Intraoperative zero-heat-flux thermometry overestimates esophageal temperature by 0.26 °C: an observational study in 100 infants and young children

What is the minimum time interval for reporting of intraoperative core body temperature measurements in pediatric anesthesia? A secondary analysis

Given that perioperative normothermia represents a quality parameter in pediatric anesthesia, numerous studies have been conducted on temperature measurement, albeit with heterogeneous measurement intervals, ranging from 30 s to fifteen minutes. We aimed to determine the minimum time interval for reporting of intraoperative core body temperature across commonly used measurement intervals in children. Data were extracted from the records of 65 children who had participated in another clinical study and analyzed using a quasibinomial mixed linear model. Documented artifacts, like probe dislocations or at the end of anesthesia, were removed. Primary outcome was the respective probability of failing to detect a temperature change of 0.2 °C or more at any one measurement point at 30 s, one minute, two minutes, five minutes, ten minutes, and fifteen minutes, considering an expected probability of less than 5% to be acceptable. Secondary outcomes included the probabilities of failing to detect hypothermia (< 36.0 °C) and hyperthermia (> 38.0 °C). Following the removal of 4,909 exclusions, the remaining 222,366 timestamped measurements (representing just over 60 h of monitoring) were analyzed. The median measurement time was 45 min. The expected probabilities of failing to detect a temperature change of 0.2 °C or more were 0.2% [95%-CI 0.0-0.7], 0.5% [95%-CI 0.0-1.2], 1.5% [95%-CI 0.2-2.6], 4.8% [95%-CI 2.7-6.9], 22.4% [95%-CI 18.3-26.4], and 31.9% [95%-CI 27.3-36.4], respectively. Probabilities for the detection of hyperthermia (n = 9) were lower and omitted for hypothermia due to low prevalence (n = 1). In conclusion, the core body temperature should be reported at intervals of no more than five minutes to ensure the detection of any temperature change in normothermic ranges. Further studies should focus on hypothermic and hyperthermic ranges.

Accuracy of non-invasive core temperature monitoring in infant and toddler patients: a prospective observational study

PURPOSE

Careful perioperative temperature management is important because it influences clinical outcomes. In pediatric patients, the esophageal temperature is the most accurate indicator of core temperature. However, it requires probe insertion into the body cavity, which is mildly invasive. Therefore, a non-invasive easily and continuously temperature monitor system is ideal. This study aimed to assess the accuracy of Temple Touch Pro™ (TTP), a non-invasive temperature monitoring using the heat flux technique, compared with esophageal (Tesoph) and rectal (Trect) temperature measurements in pediatric patients, especially in infants and toddlers.

METHODS

This single-center prospective observational study included 40 pediatric patients (< 3 years old) who underwent elective non-cardiac surgery. The accuracy of TTP was analyzed using Bland-Altman analysis and compared with Tesoph or Trect temperature measurements. The error was within ± 0.5 °C and was considered clinically acceptable.

RESULTS

The bias ± precision between TTP and Tesoph was 0.09 ± 0.28 °C, and 95% limits of agreement were  - 0.48 to 0.65 °C (error within ± 0.5 °C: 94.0%). The bias ± precision between TTP and Trect was 0.41 ± 0.38 °C and 95% limits of agreement were  - 0.35 to 1.17 °C (error within ± 0.5 °C: 68.5%). In infants, bias ± precision with 95% limits of agreement were 0.10 ± 0.30 °C with  - 0.50 to 0.69 °C (TTP vs. Tesoph) and 0.35 ± 0.29 °C with  - 0.23 to 0.92 °C (TTP vs. Trect).

CONCLUSION

Core temperature measurements using TTP in infants and toddlers were more accurate with Tesoph than with Trect. In the future, non-invasive TTP temperature monitoring will help perioperative temperature management in pediatric patients.

Intraoperative zero-heat-flux thermometry overestimates nasopharyngeal temperature by 0.39 °C: an observational study in patients undergoing congenital heart surgery

