The impact of continuous non-invasive arterial blood pressure monitoring on blood pressure stability during general anaesthesia in orthopaedic patients: A randomised trial

BACKGROUND: In patients undergoing general anaesthesia, intraoperative hypotension occurs frequently and is associated with adverse outcomes such as postoperative acute kidney failure, myocardial infarction or stroke. A history of chronic hypertension renders patients more susceptible to a decrease in blood pressure (BP) after induction of general anaesthesia. As a patient's BP is generally monitored intermittently via an upper arm cuff, there may be a delay in the detection of hypotension by the anaesthetist. OBJECTIVE: The current study investigates whether the presence of continuous BP monitoring leads to improved BP stability. DESIGN: Randomised, controlled and single-centre study. PATIENTS: A total of 160 orthopaedic patients undergoing general anaesthesia with a history of chronic hypertension. INTERVENTION: The patients were randomised to either a study group (n = 77) that received continuous non-invasive BP monitoring in addition to oscillometric intermittent monitoring, or a control group (n = 83) whose BP was monitored intermittently only. The interval for oscillometric measurements in both groups was set to 3 min. After induction of general anaesthesia, oscillometric BP values of the two groups were compared for the first hour of the procedure. Anaesthetists were blinded to the purpose of the study. MAIN OUTCOME MEASURE: BP stability and hypotensive events. RESULTS: There was no difference in baseline BP between the groups. After adjustment for multiple testing, mean arterial BP in the study group was significantly higher than in the control group at 12 and 15 min. Mean ± SD for study and control group, respectively were: 12 min, 102 ± 24 vs. 90 ± 26 mmHg (P = 0.039) and 15 min, 102 ± 21 vs. 90 ± 23 mmHg (P = 0.023). Hypotensive readings below a mean pressure of 55 mmHg occurred more often in the control group (25 vs. 7, P = 0.047). CONCLUSION: Continuous monitoring contributes to BP stability in the studied population. TRIAL REGISTRATION: NCT02519101.

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