Efeito do propranolol e metoprolol nas respostas cárdio-respiratórias e metabólicas ao exercício / Effects of propranolol and metoprolol on cardiorespiratory And metabolic responses to exercise.

ABSTRACT

PurposeTo study the effects of intravenous propranolol and metoprolol on cardiorespiratory and metabolic responses to exercise. MethodsTwo groups of anaesthetized dogs (sodium pentobarbital, 33 mg/kg) were studied at rest and moderate exercise (induced by electrical stimulation) before and after metoprolol (0.4 mg/ Kg, n = 7) or propranolol (0.2 mg/kg, n = 10). Haemodynamic, metabolic and respiratory variables were measured. ResultsThere was a decrease in heart rate both at rest and during exercise after metoprolol and propranolol administration. The cardiac output, stroke volume and peripheral vascular resistance presented decreased responses to exercise after both drugs. O2 consumption and CO2 production were not altered signifcantly at rest but increased in a lesser degree during exercise. Propranolol administration reduced ventilation during rest and exercise, although the ventilatory response to exercise remained the same. Metoprolol administration did not affect ventilation at rest but reduced the ventilatory response to exercise leading to an increase of the PaCO2 Conclusion Propranolol and metoprolol effects on cardiovascular and metabolic variables measured at rest and during exercise were the same. The ventilatory effect with metoprolol administration was different from the observed with propranolol