Relevance of age and hypertension for blood pressure targets in comatose survivors of cardiac arrest

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Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): The Novo Nordisk Foundation. Background Baseline arterial blood pressure (BP) is influenced by age. Therefore, age and previous hypertension may alter the appropriate BP target after out-of-hospital cardiac arrest (OHCA). Purpose To examine whether the optimal BP target after OHCA is affected by age and a history of arterial hypertension. Methods The Blood Pressure and Oxygenation Targets in Post Resuscitation Care (BOX) trial was a randomized, controlled, double-blind trial comprising 789 comatose patients ≥18 years of age, resuscitated after OHCA of presumed cardiac cause. Patients were randomized to a mean arterial BP target of either 63 mm Hg (low BP target group) or 77 mm Hg (high BP target group). The primary outcome was a composite of death from any cause or hospital discharge with severe cerebral disability within one year. The relationship between age or prevalent hypertension and clinical outcomes was evaluated using Cox proportional-hazards regression. Age was stratified into quartiles. We further determined if the effects of BP target varied across the age spectrum (and according to prevalent hypertension). Results Three-hundred and ninety-three patients were assigned to the high BP target group and 396 to the low BP target group. In all, 204 (25.9%), 201 (25.5%), 186 (23.6%), and 198 (25.1%) were ≤54, 55-64, 65-72, and ≥73 years. Mean age was similar between the two study groups (high BP target 63 ± 13 years versus low BP target 62 ± 14 years; P = 0.60). A total of 176 (45%) patients in the high BP target group and 186 (47%) patients in the low BP target group had known hypertension. At 90 days, 133 patients (34%) in the high BP target group and 127 patients (32%) in the low BP target group had experienced the primary outcome. The risk of the primary outcome increased with higher age (Figure 1). Hazard ratios of the primary outcome according to BP targets within each age quartile (with low BP target as reference) were as follows: ≤54: 1.71; 95% confidence interval [CI], 0.99 to 2.95; P = 0.054, 55-64: 0.92; 95% CI, 0.57 to 1.49; P = 0.73, 65-72: 1.12; 95% CI, 0.73 to 1.74; P = 0.59 and ≥73: 0.88; 95% CI, 0.60 to 1.27; P = 0.48 (Figure 2). The hazard ratio of the primary outcome was 0.99; 95% CI, 0.72 to 1.37; P = 0.97 in patients without prevalent hypertension, and 1.14; 95% CI, 0.83 to 1.54; P = 0.42 in patients with prevalent hypertension. Conclusions In patients resuscitated after OHCA, there was a significant association between age and the primary composite outcome of death, severe disability, or coma. The effect of BP target on the primary outcome did not appear to differ according to age groups or prevalent hypertension. Therefore, age and prevalent hypertension should not influence the choice of BP targets after OHCA.