Mode of blood pressure monitoring and morbidity after noncardiac surgery

BACKGROUND Control of blood pressure remains a key goal of peri-operative care, because hypotension is associated with adverse outcomes after surgery. OBJECTIVES We explored whether increased vigilance afforded by intra-arterial blood pressure monitoring may be associated with less morbidity after surgery. DESIGN A prospective observational cohort study. SETTING Four UK secondary care hospitals. PATIENTS A total of 4342 patients ≥45 years who underwent noncardiac surgery. METHODS We compared outcome of patients who received peri-operative intra-arterial blood pressure monitoring with those whose blood pressure was measured noninvasively. OUTCOMES The primary outcome was peri-operative myocardial injury (high-sensitivity troponin-T ≥ 15 ng l −1 within 72 h after surgery), compared between patients who received intra-arterial versus noninvasive blood pressure monitoring. Secondary outcomes were morbidity within 72 h of surgery (postoperative morbidity survey), and vasopressor and fluid therapy. Multivariable logistic regression analysis explored associations between morbidity and age, sex, location of postoperative care, mode of blood pressure/haemodynamic monitoring and Revised Cardiac Risk Index. RESULTS Intra-arterial monitoring was used in 1137/4342 (26.2%) patients. Myocardial injury occurred in 440/1137 (38.7%) patients with intra-arterial monitoring compared with 824/3205 (25.7%) with noninvasive monitoring [OR 1.82 (95% CI 1.58 to 2.11), P < 0.001]. Intra-arterial monitoring remained associated with myocardial injury when adjusted for potentially confounding variables [adjusted OR 1.56 (1.29 to 1.89), P < 0.001). The results were similar for planned ICU versus ward postoperative care. CONCLUSIONS Intra-arterial monitoring is associated with greater risk of morbidity after noncardiac surgery, after controlling for surgical and patient factors. These data provide useful insights into the design of a definitive monitoring trial.