Cerebral blood flow and oxygen metabolism during mild hypothermia in patients with subarachnoid haemorrhage

Midbrain injury in patients with subarachnoid hemorrhage: a diffusion tensor imaging study

We investigated the characteristics of midbrain injuries in patients with spontaneous subarachnoid hemorrhage (SAH) by using diffusion tensor imaging (DTI). Twenty-seven patients with SAH and 25 healthy control subjects were recruited for this study. Fractional anisotropy (FA) and mean diffusivity (MD) data were obtained for four regions of the midbrain (the anterior ventral midbrain, posterior ventral midbrain, tegmentum area, and tectum) in 27 hemispheres that did not show any pathology other than SAH. The mean FA and MD values of the four regions of the midbrain (anterior ventral midbrain, posterior ventral midbrain, tegmentum, and tectum) of the patient group were significantly lower and higher than those of the control group, respectively (p < 0.05). The mean FA values of the patient group were significantly different among the anterior ventral midbrain, posterior ventral midbrain, tegmentum, and tectum regions (ANOVA; F = 3.22, p < 0.05). Post hoc testing showed that the mean FA value of the anterior ventral midbrain was significantly lower than those of the posterior ventral midbrain, tegmentum, and tectum (p < 0.05); in contrast, there were no differences in mean FA values of the posterior ventral midbrain, tegmentum, and tectum (p > 0.05). However, differences were not observed among four regions of the midbrain (anterior ventral midbrain, posterior ventral midbrain, tegmentum, and tectum) in the mean MD values. We detected evidence of neural injury in all four regions of the midbrain of patients with SAH, and the anterior ventral midbrain was the most severely injured among four regions of the midbrain. Our results suggest that a pathophysiological mechanism of these neural injuries might be related to the occurrence of a subarachnoid hematoma.

Perinatal Infection: A Major Contributor to Efficacy of Cooling in Newborns Following Birth Asphyxia

Neonatal encephalopathy (NE) is a global burden, as more than 90% of NE occurs in low- and middle-income countries (LMICs). Perinatal infection seems to limit the neuroprotective efficacy of therapeutic hypothermia. Efforts made to use therapeutic hypothermia in LMICs treating NE has led to increased neonatal mortality rates. The heat shock and cold shock protein responses are essential for survival against a wide range of stressors during which organisms raise their core body temperature and temporarily subject themselves to thermal and cold stress in the face of infection. The characteristic increase and decrease in core body temperature activates and utilizes elements of the heat shock and cold shock response pathways to modify cytokine and chemokine gene expression, cellular signaling, and immune cell mobilization to sites of inflammation, infection, and injury. Hypothermia stimulates microglia to secret cold-inducible RNA-binding protein (CIRP), which triggers NF-κB, controlling multiple inflammatory pathways, including nod-like receptor family pyrin domain containing 3 (NLRP3) inflammasomes and cyclooxygenase-2 (COX-2) signaling. Brain responses through changes in heat shock protein and cold shock protein transcription and gene-expression following fever range and hyperthermia may be new promising potential therapeutic targets.

Diffusion Tensor Imaging Studies on Spontaneous Subarachnoid Hemorrhage-Related Brain Injury: A Mini-Review

Accurate diagnosis of the presence and severity of neural injury in patients with subarachnoid hemorrhage (SAH) is important in neurorehabilitation because it is essential for establishing appropriate therapeutic strategies and developing a prognosis. Diffusion tensor imaging has a unique advantage in the identification of microstructural white matter abnormalities which are not usually detectable on conventional brain magnetic resonance imaging. In this mini-review article, 12 diffusion tensor imaging studies on SAH-related brain injury were reviewed. These studies have demonstrated SAH-related brain injuries in various neural tracts or structures including the cingulum, fornix, hippocampus, dorsolateral prefrontal region, corticospinal tract, mamillothalamic tract, corticoreticular pathway, ascending reticular activating system, Papez circuit, optic radiation, and subcortical white matter. We believe that these reviewed studies provide information that would be helpful in science-based neurorehabilitation of patients with SAH. Furthermore, the results of these reviewed studies would also be useful for clarification of the pathophysiological mechanisms associated with SAH-related brain injury. However, considering the large number of neural tracts or neural structures in the brain, more research on SAH-related brain injury in other neural tracts or structures should be encouraged.

