Effect of a vapor barrier in combination with active external rewarming for cold-stressed patients in a prehospital setting: a randomized, crossover field study.

BACKGROUND: Use of a vapor barrier in the prehospital care of cold-stressed or hypothermic patients aims to reduce evaporative heat loss and accelerate rewarming. The application of a vapor barrier is recommended in various guidelines, along with both insulating and wind/waterproof layers and an active external rewarming device; however, evidence of its effect is limited. This study aimed to investigate the effect of using a vapor barrier as the inner layer in the recommended "burrito" model for wrapping hypothermic patients in the field. METHODS: In this, randomized, crossover field study, 16 healthy volunteers wearing wet clothing were subjected to a 30-minute cooling period in a snow chamber before being wrapped in a model including an active heating source either with (intervention) or without (control) a vapor barrier. The mean skin temperature, core temperature, and humidity in the model were measured, and the shivering intensity and thermal comfort were assessed using a subjective questionnaire. The mean skin temperature was the primary outcome, whereas humidity and thermal comfort were the secondary outcomes. Primary outcome data were analyzed using analysis of covariance (ANCOVA). RESULTS: We found a higher mean skin temperature in the intervention group than in the control group after approximately 25 min (p < 0.05), and this difference persisted for the rest of the 60-minute study period. The largest difference in mean skin temperature was 0.93 °C after 60 min. Humidity levels outside the vapor barrier were significantly higher in the control group than in the intervention group after 5 min. There were no significant differences in subjective comfort. However, there was a consistent trend toward increased comfort in the intervention group compared with the control group. CONCLUSIONS: The use of a vapor barrier as the innermost layer in combination with an active external heat source leads to higher mean skin rewarming rates in patients wearing wet clothing who are at risk of accidental hypothermia. TRIAL REGISTRATION: ClinicalTrials.gov identifier: NCT05779722.

Role of perfusion medium in rewarming machine perfusion from hypo- to normothermia.

BACKGROUND: Gradual warming up of cold stored organ grafts using a controlled machine perfusion protocol facilitates restitution of cellular homeostasis and mitigates rewarming injury by adapted increase of temperature and metabolism. The aim of the present study was to compare intra- and extracellular type perfusion media for the use in machine perfusion-assisted rewarming from hypo- to normothermia. METHODS: Rat livers were retrieved 20 min after cardiac arrest. After 18 h of cold storage (CS) with or without additional 2 h of rewarming machine perfusion from 8°C up to 35°C with either diluted Steen solution or with Belzer MPS, liver functional parameters were evaluated by an established ex vivo reperfusion system. RESULTS: Rewarming machine perfusion with either solution significantly improved graft performance upon reperfusion in terms of increased bile production, less enzyme release, and reduced lipid peroxidation compared to CS alone. Cellular apoptosis (release of caspase-cleaved keratin 18) and release of tumor necrosis factor were only reduced significantly after machine perfusion with Belzer MPS. Histological evaluation did not disclose any major morphological damage in any of the groups. CONCLUSION: Within the limitation of our model, the use of Belzer MPS seems to be an at least adequate alternative to a normothermic medium like Steen solution for rewarming machine perfusion of cold liver grafts.

[Reducing the Incidence of Postoperative Hypothermia in Patients Undergoing Robotic-Assisted Mitral Valve Surgery].

