Cimetidine in the prevention of the pulmonary acid aspiration (Mendelson's) syndrome

Comparison of roxatidine and famotidine on nocturnal gastric juice secretion

Adult patients with symptoms of gastric disease were randomly assigned to two treatment groups (roxatidine group, n = 115; famotidine group, n = 113) or untreated control group (placebo, n = 111). The treatment groups randomly received 75 mg of roxatidine or 20 mg of famotidine at 9 pm, and 12 - 13 h later gastric juice secretion was measured with gastric X-ray films in both groups. Mean gastric juice secretion was significantly lower in the treated groups (roxatidine, 16.1 ml/12 h; famotidine, 19.9 ml/12 h) than in the untreated controls (placebo, 49.5 ml/12 h). Gastric juice suppression by roxatidine and by famotidine, respectively, was 82% and 37% in patients with gastric ulcer; 71% and 39% in patients with duodenal ulcer; 70% and 64% in patients with gastritis; and 68% and 86% in patients with no evidence of disease. It is concluded that roxatidine was more effective than famotidine for gastric juice suppression in patients with peptic ulcer. In patients with no evidence of gastric disease, however, famotidine was more effective than roxatidine.

A volume and pH determination of tracheal residue postaspiration

An endotracheal tube containing pH sensors for rapid detection of episodic acid aspiration was combined with a design that provides a means of suctioning tracheal residue resulting from gastric regurgitation and aspiration. The efficacy of the tube operation was demonstrated in two patients who aspirated gastric contents.

Intraocular pressure--physiology and implications for anaesthetic management

The major factors controlling intraocular pressure during surgery are the dynamic balance between aqueous humour production in the ciliary body and its elimination via the canal of Schlemm; the auto-regulation and chemical control of choridal blood volume; the extraocular muscle tone and vitreous humour volume. Prior to surgical incision of the anterior chamber in open intraocular procedures, a low-normal intraocular pressure is mandatory to avoid the hazards of iris or lens prolapse and vitreous loss associated with sudden decompression. In general, the central nervous system depressant drugs, hypnotics, narcotics, major tranquillizers, volatile anaesthetic agents are associated with a reduction in intraocular pressure, with the exception of ketamine and possibly trichloroethylene. The mechanism of action of anaesthetic agents in reducing intraocular pressure may involve a direct effect on central diencephalic control centres, reduction of aqueous production, facilitation of aqueous drainage or relaxation of extraocular muscle tone. Succinylcholine administration is associated with a significant rise in intraocular pressure, with a peak increase between two to four minutes following administration and a return to base line values after six minutes. The intraocular hypertensive effect may be due to a tonic contraction of the extraocular muscles, choroidal vascular dilatation or relaxation of orbital smooth muscle. Despite many claims to the contrary, no reported method to date has been shown to consistently prevent the intraocular hypertensive response to intravenous succinylcholine administration. Because the non-depolarizing relaxants are associated with a reduced intraocular pressure, a barbiturate-non-depolarizing relaxant technique utilizing preoxygenation and cricoid pressure has evolved as the most commonly employed induction technique for the emergency repair of a penetrating eye injury. The alternative non-depolarizing relaxant pretreatment-barbiturate-succinylcholine technique may offer the advantages of more rapid onset of relaxation with only minor increases in intraocular pressure and in a carefully controlled rapid sequence induction technique may be the most acceptable method of handling emergency penetrating eye injuries.

Cimetidine in anesthesia: does it minimize the complications of acid aspiration?

The use of cimetidine, an H2-receptor antagonist, to minimize the complications of acid aspiration pneumonia is reviewed. Since Mendelson's early description of acid aspiration in 66 obstetrical patients, attempts have been made to decrease gastric acidity by administering perioperative antacids and/or antihistamine drugs such as atropine and glycopyrrolate. In this review of the literature, strict attention is given to study design and subject selection, methods of collecting gastric samples and reporting both pH and volume measurements, and medications taken on admission, given preoperatively, and as anesthetics. Clinical trials evaluating cimetidine alone and compared with other prophylactic regimens were reviewed, detailing the timing, route, and frequency of drug administration. Cimetidine appears to be effective in minimizing complications of acid aspiration since gastric acidity (pH less than 2.5) is a contributing factor in both the morbidity and mortality of this disease state. In general terms, cimetidine 300 mg po 1.5-2.0 h prior to intubation or 45-60 minutes iv before surgery will decrease gastric acidity below the critical level. This effect may be maintained for up to three hours. Perioperative cimetidine administration, to minimize the complications of acid aspiration, appears to be safe in terms of drug-drug interactions and effects on labor, the fetus, and the newborn child.

