Intraoperative Core Temperature Patterns, Transfusion Requirement, and Hospital Duration in Patients Warmed with Forced Air

TLDR

Core temperature patterns in patients warmed with forced air are poorly characterized, and the impact of transient, mild intraoperative hypothermia on adverse outcomes remains unknown. The study evaluated esophageal core temperatures in 58,814 adults undergoing >60‑minute surgery while being warmed with forced air. The authors analyzed temperature data from this cohort, assessing independent associations between hypothermic exposure and transfusion requirement and hospitalization duration, noting a drop in core temperature during the first hour followed by a gradual rise thereafter. In this cohort, the mean lowest core temperature was 35.7 °C; 64 % of patients fell below 36 °C within 45 min and 29 % below 35.5 °C, with nearly half remaining under 36 °C for over an hour and 20 % under 35.5 °C for over an hour; hypothermia was independently linked to higher transfusion rates and a modest increase in hospital stay, confirming its routine occurrence despite active warming.

Abstract

Core temperature patterns in patients warmed with forced air remain poorly characterized. Also unknown is the extent to which transient and mild intraoperative hypothermia contributes to adverse outcomes in broad populations.We evaluated esophageal (core) temperatures in 58,814 adults having surgery lasting >60 min who were warmed with forced air. Independent associations between hypothermic exposure and transfusion requirement and duration of hospitalization were evaluated.In every percentile subgroup, core temperature decreased during the first hour and subsequently increased. The mean lowest core temperature during the first hour was 35.7 ± 0.6°C. Sixty-four percent of the patients reached a core temperature threshold of <36°C 45 min after induction; 29% reached a core temperature threshold of <35.5°C. Nearly half the patients had continuous core temperatures <36°C for more than an hour, and 20% of the patients were <35.5°C for more than an hour. Twenty percent of patients had continuous core temperatures <36°C for more than 2 h, and 8% of the patients were below 35.5°C for more than 2 h. Hypothermia was independently associated with both transfusions and duration of hospitalization, although the prolongation of hospitalization was small.Even in actively warmed patients, hypothermia is routine during the first hour of anesthesia. Thereafter, average core temperatures progressively increase. Nonetheless, intraoperative hypothermia was common, and often prolonged. Hypothermia was associated with increased transfusion requirement, which is consistent with numerous randomized trials.