BACKGROUND & PROBLEMS: Post-operation hypothermia tends to induce complications. Sixty percent of robotic-assisted mitral valve surgery patients experienced hypothermia while admitted to our intensive care unit (ICU), resulting in prolonged ICU stays and 57% (eight) of those patients with hypothermia also experiencing cardiac arrhythmia. The causes of hypothermia in our ICU included low temperature in the operating room, delayed initiation of blanket coverage after surgery, and lack of postoperative thermal blankets, insufficient cardiopulmonary bypass rewarming time, cold ICU beds, lack of in-service training for hypothermia, and lack of procedure auditing. PURPOSE: This intervention was designed to reduce the incidence of hypothermia in ICU patients undergoing robotic-assisted mitral valve surgery upon ICU admission from 60% to 36% and the one-hour hypothermia rate from 43.3% to 26%. RESOLUTIONS: We implemented several measures including increasing the room temperature, pre-heating the ICU bed, achieving team consensus regarding prolonging the rewarming time after cardiopulmonary bypass, establishing a blanket warming area for postoperative patient use, and holding in-service training to enhance the awareness of the nurses were implemented. RESULTS: The incidence of hypothermia in ICU patients receiving robotic-assisted mitral valve surgery upon ICU admission decreased from 60% to 19.4%, while the one-hour hypothermia rate decreased from 43.3% to 19.4%. CONCLUSIONS: Using systemic interprofessional collaboration, combined thermal care can be achieved to significantly reduce the incidence of postoperative hypothermia in patients undergoing robotic-assisted mitral valve surgeries resulting in higher patient care quality and shorter ICU stays. We recommend applying this combined method to improve the quality of perioperative care for long-duration and major surgical procedures that involve large postoperative wounds and for patients who may require wider exposure during their operation.

Rewarming Young Children After Drowning-Associated Hypothermia and Out-of-Hospital Cardiac Arrest: Analysis Using the CAse REport Guideline.

OBJECTIVES: Extracorporeal membrane oxygenation (ECMO) is recommended in adults with drowning-associated hypothermia and out-of-hospital cardiac arrest (OHCA). Our experience of managing a drowned 2-year-old girl with hypothermia (23°C) and cardiac arrest (58 min) prompted this summary using the CAse REport (CARE) guideline to address the question of optimal rewarming procedure in such patients. DESIGN/PATIENTS: Following the CARE guideline, we identified 24 reports in the "PubMed database" describing children less than or equal to 6 years old with a temperature less than or equal to 28°C who had been rewarmed using conventional intensive care ± ECMO. Adding our patient, we were able to analyze a total of 57 cases. MAIN RESULTS: The two groups (ECMO vs non-ECMO) differed with respect to submersion time, pH and potassium but not age, temperature or duration of cardiac arrest. However, 44 of 44 in the ECMO group were pulseless on arrival versus eight of 13 in the non-ECMO group. Regarding survival, 12 of 13 children (92%) undergoing conventional rewarming survived compared with 18 of 44 children (41%) undergoing ECMO. Among survivors, 11 of 12 children (91%) in the conventional group and 14 of 18 (77%) in the ECMO group had favorable outcome. We failed to identify any correlation between "rewarming rate" and "outcome." CONCLUSIONS: In this summary analysis, we conclude that conventional therapy should be initiated for drowned children with OHCA. However, if this therapy does not result in return of spontaneous circulation, a discussion of withdrawal of intensive care might be prudent when core temperature has reached 34°C. We suggest further work is needed using an international registry.

Analysis of rebound intracranial pressure occurring during rewarming after therapeutic hypothermia in traumatic brain injury patients.

OBJECTIVE: To investigate the risk factors associated with rebound intracranial pressure (ICP), a phenomenon that occurs when brain swelling reprogresses rapidly during rewarming in patients who have undergone therapeutic hypothermia for traumatic brain injury (TBI). METHODS: This study analyzed 42 patients who underwent therapeutic hypothermia among 172 patients with severe TBI admitted to a single regional trauma center between January 2017 and December 2020. Forty-two patients were classified into 34.5 °C (mild) and 33 °C (moderate) hypothermia groups according to the therapeutic hypothermia protocol for TBI. Rewarming was initiated post-hypothermia, wherein ICP was maintained at ≤ 20 mmHg and cerebral perfusion pressure was maintained at ≥ 50 mmHg for ≥ 24 h. In the rewarming protocol, the target core temperature was increased to 36.5 °C at 0.1 °C/h. RESULTS: Of the 42 patients who underwent therapeutic hypothermia, 27 did not survive: 9 in the mild and 18 in the moderate hypothermia groups. The moderate hypothermia group had a significantly higher mortality rate than the mild hypothermia group (p = 0.013). Rebound ICP occurred in 9 of 25 patients: 2 in the mild and 7 in the moderate hypothermia groups. In the risk factor analysis of rebound ICP, only the degree of hypothermia was statistically significant, and rebound ICP was observed more frequently in the moderate than in the mild hypothermia group (p = 0.025). CONCLUSIONS: In patients who underwent rewarming after therapeutic hypothermia, rebound ICP presented a higher risk at 33 °C than at 34.5 °C. Therefore, more careful rewarming is needed in patients receiving therapeutic hypothermia at 33 °C.

