Report of a consensus meeting on human brain temperature after severe traumatic brain injury: its measurement and management during pyrexia

Difference between brain temperature and core temperature in severe traumatic brain injury: a systematic review

INTRODUCTION

Intensive care management for traumatic brain injury (TBI) patients aims to prevent secondary cerebral damage. Targeted temperature management is one option to prevent cerebral damage, as hypothermia may have protective effects. By conducting a systematic literature review we evaluated: 1) the presence of a temperature difference (gradient) between brain temperature (Tb) and core temperature (Tc) in TBI patients; and 2) clinical factors associated with reported differences.

EVIDENCE ACQUISITION

The PubMed database was systematically searched using Mesh terms and key words, and Web of Sciences was assessed for additional article citations. We included studies that continuously and simultaneously measured Tb and Tc in severe TBI patients. The National Institutes of Health (NIH) quality assessment tool for observational cohort and cross-sectional studies was modified to fit the purpose of our study. Statistical data were extracted for further meta-analyses.

EVIDENCE SYNTHESIS

We included 16 studies, with a total of 480 patients. Clinical heterogeneity consisted of Tb/Tc measurement site, measurement device, physiological changes, local protocols, and medical or surgical interventions. The studies have a high statistical heterogeneity (I2). The pooled mean temperature gradient between Tb and Tc was +0.14 °C (95% confidence interval: 0.03 to 0.24) and ranged from -1.29 to +1.1 °C. Patients who underwent a decompressive (hemi)craniectomy showed lower Tb values compared to Tc found in three studies.

CONCLUSIONS

Studies on Tb and Tc are heterogeneous and show that, on average, Tb and Tc are not clinically significant different in TBI patients (<0.2 °C). Interpretations and interventions of the brain and central temperatures will benefit from standardization of temperature measurements.

Brain temperature regulation in poor-grade subarachnoid hemorrhage patients - A multimodal neuromonitoring study

Elevated body temperature (T_core) is associated with poor outcome after subarachnoid hemorrhage (SAH). Brain temperature (T_brain) is usually higher than T_core. However, the implication of this difference (T_delta) remains unclear. We aimed to study factors associated with higher T_delta and its association with outcome. We included 46 SAH patients undergoing multimodal neuromonitoring, for a total of 7879 h of averaged data of T_core, T_brain, cerebral blood flow, cerebral perfusion pressure, intracranial pressure and cerebral metabolism (CMD). Three-months good functional outcome was defined as modified Rankin Scale ≤2. T_brain was tightly correlated with T_core (r = 0.948, p < 0.01), and was higher in 73.7% of neuromonitoring time (T_delta +0.18°C, IQR -0.01 - 0.37°C). A higher T_delta was associated with better metabolic state, indicated by lower CMD-glutamate (p = 0.003) and CMD-lactate (p < 0.001), and lower risk of mitochondrial dysfunction (MD) (OR = 0.2, p < 0.001). During MD, T_delta was significantly lower (0°C, IQR -0.2 - 0.1; p < 0.001). A higher T_delta was associated with improved outcome (OR = 7.7, p = 0.002). Our study suggests that T_brain is associated with brain metabolic activity and exceeds T_core when mitochondrial function is preserved. Further studies are needed to understand how T_delta may serve as a surrogate marker for brain function and predict clinical course and outcome after SAH.

Effects of Brain Temperature on the Outcome of Patients with Traumatic Brain Injury: A Prospective Observational Study

A prospective observational study collected temperature data from 51 patients in 11 neurosurgical centers and follow-up outcome information at 6 months in 49 patients. Brain temperature (T_br) was measured directly by an intraventricular temperature sensor. Axillary temperature (T_ax) and rectal temperature (T_re) were measured by electric thermometers. T_br was 0.4 to 1.5°C higher than body temperature. T_re correlated well with the T_br (coefficient: 0.7378; p < 0.05). Among all patients, Glasgow Coma Scale (GCS) scores on admission were significantly lower in the patients with post-operatively extreme peak temperature (T_peak, < 37°C or >39°C in first 24 h) and major temperature variation (T_vari > 1°C in first 12 h; p < 0.05, p < 0.01, respectively). Among the patients with no temperature intervention, the extreme T_peak group showed a lower Glasgow Outcome Scale-Extended (GOS-E) score at 6 months (p < 0.05) with lower GCS scores on admission (p < 0.01), compared with the moderate T_peak group. Remarkably, the major T_vari group showed significantly lower GOS-E scores (p < 0.05) with the same GCS scores as the minor T_vari group. Thus, T_re is the better candidate to estimate T_br. Spontaneously extreme T_peak in TBI represents both more serious injury on admission and worse prognosis, and T_vari might be used as a novel prognostic parameter in TBI. Brain temperature is therefore one of the critical indicators evaluating injury severity, prognostication, and monitoring in the management of TBI. This prospective observational study has been registered in ClinicalTrials.gov ( https://clinicaltrials.gov ), and the registration number is NCT03068143.

