Clinical review: Treatment of heat stroke: should dantrolene be considered?

Association of malignant hyperthermia and exertional heat illness in young athletes: An analysis of awareness among clinical and athletic first responders

Background

Malignant hyperthermia (MH), a rare inherited condition seen almost exclusively in the perioperative setting, is triggered by volatile anesthetics or an intravenous paralytic drug, succinylcholine. It can, however, occur without any exposure to anesthetic drugs, being associated with heat illness and rhabdomyolysis, thus presenting a little-known risk to young athletes exercising in hot environments.

Objective

This study aimed to determine the first responder awareness of MH and its association with heat illness in young athletes within athletic and clinical environments.

Methods

Awareness within the clinical milieu was assessed by an institutional chart review of 3296 charts. The identified heat illness cases were examined for treatment consistent with the management of a suspected episode of MH. Awareness among first responders in an athletic setting was examined by a survey administered to a total of 1,500 coaches and athletic trainers at the high school level along with emergency medical services providers across the United States.

Results

No treatment consistent with the suspicion of MH was noted among clinical first responders, suggesting a lack of awareness. Survey administration also revealed a limited amount of knowledge of MH and its potential role in heat illness.

Conclusion

The results point to lack of awareness among pre-hospital and hospital-based first responders of the relationship between MH and heat illness in young athletes. An effort to educate these members of the healthcare community can contribute to an expeditious and life-saving intervention.

Clinical Relevance

First responders who may interact with a young athlete have low knowledge of MH and its relationship to heat illness. Similar lack of awareness exists among hospital personnel who care for young individuals with heat illness. Educating the first responders about this condition can speed up the time to intervene and save lives.

Management of Heat-Related Illness and Injury in the ICU: A Concise Definitive Review

OBJECTIVES

The increasing frequency of extreme heat events has led to a growing number of heat-related injuries and illnesses in ICUs. The objective of this review was to summarize and critically appraise evidence for the management of heat-related illnesses and injuries for critical care multiprofessionals.

DATA SOURCES

Ovid Medline, Embase, Cochrane Clinical Trials Register, Cumulative Index to Nursing and Allied Health Literature, and ClinicalTrials.gov databases were searched from inception through August 2023 for studies reporting on heat-related injury and illness in the setting of the ICU.

STUDY SELECTION

English-language systematic reviews, narrative reviews, meta-analyses, randomized clinical trials, and observational studies were prioritized for review. Bibliographies from retrieved articles were scanned for articles that may have been missed.

DATA EXTRACTION

Data regarding study methodology, patient population, management strategy, and clinical outcomes were qualitatively assessed.

DATA SYNTHESIS

Several risk factors and prognostic indicators for patients diagnosed with heat-related illness and injury have been identified and reported in the literature. Effective management of these patients has included various cooling methods and fluid replenishment. Drug therapy is not effective. Multiple organ dysfunction, neurologic injury, and disseminated intravascular coagulation are common complications of heat stroke and must be managed accordingly. Burn injury from contact with hot surfaces or pavement can occur, requiring careful evaluation and possible excision and grafting in severe cases.

CONCLUSIONS

The prevalence of heat-related illness and injury is increasing, and rapid initiation of appropriate therapies is necessary to optimize outcomes. Additional research is needed to identify effective methods and strategies to achieve rapid cooling, the role of immunomodulators and anticoagulant medications, the use of biomarkers to identify organ failure, and the role of artificial intelligence and precision medicine.

Current clinical application of dantrolene sodium

Dantrolene sodium (DS) was first introduced as an oral antispasmodic drug. However, in 1975, DS was demonstrated to be effective for managing malignant hyperthermia (MH) and was adopted as the primary therapeutic drug after intravenous administration. However, it is difficult to administer DS intravenously to manage MH. MH is life-threatening, pharmacogenomically related, and induced by depolarizing neuromuscular blocking agents or inhalational anesthetics. All anesthesiologists should know the pharmacology of DS. DS suppresses Ca2+ release from ryanodine receptors (RyRs). RyRs are expressed in various tissues, although their distribution differs among subtypes. The anatomical and physiological functions of RyRs have also been demonstrated as effective therapeutic drugs for cardiac arrhythmias, Alzheimer's disease, and other RyR-related diseases. Recently, a new formulation was introduced that enhanced the hydrophilicity of the lipophilic DS. The authors summarize the pharmacological properties of DS and comment on its indications, contraindications, adverse effects, and interactions with other drugs by reviewing reference articles.

Critical illness aspects of heatstroke: A hot topic

Heatstroke represents the most severe end of the heat illness spectrum, and is increasingly seen in those undergoing exercise or exertion ('exertional heatstroke') and those exposed to high ambient temperatures, for example in heatwaves ('classical heatstroke'). Both forms may be associated with significant thermal injury, leading to organ dysfunction and the need for admission to an intensive care unit. The process may be exacerbated by translocation of bacteria or endotoxin through an intestinal wall rendered more permeable by the hyperthermia. This narrative review highlights the importance of early diagnosis, rapid cooling and effective management of complications. It discusses the incidence, clinical features and treatment of heatstroke, and discusses the possible role of intestinal permeability and advances in follow-up and recovery of this condition. Optimum treatment involves an integrated input from prehospital, emergency department and critical care teams, along with follow-up by rehabilitation teams and, if appropriate, sports or clinical physiologists.

