[Continuous monitoring of spontaneous postoperative respiration. 3. The effect of amiphenazole on cutaneous oxygen and carbon dioxide partial pressure following gynecologic surgery under halothane anesthesia].

Methods: In an attempt to verify non-invasive respiratory monitoring for patients in the early postoperative period, cutaneous O2 and CO2 pressures were monitored in 30 female patients recovering from major gynaecologic surgery under halothane anaesthesia. In a double-blind and randomized fashion, in the recovery room the patients received a single intravenous bolus injection of placebo or 150 mg amiphenazole, a respiratory stimulant. The data were collected and stored in a personal computer, using the TCM3 system with a combination electrode for simultaneous measuring of cutaneous oxygen and carbon dioxide partial pressures (TINA, Radiometer) at 30-s intervals. The overall observation period was 240 min. Means and standard deviations were calculated for individual data and for data pooled at 15- or 60-min intervals. Groups were compared by means of the chi 2 test, Student's t-test, Wilcoxon rank sum test or analysis of variance (level of significance P < or = 0.05).

Results: The study groups were comparable with respect to demographic and anaesthesiological data. The partial pressures for both O2 and CO2 were not statistically significant between groups. Electrode heating was slightly higher with amiphenazole (n.s.), indicating a trend for peripheral vasodilation without a true improvement of spontaneous ventilation. pctO2 and pctCO2 levels were decreased or elevated, respectively, in the first observation hours and slowly returned to normal within the 240-min observation period. Episodes of hypercapnia (pct-CO2 > 50 or > 55 mm Hg) were frequent in the first 2 h (10-30% of individual data for pctCO2 > 50, 2-7% for pctCO2 > 55, respectively), indicating the need for close monitoring of spontaneous respiration after general anaesthesia with halothane.

Discussion And Conclusion: The present study confirmed that spontaneous respiration in the early postoperative period can be monitored non-invasively by measuring transcutaneous partial pressures of carbon dioxide and, less precisely due to large individual variations, oxygen. It showed that spontaneous respiration deteriorates after gynaecological surgery under halothane anaesthesia and recovers slowly during the next 4 h. The respiratory stimulant amiphenazole (150 mg i.v.) was of no significant value with respect to the improvement of ventilation.