Postoperative Core Temperature Research Articles

Prevention of inadvertent perioperative hypothermia - Guideline compliance in German hospitals.

Patients undergoing elective surgery are at risk for inadvertent postoperative hypothermia, defined as a core body temperature below 36°C. This study was conducted to investigate the acceptance of the recommendations of the German S3 Guideline, in particular with respect to the concept of pre-warming and sublingual temperature measurement. The main focus was to gather data concerning the postoperative core temperature and the frequency of perioperative hypothermia in patients receiving a pre-warming regime and those without. The study team investigated the local concept and measures employed to avoid inadvertent perioperative hypothermia with respect to defined outcome parameters following a specific protocol. In summary, the study hospitals vary greatly in their perioperative processes to prevent postoperative hypothermia. However, each hospital has a strategy to prevent hypothermia and was more or less successful in keeping its patients normothermic during the perioperative process. Our data could not demonstrate major differences between hospitals in the implementation strategy to prevent perioperative hypothermia in regard to the hospital size. The results of our study suggest a wide-spread acceptance, as no postoperative hypothermia was detected in a cohort of 431 patients.

The Effect of Heated Humidified Carbon Dioxide on Postoperative Pain, Core Temperature and Recovery Times in Patients Having Laparoscopic Surgery: A Randomised Controlled Trial

Study Objective: To determine whether use of heated humidified carbon dioxide as insufflation gas during gynaecologic laparoscopy reduced postoperative pain and hypothermia. Design: A randomised controlled trial (Canadian task Force classification 1). Setting: A tertiary referral hospital. Patients: Sixty women scheduled for gynaecologic laparoscopy between 30 and 90 minutes duration. Intervention: Operative laparoscopic management of endometriosis, adhesions, or adnexal pathology. Measurements and Main Results: Sixty patients were randomised into receiving either heated humidified carbon dioxide (study group) or standard cold dry gas (control group). Intraoperative and postoperative core temperature, total analgesic use, postoperative nausea, and recovery room time were recorded. Postoperative pain intensity was assessed using a visual analogue scale. Statisctical analysis was performed using software. No significant difference was revealed between groups with regard to postoperative pain, analgesic requirements, recovery room time, or postoperative nausea. The control group had less postoperative hypothermia, suggesting that external warming blankets may be more effective than heated humidified carbon dioxide at maintaining intraoperative normothermia. Conclusion: The use of heated humidifed carbon dioxide insufflation for short-duration gynaecologic laparoscopy up to 90 minutes duration was not associated with any significant benefit with regard to postoperative pain, hypothermia or time of recovery room stay.

A randomised controlled trial comparing Mediwrap® heat retention and forced air warming for maintaining normothermia in thoracic surgery☆

Hypothermia is one of the common complications in the perioperative period. Currently, normothermia is maintained with forced air warming (FAW) or passive heat retention methods. We compared the efficacy of the Mediwrap blanket with FAW in maintaining normothermia during intra-operative period in thoracic surgery in a prospective randomised controlled trial on 30 patients. Core temperature was measured at 30-min intervals in the perioperative period and the time taken to attain baseline in the postoperative periods in the two groups was compared. There was no difference in core temperatures between the groups during pre- and intra-operative period, with mean+/-S.D. final core temperatures of 36.2+/-0.6 degrees C with Mediwrap and 36+/-0.9 degrees C with the FAW blanket. However, the postoperative core temperatures were significantly higher in the Mediwrap group. The time required to reach baseline temperature was lower in the Mediwrap group with a mean+/-S.D. of 66+/-66 min as compared to 161+/-108 min in the FAW group. The Mediwrap blanket is as effective as the FAW blanket in maintaining core body temperature during thoracotomy when applied thirty minutes before the surgery.