Extracorporeal Rewarming Is Associated With Increased Survival Rate in Severely Hypothermic Patients With Preserved Spontaneous Circulation.

Treatment recommendations for rewarming patients in severe accidental hypothermia with preserved spontaneous circulation have a weak evidence due to the absence of randomized clinical trials. We aimed to compare the outcomes of extracorporeal versus less-invasive rewarming of severely hypothermic patients with preserved spontaneous circulation. We conducted a multicenter retrospective study. The patient population was compiled based on data from the HELP Registry, the International Hypothermia Registry, and a literature review. Adult patients with a core temperature <28°C and preserved spontaneous circulation were included. Patients who underwent extracorporeal rewarming were compared with patients rewarmed with less-invasive methods, using a matched-pair analysis. The study population consisted of 50 patients rewarmed extracorporeally and 85 patients rewarmed with other, less-invasive methods. Variables significantly associated with survival included: lower age; outdoor cooling circumstances; higher blood pressure; higher PaCO 2 ; higher BE; higher HCO 3 ; and the absence of comorbidities. The survival rate was higher in patients rewarmed extracorporeally ( p = 0.049). The relative risk of death was twice as high in patients rewarmed less invasively. Based on our data, we conclude that patients in severe accidental hypothermia with circulatory instability can benefit from extracorporeal rewarming without an increased risk of complications.

Temperature Control After Cardiac Arrest: A Narrative Review.

Cardiac arrest (CA) is a critical public health issue affecting more than half a million Americans annually. The main determinant of outcome post-CA is hypoxic-ischemic brain injury (HIBI), and temperature control is currently the only evidence-based, guideline-recommended intervention targeting secondary brain injury. Temperature control is a key component of a post-CA care bundle; however, conflicting evidence challenges its wide implementation across the vastly heterogeneous population of CA survivors. Here, we critically appraise the available literature on temperature control in HIBI, detail how the evidence has been integrated into clinical practice, and highlight the complications associated with its use and the timing of neuroprognostication after CA. Future clinical trials evaluating different temperature targets, rates of rewarming, duration of cooling, and identifying which patient phenotype benefits from different temperature control methods are needed to address these prevailing knowledge gaps.

The effect of rewarming on hemodynamic parameters and arterial blood gases of patients after open-heart surgery: A randomized controlled trial.

INTRODUCTION: Hypothermia after open-heart surgery can have potential side effects for patients. AIM: This study aimed to examine the effects of rewarming on patients' hemodynamic and arterial blood gases parameters after open-heart surgery. METHODS: This randomized controlled trial was performed in 2019 on 80 patients undergoing open-heart surgery at Tehran Heart Center, Iran. The subjects were consecutively recruited and randomly assigned to an intervention group (n=40) and a control group (n=40). After the surgery, the intervention group was warmed with an electric warming mattress while the control group warmed using a simple hospital blanket. The hemodynamic parameters of the two groups were measured 6 times and arterial blood gas was measured 3 times. Data were analyzed by independent samples t and Chi-squared tests, and repeated measures analysis. RESULTS: Before the intervention, the two groups did not significantly differ in terms of hemodynamic and blood gas parameters. However, the two groups were significantly different in the mean heart rate, systolic blood pressure, diastolic blood pressure, mean arterial blood pressure, temperature, right and left lung drainage in the first half-hour, and the first to fourth hours after the intervention (p < 0.05). Furthermore, there was a significant difference between the mean arterial oxygen pressure of the two groups during and after rewarming (P <0.05). CONCLUSION: Rewarming of patients after open-heart surgery can significantly affect hemodynamic and arterial blood gas parameters. Therefore, rewarming methods can be used safely to improve the patients' hemodynamic parameters after open-heart surgery.

