Effect of doxapram on postoperative oxygenation in obese patients

Doxapram improves pulmonary function after upper abdominal surgery

The effects of doxapram on postoperative pulmonary function were studied in 40 ASA I and II patients randomly allocated to receive either doxapram 1.8 mg.kg-1.h-1 or placebo for 2 h immediately after elective cholecystectomy. The two groups displayed similar reductions of carbon dioxide production at 2 h and 6 h postoperatively, whereas oxygen consumption remained at preoperative levels for 24 h. Minute ventilation was similarly reduced in the two groups at 2 h and 6 h postoperatively, with corresponding increases in PaCO2. PaO2 was similarly and significantly decreased in both groups postoperatively, whereas P(A-a)O2 remained unchanged at 2 h and 6 h in doxapram-treated patients. FRC was reduced postoperatively in both groups, significantly more so in the control group at 6 h. Various indices of intrapulmonary gas distribution, including the functional (nitrogen) dead space, underwent similar changes in the two groups. By contrast, the physiological dead space was reduced in doxapram-treated patients at 2 h, 6 h and 24 h postoperatively, whereas no significant changes were seen in the control group. The ventilatory equivalent for CO2 was significantly lower in the doxapram-treated group, implying higher ventilatory efficiency. Our findings indicate that infusion of doxapram postoperatively attenuates the impairment of pulmonary function postoperatively, chiefly via effects on V'A/Q' ratios. No side effects of doxapram were observed.

Effect of doxapram on postoperative pulmonary complications after upper abdominal surgery in high-risk patients

In a double-blind randomised trial an infusion of doxapram, 2 mg per min for 6 h immediately after surgery and repeated on the first postoperative day, or the same volume of saline, was given to 39 patients who underwent upper abdominal surgery and who were at high risk of postoperative day, or the same volume of saline, was given to 39 patients who underwent upper abdominal surgery and who were at high risk of postoperative pulmonary complications. The patients were assessed pre-operatively and during the first 5 postoperative days by physical examination, spirometry, blood-gas analysis, and chest radiography. Postoperative pulmonary complications were defined as temperature over 38 degrees C for 2 days, abnormal auscultation, pathological radiography, and/or productive cough. Data from 16 patients per group were analysed. Significantly more patients in the placebo group had three criteria of postoperative pulmonary complication compared with the doxapram group (63% vs 19%). The doxapram group also had higher PaO2 postoperatively.