Patient care in inadvertent hypothermia - Assignment Example

? Patient care in inadvertent hypothermia Patient care in inadvertent hypothermia Patient care in inadvertent hypothermia The spontaneous lowering ofcore body temperature below 360 F is inadvertent hypothermia (Hart, 2011). The unwarmed surgical patient usually presented with this feature. Perioperative hypothermia had a potential for morbidity and mortality. The patients who had perioperative hypothermia had a chance for surgical site infections especially in patients with colorectal surgery (Hart et al, 2011). The guidelines of Surgical Care Improvement Project encouraged the decrease in incidence of this illness. Human beings required internal body temperatures to be constant for the multiple organs to function optimally. The situation changed when the patient entered the operation theatre. The temperatures of the operation rooms were kept below 230C. Almost all the surgeries required this temperature for maintenance of normothermia for the reason that the operation theatre staff found the temperature for normothermia slightly warm for work. This caused the maintenance of lower temperatures in the theatre. Actual heat loss was governed by room temperature as the temperature gradient determined the heat loss. Surgeons and other staff could not withstand the warmth because of the stress of surgery and the layers of clothing they wore and the lead aprons. Prevention of perspiration was essential to avoid the problem of sweat polluting the surgical site. Staff could generally become lethargic with the higher room temperature hindering their vigilance which was critical in the operation theatre. However patients commented about the cold room. Inadvertent hypothermia is the aspect of care that has been selected by this researcher for study. Information on the issue of hypothermia was gathered from review of literature beginning with the study by Hart et al (2011). The review of literature provided plenty of basic information that could help readers to understand this topic of management of inadvertent hypothermia better. This researcher has carefully selected articles most recently published from the Pubmed Central site. Analysis of current evidence base Perioperative hypothermia Perioperative hypothermia of below 360C was experienced by 20% of patients (Kurz, 2008). Anaesthesia rendered a patient devoid of many defensive mechanisms for becoming warmer in the instance of hypothermia. Behavioural modification was eliminated so that patients became colder. Thermoregulatory mechanisms did not function so unwarmed patients became hypothermic. Perioperative hypothermia produced adverse effects like elevated loss of blood during surgery, a higher rate by 20% of allogeneic transfusions and an increase of surgical site infections by three times (Hart et al, 2011). Prevention of hypothermia had guidelines instituted by the Surgical Care Improvement Project (SCIP) for operative and post-operative patients. Perioperative normothermia was to be maintained by warming devices. Staff providing the warming support was to be knowledgeable about the mechanisms of temperature regulation, perioperative hypothermia and the methods to prevent or manage hypothermia. Temperature monitoring Temperature monitoring became an essential component of perioperative care. Oral temperature measurement was the best technique according to the American Society of Perianesthesia Nurses (ASPAN). The same method of measurement needed to be maintained throughout perianaesthesia (Hart et al, 2011). The temperature at the depth of the thoracic, abdominal and central nervous systems was the core temperature. It was more consistently controlled and was 2-40C higher than skin temperature. The measurement was made at the distal end of the oesophagus, from a bladder with good urine flow, the nasopharynx and the pulmonary artery in general anaesthesia patients. The core temperature was the most reliable indicator of the thermal status (Sessler, 2008). Near-core temperatures were taken from the axillary area, rectum, bladder with low urinary flow and oral region in regional anaesthesia and perioperative patients (Hart et al, 2011). Near-core temperature could be influenced by ambient temperature and the regional skin blood flow but rectal and bladder temperatures were not affected. Occasionally a liquid crystal strip attached to the forehead could measure the thermal status. Mechanisms of loss of body temperature Loss of heat through radiation accounted for most of the loos of body temperature in peri-operative patients. Convection loss was prevented to a certain extent by the insulation of the skin. The exchange of air in the operating room was more