Detrimental effects of systemic hyperthermia on locomotor function and histopathological outcome after traumatic spinal cord injury in the rat

Fever in a paraplegia patient with a pressure ulcer

The incidence rates of pressure ulcers (PUs) in patients with SCI in the United States varies by clinical setting, ranging from 0.4%-38% in acute care, 2.2%-23.9% in long-term care, and 0%-17% in home care [1,2]. Unrelieved pressure is the most important factor in the development of PUs. Other factors associated with PUs in patients with SCI include age at the time of injury, men, blacks, completeness of the injury, functional dependence, behavioral protective factors such as frequent pressure relief, self-positioning, daily skin monitoring, nutritional state, cigarette smoking, alcohol (ab)use, and being depressed [3]. Presence of PUs affects functional physical outcomes; thus, prevention of PUs is the key [4]. Infection is a common complication of PUs which can be local such as cellulitis or osteomyelitis or systemic such as septicemia with a greater than 50% mortality. We present a case of a 58-year-old paraplegic man with pressure ulcer who presented with fever in the presence of an osteomyelitis and had a pelvic abscess on magnetic resonance imaging which needed surgical drainage.

An approach to the management of fever of unknown origin in the setting of acute spinal cord injury

Introduction

Discovering the source of a patient’s fever, in the absence of clinical localizing signs, can be a formidable undertaking. Without a clear symptom pattern to narrow the focus of a diagnostic workup, this task can require numerous noninvasive and invasive procedures, imaging studies, and laboratory tests to arrive at a conclusion. Identifying the source of a patient’s fever in the setting of an acute spinal cord injury can present a unique challenge because this population is at risk for many different conditions that can cause fever, some of which are rarely seen in the general population.

Case presentation

This case report describes a unique case and diagnostic workup of fever of unknown origin in a 51-year-old male with multiple medical comorbidities who presented to an inpatient rehabilitation service following an acute traumatic cervical spinal cord injury. Ultimately, it was determined that the patient had several different factors that were causing him to have intermittent fevers over a 5-week period.

Discussion

This case demonstrates the importance of obtaining serial medical histories and physical examinations during the investigation for fever of unknown origin. It also supports why additional workup of a patient’s fever may need to be considered even after a potential source is found. Finally, it demonstrates the need for increased awareness of quadriplegic fever so that this condition can be more effectively recognized, prevented, and managed in the future.

Therapeutic hypothermia and targeted temperature management for traumatic brain injury: Experimental and clinical experience

Traumatic brain injury (TBI) is a worldwide medical problem, and currently, there are few therapeutic interventions that can protect the brain and improve functional outcomes in patients. Over the last several decades, experimental studies have investigated the pathophysiology of TBI and tested various pharmacological treatment interventions targeting specific mechanisms of secondary damage. Although many preclinical treatment studies have been encouraging, there remains a lack of successful translation to the clinic and no therapeutic treatments have shown benefit in phase 3 multicenter trials. Therapeutic hypothermia and targeted temperature management protocols over the last several decades have demonstrated successful reduction of secondary injury mechanisms and, in some selective cases, improved outcomes in specific TBI patient populations. However, the benefits of therapeutic hypothermia have not been demonstrated in multicenter randomized trials to significantly improve neurological outcomes. Although the exact reasons underlying the inability to translate therapeutic hypothermia into a larger clinical population are unknown, this failure may reflect the suboptimal use of this potentially powerful therapeutic in potentially treatable severe trauma patients. It is known that multiple factors including patient recruitment, clinical treatment variables, and cooling methodologies are all important in yielding beneficial effects. High-quality multicenter randomized controlled trials that incorporate these factors are required to maximize the benefits of this experimental therapy. This article therefore summarizes several factors that are important in enhancing the beneficial effects of therapeutic hypothermia in TBI. The current failures of hypothermic TBI clinical trials in terms of clinical protocol design, patient section, and other considerations are discussed and future directions are emphasized.

Neurogenic Fever after Acute Traumatic Spinal Cord Injury: A Qualitative Systematic Review

STUDY DESIGN

Systematic review.

OBJECTIVE

To determine the incidence, pathogenesis, and clinical outcomes related to neurogenic fevers following traumatic spinal cord injury (SCI).

METHODS

A systematic review of the literature was performed on thermodysregulation secondary to acute traumatic SCI in adult patients. A literature search was performed using PubMed (MEDLINE), Cochrane Central Register of Controlled Trials, and Scopus. Using strict inclusion and exclusion criteria, seven relevant articles were obtained.

