Study of the Prevalence of Postoperative Hypothermia in Adults Undergoing Non-Cardiac Surgery in Spanish Post-Anesthesia Care Units

Overview

The prevalence of Hypothermia in Spanish Post-Anesthesia Recovery Units (in Spanish: "Prevalencia de Hipotermia en las Reanimaciones Españolas" PHRES Study) is a prospective, multicenter observational study that will evaluate how often adults develop unintended low body temperature after non-cardiac surgery in post-anesthesia recovery units in Spain. Unintended low body temperature, known as perioperative hypothermia, is a common problem after surgery and may be associated with complications such as shivering, increased bleeding, heart problems, discomfort, and delayed recovery. Although active warming devices and temperature monitoring are available in many Spanish hospitals, their use may vary between centers. The study will include adults undergoing scheduled non-cardiac surgery lasting more than 60 minutes under general, regional, or combined anesthesia. Approximately 1,334 patients from 25-30 Spanish hospitals are expected to participate. Patients will be included consecutively according to predefined eligibility criteria. The study will record information about the patient, the type and duration of surgery and anesthesia, and the measures used to prevent low body temperature before and during surgery, including active warming and temperature monitoring. On arrival in the post-anesthesia recovery unit, the patient's core body temperature will be measured using the same non-invasive temperature monitoring technology in all participating centers. The main objective is to determine the proportion of patients with a core temperature below 36°C at the time of admission to the recovery unit. The study will also investigate factors associated with postoperative hypothermia and record complications occurring shortly after surgery, such as shivering, hemodynamic instability, new-onset arrhythmias, significant bleeding, and the need for blood transfusion. This is an observational study. The study will not determine or change how patients are warmed or how their temperature is monitored during surgery. These decisions will remain the responsibility of the treating anesthesia team according to local clinical practice. The additional temperature measurement performed for the study is non-invasive and does not involve any significant additional risk to participants.

Background Unintended perioperative hypothermia, defined as a core body temperature below 36.0°C, is one of the most common complications associated with anesthesia and surgery. During the first hour after induction of anesthesia, the body's normal temperature regulation is impaired, causing heat to redistribute from the core to the peripheral tissues. Additional factors such as exposure to a cool operating room, administration of intravenous fluids, surgical duration, and the extent of the surgical procedure further increase the risk of heat loss. Postoperative hypothermia has been associated with several adverse outcomes, including shivering, patient discomfort, increased blood loss and transfusion requirements, wound infection, cardiac complications, and prolonged recovery. International guidelines recommend routine temperature monitoring and the use of active warming techniques during surgery. However, the implementation of these recommendations varies considerably between hospitals, and contemporary national data from Spain are not available. The PHRES Study has been designed to determine the current prevalence of postoperative hypothermia in Spanish post-anesthesia recovery units and to describe perioperative temperature management practices across a wide range of hospitals. Study Design PHRES is a prospective, multicenter, observational study conducted in approximately 25-30 public and private hospitals throughout Spain. The study is coordinated by Spanish anesthesiologists and will recruit approximately 1,334 adult patients undergoing elective non-cardiac surgery. Because this is an observational study, no aspect of routine clinical care will be modified. Decisions regarding prewarming, intraoperative active warming, temperature monitoring, fluid warming, anesthetic technique, and postoperative management will remain entirely under the responsibility of the treating anesthesia team according to local clinical practice. Participants Eligible participants are adults aged 18 years or older undergoing scheduled non-cardiac surgery with an expected anesthesia duration of more than 60 minutes. Patients receiving general anesthesia, neuraxial anesthesia, or combined techniques may be included. Patients with suspected infection, those undergoing surgery under regional anesthesia with sedation alone, or those unable to provide informed consent will be excluded. Participants will be enrolled consecutively during predefined recruitment periods in each participating center in order to minimize selection bias. Study Procedures After written informed consent is obtained, demographic and clinical information will be collected from the medical record and anesthesia chart. Information recorded will include: * Patient characteristics and comorbidities. * Type and duration of anesthesia and surgery. * Surgical specialty and operative approach. * Use of preoperative and intraoperative active warming. * Methods of intraoperative core temperature monitoring. * Administration of fluids, vasoactive drugs, and irrigation fluids. Upon admission to the post-anesthesia care unit (PACU), the patient's core temperature will be measured using the same non-invasive zero-heat-flux temperature monitoring system in all participating centers. Standardizing the postoperative temperature measurement minimizes variability related to different thermometry methods and allows reliable comparison between hospitals. The study will also record immediate postoperative events including shivering, hemodynamic instability requiring vasoactive support, new-onset arrhythmias, significant bleeding, and the need for blood transfusion. Study Objectives The primary objective is to estimate the prevalence of postoperative hypothermia, defined as a core temperature below 36.0°C at admission to the PACU. Secondary objectives are: * To describe the use of prewarming, active intraoperative warming, and core temperature monitoring in Spanish hospitals. * To identify patient- and procedure-related risk factors associated with postoperative hypothermia. * To evaluate the relationship between postoperative hypothermia and immediate postoperative complications. Importance of the Study This study will provide the first large contemporary national estimate of postoperative hypothermia in Spain using a standardized method for postoperative core temperature measurement. The results are expected to identify opportunities to improve perioperative temperature management, promote adherence to evidence-based warming strategies, and ultimately improve patient safety and recovery after surgery.