Therapeutic hypothermia protocols

The application of targeted temperature management has become common practice in the neurocritical care setting. It is important to recognize the pathophysiologic mechanisms by which temperature control impacts acute neurologic injury, as well as the clinical limitations to its application. Nonetheless, when utilizing temperature modulation, an organized approach is required in order to avoid complications and minimize side-effects. The most common clinically relevant complications are related to the impact of cooling on hemodynamics and electrolytes. In both instances, the rate of complications is often related to the depth and rate of cooling or rewarming. Shivering is the most common side-effect of hypothermia and is best managed by adequate monitoring and stepwise administration of medications specifically targeting the shivering response. Due to the impact cooling can have upon pharmacokinetics of commonly used sedatives and analgesics, there can be significant delays in the return of the neurologic examination. As a result, early prognostication posthypothermia should be avoided.

Endovascular Cooling Catheter for Selective Brain Hypothermia: An Animal Feasibility Study of Cooling Performance

BACKGROUND AND PURPOSE

Therapeutic hypothermia represents a promising neuroprotective treatment in acute ischemic stroke. Selective cerebral hypothermia applied early, prior to and during endovascular mechanical recanalization therapy, may be beneficial in the critical phase of reperfusion. We aimed to assess the feasibility of a new intracarotid cooling catheter in an animal model.

MATERIALS AND METHODS

Nine adult sheep were included. Temperature probes were introduced into the frontal and temporal brain cortices bilaterally. The cooling catheter system was introduced into a common carotid artery. Selective blood cooling was applied for 180 minutes. Systemic and local brain temperatures were measured during cooling and rewarming. Common carotid artery diameters and flow were measured angiographically and by Doppler sonography.

RESULTS

The common carotid artery diameter was between 6.7 and 7.3 mm. Common carotid artery blood flow velocities increased moderately during cooling and after catheter removal. Maximum cerebral cooling in the ipsilateral temporal cortex was -4.7°C (95% CI, -5.1 to -4.0°C). Ipsilateral brain temperatures dropped significantly faster and became lower compared with the contralateral cortex with maximum temperature difference of -1.3°C (95% CI, -1.5 to -1.0°C; P < .0001) and compared with systemic temperature (-1.4°C; 95% CI, -1.7 to -1.0°C; P < .0001).

CONCLUSIONS

Sheep proved a feasible animal model for the intracarotid cooling catheter. Fast induction of selective mild hypothermia was achieved within the cooled cerebral hemisphere, with stable temperature gradients in the contralateral brain and systemic blood. Further studies are required to demonstrate any therapeutic benefit of selective cerebral cooling in a stroke model.

Therapeutic hypothermia reduces middle cerebral artery flow velocity in patients with severe aneurysmal subarachnoid hemorrhage

BACKGROUND

Transcranial Doppler (TCD) is widely used to detect and follow up cerebral vasospasm after subarachnoid hemorrhage (SAH). Therapeutic hypothermia might influence blood flow velocities assessed by TCD. The aim of the study was to evaluate the effect of hypothermia on Doppler blood flow velocity after SAH.

METHODS

In 20 patients treated with hypothermia (33°) due to refractory intracranial hypertension or delayed cerebral ischemia (DCI), mean flow velocity of the middle cerebral artery (MFV(MCA)) was assessed by TCD. Thirteen patients were treated with combined hypothermia and barbiturate coma and seven with hypothermia alone. MFV(MCA) was obtained within 24 h before and after induction of hypothermia as well as before and after rewarming.

RESULTS

Hypothermia was induced on average 5 days after SAH (range 1-12) and maintained for 144 h (range 29-270). After hypothermia induction, MFV(MCA) decreased from 113.7 ± 49.0 to 93.8 ± 44.7 cm/s (p = 0.001). The decrease was independent of SAH-related complications and barbiturate coma. MFV(MCA) further decreased by 28.2 cm/s between early and late hypothermia (p < 0.001). This second decrease was observed in patients with DCI (p < 0.001), but not in patients with intracranial hypertension (p = 0.715). Compared to late hypothermia, MFV(MCA) remained unchanged after rewarming (65.6 ± 32.1 vs 70.3 ± 36.8 cm/s; p = 0.219). However, patients treated with hypothermia alone showed an increase in MFV(MCA) after rewarming (p = 0.016).

