Cardiopulmonary interactions of salbutamol and hypoxaemia in healthy young volunteers

Abstract

1. Nebulised salbutamol is frequently used in the treatment of asthma and chronic obstructive pulmonary disease. Its effects on the cardiovascular system have been extensively investigated although as yet little is known concerning its effects on the pulmonary circulation, particularly during hypoxaemia. We have therefore examined the effects of nebulised salbutamol on pulmonary haemodynamics to see if it modifies hypoxic pulmonary vasoconstriction. 2. Eight healthy normal volunteers were studied on two separate occasions. After resting to achieve baseline haemodynamics patients were randomised to receive 5 mg salbutamol or placebo via a nebuliser. They were restudied after 30 min and then rendered hypoxaemic by breathing an N2/O2 mixture to achieve an SaO2 of 75-80%. Doppler echocardiography was used to measure mean pulmonary artery pressure (MPAP), cardiac output (CO) and hence pulmonary vascular resistance (PVR). 3. Treatment with salbutamol significantly increased MPAP during normoxaemia and hypoxaemia compared with placebo at 12.0 +/- 1.2 vs 8.0 +/- 0.7 mm Hg and 28.6 +/- 0.9 vs 25.2 +/- 1.0 mm Hg, respectively (P < 0.05). Salbutamol caused a significant increase in heart rate compared with placebo and effects were additive to those of hypoxia at 74 +/- 2 vs 67 +/- 3 beats min-1 during normoxaemia and 84 +/- 3 vs 77 +/- 4 beats min-1 during hypoxaemia, respectively (P < 0.05). Whilst systemic vascular resistance fell in response to salbutamol, PVR was unchanged by salbutamol during either normoxaemia or hypoxaemia. Cardiac output was increased by salbutamol and by hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)