Reduction of amputations of frostbitten limbs by treatment using microwave rewarming.

Drug treatment of limb frostbite injuries is complicated due to the poor delivery of medications to affected tissues. External rewarming of the frostbitten area is risky and does not always result in positive outcomes because the dilatation of superficial vessels with constricted deep vessels can lead to irreversible damage, necrosis, and amputation. One of the techniques to restore perfusion of deep vessels in an affected extremity is rewarming with low-power microwave radiation in a specially designed metal chamber. Below are findings following treatment of 14 volunteers with this technique in 2 Tomsk hospitals during winters of 2018-2021. It is demonstrated that timely, i.e. in the early reactive period, application of microwave radiation and appropriate supportive drug treatment results in positive amputation-free outcomes. The key requirement is prompt thermal insulation of the trauma and no prior exposure to external heat sources.

Prolonged Controlled Oxygenated Rewarming Improves Immediate Tubular Function and Energetic Recovery of Porcine Kidneys During Normothermic Machine Perfusion.

BACKGROUND: Normothermic machine perfusion (NMP) is typically performed after a period of hypothermic preservation, which exposes the kidney to an abrupt increase in temperature and intravascular pressure. The resultant rewarming injury could be alleviated by gradual rewarming using controlled oxygenated rewarming (COR). This study aimed to establish which rewarming rate during COR results in the best protective effect on renal rewarming injury during subsequent NMP. METHODS: Twenty-eight viable porcine kidneys (n = 7/group) were obtained from a slaughterhouse. After these kidneys had sustained 30 min of warm ischemia and 24 h of oxygenated HMP, they were either rewarmed abruptly from 4-8 °C to 37 °C by directly initiating NMP or gradually throughout 30, 60, or 120 min of COR (rate of increase in kidney temperature of 4.46%/min, 2.20%/min, or 1.10%/min) before NMP. RESULTS: Kidneys that were rewarmed during the course of 120 min (COR-120) had significantly lower fractional excretion of sodium and glucose at the start of NMP compared with rewarming durations of 30 min (COR-30) and 60 min (COR-60). Although COR-120 kidneys showed superior immediate tubular function at the start of normothermic perfusion, this difference disappeared during NMP. Furthermore, energetic recovery was significantly improved in COR-30 and COR-120 kidneys compared with abruptly rewarmed and COR-60 kidneys. CONCLUSIONS: This study suggests that a rewarming rate of 1.10%/min during COR-120 could result in superior immediate tubular function and energetic recovery during NMP. Therefore, it may provide the best protective effect against rewarming injury.

Water Rewarming After Seawater Hypothermia Mitigates IL-1ß in Both Intestinal Tissue and Blood.