Protection against acid pulmonary aspiration with cimetidine

Gastric pH values were studied prior to, and up to, ninety minutes after an intravenous injection of cimetidine 200 mg given before general anaesthesia, in twenty surgical patients, all with a gastric pH less than 3.5. At thirty, sixty and ninety minutes, sixteen, eighteen and twenty patients had a gastric pH greater than 3.5 respectively. In conclusion, the results of the present study indicate that cimetidine 200 mg given intravenously 90 minutes before surgery will reduce the hazard of chemical pneumonitis should stomach content be aspirated.

Comparative trial of the effect of ranitidine and cimetidine on gastric secretion in fasting patients at induction of anaesthesia

A comparative trial of the H2-receptor antagonists, cimetidine and ranitidine, on gastric pH and volume, was conducted in 168 healthy patients coming to elective surgery. The drugs were administered in random fashion either intravenously (ranitidine 50 mg or 100 mg, cimetidine 300 mg or placebo) or orally (ranitidine 150 mg, cimetidine 300 mg or placebo). The patients received the drugs or placebo 45 minutes to five hours before operation. After induction of anaesthesia, a nasogastric tube was passed and the stomach contents were aspirated. The volume and pH were measured. Those patients receiving ranitidine 50 or 100 mg or cimetidine 300 mg intravenously had statistically significantly higher gastric pH compared to those receiving placebo, but up to eight percent of patients has a pH less than 2.5. Oral administration of cimetidine 300 mg or ranitidine 150 mg were also superior when compared to placebo. However, 25 per cent of the patients receiving oral cimetidine had a pH less than 2.5; cimetidine orally was statistically significantly inferior to ranitidine 100 mg given intravenously. We conclude that the intravenous use of either ranitidine or cimetidine is an acceptable method to decrease the acidity of gastric contents before induction of anaesthesia. Orally, ranitidine appears to be a better choice than cimetidine in the doses studied. Both ranitidine and cimetidine need to be given at least 45 minutes before induction of anaesthesia to be effective; therefore the use of these agents to decrease the risk of acid pulmonary aspiration syndrome by no means obviates the need for proper anaesthesia technique during induction of anaesthesia.

Sodium citrate: an alternative antacid for prophylaxis against aspiration pneumonitis

In a double-blind study, 107 patients undergoing elective and emergency surgical procedures were given 15 ml of either sodium citrate 0.3 M or placebo 10 minutes before induction of anaesthesia. Gastric contents were sampled immediately after induction and the pH was measured. The mean pH of the Gastric contents of patients given sodium citrate was 5.67, whereas for those given the placebo it was 3.21 (p less than 0.001). Of patients given sodium citrate 92% had a gastric pH above 3.0 compared with only 37% in the placebo group (p less than 0.001). At the end of surgery gastric contents were emptied as completely as possible and the volume and pH measured. There was no significant difference in the mean volume of gastric contents in the two groups. In neither group was the mean pH at the end of surgery significantly different from that after induction.

[Control of gastric acidity with cimetidine given as premedication before general anesthesia: efficacy and tolerance]

Cimetidine 400 mg was administered intramuscularly 60 minutes before the beginning of general anaesthesia. The double blind experiment was conducted on 84 patients divided in two groups: cimetidine and control. There was no difference in gastric fluid volume between the two groups during general anaesthesia, but acid secretion decreased significantly in the cimetidine group. Values of pH lower than 2.5 were observed in 33.3 per cent at induction and 34 per cent at recovery in the control group against 14.6 per cent and 0 per cent in the cimetidine group. Clinical tolerance to cimetidine was studied in 100 patients during operation. Cimetidine did not alter pharmacological action of usual anaesthetics. There were no significant changes in cardiovascular and electrocardiographic data.