than three times faster than in the other rooms. The blankets or surgical drapes helped to save this loss by convection. Conduction and evaporation from the wound only accounted minimally to the loss (Hart et al, 2011). Physiology of temperature regulation Normal body temperature is 98.60F. In normal circumstances the body temperature was regulated to within one-tenth of a degree Celsius. However in the operation room, other thermoregulatory mechanisms existed which reduced the core body temperature and thereby perioperative hypothermia resulted as the body regulation of temperature did not function well after anaesthesia. So most patients could have hypothermia if warming was not done (Hart et al, 2011). The nervous network of regulation consisted of the thermal sensing afferent cells, the central regulation by the hypothalamus and the spinal cord to a small extent. The efferent response was by the behavior modification, shivering and vasoconstriction. Neonates did not show shivering. Regulation of the blood flow through the arterio-venous shunts on the skin surface produced temperature regulation. Core temperature and types of hypothermia The core temperature was the temperature within the central circulation and hypothalamus-regulated (Kjellman et al, 2011). Normal core temperature is 36.5-37.50C. This temperature remained steady even when ambient temperatures fluctuated, enabling the biochemical functions to proceed undisturbed. However in trauma, burns and anesthetized patients, disturbances occurred and this was when interventions became necessary. Three classes of hypothermia had been identified based on the core temperature. The ranges of 35-32°C, 32-30°C and less than 30°C were classified into mild, moderate and severe (Kjellman et al, 2011). The ranges for injured people were between 36 and 34°C for mild, between 34-32°C for moderate and less than 32°C for severe types. Temperature regulation in anaesthetized patients Vasoconstriction occurring as a normal response to hypothermia became inhibited by general anesthetics (Hart et al, 2011). The dispersing of the core temperature, which normally was higher in the head and truncal regions, to the periphery within one hour of anaesthesia caused hypothermia. The core temperature was noted to be speedily decreasing in the first hour. Then it became stable due to a loss of sympathetic tone caused by the vasodilatory effects of general anaesthesia. The warmer periphery had a greater tendency to lose heat to the environment. So a graph showed a faster decrease of core temperature in the first hour (Phase I) and then a slower decrease (Phase II) where heat loss still exceeded heat production (Hart et al, 2011). Phase III was a plateau phase occurring after 3-4 hours when the core temperature became stable and the vasoconstriction began. Epidural and spinal anaesthesia also decreased the shivering and vasoconstriction to a smaller level. Regional anaesthesia blocked the thermal input in regions. Sedatives and analgesics further impaired the temperature regulation (Hart et al, 2011). Inadvertent hypothermia in the postoperative period Inadvertent hypothermia was common in the post-operative period immediately after surgery (Abelha et al, 2005). Abelha and his co-researchers performed a study to measure the prevalence, find the predictive factors and assess the outcome of core hypothermia after admission to the surgical ICU. The impairment of organs and body systems could produce adverse outcomes. The background of the study had elicited information on the adverse outcomes. The changes of impairment produced a reduction in the oxygen released into the tissues. Myocardial contractility was suppressed and peripheral vasoconstriction was evident. Some researcher had reported a mismatch of the ventilation-perfusion and an increase in the viscosity of blood with shifts in the oxyhemoglobin-dissociation curve to the left (Abelha et al, 2005) Platelet functions were affected. The coagulation cascade activation was lesser. Coagulopathy could result (Abelha et al, 2005). The hypothermia was especially seen in high-risk surgical patients. Rapid loss of heat occurred when higher volumes of fluid were administered and ambient temperatures added to the loss. The patient responded by regulating the temperature through the sympathetic nervous system evident by the shivering and peripheral vasoconstriction. The shivering tended to increase the exertion on the cardiac muscles and energy requirement. The oxygen consumed and carbondioxide produced became raised increasing the cardiac functions (Abelha et al, 2005). Earlier randomized controlled trials had shown a greater incidence of surgical wound infections, ischaemic heart