In this study, the rat models of severe hypothermia induced by seawater immersion were established in artificial seawater immersion at 15°C for 5 hours. With the rewarming measurement of 37°C water bath, the rewarming effects were evaluated by monitoring basic vital signs and dynamically detecting intestinal inflammation cytokines. Fifty Sprague-Dawley rats were randomly divided into five groups including the control group (group C), hypothermia group (group H), 2-hour rewarming group (group R2), 6-hour rewarming group (group R6), and 12-hour rewarming group (group R12), with 10 in each group. The basic vital signs of rats (i.e., core temperature, respiration, heart rate, and muscle tremor) were constantly recorded. The inflammatory factors were detected in the intestinal tissue via a protein chip GSR-CAA-67 of Innopsys, and the verification by reverse transcription-quantitative polymerase chain reaction. The levels of cytokines (interleukin IL-1ß, IL-6, and IL-10) were detected from blood samples collected at the end of the observation period via enzyme-linked immunosorbent assay. The expression landscape of IL-1ß in the intestinal tissue was validated by immunohistochemistry. Five hours of immersion in artificial seawater at 15°C successfully induced severe hypothermia of rats. After 2 hours of constant water bath rewarming at 37°C, the basic vital signs recovered to the normal level and maintained stably as well as the acute inflammatory reaction alleviated effectively, which indicated that 37°C of water immersion rewarming had the potential to be a suitable method for early treatment of water immersion hypothermia. After the process of hypothermia, several inflammatory cytokines of rats in rewarming groups changed distinctly with IL-1ß, showing the most significant variations compared with group C, which confirmed IL-1ß as a potential monitoring biomarker referring to the therapeutic effect of rewarming for severe hypothermia caused by seawater immersion.

Extracorporeal membrane oxygenation versus conventional rewarming for severe hypothermia in an urban emergency department.

BACKGROUND: Severe hypothermia (core body temperature < 28°C) is life-threatening and predisposes to cardiac arrest. The comparative effectiveness of different active internal rewarming methods in an urban U.S. population is unknown. We aim to compare outcomes between hypothermic emergency department (ED) patients rewarmed conventionally using an intravascular rewarming catheter or warm fluid lavage versus those rewarmed using extracorporeal membrane oxygenation (ECMO). METHODS: We performed a retrospective cohort analysis of adults with severe hypothermia due to outdoor exposure presenting to an urban ED in Minnesota, 2007-2021. The primary outcome was hospital survival. We also calculated the rewarming rate in the 4 h after ED arrival and compared these data between patients rewarmed with ECMO (the extracorporeal rewarming group) versus without ECMO (the conventional rewarming group). We repeated these analyses in the subgroup of patients with cardiac arrest. RESULTS: We analyzed 44 hypothermic ED patients: 25 patients in the extracorporeal rewarming group (median temperature 24.1°C, 84% with cardiac arrest) and 19 patients in the conventional rewarming group (median temperature 26.3°C, 37% with cardiac arrest; 89% received an intravascular rewarming catheter). The median rewarming rate was greater in the extracorporeal versus conventional group (2.3°C/h vs. 1.5°C/h, absolute difference 0.8°C/h, 95% confidence interval [CI] 0.3-1.2°C/h) yet hospital survival was similar (68% vs. 74%). Among patients with cardiac arrest, hospital survival was greater in the extracorporeal versus conventional group (71% vs. 29%, absolute difference 42%, 95% CI 4%-82%). CONCLUSIONS: Among ED patients with severe hypothermia and cardiac arrest, survival was significantly higher with ECMO versus conventional rewarming. Among all hypothermic patients, ECMO use was associated with faster rewarming than conventional methods.

Successful Nonextracorporeal Life Support Resuscitation and Rewarming of a Patient with Hypothermia in Cardiac Arrest.

We report full recovery of a patient with hypothermia in cardiac arrest following continuous and prolonged cardiopulmonary resuscitation (CPR) and conventional, nonextracorporeal life support (non-ECLS) methods. A 57-y-old man presented with unwitnessed cardiac arrest and a core temperature of 23°C (73°F). The presenting cardiac rhythm was ventricular fibrillation. The team administered epinephrine and performed defibrillation and CPR. Because ECLS was unavailable at the facility, the medical team externally and internally rewarmed the patient using heated blankets, forced warmed air, thoracic lavage, and warmed IV fluids. The patient achieved return of spontaneous circulation after 4 h 56 min of continuous CPR and rewarming. The medical team admitted the patient to the intensive care unit. He achieved full neurologic recovery the following day. When ECLS is not available and transfer is not appropriate because of patient instability or hospital location, conventional rewarming methods and continuous, prolonged CPR can lead to successful outcomes in patients with hypothermia in cardiac arrest. This case demonstrates that CPR in patients with hypothermia-associated cardiac arrest can lead to full recovery.

