The Accuracy and Precision of Body Temperature Monitoring Methods During Regional and General Anesthesia

Prospective comparative analysis of zero-heat-flux thermometer (SpotOn®) compared with tympanic thermometer and bladder thermometer in extremely aged patients undergoing lower extremity orthopedic surgery

Thermoregulation is important for maintaining homeostasis in the body. It can be easily broken under anesthesia. An appropriate method for measuring core body temperature is needed, especially for elderly patients, because the efficiency of thermoregulation gradually decreases with age. Zero-heat-flux (ZHF) thermometry (SpotOn) is an alternative, noninvasive method for continuous temperature monitoring at the skin surface. The aim of this study was to examine the accuracy and feasibility of using the SpotOn sensor in lower extremity orthopedic surgery in elderly patients aged over 80 years by comparing a SpotOn sensor with 2 other reliable minimally invasive methods: a tympanic membrane thermometer and a bladder thermometer. This study enrolled 45 patients aged over 80 years who were scheduled to undergo lower extremity surgery. Body temperature was measured using a SpotOn sensor, a tympanic membrane thermometer and a bladder thermometer. Agreements between the SpotOn sensor and the other 2 methods were assessed using Bland and Altman plots for repeated measures adjusted for unequal numbers of measurements per patient. Compared with bladder temperature, bias and limits of agreement for SpotOn temperature were 0.07°C ± 0.58°C. Compared with tympanic membrane temperature, bias and limits of agreement for SpotOn temperature were -0.28°C ± 0.61°C. The 3M SpotOn sensor using the ZHF method for patients aged over 80 years undergoing lower extremity surgery showed feasible measurement value and sensitivity.

Tumor therapeutic response monitored by telemetric temperature sensing, a preclinical study on immunotherapy and chemotherapy

Temperature in the body and the tumor reflects physiological and pathological conditions. A reliable, contactless, and simplistic measurement system can be used for long-term monitoring of disease progression and therapy response. In this study, miniaturized battery-free wireless chips implanted into growing tumors on small animals were used to capture both basal and tumor temperature dynamics. Three preclinical models: melanoma (B16), breast cancer (4T1), and colon cancer (MC-38), were treated with adoptive T cell transfer, AC-T chemotherapy, and anti-PD-1 immunotherapy respectively. Each model presents a distinctive pattern of temperature history dependent on the tumor characteristic and influenced by the administered therapy. Certain features are associated with positive therapeutic response, for instance the transient reduction of body and tumor temperature following adaptive T cell transfer, the elevation of tumor temperature following chemotherapy, and a steady decline of body temperature following anti-PD-1 therapy. Tracking in vivo thermal activity by cost-effective telemetric sensing has the potential of offering earlier treatment assessment to patients without requiring complex imaging or lab testing. Multi-parametric on-demand monitoring of tumor microenvironment by permanent implants and its integration into health information systems could further advance cancer management and reduce patient burden.

Assessment of Exercise-Associated Gastrointestinal Perturbations in Research and Practical Settings: Methodological Concerns and Recommendations for Best Practice

Strenuous exercise is synonymous with disturbing gastrointestinal integrity and function, subsequently prompting systemic immune responses and exercise-associated gastrointestinal symptoms, a condition established as "exercise-induced gastrointestinal syndrome." When exercise stress and aligned exacerbation factors (i.e., extrinsic and intrinsic) are of substantial magnitude, these exercise-associated gastrointestinal perturbations can cause performance decrements and health implications of clinical significance. This potentially explains the exponential growth in exploratory, mechanistic, and interventional research in exercise gastroenterology to understand, accurately measure and interpret, and prevent or attenuate the performance debilitating and health consequences of exercise-induced gastrointestinal syndrome. Considering the recent advancement in exercise gastroenterology research, it has been highlighted that published literature in the area is consistently affected by substantial experimental limitations that may affect the accuracy of translating study outcomes into practical application/s and/or design of future research. This perspective methodological review attempts to highlight these concerns and provides guidance to improve the validity, reliability, and robustness of the next generation of exercise gastroenterology research. These methodological concerns include participant screening and description, exertional and exertional heat stress load, dietary control, hydration status, food and fluid provisions, circadian variation, biological sex differences, comprehensive assessment of established markers of exercise-induced gastrointestinal syndrome, validity of gastrointestinal symptoms assessment tool, and data reporting and presentation. Standardized experimental procedures are needed for the accurate interpretation of research findings, avoiding misinterpreted (e.g., pathological relevance of response magnitude) and overstated conclusions (e.g., clinical and practical relevance of intervention research outcomes), which will support more accurate translation into safe practice guidelines.

Using the Bair Hugger™ temperature monitoring system in neck and chest regions: a pilot study

PURPOSE

Temperature monitoring in the perioperative periods is important in order to avoid both hyperthermia and hypothermia. In our pilot study, we evaluated the usefulness of Bair Hugger™ temperature monitoring system (BHTMS), a forehead deep temperature monitoring system, in the neck and chest under general anesthesia.

METHODS

After approval from the Sapporo Medical University Research Ethics Board, 30 female patients scheduled for laparoscopic surgery were enrolled in this study. Patients were divided into three groups, depending on the attachment regions of BHTMS sensor. Temperatures obtained from the three regions and each esophageal temperature (T_Eso) were monitored and analyzed.

RESULTS

A Bland-Altman plot showed that the mean bias between temperature obtained from the neck and T_Eso was + 0.05 °C above T_Eso (2SD ± 0.35 °C), and that between temperature obtained from the chest and T_Eso was - 0.55 °C above T_Eso (2SD ± 0.55 °C).

CONCLUSION

By using the BHTMS sensor in the neck region, it is possible to monitor core body temperature seamlessly and with high reliability. These results may suggest that the use of BHTMS has high versatility in measuring perioperative core body temperature.

