DOPAMINE DEPRESSES MINUTE VENTILATION IN PATIENTS WITH HEART-FAILURE

Background-Low-dose dopamine is frequently used in patients In the int ensive care setting. Dopamine may inhibit chemoreceptor afferents and hence decrease chemoreflex sensitivity to hypoxia, Methods and Results -In a double-blind, randomized, crossover study, we determined the eff ects of dopamine (5 mu g . kg(-1) . min(-1)) and placebo infusion on o xygen saturation, minute ventilation, and sympathetic nerve activity d uring normoxia and 5 minutes of hypoxia in 10 normal young subjects. W e further investigated the effects of dopamine and placebo on minute v entilation during normoxic breathing in 8 patients with severe heart f ailure and in 8 age-matched control subjects. Dopamine did not decreas e minute ventilation during normoxia in normal subjects. During hypoxi a, minute ventilation was 12.9+/-1.3 L/min on dopamine and 15.8+/-1.5 L/min on placebo (P<0.0001). Oxygen saturation during hypoxia was lowe r with dopamine (78+/-3%) than placebo (84+/-2%; P<0.0001). Sympatheti c nerve activity during hypoxia was not enhanced with dopamine despite the lower O-2 saturation. Subjects were able to maintain a voluntary apnea to a lower oxygen saturation on dopamine than on placebo (P<0.05 ), In heart failure patients breathing room air, but not in age-matche d control subjects, dopamine decreased minute ventilation despite decr eased oxygen saturation and increased PETCO2 during dopamine (all P le ss than or equal to 0.02). Conclusions-Dopamine inhibits chemoreflex r esponses during hypoxic breathing in normal humans, preferentially aff ecting the ventilatory response more than the sympathetic response. Do pamine also depresses ventilation in normoxic heart failure patients b reathing room air. Ventilatory inhibition by low-dose dopamine may adv ersely influence outcome in hypoxic patients, especially in patients w ith heart failure.