imageResearch showing that more than 7% of thoracic surgery patients experience postoperative hypothermia despite active warming is raising questions about the appropriateness of current criteria for the hypothermia quality measure.
The study, led by David Bronheim, MD, associate professor in the Department of Anesthesiology at Icahn School of Medicine at Mount Sinai, in New York City, was a retrospective analysis of medical records from 316 thoracic surgery patients treated at the institution between May 2011 and February 2012. All of the patients had been covered perioperatively with a forced–warm air blanket.
Despite active warming, Dr. Bronheim’s team found 7.2% of patients (23 of 316) experienced postoperative hypothermia. These patients were significantly more likely to die within 30 days of surgery than patients whose temperature remained normal: 8.7% (two of 23) versus 0.7% (two of 293), respectively (P=0.028).
Richard Dutton, MD, executive director of the Anesthesia Quality Institute, in Park Ridge, Ill., said the results should prompt the Centers for Medicare & Medicaid Services (CMS) to revise its Physician Quality Reporting System (PQRS; formerly the Physician Quality Reporting Initiative) hypothermia quality measure.
The current hypothermia quality measure from CMS specifies that only one of two conditions must be met in surgical patients receiving more than one hour of general anesthesia: normothermia maintenance during the perioperative period or simply covering the patient with a forced-air warming blanket.
“Documented forced-air warming is a process measure, not an outcome measure,” said Dr. Dutton, who was not involved in the study. “As this study shows, some patients still get cold despite active forced-air warming. In these individuals, we need to go beyond forced-air warming blankets and use other warming approaches.”
Dr. Dutton, who also is a member of the American Society of Anesthesiologists’ Committee on Performance and Outcomes Measurement (CPOM), noted that the current PQRS criteria were based on criteria submitted by CPOM in 2009 and represented “the best compromise between the known science and the ability to measure performance.”
“With limited knowledge of the exact link between temperature and outcome, the criteria specified a performance threshold as well as the ability to meet the measure through good faith efforts to support normothermia,” he explained.

Why Temperature Matters

Clinical trials have shown that hypothermia increases morbidity, including:
image
  • Adverse myocardial outcomes
  • Increased surgical wound infection risk
  • Increased blood loss and transfusion requirements
  • Prolonged recovery and length of stay
  • Coagulopathy
However, in light of evidence that has emerged since then that has shown that the potential harms of hypothermia are more significant than previously thought (sidebar), CPOM has submitted a new proposal asking that the measure include only actual hypothermia prevention.
“We know that our proposed definition, leaving out the process measure, may lower the rate of successful performance, but in the long term we think it will increase the quality of care,” Dr. Dutton said.
Findings Help Identify At-Risk Patients
The study helps identify thoracic surgery patients most at risk for hypothermia, said Dr. Bronheim, who presented his team’s findings at the 2013 annual meeting of the Society of Cardiovascular Anesthesiologists (abstract 96). A preliminary analysis that his team conducted showed lower body weight, shorter height and administration of lower amounts of crystalloids were independently associated with hypothermia (P<0.05 for all).
He said his team hopes to isolate the most significant risk factors with further research. They also will be examining whether hypothermia is itself a risk factor for morbidity and mortality or whether it reflects an underlying condition that places patients at risk—something the current study was not designed to discern.
“If we find that hypothermia is indeed a direct risk factor for mortality, we would have to study whether other warming techniques might improve outcomes,” Dr. Bronheim said in an interview.
Should Outcome Measures Be Absolute?
While Dr. Dutton argued for a revision of the criteria for the hypothermia quality measure, Dr. Bronheim said a hospital’s rate of hypothermia should be compared with that of other centers.
“Unlike wrong-sided surgery, for example, hypothermia is not a ‘never’ phenomenon,” Dr. Bronheim said. “I think that rather than looking at absolute rates of hypothermia, they need to be considered relative to other centers. We need a database, like the Society of Thoracic Surgeons has, where we can enter our patients’ risk factors and our hypothermia rates and see how we’re doing compared to other centers. That’s how our outcomes should be measured.”