Abstract】Objective To understand the many factors that cause a decrease in body temperature during anesthesia surgery in the elderly and the complications arising from hypothermia. Methods Forty elderly patients were continuously monitored for body temperature and other vital signs from the time they entered the operating room until the end of surgery. Results The process of anesthesia operation, anesthetic drugs, operation time, intraoperative blood transfusion, and body cavity flushing caused a decrease in body temperature. There was a correlation between postoperative hypothermia and postoperative complications. Conclusion Intraoperative hypothermia is very common in elderly people, and some measures are necessary to maintain a constant intraoperative body temperature. Keywords: elderly people: during anesthesia surgery; decreased body temperature The phenomenon of decreased body temperature during anesthesia surgery is gaining attention. The central temperature below 35 degrees is generally referred to as hypothermia in clinical practice…. The incidence of postoperative hypothermia is high and may result in related complications due to the reduced thermoregulatory function in the elderly. This paper reports the decrease in body temperature during anesthesia surgery and postoperative complications in elderly surgical patients in our hospital in recent years, and discusses the factors of decreased body temperature during anesthesia surgery and the relationship with postoperative complications. Materials and methods Clinical data: 40 elective surgery patients, 30 males and 10 females, ASA grade II-III, mean age 74.95±8.12 years, 7 cases of thoracic surgery, 17 cases of middle and upper abdominal surgery, 13 cases of lower abdominal surgery, and 3 cases of lower limb surgery. There were 25 cases of epidural anesthesia and 15 cases of combined general anesthesia with epidural. The patients had stable function of cardiovascular system and respiratory system before surgery. METHODS: Pre-anesthesia medication was administered, Sulfanilamide 0.06-0.08 mg/kg, intramuscularly half an hour before surgery. After entering the operating room, EKG, NIBP, SP02 and esophageal body temperature were continuously monitored using a DATEX monitor. Epidural anesthesia: At the appropriate segmental selection, an epidural puncture is performed to place the tube, and the local anesthetic is 1.73% lidocaine carbonate or 1.6% lidocaine + 0.2% cocaine, and the local anesthetic is gradually injected through the epidural catheter to a satisfactory level. The lower abdomen and lower extremity sites can be operated under this anesthesia. Combined endotracheal anesthesia is required for thoracic and upper abdominal surgery: 1 to 2ug/kg of fentanyl + 0.3mg/kg of ethamiprid + 0.5 to 0.75mg/kg of carnosine to induce intubation followed by a combination of isoproterenol, fentanyl, isoflurane by static inhalation, and intramuscular relaxants by interrogation. As a result, the body temperature of the elderly in this group decreased during anesthesia and surgery. Four patients in this group had an operation time of more than 4 hours, postoperative body temperature below 35°C, delayed awakening, three cases of postoperative complications of pulmonary infection, and one case of stroke. Discussion In recent years, the medical community has paid great attention to the reduction of body temperature during anesthesia surgery. Postoperative shivering caused by hypothermia increases oxygen consumption and wound bleeding, induces arrhythmia and myocardial infarction; hypothermia prolongs drug action and delays awakening; hypothermia weakens immune function…, decreases the patient’s resistance to respiratory system and wound infection, and prolongs the patient’s hospital stay. The elderly are particularly prone to postoperative hypothermia because of the reduced function of organs and the decreased thermoregulatory ability of the body, while the proportion of elderly surgical patients with combined cardiovascular disease and pulmonary decompensation is higher than other age groups, and the complications caused by hypothermia are more frequent and serious. Therefore, the causes of hypothermia in elderly patients during anesthesia surgery and its prevention methods are worth exploring. Preoperative medication reduces muscle tone in the patient’s extremities, vasodilation, and heat distribution through the skin. Elderly people have thin skin and poor thermoregulation. If anesthesia is performed with part of the torso exposed in an environment of 2l-26°C, the patient is often in a critical state of hypothermia before the start of surgery. According to MORRIS report, none of the hypothermia occurred when the patient was under sedation and the operating room temperature was between 24 and 26℃. Therefore, controlling the operating room temperature is the first step in preventing hypothermia. There are many factors that cause a drop in body temperature due to anesthesia. The skin dissipates heat during the operation of intrathecal anesthesia, the vasodilatation of the blocked area dissipates heat after epidural administration, and the loss of thermogenesis after muscle relaxation, as well as the blocking of warm sensory transmission, all cause a decrease in body temperature.1 General anesthesia weakens the body’s thermoregulatory mechanisms through central and peripheral effects, and anesthetics inhibit thermoregulation in a dose-dependent manner.141 Opiates dilate peripheral blood vessels while also causing The warming of cold anesthetic gases and evaporation of water from the respiratory tract take away some heat; together with the inability of muscles to produce heat due to the effect of muscarinic drugs, body temperature decreases. The rapid decrease in body temperature during preoperative sterilization was confirmed by Sessler et al. to be the result of redistribution of the body’s heat center to the periphery during anesthesia-induced diastole. The body temperature decreases at 0.5 to 1.0 degrees / 4′ after the start of surgery, and the central body temperature decreases significantly when entering the thoracic and abdominal cavities, where there is a large temperature gradient between the central body temperature and the surrounding environment, and the body temperature also decreases significantly during blood transfusion and thoracoabdominal irrigation, because 4 units of cold storage blood or 4 liters of crystalloid fluid can lower the central body temperature by 1 degree. Our study also found that body cavity irrigation in patients at the end of surgery caused a drop in blood pressure. Longer procedures with high transfusion volumes resulted in 85% postoperative hypothermia”.l Some effective measures to maintain heat to maintain constant body temperature are necessary. For example: inhalation of gas to heat and humidify №1, warming of blood and fluids through a heating device before entering the body, warming of the skin on the extremities, replacing volatile disinfectants with disinfectants such as Beta-dine; rinsing the body cavity with warm saline, covering the exposed plasma membrane surface with hot saline sand pads during surgery, preoperative and intraoperative infusion of amino acids “1, etc. Maintaining a constant body temperature during anesthesia and surgery is as important as maintaining the stability of vital signs such as blood pressure and heart rate to improve the quality of anesthesia and perioperative survival.