Personalized intraoperative arterial pressure management and mitochondrial oxygen tension in patients having major non-cardiac surgery: a pilot substudy of the IMPROVE trial.

The "Cellular Oxygen METabolism" (COMET) system (Photonics Healthcare, Utrecht, The Netherlands) non-invasively measures mitochondrial oxygen tension (mitoPO) in the skin. The effects of general anesthesia and major non-cardiac surgery on mitoPO remain unknown. In this pre-planned pilot substudy of the "Intraoperative blood pressure Management based on the individual blood PRessure profile: impact on postOperatiVE organ function" (IMPROVE) trial, we measured mitoPO from induction of general anesthesia until the end of surgery in 19 major non-cardiac surgery patients (10 assigned to personalized and 9 to routine intraoperative arterial pressure management). In the overall cohort, the median (25th to 75th percentile) preoperative awake mitoPO was 63 (53 to 82) mmHg and mitoPO after induction of general anesthesia was 42 (35 to 59) mmHg. The intraoperative average mitoPO was 39 (30 to 50) mmHg. Thirteen patients (68%) had intraoperative mitoPO values below 20 mmHg and the median percentage of surgical time with mitoPO < 20 mmHg was 17 (0 to 31)%. MitoPO was weakly correlated with mean arterial pressure (repeated measures correlation (r(n); r(984) = 0.26, 95% confidence interval 0.20 to 0.32; P < 0.001), but not meaningfully with heart rate (r(984) = -0.05, 95% confidence interval -0.11 to 0.01; P = 0.117). There was no important difference in intraoperative average mitoPO between patients assigned to personalized or to routine intraoperative arterial pressure management (P = 0.653). MitoPO under general anesthesia was about a quarter lower than preoperative awake mitoPO, substantially fluctuated during major non-cardiac surgery, and transiently decreased below 20 mmHg in about two-thirds of the patients. Personalized - compared to routine - intraoperative arterial pressure management did not increase intraoperative mitoPO. Whether intraoperative decreases in mitoPO are clinically meaningful warrants further investigation.