PULMONARY HEMODYNAMIC EFFECTS OF AEROSOLS OF ISOPROTERENOL AND IPRATROPIUM IN NORMAL SUBJECTS AND PATIENTS WITH REVERSIBLE AIRWAY-OBSTRUCTION

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Abstract
Hemodynamic effects of isoproterenol sulfate, ipratropium bromide and Freon propellant were measured in 8 normal subjects and 10 patients with reversible airway obstruction who were placed in the supine position. Pulmonary capillary blood flow (equivalent to cardiac output when right-to-left shunt is negligible), diffusing capacity, O2 consumption, pulmonary tissue plus capillary blood volume and functional residual capacity were obtained by a rebreathing technique before and serially for 3 h after drug administration. Arterial O2 saturation by ear oximetry, blood pressure and heart rate were monitored. No changes in these parameters occurred in normal subjects after inhalation of 150 .mu.g of isoproterenol sulfate or 80 .mu.g of ipratropium bromide. Cardiac output increased slightly in patients with reversible airway obstruction 5 min after isoproterenol inhalation but then returned to baseline values; 600 .mu.g of isoproterenol sulfate produced a slightly greater transient increase in cardiac output 5 min after inhalation than the 150-.mu.g dose. Ipratropium bromide administered in the therapeutic dose of 80 .mu.g and the excessive dose of 320 .mu.g was virtually devoid of cardiac effects. Freon propellant, although it did not produce clearcut cardiac effects 5 min after inhalation, increased diffusing capacity 15 min after administration. Apparently, therapeutic and excessive doses of aerosolized isoproterenol in patients with reversible airway obstruction produce a transient excitatory effect on the heart; if it is necessary to avoid this adverse effect, then ipratropium might be a useful alternative.