CONCLUSION

Therapeutic hypothermia after SAH decreases Doppler blood flow velocity in both intracranial hypertension and DCI cases. The results can be the effect of hypothermia-related mechanisms or resolving cerebral vasospasm during prolonged hypothermia.

Hypothermia as a neuroprotective strategy in subarachnoid hemorrhage: a pathophysiological review focusing on the acute phase

Aneurysmal subarachnoid hemorrhage (SAH) remains a very prevalent challenge in neurosurgery associated with a high morbidity and mortality due to the lack of specific treatment modalities. The prognosis of SAH patients depends primarily on three factors: (i) the severity of the initial bleed, (ii) the endovascular or neurosurgical procedure to occlude the aneurysm and (iii) the occurrence of late sequelae, namely delayed ischemic neurological deficits due to cerebral vasospasm. While neurosurgeons and interventionalists have put significant efforts in minimizing periprocedural complications and a multitude of investigators have been devoted to the research on chronic vasospasm, the acute phase of SAH has not been studied in comparable detail. In various experimental studies during the past decade, hypothermia has been shown to reduce neuronal damage after ischemia, traumatic brain injury and other cerebrovascular diseases. Clinically, only some of these encouraging results could be reproduced. This review analyses results of studies on the effects of hypothermia on SAH with special respect to the acute phase in an experimental setting. Based on the available data, some considerations for the application of mild to moderate hypothermia in patients with subarachnoid hemorrhage are given.

Fundamental research progress of mild hypothermia in cerebral protection

Through the years, the clinical application of mild hypothermia has been carried out worldwide and is built from the exploration and cognition of neuroprotection mechanisms by hypothermia. However, within the last decade, extensive and fundamental researches in this area have been conducted. In addition to aspects of the previous findings, scholars have discovered several new contents and uncertain results. This article reviews and summarizes this decade’s progression of mild hypothermia in lowering the cerebral oxygen metabolism, protecting the blood–brain-barrier, regulating the inflammatory response, regulating the excessive release of neurotransmitters, inhibiting calcium overload, and reducing neuronal apoptosis. In many aspects, particularly in regulating inflammatory reverse reaction, various results have been reported and therefore guide scholars to conduct more detailed analysis and investigation in order to discover the inherent theories surrounding the effect of mild hypothermia, and for better clinical services.

Use of hypothermia in the intensive care unit

Used for over 3600 years, hypothermia, or targeted temperature management (TTM), remains an ill defined medical therapy. Currently, the strongest evidence for TTM in adults are for out-of-hospital ventricular tachycardia/ventricular fibrillation cardiac arrest, intracerebral pressure control, and normothermia in the neurocritical care population. Even in these disease processes, a number of questions exist. Data on disease specific therapeutic markers, therapeutic depth and duration, and prognostication are limited. Despite ample experimental data, clinical evidence for stroke, refractory status epilepticus, hepatic encephalopathy, and intensive care unit is only at the safety and proof-of-concept stage. This review explores the deleterious nature of fever, the theoretical role of TTM in the critically ill, and summarizes the clinical evidence for TTM in adults.

The importance of early brain injury after subarachnoid hemorrhage

Aneurysmal subarachnoid hemorrhage (aSAH) is a medical emergency that accounts for 5% of all stroke cases. Individuals affected are typically in the prime of their lives (mean age 50 years). Approximately 12% of patients die before receiving medical attention, 33% within 48 h and 50% within 30 days of aSAH. Of the survivors 50% suffer from permanent disability with an estimated lifetime cost more than double that of an ischemic stroke. Traditionally, spasm that develops in large cerebral arteries 3-7 days after aneurysm rupture is considered the most important determinant of brain injury and outcome after aSAH. However, recent studies show that prevention of delayed vasospasm does not improve outcome in aSAH patients. This finding has finally brought in focus the influence of early brain injury on outcome of aSAH. A substantial amount of evidence indicates that brain injury begins at the aneurysm rupture, evolves with time and plays an important role in patients' outcome. In this manuscript we review early brain injury after aSAH. Due to the early nature, most of the information on this injury comes from animals and few only from autopsy of patients who died within days after aSAH. Consequently, we began with a review of animal models of early brain injury, next we review the mechanisms of brain injury according to the sequence of their temporal appearance and finally we discuss the failure of clinical translation of therapies successful in animal models of aSAH.