Body Temperature after EMS Transport: Association with Traumatic Brain Injury Outcomes

INTRODUCTION

Low body temperatures following prehospital transport are associated with poor outcomes in patients with traumatic brain injury (TBI). However, a minimal amount is known about potential associations across a range of temperatures obtained immediately after prehospital transport. Furthermore, a minimal amount is known about the influence of body temperature on non-mortality outcomes. The purpose of this study was to assess the correlation between temperatures obtained immediately following prehospital transport and TBI outcomes across the entire range of temperatures.

METHODS

This retrospective observational study included all moderate/severe TBI cases (CDC Barell Matrix Type 1) in the pre-implementation cohort of the Excellence in Prehospital Injury Care (EPIC) TBI Study (NIH/NINDS: 1R01NS071049). Cases were compared across four cohorts of initial trauma center temperature (ITCT): <35.0°C [Very Low Temperature (VLT)]; 35.0-35.9°C [Low Temperature (LT)]; 36.0-37.9°C [Normal Temperature (NT)]; and ≥38.0°C [Elevated Temperature (ET)]. Multivariable analysis was performed adjusting for injury severity score, age, sex, race, ethnicity, blunt/penetrating trauma, and payment source. Adjusted odds ratios (aORs) with 95% confidence intervals (CI) for mortality were calculated. To evaluate non-mortality outcomes, deaths were excluded and the adjusted median increase in hospital length of stay (LOS), ICU LOS and total hospital charges were calculated for each ITCT group and compared to the NT group.

RESULTS

22,925 cases were identified and cases with interfacility transfer (7361, 32%), no EMS transport (1213, 5%), missing ITCT (2083, 9%), or missing demographic data (391, 2%) were excluded. Within this study cohort the aORs for death (compared to the NT group) were 2.41 (CI: 1.83-3.17) for VLT, 1.62 (CI: 1.37-1.93) for LT, and 1.86 (CI: 1.52-3.00) for ET. Similarly, trauma center (TC) LOS, ICU LOS, and total TC charges increased in all temperature groups when compared to NT.

CONCLUSION

In this large, statewide study of major TBI, both ETs and LTs immediately following prehospital transport were independently associated with higher mortality and with increased TC LOS, ICU LOS, and total TC charges. Further study is needed to identify the causes of abnormal body temperature during the prehospital interval and if in-field measures to prevent temperature variations might improve outcomes.

A Systematic Review of the Effects of Body Temperature on Outcome After Adult Traumatic Brain Injury

OBJECTIVE

This systematic review describes effects of body temperature alterations defined as fever, controlled normothermia, and spontaneous or induced hypothermia on outcome after traumatic brain injury (TBI) in adults.

DATA SOURCES

A search was conducted using PubMed, Cochrane Library database, Cumulative Index to Nursing and Allied Health Literature, EMBASE, and ISI Web of Science in July 2013 with no back date restriction except for induced hypothermia (2009).

STUDY SELECTION

Of 1366 titles identified, 712 were reviewed. Sixteen articles met inclusion criteria: randomized controlled trials in hypothermia since 2009 (last Cochrane review) or cohort studies of temperature in TBI, measure core and/or brain temperature, neurologic outcome reporting, primarily adult patients, and English language publications. Exclusion criteria were as follows: most patients with non-TBI diagnosis, primarily pediatric patients, case reports, or laboratory/animal studies.

DATA SYNTHESIS

Most studies found that fever avoidance resulted in positive outcomes including decreased length of stay in the intensive care unit; mortality; and incidence of hypertension, elevated intracranial pressure, and tachycardia. Hypothermia on admission correlated with poor outcomes. Controlled normothermia improved surrogate outcomes. Prophylactic induced hypothermia is not supported by the available evidence from randomized controlled trial.

