Aspiration of gastric contents is still a major cause of anaesthesia-related death in obstetric practice (1, 2, 3). It usually occurs during the course of a general anaesthesia, more so when intubation is difficult (4).
Most mothers in labour are unlikely to receive general anaesthesia (5). In those with a regional block placed during labour this can usually be extended cephalad for use during Caesarean section (CS). Since the probability of general anaesthesia and thus aspiration is relatively low in parturients, it is difficult to justify the use of acid aspiration prophylaxis in labouring women (5). In 1988 in the United Kingdom, it was shown that up to 25% of 288 departments surveyed (6) did not administer aspiration prophylaxis to mothers in labour. Besides the drug costs and discomfort to the mother (5, 6) the H2 receptor antagonists can alter local anaesthetic metabolism (7). This creates a risk of local anaesthetic toxicity (Chapter 89) in mothers with ongoing epidural block, who are given regular doses of these drugs. Prophylaxis should be limited to those at high risk of requiring a CS, and this should be in the form of regular oral ranitidine.
All mothers for CS be it elective or emergency, require aspiration prophylaxis (8) (Chapter 45). Despite the increasing trend towards CS under regional anaesthesia, an epidural failure rate of up to 20% (9, 10, 11) still necessitates preparation of all these mothers as for general anaesthesia as this is a sizeable group at risk. The 1988 survey in the United Kingdom (6) showed that this is religiously given in all the departments and there is no relaxation of this practice.
Many obstetric units recommend a regimen along the following lines:
(a) Elective Caesarean section (6) - 150 mg oral ranitidine the night before and again on the morning of the operation. This is followed by 30 mls of 0.3 molar sodium citrate before the commencement of the regional block.
(b) Emergency Caesarean section (6, 12) - slow intravenous ranitidine, 50 mg at the time the need for CS is determined if this has not been given regularly during labour. Sodium citrate is given immediately before commencement of surgery.
References:
1. Tomkinson J, Turnbull A, Robson G, et al. Report on confidential enquiries into maternal deaths in England and Wales 1976-1978. London: Her Majesty's Stationery Office, 1982.
2. Turnbull A, Tindall VR, Robson G, et al. Report on confidential enquiries into maternal deaths in England and Wales 1979-1981. London: Her Majesty's Stationery Office, 1986.
3. Turnbull A, Tindall VR, Beard RW, et al. Report on confidential enquiries into maternal deaths in England and Wales 1982-1984. London: Her Majesty's Stationery Office, 1989.
4. Macdonald AG. The gastric acid problem. Recent Advances in Anaesthesia and Analgesia. 15: 8: 107-131.
5. Thorburn J, Moir DD. Antacid therapy for emergency Caesarean section. Anaesthesia 1987; 42; 352-355.
6. Tordoff SG, Sweeney BP. Acid aspiration prophylaxis in 288 obstetric anaesthetic departments in the United Kingdom. Anaesthesia 1990; 45; 776-7
7. Wilson CM, Moore J, Ghaly RG et al. Plasma bupivacaine concentration associated with extradural anaesthesia for Caesarean section: Influence of pretreatment with ranitidine. British Journal of Anaesthesia 1986; 58; 1330P-1331P.
8. May AE. The confidential enquiry into maternal deaths 1988-1990. British Journal of Anaesthesia Editorial 1. 1994; 73; 129-131.
9. Milne MK, Murray Lawson JI. Epidural analgesia for Caesarean section. British Journal of Anaesthesia 1973; 45; 1206-1210.
10. Thorburn J, Moir DD. Epidural analgesia for elective Caesarean section: Technique and its assessment. Anaesthesia 1980:3 5:3-6.
11. Chamberlain G, Wright A, and Steer P. Pain and its relief in labour: Report of the 1990 NBT survey. (1993) Churchill Livingstone, Edinburgh.
12. Rout CC, Rocke DA, Gouws E. Intravenous ranitidine reduces the risk of acid aspiration of gastric contents at emergency Caesarean section. Anaesthesia and Analgesia 1993; 76; 156-61.