Oxygen Delivery and Consumption in Patients Who Are Comatose After Out-of-Hospital Cardiac Arrest Are Affected by Blood Pressure Target

BACKGROUND: In the management of patients resuscitated from out-of-hospital cardiac arrest, a primary goal is to restore sufficient oxygen delivery (DO2) to meet demands in oxygen consumption (VO2). METHODS AND RESULTS: This post hoc analysis of the BOX (Blood Pressure and Oxygen Targets) study included adult patients who were comatose and experienced out-of-hospital cardiac arrest from a presumed cardiac cause, who were randomized to a mean arterial blood pressure (MAP) target of 63 mm Hg (MAP63) or 77 mm Hg (MAP77) and a Restrictive PaO2 target of 9 to 10 kPa versus a Liberal target of 13 to 14 kPa in a 2×2 factorial design. A pulmonary artery catheter was inserted following randomization. DO2 and VO2 were calculated as: DO2=cardiac output × arterial oxygen content, and VO2= cardiac output × arteriovenous oxygen difference. Of 789 patients, 730 (92.5%) were included in this substudy. A total of 362 patients were randomized to MAP77, and 368 to MAP63, 368 to a liberal Pao2 target, and 362 to a restrictive target. At all prespecified time points, DO2 in MAP77 was higher compared with MAP63, with a cumulative treatment effect of 203 L (95% CI, 132-274) O2 after 36 hours. VO2 was higher in MAP77 after 36 hours, with a cumulative treatment effect of 21.9 L (95% CI, 5.8-38) O2, compared with the MAP63 group. CONCLUSIONS: Targeting a MAP of 77 mm Hg resulted in an overall increase in DO2 and a smaller increase in VO2 compared with a MAP target of 63 mm Hg. A higher Pao2 target did not result in any difference in DO2 or VO2.