The Role of Perfusion Index in Defining Postoperative Shivering

Perioperative hypothermia is generally defined as body temperature below 36.0oC. While classified as mild hypothermia (34.C-36.C), moderate hypothermia (32.C-34.C) and severe hypothermia (<32 °C), the most reliable monitoring sites are: pulmonary artery, distal esophagus, nasopharynx and tympanic membrane. measurements. Within approximately 60-90 minutes after anesthesia induction, body temperature decreases with redistribution of the physiological effect of anesthesia. The incidence of perioperative hypothermia in postoperative patients has been reported to be between 20% and 70%. Even mild hypothermia increases the incidence of wound infection, postoperative ischemic myocardial events, and intraoperative blood loss and prolongs the postoperative recovery period. In the hospital environment, the temperature in the extremities is usually 2 to 4°C cooler than the core temperature, and the skin surface is even colder. Body temperature during surgery is affected by a number of anesthesia-related, surgical, environmental, or patient-related risk factors. Surgical risk factors such as surgical technique, duration of surgery, scope of surgery, procedure and amount of irrigation fluid used are at the forefront. In temperature change, behavioral regulation is the strongest thermoregulatory effector. However, patients under anesthesia cannot activate behavioral responses; thermoregulation is only provided by autonomous mechanisms and external thermal management. Vasoconstriction is the most commonly used autonomous effector mechanism in this process. If vasoconstriction is not sufficient and body temperature drops below a certain threshold, shivering begins. Shivering, an involuntary oscillatory pattern of skeletal muscle activity that increases heat production by up to sixfold, is a compensatory mechanism in this sense. It occurs when the temperature of the preoptic area of the hypothalamus decreases. Shivering increases oxygen consumption, causing lactic acidosis, carbon dioxide production, and catecholamine release, eventually increasing cardiac output, heart rate, and arterial pressure. Studies are continuing on the use of perfusion index (PI) for diagnostic purposes regarding the emergence of tremor. Therefore, PI may help reduce the incidence of postoperative shivering with preoperative precautions and preparations. Perfusion index can be calculated using pulse peripheral perfusion oximetry: expressed as the ratio of the pulsatile signal (arterial blood) to the percentage of the non-pulsatile signal (skin, other tissues and non-pulsatile blood), it is a non-invasive measurement, obtained from the amount of infrared light absorbed. PI simultaneously images peripheral perfusion changes during anesthesia, ıt's a very useful monitorization that can help determine the redistribution of body temperature, the effects of vasodilation and their relationship with anesthesia. Previous prospective studies have shown that patients with low PI values before induction of anesthesia are more likely to develop intraoperative hypothermia. It has been found that under general anesthesia, skin temperature contributes almost 20% to the control of vasoconstriction and postanesthetic shivering threshold. In this study, investigator planned to examine whether perioperatif changes in perfusion index are correlated with the incidence of postoperative shivering and therefore whether perfusion index can predict postoperative shivering for preventive purposes under general anesthesia.