Severe traumatic head injury in adults: which patients are at risk of early hyperthermia?

Traumatic brain injury extending to the striatum alters autonomic thermoregulation and hypothalamic monoamines in recovering rats

The brain cortex is the structure that is typically injured in traumatic brain injury (TBI) and is anatomically connected with other brain regions, including the striatum and hypothalamus, which are associated in part with motor function and the regulation of body temperature, respectively. We investigated whether a TBI extending to the striatum could affect peripheral and core temperatures as an indicator of autonomic thermoregulatory function. Moreover, it is unknown whether thermal modulation is accompanied by hypothalamic and cortical monoamine changes in rats with motor function recovery. The animals were allocated into three groups: the sham group (sham), a TBI group with a cortical contusion alone (TBI alone), and a TBI group with an injury extending to the dorsal striatum (TBI + striatal injury). Body temperature and motor deficits were evaluated for 20 days post-injury. On the 3rd and 20th days, rats were euthanized to measure the serotonin (5-HT), noradrenaline (NA), and dopamine (DA) levels using high-performance liquid chromatography (HPLC). We observed that TBI with an injury extending to the dorsal striatum increased core and peripheral temperatures. These changes were accompanied by a sustained motor deficit lasting for 14 days. Furthermore, there were notable increases in NA and 5-HT levels in the brain cortex and hypothalamus both 3 and 20 days after injury. In contrast, rats with TBI alone showed no changes in peripheral temperatures and achieved motor function recovery by the 7th day post-injury. In conclusion, our results suggest that TBI with an injury extending to the dorsal striatum elevates both core and peripheral temperatures, causing a delay in functional recovery and increasing hypothalamic monoamine levels. The aftereffects can be attributed to the injury site and changes to the autonomic thermoregulatory functions.

A risk nomogram for predicting prolonged intensive care unit stays in patients with chronic obstructive pulmonary disease

Background

Providing intensive care is increasingly expensive, and the aim of this study was to construct a risk column line graph (nomograms)for prolonged length of stay (LOS) in the intensive care unit (ICU) for patients with chronic obstructive pulmonary disease (COPD).

Methods

This study included 4,940 patients, and the data set was randomly divided into training (n = 3,458) and validation (n = 1,482) sets at a 7:3 ratio. First, least absolute shrinkage and selection operator (LASSO) regression analysis was used to optimize variable selection by running a tenfold k-cyclic coordinate descent. Second, a prediction model was constructed using multifactorial logistic regression analysis. Third, the model was validated using receiver operating characteristic (ROC) curves, Hosmer-Lemeshow tests, calibration plots, and decision-curve analysis (DCA), and was further internally validated.

Results

This study selected 11 predictors: sepsis, renal replacement therapy, cerebrovascular disease, respiratory failure, ventilator associated pneumonia, norepinephrine, bronchodilators, invasive mechanical ventilation, electrolytes disorders, Glasgow Coma Scale score and body temperature. The models constructed using these 11 predictors indicated good predictive power, with the areas under the ROC curves being 0.826 (95%CI, 0.809-0.842) and 0.827 (95%CI, 0.802-0.853) in the training and validation sets, respectively. The Hosmer-Lemeshow test indicated a strong agreement between the predicted and observed probabilities in the training (χ² = 8.21, p = 0.413) and validation (χ² = 0.64, p = 0.999) sets. In addition, decision-curve analysis suggested that the model had good clinical validity.

Conclusion

This study has constructed and validated original and dynamic nomograms for prolonged ICU stay in patients with COPD using 11 easily collected parameters. These nomograms can provide useful guidance to medical and nursing practitioners in ICUs and help reduce the disease and economic burdens on patients.

Interventions to reduce body temperature to 35 ⁰C to 37 ⁰C in adults and children with traumatic brain injury

BACKGROUND

Traumatic brain injury (TBI) is a major cause of death and disability, with an estimated 5.5 million people experiencing severe TBI worldwide every year. Observational clinical studies of people with TBI suggest an association between raised body temperature and unfavourable outcome, although this relationship is inconsistent. Additionally, preclinical models suggest that reducing temperature to 35 °C to 37.5 °C improves biochemical and histopathological outcomes compared to reducing temperature to a lower threshold of 33 °C to 35 °C. It is unknown whether reducing body temperature to 35 °C to 37.5 °C in people admitted to hospital with TBI is beneficial, has no effect, or causes harm. This is an update of a review last published in 2014.

OBJECTIVES

To assess the effects of pharmacological interventions or physical interventions given with the intention of reducing body temperature to 35 °C to 37.5 °C in adults and children admitted to hospital after TBI.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Web of Science, and PubMed on 28 November 2019. We searched clinical trials registers, grey literature and references lists of reviews, and we carried out forward citation searches of included studies.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) with participants of any age admitted to hospital following TBI. We included interventions that aimed to reduce body temperature to 35 °C to 37.5 °C: these included pharmacological interventions (such as paracetamol, or non-steroidal anti-inflammatory drugs), or physical interventions (such as surface cooling devices, bedside fans, or cooled intravenous fluids). Eligible comparators were placebo or usual care.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed studies for inclusion, extracted data, and assessed risks of bias. We assessed the certainty of the evidence with GRADE.

MAIN RESULTS

We included one RCT with 41 participants. This study recruited adult participants admitted to two intensive care units in Australia, and evaluated a pharmacological intervention. Researchers gave participants 1 g paracetamol or a placebo intravenously at four-hourly intervals for 72 hours. We could not be certain whether intravenous paracetamol influenced mortality at 28 days (risk ratio 2.86, 95% confidence interval 0.32 to 25.24). We judged the evidence for this outcome to be very low certainty, meaning we have very little confidence in this effect estimate, and the true result may be substantially different to this effect. We downgraded the certainty for imprecision (because the evidence was from a single study with very few participants), and study limitations (because we noted a high risk of selective reporting bias). This study was otherwise at low risk of bias. The included study did not report the primary outcome for this review, which was the number of people with a poor outcome at the end of follow-up (defined as death or dependency, as measured on a scale such as the Glasgow Outcome Score), or any of our secondary outcomes, which included the number of people with further intracranial haemorrhage, extracranial haemorrhage, abnormal intracranial pressure, or pneumonia or other serious infections. The only other completed trial that we found was of a physical intervention that compared advanced fever control (using a surface cooling device) versus conventional fever control in 12 participants. The trial was published as an abstract only, with insufficient details to allow inclusion, so we have added this to the 'studies awaiting classification' section, pending further information from the study authors or publication of the full study report. We identified four ongoing studies that will contribute evidence to future updates of the review if they measure relevant outcomes and, in studies with a mixed population, report data separately for participants with TBI.

AUTHORS' CONCLUSIONS

One small study contributed very low-certainty evidence for mortality to this review. The uncertainty is largely driven by limited research into reduction of body temperature to 35 °C to 37.5 °C in people with TBI. Further research that evaluates pharmacological or physical interventions, or both, may increase certainty in this field. We propose that future updates of the review, and ongoing and future research in this field, incorporate outcomes that are important to the people receiving the interventions, including side effects of any pharmacological agent (e.g. nausea or vomiting), and discomfort caused by physical therapies.

