LAUSR

Objective There is inadequate information about the values of many intraoperative physiological measurements that are associated with improved outcomes after surgery. The purpose of this observational study is to investigate the optimal physiological ranges during major spine surgery. Setting A teaching hospital in the USA. Participants A convenience sample of 102 patients receiving major posterior spine surgery with multilevel spinal fusion in a prone position. Methods Physiological variables, including but not limited to mean arterial pressure (MAP) and cerebral and somatic tissue oxygen saturation (SctO2/SstO2), were recorded. The results of these measurements were associated with length of hospital stay and composite complication data and were analysed based on thresholds (ie, a cut-off value for optimal and suboptimal physiology) and the area under the curve (AUC) values. The AUC values were measured as the area enclosed by the actual tracing and the threshold. The outcomes were dichotomised into above-average and below-average (ie, improved) categories. Results Analyses based on thresholds identified the following variables associated with above-average outcomes: MAP <60 mm Hg, temperature <35°C, heart rate >90 beats per minute (bpm), SctO2 <60% and SstO2 >80%. Analyses based on AUC values identified the following as associated with above-average outcomes: MAP <70 and >100 mm Hg, temperature <36°C, heart rate >90 bpm, tidal volume (based on ideal body weight)<6 mL/kg, tidal volume (based on actual body weight) >10 mL/kg and peak airway pressure <15 cmH2O. Conclusion The following physiological ranges are associated with improved outcomes (ie, shorter hospitalisation and fewer complications) during major spine surgery: MAP of 70–100 mm Hg, temperature ≥36°C, heart rate <90 bpm, tidal volume based on ideal body weight >6 mL/kg, SctO2 >60% and SstO2 <80%.