ACUTE EFFECTS OF INTRAVENOUS COCAINE ON PULMONARY-ARTERY PRESSURE ANDCARDIAC INDEX IN HABITUAL CRACK SMOKERS

Background: Some habitual crack cocaine smokers who deny IV drug abuse show decreased pulmonary transfer of carbon monoxide (DCO). We specul ated that repeated elevations in pulmonary artery pressure (PAP) might cause pulmonary capillary damage and result in a lowered DCO, or that the reduction could be due to anoxic lung injury secondary to repeate d episodes of cocaine-induced pulmonary vascular constriction. Study O bjective: Compare the acute effects of IV cocaine HCl and placebo on P AP, cardiac stroke volume, and cardiac output estimated indirectly by continuous Doppler echocardiogaphy. Design: A single-blind crossover s tudy in which placebo always preceded the active drug. Subjects: Ten c urrent crack-smoking subjects, 32 to 47 years of age, with a history o f limited previous IV cocaine use. Methods: PAP, cardiac stroke volume , heart rate, and BP were measured continuously after injection of pla cebo followed by cocaine HCl (0.5 mg/kg). Results: IV cocaine resulted in no significant change in PAP (-0.14+/-3.3[SD] mm Hg, 95% confidenc e interval [CI] for difference -2.45, +2.21). Stroke volume index show ed no significant change after cocaine (-0.1+/-2.0 mL; 95% CI, -1.5, 1.3). Heart rate showed a significant increase (10.0+/-7.2 min(-1); p= 0.0017, 95% CI, +4.9, +15.1). Cardiac index showed a significant incre ase (0.48+/-0.32 L/min; p=0.0012, 95% CI, +0.25, +0.71). Pulmonary vas cular resistance showed no significant change (-44+/-101 dyne . s . cm (-5)/m(2), 95% CI, -116, +29). Conclusions: IV cocaine HCl does not ca use short-term increases in PAP or stroke volume index, but causes an increase in cardiac index due to its chronotropic effect.