Frostbite of The Extremities - Recognition, Evaluation and Treatment.

OBJECTIVES: Frostbite refers to the freezing of body tissue which is caused by prolonged exposure to cold temperatures and results in tissue destruction. Tissue damage is due to both immediate cold-induced cell death and the more gradual development of localized inflammatory processes and tissue ischemia. A detailed treatment plan based on the current UpToDate literature is needed to decrease morbidity and mortality rates. METHODS: The United States National Library of Medicine (PubMed/Medline), EMBASE, Web of Science, and the Cochrane Database of Systematic Reviews were systematically searched to identify publications relevant to this review. CONCLUSION: In this review, we present the current knowledge on the diagnosis and treatment of frostbite injuries. We then provide an extended and detailed treatment plan, from first aid in the field to treatment of short and long-term complications .

Pediatric Environmental Cold Injuries.

Cold weather injuries are relevant concerns for children during winter sports and outdoor activities. To mitigate the risk of cold injury in this high-risk population, providers can educate parents on proper outdoor attire as well as the added risks of wind and water exposure. There are 2 types of environmental cold injuries: freezing injuries and nonfreezing injuries. Frostbite is a freezing injury from direct contact with cold air or surfaces. The extent of injury depends on the depth to which the freezing extends. Treatment involves rewarming the frozen tissue with warm water baths and considering analgesia. Hypothermia is a nonfreezing cold injury, and it can occur even when ambient temperatures are above freezing. When there is a decrease in the body's core temperature, hypothermia progresses from mild to severe symptoms. Treatment of hypothermia is threefold but is also dependent on the core body temperature, as colder core temperatures will require more aggressive warming techniques. Hypothermia treatment involves passive protection from further heat loss (ie, removing wet clothing), which helps the body to warm itself. Treatment also involves active external rewarming wherein a heat source, such as a heated blanket, is used to increase body temperature. Active internal rewarming is the delivery of heat inside the patient's body, such as warmed intravenous fluids.

Accidental hypothermia: direct evidence for consciousness as a marker of cardiac arrest risk in the acute assessment of cold patients.

BACKGROUND: Rapid stratification of the risk of cardiac arrest is essential in the assessment of patients with isolated accidental hypothermia. Traditional methods based on measurement of core temperature are unreliable in the field. Behavioural observations have been used as predictors of core temperature and thus indirect predictors of cardiac arrest. This study aims to quantify the direct relationship between observed conscious level and cardiac arrest. METHODS: Retrospective case report analysis identified 114 cases of isolated accidental hypothermia meeting inclusion criteria. Level of consciousness in the acute assessment and management phase was classified using the AVPU system with an additional category of "Alert with confusion"; statistical analysis then related level of consciousness to incidence of cardiac arrest. RESULTS: All patients who subsequently suffered cardiac arrest showed some impairment of consciousness (p < < .0001), and the risk of arrest increased directly with the level of impairment; none of the 33 fully alert patients arrested. In the lowest impairment category, Alert confused, a quarter of the 12 patients went on to arrest, while in the highest Unresponsive category, two thirds of the 43 patients arrested. Where core temperature was available (62 cases), prediction of arrest by consciousness level was at least as good as prediction from core temperature. CONCLUSIONS: This study provides retrospective analytical evidence that consciousness level is a valid predictor of cardiac arrest risk in isolated accidental hypothermia; the importance of including confusion as a criterion is a new finding. This study suggests the use of consciousness alone may be at least as good as core temperature in cardiac arrest risk prediction. These results are likely to be of particular relevance to the management of accidental hypothermia in the pre-hospital and mass casualty environment, allowing for rapid and accurate triage of hypothermic patients.