Noninvasive Temperature Monitoring in Postanesthesia Care Units

Initial postoperative core temperature is a physician and hospital performance measure. However, the extent to which core temperature changes during emergence from anesthesia and transport from the operating room to the postanesthesia care unit (PACU) remains unknown. Similarly, the accuracy of many noninvasive temperature-monitoring methods used in the PACU has yet to be quantified. This study, therefore, quantified the change in core temperature occurring during emergence and transport and evaluated the accuracy and precision of eight noninvasive thermometers in the PACU. In 50 patients having laparoscopic surgery, the authors measured temperatures upon PACU arrival and 30 and 60 min thereafter. Monitoring methods included oral, axillary, temporal artery, forehead skin-surface, forehead liquid-crystal display, infrared aural canal, deep forehead, and deep chest. Bladder temperature was used as the reference and was also measured at the end of surgery. The primary outcome was agreement between individual temperatures from each method and bladder temperature in the PACU. A priori, the authors chose 0.5 degrees C as a clinically important temperature deviation. Bladder temperature increased 0.2 +/- 0.3 degrees C (95% confidence interval 0.1 to 0.3 degrees C), P < 0.001, during transport. None of the tested noninvasive thermometers was consistently within 0.5 degrees C of bladder temperature. However, oral, deep forehead, and temporal artery temperatures were significantly better than other methods and agreed reasonably well with bladder temperature. Invasive temperature monitoring available intraoperatively is more accurate than any generally available postoperative methods. Physician performance measures should therefore not be based exclusively on postoperative temperatures. Among the generally available postoperative monitoring methods, electronic oral thermometry appears to be the best.

Mortality Impact of Hypothermia After Cavitary Explorations in Trauma

Admission hypothermia (core temperature<or=35 degrees C) is an independent risk factor for mortality after trauma. The predictive value of perioperative core temperatures during acute trauma surgery, however, although widely employed as a criterion for initiating damage control, is unknown. We hypothesized that for trauma patients undergoing laparotomy or thoracotomy, early postoperative hypothermia is a predictor of mortality. After institutional review board (IRB) approval, all critically ill trauma patients undergoing cavitary surgery (laparotomy or thoracotomy) at a level 1 trauma center from 01/1998 to 07/2006 were identified from the trauma registry. Immediate postoperative core temperature (Tc) was used to classify patients as hypothermic (Tc<or=35 degrees C) or normothermic (Tc>35 degrees C). The profoundly hypothermic subgroup of patients with a Tc<33 degrees C was also analyzed. During the study period, 2,489 patients required cavitary surgery, 1,252 of whom (50%) were admitted to the intensive care unit (ICU). On arrival in the ICU 15% of the patients had a Tc<or=35 degrees C and were more likely to be >or=55 years old (12% versus 7%; p=0.04); in addition, they were hypotensive on admission (25% versus 13%; p<0.001), had a lower admission Glasgow Coma Score (GCS; 11+/-5 versus 14+/-3; p<0.001), a higher Injury Severity Score (ISS; 29+/-15 versus 22+/-12; p<0.001), higher head and chest Abbreviated Injury Scale (AIS), and greater intraoperative blood loss (2.6+/-2.4 l versus 1.7+/-1.8 l; p<0.001). When compared to patients who were normothermic at the end of their operation, hypothermic patients had a significantly higher mortality (35% versus 8%; p<0.001). With decreasing Tc, there was a stepwise increase in mortality. Compared to patients with a Tc>35 degrees C, the relative risk of death for patients with a Tc between 35 degrees C and 33 degrees C was 4.0, and that for patients with a Tc<or=33 degrees C it was 7.1. After adjusting for multiple differences between groups, postoperative hypothermia remained an independent predictor of mortality (adjusted odds ratio [OR] 3.2; 95% confidence interval [CI] 1.9-5.3; p<0.001). Postoperative hypothermia is common in critically injured patients requiring cavitary surgery and is an independent predictor of mortality. The impact of measures to maintain or restore normothermia in the operating room warrants further investigation.

The Effect of Heated Humidified Carbon Dioxide on Postoperative Pain, Core Temperature, and Recovery Times in Patients Having Laparoscopic Surgery: A Randomized Controlled Trial

Study Objective To determine whether use of heated humidified carbon dioxide as insufflation gas during gynecologic laparoscopy reduced postoperative pain and hypothermia. Design A randomized controlled trial (Canadian Task Force classification 1). Setting A tertiary referral hospital. Patients Sixty women scheduled for gynecologic laparoscopy between 30 and 90 minutes’ duration. Interventions Operative laparoscopic management of endometriosis, adhesions, or adnexal pathology. Measurements and Main Results Sixty patients were randomized into either receiving heated humidified carbon dioxide (study group) or standard cold dry gas (control group). Intraoperative and postoperative core temperature, total analgesic use, postoperative nausea, and recovery room time were recorded. Postoperative pain intensity was assessed using visual analog scale. Statistical analysis was performed using software. No significant difference was revealed between groups with regard to postoperative pain, analgesic requirements, recovery room time, or postoperative nausea. The control group had less postoperative hypothermia, suggesting that external warming blankets may be more effective than heated humidified gas at maintaining intraoperative normothermia. Conclusion The use of heated humidified carbon dioxide insufflation for short-duration gynecologic laparoscopy up to 90 minutes’ duration was not associated with any significant benefit with regard to postoperative pain, hypothermia, or time of recovery room stay.