TRIAL REGISTRATION

This study was approved by the Sapporo Medical University Research Ethics Board (2015: No. 262-149) and registered with UMIN Clinical Trial Registry ( UMIN000016802 Registered 15 March 2015).

Association between perioperative hypothermia and surgical site infection: A meta-analysis

BACKGROUND

A majority of reports in the past decade have demonstrated that perioperative hypothermia increases susceptibility to surgical site infection (SSI). However, in recent years, an increasing number of studies did not find an association between hypothermia and the risk of SSI. These contradictory results have given rise to a conflicting issue on whether perioperative hypothermia is associated with SSI risk in surgical patients.

METHODS

We examined the association between perioperative hypothermia and SSI incidence and then integrated available evidence by searching the databases, such as PubMed, Web of Science, Embase, and Cochrane library for potential papers from inception to April 2018. We included studies that reported original data or odds ratio (OR) with 95% confidence intervals (CIs) of the associations. Using fixed-effects models combined the OR with 95% CIs, randomized controlled trials and observational studies were analyzed, respectively, and cohort studies were further analyzed. Sensitivity analyses were performed by omitting each study iteratively, and publication bias was detected using Begg's tests.

RESULTS

We screened 384 studies, and identified 8 eligible studies, including 2 randomized controlled trials and 6 observational studies (1 case-control study and 5 cohort studies). The pooled OR results in the randomized controlled studies showed that perioperative hypothermia could increase the risk of SSI without heterogeneity (OR, 1.60; 95% CI, 1.14-2.23; I = 0.0%, P = .845). The fixed-effect meta-analysis indicated no association between perioperative hypothermia and SSI risk in observational studies (OR, 0.98; 95% CI, 0.96-1.01; I = 53.2%, P = .058). Furthermore, cohort studies were performed to pool OR by using the fixed-effect model, and the incorporated results also suggested a similar relationship (OR, 1.13; 95% CI, 0.97-1.33; I = 46.4%, P = .113).

CONCLUSION

The meta-analysis suggests that perioperative hypothermia is not associated with SSI in surgical patients. However, the 8 eligible studies were mostly cohort studies. Thus, further randomized controlled trials are required to confirm this finding.

Comparison of Forced-air Warming and Radiant Heating during Transurethral Prostatic Resection under Spinal Anaesthesia

Forced-air warming is commonly used to warm patients intraoperatively, but may not achieve normothermia during a short procedure. Comparative trials of a new radiant warming device in general anaesthesia (Suntouch™, Fisher and Paykel, Auckland, New Zealand) have had conflicting results. We conducted a randomized controlled trial to compare the efficacy and thermal comfort of the Suntouch™ radiant warmer and forced-air warming in patients at high risk of hypothermia during neuraxial blockade. With ethics committee approval, 60 patients having transurethral resection of the prostate under spinal were randomized to either radiant warming or forced-air warming. All intravenous and irrigation fluids were warmed but pre-warming was not used. The final intraoperative rectal temperatures for the radiant warming and forced-air warming groups were 36.1°C and 36.4°C respectively (P=0.03). A large proportion of patients in both groups (46% and 33% respectively, P=0.3) were hypothermic (<36°C) on arrival in the post-anaesthesia care unit. No other patient variables were significantly different. Neither warming device reliably prevented hypothermia, although forced-air warming was slightly superior.

Identifying Critical Design Parameters for Improved Body Temperature Measurements: A Clinical Study Comparing Transient and Predicted Temperature Measurements

Readily available store brand, or “home,” thermometers are used countless times in the home and clinic as a first diagnostic measure of body temperature. Measurement inaccuracies may lead to unnecessary medical visits or medication (false positives), or, potentially worse, lack of intervention when a person is truly sick (false negatives). A critical first step in the design process is to determine the shortcomings of the existing designs. For this project, we evaluated the accuracy of three currently available store brand thermometers in a pediatric population. The accuracies of the thermometers were assessed by comparing their body temperature predictions to those measured by a specially designed and calibrated and fast-responding reference thermometer. The reference thermometer was placed at the measurement site simultaneously with the store brand thermometer and recorded the temperature at the measurement site continuously. More than 300 healthy or sick pediatric subjects were enrolled in this study. Temperatures were measured at both the oral and axillary (under the arm) sites. The store brand thermometer measurements characteristically deviated from the reference thermometer temperature after 120 s, and the deviations did not follow a consistent pattern. The Brand C thermometers had the greatest deviations of up to 3.7 °F (2.1 °C), while the Brand A thermometers had the lowest deviations; however, they still deviated by up to 1.9 °F (1.1 °C). The data showed that the tested store brand thermometers had lower accuracy than the ±0.2 °F (0.1 °C) indicated in their Instructions for Use. Our recorded reference (transient) data showed that there was a wide variation in the transient temperature profiles. The store brand thermometers tested stated in their documentation that they are able to predict a body temperature based on transient temperature values over the first 5–10 s of measurements, implying that they use an embedded algorithm to extrapolate to the steady-state temperature. Significant deviations from the maximum temperature after time t = 4.6t0.63 illustrated that the transient temperature profiles may not be represented by an exponential function with a single time constant, t0.63. The accuracy of those embedded algorithms was not confirmed by our study, since the predicted body temperatures do not capture the large variations observed over the initial 10 s of the measurements. A thermometer with an error of several degrees Fahrenheit may result in a false positive or negative diagnosis of fever in children. The transient temperature measurements from our clinical study represent unique and critical data for helping to design the next generation of readily available, highly accurate, home thermometers.

