Clinical trial of an air-circulating cooling blanket for fever control in critically ill neurologic patients

Intensive care unit management of interventional neuroradiology patients

The management of interventional neurologic patients in the intensive care unit is based on their underlying disease for the most part. Patients with ischemic stroke are largely managed like patients with ischemic stroke who have not undergone interventional procedures, and the same is true for those with an aneurysmal subarachnoid hemorrhage or intracerebral hemorrhage secondary to an arteriovenous malformation, for example.Having said this, there are some special considerations that require special mention when it comes to managing patients after catheter-based procedures.

The management of large hemispheric cerebral infarcts

Large hemispheric cerebral infarcts have significant morbidity and mortality. Our understanding of this pathophysiological process involved with secondary neurological deterioration in large hemispheric infarctions has increased in the past few decades. New experimental strategies designed to improve outcome are reviewed.

[Controlled mild-to-moderate hypothermia in the intensive care unit]

Controlled hypothermia is used as a therapeutic intervention to provide neuroprotection and (more recently) cardioprotection. The growing insight into the underlying pathophysiology of apoptosis and destructive processes at the cellular level, and the mechanisms underlying the protective effects of hypothermia, have led to improved application and to a widening of the range of potential indications. In many centres hypothermia has now become part of the standard therapy for post-anoxic coma in certain patients, but for other indications its use still remains controversial. The negative findings of some studies may be partly explained by inadequate protocols for the application of hypothermia and insufficient attention to the prevention of potential side effects. This review deals with some of the concepts underlying hypothermia-associated neuroprotection and cardioprotection, and discusses some potential clinical indications as well as reasons why some clinical trials may have produced conflicting results. Practical aspects such as methods to induce hypothermia, as well as the side effects of cooling are also discussed.

Emerging medical and surgical management strategies in the evaluation and treatment of intracerebral hemorrhage

Intracerebral hemorrhage (ICH) accounts for approximately 10% of all strokes and causes high morbidity and mortality. Rupture of the small perforating vessels of the cerebral arteries is caused by chronic hypertension, which induces pathologic changes in the small vessels and accounts for most cases of ICH; however, amyloid angiopathy and other secondary causes are being seen more frequently with the increasing age of the population. Recent computed tomographic studies have revealed that ICH is a dynamic process with up to one third of initial hemorrhages expanding within the first several hours of ictus. Secondary injury is believed to result from the development of cerebral edema and the release of specific neurotoxins associated with the breakdown products of hemoglobin. Treatment is primarily supportive. Surgical evacuation is the treatment of choice for patients with neurologic deterioration from infratentorial hematomas. Randomized trials comparing surgical evacuation to medical management have shown no benefit of surgical removal of supratentorial hemorrhages. New strategies focusing on early hemostasis, improved critical care management, and less invasive surgical techniques for clot evacuation are promising to decrease secondary neurologic injury. We review the pathophysiology of ICH, its medical management, and new treatment strategies for improving patient outcome.

Clinical trial of a novel surface cooling system for fever control in neurocritical care patients

OBJECTIVE

To compare the efficacy of a novel water-circulating surface cooling system with conventional measures for treating fever in neuro-intensive care unit patients.

DESIGN

Prospective, unblinded, randomized controlled trial.

SETTING

Neurologic intensive care unit in an urban teaching hospital.

PATIENTS

Forty-seven patients, the majority of whom were mechanically ventilated and sedated, with fever > or =38.3 degrees C for >2 consecutive hours after receiving 650 mg of acetaminophen.

INTERVENTIONS

Subjects were randomly assigned to 24 hrs of treatment with a conventional water-circulating cooling blanket placed over the patient (Cincinnati SubZero, Cincinnati OH) or the Arctic Sun Temperature Management System (Medivance, Louisville CO), which employs hydrogel-coated water-circulating energy transfer pads applied directly to the trunk and thighs.