Systemic Hyperthermia in Traumatic Brain Injury-Relation to Intracranial Pressure Dynamics, Cerebral Energy Metabolism, and Clinical Outcome

BACKGROUND

Systemic hyperthermia is common after traumatic brain injury (TBI) and may induce secondary brain injury, although the pathophysiology is not fully understood. In this study, our aim was to determine the incidence and temporal course of hyperthermia after TBI and its relation to intracranial pressure dynamics, cerebral metabolism, and clinical outcomes.

MATERIALS AND METHODS

This retrospective study included 115 TBI patients. Data from systemic physiology (body temperature, blood pressure, and arterial glucose), intracranial pressure dynamics (intracranial pressure, cerebral perfusion pressure, compliance, and pressure reactivity), and cerebral microdialysis (glucose, pyruvate, lactate, glycerol, glutamate, and urea) were analyzed during the first 10 days after injury.

RESULTS

Overall, 6% of patients did not have hyperthermia (T>38°C) during the first 10 days after injury, whereas 20% had hyperthermia for >50% of the time. Hyperthermia increased from 21% (±27%) of monitoring time on day 1 to 36% (±29%) on days 6 to 10 after injury. In univariate analyses, higher body temperature was not associated with higher intracranial pressure nor lower cerebral perfusion pressure, but was associated with lower cerebral glucose concentration (P=0.001) and higher percentage of lactate-pyruvate ratio>25 (P=0.02) on days 6 to 10 after injury. Higher body temperature and lower arterial glucose concentration were associated with lower cerebral glucose in a multiple linear regression analysis (P=0.02 for both). There was no association between hyperthermia and worse clinical outcomes.

CONCLUSION

Hyperthermia was most common between days 6 and 10 following TBI, and associated with disturbances in cerebral energy metabolism but not worse clinical outcome.

Traumatic brain injury in pregnancy

Trauma is the leading cause of nonobstetric maternal mortality and affects up to 8% of all pregnancies. Pregnant patients with traumatic brain injury (TBI) are an especially vulnerable population, and their management is complex, with multiple special considerations that must be taken into account. These include but are not limited to alterations in maternal physiology that occur with pregnancy, potential teratogenicity of pharmacologic therapies and diagnostic studies using ionizing radiation, need for fetal monitoring, Rh immunization status, placental abruption, and preterm labor. Despite these challenges, evidence regarding management of the pregnant patient with a TBI is lacking, limited to only case reports/series and retrospective analyses. Despite this uncertainty, expert opinion on management of these patients seems to be that, overall, the standard therapies for management of TBI are safe and effective in pregnancy, with a few notable exceptions described in this chapter. Significant work is needed to continue to develop best-practice and evidence-based guidelines for the management of TBI pregnancy.

An interactive nomogram to predict healthcare-associated infections in ICU patients: A multicenter study in GuiZhou Province, China

Objective

To develop and validate an interactive nomogram to predict healthcare-associated infections (HCAIs) in the intensive care unit (ICU).

Methods

A multicenter retrospective study was conducted to review 2017 data from six hospitals in Guizhou Province, China. A total of 1,782 ICU inpatients were divided into either a training set (n = 1,189) or a validation set (n = 593). The patients’ demographic characteristics, basic clinical features from the previous admission, and their need for bacterial culture during the current admission were extracted from electronic medical records of the hospitals to predict HCAI. Univariate and multivariable analyses were used to identify independent risk factors of HCAI in the training set. The multivariable model’s performance was evaluated in both the training set and the validation set, and an interactive nomogram was constructed according to multivariable regression model. Moreover, the interactive nomogram was used to predict the possibility of a patient developing an HCAI based on their prior admission data. Finally, the clinical usefulness of the interactive nomogram was estimated by decision analysis using the entire dataset.

Results

The nomogram model included factor development (local economic development levels), length of stay (LOS; days of hospital stay), fever (days of persistent fever), diabetes (history of diabetes), cancer (history of cancer) and culture (the need for bacterial culture). The model showed good calibration and discrimination in the training set [area under the curve (AUC), 0.871; 95% confidence interval (CI), 0.848–0.894] and in the validation set (AUC, 0.862; 95% CI, 0.829–0.895). The decision curve demonstrated the clinical usefulness of our interactive nomogram.

Conclusions

The developed interactive nomogram is a simple and practical instrument for quantifying the individual risk of HCAI and promptly identifying high-risk patients.

Management of Severe Traumatic Brain Injury in Pregnancy: A Body with Two Lives

Traumatic brain injury is the major contributing factor in non-obstetric mortality in developing countries. Approximately 20% of maternal mortality is directly correlated to injuries. Road traffic accidents and domestic violence are the most common nonlethal injuries that can threaten either the maternal or foetal life, and such events occur in one out of every 12 pregnancies. The treatment of severe traumatic brain injury in pregnancy requires a multidisciplinary team approach. The management of a pregnant trauma patient warrants consideration of several issues specific to pregnancy, such as the alterations in the maternal physiology and anatomy. In the case of maternal cardiac arrest with amniotic fluid embolism, intact neonatal survival is linked with the timing of caesarean section after maternal cardiac arrest. Moreover, the decision for perimortem caesarean section is clear after maternal cardiac arrest. The foetal survival rate is 67% if the operation is done before 15 min of cardiopulmonary compromise has occurred, and it drops to 40% at the duration range of 16–25 min. Whether minor or severe, traumatic brain injury during pregnancy is associated with unfavourable maternal outcomes. Injuries considered minor for the general population are not minor for pregnant women. Therefore, these patients should be intensively monitored, and multidisciplinary approaches should always be involved.

The incidence of hyperthermia during craniotomy

There is evidence that even mild hyperthermia may exacerbate brain injury. There seem reasonable grounds for considering patients undergoing craniotomy as at risk for brain injury. A retrospective observational study was undertaken to measure the incidence of mild hyperthermia in craniotomy cases in which the patient was initially normothermic. Auckland City Hospital's database of electronic anaesthetic records was searched for adult patients who were normothermic (≤37°C) prior to undergoing craniotomy procedures. For each case, demographic data, intraoperative naso- or oropharyngeal temperature measurements, and paracetamol use were extracted. We identified the proportion of patients whose temperature rose to exceed normal (>37°C) and subdivided that group into the proportion in whom the temperature rose to ≥38°C. Two thousand, nine hundred and thirty-five craniotomy cases began their operations while normothermic and had adequate temperature data collected. There were 984 (33.5%) cases that had at least one temperature reading >37°C, for a mean (standard deviation [SD]) time of 66.0 (64.6) minutes, and 49 (1.7%) cases that had at least one reading ≥38°C for a mean (SD) time of 40.4 (38.1) minutes. The majority (77.8%) who became mildly hyperthermic remained so at the end of the procedure. New mild hyperthermia occurs commonly during craniotomy. In view of the compelling evidence of potential harm arising from mild hyperthermia in brain injury, these findings suggest an opportunity for practice improvement in the anaesthetic management of craniotomy patients. Reasonable steps should be taken by anaesthetists to avoid intraoperative hyperthermia of any degree.