Comparative study between Dexmedetomidine and Ondansteron for prevention of post spinal shivering. A randomized controlled trial

Background

Regional anesthesia could affect the homeostatic system functions resulting frequently in perioperative hypothermia and consequently shivering. The objective of this trial was to evaluate the efficacy of dexmedetomidine and ondansetron to reduce the incidence and severity of shivering after intrathecal blocks.

Methods

This randomized placebo-controlled trial included 120 patients allocated equally in three groups. All patients were anesthetized by standard intrathecal blocks for surgical procedure at lower half of the body and received one of the study drugs intravenously (IV) according to the group assignments. Group S patients (placebo) were administered saline, Group O (ondansetron) were given 8 mg ondansetron, and Group D (dexmedetomidine) were given 1 μg/kg of dexmedetomidine. Shivering incidence and scores, sedation scores, core body temperature, hemodynamic variables, and incidence of complications (nausea, vomiting, hypotension, bradycardia, over-sedation, and desaturation) were recorded.

Results

The incidence and 95% confidence interval (95% CI) of shivering in group S 57.5% (42.18–72.82%) was significantly higher than that of both group O 17.5% (5.73–29.27%), P < 0.001 and group D 27.5% (13.66–41.34%), P = 0.012. However, the difference in the incidence of shivering between group O and group D was comparable, P = 0.425. The sedation scores were significantly higher in group D than those of both group S and group O, P < 0.001. Sedation scores between group S and group O were comparable, P = 0.19. Incidences of adverse effects were comparable between the three groups.

Conclusion

Prophylactic administrations of dexmedetomidine or ondansetron efficiently decrease the incidence and severity of shivering after spinal anesthesia as compared to placebo without significant difference between their efficacies when compared to each other.

Trial registration

Pan African Clinical Trial Registry (PACTR) under trial number (PACTR201710002706318). 18-10-2017. ‘retrospectively registered’.

The incidence of mild hypothermia after total knee or hip arthroplasty: A study of 2600 patients

Hypothermia is associated with a higher risk of perioperative complications and occurs frequently after total joint arthroplasty (TJA). The incidence of hypothermia following total joint arthroplasty was assessed with its risk factors and its correlation with PJI. Correlation of hypothermia with age, gender, BMI, type of arthroplasty surgery, type of anesthesia, operation time, blood loss, date of surgery and PJI was evaluated in 2600 patients. Female gender and spinal anesthesia increased the risk for hypothermia whereas an increased BMI and surgery duration correlated decreased the risk of hypothermia. The incidence of hypothermia decreased over time without a correlation with PJI.

Effects of Thermal Protection in Patients Undergoing Body Contouring Procedures: A Controlled Clinical Trial

BACKGROUND

Hypothermia is common in many plastic surgery procedures, but few measures to prevent its occurrence are taken.

OBJECTIVES

This study evaluated the effect of hypothermia in patients undergoing plastic surgery procedures and the effect of utilizing simple and inexpensive measures to prevent patient hypothermia during surgery.

METHODS

A randomized controlled clinical trial was performed among 3 groups of patients who underwent body contouring surgery for longer than 3.5 hours. In group 1, no protective measures were taken to prevent hypothermia; in group 2, maneuvers were applied intraoperatively for the duration of the entire surgical procedure; and in group 3, measures were taken preoperatively and intraoperatively. The results were quantified and analyzed through a bivariate analysis, including degree of hypothermia, anesthesia recovery time, time spent in the recovery area, intensity of pain, cold perception, response to opioids, and nausea.

RESULTS

There were 122 patients included in the study: 43 in group 1, 39 in group 2, and 40 in group 3. All patients in group 1 had a higher degree of hypothermia, longer recovery time from anesthesia, longer overall recovery time, increased pain, increased feeling of cold, and more nausea. These patients also required a greater amount of opioids compared with the patients in groups 2 and 3. Many of the results were statistically significant.

CONCLUSIONS

The adoption of simple and inexpensive measures before and during plastic surgery can prevent patient hypothermia during the procedures, leading to a shorter anesthesia recovery time and avoiding the undesirable effects associated with hypothermia. In addition, these measures may have significant economic savings.

LEVEL OF EVIDENCE 2

Ice slurry ingestion reduces human brain temperature measured using non-invasive magnetic resonance spectroscopy

We previously reported that ice slurry ingestion reduced forehead skin temperature, thereby potentially reducing brain temperature (T_brain). Therefore, in the current study, we investigated the effect of ice slurry ingestion on T_brain using proton magnetic resonance spectroscopy, which is a robust, non-invasive method. Eight male participants ingested 7.5 g/kg of either a thermoneutral drink (37 °C; CON) or ice slurry (-1 °C; ICE) for about 5 min following a 15-min baseline period. Then, participants remained at rest for 30 min. As physiological indices, T_brain, rectal temperature (T_re), mean skin temperature, nude body mass, and urine specific gravity were measured. Subjective thermal sensation (TS) and thermal comfort (TC) were measured before and after the experiment. T_brain and T_re significantly reduced after ingestion of ICE compared with after ingestion of CON, and there was a significant correlation between T_brain and T_re. The other physiological indices were not significantly different between beverage conditions. TS and TC were significantly lower with ICE than with CON (p < 0.05). These results indicate that ice slurry ingestion can cool the brain, as well as the body's core.