A Team Approach to the Prevention of Unplanned Postoperative Hypothermia

Postoperative hypothermia (ie, a core temperature lower than 96.8 degrees F [36 degrees C]), is a problem frequently seen in surgical patients, especially those undergoing total joint replacement. Patients who experience hypothermia may have increased recovery times and postoperative complications. A team of clinical staff members and personnel from the performance improvement (PI) department of a hospital used a PI model to incorporate use of preoperative forced-air warming blankets that resulted in improved postoperative core temperatures.

Temperature Monitoring and Management During Neuraxial Anesthesia: An Observational Study

Temperature monitoring and thermal management are rare during spinal or epidural anesthesia because clinicians apparently restrict monitoring to patients with an expected risk of hypothermia. This implies that anesthesiologists can predict patient thermal status without monitoring core temperature. We therefore, tested the hypotheses that during neuraxial anesthesia: 1) amount of core hypothermia depends on the magnitude and duration of surgery; 2) temperature monitoring and thermal management are used selectively in patients at high risk of hypothermia; and 3) anesthesiologists can estimate patient thermal status. We evaluated thermal status on arrival in the recovery room along with intraoperative thermal management and monitoring in 120 patients. Anesthesiologists were asked if their patients were hypothermic (<36°C). There was no correlation between the magnitude or duration of surgery and initial postoperative core temperature in unwarmed patients. Temperature monitoring and thermal management were not used selectively in high-risk patients. Initial postoperative tympanic membrane temperatures were <36°C in 77% of patients and <35°C in 22%. Body temperature was monitored intraoperatively in 27% of the patients and forced-air warming was used in 31%. Anesthesiologists failed to accurately estimate whether their patients were hypothermic. Our results suggest that temperature monitoring and management during neuraxial anesthesia is currently inadequate. Implications In this observational study, we evaluated core temperatures and intraoperative thermal management in patients undergoing spinal or epidural anesthesia. Hypothermia was common, however, rarely detected either by temperature monitoring or estimates by anesthesiologists. In addition, it was not treated with active warming. Consequently, temperature monitoring and management have to be done during neuraxial anesthesia.

Temperature Monitoring and Management During Neuraxial Anesthesia: An Observational Study

Temperature monitoring and thermal management are rare during spinal or epidural anesthesia because clinicians apparently restrict monitoring to patients with an expected risk of hypothermia. This implies that anesthesiologists can predict patient thermal status without monitoring core temperature. We therefore, tested the hypotheses that during neuraxial anesthesia: 1) amount of core hypothermia depends on the magnitude and duration of surgery; 2) temperature monitoring and thermal management are used selectively in patients at high risk of hypothermia; and 3) anesthesiologists can estimate patient thermal status. We evaluated thermal status on arrival in the recovery room along with intraoperative thermal management and monitoring in 120 patients. Anesthesiologists were asked if their patients were hypothermic (<36 degrees C). There was no correlation between the magnitude or duration of surgery and initial postoperative core temperature in unwarmed patients. Temperature monitoring and thermal management were not used selectively in high-risk patients. Initial postoperative tympanic membrane temperatures were <36 degrees C in 77% of patients and <35 degrees C in 22%. Body temperature was monitored intraoperatively in 27% of the patients and forced-air warming was used in 31%. Anesthesiologists failed to accurately estimate whether their patients were hypothermic. Our results suggest that temperature monitoring and management during neuraxial anesthesia is currently inadequate. In this observational study, we evaluated core temperatures and intraoperative thermal management in patients undergoing spinal or epidural anesthesia. Hypothermia was common, however, rarely detected either by temperature monitoring or estimates by anesthesiologists. In addition, it was not treated with active warming. Consequently, temperature monitoring and management have to be done during neuraxial anesthesia.

