Raymond R. Townsend, MD, Researcher Physician at University of Pennsylvania. In this video, he speaks about the SPYRAL HTN-ON MED Study.
Intraoperative hypothermia of moderate severity causes myocardial damage, surgical site infections, and blood loss. It is unknown whether forceful warming to a true normothermic temperature approaching 37°C improves outcomes. We wanted to see if intensive intraoperative warming minimizes severe perioperative problems.
During non-cardiac surgery, patients were randomly assigned (1:1) to either aggressive warming to a target core temperature of 37°C (aggressively warmed group) or routine thermal management to a target of 35°C (routine thermal management group) at 12 sites in China and the Cleveland Clinic in the United States. Randomization was stratified by location, with randomly sized blocks generated by a computer. Eligible patients (aged 45 years) had at least one cardiovascular risk factor, were scheduled for inpatient non-cardiac surgery lasting 2–6 hours under general anaesthesia, and had at least half of the anterior skin surface available for warming. Patients on dialysis and those with a BMI more than 30 kg/m2 were excluded. In the modified intention-to-treat population, the primary outcome was a composite of myocardial damage (troponin increase, probably of ischemic origin), non-fatal cardiac arrest, and all-cause mortality within 30 days of surgery. NCT03111875, this study is registered with ClinicalTrials.gov.
5056 participants were enrolled between March 27, 2017 and March 16, 2021, with 5013 included in the intention-to-treat population (2507 in the aggressively warmed group and 2506 in the routine thermal management group). Patients allocated to intense warming had a mean final intraoperative core temperature of 371°C (SD 03), whereas patients assigned to regular thermal care had a mean final intraoperative core temperature of 356°C (SD 03). At least one of the primary outcome components (myocardial damage following non-cardiac surgery, cardiac arrest, or mortality) occurred in 246 (99% of 2497) of the forcefully warmed patients and in 239 (96% of 2490) of the normal thermal care patients. The calculated common impact relative risk of active versus routine thermal management was 104 (95 percent CI 087–124; p=069). There were 39 adverse events (17 of which were significant) in patients assigned to intense warming and 54 in those assigned to normal thermal care (30 of which were serious). One major adverse event in a patient who had been intensively warmed was thought to be connected to thermal management.
The 30-day composite of main cardiovascular events did not differ substantially between participants randomly assigned to 355°C or 37°C. There was no evidence that any significant consequence differed throughout a 15°C range from extremely mild hypothermia to full normothermia. In surgical patients, maintaining a core temperature of at least 355°C appears to be sufficient.