RESULTS

The incidence of fever of all origins (both known and unknown) after SCI ranged from 22.5 to 71.7% with a mean incidence of 50.6% and a median incidence of 50.0%. The incidence of fever of unknown origin (neurogenic fever) ranged from 2.6 to 27.8% with a mean incidence of 8.0% and a median incidence of 4.7%. Cervical and thoracic spinal injuries were more commonly associated with fever than lumbar injuries. In addition, complete injuries had a higher incidence of fever than incomplete injuries. The pathogenesis of neurogenic fever after acute SCI is not thoroughly understood.

CONCLUSION

Neurogenic fevers are relatively common following an acute SCI; however, there is little in the scientific literature to help physicians prevent or treat this condition. The paucity of research underscored by this review demonstrates the need for further studies with larger sample sizes, focusing on incidence rate, clinical outcomes, and pathogenesis of neurogenic fever following acute traumatic SCI.

Therapeutic hypothermia and targeted temperature management in traumatic brain injury: Clinical challenges for successful translation

The use of therapeutic hypothermia (TH) and targeted temperature management (TTM) for severe traumatic brain injury (TBI) has been tested in a variety of preclinical and clinical situations. Early preclinical studies showed that mild reductions in brain temperature after moderate to severe TBI improved histopathological outcomes and reduced neurological deficits. Investigative studies have also reported that reductions in post-traumatic temperature attenuated multiple secondary injury mechanisms including excitotoxicity, free radical generation, apoptotic cell death, and inflammation. In addition, while elevations in post-traumatic temperature heightened secondary injury mechanisms, the successful implementation of TTM strategies in injured patients to reduce fever burden appear to be beneficial. While TH has been successfully tested in a number of single institutional clinical TBI studies, larger randomized multicenter trials have failed to demonstrate the benefits of therapeutic hypothermia. The use of TH and TTM for treating TBI continues to evolve and a number of factors including patient selection and the timing of the TH appear to be critical in successful trial design. Based on available data, it is apparent that TH and TTM strategies for treating severely injured patients is an important therapeutic consideration that requires more basic and clinical research. Current research involves the evaluation of alternative cooling strategies including pharmacologically-induced hypothermia and the combination of TH or TTM approaches with more selective neuroprotective or reparative treatments. This manuscript summarizes the preclinical and clinical literature emphasizing the importance of brain temperature in modifying secondary injury mechanisms and in improving traumatic outcomes in severely injured patients. This article is part of a Special Issue entitled SI:Brain injury and recovery.

Therapeutic Hypothermia in Spinal Cord Injury: The Status of Its Use and Open Questions

Spinal cord injury (SCI) is a major health problem and is associated with a diversity of neurological symptoms. Pathophysiologically, dysfunction after SCI results from the culmination of tissue damage produced both by the primary insult and a range of secondary injury mechanisms. The application of hypothermia has been demonstrated to be neuroprotective after SCI in both experimental and human studies. The myriad of protective mechanisms of hypothermia include the slowing down of metabolism, decreasing free radical generation, inhibiting excitotoxicity and apoptosis, ameliorating inflammation, preserving the blood spinal cord barrier, inhibiting astrogliosis, promoting angiogenesis, as well as decreasing axonal damage and encouraging neurogenesis. Hypothermia has also been combined with other interventions, such as antioxidants, anesthetics, alkalinization and cell transplantation for additional benefit. Although a large body of work has reported on the effectiveness of hypothermia as a neuroprotective approach after SCI and its application has been translated to the clinic, a number of questions still remain regarding its use, including the identification of hypothermia's therapeutic window, optimal duration and the most appropriate rewarming rate. In addition, it is necessary to investigate the neuroprotective effect of combining therapeutic hypothermia with other treatment strategies for putative synergies, particularly those involving neurorepair.