Development of a method for estimating oesophageal temperature by multi-locational temperature measurement inside the external auditory canal

We aimed to develop a practical method to estimate oesophageal temperature by measuring multi-locational auditory canal temperatures. This method can be applied to prevent heatstroke by simultaneously and continuously monitoring the core temperatures of people working under hot environments. We asked 11 healthy male volunteers to exercise, generating 80 W for 45 min in a climatic chamber set at 24, 32 and 40 °C, at 50% relative humidity. We also exposed the participants to radiation at 32 °C. We continuously measured temperatures at the oesophagus, rectum and three different locations along the external auditory canal. We developed equations for estimating oesophageal temperatures from auditory canal temperatures and compared their fitness and errors. The rectal temperature increased or decreased faster than oesophageal temperature at the start or end of exercise in all conditions. Estimated temperature showed good similarity with oesophageal temperature, and the square of the correlation coefficient of the best fitting model reached 0.904. We observed intermediate values between rectal and oesophageal temperatures during the rest phase. Even under the condition with radiation, estimated oesophageal temperature demonstrated concordant movement with oesophageal temperature at around 0.1 °C overestimation. Our method measured temperatures at three different locations along the external auditory canal. We confirmed that the approach can credibly estimate the oesophageal temperature from 24 to 40 °C for people performing exercise in the same place in a windless environment.

The accuracy of a disposable noninvasive core thermometer

PURPOSE

Perioperative hypothermia is still a common occurrence, and it can be difficult to measure a patient's core temperature accurately, especially during regional anesthesia, with placement of a laryngeal mask airway device, or postoperatively. We evaluated a new disposable double-sensor thermometer and compared the resulting temperatures with those of a distal esophageal thermometer and a bladder thermometer in patients undergoing general and regional anesthesia, respectively. Furthermore, we compared the accuracy of the thermometer between regional and general anesthesia, since forehead microcirculation might differ between the two types of anesthesia.

METHODS

We assessed core temperature in 36 general anesthesia patients and 20 patients having regional anesthesia for orthopedic surgery. The temperatures obtained using the double-sensor thermometer were compared with those obtained with the distal esophageal thermometer in the general anesthesia population and those obtained with the bladder thermometer in regional anesthesia patients.

RESULTS

In our general anesthesia patients, 90% (95% confidence interval [CI] 85 to 95) of all double-sensor values were within 0.5°C of esophageal temperatures. The average difference (bias) between the esophageal and double-sensor temperatures was -0.01°C. In patients undergoing regional anesthesia 89% (95% CI 80 to 97) of all double-sensor values were within 0.5°C of bladder temperatures. The average difference (bias) between the bladder and double-sensor temperatures was -0.13°C, limits of agreement were -0.65 to 0.40°C.

CONCLUSIONS

In a perioperative patient population undergoing general or regional anesthesia, the accuracy of the noninvasive disposable double-sensor thermometer is comparable with that of the distal esophageal and bladder thermometers in routine clinical practice. Furthermore, the sensor performed comparably in patients undergoing regional and general anesthesia.

Perioperative management of a patient scheduled for bilateral hand transplant

The perioperative management of a patient receiving a bilateral hand transplant is presented. The anesthetic management required careful fluid administration, homeothermic temperature maintenance, and postoperative analgesia. The role of different anesthesia subspecialties is highlighted.

[Accuracy, precision, and validity of fever detection using non-invasive temperature measurement in adult coronary care unit patients with pulmonary catheters]

PURPOSE

To investigate the accuracy, precision and validity of fever detection of tympanic membrane (TM), temporal artery (TA) and axillary temperature (AT) compared with pulmonary artery temperature (PA).

METHODS

Repeated-measures design was conducted for one year on 83 adult cardiac care unit patients with pulmonary artery catheters after open heart surgery. Sequential temperature measurements were taken three times at 20-minute intervals. Accuracy, precision, repeatability, and validity of fever detection were analyzed.

RESULTS

Mean pulmonary artery temperature was 37.04°C (SD 0.70°C). The mean (SD) offsets from PA, with the mean reflecting accuracy and SD reflecting precision, were -1.31°C (0.75°C) for TA, -0.20°C (0.24°C) for TM, and -0.97°C (0.64°C) for AT. Percentage of pairs with differences within ±0.5°C was 9.6% for TA, 19.7% for AT, and 91.6% for TM. Repeated measurements with all three methods had mean SD values within 0.04°C. Sensitivity, specificity, and positive and negative predictive values of tympanic measurements were 0.76, 1.0, and 1.0, and 0.90, respectively.

CONCLUSION

Results show that TM best reflects PA, and is most consistent, accurate, and precise. AT tends to underestimate PA, and TA is least accurate and precise. Therefore tympanic membrane measurement is a reliable alternative to other non-invasive methods of measuring temperatures.

Outcome of a strategy to reduce surgical site infection in a tertiary-care hospital

BACKGROUND

Surgical site infection (SSI) is a preventable complication. Achieving a zero SSI rate for all clean operations should be the goal of all surgeons.

AIM

We aimed to reduce our SSI rate by 50% for patients undergoing elective gastrointestinal and hernia operations.

METHODS

The study was conducted in a tertiary-care hospital department of surgery from January 2006 to December 2007 for all clean and clean-contaminated elective gastrointestinal and hernia operations. Four interventions targeted at reducing SSI were implemented in January 2006: Use of clippers instead of shavers for surgical site hair removal; standardized prophylactic antibiotic regimen and antibiotic administration within 30 min before incision; standardized glucose monitoring for diabetics; and maintenance of postoperative normothermia. Prospective data were collected and compared with historical data from January to December 2005.

RESULTS

A total of 2,408 patients underwent elective gastrointestinal and hernia operations from January 2006 to December 2007. After implementation, we were able to achieve 91%, 87%, 89%, and 76% overall compliance with the respective interventions, but postoperative normothermia was achieved in only 44% of our patients. With the bundle of interventions, our overall SSI rate was reduced from 3.1% to 0.5% (p < 0.001), an 84% reduction within two years. The incidence of SSI was 1.7% in colorectal operations, 1.2% in upper gastrointestinal operations, 0.3% in hepatopancreaticobiliary operations, and zero in inguinal and ventral hernia operations. The estimated cost saving for both the patients and the hospital was S$208,562 (US$147,967).