Physiologic and pharmacologic considerations for hypothermia therapy in neonates

With mounting evidence that hypothermia is neuroprotective in newborns with hypoxic-ischemic encephalopathy (HIE), an increasing number of centers are offering this therapy. Hypothermia is associated with a wide range of physiologic changes affecting every organ system, and awareness of these effects is essential for optimum patient management. Lowering the core temperature also alters pharmacokinetic and pharmacodynamic properties of medications commonly used in asphyxiated neonates, necessitating close attention to drug efficacy and side effects. Rewarming introduces additional risks and challenges as the hypothermia-associated physiologic and pharmacologic changes are reversed. In this review we provide an organ system-based assessment of physiologic changes associated with hypothermia. We also summarize evidence from randomized controlled trials showing lack of serious adverse effects of moderate hypothermia therapy in term and near-term newborns with moderate-to-severe HIE. Finally, we review the effects of hypothermia on drug metabolism and clearance based on studies in animal models and human adults, and limited data from neonates.

Pharmacologic options for reducing the shivering response to therapeutic hypothermia

Recent literature has demonstrated significant improvements in neurologic outcomes in patients who have received induced hypothermia in the setting of out-of-hospital cardiac arrest. Through multiple metabolic mechanisms, the induction of hypothermia slows the progression and devastation of transient cerebral hypoxia. Despite these benefits, the desired reduction in core temperature is often a challenging venture as the body attempts to maintain homeostasis through the induction of thermoregulatory processes aimed at elevating body temperature. Shivering is an involuntary muscular activity that enhances heat production in an attempt to restore homeostasis. For successful induction and maintenance of induced hypothermia, shivering, as well as other thermoregulatory responses, must be overcome. Several pharmacologic options are available, either used alone or in combination, that safely and effectively prevent or treat shivering after the induction of hypothermia. We conducted a PubMed search (1966-March 2009) to identify all human investigations published in English that discussed pharmacologic mechanisms for the control of shivering. Among these options, clonidine, dexmedetomidine, and meperidine have demonstrated the greatest and most clinically relevant impact on depression of the shivering threshold. More research in this area is needed, however, and the role of the clinical pharmacist in the development and implementation of this therapy needs to be defined.

Therapeutic hypothermia: implications for acute care practitioners

The use of therapeutic hypothermia (TH) in acute care medicine has evolved over the past 2 centuries, and its use over the past decade has increased in emergency departments, intensive care units, and operating rooms. Therapeutic hypothermia has several potential clinical applications based on its putative mechanisms of action. It appears to improve oxygen supply to ischemic areas of the brain and decreases intracranial pressure. Mild-to-moderate TH (33 degrees C +/- 1 degrees C) after resuscitation from cardiac arrest is neuroprotective, and also acts on the cardiovascular system with evidence of a decrease in heart rate and increase in systemic vascular resistance. Therapeutic hypothermia decreases cardiac output by 7% for each 1 degrees C decrease in core body temperature, but maintains the stroke volume and the mean arterial pressure. Despite a growing amount of data, this life-saving technique is underutilized in hospitals worldwide. The purpose of this comprehensive review is to show the evolution and the clinical use of TH as it pertains to acute care practitioners.

[Therapeutic hypothermia in neurocritical patients]

Induced hypothermia in neurocritical patients is one of the most promising neuroprotective therapies in the last decade. Unfortunately, the promising results obtained in experimental studies have had an unequal reflection in the different diseases that affect the neurocritical patient. The use of therapeutic hypothermia is clearly established in patients with neurological deterioration after cardiac arrest. On the contrary, its use in patients with traumatic brain injury is highly controversial. There is not enough evidence in stroke and hemorrhagic patients to support its use except in clinical trials. Nowadays, the greater understanding of the pathophysiology of secondary brain damage, the go od clinical results obtained in randomized clinical trials in patients with cerebral anoxia after ventricular fibrillation and the new cooling methods that have appeared have improved the interest of hypothermia in neurocritical patients. Induced hypothermia has a role in the intensive care unit. Critical care physicians should be familiar with the physiologic effects, current indications, techniques, and complications of induced hypothermia. This review elaborates on the clinical implications of hypothermia research in traumatic brain injury, anoxic, brain injury, stroke and intracerebral hemorrhage.