Thermal energy balance as a measure of adequate rewarming from hypothermic cardiopulmonary bypass

Objective: To determine whether the amount of heat (thermal energy) used actively to rewarm patients on cardiopulmonary bypass (CPB) was a better indicator of adequate rewarming from hypothermic CPB than core temperature. Design: Prospective study. Setting: Single hospital. Participants: Fifty-four sequential patients undergoing hypothermic CPB. Interventions: None. Measurements and Main Results: Thermal energy balance (TEB) (net heat supplied to or removed from the body, from initiation to termination of CPB) was measured using previously validated apparatus. Adequacy of rewarming was assessed by measuring the coldest postoperative core (tympanic membrane) temperature and the time to rewarm postoperatively to a core temperature of 37.0°C. Core temperature on termination of CPB did not correlate with the degree of postoperative hypothermia as judged by time to rewarm postoperatively to 37.0°C (r = 0.14; p = 0.33), but did correlate with coldest postoperative core temperature (r = 0.47; p = 0.0003). TEB correlated better with time to rewarm to 37.0°C (r = 0.43; p 0.001) and coldest postoperative core temperature (r = 0.58, p = 0.0001). Conclusion: TEB is a better predictor than corresponding values of core temperature on termination of CPB in predicting the coldest postoperative temperature and time to rewarm to 37°C. Copyright © 2000 by W.B. Saunders Company

Sigmoid ischemia and the inflammatory response following endovascular abdominal aortic aneurysm repair.

To assess the relationship between sigmoid colonic perfusion, endotoxemia, and cytokine generation in patients undergoing elective open repair (OR) or endovascular repair (EVR) of infrarenal abdominal aortic aneurysms (AAA). Ten patients (9 males; average age 67.6 +/- 2.5 years, mean aneurysm diameter 6.9 +/- 0.6 cm) undergoing OR were compared to 10 patients (all males; average age 70.3 +/- 2.6 years, mean aneurysm diameter 6.5 +/- 0.5 cm) whose repair was performed using the EVR technique. The partial pressure of the carbon dioxide gap (PCO2gap = tissue PCO2 - arterial PCO2) of the sigmoid colonic mucosa was measured using a silicone tonometer to evaluate bowel perfusion. Blood samples were collected into pyrogen-free heparinized tubes for quantification of plasma concentrations of endotoxin, tumor necrosis factor alpha (TNF-alpha), and interleukin 6 (IL-6) before, during, and after aortic repair. Patients in the OR group had a significantly greater increase in PCO2gap, suggesting a greater degree of bowel ischemia compared to the EVR group. This was associated with significantly greater postoperative concentrations of endotoxin, TNF-alpha, and IL-6 in the OR group. A significant correlation was found between PCO2gap, IL-6, and postoperative core temperature. The results suggest that the degree of bowel ischemia, endotoxemia, and cytokine generation following elective infrarenal AAA reconstruction may be reduced if the endovascular technique is used instead of conventional surgery.

Pharmacological vasodilatation improves efficiency of rewarming from hypothermic cardiopulmonary bypass

An afterdrop in core temperature after hypothermic cardiopulmonary bypass (CPB) is related to inadequate peripheral rewarming. We proposed that pharmacological vasodilatation during rewarming on bypass would improve peripheral rewarming and reduce the degree of afterdrop. Fifty-nine of 120 patients were randomized to receive a sodium nitroprusside (SNP) infusion during the rewarming stage of hypothermic CPB. Mean systemic vascular resistance (SVR) during the rewarming phase of CPB was 1129 dyne s-1 cm-5 in the control group and 768 dyne s-1 m-5 in the SNP group (P < or = 0.001). Patients receiving SNP rewarmed to 37.0 degrees C faster (299 min vs 376 min; P = 0.003) and were extubated earlier (490 min vs 621 min; P = 0.001). Patients receiving SNP had a warmer mean peripheral temperature (MPT) (32.9 degrees C vs 32.4 degrees C; P = 0.05) on termination of CPB. Postoperative core temperature fell less in the SNP group (35.6 degrees C vs 35.2 degrees C; P = 0.01) as did MPT (31.8 degrees C vs 31.2 degrees C; P = 0.004). SNP-induced vasodilatation during rewarming from hypothermic CPB improves peripheral rewarming, reduces the degree of postoperative core and peripheral hypothermia and reduces time to extubation.

Forced-air warming is no more effective than conventional methods for raising postoperative core temperature after cardiac surgery

Objective: To determine whether postoperative forced-air warming of cardiac bypass patients in the intensive care unit (ICU) results in faster rate of warming and improved outcomes compared with more conventional ICU warming methods. Design: Prospective randomized effectiveness study. Setting: Three hundred fifty—bed university-affiliated hospital. Participants: Sixty consenting randomized patients from a consecutive series of 84 patients undergoing routine adult cardiac surgery. Interventions: One group of patients received usual patient care, which includes warm blankets and overhead heat lamps. Patients in the other group were placed under forced-air warming devices on arrival in the ICU. Sixty consenting patients (30 in each group) were randomly assigned to one or the other method of warming. The remaining 24 patients refused randomization and self-selected a treatment group. Measurements and Main Results: Results are presented for the randomized groups. Core temperature, measured by pulmonary artery catheter thermistor, increased in both groups at the rate of 0.25°C per hour. No statistically or clinically significant differences were found between the group for whom the warming device was used and the standard care group in the incidence of postoperative cardiac arrhythmia, duration of time in the ICU, or any other clinical variable. Conclusions: There is no evidence from this study to warrant use of forced-air warming devices for the care of postoperative cardiac surgical patients in the ICU.

