Effects of Active Prewarming in Perioperative Hypothermia in Adults

This study evaluates the effect of active prewarming on the frequency and duration of perioperative hypothermia. 50% of patients will receive active warming with forced-air devices prior to entering the operating room, and the other 50% will not receive any active heating measures.

Inadvertent perioperative hypothermia is defined as a body temperature below 36º C during the perioperative period. It occurs as a result of the effects of anesthetic drugs on the regulation of body temperature and exposure to a cold environment.

The main temperature loss during the perioperative period occurs during the first hour after the anesthetic induction as a result of heat redistribution from the central compartment to the peripheral compartment

The most effective strategy to prevent perioperative hypothermia is the use of forced-air warming devices. These devices are usually initiated once the patient enters the operating room. At that time, the patient has already initiated the heat loss by distributing heat from the central to the peripheral compartment to maintain body temperature.

We intend to use forced-air warming devices before the patients is transferred to the operating room in order to preserve the peripheral body temperature. This way the redistribution of heat should be avoided and, therefore, perioperative hypothermia and its harmful effects will be prevented.

Eligibility Criteria:
Inclusion Criteria:

* \> 18 years old.
* American Society of Anesthesiologists I-III.
* Undergoing surgery under general or locoregional anesthesia lasting more than 30 minutes.
* General surgery: hernias, cholecystectomies, hepatectomies, intestinal resections, pancreatoduodenectomies ...
* Traumatology and orthopedics: total / partial knee prosthesis, total / partial hip prosthesis, osteosynthesis, removal of material, arthroscopies, hallux valgus, lumbar arthrodesis ...
* Neurosurgery: lumbar arthrodesis, excision of intracranial tumors.
* Gynecology: Hysterectomies, adnexectomies, hysteroscopy ...
* Otorhinolaryngology: septoplasty, nasosinusal endoscopic surgery, tonsillectomies, adenoidectomies, thyroidectomies...
* Thoracic: Pneumonectomies and pulmonary resections, sympathectomies, thoracoscopy ...
* Urology: Bladder transurethral resection , prostate transurethral resection, nephrectomies.
* Maxillofacial: parathyroidectomies, microsurgery ...
* Ability to understand the study, give authorization and collaborate with data collection

Exclusion Criteria:

* Local anesthesia or peripheral nerve block.
* Urgent or emergent surgery.
* Cognitive impairment or lack of collaboration of any kind
* Pregnant women undergoing cesarean section.
* Diabetes Mellitus poorly controlled (HbA1c\> 6.5-7%)
* Subjects that are under treatment with drugs that interfere with thermoregulation or may cause drug-induced hyperthermia (amphetamines, barbiturates, inhaled gases ...)
* Subjects with burns, pressure ulcers and other surface disturbances that cover the heating devices
* Subjects with screening temperature \> 37.5º C.
* Subjects with fever or active infections.
* Subjects with chronic anemia who require periodic transfusions