THERAPEUTIC HYPOTHERMIA IN PATIENTS WITH ANEURYSMAL SUBARACHNOID HEMORRHAGE, REFRACTORY INTRACRANIAL HYPERTENSION, OR CEREBRAL VASOSPASM

OBJECTIVE

To evaluate the feasibility and safety of mild hypothermia treatment in patients with aneurysmal subarachnoid hemorrhage (SAH) who are experiencing intracranial hypertension and/or cerebral vasospasm (CVS).

METHODS

Of 441 consecutive patients with SAH, 100 developed elevated intracranial pressure and/or symptomatic CVS refractory to conventional treatment. Hypothermia (33–34°C) was induced and maintained until intracranial pressure normalized, CVS resolved, or severe side effects occurred.

RESULTS

Thirteen patients were treated with hypothermia alone, and 87 were treated with hypothermia in combination with barbiturate coma. Sixty-six patients experienced poor-grade SAH (Hunt and Hess Grades IV and V) and 92 had Fisher Grade 3 and 4 bleedings. The mean duration of hypothermia was 169 ± 104 hours, with a maximum of 16.4 days. The outcome after 1 year was evaluated in 90 of 100 patients. Thirty-two patients (35.6%) survived with good functional outcome (Glasgow Outcome Scale [GOS] score, 4 and 5), 14 (15.5%) were severely disabled (GOS score, 3), 1 (1.1%) was in a vegetative state (GOS score, 2), and 43 (47.8%) died (GOS score, 1). The most frequent side effects were electrolyte disorders (77%), pneumonia (52%), thrombocytopenia (47%), and septic shock syndrome (40%). Of 93 patients with severe side effects, 6 (6.5%) died as a result of respiratory or multi-organ failure.

CONCLUSION

Prolonged systemic hypothermia may be considered as a last-resort option for a carefully selected group of SAH patients with intracranial hypertension or CVS resistant to conventional treatment. However, complications associated with hypothermia require elaborate protocols in general intensive care unit management.

Temperature management in acute neurologic disorders

Temperature management in acute neurologic disorders has received considerable attention in the last 2 decades. Numerous trials of hypothermia have been performed in patients with head injury, stroke, and cardiac arrest. This article reviews the physiology of thermoregulation and mechanisms responsible for hyperpyrexia. Detrimental effects of fever and benefits of normalizing elevated temperature in experimental models are discussed. This article presents a detailed analysis of trials of induced hypothermia in patients with acute neurologic insults and describes methods of fever control.

Therapeutic hypothermia: past, present, and future

Cardiac arrest causes devastating neurologic morbidity and mortality. The preservation of the brain function is the final goal of resuscitation. Therapeutic hypothermia (TH) has been considered as an effective method for reducing ischemic injury of the brain. The therapeutic use of hypothermia has been utilized for millennia, and over the last 50 years has been routinely employed in the operating room. TH gained recognition in the past 6 years as a neuroprotective agent in victims of cardiac arrest after two large, randomized, prospective clinical trials demonstrated its benefits in the postresuscitation setting. Extensive research has been done at the cellular and molecular levels and in animal models. There are a number of proposed applications of TH, including traumatic brain injury, acute encephalitis, stroke, neonatal hypoxemia, and near-drowning, among others. Several devices are being designed with the purpose of decreasing temperature at a fast and steady rate, and trying to avoid potential complications. This article reviews the historical development of TH, and its current indications, methods of induction, and potential future.

