The Haemodynamic response to dopamine infusion has been assessed in 30 patients in septic shock with myocardial dysfunction. Dopamine infusion resulted in a haemodynamic improvement as indicated by significant increases in cardiac output of 38.4% (p less than .001), stroke volume 18.7% (p less than .001), and mean arterial pressure of 33% (p less than .001). Despite the inotropic effect, left ventricular filling pressure did not change in 20 cases and increased in 10 cases. Mean peripheral resistance remained unchanged with a scatter of individual responses depending upon factors such as dopamine dose and initial vascular resistance. Dopamine increased intrapulmonary shunting by 48% (p less than .001), insignificantly decreased PaO2, increased mixed venous oxygen saturation by 16% (p less than .02) and decreased pulmonary vascular resistance by 15% (p less than .02). Both isoprenaline and dopamine improve stroke volume by an inotropic action, with an increase in venous return in the case of the latter and a reduction in afterload in the former. It is concluded that the usefulness of dopamine in septic shock may be limited in patients with previous myocardial disease because of the risk of increasing preload and in hypoxaemic patients because of the risk of increasing intrapulmonary shunting.

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The haemodynamic changes following the administration of morphine 0.15 and 0.30 mg kg" 1 i.v. were studied in 11 patients, free from known cardiac disease. All patients were acutely ill and their lungs were being ventilated mechanically. In those patients receiving 0.15 mg kg" 1 , the only haemodynamic change was a slight and transitory decrease in the systolic arterial pressure. In contrast, several changes were observed in patients receiving 0.30 mg kg" 1 : an immediate and prolonged decrease in the cardiac index was noted along with transient decreases in heart rate, stroke volume index, arterial pressure and left stroke work index. These results suggest that the haemodynamic cost of morphine 10 mg is negligible but could be significant when 20 mg has been administered and must be weighed against its beneficial effects in the critically ill patient.

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