2.1. Procedures, Randomization and Interventions
tremors
BLIND
In the pre-assessment clinic, subjects were informed of the study and offered participation. For patients accepting participation and signing written consent, we used a block randomization schedule generated by the Epidat v4.1 (Consellería de Sanidade, Xunta de Galicia, Spain) program and placed in sealed envelopes. On the day of surgery, patients were randomly assigned to one of the study groups after opening the envelopes. Due to the nature of the intervention, it was not possible to blind patients to their allocation. For patients allocated to the intervention, active prewarming was initiated as soon as the patient arrived in the pre-anesthesia room with a preoperative hot air blanket (“3M™ Bair Hugger™ Preoperative Blanket”, St. Paul, MN, USA) and a hot air heating unit (“3M™ Bair Hugger™ Warming Unit”, St. Paul, MN, USA) initially set at 43 °C. If the patient felt overheated, the warming device was lowered as tolerated. In the control group, no prewarming was carried out and patients were kept in their gowns and leggings. Core body temperature was monitored in both groups using the Zero Heat Flux principle (“3M SpotOn™ Monitoring system”, St. Paul, MN, USA). The body temperature was recorded every 5 min in the pre-anesthesia room, during the intraoperative period and on arrival in the recovery room or in the ICU. In the pre-anesthesia room, patients did not receive any drugs nor receive intravenous fluid infusion, apart from a very slow drip of intravenous crystalloids to ensure the patency of the cannula. This choice was made to avoid interference from exogenous fluid on patient temperature.In the operating theatre, the attending anesthesiologist was aware of the group allocation for each patient. Although anesthetic drugs and also adjuvants commonly used in anesthesia practice (analgesics, anxiolytics, etc.) affect thermoregulation and affects also the defense mechanisms such as tremors, we opted for a pragmatic approach. Hence, in this RCT we left the attending anesthesiologist free to decide on the drugs for the anesthesiology conduction. Regarding the approach to warming during the intraoperative period, participants in both groups were actively warmed following a local protocol [