A theoretical model of selective cooling using intracarotid cold saline infusion in the human brain

A three-dimensional mathematical model was developed to examine the transient and steady-state temperature distribution in the human brain during selective brain cooling (SBC) by unilateral intracarotid freezing-cold saline infusion. To determine the combined effect of hemodilution and hypothermia from the cold saline infusion, data from studies investigating the effect of these two parameters on cerebral blood flow (CBF) were pooled, and an analytic expression describing the combined effect of the two factors was derived. The Pennes bioheat equation used the thermal properties of the different cranial layers and the effect of cold saline infusion on CBF to propagate the evolution of brain temperature. A healthy brain and a brain with stroke (ischemic core and penumbra) were modeled. CBF and metabolic rate data were reduced to simulate the core and penumbra. Simulations using different saline flow rates were performed. The results suggested that a flow rate of 30 ml/min is sufficient to induce moderate hypothermia within 10 min in the ipsilateral hemisphere. The brain with stroke cooled to lower temperatures than the healthy brain, mainly because the stroke limited the total intracarotid blood flow. Gray matter cooled twice as fast as white matter. The continuously falling hematocrit was the main time-limiting factor, restricting the SBC to a maximum of 3 h. The study demonstrated that SBC by intracarotid saline infusion is feasible in humans and may be the fastest method of hypothermia induction.

Temperature Management in Acute Neurologic Disorders

Temperature management in acute neurologic disorders has received considerable attention in the last 2 decades. Numerous trials of hypothermia have been performed in patients with head injury, stroke, and cardiac arrest. This article reviews the physiology of thermoregulation and mechanisms responsible for hyperpyrexia. Detrimental effects of fever and benefits of normalizing elevated temperature in experimental models are discussed. This article presents a detailed analysis of trails of induced hypothermia in patients with acute neurologic insults and describes methods of fever control.

Therapeutic hypothermia

Therapeutic hypothermia has been used for millennia, but in recent years was not in much clinical use due to an apparent high risk of complications. More recently, the benefits of induced therapeutic hypothermia have been rediscovered, mainly with the improvement in neurological outcome in out-of-hospital cardiac arrest victims. In addition, therapeutic hypothermia has been suggested to improve outcome in other neurological conditions such as traumatic brain injury, neonatal asphyxia, cerebrovascular accidents and intracranial hypertension. This article reviews the history of the discovery of therapeutic hypothermia, as well as the current therapeutic applications and ways to deliver this treatment. Cooling techniques and recovery processes, as well as potential complications are also reviewed. Clinicians caring for a wide variety of critically ill patients should be familiar with the use of therapeutic hypothermia.

Controversies in the management of aneurysmal subarachnoid hemorrhage*

BACKGROUND

The care of patients with aneurysmal subarachnoid hemorrhage has evolved significantly with the advent of new diagnostic and therapeutic modalities. Although it is believed that these advances have contributed to improved outcomes, considerable uncertainty persists regarding key areas of management.

OBJECTIVE

To review selected controversies in the management of aneurysmal subarachnoid hemorrhage, with a special emphasis on endovascular vs. surgical techniques for securing aneurysms, the diagnosis and therapy of cerebral vasospasm, neuroprotection, antithrombotic and anticonvulsant agents, cerebral salt wasting, and myocardial dysfunction, and to suggest venues for further clinical investigation.

DATA SOURCE

Search of MEDLINE and Cochrane databases and manual review of article bibliographies.

DATA SYNTHESIS AND CONCLUSIONS

Many aspects of care in patients with aneurysmal subarachnoid hemorrhage remain highly controversial and warrant further resolution with hypothesis-driven clinical or translational research. It is anticipated that the rigorous evaluation and implementation of such data will provide a basis for improvements in short- and long-term outcomes.

Hypothermia and stroke: the pathophysiological background

Hypothermia to mitigate ischemic brain tissue damage has a history of about six decades. Both in clinical and experimental studies of hypothermia, two principal arbitrary patterns of core temperature lowering have been defined: mild (32-35 degrees C) and moderate hypothermia (30-33 degrees C). The neuroprotective effectiveness of postischemic hypothermia is typically viewed with skepticism because of conflicting experimental data. The questions to be resolved include the: (i) postischemic delay; (ii) depth; and (iii) duration of hypothermia. However, more recent experimental data have revealed that a protected reduction in brain temperature can provide sustained behavioral and histological neuroprotection, especially when thermoregulatory responses are suppressed by sedation or anesthesia. Conversely, brief or very mild hypothermia may only delay neuronal damage. Accordingly, protracted hypothermia of 32-34 degrees C may be beneficial following acute cerebral ischemia. But the pathophysiological mechanism of this protection remains yet unclear. Although reduction of metabolism could explain protection by deep hypothermia, it does not explain the robust protection connected with mild hypothermia. A thorough understanding of the experimental data of postischemic hypothermia would lead to a more selective and effective clinical therapy. For this reason, we here summarize recent experimental data on the application of hypothermia in cerebral ischemia, discuss problems to be solved in the experimental field, and try to draw parallels to therapeutic potentials and limitations.