Population pharmacokinetics of intravenous paracetamol in critically ill patients with traumatic brain injury

PURPOSE

High-dose paracetamol (6 g/day) is a low-cost intervention that may prevent pyrexia. The purpose of this study was to describe the pharmacokinetics of high-dose intravenous paracetamol, in patients with traumatic brain injury (TBI).

MATERIALS AND METHODS

A clinical pharmacokinetic study in adult patients with TBI was performed as a sub-study to a prospective, phase 2B, randomized placebo-controlled study (PARITY). Patients received 1 g of intravenous paracetamol or 0.9% sodium chloride every 4 h for 72 h.

RESULTS

All patients were included in the pharmacokinetic sub-study. The mean age, weight and area under the concentration-time curve for the sampled dosing interval were 34.5 yr, 82.3 kg and 39.9 ± 19.8 mg.h/L, respectively. The concentrations observed in the study patients were well below the threshold of toxicity and there was no evidence of accumulation of paracetamol. Paracetamol clearance was found to be high and variable (25.7 L.h^-1, coefficient of variation (CV) 40.9%), and a wide range of volume of distribution observed (27.6 L, CV 30.6%). A relationship between lower Glasgow coma scores and higher clearance of paracetamol was observed.

CONCLUSION

Due to altered pharmacokinetics, patients experiencing severe TBI may require a higher dose of paracetamol to achieve drug exposure that results in preventing pyrexia.

Reduction of hyperthermia in pediatric patients with severe traumatic brain injury: a quality improvement initiative

OBJECTIVE Severe traumatic brain injury remains a leading cause of morbidity and mortality in the pediatric population. Providers focus on reducing secondary brain injury by avoiding hypoxemia, avoiding hypotension, providing normoventilation, treating intracranial hypertension, and reducing cerebral metabolic demand. Hyperthermia is frequently present in patients with severe traumatic brain injury, contributes to cerebral metabolic demand, and is associated with prolonged hospital admission as well as impaired neurological outcome. The objective of this quality improvement initiative was to reduce the duration of hyperthermia for pediatric patients with severe traumatic brain injury during the initial 72 hours of admission to the pediatric intensive care unit. METHODS A retrospective chart review was performed to evaluate the incidence and duration of hyperthermia within a preintervention cohort. The retrospective phase was followed by three 6-month intervention periods (intervention Phase 1, the maintenance phase, and intervention Phase 2). Intervention Phase 1 entailed placement of a cooling blanket on the bed prior to patient arrival and turning it on once the patient's temperature rose above normothermia. The maintenance phase focused on sustaining the results of Phase 1. Intervention Phase 2 focused on total prevention of hyperthermia by initiating cooling blanket use immediately upon patient arrival to the intensive care unit. RESULTS The median hyperthermia duration in the preintervention cohort (n = 47) was 135 minutes. This was reduced in the Phase 1 cohort (n = 9) to 45 minutes, increased in the maintenance phase cohort (n = 6) to 88.5 minutes, and decreased again in the Phase 2 cohort (n = 9) to a median value of 0 minutes. Eight percent of patients in the intervention cohorts required additional sedation to tolerate the cooling blanket. Eight percent of patients in the intervention cohorts became briefly hypothermic while on the cooling blanket. No patient required neuromuscular blockade to tolerate the cooling blanket, experienced an arrhythmia, had new coagulopathy, or developed a pressure ulcer. CONCLUSIONS The placement of a cooling blanket on the bed prior to patient arrival and actively targeting normothermia successfully reduced the incidence and duration of hyperthermia with minimal adverse events.

The influence of hyperthermia on intracranial pressure, cerebral oximetry and cerebral metabolism in traumatic brain injury

BACKGROUND

Hyperthermia is a common secondary insult in traumatic brain injury (TBI). The aim was to evaluate the relationship between hyperthermia and intracranial pressure (ICP), and if intracranial compliance and cerebral blood flow (CBF) pressure autoregulation affected that relationship. The relationships between hyperthermia and cerebral oximetry (BtipO2) and cerebral metabolism were also studied.

METHODS

A computerized multimodality monitoring system was used for data collection at the neurointensive care unit. Demographic and monitoring data (temperature, ICP, blood pressure, microdialysis, BtipO2) were analyzed from 87 consecutive TBI patients. ICP amplitude was used as measure of compliance, and CBF pressure autoregulation status was calculated using collected blood pressure and ICP values. Mixed models and comparison between groups were used.

RESULTS

The influence of hyperthermia on intracranial dynamics (ICP, brain energy metabolism, and BtipO2) was small, but individual differences were seen. Linear mixed models showed that hyperthermia raises ICP slightly more when temperature increases in the groups with low compliance and impaired CBF pressure autoregulation. There was also a tendency (not statistically significant) for increased BtipO2, and for increased pyruvate and lactate, with higher temperature, while the lactate/pyruvate ratio and glucose were stable.

CONCLUSIONS

The major finding was that the effects of hyperthermia on intracranial dynamics (ICP, brain energy metabolism, and BtipO2) were not extensive in general, but there were exceptional cases. Hyperthermia treatment has many side effects, so it is desirable to identify cases in which hyperthermia is dangerous. Information from multimodality monitoring may be used to guide treatment in individual patients.

Paracetamol in fever in critically ill patients-an update

Fever, which is arbitrary defined as an increase in body temperature above 38.3°C, can affect up to 90% of patients admitted in intensive care unit. Induction of fever is mediated by the release of pyrogenic cytokines (tumor necrosis factor α, interleukin 1, interleukin 6, and interferons). Fever is associated with increased length of stay in intensive care unit and with a worse outcome in some subgroups of patients (mainly neurocritically ill patients). Although fever can increase oxygen consumption in unstable patients, on the contrary, it can activate physiologic systems that are involved in pathogens clearance. Treatments to reduce fever include the use of antipyretics. Thus, the reduction of fever might reduce the ability to develop an efficient host response. This balance, between harms and benefits, has to be taken into account every time we decide to treat or not to treat fever in a given patient. Among the antipyretics, paracetamol is one of the most common used. Paracetamol is a synthetic, nonopioid, centrally acting analgesic, and antipyretic drug. Its antipyretic effect occurs because it inhibits cyclooxygenase-3 and the prostaglandin synthesis, within the central nervous system, resetting the hypothalamic heat-regulation center. In this clinical review, we will summarize the use of paracetamol as antipyretic in critically ill patients (sepsis, trauma, neurological, and medical).

