MIDAZOLAM ATTENUATES THE METABOLIC AND CARDIOPULMONARY RESPONSES TO AN ACUTE INCREASE IN OXYGEN-DEMAND

Critically ill patients are subjected to routine clinical activities t hat increase oxygen demand. This results in increased heart rate, bloo d pressure, minute ventilation, and oxygen delivery in patients with o ften already compromised cardiopulmonary systems. This study examines whether the benzodiazepine, midazolam, could attenuate the increase in metabolism, respiration, and circulation seen during chest physical t herapy. Two groups of mechanically ventilated postoperative patients w ere studied. One group (n=15) received, in random order, 0.015 mg/kg o f midazolam and placebo prior to two consecutive chest physical therap y sessions, while the other (n=13) received 0.030 mg/kg and placebo. B oth doses of midazolam significantly attenuated the increases in oxyge n consumption, heart rate, and systemic blood pressure observed during placebo administration. The cardiac output increase was also attentua ted. Although midazolam reduced minute ventilation and respiratory rat e, no excess CO2 retention occurred when the drug was administered lik ely as the result of reduced CO2 production. The administration of mid azolam (0.015 mg/kg and 0.030 mg/kg) prior to chest physical therapy r educes metabolic, hemodynamic, and ventilatory responses to chest phys ical therapy.