Emergence of cognitive deficits after mild traumatic brain injury due to hyperthermia

Mild elevations in core temperature can occur in individuals involved in strenuous activities that are risky for potentially sustaining a mild traumatic brain injury (mTBI) or concussion. Recently, we have discovered that mild elevations in brain temperature can significantly aggravate the histopathological consequences of mTBI. However, whether this exacerbation of brain pathology translates into behavioral deficits is unknown. Therefore, we investigated the behavioral consequences of elevating brain temperature to mildly hyperthermic levels prior to mTBI. Adult male Sprague Dawley rats underwent mild fluid-percussion brain injury or sham surgery while normothermic (37 °C) or hyperthermic (39 °C) and were allowed to recover for 7 days. Animals were then assessed for cognition using the water maze and cue and contextual fear conditioning. We found that mTBI alone at normothermia had no effect on long-term cognitive measures whereas mTBI animals that were hyperthermic for 15 min prior to and for 4h after brain injury were significantly impaired on long-term retention for both the water maze and fear conditioning. In contrast, hyperthermic mTBI animals cooled within 15 min to normothermia demonstrated no significant long-term cognitive deficits. Mild TBI irrespective of temperature manipulations resulted in significant short-term working memory deficits. Cortical atrophy and contusions were detected in all mTBI treatment groups and contusion volume was significantly less in hyperthermic mTBI animals that were cooled as compared to hyperthermic mTBI animals that remained hyperthermic. These results indicate that brain temperature is an important variable for mTBI outcome and that mildly elevated temperatures at the time of injury result in persistent cognitive deficits. Importantly, cooling to normothermia after mTBI prevents the development of long-term cognitive deficits caused by hyperthermia. Reducing temperature to normothermic levels soon after mTBI represents a rational approach to potentially mitigate the long-term consequences of mTBI.

Potential long-term benefits of acute hypothermia after spinal cord injury: assessments with somatosensory-evoked potentials

OBJECTIVE

Neuroprotection by hypothermia has been an important research topic over last two decades. In animal models of spinal cord injury, the primary focus has been assessing the effects of hypothermia on behavioral and histologic outcomes. Although a few studies have investigated electrophysiological changes in descending motor pathways with motor-evoked potentials recorded during cooling, we report here hypothermia induced increased electrical conduction in the ascending spinal cord pathways with somatosensory-evoked potentials in injured rats. In our experiments, these effects lasted long after the acute hypothermia and were accompanied by potential long-term improvements in motor movement.

DESIGN

Laboratory investigation.

SETTING

University medical school.

SUBJECTS

Twenty-one female Lewis rats.

INTERVENTIONS

Hypothermia.

MEASUREMENTS AND MAIN RESULTS

All animals underwent spinal cord contusion with the NYU-Impactor by a 12.5-mm weight drop at thoracic vertebra T8. A group (n = 10) was randomly assigned for a systemic 2-hr hypothermia episode (32 ± 0.5°C) initiated approximately 2.0 hrs postinjury. Eleven rats were controls with postinjury temperature maintained at 37 ± 0.5°C for 2 hrs. The two groups underwent preinjury, weekly postinjury (up to 4 wks) somatosensory-evoked potential recordings and standard motor behavioral tests (BBB). Three randomly selected rats from each group were euthanized for histologic analysis at postinjury day 3 and day 28. Compared with controls, the hypothermia group showed significantly higher postinjury somatosensory-evoked potential amplitudes with longer latencies. The BBB scores were also higher immediately after injury and 4 wks later in the hypothermia group. Importantly, specific changes in the Basso, Beattie, Bresnahan scores in the hypothermia group (not seen in controls) indicated regained functions critical for motor control. Histologic evaluations showed more tissue preservation in the hypothermia group.

CONCLUSIONS

After spinal cord injury, early systemic hypothermia provided significant neuroprotection weeks after injury through improved sensory electrophysiological signals in rats. This was accompanied by higher motor behavioral scores and more spared tissue in acute and postacute periods after injury.

Hypothermic treatment for acute spinal cord injury

Spinal cord injury (SCI) is a devastating condition that affects approximately 11,000 patients each year in the United States. Although a significant amount of research has been conducted to clarify the pathophysiology of SCI, there are limited therapeutic interventions that are currently available in the clinic. Moderate hypothermia has been used in a variety of experimental and clinical situations to target several neurological disorders, including traumatic brain and SCI. Recent studies using clinically relevant animal models of SCI have reported the efficacy of therapeutic hypothermia (TH) in terms of promoting long-term behavioral improvement and reducing histopathological damage. In addition, several clinical studies have demonstrated encouraging evidence for the use of TH in patients with a severe cervical spinal cord injury. Moderate hypothermia (33°C) introduced systemically by intravascular cooling strategies appears to be safe and provides some improvement of long-term recovery of function. TH remains an experimental clinical approach and randomized multicenter trials are needed to critically evaluate this potentially exciting therapeutic intervention targeting this patient population.

