RESUMO
Morphine is known as the best analgesic for patients with acute myocardial infarction complicated by heart failure. In patients with uncomplicated acute myocardial infarction, buprenorphine has recently been indicated as an alternative to the widely used pentazocine. In order to verify if the haemodynamic effects of the two drugs differed, a randomized double-blind controlled trial was performed on 20 patients with uncomplicated acute myocardial infarction: 10 patients were treated with i.v. pentazocine 30 mg. and 10 patients with buprenorphine 0.30 mg. (equianalgesic doses). Right atrial, ventricular and pulmonary artery and capillary pressure, cardiac index, total pulmonary and total systemic resistance were measured before testing and 15', 30', 60', 180' and 240' after drug injection. PO2 was measured before drug injection and 30' and 60' later. Data were analyzed using the Wilcoxon test. All patients in each group showed uniform results: pentazocine increased total systemic resistance (mean increase 17%) while buprenorphine lowered it (mean reduction 12%) (P less than 0.05). Pentazocine lowered cardiac index (mean reduction 5.9%) while buprenorphine increased it (mean increase 9.3%) (P less than 0.05). Maximum changes occurred within 60' after the administration of both drugs. The other parameters did not change significantly from basal values. These results suggest that in patients with acute myocardial infarction uncomplicated by heart failure pentazocine and buprenorphine may be used in different haemodynamic situations. In the cases in which a reduction in total systemic resistance is desired, buprenorphine seems most suitable. However, in the presence of vagal reaction for instance, pentazocine may be administered.