The effect of decompressive hemicraniectomy on brain temperature after severe brain injury

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 Influences Intracranial Pressure and Cerebral Perfusion Pressure After Traumatic Brain Injury: A CENTER-TBI Study

Background

After traumatic brain injury (TBI), fever is frequent. Brain temperature (BT), which is directly linked to body temperature, may influence brain physiology. Increased body and/or BT may cause secondary brain damage, with deleterious effects on intracranial pressure (ICP), cerebral perfusion pressure (CPP), and outcome.

Methods

Collaborative European NeuroTrauma Effectiveness Research in Traumatic Brain Injury (CENTER-TBI), a prospective multicenter longitudinal study on TBI in Europe and Israel, includes a high resolution cohort of patients with data sampled at a high frequency (from 100 to 500 Hz). In this study, simultaneous BT, ICP, and CPP recordings were investigated. A mixed-effects linear model was used to examine the association between different BT levels and ICP. We additionally focused on changes in ICP and CPP during the episodes of BT changes (Δ BT ≥ 0.5 °C lasting from 15 min to 3 h) up or downward. The significance of ICP and CPP variations was estimated with the paired samples Wilcoxon test (also known as Wilcoxon signed-rank test).

Results

Twenty-one patients with 2,435 h of simultaneous BT and ICP monitoring were studied. All patients reached a BT of 38 °C and experienced at least one episode of ICP above 20 mm Hg. The linear mixed-effects model revealed an association between BT above 37.5 °C and higher ICP levels that was not confirmed for lower BT. We identified 149 episodes of BT changes. During BT elevations (n = 79) ICP increased, whereas CPP was reduced; opposite ICP and CPP variations occurred during episodes of BT reduction (n = 70). All these changes were of moderate clinical relevance (increase of ICP of 4.5 and CPP decrease of 7.5 mm Hg for BT rise, and ICP reduction of 1.7 and CPP elevation of 3.7 mm Hg during BT defervescence), even if statistically significant (p < 0.0001). It has to be noted, however, that a number of therapeutic interventions against intracranial hypertension was documented during those episodes.

Conclusions

Patients after TBI usually develop BT > 38 °C soon after the injury. BT may influence brain physiology, as reflected by ICP and CPP. An association between BT exceeding 37.5 °C and a higher ICP was identified but not confirmed for lower BT ranges. The relationship between BT, ICP, and CPP become clearer during rapid temperature changes. During episodes of temperature elevation, BT seems to have a significant impact on ICP and CPP.

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.

Thermal Regulation of the Brain-An Anatomical and Physiological Review for Clinical Neuroscientists

Humans, like all mammals and birds, maintain a near constant core body temperature of 36–37.5°C over a broad range of environmental conditions and are thus referred to as endotherms. The evolution of the brain and its supporting structures in mammals and birds coincided with this development of endothermy. Despite the recognition that a more evolved and complicated brain with all of its temperature-dependent cerebral circuitry and neuronal processes would require more sophisticated thermal control mechanisms, the current understanding of brain temperature regulation remains limited. To optimize the development and maintenance of the brain in health and to accelerate its healing and restoration in illness, focused, and committed efforts are much needed to advance the fundamental understanding of brain temperature. To effectively study and examine brain temperature and its regulation, we must first understand relevant anatomical and physiological properties of thermoregulation in the head-neck regions.

Regional pressure and temperature variations across the injured human brain: comparisons between paired intraparenchymal and ventricular measurements

INTRODUCTION

Intraparenchymal, multimodality sensors are commonly used in the management of patients with severe traumatic brain injury (TBI). The 'gold standard', based on accuracy, reliability and cost for intracranial pressure (ICP) monitoring is within the cerebral ventricle (external strain gauge). There are no standards yet for intracerebral temperature monitoring and little is known of temperature differences between brain tissue and ventricle. The aim of the study therefore was to determine pressure and temperature differences at intraparenchymal and ventricular sites during five days of continuous neuromonitoring.

METHODS

Patients with severe TBI requiring emergency surgery.

INCLUSION CRITERIA

patients who required ICP monitoring were eligible for recruitment. Two intracerebral probe types were used: a) intraventricular, dual parameter sensor (measuring pressure, temperature) with inbuilt catheter for CSF drainage: b) multiparameter intraparenchymal sensor measuring pressure, temperature and oxygen partial pressure. All sensors were inserted during surgery and under aseptic conditions.

RESULTS

Seventeen patients, 12 undergoing neurosurgery (decompressive craniectomy n = 8, craniotomy n = 4) aged 21-78 years were studied. Agreement of measures for 9540 brain tissue-ventricular temperature 'pairs' and 10,291 brain tissue-ventricular pressure 'pairs' were determined using mixed model to compare mean temperature and pressure for longitudinal data. There was no significant overall difference for mean temperature (p = 0.92) or mean pressure readings (p = 0.379) between tissue and ventricular sites. With 95.8 % of paired temperature readings within 2SD (-0.4 to 0.4 °C) differences in temperature between brain tissue and ventricle were clinically insignificant. For pressure, 93.5 % of readings pairs fell within the 2SD range (-9.4756 to 7.8112 mmHg). However, for individual patients, agreement for mean tissue-ventricular pressure differences was poor on occasions.

CONCLUSIONS

There is good overall agreement between paired temperature measurements obtained from deep white matter and brain ventricle in patients with and without early neurosurgery. For paired ICP measurements, 93.5 % of readings were within 2SD of mean difference. Whilst the majority of paired readings were comparable (within 10 mmHg) clinically relevant tissue-ventricular dissociations were noted. Further work is required to unravel the events responsible for short intervals of pressure dissociation before tissue pressure readings can be definitively accepted as a reliable surrogate for ventricular pressure.

Brain temperature and its fundamental properties: a review for clinical neuroscientists

Brain temperature, as an independent therapeutic target variable, has received increasingly intense clinical attention. To date, brain hypothermia represents the most potent neuroprotectant in laboratory studies. Although the impact of brain temperature is prevalent in a number of common human diseases including: head trauma, stroke, multiple sclerosis, epilepsy, mood disorders, headaches, and neurodegenerative disorders, it is evident and well recognized that the therapeutic application of induced hypothermia is limited to a few highly selected clinical conditions such as cardiac arrest and hypoxic ischemic neonatal encephalopathy. Efforts to understand the fundamental aspects of brain temperature regulation are therefore critical for the development of safe, effective, and pragmatic clinical treatments for patients with brain injuries. Although centrally-mediated mechanisms to maintain a stable body temperature are relatively well established, very little is clinically known about brain temperature's spatial and temporal distribution, its physiological and pathological fluctuations, and the mechanism underlying brain thermal homeostasis. The human brain, a metabolically "expensive" organ with intense heat production, is sensitive to fluctuations in temperature with regards to its functional activity and energy efficiency. In this review, we discuss several critical aspects concerning the fundamental properties of brain temperature from a clinical perspective.