ANESTH ANALG 58:426-427. 1979
Cimetidine for Prophylaxis of Aspiration Pneumonitis: Comparison of Intramuscular and Oral Dosage Schedules Larry Weber, MD,*and Carol A. Hirshman, MDt Aspiration of gastric contents into the tracheobronchial tree is a major cause of anesthesia-related morbidity and mortality.' Silent regurgitation of gastric contents occurs more frequently than is realized, even with an endotracheal tube in place.2* A pH value of less than 2.5 is generally considered the critical level for the development of pulmonary damage!. Routine antacid prophylaxis is established practice in obstetric anesthesia and has been advocated for all anesthesia.6+'Cimetidine, a new histamine-2 receptor antagonist: increases gastric pH and decreases gastric volume.' A number of studies have recently evaluated the efficacy of oral doses of cimetidine premedication at raising gastric PH.'"-'~ The aim of this study was to compare intramuscular with oral doses of cimetidine along with routine premedication for elective surgery with respect to increasing gastric pH.
Methods Twenty-six consenting adult patients, A.S.A. class I or 11, scheduled for 8 a.m. elective surgery requiring an endotracheal intubation, were studied. All patients fasted after midnight and were prernedicated with morphine sulfate, 0.1 to 0.2 mg/kg at 6:30 a.m. Patients were randomly assigned to three groups. Groups were similar with regard to weight, age, and sex. Group 1 received no additional premedication. Group 2 received cimetidine, 300 mg orally (P.o.), at bedtime and 300 mg p.0. at 6:30 a.m. with less than 30 ml of water. Group 3 receivedKimetidine, 300 mg P.o., at bedtime and 300 mg IM at 630 a.m. * Resident in Anesthesia.
t Assistant Professor.
Received from the Department of Anesthesiology, University of Oregon Health Sciences Center, Portland, Oregon 97201. Accepted for publication M a y 10,1979. Reprint requests to Dr. Hirshman.
426
ANESTHESIA AND ANALGESIA Sept-Oct 1979
VOI 513.NO 5.
To evaluate the necessity for a bedtime dose, 10 additional patients (group 4) received oral cimetidine, 300 mg, 90 minutes prior to surgery without a preceding dose. Anesthesia was induced with thiopental, and tracheal intubation was accomplished with the aid of succinylcholine. A no. 16 nasogastric tube was passed immediately following intubation and all available gastric contents evacuated. The volume and pH of the gastric contents were measured. All pH values were measured with a Beckman 76008 digital pH meter and no. 39183 probe combination electrode. The gastric volumes obtained are not considered to represent accurately the total wolume of the gastric contents as no attempt was made to fully empty the stomach by altering the position of the patients. The three groups were compared with respect to pH values by a one-way analysis of variance and a multiple comparison test.I3 Group 4 was compared to group 1 with respect to pH values by an unpaired t-test.14 The level of statistical significance used was less than or equal to 0.05.
Results The mean pH values of the gastric aspirates are shown in the Table. The distribution of pH values are shown in the Figure. The groups that received cimetidine, 300 mg p.0. at bedtime and 300 mg either p.0. or IM at 6:30 a.m., had gastric aspirates with pH levels significantly higher than the control group when measured 90 minutes later. The group receiving cimetidine intramuscularly had gastric aspirates with significantlyhigher pH levels than the group receiving the drug orally. One patient who received cimetidine orally had a pH below 2.5. Patients receiving only cimetidine, 300 mg p.0. at 6:30 a.m., had gastric aspirates that were not significantly different from the pH levels of control patients. Three patients in this latter group had pH values less than 2.5. Gastric juice could not be obtained from six patients who were not included in the study.
Discussion The peak effect of cimetidine on gastric pH occurs 4 to 6 hours after oral administration.12Stoelting" found that 300 mg of cimetidine given orally 90 minutes before induction of anesthesia increased gastric pH to levels above 2.5 in some but not all patients.
CLINICAL REPORTS TABLE Gastric Residue from CimaMinaTrentod and Control Path& C W n e - t r 8 a t e d patients
control patients Total patients pH (mean f SEM) Range p value
10 2.92 f 0.49
300 mg p.0. h.8. 300 mg P.O. a.m.
300 mg D.O. h.8. 300 me i.m. a.m.
