By Naveed Saleh, MD, MS

Vienna—Underbody-type blankets may outperform other types of warming blankets starting around 100 minutes after induction of anesthesia, according to one study.

“Underbody blankets, together with surgical draping, enable efficient convection of airflow over the body,” said study author Shigekazu Sugino, MD, PhD, a research associate in the Department of Anesthesiology and Perioperative Medicine at Tohoku University School of Medicine, in Sendai, Japan. “This warmed tent produces a larger body surface area that can be warmed by the blanket.”

In the current study, Dr. Sugino and his team prospectively reviewed data from 20,644 patients who underwent surgery under general anesthesia during 2018. They included 10,105 patients in their final analysis, with 3,829 assigned to the underbody blanket group and 6,276 assigned to a control group. Clinical data were taken from electronic health and anesthesia records. Data were collected for each type of blanket every five minutes for a period of four hours after the induction of anesthesia.


The lead author of the study was Kunie Sato, MD, who presented the poster during the 2019 annual meeting of the European Society of Anaesthesiology. At 100 minutes after anesthesia induction, the regression coefficient was statistically significant in favor of underbody warming blankets.

Kunie Sato, MD, presents on benefits of underbody warming blankets during the 2019 annual meeting of the European Society of Anaesthesiology.

Anesthetics result in vasodilation by means of direct peripheral action. This process yields an initial rapid decrease in core temperature, and produces core-to-peripheral heat redistribution. Forced-air warming is necessary during the first three hours after anesthesia induction due to core-to-peripheral redistribution of body heat, which causes a rapid drop in temperature immediately after the start of anesthesia. Although underbody-type blankets have recently come to market, their current utility is unclear.


“Gaining a deeper understanding of temperature redistribution and how to maintain normothermia during surgery and anesthesia is an important subject, as there are clinical implications for patient outcomes tied to this metric,” said Scott Falk, MD, an associate professor of anesthesiology and critical care at Penn Medicine, in Philadelphia. “Given the data presented, underbody forced-air warming devices may have some advantage over overbody forced-air devices for prolonged procedures—those procedures lasting over 100 minutes. This study is unique in that it uses mathematical modeling on a large population to determine warmer effectiveness. It would have been beneficial to also relate the findings to significant outcomes, such as temperature postoperatively, patient length of stay and infection rates. Hopefully in the future, we will be able to delineate exactly which populations would benefit from this technology so it can be applied in a directed way.”

Drs. Sugino and Sato are looking forward to performing a prospective study in the near future. “We shall verify the usefulness of the underblanket in a prospective study. Actually, we are conducting it now,” Dr. Sugino said.