disease, arrhythmias, drug effects of anaesthesia, shivering, lengthy recovery room stay and prolonged post-anaesthetic care and hospital stay. With all the precautions of pre-warming, temperature monitoring, advances in surgery and anaesthesia, longer surgeries were being planned for older patients. The risk of hypothermia was still seen in the perioperative period especially in the ICU postoperatively. The patients who were admitted for 4 consecutive months in the surgical ICU were the 185 non cardiac participants (Abelha et al, 2005). Patients who temperature was below 350C were classed as hypothermic and the others were normothermic. At the time of ICU admission, prevalence was 57.8%. The protective factors for the prevention of core hypothermia were the extensiveness of the surgery, whether general anaesthesia was used or whether a combination of epidural and general were used, whether total intravenous crystalloids were used, whether total packed RBCs were given, whether anaesthesia was longer than 3 hours. It was found that hypothermia did not have a place in the risk factors for hospital mortality or for prolonged stay in the ICU. The risk factors for hypothermia were the extensiveness of surgery, disease severity, prolonged anaesthesia, combinations of types of surgery like epidural with general anaesthesia, large intake of IV fluids, absence of temperature monitoring or pre-warming devices. Monitoring the patients’ body temperature proved significant (Abelha, 2005). The guidelines established that inadvertent hypothermia could be prevented by strictly following the recommendations about monitoring of temperature and the guidelines about thermal management. Abelha’s study (2005) also suggested that warmer pre-operative body was protective for preventing hypothermia. Older patients were not more prone to hypothermia. The severely ill patients had a bigger possibility of arriving hypothermic at the ICU. An and Yang investigated the effects of PEEP on the thermoregulatory responses during TIVA in patients undergoing tympanoplasty (2011). The redistribution of body heat to the periphery reducing the body temperature had been described as being due to peripheral vasodilation and arteriovenous shunt expansion. This explanation appeared a little different from the explanation by Hart et al (2011) for the redistribution of body heat in general anaesthesia. The core temperature decreased due to the redistribution of body heat. The explanation for the decrease in body temperature was that of the core temperature reaching the vasoconstriction threshold, the vasoconstriction occurred then reducing the heat loss. The plateau phase described by Hart et al, where the redistribution and the decrease in body temperature was controlled had been described as “reaching equilibrium” by An and Yang (2011). Normally temperature regulation occurred within a range of 0.20C. However during general anaesthesia, the range of regulation became wider due to the rise in sweating threshold and reduction in the threshold for vasoconstriction. PEEP or positive end expiratory pressure had an influence on the vasoconstriction threshold. Intrathoracic pressure was elevated and the venous return reduced by PEEP. This resulted in secondary vasoconstriction and an increase in the thermoregulatory vasoconstriction threshold through carotid unloading (Sessler, 2008). Core temperature was influenced by the cardiac filling pressure or the baroreceptor loading level through the modification of the thermoregulatory peripheral vasoconstriction (An and Yang, 2011). The PEEP influence on the perioperative hypothermia was through unloading of the baroreceptors (Mizobe et al, 2005). The thermoregulatory response in total intravenous anaesthesia with propofol-remifentanil was investigated by An and Yang (2011). Forty patients who were healthy and being prepared for tympanoplasty were divided into two groups: ZEEP and PEEP. The ZEEP group with 20 patients had zero-end respiratory pressure. The PEEP group had an application of 5cm. H2O end respiratory pressure. The ambient temperature was maintained at 22-240C. The anaesthesia was induced and maintained by propofol-remifentanil (An and Yang, 2011). General anaesthesia lasted for 180 minutes. The core temperature and the difference in temperature taken at two points were recorded before and after the anaesthesia (the forearm and the fingertip skin). The results indicated that the core temperature noted was higher. The peripheral vasoconstriction, the threshold for vasoconstriction and the time for threshold were higher. In general anaesthesia, it was due to a number of reasons that hypothermia occurred. The reduced response of the body to changes in temperature