Associations between intraoperative and post-anesthesia care unit hypotension and surgical ward hypotension.

Study Objective: To test whether patients who experience hypotension in the post-anesthesia care unit or during surgery are most likely to experience hypotension on surgical wards.

Design: A prediction study using data from two randomized controlled trials.

Setting: Operating room, post-anesthesia care unit, and surgical ward.

Patients: 550 adult patients having abdominal surgery with ASA physical status I-IV.

Interventions: Blood pressure measurement per routine intraoperatively, and with continuous non-invasive monitoring postoperatively.

Measurements: The primary predictors were minimum mean arterial pressure (<60, <65, <70 and < 80 mmHg) and minimum systolic blood pressure (<70, <75, <80, <85 mmHg) in the post-anesthesia care unit. The secondary predictors were intraoperative minimum blood pressures with the same thresholds as the primary ones. Our outcome was ward hypotension defined as mean pressure < 70 mmHg or systolic pressure < 85 mmHg. A threshold was considered clinically useful if both sensitivity and specificity exceeded 0.75.

Main Results: Minimum mean and systolic pressures in the post-anesthesia care unit similarly predicted ward mean or systolic hypotension, with the areas under the curves near 0.74. The best performing threshold was mean pressure < 80 mmHg in the post-anesthesia care unit which had a sensitivity of 0.41 (95% confidence interval [CI], 0.35, 0.47) and specificity of 0.91 (95% CI, 0.87, 0.94) for ward mean pressure < 70 mmHg and a sensitivity of 0.44 (95% CI, 0.37, 0.51) and specificity of 0.88 (95% CI, 0.84, 0.91) for ward systolic pressure < 85 mmHg. The areas under the curves using intraoperative hypotension to predict ward hypotension were roughly similar at about 0.60, with correspondingly low sensitivity and specificity.

Conclusions: Intraoperative hypotension poorly predicted ward hypotension. Pressures in the post-anesthesia care unit were more predictive, but the combination of sensitivity and specificity remained poor. Unless far better predictors are identified, all surgical inpatients should be considered at risk for postoperative hypotension.