Acute-phase responses to cardiopulmonary bypass in children weighing less than 10 kilograms

Cardiopulmonary bypass induces a systemic inflammatory response. This study investigated, in a pediatric population, cytokine-induced responses and their potential modification by intraoperative steroid administration. Markers of the acute-phase response were measured perioperatively in 24 children weighing less than 10 kg undergoing cardiac operations. Those having operations with cardiopulmonary bypass were randomized to receive either no steroid (group I, n = 8) or 10 mg/kg methylprednisolone in the pump prime (group II, n = 10); patients undergoing nonbypass procedures were controls (group III, n = 6). In all groups, plasma interleukin-6 level was elevated (p < 0.01) above baseline throughout the post-operative period, peaking earlier in group I. Levels of C-reactive protein peaked at 48 hours, and postoperative core temperature was raised in all groups. Levels of interleukin-6 from 2 to 6 hours and C-reactive protein at 24 hours postoperatively were greater (p < 0.05) in group I than in group II. Maximum interleukin-6 level, C-reactive protein level, and temperature were all significantly greater in group I than in group III. Maximum interleukin-6 level correlated with maximum C-reactive protein level in group I only (rs = 0.76; p < 0.05) and showed no association with temperature. Duration of bypass did not correlate with levels of interleukin-6. This study demonstrated a marked acute-phase response to operation; the greater response to procedures with cardiopulmonary bypass was abrogated by intraoperative steroid administration. The importance of interleukin-6 as an inducer of acute phase proteins after bypass is supported by its association with C-reactive protein levels, but other factors must be important in the induction of pyrexia.

Postoperative hemodynamic and thermoregulatory consequences of intraoperative core hypothermia

Study Objective: To evaluate the postoperative hemodynamic and thermoregulatory consequences of intraoperative core hypothermia. Design: Prospective, randomized clinical trial. Setting: Operating room and postanesthesia care unit of a university hospital. Patients: 74 healthy, ASA status I, II, and III patients (average age 58 yrs) undergoing elective colon surgery. Interventions: Patients were randomly assigned to be kept normothermic or ≈2.5 °C hypothermic during surgery. Anesthesia was maintained with isoflurane, nitrous oxide, and fentanyl. Postoperatively, surgical pain was treated with patient-controlled analgesia (PCA) opioid. Measurements and Main Results: An observer blinded to group assignment and core temperatures evaluated shivering, thermal comfort, surgical pain, heart rates (HRs), and blood pressures (BPs) during the first six postoperative hours. Morphometric characteristics, oxygen saturation, fluid balance, PCA-administered opioid, and visual analog pain scores were comparable in the two groups. Hypothermic patients felt uncomfortably cold during recovery, and their postoperative core temperatures remained significantly less than in the normothermic patients for more than four hours. Peripheral vasoconstriction and shivering were common in the hypothermic patients but rare in those kept normothermic. HRs and BPs were comparable in the two groups. Conclusions: These data confirm that the effects of intraoperative hypothermia on postoperative HR and BP are modest in relatively young, generally healthy patients. In contrast, intraoperative hypothermia caused substantial postoperative thermal discomfort, and full recovery from hypothermia required many hours. Delayed return to core normothermia apparently resulted largely from postoperative thermoregulatory impairment.

Postoperative Temperature Measurement

The purpose of this study was to determine the validity of the axillary site for temperature measurement in the postoperative patient. Axillary electronic, axillary mercury, rectal mercury, and core body temperatures were obtained in 18 postoperative patients. Rectal temperatures correlated extremely well with core temperatures, r = .98, but on average were .5 degrees C higher than core. Mercury axillary left in place for 10 minutes had the next highest correlation, r = .96, but on average were .2 degrees C lower than core. Electronic axillary were the poorest indicator of core temperature, r = .92, and were on average .6 degrees C lower than core. The correlation of -.64 between age and postoperative core temperature suggests that the elderly are most susceptible to hypothermia in a surgical setting.