Pyrexia: aetiology in the ICU

Elevation in core body temperature is one of the most frequently detected abnormal signs in patients admitted to adult ICUs, and is associated with increased mortality in select populations of critically ill patients. The definition of an elevated body temperature varies considerably by population and thermometer, and is commonly defined by a temperature of 38.0 °C or greater. Terms such as hyperthermia, pyrexia, and fever are often used interchangeably. However, strictly speaking hyperthermia refers to the elevation in body temperature that occurs without an increase in the hypothalamic set point, such as in response to specific environmental (e.g., heat stroke), pharmacologic (e.g., neuroleptic malignant syndrome), or endocrine (e.g., thyrotoxicosis) stimuli. On the other hand, pyrexia and fever refer to the classical increase in body temperature that occurs in response to a vast list of infectious and noninfectious aetiologies in association with an increase in the hypothalamic set point. In this review, we examine the contemporary literature investigating the incidence and aetiology of pyrexia and hyperthermia among medical and surgical patients admitted to adult ICUs with or without an acute neurological condition. A temperature greater than 41.0 °C, although occasionally observed among patients with infectious or noninfectious pyrexia, is more commonly observed in patients with hyperthermia. Most episodes of pyrexia are due to infections, but incidence estimates of infectious and noninfectious aetiologies are limited by studies with small sample size and inconsistent reporting of noninfectious aetiologies. Pyrexia commonly triggers a full septic work-up, but on its own is a poor predictor of culture-positivity. In order to improve culturing practices, and better guide the diagnostic approach to critically ill patients with pyrexia, additional research is required to provide more robust estimates of the incidence of infectious and noninfectious aetiologies, and their relationship to other clinical features (e.g., leukocytosis). In the meantime, using existing literature, we propose an approach to identifying the aetiology of pyrexia in critically ill adults.

Temperature Management in the Neurointensive Care Unit

OPINION STATEMENT

Fever in the neurocritical care unit has a high prevalence and is associated with worse outcomes in patients with severe neurologic illness. While it is well accepted that fever is associated with worse outcomes in this patient population, it is unclear if aggressive temperature management will improve outcomes. Temperature should be monitored routinely in this high-risk population, fever worked up appropriately to identify infectious etiology, and reasonable measures taken to control elevated temperature. While infection is a common source of fever in patients with significant neurologic illness, the fever may also be exacerbated by the underlying brain injury. The clinician must decide at which point to initiate fever control measures, how aggressively to manage the fever, and which temperature to target for normothermia. Several pharmacological agents are available as first-line therapy. Depending on the degree and severity of the febrile response, advanced temperature-control devices should be added to pharmacological measures. Several types of temperature-control devices are available, including invasive (intravascular catheters) and noninvasive (external cooling pads) technologies. The clinician should utilize both pharmacologic and device-based temperature therapies to minimize the amount of time spent in a febrile state and help to mitigate the secondary brain injury brought on by fever.

The Effect of Paracetamol on Core Body Temperature in Acute Traumatic Brain Injury: A Randomised, Controlled Clinical Trial

Background

Strategies to prevent pyrexia in patients with acute neurological injury may reduce secondary neuronal damage. The aim of this study was to determine the safety and efficacy of the routine administration of 6 grams/day of intravenous paracetamol in reducing body temperature following severe traumatic brain injury, compared to placebo.

Methods

A multicentre, randomised, blind, placebo-controlled clinical trial in adult patients with traumatic brain injury (TBI). Patients were randomised to receive an intravenous infusion of either 1g of paracetamol or 0.9% sodium chloride (saline) every 4 hours for 72 hours. The primary outcome was the mean difference in core temperature during the study intervention period.

Results

Forty-one patients were included in this study: 21 were allocated to paracetamol and 20 to saline. The median (interquartile range) number of doses of study drug was 18 (17–18) in the paracetamol group and 18 (16–18) in the saline group (P = 0.85). From randomisation until 4 hours after the last dose of study treatment, there were 2798 temperature measurements (median 73 [67–76] per patient). The mean ± standard deviation temperature was 37.4±0.5°C in the paracetamol group and 37.7±0.4°C in the saline group (absolute difference -0.3°C; 95% confidence interval -0.6 to 0.0; P = 0.09). There were no significant differences in the use of physical cooling, or episodes of hypotension or hepatic abnormalities, between the two groups.

Conclusion

The routine administration of 6g/day of intravenous paracetamol did not significantly reduce core body temperature in patients with TBI.

Trial Registration

Australian New Zealand Clinical Trials Registry ACTRN12609000444280

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.

'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.

Modest cooling therapies (35ºC to 37.5ºC) for traumatic brain injury

BACKGROUND

Animal models of traumatic brain injury suggest that induced normothermia (36.5 or 37 ºC), compared to induced hyperthermia (39 ºC), improves histopathological and neurobehavioural outcomes. Observational clinical studies of patients with TBI suggest an association between raised body temperature and unfavourable outcome, although this relationship is inconsistent.

OBJECTIVES

To assess the effects of modest cooling therapies (defined as any drug or physical therapy aimed at maintaining body temperature between 35 ºC and 37.5 ºC) when applied to patients in the first week after traumatic brain injury.

SEARCH METHODS

The most recent search was run on 23(rd) September 2013. We searched the Cochrane Injuries Group's Specialised Register, The Cochrane Library (CENTRAL), MEDLINE (OvidSP), Embase (OvidSP), ISI WOS: SCI-EXPANDED (1970) & CPCI-S (1990), PubMed and trials registries together with reference checking.

SELECTION CRITERIA

All completed randomised, controlled and placebo-controlled trials published or unpublished, where modest cooling therapies were applied in the first week after traumatic brain injury.

DATA COLLECTION AND ANALYSIS

Two authors independently applied the selection criteria to relevant trials.

MAIN RESULTS

We were unable to find any randomised controlled trials of modest cooling therapies after traumatic brain injury.

AUTHORS' CONCLUSIONS

In order to further explore the preliminary findings provided by animal models and observational clinical studies that suggests there may be a beneficial effect of modest cooling for TBI, randomised trials designed to explore the effect of these interventions on patient-centred outcomes are needed.

The epidemiology of spontaneous fever and hypothermia on admission of brain injury patients to intensive care units: a multicenter cohort study

OBJECTIVES

Fever and hypothermia (dysthermia) are associated with poor outcomes in patients with brain injuries. The authors sought to study the epidemiology of dysthermia on admission to the intensive care unit (ICU) and the effect on in-hospital case fatality in a mixed cohort of patients with brain injuries.

METHODS

The authors conducted a multicenter retrospective cohort study in 94 ICUs in the United States. Critically ill patients with neurological injuries, including acute ischemic stroke (AIS), aneurysmal subarachnoid hemorrhage (aSAH), intracerebral hemorrhage (ICH), and traumatic brain injury (TBI), who were older than 17 years and consecutively admitted to the ICU from 2003 to 2008 were selected for analysis.

RESULTS

In total, 13,587 patients were included in this study; AIS was diagnosed in 2973 patients (22%), ICH in 4192 (31%), aSAH in 2346 (17%), and TBI in 4076 (30%). On admission to the ICU, fever was more common among TBI and aSAH patients, and hypothermia was more common among ICH patients. In-hospital case fatality was more common among patients with hypothermia (OR 12.7, 95% CI 8.4-19.4) than among those with fever (OR 1.9, 95% CI 1.7-2.1). Compared with patients with ICH (OR 2.0, 95% CI 1.8-2.3), TBI (OR 1.5, 95% CI 1.3-1.8), and aSAH (OR 1.4, 95% CI 1.2-1.7), patients with AIS who developed fever had the highest risk of death (OR 3.1, 95% CI 2.5-3.7). Although all hypothermic patients had an increased mortality rate, this increase was not significantly different across subgroups. In a multivariable analysis, when adjusted for all other confounders, exposure to fever (adjusted OR 1.3, 95% CI 1.1-1.5) or hypothermia (adjusted OR 7.8, 95% CI 3.9-15.4) on admission to the ICU was found to be significantly associated with in-hospital case fatality.