10 5.1 0.61 2.2-7.5 c0.05’
6 7.3 0.31 6.4-8.1
Cimetidine for Prophylaxis of Aspiration Pneumonitis: Comparison of Intramuscular and Oral Dosage Schedules Larry Weber, MD,*and Carol A. Hirshman, MDt Aspiration of gastric contents into the tracheobronchial tree is a major cause of anesthesia-related morbidity and mortality.' Silent regurgitation of gastric contents occurs more frequently than is realized, even with an endotracheal tube in place.2* A pH value of less than 2.5 is generally considered the critical level for the development of pulmonary damage!. Routine antacid prophylaxis is established practice in obstetric anesthesia and has been advocated for all anesthesia.6+'Cimetidine, a new histamine-2 receptor antagonist: increases gastric pH and decreases gastric volume.' A number of studies have recently evaluated the efficacy of oral doses of cimetidine premedication at raising gastric PH.'"-'~ The aim of this study was to compare intramuscular with oral doses of cimetidine along with routine premedication for elective surgery with respect to increasing gastric pH.
Methods Twenty-six consenting adult patients, A.S.A. class I or 11, scheduled for 8 a.m. elective surgery requiring an endotracheal intubation, were studied. All patients fasted after midnight and were prernedicated with morphine sulfate, 0.1 to 0.2 mg/kg at 6:30 a.m. Patients were randomly assigned to three groups. Groups were similar with regard to weight, age, and sex. Group 1 received no additional premedication. Group 2 received cimetidine, 300 mg orally (P.o.), at bedtime and 300 mg p.0. at 6:30 a.m. with less than 30 ml of water. Group 3 receivedKimetidine, 300 mg P.o., at bedtime and 300 mg IM at 630 a.m. * Resident in Anesthesia.
t Assistant Professor.
Received from the Department of Anesthesiology, University of Oregon Health Sciences Center, Portland, Oregon 97201. Accepted for publication M a y 10,1979. Reprint requests to Dr. Hirshman.
426
ANESTHESIA AND ANALGESIA Sept-Oct 1979
VOI 513.NO 5.
To evaluate the necessity for a bedtime dose, 10 additional patients (group 4) received oral cimetidine, 300 mg, 90 minutes prior to surgery without a preceding dose. Anesthesia was induced with thiopental, and tracheal intubation was accomplished with the aid of succinylcholine. A no. 16 nasogastric tube was passed immediately following intubation and all available gastric contents evacuated. The volume and pH of the gastric contents were measured. All pH values were measured with a Beckman 76008 digital pH meter and no. 39183 probe combination electrode. The gastric volumes obtained are not considered to represent accurately the total wolume of the gastric contents as no attempt was made to fully empty the stomach by altering the position of the patients. The three groups were compared with respect to pH values by a one-way analysis of variance and a multiple comparison test.I3 Group 4 was compared to group 1 with respect to pH values by an unpaired t-test.14 The level of statistical significance used was less than or equal to 0.05.
Results The mean pH values of the gastric aspirates are shown in the Table. The distribution of pH values are shown in the Figure. The groups that received cimetidine, 300 mg p.0. at bedtime and 300 mg either p.0. or IM at 6:30 a.m., had gastric aspirates with pH levels significantly higher than the control group when measured 90 minutes later. The group receiving cimetidine intramuscularly had gastric aspirates with significantlyhigher pH levels than the group receiving the drug orally. One patient who received cimetidine orally had a pH below 2.5. Patients receiving only cimetidine, 300 mg p.0. at 6:30 a.m., had gastric aspirates that were not significantly different from the pH levels of control patients. Three patients in this latter group had pH values less than 2.5. Gastric juice could not be obtained from six patients who were not included in the study.
Discussion The peak effect of cimetidine on gastric pH occurs 4 to 6 hours after oral administration.12Stoelting" found that 300 mg of cimetidine given orally 90 minutes before induction of anesthesia increased gastric pH to levels above 2.5 in some but not all patients.
CLINICAL REPORTS TABLE Gastric Residue from CimaMinaTrentod and Control Path& C W n e - t r 8 a t e d patients
control patients Total patients pH (mean f SEM) Range p value
10 2.92 f 0.49
300 mg p.0. h.8. 300 mg P.O. a.m.
300 mg D.O. h.8. 300 me i.m. a.m.
10 5.1 0.61 2.2-7.5 c0.05’
6 7.3 0.31 6.4-8.1
