an article looking at resuscitative strategies for massive peripartum haemorrhage, the

following strategy was suggested: Avoidance of dilutional coagulopathy Red blood cells, fresh frozen plasma and platelets to be replaced in a ratio of 1:1:1. Use of appropriate cryoprecipitate and an antifibrinolytic agent.[24]

2. In an article based on 6 case studies, their massive transfusion protocol involved the replacement of blood products i.e. Red blood cells, plasma and apheretic platelets in a ratio of 6:4:1. The authors stated that this ratio is an approximation the composition of whole blood[25].

During the maintenance phase of their resuscitation, the following laboratory test: PT, PTT, Platelets and fibrinogen levels were done to guide resuscitation. Replacement of blood products occurred when Platelet levels were below 25, fibrinogen levels below 100mg/dl and 1.5 times normal values of both PT and PTT[25].

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PRE-ECLAMPSIA Definition

The American College of Obstetricians and Gynaecologists revised their criteria for the diagnosis of pre-eclampsia. Proteinuria is no longer a mandatory requirement for the diagnosis of pre-eclampsia. The new definition states that pre-eclampsia is hypertension with the following features: Pulmonary edema, impaired liver function, thrombocytopenia, renal insufficiency and cerebral or visual disturbances.[26]

[26]

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[26] Fetal growth restriction and the quantity of urinary protein have been removed as criteria of diagnosis of severe pre-eclampsia They further classified hypertension during pregnancy into four classifications Pre-eclampsia-eclampsia Chronic hypertension of any cause Chronic hypertension with superimposed preeclampsia Gestational hypertension Prevention and management Prevention 1. Administer calcium. 2. Administer low dose aspirin. Management 1. Timely diagnosis. 2. Non-steroidal anti-inflammatory drugs to be avoided. 3. Mild Gestational hypertension, Pre-eclampsia with BP< 160mm Hg + Diastolic < 110mm

Hg. 37 weeks or less – Expectant Management and monitoring 37 weeks or more- Delivery of fetus Anti-hypertensives not to be administered Magnesium sulphate not to be administered

4. Severe Pre-eclampsia, BP > 160 mm Hg + Diastolic > 110 mm Hg 34 weeks or more- Fetus to be delivered. Less than 34 weeks - Monitor if fetus and mother are stable (High resource unit).

- Administer corticosteroids (48hrs). Start Anti-hypertensives. Administer Magnesium sulphate. Neuraxial anaesthesia permitted (Provided there are no contraindications).

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Anti-Hypertensive agents In a Cochrane review evaluating the optimal anti-hypertensive to use in parturients. 14 anti-hypertensive drugs were looked at, 35 trials were collected and reviewed. The effects of the drugs on both maternal and fetal morbidity and mortality were assessed. The review found that with the three most commonly used agents i.e. hydralazine, labetalol and nifedipine there was no significant differential effects. The review recommended that the following drugs be avoided: Nimodipine High dose diazoxide- Associated with severe hypotension. Ketanserin- Associated with persistent hypertension.

They demonstrated that there was no optimal anti-hypertensive to use in parturients with hypertension.[27] Prevention Peri-induction hypertension A review article looked at drugs used to blunt the intubation response in pre-eclamptic patients. The groups of drugs that were looked at were: Beta adrenergic antagonists, direct vasodilators, opioids, Lignocaine, calcium channel blockers, Magnesium sulphate and the induction agents.[28]

[28]

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The review article noted that there is little evidence of the optimal drug to be used to blunt that intubation response in parturients undergoing a rapid sequence induction. The following drugs were recommended for use to blunt the pressor response: Esmolol, Nitroglycerine, labetalol, and remifentanil. They were found to have favorable pharmacological profiles, and the effects of the drugs in neonates was short. The following drugs were to be avoided due potential for serious side effects to both the fetus and mother. The drugs are hydralazine, magnesium and calcium channel blockers. [28]

CONCLUSION There is currently an enormous amount of work and research going on in the areas I’ve mentioned in my talk. My talk was meant to highlight some of the developments in these aspects that may impact our current practice.

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REFERENCES 1. Samsoon GL, Young JR: Difficult tracheal intubation: a retrospective study. Anaesthesia

1987, 42(5):487-490. 2. Quinn AC, Milne D, Columb M, Gorton H, Knight M: Failed tracheal intubation in obstetric

anaesthesia: 2 yr national case-control study in the UK. Br J Anaesth 2013, 110(1):74-80. 3. Rahman K, Jenkins J: Failed tracheal intubation in obstetrics: no more frequent but still

managed badly. Anaesthesia 2005, 60(2):168-171.

4. Barnardo P, Jenkins J: Failed tracheal intubation in obstetrics: a 6‐year review in a UK region. Anaesthesia 2000, 55(7):690-694.

5. Kinsella SM, Winton AL, Mushambi MC, Ramaswamy K, Swales H, Quinn AC, Popat M: Failed tracheal intubation during obstetric general anaesthesia: a literature review. International journal of obstetric anesthesia 2015.

6. Pilkington S, Carli F, Dakin MJ, Romney M, De Witt KA, Dore CJ, Cormack RS: Increase in Mallampati score during pregnancy. Br J Anaesth 1995, 74(6):638-642.