Long-term hypothermia in patients with severe brain edema after poor-grade subarachnoid hemorrhage: feasibility and intensive care complications

The purpose was to evaluate the feasibility and intensive care complications of long-term hypothermia (>72 hours) in the treatment of severe brain edema after poor-grade subarachnoid hemorrhage (SAH) Hunt and Hess grade 4 to 5. Among 156 patients with SAH, 21 patients were treated with mild hypothermia (33.0 to 34.0 degrees C) combined with barbiturate coma because of severe brain edema and elevated intracranial pressure (>15 mm Hg) after early aneurysm clipping. Hypothermia was sustained for at least 24 hours after maintaining an intracranial pressure of <15 mm Hg. Nine patients were treated for <72 hours (group 1: mean 42.2 hours, range 8-66 hours) and 12 for >72 hours (group 2: mean 153.9 hours, range 78-400 hours). Three patients (14%) died during the hypothermia treatment. Good functional outcome after 3 months (Glasgow Outcome Score 4-5) was achieved in 10 patients (48%). The outcome did not differ between the two groups. All patients developed severe infections. In group 2 the mean value of minimal leukocyte counts during hypothermia was significantly lower (6.9 vs. 11.8 x 109/L; P = 0.001), and thrombocytopenia (<150 x 109/L) occurred significantly more often (48 vs. 33%; P = 0.032). In 48% of patients with poor-grade SAH, good functional outcome was achieved with combined mild hypothermia and barbiturate coma after early aneurysm surgery. This may be a feasible treatment even for longer than 72 hours. All patients developed severe infections as potentially hazardous side effects. To determine whether mild hypothermia alone is effective in the treatment of severe SAH patients, controlled studies to compare the effects of barbiturate coma alone, mild hypothermia alone, and combined barbiturate coma with hypothermia are needed.

Induced hypothermia in critical care medicine: a review

BACKGROUND

Clinical trials of induced hypothermia have suggested that this treatment may be beneficial in selected patients with neurologic injury.

OBJECTIVES

To review the topic of induced hypothermia as a treatment of patients with neurologic and other disorders.

DESIGN

Review article.

INTERVENTIONS

None.

MAIN RESULTS

Improved outcome was demonstrated in two prospective, randomized, controlled trials in which induced hypothermia (33 degrees C for 12-24 hrs) was used in patients with anoxic brain injury following resuscitation from prehospital cardiac arrest. In addition, prospective, randomized, controlled trials have been conducted in patients with severe head injury, with variable results. There also have been preliminary clinical studies of induced hypothermia in patients with severe stroke, newborn hypoxic-ischemic encephalopathy, neurologic infection, and hepatic encephalopathy, with promising results. Finally, animal models have suggested that hypothermia that is induced rapidly following traumatic cardiac arrest provides significant neurologic protection and improved survival.

CONCLUSIONS

Induced hypothermia has a role in selected patients in the intensive care unit. Critical care physicians should be familiar with the physiologic effects, current indications, techniques, and complications of induced hyperthermia.

Role of hypothermia in the management of severe cases of subarachnoid hemorrhage

Mild hypothermia is thought to have a brain protective effect to pathophysiological conditions, which are caused by severe brain damage including brain injury and cerebral stroke. In this paper, general aspects of this treatment as history, pathophysiological effect, and problems are summarized. Also, the clinical effects of hypothermic therapy for a subarachnoid hemorrhage are reviewed. Main targets of the therapy for this disease are severe primary brain damage caused by the attack itself and secondary ischemic brain damage after delayed vasospasm. But even now, there are no fully established data about the effect of hypothermia at such conditions after subarachnoid hemorrhage. The results of our study of cerebral blood flow and cerebral oxygen metabolism using positron emission tomography are presented to show the physiological effect of hypothermia on human brain after severe brain damage caused by subarachnoid hemorrhage. In conclusion, effect of hypothermia on subarachnoid hemorrhage is not confirmed yet and reported data is limited, so that additional studies, especially controlled studies, would be recommended.