Traumatic injury activates MAP kinases in astrocytes: mechanisms of hypothermia and hyperthermia

Hyperthermia is common following traumatic brain injury (TBI) and has been associated with poor neurologic outcome, and hypothermia has emerged as a potentially effective therapy for TBI, although its mechanism is still unclear. In this study we investigated the effects of temperature modulations on astrocyte survival following traumatic injury and the involved MAPK pathways. Trauma was produced by scratch injury of a monolayer of confluent astrocytes in culture, followed by incubation at hypothermia (308 degree C), normothermia (378 degree C), or hyperthermia (398 degree C). The activation of MAPK pathways including extracellular signal-regulated protein kinase (ERK), c-Jun NH(2)-terminal kinase ( JNK), and p38 MAPK were measured at 0, 15, 30, 60, and 120 min after traumatic injury followed by temperature modulation. Apoptosis of astrocytes was assessed by quantitation of cleaved caspase-3 expression 24 h after injury. Our findings showed that only JNK activation at 15 min after trauma was reduced by hypothermia, and this was associated with a marked reduction in apoptosis. Hyperthermia activated both ERK and JNK and increased apoptosis. The specific JNK inhibitor, SP60025, markedly reduced JNK-induced apoptosis at normothermia and hyperthermia, and showed a dose-dependent effect. In conclusion, the JNK pathway appears to mediate traumatic injury-induced apoptosis in astrocytes. Prolonged hyperthermia as a secondary insult worsens apoptosis by increasing JNK activation. Hypothermia protects against traumatic injury via early suppression on JNK activation and subsequent prevention of apoptosis. Manipulation of the JNK pathway in astrocytes may represent a therapeutic target for ameliorating the devastating progression of tissue injury and cell death after TBI.

Continuous low dose diclofenac sodium infusion to control fever in neurosurgical critical care

INTRODUCTION

Aim of this randomized prospective clinical trial is to compare two methods of antipyretics and evaluate their efficacy in controlling fever during the acute phase of brain damage.

METHODS

Twenty-two febrile comatose patients: 12 severe traumatic brain injury and 10 subarachnoid hemorrhage divided in 2 groups: Diclofenac low-dose infusion (10 patients) and extemporaneous boluses of NSAIDs (CTRL, 12 patients). The primary outcome measure was length of time with temperature>38 degrees C. Secondary outcome measures were: 1) to assess the effects of each antipyretic strategy on intracranial pressure (ICP), cerebral perfusion pressure (CPP), mean arterial pressure (MAP) and heart rate; 2) to monitor adverse effects of each antipyretic strategy. The baseline characteristics in the two treatment groups were similar.

RESULTS

Primary findings: percentage of time per patient with temperature>38 degrees C was significantly lower (P<0.0001) in the DCF group, 4% (0-22%), vs. 34% (8-56%) in CTRL group. In addition, mean T degrees , max T degrees were lower in DCF than in CTRL (P<0.05). Secondary findings: CPP and MAP were significantly higher in DCF group (P<0.05) while ICP was not different (NS). However, if ICP pre randomization was <25 mmHg, CTRL suffered a worst ICP (24+/-11 vs. 16+/-7 P=0.01), MAP (89+/-10 vs. 104+/-10 P=0.01) and CPP (75+/-10 vs. 94+/-17 P=0.01) compared to DCF. No differences between the two treatment were recorded when ICP>or=25 mmHg before randomization. There was no gastrointestinal or intracranial bleeding.

CONCLUSIONS

Low dose DCF infusion is a potential useful strategy for a successful control temperature better than intermittent NSAIDs dosing, minimizing potentially brain-damaging effects of fever.

Progenitor cell injury after irradiation to the developing brain can be modulated by mild hypothermia or hyperthermia

Ionizing radiation induced acute cell death in the dentate gyrus subgranular zone (SGZ) and the subventricular zone (SVZ). Hypomyelination was also observed. The effects of mild hypothermia and hyperthermia for 4 h after irradiation (IR) were studied in postnatal day 9 rats. One hemisphere was irradiated with a single dose of 8 Gy and animals were randomized to normothermia (rectal temperature 36 degrees C for 4 h), hypothermia (32 degrees C for 4 h) or hyperthermia (39 degrees C for 4 h). Cellular injury, e.g. chromatin condensation and nitrotyrosine formation, appeared to proceed faster when the body temperature was higher. Caspase-3 activation was more pronounced in the hyperthermia group and nuclear translocation of p53 was less pronounced in the hypothermia group 6 h after IR. In the SVZ the loss of nestin-positive progenitors was more pronounced (48%) and the size was smaller (45%) in the hyperthermia group 7 days post-IR. Myelination was not different after hypo- or hyperthermia. This is the first report to demonstrate that hypothermia may be beneficial and that hyperthermia may aggravate the adverse side-effects after radiation therapy to the developing brain.