CONCLUSION

Setting a goal of normothermia, avoiding fever, and aggressively treating fever may be most important after TBI. Further research is needed to characterize the magnitude and duration of temperature alteration after TBI, determine if temperature alteration influences or predicts neurologic outcome, determine if rate of temperature change influences or predicts neurologic outcome, and compare controlled normothermia versus standard practice or hypothermia.

New multimodal data obtained in-vivo from a single ultra-miniature transducer

Recent advances in multimodal sensing technology and sensor miniaturization technologies are paving the way for a new era in physiological measurement. Traditional approaches have integrated several transducers on a single silicon chip or packaged several sensing elements within a biocompatible catheter. Thermal and electrical cross-talk between sensors, time-lag between parallel measurements, lower yields associated with the increased complexity, and restrictions on the minimum size are challenges presented by these approaches. We present an alternative method which enables simultaneous measurement of temperature, pressure and heart rate to be obtained from a single ultra-miniature solid-state transducer. For the first time multimodal data were obtained from the sensor located within the abdominal aortas of five rats. The catheter-tip sensor interfaces with a fully implanted and inductively powered telemetry device capable of operating for the lifetime of the animal. Results of this study demonstrate good agreement between the core-temperature measurement from the catheter-tip sensor and the reference sensor with mean difference between the two sensors of 0.03 °C ± 0.02 °C (n = 5, 7 days). Real-time data obtained in the undisturbed rat, revealed fluctuations associated with the rest-activity cycle, in temperature, mean arterial pressure and heart rate. The stress response was shown to elicit an elevation in the core temperature of 1.5 °C. This was heralded by an elevation in mean arterial pressure of 35 mmHg and heart rate of 160 bpm. Obtaining multiple parameters from a single transducer goes a considerable way towards overcoming challenges of the prior art.

'Cool and quiet' therapy for malignant hyperthermia following severe traumatic brain injury: A preliminary clinical approach

Malignant hyperthermia increases mortality and disability in patients with brain trauma. A clinical treatment for malignant hyperthermia following severe traumatic brain injury, termed ‘cool and quiet’ therapy by the authors of the current study, was investigated. Between June 2003 and June 2013, 110 consecutive patients with malignant hyperthermia following severe traumatic brain injury were treated using mild hypothermia (35–36°C) associated with small doses of sedative and muscle relaxant. Physiological parameters and intracranial pressure were monitored, and the patients slowly rewarmed following the maintenance of mild hypothermia for 3–12 days. Consecutive patients who had undergone normothermia therapy were retrospectively analyzed as the control. In the mild hypothermia group, the recovery rate was 54.5%, the mortality rate was 22.7%, and the severe and mild disability rates were 11.8 and 10.9%, respectively. The mortality rate of the patients, particularly that of patients with a Glasgow Coma Scale (GCS) score of between 3 and 5 differed significantly between the hypothermia group and the normothermia group (P<0.05). The mortality of patients with a GCS score of between 6 and 8 was not significantly different between the two groups (P> 0.05). The therapy using mild hypothermia with a combination of sedative and muscle relaxant was beneficial in decreasing the mortality of patients with malignant hyperthermia following severe traumatic brain injury, particularly in patients with a GCS score within the range 3–5 on admission. The therapy was found to be safe, effective and convenient. However, rigorous clinical trials are required to provide evidence of the effectiveness of ‘cool and quiet’ therapy for hyperthermia.

Brain Injury as a Risk Factor for Fever Upon Admission to the Intensive Care Unit and Association With In-Hospital Case Fatality

Purpose:

To test the hypothesis that fever was more frequent in critically ill patients with brain injury when compared to nonneurological patients and to study its effect on in-hospital case fatality.

Methods:

Retrospective matched cohort study utilizing a single-center prospectively compiled registry. Critically ill neurological patients ≥18 years and consecutively admitted to the intensive care unit (ICU) with acute ischemic stroke (AIS), intracerebral hemorrhage (ICH), and traumatic brain injury (TBI) were selected. Patients were matched by sex, age, and Acute Physiology and Chronic Health Evaluation II (APACHE-II) to a cohort of nonneurological patients. Fever was defined as any temperature ≥37.5°C within the first 24 hours upon admission to the ICU. The primary outcome measure was in-hospital case fatality.