During surgery for congenital heart disease (CHD) temperature management is crucial. Vesical (Tves) and nasopharyngeal (TNPH) temperature are usually measured. Whereas Tves slowly responds to temperature changes, TNPH carries the risk of bleeding. The zero-heat-flux (ZHF) temperature monitoring systems SpotOn™ (TSpotOn), and Tcore™ (Tcore) measure temperature non-invasively. We evaluated accuracy and precision of the non-invasive devices, and of Tves compared to TNPH for estimating temperature. In this prospective observational study in pediatric and adult patients accuracy and precision of TSpotOn, Tcore, and Tves were analyzed using the Bland-Altman method. Proportion of differences (PoD) and Lin´s concordance correlation coefficient (LCC) were calculated. Data of 47 patients resulted in sets of matched measurements: 1073 for TSpotOn vs. TNPH, 874 for Tcore vs. TNPH, and 1102 for Tves vs. TNPH. Accuracy was - 0.39 °C for TSpotOn, -0.09 °C for Tcore, and 0.07 °C for Tves. Precisison was between - 1.12 and 0.35 °C for TSpotOn, -0.88 to 0.71 °C for Tcore, and - 1.90 to 2.05 °C for Tves. PoD ≤ 0.5 °C were 71% for TSpotOn, 71% for Tcore, and 60% for Tves. LCC was 0.9455 for TSpotOn, 0.9510 for Tcore, and 0.9322 for Tves. Temperatures below 25.2 °C (TSpotOn) or 27.1 (Tcore) could not be recorded non-invasively, but only with Tves. Trial registration German Clinical Trials Register, DRKS00010720.

Preventing hypothermia in pediatric neurosurgery in Africa-A randomized controlled non-inferiority trial of insulation versus active warming

PURPOSE

The objective of this study was to compare the efficacy of a low-cost heat-preserving method in preventing intraoperative hypothermia with that of forced-air warming in a resource-limited setting.

METHODS

In this randomized controlled non-inferiority trial, we recruited children younger than 12 years scheduled for cranial neurosurgery in a large East-African hospital. Patients were block-randomized by age to intraoperative warming measures using Hibler's method (intervention) or warm air (comparator). Hibler's group patients were circumferentially wrapped in transparent plastic sheeting (providing a vapor-trap) over a layer of cotton blankets, then laid on an insulating foam mattress. Warm air group patients were treated with forced-air convection via an underlying Snuggle Warm™ Pediatric Full Body mattress. Allocated warming measures were initiated in the operating theatre and discontinued upon anesthesia emergence. Perioperative temperatures were measured using noninvasive forehead probes (SpotOn™). The primary outcome was incidence of hypothermia (core temperature < 36.0° for longer than 5 min). Our null hypothesis was that Hibler's method is inferior in efficacy to the warm air method by a margin exceeding 20%. Among secondary outcomes were duration of hypothermia as proportion of surgical duration, incidence of postoperative shivering and rescue measure requirements.

RESULTS

We analyzed data for 77 participants (Hibler's = 38; warm air = 39). There was no significant difference between the Hibler's and warm air arms of the study in the primary outcome of incidence of hypothermia (59.0% vs. 60.5% respectively; OR 1.07; 95% CI 0.43-2.65; p = .890). However, the risk difference (1.55%; 95% CI -0.20 to -0.24) exceeded the 0.2 margin and non-inferiority could not be declared. There was considerable need for rescue measures in both groups (71.1 0% vs. 69.2%; OR 1.09; 95% CI 0.41-2.90; p = .861). There was no statistically significant difference between groups for any prespecified secondary outcome.

CONCLUSION

Although perioperative core temperatures were not significantly different, we could not declare an inexpensive heat-preserving method non-inferior to warm air convection in preventing intraoperative hypothermia in children undergoing anesthesia for cranial neurosurgery in a resource-limited setting. The extensive need for rescue measures may have masked important differences.

TRIAL REGISTRATION

US National Institutes of Health Clinicaltrials.gov database (ID no. NCT02975817).

Accuracy of a Dual-Sensor Heat-Flux (DHF) Non-Invasive Core Temperature Sensor in Pediatric Patients Undergoing Surgery

Accurate temperature measurement is crucial for the perioperative management of pediatric patients, and non-invasive thermometry is necessary when invasive methods are infeasible. A prospective observational study was conducted on 57 patients undergoing elective surgery. Temperatures were measured using a dual-sensor heat-flux (DHF) thermometer (Tcore™) and a rectal temperature probe (TRec), and the agreement between the two measurements was assessed. The DHF measurements showed a bias of +0.413 °C compared with those of the TRec. The limits of agreement were broader than the pre-defined ±0.5 °C range (-0.741 °C and +1.567 °C). Although the DHF sensors tended to overestimate the core temperature compared to the rectal measurements, an error grid analysis demonstrated that 95.81% of the DHF measurements would not have led to a wrong clinical decision, e.g., warming or cooling when not necessary. In conclusion, the low number of measurements that would have led to incorrect decisions suggests that the DHF sensor can be considered an option for continuous temperature measurement when more invasive methods are infeasible.

