An observational study in Hypothermia Following Anesthesia, sponsored by Instituto de Investigación Sanitaria de la Fundación Jiménez Díaz. Enrolling by invitation at 1 site in Spain. Open to participants aged 18 Years and older, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-09-24.
Sponsored by Instituto de Investigación Sanitaria de la Fundación Jiménez Díaz · Observational
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:
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:
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.
449 studies on the registry are indexed under Hypothermia; 54 are open to participants now.
This study's planned enrollment of 1,300 is above the median of 95 across 106 observational studies indexed under Hypothermia.
Browse Hypothermia studies →Instituto de Investigación Sanitaria de la Fundación Jiménez Díaz is the lead sponsor of 76 studies on the registry; 27 are open to participants now.
Counted across the registry records on this site, refreshed daily.
The study population will consist of adult patients undergoing scheduled non-cardiac surgery under general, neuraxial, or combined anesthesia at participating public or private hospitals in Spain. Participating centers will be hospitals with operating rooms equipped with active patient warming systems and availability of core temperature monitoring in the postoperative recovery setting.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
ASA physical status
The anaesthetists’ scale of health before surgery: I is healthy, II has a mild illness that is under control, III a severe one, IV a severe illness that is a constant threat to life. V and VI are used for the critically ill and for organ donors.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
A non-invasive zero-heat-flux temperature sensor will be used to measure core body temperature upon admission to the post-anesthesia care unit. The same temperature monitoring system will be used in all participating centers to standardize postoperative temperature measurement. The measurement does not alter routine clinical care.
Prevalence of Postoperative Hypothermia
Proportion of patients with a core body temperature below 36.0°C at admission to the post-anesthesia care unit (PACU). Core temperature will be measured using a non-invasive zero-heat-flux temperature monitoring system.
Time frame: At admission to the post-anesthesia care unit, immediately after surgery
Prevalence of Preoperative Active Warming
Proportion of patients who receive active warming for at least 10 minutes before transfer to the operating room.
Time frame: During the preoperative period, before transfer to the operating room
Prevalence of Intraoperative Active Warming
Proportion of patients who receive active intraoperative warming and description of the warming method used, including forced-air warming, conductive warming, intravenous fluid warming, or irrigation fluid warming.
Time frame: From induction of anesthesia until completion of surgery
Prevalence of Intraoperative Core Temperature Monitoring
Proportion of patients who undergo intraoperative core temperature monitoring and description of the monitoring method used.
Time frame: During surgery
Risk Factors Associated With Postoperative Hypothermia
Association between patient characteristics, comorbidities, surgical and anesthetic characteristics, and perioperative temperature management practices and the occurrence of postoperative hypothermia, defined as core temperature below 36.0°C at admission to the PACU.
Time frame: Perioperative/Periprocedural
Immediate Postoperative Complications Associated With Hypothermia
Association between postoperative hypothermia and immediate postoperative complications, including shivering, hemodynamic instability requiring vasoactive drugs, new-onset perioperative arrhythmia, perioperative bleeding greater than 500 mL, and need for blood transfusion.
Time frame: Perioperative/Periprocedural
Plan to share: No — Individual participant data will not be shared because of privacy and data protection considerations. The study involves health-related information that will be collected and pseudonymized in accordance with applicable data protection regulations. Data will be used for the purposes specified in the study protocol and will not be made available for public sharing at the individual participant level.
Start is estimated for Nov 2026; primary completion for Dec 2026, 1 month later.
Of 47 non-industry observational studies under Hypothermia, half reached primary completion within 12 months of starting (the median), counting those still running; a quarter within 4 and three quarters within 50. This study's planned 1 month is below that.
Counting every sponsor, half of 48 studies reached it within 12 months; a quarter within 4 and three quarters within 50.
How these figures are worked out, and which studies are left out of them.
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Instituto de Investigación Sanitaria de la Fundación Jiménez Díaz