MEASUREMENTS AND MAIN RESULTS

Diagnoses included subarachnoid hemorrhage (60%), cerebral infarction (23%), intracerebral hemorrhage (11%), and traumatic brain injury (4%). The groups were matched in terms of baseline variables, although mean temperature was slightly higher at baseline in the Arctic Sun group (38.8 vs. 38.3 degrees C, p = .046). Compared with patients treated with the SubZero blanket (n = 24), Arctic Sun-treated patients (n = 23) experienced a 75% reduction in fever burden (median 4.1 vs. 16.1 C degrees -hrs, p = .001). Arctic Sun-treated patients also spent less percent time febrile (T > or =38.3 degrees C, 8% vs. 42%, p < .001), spent more percent time normothermic (T < or =37.2 degrees C, 59% vs. 3%, p < .001), and attained normothermia faster than the SubZero group median (2.4 vs. 8.9 hrs, p = .008). Shivering occurred more frequently in the Arctic Sun group (39% vs. 8%, p = .013).

CONCLUSION

The Arctic Sun Temperature Management System is superior to conventional cooling-blanket therapy for controlling fever in critically ill neurologic patients.

Causes and consequences of fever complicating critical surgical illness

BACKGROUND

Fever may have malign consequences in the postoperative period. This study was performed to determine the causes and consequences of fever in critically ill surgical patients. The specific hypothesis tested is that postoperative fever is associated with adverse clinical outcomes, including increased organ dysfunction and risk of death.

METHODS

Inception-cohort study of critically ill surgical patients who manifested a core temperature of >/=38.2 degrees C for the first time. The episode of fever was monitored until resolution, which was defined as a core temperature of <38.2 degrees C for at least 72 consecutive h. Demographic data collected included age, gender, admission diagnosis, admission status (elective/emergency), severity of illness (APACHE III), the systemic inflammatory response syndrome (SIRS) score, the cumulative multiple organ dysfunction score, cause of fever (infectious/non-infectious), ICU and hospital length of stay, and mortality. The day of onset of fever in the ICU, peak temperature, ICU day of peak temperature, and duration of fever episode were recorded. All diagnostic and therapeutic interventions were recorded, including the type and duration of antibiotic therapy. Univariate results of possible significance (alpha < 0.15) were tested in logistic regression models for independence of effect upon mortality after auto-correlation was excluded by matrix correlations and the Durbin-Watson statistic. Cases where both non-infectious and infectious causes of fever were present were analyzed as part of the infectious group, whereas the cumulative MOD score was dichotomized (< 5, >/=5 points) at a value known to be associated with increased mortality.

RESULTS

Among 2,419 screened patients, 626 patients (26%) developed fever. Febrile patients were older, sicker, more likely to have undergone emergency surgery, more likely to develop organ dysfunction, and more likely to die (all, p < 0.0001). The mean day of onset of fever was day 1 and the mean peak temperature for the episode was 39.1 +/- 0.1 degrees C. For most patients, it was their only episode of fever, with a mean of 1.4 +/- 0.1 episodes/patient. Forty-six percent of febrile patients were found to have an infectious cause of fever. Nearly all patients had SIRS, and nearly all developed organ dysfunction to some degree. By logistic regression, the presence of SIRS (as opposed to fever in isolation), emergency status, higher APACHE III score and the peak temperature were associated with increased mortality, with peak temperature being the most powerful predictor in the model (OR 2.20, 95% Cl 1.57-3.19). Gender had no bearing on outcome, and there was a trend toward a protective effect from an infectious etiology of fever.

CONCLUSIONS

Postoperative fever is deleterious to critically ill patients. The magnitude of fever is a determinant of mortality, whereas an infectious etiology of fever may not be. The impacts of nosocomial infection and suppression of fever on critically surgical patients deserve further study.

Elevated body temperature independently contributes to increased length of stay in neurologic intensive care unit patients

OBJECTIVE

Elevated temperature results in worse outcome in experimental models of cerebral ischemia and brain trauma. In critically ill neurologic and neurosurgical patients, elevated body temperature is common and is associated with neurologic deterioration and poor outcome. We sought to determine whether, after controlling for age, severity of illness, and complications, elevated body temperature remained an important predictor of intensive care unit (ICU) and hospital length of stay, mortality rate, and hospital disposition in a large cohort of patients emergently admitted to a neurologic ICU.