CONCLUSIONS

Fever is frequently encountered in the acute phase of brain injury, and a small proportion of patients with brain injuries may also develop spontaneous hypothermia. The effect of fever on mortality rates differed by neurological diagnosis. Both early spontaneous fever and hypothermia conferred a higher risk of in-hospital death after brain injury.

Pharmacotherapy of fever control among hospitalized adult patients

INTRODUCTION

Fever is common and associated with increased mortality among hospitalized adults. This article will review the pharmacotherapy of commonly prescribed antipyretic drugs including the rationale for and against temperature control in febrile adults, as well as the evidence associated with fever control in specific patient populations.

AREAS COVERED

Though fever is common, the molecular basis of pyrexia, and the interaction of these pathways with commonly prescribed antipyretic drugs are not fully understood. Furthermore, while experimental and clinical studies clearly demonstrate that pyrexia is harmful in select patients, available clinical trial data are unable to suggest an evidence-based approach to the treatment of fever. Interestingly, this also applies to patients with an acute neurologic injury wherein the treatment of fever with antipyretic therapy has become a common management strategy.

EXPERT OPINION

Few adequately powered clinical trials have investigated temperature control strategies in febrile patients. Therefore, it is not possible to define an evidence-based approach to the control of fever in hospitalized adults. Further clinical and translational research is required to identify the patients most likely to benefit from a strategy of fever control versus permissive hyperthermia, and to determine the antipyretic therapies associated with the greatest improvement in outcome.

Keep the brain cool--endovascular cooling in patients with severe traumatic brain injury: a case series study

BACKGROUND

As brain temperature is reported to be extensively higher than core body temperature in traumatic brain injury (TBI) patients, posttraumatic hyperthermia is of particular relevance in the injured brain.

OBJECTIVE

To study the influence of prophylactic normothermia on brain temperature and the temperature gradient between brain and core body in patients with severe TBI using an intravascular cooling system and to assess the relationship between brain temperature and intracranial pressure (ICP) under endovascular temperature control.

METHODS

Prospective case series study conducted in the neurologic intensive care unit of a tertiary care university hospital. Seven patients with severe TBI with a Glasgow Coma Scale score of 8 or less were consecutively enrolled. Prophylactic normothermia, defined as a target temperature of 36.5°C, was maintained using an intravascular cooling system. Simultaneous measurements of brain and urinary bladder temperature and ICP were taken over a 72-hour period.

RESULTS

The mean bladder temperature in normothermic patients was 36.3 ± 0.4°C, and the mean brain temperature was determined as 36.4 ± 0.5°C. The mean temperature difference between brain and bladder was 0.1°C. We found a significant direct correlation between brain and bladder temperature (r = 0.95). In 52.4% of all measurements, brain temperature was higher than core body temperature. The mean ICP was 18 ± 8 mm Hg.

CONCLUSION

Intravascular temperature management stabilizes both brain and body core temperature; prophylactic normothermia reduces the otherwise extreme increase of intracerebral temperature in patients with severe TBI. The intravascular cooling management proved to be an efficacious and feasible method to control brain temperature and to avoid hyperthermia in the injured brain. We could not find a statistically significant correlation between brain temperature and ICP.

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

BACKGROUND

Animal studies have shown that even a small temperature elevation of 1°C can cause detrimental effects after brain injury. Since the skull acts as a potential thermal insulator, we hypothesized that decompressive hemicraniectomy facilitates surface cooling and lowers brain temperature.

METHODS

Forty-eight patients with severe brain injury (TBI = 38, ICH = 10) with continuous brain temperature monitoring were retrospectively studied and grouped into "hemicraniectomy" (n = 20) or "no hemicraniectomy" (n = 28) group. The paired measurements of core body (T Core) and brain (T Br) temperature were recorded at 1-min intervals over 12 ± 7 days. As a surrogate measure for the extent of surface heat loss from the brain, ∆T Core-Br was calculated as the difference between T Core and T Br with each recording. In order to accommodate within-patient temperature correlations, mixed-model regression was used to assess the differences in ∆T Core-Br between those with and without hemicraniectomy, adjusted for core body temperature and diagnosis.

RESULTS

A total of 295,883 temperature data pairs were collected (median [IQR] per patient: 5047 [3125-8457]). Baseline characteristics were similar for age, sex, diagnosis, incidence of sepsis, Glasgow Coma Scale score, ICU mortality, and ICU length of stay between the two groups. The mean difference in ∆T Core-Br was 1.29 ± 0.87°C for patients with and 0.80 ± 0.86°C for patients without hemicraniectomy (P < 0.0001). In mixed-model regression, accounting for temperature correlations within patients, hemicraniectomy and higher T Core were associated with greater ∆T Core-Br (hemicraniectomy: estimated effect = 0.60, P = 0.003; T Core: estimated effect = 0.21, P < 0.0001).

CONCLUSIONS

Hemicraniectomy is associated with modestly but significantly lower brain temperature relative to core body temperature.

Risk factors for posttraumatic vasospasm

OBJECT

Posttraumatic vasospasm (PTV) is an underrecognized cause of ischemic damage after severe traumatic brain injury (TBI) that independently predicts poor outcome. There are, however, no guidelines for PTV screening and management, partly due to limited understanding of its pathogenesis and risk factors.

METHODS

A database review of 46 consecutive cases of severe TBI in pediatric and adult patients was conducted to identify risk factors for the development of PTV. Univariate analysis was performed to identify potential risk factors for PTV, which were subsequently analyzed using a multivariate logistic regression model to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Fever on admission was an independent risk factor for development of PTV (OR 22.2, 95% CI 1.9-256.8), and patients with hypothermia on admission did not develop clinically significant vasospasm during their hospital stay. The presence of small parenchymal contusions was also an independent risk factor for PTV (OR 7.8, 95% CI 0.9-69.5), whereas the presence of subarachnoid hemorrhage or other patterns of intracranial injury were not. Other variables, such as age, sex, ethnicity, degree of TBI severity, or admission laboratory values, were not independent predictors for the development of clinically significant PTV.

CONCLUSIONS

Independent risk factors for PTV include parenchymal contusions and fever. These results suggest that diffuse mechanical injury and activation of inflammatory pathways may be underlying mechanisms for the development of PTV, and that a subset of patients with these risk factors may be an appropriate population for aggressive screening. Further studies are needed to determine if treatments targeting fever and inflammation may be effective in reducing the incidence of vasospasm following severe TBI.