CONCLUSIONS

Surgical site infections could be reduced with the bundle of interventions. With these encouraging results, the good practices should be sustained and promulgated. Such a SSI prevention program must be embedded in the work processes for all surgical disciplines.

Prevention of inadvertent perioperative hypothermia

All patients undergoing surgery are at risk of developing hypothermia; up to 70% develop hypothermia perioperatively. Inadvertent hypothermia is associated with complications such as impaired wound healing, increased blood loss, cardiac arrest and increased risk of wound infection. Anaesthesia increases the risk as the normal protective shivering reflex is absent. Ambient temperature also has a major effect on the patient's body temperature. Prevention of hypothermia not only reduces the incidence of complications, but patients also experience a greater level of comfort, and avoid postoperative shivering and the unpleasant sensation of feeling cold. Nurses should be aware of the risks of hypothermia so that preventative interventions can be employed to minimize the risk of hypothermia. Preoperative assessment is essential to enable identification of at-risk patients. Simple precautionary measures initiated by nurses can considerably reduce the amount of heat lost, minimize the risk of associated complications and ultimately improve patients' short- and long-term recovery. Minimizing skin exposure, providing adequate bed linen for the transfer to theatre and educating patients about the importance of keeping warm perioperatively are all extremely important. It is also worth considering using forced-air warmers preoperatively as research suggests that initiating active warming preoperatively may be successful in preventing hypothermia during the perioperative period.

Factors associated to the development of hypothermia in the intraoperative period

This study aimed to assess factors associated to body temperature changes intraoperatively in patients undergoing elective surgery. A prospective study including 70 patients was carried out in a charity hospital. A data collection instrument was developed and its face and content validity was established. The variables measured were operating room temperature and humidity and patient body temperature at different times. In the multivariate linear regression, the variables type of anesthesia, duration of anesthesia, body mass index, and operating room temperature were directly associated to mean body temperature. Nurses are responsible for planning and implementing effective interventions that can contribute to minimize costs and most importantly reduce hypothermia complications.

Accuracy and precision of a novel non-invasive core thermometer

BACKGROUND

Accurate measurement of core temperature is a standard component of perioperative and intensive care patient management. However, core temperature measurements are difficult to obtain in awake patients. A new non-invasive thermometer has been developed, combining two sensors separated by a known thermal resistance ('double-sensor' thermometer). We thus evaluated the accuracy of the double-sensor thermometer compared with a distal oesophageal thermometer to determine if the double-sensor thermometer is a suitable substitute.

METHODS

In perioperative and intensive care patient populations (n=68 total), double-sensor measurements were compared with measurements from a distal oesophageal thermometer using Bland-Altman analysis and Lin's concordance correlation coefficient (CCC).

RESULTS

Overall, 1287 measurement pairs were obtained at 5 min intervals. Ninety-eight per cent of all double-sensor values were within +/-0.5 degrees C of oesophageal temperature. The mean bias between the methods was -0.08 degrees C; the limits of agreement were -0.66 degrees C to 0.50 degrees C. Sensitivity and specificity for detection of fever were 0.86 and 0.97, respectively. Sensitivity and specificity for detection of hypothermia were 0.77 and 0.93, respectively. Lin's CCC was 0.93.

CONCLUSIONS

The new double-sensor thermometer is sufficiently accurate to be considered an alternative to distal oesophageal core temperature measurement, and may be particularly useful in patients undergoing regional anaesthesia.

Thermoregulatory management for mild therapeutic hypothermia

In recent years the use of mild therapeutic hypothermia as a means of neuroprotection has become an important concept for treatment after cerebral ischemic hypoxic injury. Mild therapeutic hypothermia has been shown to improve outcome after out-of-hospital cardiac arrest, and many studies suggest a beneficial effect of mild therapeutic hypothermia on patient outcome after traumatic brain injury, cerebrovascular damage and neonatal asphyxia. This review article explores the numerous possibilities and methods for the induction of mild therapeutic hypothermia, reviews thermoregulatory management during maintenance and discusses associated risks and complications.

Infrared tympanic thermography as a substitute for a probe in the evaluation of ear temperature for post-mortem interval determination: a pilot study

Reported methods which have been used to measure tympanic temperatures on cadavers up to now are quite invasive. They involve the use of a probe which can perforate the tympanic membrane and frequently causes bleeding from the ear. For this reason a non traumatic method for estimating tympanic temperature should be applied. Infrared tympanic thermometry seems to be a plausible option. Reliability of infrared tympanic thermometry (ITT) has been largely assessed on living individuals but only one author up to now has assessed its applicability for post-mortem interval determination. Thus the authors set out to test the difference between ear temperatures taken with a probe vs. ITT, differences between left and right ear and reproducibility of measurements of ITT. The aim of the study was to verify whether ITT could be a plausible option for measuring ear temperature for PMI estimation. Ear temperatures were taken on 25 cadavers (15 males, 10 females). Temperatures were taken alternately by similarly trained personnel by two technical methods (Checktemp 1 thermocouple probe and First Temp Genius infrared thermometer) for a total of 93 measurements. Statistical analysis of the data was performed using SAS statistical software. The range of temperature measured was from 20 to 28 degrees C, statistical analysis revealed no differences within the two technical methods, both for right and left ear (ITT: 22.33+/-0.35 vs. probe: 23.08+/-0.25; P=0.087). The study shows the ITT method can be considered as a possible alternative to the probe for measuring ear temperative and further studies should be considered.