DESIGN

Prospectively collected data (demographics, diagnosis, Acute Physiology and Chronic Health Evaluation II score, Glasgow Coma Scale score, daily maximum temperature, complications, disposition) were retrospectively reviewed.

SETTING

A 20-bed neurology/neurosurgery ICU in a tertiary care academic, level I trauma, referral center.

SUBJECTS

From 6,759 admissions, those admitted after an elective procedure with length of stay < or = 1 day, those <18 yrs old, and those with incomplete data were excluded, leaving 4,295 patients for this analysis. First, a hierarchical multiple regression analysis was performed to determine whether elevated body temperature was an independent predictor of length of stay. Second, a path analysis was performed to define the relationships among elevated body temperature, complications, and length of stay. Finally, a matched, weighted sample was developed to quantify the difference in length of stay.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

We measured ICU and hospital length of stay, mortality rate, and discharge disposition. The presence of elevated body temperature was associated with a dose-dependent longer ICU and hospital length of stay, higher mortality rate, and worse hospital disposition. The most important predictor of ICU length of stay was the number of complications (beta =.681) followed by elevated body temperature (beta =.143). In the matched, weighted population, the presence of elevated body temperature was associated with 3.2 additional ICU days and 4.3 additional hospital days.

CONCLUSION

In a large cohort of neurologic ICU patients, after we controlled for severity of illness, diagnosis, age, and complications, elevated body temperature was independently associated with a longer ICU and hospital length of stay, higher mortality rate, and worse outcome.

Treatment of fever in the neurologic intensive care unit with a catheter-based heat exchange system

CONTEXT

Elevated temperature worsens injury in experimental focal and global ischemia and brain trauma. Fever is common in patients with acute neurologic illness and independently predicts poor outcome. Conventional means of treating fever are not very effective in this population.

OBJECTIVE

To study the effectiveness of a catheter-based heat exchange system in reducing elevated temperatures in critically ill neurologic and neurosurgical patients. DESIGN, INTERVENTION, SETTING, AND POPULATION: This was a prospective randomized, non-blinded trial that compared conventional treatment of fever (acetaminophen and cooling blankets) with conventional treatment plus an intravascular catheter-based heat exchange system (Alsius, Irvine, CA). Patients admitted to one of 13 neurologic intensive care units in academic medical centers were eligible if they a) suffered subarachnoid hemorrhage, intracerebral hemorrhage, ischemic infarction, or traumatic brain injury; b) had a temperature >38 degrees C on two occasions or for >4 continuous hrs; and c) required central venous access.

MAIN OUTCOME MEASURE

The fever burden (area under the curve >38 degrees C) for 72 hrs was compared in an intention to treat analysis. Safety of the catheter system was monitored.

RESULTS

A total of 296 patients were enrolled over 20 months. Forty-one percent had subarachnoid hemorrhage, 24% had traumatic brain injury, 23% had intracerebral hemorrhage, and 13% had ischemic stroke. The groups were matched in terms of age, body mass index, sex, and Glasgow Coma Scale score distribution. Fever burden was 7.92 vs. 2.87 degrees C-hrs in the conventional group and catheter groups, respectively (64% reduction, p <.01). There was no higher rate of infection or the use of sedatives, narcotics, or antibiotics in the catheter group. The catheter did not significantly increase risk to the patient beyond that of a central catheter.

CONCLUSIONS

The addition of this catheter-based cooling system to conventional management significantly improves fever reduction in neurologic intensive care unit patients.

Application of therapeutic hypothermia in the ICU: opportunities and pitfalls of a promising treatment modality. Part 1: Indications and evidence

OBJECTIVE

Hypothermia has been used for medicinal purposes since ancient times. This paper reviews the current potential clinical applications for mild hypothermia (32-35 degrees C).