Results:

Mean age among neurological patients was 65.6 ± 15 years, 46% were men, and median APACHE-II was 15 (interquartile range 11-20). There were 18% AIS, 27% ICH, and 6% TBI. More neurological patients experienced fever than nonneurological patients (59% vs 47%, P = .007). The mean hospital length of stay was higher for nonneurological patients (18 ± 20 vs 14 ± 15 days, P = .007), and more neurological patients were dead at hospital discharge (29% vs 20%, P < .0001). After risk factor adjustment, diagnosis (neurological vs nonneurological), and the probability of being exposed to fever (propensity score), the following variables were associated with higher in-hospital case fatality: APACHE-II, neurological diagnosis, mean arterial pressure, cardiovascular and respiratory dysfunction in ICU, and fever (odds ratio 1.9, 95% confidence interval 1.04-3.6, P = .04).

Conclusion:

These data suggest that fever is a frequent occurrence after brain injury, and that it is independently associated with in-hospital case fatality.

Relationship between temperature, hematoma growth, and functional outcome after intracerebral hemorrhage

BACKGROUND

Fever and hematoma growth are known to be independent predictors of poor outcome after intracerebral hemorrhage (ICH). We sought to assess the distribution of temperature at different stages in relation to hematoma growth and functional outcome at 90 days in a cohort of ICH patients.

METHODS

Data of patients registered in the Virtual International Stroke Trials Archive--ICH were analyzed. Temperatures at baseline, 24, 48, 72, and 168 h were assessed in relation to the hematoma growth and functional outcome at 90 days. We calculated the daily linear variation of each subject's temperature by subtracting 37 °C from the maximal daily recorded temperature (delta-temperature). We used logistic regression and mixed-effects models to identify factors associated with hematoma growth, poor outcome, and temperature elevation after ICH.

RESULTS

303 patients were included in the analysis. The average age was 66 ± 12 years, 200 (66 %) were males, median admission NIHSS was 13 [Interquartile range (IQR), 9-18), median GCS was 15 (IQR, 14-15). Hematoma growth occurred in 22 % and poor functional outcome at 90-days occurred in 41 % of the patients. Cumulative delta-temperature at 72 h was associated with hematoma growth; age, ICH score, hematoma growth, and cumulative delta-temperature at 168 h were associated with poor outcome at 90 days. Factors associated with fever in mixed-models were day after onset of ICH, hypertension, base hematoma volume, intraventricular-hemorrhage, pneumonia, and hematoma growth.

CONCLUSIONS

There is a temporal and independent association between fever and hematoma growth. Fever after ICH is associated with poor outcome at 90 days. Future research is needed to study the mechanisms of this phenomenon and if early protocols of temperature modulation would be associated with improved outcomes after ICH.

Clinical review: Brain-body temperature differences in adults with severe traumatic brain injury

Surrogate or 'proxy' measures of brain temperature are used in the routine management of patients with brain damage. The prevailing view is that the brain is 'hotter' than the body. The polarity and magnitude of temperature differences between brain and body, however, remains unclear after severe traumatic brain injury (TBI). The focus of this systematic review is on the adult patient admitted to intensive/neurocritical care with a diagnosis of severe TBI (Glasgow Coma Scale score of less than 8). The review considered studies that measured brain temperature and core body temperature. Articles published in English from the years 1980 to 2012 were searched in databases, CINAHL, PubMed, Scopus, Web of Science, Science Direct, Ovid SP, Mednar and ProQuest Dissertations & Theses Database. For the review, publications of randomised controlled trials, non-randomised controlled trials, before and after studies, cohort studies, case-control studies and descriptive studies were considered for inclusion. Of 2,391 records identified via the search strategies, 37 were retrieved for detailed examination (including two via hand searching). Fifteen were reviewed and assessed for methodological quality. Eleven studies were included in the systematic review providing 15 brain-core body temperature comparisons. The direction of mean brain-body temperature differences was positive (brain higher than body temperature) and negative (brain lower than body temperature). Hypothermia is associated with large brain-body temperature differences. Brain temperature cannot be predicted reliably from core body temperature. Concurrent monitoring of brain and body temperature is recommended in patients where risk of temperature-related neuronal damage is a cause for clinical concern and when deliberate induction of below-normal body temperature is instituted.