7. Kodali BS, Chandrasekhar S, Bulich LN, Topulos GP, Datta S: Airway changes during labor and delivery. Anesthesiology 2008, 108(3):357-362.

8. Mushambi MC, Kinsella SM, Popat M, Swales H, Ramaswamy KK, Winton AL, Quinn AC: Obstetric Anaesthetists' Association and Difficult Airway Society guidelines for the management of difficult and failed tracheal intubation in obstetrics. Anaesthesia 2015, 70(11):1286-1306.

9. Hawthorne L, Wilson R, Lyons G, Dresner M: Failed intubation revisited: 17-yr experience in a teaching maternity unit. British Journal of Anaesthesia 1996, 76(5):680-684.

10. Balki MBBSMDM, Cooke MDFRCPCMary E, Dunington MARRTFCSRTS, Salman MDFRCPCA, Goldszmidt MDFRCPCE: Unanticipated Difficult Airway in Obstetric PatientsDevelopment of a New Algorithm for Formative Assessment in High-fidelity Simulation. Anesthesiology 2012, 117(4):883-897.

11. Lipman S, Carvalho B, Brock-Utne J: The demise of general anesthesia in obstetrics revisited: prescription for a cure. International journal of obstetric anesthesia 2005, 14(1):2-4.

12. Organization WH: WHO recommendatioins for the prevention and treatment or postpartum haemorrhage: evidence base. 2012.

13. Saving Mothers 2011-2013. Sixth report on the confidential enquiries into maternal deaths in south africa.

14. Carvalho J, Balki M, Windrim R: Oxytocin requirements at elective cesarean delivery: a dose-finding study. Obstetrics and gynecology 2004, 104(5 Pt 1):1005-1010.

15. Sheehan SR, Wedisinghe L, Macleod M, Murphy DJ: Implementation of guidelines on oxytocin use at caesarean section: a survey of practice in Great Britain and Ireland. European Journal of Obstetrics & Gynecology and Reproductive Biology 2010, 148(2):121-124.

16. Farina Z, Fawcus S: Oxytocin-ensuring appropriate use and balancing efficacy with safety. SAMJ: South African Medical Journal 2015, 105(4):271-273.

17. Kovacheva VP, Soens MA, Tsen LC: A Randomized, Double-blinded Trial of a “Rule of Threes” Algorithm versus Continuous Infusion of Oxytocin during Elective Cesarean Delivery. Anesthesiology 2015, 123(1):92-100.

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18. Butwick AJ: Postpartum hemorrhage and low fibrinogen levels: the past, present and future. International journal of obstetric anesthesia, 22(2):87-91.

19. Ducloy-Bouthors A-S, Susen S, Wong CA, Butwick A, Vallet B, Lockhart E: Medical Advances in the Treatment of Postpartum Hemorrhage. Anesthesia & Analgesia 2014, 119(5):1140-1147.

20. Wikkelsø AJ, Edwards HM, Afshari A, Stensballe J, Langhoff-Roos J, Albrechtsen C, Ekelund K, Hanke G, Secher EL, Sharif HF et al: Pre-emptive treatment with fibrinogen concentrate for postpartum haemorrhage: randomized controlled trial. British Journal of Anaesthesia 2015.

21. Roberts I, Shakur H, Coats T, Hunt B, Balogun E: The CRASH-2 trial: a randomised controlled trial and economic evaluation of the effects of tranexamic acid on death, vascular occlusive events and transfusion requirement in bleeding trauma patients. Health Technology Assessment 2013, 17(10):79.

22. Ducloy-Bouthors A-S, Jude B, Duhamel A, Broisin F, Huissoud C, Keita-Meyer H, Mandelbrot L, Tillouche N, Fontaine S, Le Goueff F et al: High-dose tranexamic acid reduces blood loss in postpartum haemorrhage. Critical Care 2011, 15(2):R117-R117.

23. Sentilhes L, Lasocki S, Ducloy-Bouthors A, Deruelle P, Dreyfus M, Perrotin F, Goffinet F, Deneux-Tharaux C: Tranexamic acid for the prevention and treatment of postpartum haemorrhage. British journal of anaesthesia 2015, 114(4):576-587.

24. Snegovskikh D, Clebone A, Norwitz E: Anesthetic management of patients with placenta accreta and resuscitation strategies for associated massive hemorrhage. Current Opinion in Anesthesiology 2011, 24(3):274-281.

25. Burtelow M, Riley E, Druzin M, Fontaine M, Viele M, Goodnough LT: How we treat: management of life-threatening primary postpartum hemorrhage with a standardized massive transfusion protocol. Transfusion 2007, 47(9):1564-1572.

26. Hypertension in Pregnancy: Executive Summary. Obstetrics & Gynecology 2013, 122(5):1122-1131.

27. Duley L, Meher S, Jones L: Drugs for treatment of very high blood pressure during pregnancy. Cochrane Database of Systematic Reviews 2013(7).

28. Pant M, Fong R, Scavone B: Prevention of Peri-Induction Hypertension in Preeclamptic Patients: A Focused Review. Anesthesia & Analgesia 2014, 119(6):1350-1356.

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