Macrophages and dendritic cells treatment of spinal cord injury: from the bench to the clinic

The failure of the spinal cord to recover after injury has been associated with the immune privilege mechanism that suppresses immune activity throughout the central nervous system. Primed macrophages and dendritic cells were shown to promote neurological recovery in preclinical models of spinal cord injury. A cell therapy consisting of autologous incubated macrophages is now being tested on spinal cord injury patients in clinical trials.

Monitoring recovery after injury: procedures for deriving the optimal test window

Researchers studying the impact of treatments designed to facilitate recovery after neural injury face competing demands. On the one hand, because treatment effects often emerge slowly over days, and because researchers seek evidence of stable long-term effects, it is common practice to observe experimental subjects for many weeks after treatment. On the other hand, the cost of performing studies and the need to evaluate a multitude of alternative treatment procedures requires optimal efficiency, pushing researchers towards shorter test procedures. With these issues in mind, researchers have appeared to derive a test window based on previously published methodologies and inspection of their recovery curves, with testing terminated after the recovery curve reaches asymptote (approaches a slope of 0). An alternative procedure is introduced here that evaluates the stability of the data set over time. Using correlational techniques, researchers can determine whether (1) testing should be continued for additional days; or (2) equivalent statistical power can be achieved in fewer days. This provides a rational decision rule to help researchers balance competing demands. Applying these techniques to a procedure that evaluates the impact of acute treatments on recovery from spinal cord injury, it is shown that equal statistical power can be achieved in half the time, greatly increasing the efficiency with which alternative treatments can be evaluated.

Targeting the host inflammatory response in traumatic spinal cord injury

Both acute and chronic inflammatory processes have been shown to influence outcome in experimental models of spinal cord injury. Although early inflammatory responses may participate in secondary injury processes, more delayed inflammatory events may be reparative. Therapeutic strategies that target these events are currently based on experimental findings that have clarified the cellular and molecular processes involved in the inflammatory response to injury. An increasing body of literature supports the hypothesis that acute inflammatory events are attenuated by therapeutic hypothermia and other anti-inflammatory strategies, whereas immune neuroprotection and axonal regeneration can be achieved by transfer of activated T cells or by treatment with therapeutic vaccines. These data are summarized in the present review.

Compensatory locomotor adjustments of rats with cervical or thoracic spinal cord hemisections

The accurate measurement of behavioral compensation after CNS trauma, such as spinal cord injury, is important when assessing the functional effects of injury and treatment in animal models. We investigated the locomotor abilities of rats with unilateral thoracic or cervical spinal cord injuries using a locomotor rating (BBB) scale, reflex tests, and quantitative kinetic measurements. The BBB rating scale indicated that thoracic spinal hemisected (TH) rats had more severely affected hindlimbs compared to cervical spinal hemisected (CH) and sham-operated animals. Kinetic measurements revealed that CH and TH animals moved with different ground reaction force patterns, which nevertheless shared some similarities with each other and with the gait patterns of rats with different unilateral CNS lesions. Uninjured rats typically had an equal distribution of their body weight over the forelimbs and hind limbs, and used their forelimbs predominantly for braking while using their hind limbs mostly for propulsion. CH rats bore more weight on their hind limbs than their forelimbs, while TH animals bore more weight on their forelimbs than their hind limbs. Neither CH nor TH rats used the forelimb ipsilateral to the spinal hemisection for net braking or propulsion. The hindlimb contralateral to the hemisection was placed on the ground prematurely during the stride cycle for both CH and TH animals. The altered kinetics of the locomotor pattern in hemisected animals resulted in changes in the oscillations of total body potential and kinetic energies. These two forms of energy oscillate synchronously in intact locomoting rats, but were asynchronous during parts of the stride cycle in spinal hemisected animals. We conclude that rats develop a general compensatory response for unilateral CNS lesions, which may help stabilize the animal during locomotion.