[Therapeutic control of premedication with famotidine given on the evening before surgery for the prevention of pneumonitis in heart surgery patients].
Pulmonary damage after aspiration of acid gastric content is one of the major risks of general anaesthesia. Antisecretory therapy with different H2-antagonists can effectively decrease the risk of aspiration. The effective dosage and the method and timing of administration remain unclear. PATIENTS AND METHODS. A series of 38 patients scheduled for elective cardiac surgery (coronary artery bypass graft) were premedicated at random at 10:00 p.m. on the evening prior to surgery with famotidine 40 mg and flunitrazepam 0.5 mg p.o. or with flunitrazepam alone. Continuous intragastric pH monitoring (720 values/h) with a combined glass electrode was started immediately after induction and continued for at least 12 h after surgery, in most cases up to extubation. The time periods analyzed were the first 30 min after induction, time of surgery, 12 h after surgery, and time of extubation. For each period the number of pH values less than 2.5 and pH less than 4, mean and median, and significance of differences were calculated. STATISTICS. Test statistics were evaluated using the Wilcoxon test and the Mann-Whitney U-test. RESULTS. (see Table 1, Fig. 1). The mean time interval between oral premedication and induction of anaesthesia was 9.7 h. There were no differences between the groups concerning age and duration of surgery. The average age was 51 in the group of treated patients (n = 15) and 59 years in the control group (n = 23). The average duration of surgery was 3.36 h and 4.02 h. During induction and in the following 30 min, in the famotidine treatment group 28.7% of all pH values were pH less than 2.5, as against 45.4% in the control group (P = 0.08). Intraoperative values: 16.3% pH less than 2.5 against 24.7% (not significant); 12 h postoperative: 21.1% vs 17.8% and during extubation 40% vs 21% (not significant). During induction there were more pH values less than 2.5 in the control than in the treatment group (P = 0.08). Treated patients had nearly 30% pH values less than 2.5 and therefore, a persisting risk of acid aspiration. In both groups intragastric acidity decreased during surgery. Postoperatively there was no difference between the two groups, and during extubation more patients in the famotidine-treated group had values below pH 2.5. CONCLUSION. Prophylaxis of acid aspiration before, during and after cardiac surgery can be achieved by increasing the pH of the gastric content. The timing and the method of administration must be selected to a safe decrease in intragastric acidity before the induction of general anaesthesia. Famotidine 40 mg given orally at 10.00 p.m. on the evening before surgery is not a reliable means of decreasing intragastric acidity or, consequently, of preventing of acid aspiration syndrome.