Risk factors for intraoperative hypothermia in infants during general anesthesia: A retrospective study

This study aimed to determine the incidence and evaluate the risk factors and outcomes of intraoperative hypothermia (IH) during general anesthesia in infants. Retrospective analysis of prospectively collected data. A total of 754 infants younger than 1 year old who underwent surgery under general anesthesia were included. Intraoperative body temperature fluctuations, surgical and anesthetic data, postoperative complications, and infant outcomes were recorded. Logistic regression algorithms were used to evaluate potential risk factors. Among the 754 infants, 47.88% developed IH (<36 °C) and 15.4% of them experienced severe hypothermia (<35 °C). The average lowest temperature in hypothermia patients was 35.06 ± 0.69°C with a duration of 82.23 ± 50.59 minutes. Neonates tended to experience hypothermia (37.7% vs 7.6%, P < .001) and prematurity was more common in patients with IH (29.4% vs 16.8%, P < .001). Infants with hypothermia experienced a longer length of stay in the post anesthesia care units and intensive care units, postoperative hospitalizations, and tracheal extubation as well as a higher rate of postoperative hemorrhage than those with normothermia (all P < .05). Several factors were proved to be associated with an increased risk of IH after multivariate analysis: neonate (odds ratio [OR] = 3.685, 95% CI 1.839-7.382), weight (OR = 0.599, 95% CI 0.525-0.683), American society of anesthesiologists (OR = 3.418, 95% CI 2.259-5.170), fluid > 20 mL/kg (OR = 2.380, 95% CI 1.389-4.076), surgery time >60 minutes (OR = 1.785, 95% CI 1.030-3.093), and pre-warming (OR = 0.027, 95% CI 0.014-0.052). This retrospective study found that neonates, lower weight, longer surgery times, more fluid received, higher American society of anesthesiologists stage, and no pre-warming were all significant risk factors for IH during general anesthesia in infants.

Modeling iatrogenic intraoperative hyperthermia from external warming in children: A pooled analysis from two prospective observational studies

BACKGROUND

Maintenance of normothermia is an important quality metric in pediatric anesthesia. While inadvertent hypothermia is effectively prevented by forced-air warming, this therapeutic approach can lead to iatrogenic hyperthermia in young children.

AIMS

To estimate the influence of external warming by forced air on the development of intraoperative hyperthermia in anesthetized children aged 6 years or younger.

METHODS

We pooled data from two previous clinical studies. Primary outcome was the course of core temperature over time analyzed by a quadratic regression model. Secondary outcomes were the incidence of hyperthermia (body core temperature >38°C), the probability of hyperthermia over the duration of warming in relation to age and surface-area-to-weight ratio, respectively, analyzed by multiple logistic regression models. The influence of baseline temperature on hyperthermia was estimated using a Cox proportional hazards model.

RESULTS

Two hundred children (55 female) with a median age of 2.1 [1st -3rd quartile 1-4.2] years were analyzed. Mean temperature increased by 0.43°C after 1 h, 0.64°C after 2 h, and reached a peak of 0.66°C at 147 min. Overall, 33 children were hyperthermic at at least one measurement point. The odds ratios of hyperthermia were 1.14 (95%-CI: 1.07-1.22) or 1.13 (95%-CI: 1.06-1.21) for every 10 min of warming therapy in a model with age or surface-area-to weight ratio (ceteris paribus), respectively. Odds ratio was 1.33 (95%-CI: 1.07-1.71) for a decrease of 1 year in age and 1.63 (95%-CI: 0.93-2.83) for an increase of 0.01 in the surface-to-weight-area ratio (ceteris paribus). An increase of 0.1°C in baseline temperature increased the hazard of becoming hyperthermic by a factor of 1.33 (95%-CI: 1.23-1.43).

CONCLUSIONS

In children, external warming by forced-air needs to be closely monitored and adjusted in a timely manner to avoid iatrogenic hyperthermia especially during long procedures, in young age, higher surface-area-to-weight ratio, and higher baseline temperature.

Perioperative Hypothermia in Children

Background: First described by paediatric anaesthesiologists, perioperative hypothermia is one of the earliest reported side effects of general anaesthesia. Deviations from normothermia are associated with numerous complications and adverse outcomes, with infants and small children at the highest risk. Nowadays, maintenance of normothermia is an important quality metric in paediatric anaesthesia. Methods: This review is based on our collection of publications regarding perioperative hypothermia and was supplemented with pertinent publications from a MEDLINE literature search. Results: We provide an overview on perioperative hypothermia in the paediatric patient, including definition, history, incidence, development, monitoring, risk factors, and adverse events, and provide management recommendations for its prevention. We also summarize the side effects and complications of perioperative temperature management. Conclusions: Perioperative hypothermia is still common in paediatric patients and may be attributed to their vulnerable physiology, but also may result from insufficient perioperative warming. An effective perioperative warming strategy incorporates the maintenance of normothermia during transportation, active warming before induction of anaesthesia, active warming during anaesthesia and surgery, and accurate measurement of core temperature. Perioperative temperature management must also prevent hyperthermia in children.