Hemodynamic and metabolic effects of morphine in the critically ill.

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Abstract
To assess the effects of i.v. injection of morphine, 0.5 mg/kg, hemodynamic studies were performed on 24 critically ill patients under controlled ventilation. An esophageal balloon was used to estimate intrapleural pressure and transmural cardiac filling pressures were calculated. After injection of morphine, there were significant decreases in heart rate (13%), cardiac index (18%), stroke index (17%) and arterial pressure (15%) and there was a nonsignificant increase in esophageal pressure (15%). Transmural cardiac filling pressures decreased significantly (21% for the pulmonary wedge pressure); intravascular filling pressures were unchanged. O2 consumption decreased significantly, by 21%, in 10 patients with initially elevated O2 consumption and by 9% in 14 patients with initial normal O2 consumption. The O2 extraction ratio was unchanged, suggesting that the decrease in O2 consumption was caused by decreased O2 demand rather than by inadequate O2 delivery. The hemodynamic effects of morphine (0.5 mg/kg) administered to critically ill patients apparently were associated with a significant decrease in O2 consumption, which probably reflected sedation and analgesia.