and autonomic nervous system and the inability to regulate body temperature contributed to the inadvertent hypothermia in general anaesthesia (An and Yang, 2011). However the reason that answered most for the hypothermia was the redistribution of the body heat from the core to the periphery through a process of arterio-venous shunt and supported by a reduced vasoconstriction threshold (Ikeda et al, 1999 in An and Yang, 2011). The anaesthetics used had the action of suppression of the normal actions of the autonomic nervous system. The consequences were a rise in the threshold for sweating and a simultaneous reduced threshold for cold response which was constituted by the thermoregulatory vasoconstriction and threshold for shivering. Thus the range between the threshold became larger by 10 times (Sessler, 2009). The body temperature was reduced by 1.6 + 0.30C in an hour of anaesthesia and the heat redistribution from the core to the periphery answered for 81% of the heat reduced in a study by Matsukawa et al (1995 in An and Yang, 2011). The redistribution occurred through the arterio-venous shunts of 100?m thickness. Inhalation anesthetics seemed to have similar responses of the general anesthetics. A significant finding was the lower core temperature attained through the use of 5 vol % of sevoflurane. The leg-up position of the patient produced a larger temperature drop (An and Yang, 2011). Mitzobe’s findings had been different regarding the core temperature decrease and the time when skin temperature change was greater (2005). Nakajima found that the sitting-up position showed a greater difference in temperature as compared to the supine position in unanaesthetised patients (2002 in An and Yang, 2011). The reasons were claimed to be the responses of a higher level of activity of the peripheral sympathetic nervous system and a higher level of norepinephrine in the sitting position. This led to a reduced adrenaline flow to the brain causing suppression of the hypophysis. Subsequently the cold responses were suppressed and heat generation occurred through the thermoregulatory process. Thermal vasoconstriction occurred only in the anaesthetized patients. The hypothermia in anaesthetized patients produced a dysfunctioning of the platelets and a coagulation disorder leading to immunosuppression and infection because of the reduced blood flow (An and Yang, 2011). Postoperative heart complications occurred because of the rise in catecholamine secretion. Several problems were related to the inadvertent hypothermia in anaesthesia: heart complications, prolonged wound healing, slow recovery from the anaesthesia, longer hospital stay and higher oxygen consumption. Prevention of hypothermia therefore became essential in patients doing TIVA propofol-remifentanil. PEEP in TIVA helped to decrease intraoperative hypothermia by reducing the drop in temperature and elevating the vasoconstriction (An and Yang, 2011). Hypothermia was common in burns and also increased the morbidity and mortality rates (Kjellman et al, 2011). Previous studies on hypothermia had not focused on burns patients. The drawbacks in effective treatment of hypothermia in their hospital had initiated the researchers into this research. Ten burns patients who had more than 20% burnt surface area and core temperature less than 360C were selected as participants for this prospective, randomised, comparative study. Each treatment/ measurement cycle lasted six hours. Heating method was assessed for 2 hours. An indwelling bladder thermistor was used for recording core temperature. The paired t-tests were used to estimate the significance of differences of treatment between the groups of patients. The conventional blankets, the Thermowrap of AllonTM2001 and the Warmcloud were used for determining the best to prevent hypothermia. The Thermowrap of AllonTM2001 was found to provide more comfort. The journey of burns patients from the site of trauma to the burns unit took a long time usually in a hypothermic state. The anaesthetic procedures at time of arrival further lengthened the hypothermic period. The burns unit had means to increase the ambient temperature, provide warm fluids for resuscitation, warm blankets, radiators in the ceilings and hot air (Kjellman et al, 2011). However these methods were insufficient to reduce the hypothermia as they depended on staff who could be influenced by the changes made. Three warming techniques had been described: passive rewarming, active external rewarming and active core rewarming. Passive rewarming was possible with the burns unit fittings which allowed endogenous heat production by changing the environment. Active external rewarming involved the adding of heat to the