Combination of thoracic epidural anesthesia does not always induce hypothermia during general anesthesia

The combination of general anesthesia and epidural anesthesia has been considered to worsen the degree of hypothermia. However, epidural anesthesia reduces cardiac output, which may prevent redistribution hypothermia. Twenty-four patients undergoing gynecologic surgery were randomly assigned to one of two groups: recipients of epidural injection of 1% ropivacaine and general anesthesia (epidural and general group, n=12) and recipients of epidural injection of saline and general anesthesia (general group, n=12). Fifteen minutes after epidural injection of 12 mL of 1% ropivacaine (epidural and general group) or saline (general group), general anesthesia was induced with propofol, and tracheal intubation was facilitated with vecuronium. Anesthesia was maintained with 35% oxygen and 0.4% to 2% isoflurane with a nitrous oxide mixture. Tympanic (core), forearm, and fingertip temperatures were recorded before the epidural injection, just before induction of general anesthesia, just after tracheal intubation, and every 15 minutes up to 90 minutes after tracheal intubation. The core temperature was significantly higher in the epidural and general group than in the general group from 30 to 90 minutes after tracheal intubation. Epidural anesthesia with 1% ropivacaine may prevent redistribution hypothermia during general anesthesia for gynecologic surgery.

Temporal Artery Versus Bladder Thermometry During Perioperative and Intensive Care Unit Monitoring

BACKGROUND

Core temperature measurements are an important component of perioperative patient monitoring. It is fairly easy to obtain core temperature measurements invasively in anesthetized patients. However, such measurements are more difficult to obtain noninvasively in awake patients. Recently, a new version of a temporal artery thermometer for noninvasive core temperature measurements (TemporalScanner TAT-5000) was introduced with accuracy and precision advertised as being comparable to invasive core temperature measurements. In this study, we sought to determine if this new thermometer is an acceptable substitute for invasive bladder temperature measurement.

METHODS

In 35 patients undergoing neurosurgical interventions and 35 patients in the neurosurgical intensive care unit, measurements from the temporal artery thermometer were compared with those from a bladder thermometer. Four measurements were obtained from each patient.

RESULTS

Overall 280 measurement pairs were obtained. The mean bias between the methods was 0.07 degrees C +/- 0.79 degrees C; the limits of agreement were approximately 3 times greater than the a priori defined limit of +/-0.5 degrees C (-1.48 to 1.62). The sensitivity for detecting fever (core temperature >37.8 degrees C) using the temporal artery thermometer was 0.72, and the specificity was 0.97. The positive predictive value for fever was 0.89; the negative predictive value was 0.94. The sensitivity for detecting hypothermia (core temperature <35.5 degrees C) was 0.29, and the specificity was 0.95. The positive predictive value for hypothermia was 0.31, and the negative predictive value was 0.95.

CONCLUSIONS

The results of this study do not support the use of temporal artery thermometry for perioperative core temperature monitoring; the temporal artery thermometer does not provide information that is an adequate substitute for core temperature measurement by a bladder thermometer.

Accuracy and Precision of Noninvasive Temperature Measurement in Adult Intensive Care Patients

Background Research on the accuracy and precision of noninvasive methods of measuring body temperature is equivocal.

Objectives To determine accuracy and precision of oral, ear-based, temporal artery, and axillary temperature measurements compared with pulmonary artery temperature.

Methods Repeated-measures design conducted for 6 months. Sequential temperature measurements on the same side of the body were obtained within 1 minute, with measurements repeated 3 times at 20-minute intervals. Accuracy, precision, and confidence limits were analyzed.

Results In 60 adults with cardiopulmonary disease and a pulmonary artery catheter, mean pulmonary artery temperature was 37.1°C (SD 0.6°C, range 35.3°C–39.4°C). Mean (SD) offset from pulmonary artery temperature (with the mean reflecting accuracy and SD reflecting precision) and confidence limits were 0.09°C (0.43°C) and −0.75°C to 0.93°C for oral measurements, −0.36°C (0.56°C) and −1.46°C to 0.74°C for ear measurements, −0.02°C (0.47°C) and −0.92°C to 0.88°C for temporal artery measurements, and 0.23°C (0.44°C) and −0.64°C to 1.12°C for axillary measurements. Percentage of pairs with differences greater than ±0.5°C was 19% for oral, 49% for ear, 20% for temporal artery, and 27% for axillary measurements. Intubation increased oral measurements compared with pulmonary artery temperatures (mean difference 0.3°C, SD 0.3°C, P = .001).

Conclusions Oral and temporal artery measurements were most accurate and precise. Axillary measurements underestimated pulmonary artery temperature. Ear measurements were least accurate and precise. Intubation affected the accuracy of oral measurements; diaphoresis and airflow across the face may affect temporal artery measurements.

Survey on intraoperative temperature management in Europe

BACKGROUND AND OBJECTIVES

Inadvertent perioperative hypothermia causes serious morbidity in surgical patients. However, recent reports suggest that patients might still be hypothermic after elective surgery. We thus surveyed intraoperative temperature monitoring and management practices in Europe.

METHODS

Postal survey of 801 representative hospitals from 17 European countries on the same day. The questions addressed the number of surgical procedures and type of anaesthesia performed, mode and site of temperature monitoring and method of patient warming. Mean and standard error of the mean or count and percentage were calculated. The t-test or contingency table analysis with the Fisher's exact test were used.

RESULTS

Eight thousand and eighty-three surgical procedures were assessed from 316 responding hospitals (39.4%). Overall, patient temperature monitored in 19.4% and 38.5% of the patients were actively warmed. Under general anaesthesia, body temperature was monitored in 25% and during regional anaesthesia in 6%, P = 0.0005. Nasopharyngeal temperature was most often taken under general anaesthesia, while tympanic temperature was preferred during regional anaesthesia. Under general anaesthesia, 43% of patients were actively warmed as compared to 28% with regional anaesthesia, P = 0.0005. Forced-air warming was the method of choice for both general and regional anaesthesia.

