Haemodynamic and respiratory effects of post-operative doxapram and almitrine in patients following pneumonectomy.

Respiratory analeptics have been shown to give important increases in pulmonary vascular resistance and pulmonary arterial pressure in hypoxaemic respiratory failure patients, but no studies have been carried out in the post-operative recovery period. The aim of this study was to compare the haemodynamic and respiratory effects of doxapram and almitrine infusion given over 1 h in patients who had just undergone pneumonectomy. Two hours after the end of anaesthesia, three groups of randomly selected patients were therefore given 3 mg kg-1 doxapram (n = 10), 1 mg kg-1 almitrine (n = 10) or placebo (n = 10). Measurements were made before and 15, 30, 60, 90, 120 and 180 min after the beginning of the infusion. There was an immediate 15-20% fall (P less than 0.01) in PaCO2 and a 20% rise in PaO2 (P less than 0.005), identical for both drugs; the variations in the placebo group became significant only after 60 min. Heart rate and cardiac index did not change. Mean arterial pressure did not change with doxapram, but decreased by 20% during the infusion of almitrine (P less than 0.01), remaining low until the 90th min (P less than 0.05). This hypotension was due to a decrease in peripheral arterial resistance (P less than 0.05) and a small decrease in right atrial pressure (P less than 0.05). The mean pulmonary arterial and wedge pressures were increased before starting the infusion, and did not vary significantly. Pulmonary arterial resistance increased with both analeptics but only significantly with the doxapram (P less than 0.05) at 5, 60 and 90 min; however, there was no significant difference between doxapram and almitrine. The post-operative respiratory efficiency of these drugs has been confirmed, there being no difference between almitrine and doxapram. The haemodynamic effects were moderate, especially with almitrine. Both of these drugs, therefore, may be recommended for use after lung surgery.