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

Temperature disturbances are common in patients with severe traumatic brain injury. The possibility of an adaptive, potentially beneficial role for fever in patients with severe brain trauma has been dismissed, but without good justification. Fever might, in some patients, confer benefit. A cadre of clinicians and scientists met to debate the clinically relevant, but often controversial issue about whether raised brain temperature after human traumatic brain injury (TBI) should be regarded as "good or bad" for outcome. The objective was to produce a consensus document of views about current temperature measurement and pyrexia treatment. Lectures were delivered by invited speakers with National and International publication track records in thermoregulation, neuroscience, epidemiology, measurement standards and neurocritical care. Summaries of the lectures and workshop discussions were produced from transcriptions of the lectures and workshop discussions. At the close of meeting, there was agreement on four key issues relevant to modern temperature measurement and management and for undergirding of an evidence-based practice, culminating in a consensus statement. There is no robust scientific data to support the use of hypothermia in patients whose intracranial pressure is controllable using standard therapy. A randomized clinical trial is justified to establish if body cooling for control of pyrexia (to normothermia) vs moderate pyrexia leads to a better patient outcome for TBI patients.

Temperature patterns in the early postresuscitation period after pediatric inhospital cardiac arrest

OBJECTIVE

To describe the prevalence of postarrest hyperthermia among children during the first 24 hrs after inhospital cardiac arrest and to determine the association of persistent postarrest hyperthermia with neurologic outcome and death before hospital discharge.

DESIGN

Multicenter, national registry of inhospital cardiopulmonary resuscitation.

SETTING

A total of 196 hospitals reporting to the American Heart Association's National Registry of Cardiopulmonary Resuscitation from January 1, 2005 to December 31, 2007.

PATIENTS

A total of 547 pediatric patients who suffered inhospital pulseless cardiac arrests reported to the National Registry of Cardiopulmonary Resuscitation, who survived resuscitative efforts and who had the maximum and the minimum temperature in the first 24 hrs postresuscitation reported to the National Registry of Cardiopulmonary Resuscitation.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Among 547 children with pulseless cardiac arrests, 238 (43.5%) had at least one temperature of ≥38°C, and 30 (5.5%) had "persistent hyperthermia" (i.e., both the minimum and the maximum temperature of ≥38°C) during the first 24 hrs postarrest. After adjusting for potential confounders by multivariate logistic regression, persistent hyperthermia in the first 24 hrs postarrest was associated with unfavorable neurologic outcome (adjusted odds ratio, 2.7; 95% confidence interval, 1.1-6.7), but not with death before hospital discharge (adjusted odds ratio, 1.2; 95% confidence interval, 0.4-3.4).

CONCLUSIONS

Despite current guidelines to avoid postarrest hyperthermia, a temperature of ≥38°C occurred commonly among children in the first 24 hrs postarrest. Persistent postarrest hyperthermia was associated with unfavorable neurologic outcomes, even after controlling for potential confounding factors.

Fluid balance, complications, and brain tissue oxygen tension monitoring following severe traumatic brain injury

BACKGROUND

Refractory intracranial hypertension (RIH) frequently complicates severe traumatic brain injury (TBI) and is associated with worse outcomes. Aggressive fluid resuscitation contributes to the development of peripheral and pulmonary edema, but an effect on cerebral edema is not well established. Some clinicians, including advocates of the "Lund Concept", practice fluid restriction as a means of limiting cerebral edema and reducing intracranial pressure (ICP).

METHODS

We performed a retrospective cohort study involving 41 consecutive patients with severe TBI to assess the association between fluid balance and the development of RIH or pulmonary complications.

RESULTS

There was no difference in cumulative fluid balance between patients who did, or did not, develop RIH. Patients in the tertile with the largest fluid balance were no more likely to develop RIH than those in the more restrictive groups (HR 1.05, 0.78-1.42, P = 0.73). In contrast, there was a strong association between fluid balance and the development of bilateral pulmonary infiltrates, which persisted even after adjusting for Glasgow Coma Scale and Injury Severity Score (HR 1.69, 1.40-2.04, P < 0.0001). The use of P(bt)O(2) monitors to guide therapy was associated with higher cumulative fluid balance, more vasopressor use, and the development of both pulmonary edema and RIH.

CONCLUSION

We found no association between cumulative fluid balance and the development of RIH. However, more judicious volume management has the potential to reduce the occurrence of pulmonary complications. Further research is needed to clarify optimal approaches to fluid management among patients with severe TBI and to guide the interpretation and integration of information derived from P(bt)O(2) monitors.

Judgments of critical care nurses about risk for secondary brain injury

BACKGROUND

Interdisciplinary care for patients with traumatic brain injury focuses on treating the primary brain injury and limiting further brain damage from secondary injury. Intensive care unit nurses have an integral role in preventing secondary brain injury; however, little is known about factors that influence nurses' judgments about risk for secondary brain injury.

OBJECTIVE

To investigate which physiological and situational variables influence judgments of intensive care unit nurses about patients' risk for secondary brain injury, management solely with nursing interventions, and management by consulting another member of the health care team.

METHODS

A multiple segment factorial survey design was used. Vignettes reflecting the complexity of real-life scenarios were randomly generated by using different values of each independent variable. Surveys containing the vignettes were sent to nurses at 2 level I trauma centers. Multiple regression was used to determine which variables influenced judgments about secondary brain injury.

RESULTS

Judgments about risk for secondary brain injury were influenced by a patient's oxygen saturation, intracranial pressure, cerebral perfusion pressure, mechanism of injury, and primary diagnosis, as well as by nursing shift. Judgments about interventions were influenced by a patient's oxygen saturation, intracranial pressure, and cerebral perfusion pressure and by nursing shift. The initial judgments made by nurses were the most significant variable predictive of follow-up judgments.

CONCLUSIONS

Nurses need standardized, evidence-based content for management of secondary brain injury in critically ill patients with traumatic brain injury.

Intensive care unit nurse characteristics impacting judgments about secondary brain injury

Although intensive care unit nurses have an integral role in preventing secondary brain injury when caring for critically ill traumatic brain injury patients, nursing practice varies and little research has examined if individual nurse characteristics affect judgments about secondary brain injury. The purpose of this study was to investigate how intensive care unit nurse characteristics influence judgments when managing secondary brain injury. A factorial survey research design was used to administer surveys to intensive care nurses from 2 level I trauma centers. Nursing shift and number of years in the intensive care unit were significant predictors of judgments. Understanding the role of nurse characteristics is important in future educational and research efforts aimed at evidence-based management of secondary brain injury.

