Relevance of age and hypertension for blood pressure targets in comatose survivors of cardiac arrest: A BOX-Trial sub-study

Aims: To assess whether the optimal mean arterial blood pressure (MAP) target after out-of-hospital cardiac arrest (OHCA) is influenced by age and a history of arterial hypertension. Methods and results: A post hoc analysis of data from the Blood Pressure and Oxygenation Targets in Post Resuscitation Care trial. The trial included 789 comatose patients randomized to a MAP target of 63 or 77 mmHg. The primary outcome of this sub-study was 1-year all-cause mortality. Cox proportional hazards regression and restricted cubic splines were used to examine whether prevalent hypertension and age modified the effect of low vs. high MAP target on all-cause mortality. Of the 789 patients randomized, 393 were assigned to a high MAP target, and 396 to a low MAP target. Groups were well-balanced for mean age (high MAP target 63 ± 13 years vs. low 62 ± 14 years) and hypertension (45 vs. 47%, respectively). At 1 year, the primary outcome occurred in 143 patients (36%) with a high MAP target and 138 (35%) with a low MAP target. The risk of the primary outcome increased linearly with increasing age (P < 0.001). The effect of a high vs. low MAP target on the primary outcome was modified by age when tested continuously, potentially favouring a low MAP target in younger patients (P for interaction = 0.03). Prevalent hypertension did not modify the effect of a high vs. low MAP target on the primary outcome (P for interaction = 0.67). Conclusion: Among patients resuscitated after OHCA, older patients and those with a history of hypertension did not benefit from a high MAP target.