CONCLUSIONS

Intraoperative temperature monitoring is still uncommon and hence active patient warming is not a standard of care in Europe. Awareness of perioperative hypothermia is critical to its prevention, and thus temperature monitoring is a pre-requisite. The objective is to maintain normothermia in patients throughout surgery. A European practice guideline for perioperative patient temperature management is warranted.

The accuracy of a new infrared ear thermometer in patients undergoing cardiac surgery

PURPOSE

To evaluate the equivalency of the prototype of a new infrared ear thermometer (IRT 4000) in comparison to the temperature measurements of a pulmonary artery catheter (PAC) and a continual contact probe on the tympanic membrane.

METHODS

After approval by the local Ethics Committee, 26 (six female and 20 male) patients undergoing elective cardiac surgery were included in a single center open trial. During surgery, temperature measurements were recorded with the IRT 4000 in the left ear, and with a tympanic contact probe in the right ear, as well as with a PAC as reference. Measurements with the infrared ear thermometers and continual PAC values were recorded every six minutes.

RESULTS

The average temperature measured with the IRT 4000 was 0.08 degrees C above the temperature of the PAC (95% confidence interval from -0.44-0.61 degrees C).

CONCLUSION

Infrared ear thermometers 4000 temperature readings accurately reflect body core temperature and correlate well with the invasive PAC. Infrared ear thermometers may present a clinically useful alternative to the pulmonary artery thermometry for the measurement of core temperature in the perioperative setting or in the intensive care unit.

Is Postanesthesia Care Unit Length of Stay: Increased in Hypothermic Patients?

Inadvertent hypothermia is one of the most common complications experienced by surgical patients who are transferred to the postanesthesia care unit (PACU). Appropriate pacu length of stay (LOS) is defined as the time required for a patient to achieve a physiologically stable condition after anesthesia administration. In studies measuring appropriate LOS, patients who arrived hypothermic in the PACU had longer stays than those who arrived normothermic. The aims of this study were to determine whether the actual and appropriate LOS in the PACU differs between hypothermic and normothermic patients and to identify differences between subgroups of patients according to age, gender, and type of anesthesia administered.

Older people and hypothermia: the role of the anaesthetic nurse

Older clients are at increased risk during surgical intervention because of age-related system changes and comorbid conditions. However, recent advances in surgical and anaesthetic techniques, together with modern monitoring technology and the proliferation of ambulatory surgery, have reduced mortality in older patients undergoing surgery. Nevertheless, inadvertent hypothermia in older clients remains problematic. Therefore, an understanding of specific diseases prevalent in old age, coupled with a comprehensive knowledge of the physiological impact of ageing in all body systems, underpins the role of the anaesthetic nurse.

Using Low-Tech Thermometers to Measure Body Temperatures in Older Adults: A Pilot Study

Many studies compare temperature sites and equipment, but none have examined the validity of groin temperatures in older adults, or compared Galinstan-in-glass with mercury-in-glass thermometer products. The purpose of this pilot study was to collect and analyze data related to human body temperature monitoring in adults 50 and older. Groin temperature (Tg) was compared with simultaneous oral (To) and rectal (Tr) temperature measures for each participant using two thermometer types (i.e., mercury-in-glass and Galinstan-in-glass). A high degree of correlation was found among sites and devices. Further study will be needed to include a larger, more diverse study population for the Galinstan non-mercury thermometer devices. Further study will also be needed to assess various temperature assessment sites for a larger, more diverse study population (e.g., age, gender, race, disease state).

Spinal anaesthesia in paediatrics

The use of spinal anaesthesia in children has been primarily limited to situations in which general anaesthesia was considered to pose an excessive risk. The ex-premature infant and the neurologically impaired child account for the majority of spinal anaesthetics used today. Spinal anaesthesia, compared with general anaesthesia, in the ex-premature infant undergoing inguinal hernia repair has decreased postoperative respiratory complications (e.g. apnoeic events, prolonged mechanical ventilation). Hyperbaric tetracaine and bupivacaine solutions are the local anaesthetics of choice. Haemodynamic stability is well preserved in neonates having spinal anaesthesia. Advances in spinal needle design have decreased the incidence of postdural puncture headache (PDPH). Catastrophic events have occurred with neuraxial techniques. Care must be taken in evaluating the relative risks of anaesthetic approaches in infants and children.

Hypothermia during head and neck surgery

OBJECTIVE

To determine the predictors and incidence of hypothermia in patients undergoing head and neck surgery.

STUDY DESIGN

Retrospective analysis.

METHODS

Patients were either not warmed (n = 43) or actively warmed with forced-air warming (n = 25). Clinical variables that were assessed as predictors of core body temperature included age, body mass, duration of procedure, estimated blood loss, amount of intravenous fluids administered, and the use of forced-air warming. The incidence of severe intraoperative hypothermia and potential hypothermia-related complications was also examined.

RESULTS

The study demonstrated that advanced age is a risk factor for hypothermia and decreased body mass is associated with lower final body temperatures in the groups of patients that was not warmed. After adjusting for differences in the ages and weights between the two groups, the mean core body temperature was found to be 0.4 degrees C lower in the patients who were not warmed. Severe intraoperative hypothermia occurred in 5 of 38 patients (11.6%) who were not warmed and 2 of 23 patients (8.0%) who were warmed. The complications associated with hypothermia included delayed time to extubation, the development of neck seromas, and flap dehiscence.

CONCLUSIONS

Patients undergoing head and neck surgery are at risk for the development of intraoperative hypothermia and require careful temperature monitoring. Elderly patients and patients with low body mass are more prone to develop low intraoperative core body temperatures. Active warming with forced-air warmers should be considered for patients at risk for intraoperative hypothermia and for patients who develop hypothermia intraoperatively, to avoid hypothermia-related complications.

