To the Editor:
I was impressed by and envious of the high caseload, 1699 cesarean sections over 5 mo, that enabled Rocke et al.  to complete their study with intravenous omeprazole so quickly . The same authors have published a similar study with ranitidine . The unanswered question is: which regimen, omeprazole or ranitidine, do they prefer? Although the studies were consecutive, the authors are in the best position to give advice because they have all the original data and their experience in this field is unequaled. Their large samples and identical experimental conditions would reduce the problem of retrospective comparisons. Although they have not studied all permutations of drugs to make perhaps the definitive recommendation, what is their current regimen to reduce the risk of acid aspiration before emergency cesarean section at their hospital?
I have presented a similar but smaller comparative study of intravenous omeprazole 40 mg with ranitidine 50 mg, both with and without metoclopramide 10 mg, before emergency cesarean section . There were no differences in gastric acidity or volume among the four groups. I agree with Rocke et al.  that metoclopramide does not appear to reduce gastric volume. Another study in this hospital comparing citrate and metoclopramide with citrate alone before emergency cesarean section came to the same conclusion .
Although Rocke et al. state that omeprazole had only been previously evaluated for elective cesarean section, quoting two of my early studies, my colleagues did report in 1992 that regular oral omeprazole during labor was less satisfactory than regular oral ranitidine at reducing gastric acidity and volume before emergency cesarean section .
Neither oral nor intravenous omeprazole is currently used in the labor ward in Hong Kong, partly because ranitidine is considerably less expensive.
Tony Gin, FRCA, FANZCA, MD
Department of Anaesthesia and Intensive Care, Chinese University of Hong Kong, Prince of Wales Hospital, Shatin, N.T., Hong Kong
1. Rocke DA, Rout CC, Gouws E. Intravenous administration of the proton pump inhibitor omeprazole reduces the risk of acid aspiration at emergency cesarean section. Anesth Analg 1994;78:1093-8.
2. Rout CC, Rocke DA, Gouws E. Intravenous ranitidine reduces the risk of acid aspiration of gastric contents at emergency cesarean section. Anesth Analg 1993;76:156-61.
3. Gin T, Stuart JC, Kan AF, et al. IV ranitidine or omeprazole for emergency casesarean section. Anaesth Intensive Care 1994;22:483.
4. Gin T, Kan AF, Yau G. Acid aspiration prophylaxis at emergency caesarean section. Anaesth Intensive Care 1994;22:97.
5. Yau G, Kan AF, Gin T, Oh TE. A comparison of omeprazole and ranitidine for prophylaxis against aspiration pneumonitis in emergency caesarean section. Anaesthesia 1992;47:101-4.