Letters To The Editor: Letters & Announcements
We would like to reply to Dr. Brock-Utne’s letter concerning our Review Article (1). The statement concerning the effect of ranitidine and other drugs on the lower esophageal sphincter (LES) was taken from Reference 27 (2). The weight of evidence does not support the view of Dr. Brock-Utne that ranitidine increases LES pressure for the following reasons.
First, one of the studies showing that ranitidine increases LES pressure involved only 6 subjects (3); hence caution is required in accepting this work.
Second, the possibility of false positive results with ranitidine on the LES may be related to normal variations in LES pressure in the interdigestive states (4). LES pressure rises from phase one to phase three of the interdigestive states. This fact was not taken into account in the methodology of the study cited by the author (3).
Third, ranitidine and cimetidine are H2-receptor antagonists and thus would be expected to have similar effects. Cimetidine does not increase LES pressure (4,7,8), and the majority of studies have found also that ranitidine does not increase LES pressure (4,5,6).
General anesthesia for pregnant patients is becoming increasingly uncommon. Pregnancy is associated with increases in heart rate (9), and in our institution it would be very unusual for anesthesiologists to use atropine before induction of general anesthesia.
We agree that protective airway reflexes are impaired by many sedative agents, a concept that is well known, and we did not think that it was necessary to cite the historical articles of the 1970s enumerated by Dr. Brock-Utne (10,11). The main objective of this section was to characterize the components of these reflexes and describe the effect of drugs from more recent studies (12–14).
Dr. Brock-Utne recommends that a nasogastric tube be removed before a rapid sequence induction. We are unable to support his view for the following reasons.
First, and most importantly, there is good evidence that the nasogastric tube does not impair effective application of cricoid pressure (15,16).
Second, the nasogastric tube provides a passageway for the drainage of gastric contents.
Thus removal of the nasogastric tube is not only unnecessary but it may increase the risk of esophageal perforation in the event of retching during a rapid sequence induction.
Alexander Ng, FRCA
Graham Smith, MD, FRCA
1. Ng A, Smith G. Gastroesophageal reflux and aspiration of gastric contents in anesthetic practice. Anesth Analg 2001; 93: 494–513.
2. Cotton BR, Smith G. The lower oesophageal sphincter and anaesthesia. Br J Anaesth 1984; 56: 37–57.
3. Brock-Utne JG, Downing JW, Humphrey D. Effect of ranitidine given before atropine sulphate on lower oesophageal sphincter tone. Anaesth Intens Care 1984; 12: 140–2.
4. Smout AJPM, Bogaard JW, van Hattum J, Akkermans LMA. Effect of cimetidine and ranitidine on interdigestive and postprandial lower esophageal sphincter pressures and plasma gastrin levels in normal subjects. Gastroenterology 1985; 88: 557–63.
5. Denis P, Galmiche JP, Ducrotte P, et al. Effect of ranitidine on resting pressure and pentagastrin response of human lower esophageal sphincter. Dig Dis Sci 1981; 26: 999–1002.
6. Wallin L, Madsen T, Boesby S. Gastro-oesophageal function in normal subjects after oral administration of ranitidine. Gut 1983; 24: 154–7.
7. Wesdorp E, Bartelsman, Pape K, et al. Oral cimetidine in reflux esophagitis: a double blind controlled trial. Gastroenterology 1978; 74: 821–4.
8. Petrokubi RJ, Jeffries GH. Cimetidine Versus Antacid in Scleroderma with Reflux Esophagitis. Gastroenterology 1979; 77: 691–5.
9. Elton CD, MacDonald R. Maternal and neonatal physiology. In Aitkenhead AR, Rowbotham DJ, Smith G, eds. Textbook of Anaesthesia. Edinburgh: Churchill Livingstone, 2001: 325.
10. Brock-Utne JG, Winning TJ, Rubin J, Kingston HGG. Laryngeal incompetence during neuroleptanalgesia in combination with diazepam. Br J Anaesth 1976; 48: 699–701.
11. Rubin J, Brock-Utne JG, Greenberg M, Bortz J, Downing JW. Laryngeal incompetence during experimental “relative analgesia” using 50% nitrous oxide in oxygen. Br J Anaesth 1977; 49: 1005–7.
12. Murphy PJ, Langton JA, Barker P, Smith G. Effect of oral diazepam on the sensitivity of upper airway reflexes. Br J Anaesth 1993; 70: 131.
13. Erskine RJ, Murphy PJ, Langton JA, Smith G. Effect of age on the sensitivity of upper airway reflexes. Br J Anaesth 1993; 70: 574–5.
14. Caranza R, Nandwani N, Tring JP, et al. Upper airway reflex sensitivity following general anaesthesia for day-case surgery. Anaesthesia 2000; 55: 367–70.
15. Vanner RG, Pryle BJ. Regurgitation and oesophageal rupture with cricoid pressure: a cadaver study. Anaesthesia 1992; 47: 732–5.
16. Salem MR, Joseph NJ, Heyman HJ, et al. Cricoid compression is effective in obliterating the oesophageal lumen in the presence of a nasogastric tube. Anesthesiology 1985; 63: 443–6.