Core temperature measurement: methods and current insights

Climatic injuries, including hypothermia, hyperthermia and heat stroke, are common in many sports activities. Body core temperature (T(c)) measurement for the sportsperson can influence individual performance and may help to prevent injuries. Monitoring internal body T(c) accurately requires invasive methods of measurement. The mercury thermometer, most commonly used to measure oral temperature (T(oral)), has been almost exclusively the only instrument for measuring T(c) since the 18th century. Rectal (T(re)) and oesophageal temperatures (T(oes)) have been the most preferred measurement sites employed in thermoregulatory investigations. However, these measurement sites (T(re), T(oes), T(oral)), and the methods used to measure T(c) at these sites, are not convenient. T(oral) measurements are not always possible or accurate. T(oes) is undesirable because of the difficulty of inserting the thermistor, irritation to nasal passages and general subject discomfort. T(re) is not suitable under many circumstances as it is labour intensive and has a prolonged response time. However, T(re) remains the most accurately available method for monitoring T(c) in thermal illness that occurs during sports activities. In addition, T(re) and T(oes) require wire connections between the thermistor and the monitoring device. The purpose of this paper is to review the various existing methods of T(c) measurements in order to focus on the breakthrough needed for a simple, noninvasive, universally used device for T(c) measurement which is essential for preventing climatic injuries during sports events.

Infrared tympanic thermometer can accurately measure the body temperature in children in an emergency room setting

OBJECTIVE

The objective in this study was to compare the accuracy of the tympanic membrane infrared thermometer with the other conventional temperature measurement options.

METHODS

One hundred and ten randomly selected pediatric patients who admitted to our emergency room were included in the study. Each child underwent simultaneous temperature measurement via rectum, axilla, and external auditory canal. The rectal and axillary measurements were performed using conventional mercury in glass thermometers. The aural measurement was performed using the non-contact infrared thermometer (Braun ThermoScan IRT 1020, Germany).

RESULTS

On aural measurement, the results of both ears as well as the first, second and third measurements were similar (P<0.01). The mean results of the axillary, rectal and tympanic temperature measurements were 37.46+/-1, 38.18+/-1, and 38.01+/-1.1, respectively. The mean axillary temperature was 0.72 degrees C lower than the mean rectal temperature, and 0.55 degrees C lower than the tympanic temperature. The difference between the mean tympanic and rectal temperatures was 0.17 degrees C. The results of measurements via rectum, axilla and ear were similar (P<0.01).

CONCLUSION

In conclusion, it is apparent that each of the temperature measurement options has some advantages and disadvantages. An optimal thermometer should have the following features; accurate temperature measurement; ease of application in a short while; safety and absence of potential risks; and tolerability by the patient. Since the aural infrared thermometer meets these criteria, its use in the routine clinical practice appears to be advantageous rather than or complementary to the conventional methods.

The effects of urapidil on thermoregulatory thresholds in volunteers

In a previous study we have shown that the antihypertensive drug, urapidil, stops postanesthetic shivering. One possible mechanism in the inhibition of postanesthetic shivering by urapidil may be alterations in thermoregulatory thresholds. We therefore studied the effects of urapidil on vasoconstriction and shivering thresholds during cold-induced shivering in volunteers. Seven healthy male volunteers were cooled by an infusion of saline at 4 degrees C on two study days separated by 48 h. Thermoregulatory vasoconstriction was estimated using forearm minus fingertip skin-temperature gradients, and values exceeding 0 degrees C were considered to represent significant vasoconstriction. The rectal core temperatures at the beginning of shivering and at vasoconstriction were considered the thermoregulatory thresholds. Before cooling, either 25 mg of urapidil or placebo was administered randomly and blindly to each volunteer. When shivering occurred continuously for 10 min, another 25 mg of urapidil was administered IV to completely stop shivering. Urapidil led to a decrease in core temperature at vasoconstriction and shivering threshold by 0.4 degrees C plus/minus 0.2 degrees C (P < 0.001) and 0.5 degrees C plus/minus 0.3 degrees C (P < 0.01), respectively. Oxygen consumption increased during shivering by 70% plus/minus 30% (P < 0.01) in comparison with baseline and decreased levels after shivering stopped, despite the continued low core temperature. Our investigation shows that urapidil stops postanesthetic shivering by decreasing important thermoregulatory thresholds. This means that shivering, not hypothermia, is treated, and hypothermia will need more attention in the postanesthesia care unit.

IMPLICATIONS

In this study we show that the antihypertensive drug urapidil stops cold-induced shivering and decreases normal thermoregulatory responses, i.e., the thresholds for vasoconstriction and shivering, in awake volunteers.

Hypothermia After Vascular Surgery: Complications, Prevention, and Treatment

Virtually all anesthetics render patients poikilothermic and body temperature invariably decreases during surgery. Dur ing vascular occlusion and resulting ischemia to the brain, kidneys, and spinal cord, hypothermia is often beneficial by decreasing metabolic demands and protecting from injury. Residual hypothermia, however, in the postoperative period is rarely desirable and hypothermia-related complications are well-known. Even mild hypothermia can exacerbate the stress response by activation of the sympathetic nervous system, resulting in increased catecholamines, which can precipitate myocardial ischemia and cardiac morbidity. As little as 2°C of core hypothermia impairs coagulation and predisposes to postoperative bleeding, which is especially problematic in the presence of fresh vascular anastomoses. Hypothermia also slows emergence from general anesthesia by both pharmacokinetic and pharmacodynamic mecha nisms. In vascular surgery patients, body temperature should be carefully monitored and controlled with the same level of attention that is given to the other vital signs. By active cooling and warming at the appropriate perioperative timepoints, outcomes can be improved and morbidity re duced in patients undergoing vascular surgery. Copyright © 2000 by W.B. Saunders Company.