Abstract
BACKGROUND: In the management of patients resuscitated from out-of-hospital cardiac arrest, a primary goal is to restore sufficient oxygen delivery (DO(2)) to meet demands in oxygen consumption (VO(2)). 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 PaO(2) 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. DO(2) and VO(2) were calculated as: DO(2)=cardiac output × arterial oxygen content, and VO(2)= 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 Pao(2) target, and 362 to a restrictive target. At all prespecified time points, DO(2) in MAP77 was higher compared with MAP63, with a cumulative treatment effect of 203 L (95% CI, 132-274) O(2) after 36 hours. VO(2) was higher in MAP77 after 36 hours, with a cumulative treatment effect of 21.9 L (95% CI, 5.8-38) O(2), compared with the MAP63 group. CONCLUSIONS: Targeting a MAP of 77 mm Hg resulted in an overall increase in DO(2) and a smaller increase in VO(2) compared with a MAP target of 63 mm Hg. A higher Pao(2) target did not result in any difference in DO(2) or VO(2).