DESIGN AND SETTING

Induced hypothermia is used mostly to prevent or attenuate neurological injury, and has been used to provide neuroprotection in traumatic brain injury, cardiopulmonary resuscitation, stroke, and various other disorders. The evidence for each of these applications is discussed, and the mechanisms underlying potential neuroprotective effects are reviewed. Some of this evidence comes from animal models, and a brief overview of these models and their limitations is included in this review.

RESULTS

The duration of cooling and speed of re-warming appear to be key factors in determining whether hypothermia will be effective in preventing or mitigating neurological injury. Some other potential usages of hypothermia, such as its use in the peri-operative setting and its application to mitigate cardiac injury following ischemia and reperfusion, are also discussed.

CONCLUSIONS

Although induced hypothermia appears to be a highly promising treatment, it should be emphasized that it is associated with a number of potentially serious side effects, which may negate some or all of its potential benefits. Prevention and/or early treatment of these complications are the key to successful use of hypothermia in clinical practice. These side effects, as well as various physiological changes induced by cooling, are discussed in a separate review.

Application of therapeutic hypothermia in the intensive care unit. Opportunities and pitfalls of a promising treatment modality--Part 2: Practical aspects and side effects

Induced hypothermia can be used to protect the brain from post-ischemic and traumatic neurological injury. Potential clinical applications and the available evidence are discussed in a separate paper. This review focuses on the practical aspects of cooling and physiological changes induced by hypothermia, as well as the potential side effects that may develop. These side effects can be serious and, if not properly dealt with, may negate some or all of hypothermia's potential benefits. However, many of these side effects can be prevented or modified by high-quality intensive care treatment, which should include careful monitoring of fluid balance, tight control of metabolic aspects such as glucose and electrolyte levels, prevention of infectious complications and various other interventions. The speed and duration of cooling and rate of re-warming are key factors in determining whether hypothermia will be effective; however, the risk of side effects also increases with longer duration. Realizing hypothermia's full therapeutic potential will therefore require meticulous attention to the prevention and/or early treatment of side effects, as well as a basic knowledge and understanding of the underlying physiological and pathophysiological mechanisms. These and other, related issues are dealt with in this review.

Therapeutic hypothermia

Hypothermia is common during anaesthesia and surgery owing to anaesthetic-induced inhibition of thermoregulatory control. Perioperative hypothermia is associated with numerous complications. However, for certain patient populations, and under specific clinical conditions, hypothermia can provide substantial benefits. Lowering core temperature to 32-34 degrees C may reduce cell injury by suppressing excitotoxins and oxygen radicals, stabilizing cell membranes, and reducing the number of abnormal electrical depolarizations. Evidence from animal studies indicates that even mild hypothermia provides substantial protection against cerebral ischaemia and myocardial infarction. Mild hypothermia has been shown to improve outcome after cardiac arrest in humans. Randomized trials are in progress to evaluate the potential benefits of mild hypothermia during aneurysm clipping and after stroke or acute myocardial infraction. However, as hypothermia can cause unwanted side-effects, further research is needed to better quantify the risks and benefits of therapeutic hypothermia.

Treatment of Refractory Fever in the Neurosciences Critical Care Unit Using a Novel, Water-Circulating Cooling Device

