Comparison of intraoperative arterial blood pressure lability during general anaesthesia in masked, uncontrolled hypertensive and adequately controlled hypertensive patients: a prospective observational study

Introduction
Hypertensive patients are known to have increased perioperative arterial blood pressure (BP) lability, which is related to cardiovascular events. Masked uncontrolled hypertensive patients are at high cardiovascular risk. This study aimed to compare BP lability during general anaesthesia in treated hypertensive patients with normal clinic BP, between masked uncontrolled hypertension and adequately controlled hypertension.

Material and methods
Forty-three patients with apparently controlled BP were initially enrolled in this prospective observational study. Home BP was monitored and patients classified into diagnostic groups. Perioperative BP profiles were recorded from before anaesthesia induction until discharge from the recovery room. BP lability was assessed using 3 methods: (1) out-of-range probability, (2) standard deviation (SD) and variance (VAR), and (3) mean and time-averaged absolute change in BP from one measurement to the next (ARV and TARV).

Results
Sixteen masked hypertensive and 21 adequately controlled hypertensive patients were analysed. The masked group had higher of BP lability [95% CI] as measured by SD than the adequately controlled group during intraoperative and postoperative periods (SBP-SD, intraoperative 17.97 [15.33, 20.60] vs. 13.528 [11.22, 15.82], P = 0.014; postoperative 10.40 [7.65, 13.16] vs. 5.49 [2.96, 8.02], P = 0.012). MAP-SD, intraoperative 12.35 [10.70, 13.99] vs. 9.66 [8.22, 11.10], P = 0.017; postoperative 7.21 [5.05, 9,38] vs. 4.06 [2.09, 6.05], P = 0.037). ARV and TARV also revealed higher intraoperative SBP lability; non-time-averaged (mmHg) 12.40 [10.43, 14.37] vs. 9.50 [7.78, 11.22], P = 0.031 and time-averaged (mmHg min–1) 2.35 [1.95, 2,74] vs. 1.82 [1.49, 2.16], P = 0.047).

Conclusions
Masked uncontrolled hypertensive patients had significantly higher BP lability in SBP and MAP during the intraoperative and immediate postoperative periods.