Spreading depolarizations and late secondary insults after traumatic brain injury

Here we investigated the incidence of cortical spreading depolarizations (spreading depression and peri-infarct depolarization) after traumatic brain injury (TBI) and their relationship to systemic physiologic values during neurointensive care. Subdural electrode strips were placed on peri-contusional cortex in 32 patients who underwent surgical treatment for TBI. Prospective electrocorticography was performed during neurointensive care with retrospective analysis of hourly nursing chart data. Recordings were 84 hr (median) per patient and 2,503 hr in total. In 17 patients (53%), 280 spreading depolarizations (spreading depressions and peri-infarct depolarizations) were observed. Depolarizations occurred in a bimodal pattern with peak incidence on days 1 and 7. The probability of a depolarization occurring increased significantly as a function of declining mean arterial pressure (MAP; R(2) = 0.78; p < 0.001) and cerebral perfusion pressure (R(2) = 0.85; p < 0.01), and increasing core temperature (R(2) = 0.44; p < 0.05). Depolarization probability was 7% for MAP values of >100 mm Hg but 33% for MAP of < or =70 mm Hg. Temperatures of < or =38.4 degrees C were associated with a 21% depolarization risk, compared to 63% for >38.4 degrees C. Intracranial pressures were higher in patients with depolarizations (18.3 +/- 9.3 vs. 13.5 +/- 6.7 mm Hg; p < 0.001). We conclude that depolarization phenomena are a common cortical pathology in TBI. Their association with lower perfusion levels and higher temperatures suggests that the labile balance of energy supply and demand is an important determinant of their occurrence. Monitoring of depolarizations might serve as a functional measure to guide therapeutic efforts and their blockade may provide an additional line of defense against the effects of secondary insults.

Temperature disturbances in traumatic brain injury: relationship to secondary insults, barbiturate treatment and outcome

OBJECTIVES

To describe the occurrence of spontaneous hyper- and hypothermia in patients with traumatic brain injury using a computerized data collecting system, to show how temperature correlates with other secondary insults, to describe how temperature affects outcome and to show how barbiturate treatment influences those analyses.

METHODS

Patients with > or = 54 hours of valid monitoring within the first 120 hours after trauma (one value/min) for temperature, intracranial pressure, cerebral perfusion pressure, systolic blood pressure, mean blood pressure and heart rate were included. Correlation analyses were performed between temperature and other secondary insult variables. The non-linear relationship between temperature and outcome (measured by Glasgow outcome scale 6 months post-trauma) was illustrated using a neural network.

RESULTS

Of the 53 patients, 44 experienced hyperthermia (>38 degrees C) and 29 experienced hypothermia (<36 degrees C). Hyperthermia correlated with occurrence of high blood pressure and high CPP. In individuals, hyperthermia also correlated with ICP and tachycardia. There was a trend towards better outcome for patients with normal temperature than those with hyper- or hypothermia (favorable outcome 64% versus 29 and 33% respectively). When patients treated with barbiturates were excluded, 60% showed favorable outcome in the hypothermia group as well. Barbiturate treatment also confounded analyses regarding temperature and other secondary insults.

DISCUSSION

Patients with hyperthermia, hypertension, high CPP and tachycardia may suffer from a hyperdynamic state. This may worsen outcome and hence clinical awareness is important. Barbiturate treatment confounds several analyses which have not been shown before. We recommend those patients to be analysed separately in future studies.

Induced normothermia attenuates intracranial hypertension and reduces fever burden after severe traumatic brain injury

INTRODUCTION

Hyperthermia following a severe traumatic brain injury (TBI) is common, potentiates secondary injury, and worsens neurological outcome. Conventional fever treatment is often ineffective. An induced normothermia protocol, utilizing intravascular cooling, was used to assess the impact on fever incidence and intracranial pressure (ICP) in patients with severe TBI.

METHODS

A comparative cohort study of 21 adult patients with severe TBI (GCS <or= 8) treated with induced normothermia [36-36.5 degrees C rectal probe setting; intravascular cooling catheter (CoolLine, Alsius Corporation, Irvine, CA)] were matched by age, gender, and severity of injury to 21 historical control severe TBI patients treated with conventional fever control methods. ICP was measured via an external ventricular catheter and time duration for ICP > 25 mmHg was calculated for the initial 72-h monitoring period. Non-parametric rank tests were performed.

RESULTS

Mean (+/-SD) or median [range] demographics did not differ between groups [total N = 42 (6 female, 36 male, age 36.4 +/- 14.8 years and initial GCS 7 [3-8], median and range]. Fever burden in the first 3 days (time >38 degrees C) in the induced normothermia versus control group was significantly less at 1.6% versus 10.6%, respectively (P = 0.03). Mean ICP for patients with induced normothermia versus control was 12.74 +/- 4.0 and 16.37 +/- 6.9 mmHg, respectively. Furthermore, percentage of time with ICP > 25 mmHg was significantly less in the induced normothermia group (P = 0.03).

CONCLUSION

Induced normothermia (fever prophylaxis via intravascular cooling catheter) is effective in reducing fever burden and may offer a means to attenuate secondary injury, as evidenced by a reduction in the intracranial hypertension burden.

[Deleterious role of hyperthermia in neurocritical care]

Fever is a secondary brain injury and may worsen neurological prognosis of neurological intensive care unit (NICU) patients. In response to an immunological threat, fever associates various physiological reactions, including hyperthermia. Its definition may vary but the most commonly used threshold is 37.5 degrees C. In animal studies, hyperthermia applied before, during or after cerebral ischemia may increase the volume of ischemic lesions. The mechanism of this effect may include increase in blood brain barrier permeability, increase in excitatory amino acid release and increase in free radical production. In NICU patients, fever is frequent, occurring in up to 20-30% of patients. Moreover, after haemorrhagic stroke, fever has been reported in 40-50% of patients. In half of the patients, fever may be related to an infectious cause but in more than 25% of patients, hyperthermia may be of central origin. After ischemic stroke, hyperthermia during the first 72 hours is associated with an increase in infarct size and increase in morbidity and mortality. This holds true also after subarachnoid haemorrhage. After traumatic brain injury, fever is not related to mortality but may increase morbidity. Whereas no causal link has been established between fever and unfavourable outcome, it seems reasonable to treat hyperthermia in patients suffering from brain injuries. In such patients, antipyretics have a moderate efficacy. In case of failure, they should be replaced by physical cooling techniques.

The significance of altered temperature after traumatic brain injury: an analysis of investigations in experimental and human studies: part 2

Raised body temperature is a common occurrence after severe traumatic brain injury (TBI). It is widely accepted that experimental evidence points to a harmful effect of raised temperature both during and after TBI. Consequently, the policy of many neurocritical care units is to implement therapies for body temperature control. This article reviews the evidence that links spontaneous temperature changes with worsened outcome after experimentally-induced and human brain trauma. The current evidence-base and rationale for treatment of raised temperature after TBI is presented with discussion positing areas for further work to explore the notion that raised temperature may not be deleterious in all neurosurgical patients.

Fever control and its impact on outcomes: what is the evidence?

Fever is common in a variety of neurological disorders. There is abundant experimental evidence suggesting that fever leads to, or exacerbates, neuronal injury in conditions such as cerebral ischemia and traumatic brain injury. However, conclusive evidence linking control of fever to improved outcomes is lacking. It has been difficult to design studies looking at the impact of fever control on outcome, in part because traditional methods of fever control are ineffective. Recently, several new devices to control temperature have become available. These devices appear to be more effective than conventional means and might allow us to design studies that definitively answer the question: "Does controlling fever improve outcome?"