Fever after acute brain injury affects neuronal function and recovery. Standard therapies have proven to be inadequate in treating hyperthermia in this patient population. We report on safety/efficacy pilot data collected using a noninvasive, novel, water-circulating cooling device in febrile acute brain injury patients. We enrolled patients who developed fever (rectal temperature > or =38.0 degrees C) refractory to pharmacological therapy. The treatment device uses an ice water circulating system embedded in hydrogel-coated, energy transfer pads. Its thermoregulatory feedback control uses cold water (4.0 degrees C-42.0 degrees C) and was set at 36.5 degrees C for this study. We analyzed the temperature response during 600 consecutive minutes of treatment. Six consecutive patients were enrolled and seven episodes of fever were recorded; the mean age of the patients was 59.7 years (range 46-71 years; five male, one female). Diagnoses were as follows: subarachnoid hemorrhage (two), severe traumatic brain injury (two), status epilepticus following massive cerebral infarction (one), and intracerebral/intraventricular hemorrhage (one). Hand warming was applied at treatment onset on all patients; shivering only responsive to meperidine occurred in five of them. Fever of 38.4 degrees C (range 38.0 degrees C-38.9 degrees C) was reduced to 36.9 degrees C (range 36.0 degrees C-38.0 degrees C) after 120 minutes (P<0.001). Core temperature remained "locked" during the remainder of the treatment (36.6 degrees C, P=0.5; 36.6 degrees C, P=0.9; and 36.5 degrees C, P=0.9 at 180, 300, and 600 minutes, respectively). Skin integrity under the pads was preserved in all study subjects. Our results indicate that use of this novel technique is safe, rapidly effective, and able to maintain sustained normothermia following fever in a cohort of critically ill neurologic/neurosurgical patients.

The 5 Ps of acute ischemic stroke treatment: parenchyma, pipes, perfusion, penumbra, and prevention of complications

Stroke is a treatable disease. Despite the therapeutic nihilism of the past, the advent of thrombolysis has changed the way stroke is approached. Acute ischemic stroke is a challenging and heterogeneous disease. Treatment needs to be based on an understanding of the underlying pathophysiology of ischemia. Interventions are designed to improve neuronal salvage and outcome. The underlying tenets of stroke therapy focus on the brain parenchyma, arterial flow (pipes), perfusion, the ischemic milieu or penumbra, and prevention of complications. This article focuses on the practical issues of ischemic stroke care, with a brief review of supporting literature.

Programmable microchip monitoring of post-stroke pyrexia: effects of aspirin and paracetamol on temperature and infarct size in the rat

BACKGROUND

Recent studies have demonstrated spontaneous and prolonged hyperthermia following stroke in both humans and rodents. However, a full characterization of these pyretic changes and the effects of anti-pyretic drugs on outcome is not available.

METHODS

The aims of this study were to monitor conscious body temperature (n=10 per group) using programmable microchips for up to 24 h in rats following either permanent (p) or 90 min transient (t) middle cerebral artery occlusion (MCAO) or sham surgery, and to evaluate the relationship to hypothalamic damage. Also, the effects of anti-pyretic drug therapy on body temperature and infarct volume were evaluated in animals treated with vehicle, optimal doses of either aspirin or paracetamol (250 mg/kg i.p.) following pMCAO (n=10 per group).

RESULTS

At 1 h, body temperature significantly (P<0.01) increased to 38.6+/-0.2 degrees C following tMCAO and 38.9+/-0.1 degrees C following pMCAO compared with sham-operated animals (37.1+/-0.1 degrees C). Sustained hyperthermia (> or =38.1 degrees C) was observed for up to 24 h following pMCAO but approached baseline within 30 min (37.6+/-0.2 degrees C) following tMCAO with reperfusion. The post-stroke pyrexia was related to the degree of ischemia where hypothalamic damage was observed in (80%) of the animals undergoing pMCAO and (0%) in the tMCAO group (P<0.05). Treatment with paracetamol (250 mg/kg i.p.) significantly attenuated (P<0.05) but did not normalize core body temperature up to 2 h (38.2+/-0.4 degrees C) compared with vehicle treated animals (39.3+/-0.1 degrees C). Aspirin had no effect on temperature under these conditions. Hypothalamic damage and lesion volume were not different between animals treated with paracetamol (253.3+/-8.5 mm(3)), aspirin (264.0+/-11.6 mm(3)) or vehicle (274.4+/-8.2 mm(3)).

CONCLUSIONS

This study is the first to demonstrate the utility of programmable microchips to monitor serial changes in post-stroke hyperthermia. The sustained post-stroke pyrexia and negative effects of antipyretic treatment may be attributed to the extensive hypothalamic injury suggesting that better pharmacologic approaches to reduce body temperature should be identified and evaluated for brain protection in severe experimental stroke.