Intraoperative warming during noncardiac surgery does not impact CV, other outcomes
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WASHINGTON — Aggressive intraoperative warming during major noncardiac surgery did not reduce myocardial injury, site infections, transfusion requirement or hospitalization stay vs. routine temperature management, a speaker reported.
Intraoperative temperatures as low as 35.5°C and no warming appear to be safe for major noncardiac surgery, according to data from the PROTECT trial presented at the American College of Cardiology Scientific Session.
“Anesthetics profoundly impair thermoregulatory control. Consequently, nearly all unwarmed surgical patients become hypothermic,” Daniel I. Sessler, MD, Michael Cudahy professor and chair of the department of outcomes research at Cleveland Clinic, said during the presentation. “Small trials, mostly dating back a quarter of a century, report that mild hypothermia during surgery increases morbid cardiovascular outcomes, promotes surgical site infections and increases bleeding and transfusions. Hypothermia also decreases drug metabolism, prolongs recovery and causes shivering and thermal discomfort. Based on these data, warming has become routine in high-income countries.”
Sessler said current guidelines specify a target temperature of 36°C, which is based on no evidence, and a slightly lower or higher temperature may be preferable.
Therefore, researchers in the department of outcomes research at Cleveland Clinic investigated whether there were any differences in outcomes after major noncardiac surgery with aggressive intraoperative warming compared with routine thermal management at 13 sites, mostly in China.
The PROTECT trial included 5,056 patients undergoing major noncardiac inpatient surgery with general anesthesia expected to last more than 2 hours who were aged at least 45 years with at least one cardiac risk factor. Approximately 52% of surgical procedures were laparoscopic and 25% were open abdominal.
Participants (mean age, 67 years; 32% women) were randomly assigned to routine thermal management with a target temperature of 35.5°C or aggressive thermal management with a target of 37°C.
Routine care included no prewarming or fluid warming and forced-air cover if core temperature dropped below 35.5°C. Aggressive warming included 30 minutes of forced-air prewarming, warmed IV fluids and two intraoperative forced-air warming covers.
Troponin was measured preoperatively and up to 3 days postoperatively.
The primary outcome was a composite of myocardial injury, cardiac arrest and death at 30 days. Secondary outcomes included deep or organ-space surgical site infections, red cell transfusions, hospital stay and hospital readmission at 30 days.
A primary outcome event occurred in 9.9% of the aggressive warming group and 9.6% of the no-warming group (estimated common effect RR = 1.04; 95% CI, 0.87-1.24; P = .69), and the results did not change after imputation of missing outcomes (common effect RR = 1.1; 95% CI, 0.92-1.32; P = .27).
The final analysis was only powered to assess for myocardial injury, and the researchers reported they observed no significant difference between intraoperative warming or routine thermal management (aggressive warming, 9.4%; no warming, 9%; common effect RR = 1.05; 95% CI, 0.85-1.3; P = .57).
Additionally, researchers found no association between fewer surgical site infections, transfusion requirement, hospital stay or readmissions compared with routine thermal management.
There were 17 serious adverse events in the aggressive warming group and 30 in the no warming group, and one serious event in the aggressive warming group was determined to be possibly related to temperature management, according to the researchers.
“We conclude that randomization to 37°C vs. 35.5°C intraoperative core temperature does not reduce cardiovascular composite, although it’s really only powered for myocardial injury. Aggressive warming also did not reduce surgical site infections, transfusion requirements, the duration of hospitalization or readmissions,” Sessler said during the presentation. “Intraoperative temperatures as low as 35.5°C appear to be safe.”
The findings were simultaneously published in The Lancet.
Reference:
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Sessler DI, et al. Late-Breaking Clinical Trials IV. Presented at: American College of Cardiology Scientific Session; April 2-4, 2022; Washington, D.C. (hybrid meeting).
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