Validation and Clinical Evaluation of a Method for Double-Blinded Blood Pressure Target Investigation in Intensive Care Medicine.

OBJECTIVES: No double-blinded clinical trials have investigated optimal mean arterial pressure targets in the ICU. The aim of this study was to develop and validate a method for blinded investigation of mean arterial pressure targets in patients monitored with arterial catheter in the ICU.

DESIGN: Prospective observational study (substudy A) and prospective, randomized, controlled clinical study (substudy B).

SETTING: ICU, Department of Cardiology, University Hospital of Copenhagen, Rigshospitalet, Copenhagen, Denmark.

PATIENTS: Adult patients resuscitated from out-of-hospital cardiac arrest.

INTERVENTIONS: Standard blood pressure measuring modules were offset to display 10% lower or higher blood pressure values. We then: 1) confirmed this modification in vivo by comparing offset to standard modules in 22 patients admitted to the ICU. Thereafter we 2) verified the method in two randomized, clinical trials, each including 50 out-of-hospital cardiac arrest patients, where the offset of the blood pressure module was blinded to the treating staff.

MEASUREMENTS AND MAIN RESULTS: Substudy A showed that the expected separation of blood pressure measurements was achieved with an excellent correlation of the offset and standard modules (R = 0.997). Bland-Altman plots showed no bias of modified modules over a clinically relevant range of mean arterial pressure. The primary endpoint of the clinical trials was between-group difference of norepinephrine dose needed to achieve target mean arterial pressure. Trial 1 aimed at a 10% difference between groups in mean arterial pressure (targets: 65 and 72 mm Hg, respectively) and demonstrated a separation of 5 ± 1 mm Hg (p < 0.001). The difference in norepinephrine dose was not significantly different (0.03 ± 0.03 µg/kg/min; p = 0.42). Trial 2 aimed at a 20% difference between groups in mean arterial pressure (targets: 63 and 77 mm Hg, respectively). Separation was 12 ± 1 mm Hg (p < 0.01) in mean arterial pressure and 0.07 ± 0.03 µg/kg/min (p < 0.01) in norepinephrine dose.

CONCLUSIONS: The present method is feasible and robust and provides a platform for double-blinded comparison of mean arterial pressure targets in critically ill patients.