Changes in CSF composition during heat stress and fever in conscious rabbits

Elevation of brain temperature after stroke can lead to severe brain injury and even a moderate hyperthermia correlates with increased nervous damage. The role of endogenous cryogens in the pathways that down-regulate body temperature are of overwhelming interest in view of their effectiveness in protecting brain from such damage. The aim of the present work was to study whether heat stress (HS) or fever generates brain homeostatic responses aimed at counteracting the resulting rise in body temperature. Conscious rabbits, with cannulas chronically implanted in the cisterna magna and lateral ventricle, underwent HS (50 min, 40 degrees C) or were injected with 25 ng of endogenous pyrogen IL-1beta, while cerebrospinal fluid (CSF) levels of amino acids involved in central mechanisms of thermoregulation like taurine, GABA, aspartate and glutamate were monitored. The concentrations of some CSF cations (Na(+), K(+), Mg(2+) and Ca(2+)) were also determined in view of their purported role (sodium and calcium in particular) in establishing the thermal set point within the hypothalamus. Results show that during HS-induced hyperthermia, CSF taurine and GABA levels were significantly increased. On the contrary, IL-1beta caused an increase in CSF taurine and, concurrently, a decrease in CSF GABA. Aspartate and glutamate did not change in both conditions. Furthermore, among CSF cations, only calcium and sodium underwent changes. In particular, calcium content increased both in HS- and febrile-animals, while CSF sodium decreased significantly only under IL-1beta-injected treatment. In conclusion, GABA and taurine contribute as endogenous cryogens in a different fashion to the central mechanisms, which regulate dissipation of body heat in hyperthermia or heat production in fever, possibly in coordination with extracellular calcium and sodium.

Hyperthermia and central nervous system injury

Fever is a common occurrence in patients following brain and spinal cord injury (SCI). In intensive care units, large numbers of patients demonstrate febrile periods during the first several days after injury. Over the last several years, experimental studies have reported the detrimental effects of fever in various models of central nervous system (CNS) injury. Small elevations in temperature during or following an insult have been shown to worsen histopathological and behavioral outcome. Thus, the control of fever after brain or SCI may improve outcome if more effective strategies for monitoring and treating hyperthermia were developed. Because of the clinical importance of fever as a potential secondary injury mechanism, mechanisms underlying the detrimental effects of mild hyperthermia after injury have been evaluated. To this end, studies have shown that mild hyperthermia (>37 degrees C) can aggravate multiple pathomechanisms, including excitotoxicity, free radical generation, inflammation, apoptosis, and genetic responses to injury. Recent data indicate that gender differences also play a role in the consequences of secondary hyperthermia in animal models of brain injury. The observation that dissociations between brain and body temperature often occur in head-injured patients has again emphasized the importance of controlling temperature fluctuations after injury. Thus, increased emphasis on the ability to monitor CNS temperature and prevent periods of fever has gained increased attention in the clinical literature. Cooling blankets, body vests, and endovascular catheters have been shown to prevent elevations in body temperature in some patient populations. This chapter will summarize evidence regarding hyperthermia and CNS injury.

Clinical Features of Fever Associated With Poor Outcome in Severe Pediatric Traumatic Brain Injury

We describe the incidence and etiology of fever and the relationship between fever characteristics and outcome in children with severe traumatic brain injury (TBI). We conducted a retrospective study of children <14 years and with Glasgow Coma Scale (GCS) score of <9 admitted to a level I pediatric trauma center intensive care unit (PICU) between 1998 and 2003. We examined whether fever characteristics were associated with poor outcome (hospital discharge GCS score <13 and discharge disposition of either death or discharge to a skilled nursing facility). PICU length of stay (LOS) and hospital LOS were also examined. Data are presented as means and medians (SD), and P < 0.05 reflects significance. Ninety-three records were reviewed. Patients were 5.7 (SD 4.1) years old, 70% were male, and the average admission GCS score was 5. Mortality rate was 14%. Forty-eight (52%) patients had fever, and 23 (48%) of those patients had infectious fever. Each additional febrile episode was associated with a twofold higher risk of patients having a hospital discharge GCS score of <13 (odds ratio 2.4, 95% confidence interval 1.2-5.0) and having a 0.4-day longer PICU LOS (P < 0.001). Patients with infectious fever had a 0.9-day longer PICU LOS (P < 0.001). Patients with any fever in the PICU had an increased HLOS (0.9 days; P < 0.001). Our data suggest that in severe pediatric TBI, both fever and infection were common, and both were associated with longer LOS. Patients with higher fever burden had poor hospital discharge GCS score.

The Effect of Hypothermia and Hyperthermia on Acute Brain Injury

The brain is extraordinarily susceptible to changes in temperature. Hyperthermia has been shown to exacerbate the biochemical cascade of secondary brain injury. Inversely, hypothermia limits the damaging effects of secondary brain injury. There has been a great deal of investigation regarding the detrimental effects of hyperthermia and the neuroprotection of hypothermia in animal studies. Within the last decade, clinical trials have begun to establish how the brain reacts to both temperature extremes. In the future, studies of hypothermia will continue in the quest of the optimal timing and degree of hypothermia. Hyperthermia will be examined in depth for its detrimental effects on an injured brain. Interventions for the prevention and treatment of hyperthermia will be explored. Nurses will implement cooling strategies to induce hypothermia, applying interventions to prevent complications, and they will also diagnose hyperthermia, deciding when and if to intervene pharmacologically and therapeutically. These advanced nursing actions will be guided by knowledge and understanding of available evidence. This article presents the pathophysiology of secondary brain injury and how it is affected by both hypothermia and hyperthermia. A review of the research leading up to clinical trials is explored, as well as a discussion of the future of temperature modulation for the brain injury patient. This information will help healthcare providers understand the effect that both hypothermia and hyperthermia have on the acutely injured brain.

Managing head injured patients

PURPOSE OF REVIEW

In this article we aim to review the recent literature concerning the management of traumatic brain injury patients, summarize the main findings, and discuss the impact of these findings on clinical practice.

RECENT FINDINGS

Several authors have focused on the development of more reliable and informative tools to predict outcome in traumatic brain injury as well as refining the definition of cerebral ischemia in last year's literature. The validity of the current cerebral perfusion pressure management guidelines has also come under scrutiny. It appears that a one size fits all therapy is not a suitable approach for traumatic brain injury patients. An individualized approach, depending on the integrity of pressure autoregulation mechanisms, would be more advisable. Clinical trials investigating brain protective treatments in head injured patients have been disappointing so far. Increasing the homogeneity of patients entering brain protective studies might be an answer. Finally, the use of hyperoxia as well as factors contributing to secondary brain injury such as the occurrence of hyperthermia, with or without an infectious process, have been assessed in head injury patients.

SUMMARY

The key term for the management of traumatic brain injury patients in the early twenty-first century will clearly be 'individualized therapy'. The search of an ideal cerebral perfusion pressure target that would fit every head-injured patients is a utopia. More energy should be focused on the development of reliable tools for outcome prediction and outcome assessment for traumatic brain injured patients. That, and a better targeting of patients entering brain protective trials, should increase the likelihood of demonstrating a significant salvaging effect of a particular treatment in humans.