body surface by using convective air blankets. Active core warming involved the addition of heat to the internal body surface. A combination of procedures was needed for burns patients. Convective air blankets could not sometimes be effective as the peripheral vasoconstriction in the patients was only minimally susceptible to external warming. Also the local heat build-up in already traumatised skin could cause further thermal injury. The active rewarming by infusion of warm liquids could produce a better response (Kjellman et al, 2011). Lavage of body cavity and airway rewarming had also been described. Invasive techniques had been used in many instances like the intravascular thermal regulation catheters which were effective but could not be recommended for burns patients with skin trauma. The complications which increased morbidity and mortality were ischaemic heart disease, arrhythmias and coagulopathies because the essential underlying problem was the poor wound healing, immunological disturbances, stress problems and neurological impairments (Kjellman, 2011). In spite of having Bair Hugger™ (warming units with accessories), radiator ceilings, bed warmers (warm air), and Hotline or Fluido- infusion heaters, cases of hypothermia still occurred in the operation theatre (OT) before and after surgical procedures (Kjellman et al, 2011). The ambient temperature was a little warm for the staff working inside the OT. However the patients who had leaking wounds tended to go into hypothermia because of the strong convection currents. The AllonTM 2001Thermowrap was a novel temperature –regulating water mattress with regulating fluid convection. KanMed Warmcloud was another air mattress with air convection. The fluid convection mattress was found useful in thoracic and abdominal surgery and was better than traditional methods of reducing hypothermia. These 2 new methods had not been used in burns patients. Kjellman et al (2011) investigated the efficiency of the fluid convection and air convection in hypothermia in burn patients. The patients were exposed to traditional warming techniques and the fluid convection and air convection randomly. Six hour treatment –measurement cycles which contained 2 hours of each of the three methods were planned. Core temperature of more than 360C was to be reached. The best technique was found to be the Allon™2001 Thermowrap for normalizing hypothermia. The work environment was also simultaneously improved for the staff (Kjellman et al, 2011). Analysis of current practice Prevention of hypothermia had guidelines instituted by the Surgical Care Improvement Project (SCIP) for operative and post-operative patients (Hart et al, 2011). Perioperative normothermia was to be maintained by warming devices. Temperature monitoring had become an essential component of perioperative care (Hart et al, 2011). Oral temperature measurement was the best technique according to the American Society of Perianesthesia Nurses (ASPAN). The core temperature was the most reliable indicator of the thermal status and it was 2-4 0C warmer than skin temperature (Sessler, 2008). The measurement was made at the distal end of the oesophagus, from a bladder with good urine flow, the nasopharynx and the pulmonary artery in general anaesthesia patients (Hart et al, 2011). Near core temperatures, which were influenced by ambient temperature and regional skin blood flow, were taken from the axillary area, rectum, bladder with low urinary flow and oral region in regional anaesthesia and perioperative patients (Hart et al, 2011). The normal response to hypothermia in anaesthetized and burn patients was vasoconstriction (Hart et al, 2011). Hypothermia in both situations was accompanied by vasoconstriction and core temperature redistribution (Hart et al, 2011; Kjellman et al, 2011). Then the temperature became stable due to a loss of sympathetic tone caused by the vasodilatory effects of general anaesthesia. The third phase was steady resembling a plateau on a graph with the core temperature becoming stable and vasoconstriction occurring in 3-4 hours (Hart et al, 2011). Epidural and spinal anaesthesia also produced the changes but at a smaller level. Sedatives and analgesics further impaired the temperature regulation (Hart et al, 2011). Kjellman indicated that the redistribution of core temperature was due to vasodilatation and arterio-venous shunting (Kjellman et al, 2011). Hart’s plateau phase was equivalent to the equilibrium phase of An and Yang (2011). Abelha (2005) contended that myocardial contractility was suppressed and peripheral vasoconstriction was evident, a mismatch of the ventilation-perfusion existed and an increase in the viscosity of blood with shifts in the