Successful recovery of severe hypothermia with minimally invasive central catheter.

BACKGROUND: Severe hypothermia can result in malignant arrhythmias or cardiac arrest and require invasive central rewarming modalities due to a core body temperature < 28 °C. Difficult rescue missions can make continuous CPR challenging, but the decrease in oxygen consumption at these low temperatures allows for successful recovery despite the delay. Although other active warming techniques, such as peritoneal lavage, intravascular warming catheter, and renal replacement therapy can be beneficial, the consensus statements recommend extracorporeal life support as the preferred rewarming method. CASE PRESENTATION: A 42-year-old female was found in a pond after presumed exposure for 30-40 min with an outside temperature of 17 °F (-8 °C) and was found to be in ventricular fibrillation. ACLS protocol was then initiated. At the hospital, she was intubated and sedated with continuous CPR during multimodal rewarming, including active internal via the ZOLL Icy catheter. One hour after rewarming, with core temperature above 29 °C, she was defibrillated and achieved ROSC. As she continued to warm, she made purposeful movement and was warmed and maintained at euthermia. She was initiated on antibiotics due to aspiration concerns and titrated off vasopressors with extubation on day 2 of hospitalization. She had mild complaints of extremity numbness and chest pain from compressions prior to discharge on hospitalization day 4. CONCLUSIONS: This case has a successful resuscitation of severe hypothermia associated with cardiac arrest. The patient was warmed at greater than 4 °C/h with a less invasive, quicker and potentially more available approach to warming. With equipment improvements, the ability to provide prolonged CPR while rewarming may suggest that transferring to an extracorporeal life support center is not necessary.

Noninvasive Versus Invasive Brain Temperature Measurement During Targeted Temperature Management: A Preclinical Study in a Swine Cardiac Arrest Model.

We aimed to evaluate correlation and agreement between noninvasive brain temperature (TBN) and invasive brain temperature (TBI) measurement during targeted temperature management (TTM) in a swine cardiac arrest model. Defibrillation attempts were provided after 5 minutes of ventricular fibrillation and 12 minutes of cardiopulmonary resuscitation in five pigs. After return of spontaneous circulation, TTM was provided with induction and maintenance phases with a target temperature of 33°C for 6 hours and a rewarming phase with a rewarming rate of 1°C/h for 4 hours. TBN and TBI were measured using a double sensor method and an intracranial catheter, respectively. Pulmonary artery temperature (TP), esophageal temperature (TE), and rectal temperature (TR) were measured. Primary outcomes were correlation and agreement between TBN and TBI and secondary outcomes were correlation and agreement among TBN and other temperatures. The Pearson correlation coefficient (PCC) between TBN and TBI was 0.95 (p < 0.001) during the whole TTM phases. PCCs between TBN and TBI during the induction, maintenance, and rewarming phases were 0.91 (p < 0.001), 0.88 (p < 0.001), and 0.94 (p < 0.001) and 95% limits of agreement (LoAs) between TBN and TBI were (-0.27°C to 0.78°C), (-0.18°C to 0.54°C), and (-0.93°C to 0.88°C), respectively. Correlation between TBN and TBI during the maintenance phase was higher than correlation between TBN and TE (PCC = 0.74, p < 0.001) or TP (PCC = 0.81, p < 0.001). The 95% LoAs were narrowest between TBN and TP in the induction phase (-0.58 to 0.11), between TBN and TBI in the maintenance phase (-0.54 to 0.18), and between TBN and TR in the rewarming phase (-0.96 to 0.84). Noninvasive brain temperature showed good correlation with invasive brain temperature during TTM in a swine cardiac arrest model. Correlation was highest during the rewarming phase and lowest during the maintenance phase. Agreement between the two measurements was not clinically acceptable.