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Extra Warming Efforts in Surgery Turn Out to Be Hot Air

April 4, 2022 By Nicole Lou, Staff Writer

WASHINGTON — Routine warming during non-cardiac surgery may be sufficient, as there was no significant difference in temperature-related procedural complications among patients kept closer to normothermia in the large PROTECT trial presented here.

Between groups randomized to aggressive warming and routine thermal management — targeting intraoperative core temperatures of 98.6°F (37°C) and 95.9°F (35.5°C), respectively — rates of combined myocardial injury, non-fatal cardiac arrest, and all-cause mortality were similar at 30 days (9.9% vs 9.6%; RR 1.04, 95% CI 0.87-1.24).

There were no between-group differences in surgical site infection, hospital readmissions, or need for transfusion, reported Daniel Sessler, MD, an anesthesiologist at the Cleveland Clinic in Ohio, during a late-breaking trial session at the American College of Cardiology (ACC) meeting.

Results of PROTECT, conducted largely in China and published in full in The Lancet, suggest that surgeons don’t need to take core temperatures higher than usual to avoid hypothermia-related complications in surgical patients.

“The good news is this study definitively shows that we don’t need go to that extra warming effort in non-cardiac surgical cases … Staying no less than 35.5°C is probably safe,” commented James McClurken, MD, a cardiac surgeon at Doylestown Health in Doylestown, Pennsylvania, during an ACC press conference.

This is a temperature that is relatively easy to maintain, whereas getting patients to 37°C is not trivial: in PROTECT, “aggressive warming” comprised pre-warming with a full-body forced-air cover for 30 minutes before induction of anesthesia, followed by the use of two forced-air covers during surgery.

McClurken and Sessler both warned against warming the room itself in order to warm the patient. “If you warm [the room] enough to keep the patient warm, everyone else in the room will be absolutely miserable,” Sessler said. “You don’t want the patient to have ill effects from the team having ill effects,” McClurken added.

The PROTECT trial was conducted at 12 sites in China plus Sessler’s institution, the Cleveland Clinic. People requiring dialysis and those with BMIs over 30 were excluded.

Participants included 5,013 people (mean age 67; two-thirds were men) randomized to warming to 37°C (“aggressive warming”) or 35.5°C (“routine thermal management”) during inpatient non-cardiac surgery.

Baseline characteristics were similar between groups. Over half underwent laparoscopic procedures, about a quarter had open abdominal operations, and the rest had a mix of orthopedic, neurosurgical, urological, and other surgeries.

There were 39 adverse events (AEs), including 17 serious adverse events (SAEs) and 54 AEs, including 30 SAEs, in the routine warming arm. One SAE, a case of fever (without evidence of infection), was ruled to be possibly related to aggressive warming.

Sessler’s group acknowledged limitations, such as nearly all enrolled patients were Chinese, few had orthopedic or vascular surgery, and all had general anesthesia.

“As such, results might differ in other populations, including patients with obesity, those having emergency surgery, or those at greater cardiovascular risk than patients enrolled in PROTECT,” the authors wrote.

Nevertheless, the trial suggests that guidelines are wrong about thermal management, according to an accompanying editorial by Flavia Borges, MD, PhD, and Jessica Spence, MD, PhD, both of the Population Health Research Institute at McMaster University in Hamilton, Ontario.

“To ensure that [anesthesia] and perioperative care continue to evolve in response to emerging research, best practice statements need to acknowledge uncertainties in the body of evidence and, rather than make recommendations on the basis of insufficient evidence, call for large studies to address these questions of utmost importance to patients,” the editorialists wrote.