oxyhemoglobin-dissociation curve to the left were seen in inadvertent hypothermia. Surgical patients who entered ICU with hypothermia showed greater impairments later. Shivering and the vasoconstriction helped to reduce the hypothermia. Earlier randomized controlled trials had shown a greater incidence of surgical wound infections, ischaemic heart disease, arrhythmias, drug effects of anaesthesia, shivering, lengthy recovery room stay and prolonged post-anaesthetic care and hospital stay. The protective factors for the prevention of core hypothermia were the extensiveness of the surgery, whether general anaesthesia was used or whether a combination of epidural and general were used, whether total intravenous crystalloids were used, whether total packed RBCs were given and whether anaesthesia was longer than 3 hours. The guidelines established that inadvertent hypothermia could be prevented by strictly following the recommendations about monitoring of temperature and the guidelines about thermal management. Positive end expiratory pressure (PEEP) had an influence on the vasoconstriction threshold. PEEP increased the intrathoracic pressure and reduced the venous return (An and Yang, 2011). This resulted in secondary vasoconstriction and an increase in the thermoregulatory vasoconstriction threshold through carotid unloading (Sessler, 2008). The reduced response of the body to changes in temperature and autonomic nervous system and the inability to regulate body temperature contributed to the inadvertent hypothermia in general anaesthesia (An and Yang, 2011). The consequences were a rise in the threshold for sweating and a simultaneous reduced threshold for cold response which was constituted by the thermoregulatory vasoconstriction and threshold for shivering. Nakajima found that the sitting-up position showed a greater difference in temperature as compared to the supine position in unanaesthetised patients (2002 in An and Yang, 2011). The reasons were claimed to be the responses of a higher level of activity of the peripheral sympathetic nervous system and a higher level of norepinephrine rewarming in the sitting position causing reduced adrenaline flow to the brain and thereby suppression of the hypophysis. Subsequently the cold responses were suppressed and heat generation occurred through the thermoregulatory process. Prevention of hypothermia therefore became essential in patients doing TIVA under propofol-remifentanil. A combination of procedures was needed for burns patients. Active core rewarming done by infusion of warm liquids could produce a good response (Kjellman et al, 2011). The Bair Hugger™ (warming units with accessories), radiator ceilings, bed warmers (warm air), and Hotline or Fluido- infusion heaters along with the AllonTM 2001Thermowrap or KanMed Warmcloud could be used for normalizing hypothermia in burns patients. Current nursing management and recommendations Hart et al have described the various aspects of nursing management of hypothermia and the recommendations for looking out for it and for managing it in the peri-operative period (2011) These recommendations were based on research evidence. Temperature measurement Guidelines from the American Society of Perianesthesia Nurses (ASPAN) provided evidence-based recommendations for temperature monitoring. Core temperature measuring was the best, however the near-core measurement was the next best if the core could not be taken as the benefit was more than the risk as evidenced from the multiple randomized controlled studies and meta-analyses (Hart et al, 2011). Oral temperature measurement was the best near-core measurement and highly beneficial over the risk and is evidenced by single randomized trials or nonrandomized studies evaluating limited. The same method of measurement was to persist throughout the perioperative period so that comparison was easier as the benefit was high over the risk and was evidenced from case studies and standards of care. Caution should be taken in management Risk factors for perioperative hypothermia Strong evidence had not been found yet for any risk factor. There was weak evidence which considered the higher age group and patients with systolic blood pressure less than 140mm Hg., both risk factors where the benefit outweighed the risk but it was reasonable to administer the recommendations as they were evidenced by single randomized trials or nonrandomized studies evaluating limited populations. The female gender and the higher level of spinal block were groups with benefit and risk being equal and could be considered as risk groups for administering the recommendations as evidenced from single randomized trials or nonrandomized studies evaluating limited