A systematic review of differences between brain temperature and core body temperature in adult patients with severe traumatic brain injury

BACKGROUND

Studies have shown that temperature at the extremes of the thermoregulatory physiological range, commensurate with a clinical diagnosis of hypothermia (at the lower end) and hyperthermia or fever (at the upper end) increase the risk of a poor neurological outcome and contribute to higher mortality. The tissue most at risk is nervous tissue. That said however, precise measurement of cerebral tissue temperature is seldom made during routine clinical care. More commonly, brain temperature is estimated from measurements of core body temperature. Different measurement sites are frequently used as a proxy or 'surrogate' for brain temperature. Knowing whether the assumption that brain temperature can be reliably represented by core body temperature is important because it will help healthcare professionals to deliver appropriate treatment when a rise (or fall) in brain temperature beyond the 'normal' range is suspected.

OBJECTIVES

This systematic review focused on whether brain temperature is higher, lower, or the same as core body temperature in patients with severe traumatic brain injury.

INCLUSION CRITERIA

This review considered studies that include male and female patients, aged 15 years and above, admitted to an adult Intensive Care Unit, with the diagnosis of severe traumatic brain injury, with a Glasgow Coma Scale score of less than eight, and who require brain temperature monitoring.The review considered studies that measured brain temperature and core body temperature.The agreement of core body temperature as a surrogate measure for brain temperature in adult patients with severe traumatic brain injury.The review considered any randomised controlled trials. In the absence of randomised controlled trials, other research designs such as non-randomised controlled trials, before and after studies, cohort studies, case-control studies and descriptive studies were considered for inclusion.

SEARCH STRATEGY

Utilising a three-step search strategy, articles published in English from the years 1980 to 2010 from the following databases were searched: CINAHL, PubMed, Scopus, Web of Science, Science Direct, Ovid SP, Mednar and ProQuest Dissertations & Theses Database.

METHODOLOGICAL QUALITY

Two reviewers independently reviewed studies using the appraisal tool developed by the authors, as the critical appraisal instrument provided by the Joanna Briggs Institute was not suitable for this systematic review.

DATA EXTRACTION

Data were extracted using the extraction tool developed by the authors, as the data extraction instrument provided by the Joanna Briggs Institute was not suitable for this systematic review.

DATA SYNTHESIS

A narrative summary of all findings was presented as statistical pooling was not possible.

RESULTS

Thirty-three studies were identified through the keywords search using the databases listed above. Eight studies were included in this systematic review after the assessment of methodological quality. Eleven temperature comparisons were identified in eight studies. Most comparison showed brain temperature to be higher than core body temperature. However, three studies showed core temperature being higher than brain temperature, especially when patients' brain temperature dropped below 36°C.

CONCLUSIONS

Brain temperature cannot be predicted by core body temperature. None of the core body temperature sites included in this review can be a surrogate for brain temperature. Concurrent monitoring of brain and body temperature is important in managing patients with severe traumatic brain injury.

IMPLICATIONS FOR PRACTICE

As body temperature does not accurately reflect brain temperature, brain temperature and core temperature should be monitored concurrently in patients with severe traumatic brain injury who are admitted to the Intensive Care Unit.

IMPLICATIONS FOR RESEARCH

Future studies should focus on having larger sample sizes and standardised brain and core temperature measurement sites.

Early hospital care of severe traumatic brain injury

Head injury is one of the major causes of trauma-related morbidity and mortality in all age groups in the United Kingdom, and anaesthetists encounter this problem in many areas of their work. Despite a better understanding of the pathophysiological processes following traumatic brain injury and a wealth of research, there is currently no specific treatment. Outcome remains dependant on basic clinical care: management of the patient's airway with particular attention to preventing hypoxia; avoidance of the extremes of lung ventilation; and the maintenance of adequate cerebral perfusion, in an attempt to avoid exacerbating any secondary injury. Hypertonic fluids show promise in the management of patients with raised intracranial pressure. Computed tomography scanning has had a major impact on the early identification of lesions amenable to surgery, and recent guidelines have rationalised its use in those with less severe injuries. Within critical care, the importance of controlling blood glucose is becoming clearer, along with the potential beneficial effects of hyperoxia. The major improvement in outcome reflects the use of protocols to guide resuscitation, investigation and treatment and the role of specialist neurosciences centres in caring for these patients. Finally, certain groups are now recognised as being at greater risk, in particular the elderly, anticoagulated patient.