populations. There was insufficient evidence to consider body mass below normal but benefit for this factor outweighed the risk and recommendations could be administered as evidenced by case studies, standards of care, or expert opinion involving very limited populations. The risks about normal body mass, procedural duration, body surface or uncovered wound area, duration of anesthesia and history of diabetes were not known due to little evidence. Pre-operative recommendations Risk factors for perioperative hypothermia needed to be assessed. Patient temperature was to be measured on admission. Thermal comfort level of the patients was to be determined. Signs and symptoms of hypothermia were to be assessed. All risk factor assessment findings were to be documented and communicated to all members of the anesthesia/surgical team. Passive thermal measures were to be implemented. Ambient room temperature was to be maintained at or above 240C. Active warming was to be instituted for patients who were hypothermic. Preoperative warming was to be considered for reducing risk of intra/postoperative hypothermia. Prewarming for a minimum of 30 minutes could reduce the risk of subsequent hypothermia. Non-emergent patients had to be normothermic before transferring to the operating room/procedure area. Emergent patients were to be warmed as soon as clinically appropriate. Intraoperative recommendations Patient risk factors were to be identified for unplanned perioperative hypothermia. Frequent intraoperative temperature monitoring was to be done. Signs and symptoms of hypothermia were to be assessed. Patient’s thermal comfort level was to be ensured. All risk factor assessment findings were to be documented and communicated to all members of the anesthesia/surgical team. Skin exposure was to be limited to lower ambient environmental temperature. Passive warming measures were to be initiated. Ambient room temperature was to be maintained from 20-250C based on Association of Perioperative Registered Nurses and architectural recommendations. Active warming was to be initiated for patients who were already hypothermic for undergoing even a short procedure of 30 minutes, for patients who were at risk of hypothermia and with increased risk of having complications. Alternative active warming measures could maintain normothermia when used alone or in combination with forced-air warming. These warming measures included warmed intravenous fluids, warmed irrigating fluids, circulating water garments, circulating water mattresses, radiant heat gel pad surface warming and resistive heating. Postoperative recommendations Assessment was to be made of the patient’s risk factors for perioperative hypothermia. All risk assessment findings were documented and communicated to all members of the healthcare team. Patient’s temperature was to be measured on admission to the PACU If normothermic, measurement was continued every hour. If hypothermic, measurement was continued every 15 minutes till normothermia was reached. Patient’s thermal comfort level was to be assessed. Signs and symptoms of hypothermia were to be noted. References: Abelha, FJ, Castro MA, Neeves, AM, Landeiro, NM and Santos, CC 2005, Hypothermia in a surgical intensive care unit. BMC Anesthesiology 2005, 5:7 doi:10.1186/1471-2253-5-7 BioMed Central An, T-H, Yang, JW 2011, Effects of PEEP on the thermoregulatory responses during TIVA in patients undergoing tympanoplasty Korean J Anesthesiol 2011 October 61(4): 302-307 http://dx.doi.org/10.4097/ kjae.2011.61.4.302 Hart, SR, Bordes,B, Hart, J, Corsino, D and Harmon, D 2011, Unintended Perioperative Hypothermia The Ochsner Journal Vol. 11, No. 3, 259–270, 2011, Academic Division of Ochsner Clinic Foundation Kjellman, B-M, Fredrikson, M, Sjoberg, F. and Huss, FRM 2011, Comparing ambient, air-convection, and fluid convection heating techniques in treating hypothermic burn patients, a clinical RCT, Kjellman et al. Annals of Surgical Innovation and Research 2011, 5:4http://www.asir-journal.com/content/5/1/4 Kurz A 2008, Physiology of thermoregulation. Best Pract Res Clin Anaesthesiol. 2008;22(4):627-644. Mizobe T, Nakajima Y, Sunaguchi M, Ueno H, Sessler DI 2005, Clonidine produces a dose-dependent impairment of baroreflex-mediated thermoregulatory responses to positive end-expiratory pressure in anaesthetized humans. Br J Anaesth 2005; 94: 536-41. Sessler DI 2008, Temperature monitoring and perioperative thermoregulation. Anesthesiology. 2008;109(2):318-38 Sessler DI 2009, Temperature regulation and monitoring. In: Miller's anesthesia. 7th ed. Edited by Miller RD, Ericksson LI, Fleisher LA, Wiener-Kronish JP, Young WL: Philadelphia, Churchill-Livingstone. 2009, pp 1542-3. Read More