Dantrolene and ryanodine receptors in COVID-19: The daunting task and neglected warden

Dantrolene (DTN) is a ryanodine receptor (RyR) antagonist that inhibits Ca²⁺ release from stores in the sarcoplasmic reticulum. DTN is mainly used in the management of malignant hyperthermia. RyRs are highly expressed in immune cells and are involved in different viral infections, including severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2), because Ca²⁺ is necessary for viral replication, maturation and release. DTN can inhibit the proliferation of SARS-CoV-2, indicating its potential role in reducing entry and pathogenesis of SARS-CoV-2. DTN may increase clearance of SARS-CoV-2 and promote coronavirus disease 2019 (COVID-19) recovery by shortening the period of infection. DTN inhibits N-methyl-D-aspartate (NMDA) mediated platelets aggregations and thrombosis. Therefore, DTN may inhibit thrombosis and coagulopathy in COVID-19 through suppression of platelet NMDA receptors. Moreover, DTN has a neuroprotective effect against SARS-CoV-2 infection-induced brain injury through modulation of NMDA receptors, which are involved in excitotoxicity, neuronal injury and the development of neuropsychiatric disorders. In conclusion, DTN by inhibiting RyRs may attenuate inflammatory disorders in SARS-CoV-2 infection and associated cardio-pulmonary complications. Therefore, DNT could be a promising drug therapy against COVID-19. Preclinical and clinical studies are warranted in this regards.

Intravenous dantrolene in hypermetabolic syndromes: a survey of the U.S. Veterans Health Administration database

BACKGROUND

Intravenous dantrolene is often prescribed for hypermetabolic syndromes other than the approved indication of malignant hyperthermia (MH). To clarify the extent of and indications for dantrolene use in conditions other than MH, we sought to document current practices in the frequency, diagnoses, clinical characteristics and outcomes associated with dantrolene treatment in critical care settings.

METHODS

Inpatients receiving intravenous dantrolene from October 1, 2004 to September 30, 2014 were identified retrospectively in the U.S. Veterans Health Administration national database. Extracted data included; diagnoses of hypermetabolic syndromes; triggering drugs; dantrolene dosages; demographics; vital signs; laboratory values; in-hospital mortality; complications; and lengths of stay. Frequency and mortality of patients who did not receive dantrolene were obtained in selected diagnoses for exploratory comparisons.

RESULTS

Dantrolene was administered to 304 inpatients. The most frequent diagnoses associated with dantrolene treatment were neuroleptic malignant syndrome (NMS; N = 108, 35.53%) and sepsis (N = 47, 15.46%), with MH accounting for only 13 (4.28%) cases. Over half the patients had psychiatric comorbidities and received psychotropic drugs before dantrolene treatment. Common clinical findings in patients receiving dantrolene included elevated temperature (mean ± SD; 38.7 ± 1.3 °C), pulse (116.33 ± 22.80/bpm), respirations (27.75 ± 9.58/min), creatine kinase levels (2,859.37 ± 6,646.88 IU/L) and low pO₂ (74.93 ± 40.16 mmHg). Respiratory, renal or cardiac failure were common complications. Mortality rates in-hospital were 24.01% overall, 7.69% in MH, 20.37% in NMS and 42.55% in sepsis, compared with mortality rates in larger and possibly less severe groups of unmatched patients with MH (5.26%), NMS (6.66%), or sepsis (41.91%) who did not receive dantrolene.

CONCLUSIONS

In over 95% of cases, dantrolene administration was associated with diagnoses other than MH in critically-ill patients with hypermetabolic symptoms and medical and psychiatric comorbidities. Exploratory survey data suggested that the efficacy and safety of dantrolene in preventing mortality in hypermetabolic syndromes other than MH remain uncertain. However, randomized and controlled studies using standardized criteria between groups matched for severity are essential to guide practice in using dantrolene.

Dantrolene Administration in the Management of the Prehospital Patient with Methylenedioxymethamphetamine Overdose: A Case Series and Literature Review

Methylenedioxymethamphetamine (MDMA) is a psychoactive substance that is used commonly as a recreational drug at rave music festivals. MDMA intoxication can cause a myriad of symptoms and side effects including the manifestation of hyperpyrexia in patients. Hyperpyrexia can mimic a heat stroke and ultimately lead to various forms of end-organ damage. The most common methods used in treating MDMA-induced hyperpyrexia focus on the rapid reduction of core body temperature. Various off-label medications have also been used in combating MDMA-induced hyperpyrexia. Dantrolene is one such medication, although its role in the treatment of MDMA intoxication remains uncertain. This case series preliminarily examines the efficacy of dantrolene in mitigating MDMA-induced hyperpyrexia and potentially reducing the risk of end-organ damage in patients suffering from MDMA overdose. This study focuses on nine patients who presented after ingesting various forms of MDMA at “rave” music events. All patients were found to be hyperthermic in the field with a maximum core body temperature of 109 degrees Fahrenheit. All patients were immediately managed by cooling measures, and seven patients additionally received dantrolene in the field before being transferred to Arrowhead Regional Medical Center. Upon arrival to the hospital, nearly every patient was found to have significantly decreased body temperatures when compared to previously measured body temperatures out in the field. However, nearly all patients in the study were also noted to have laboratory abnormalities consistent with various forms of end-organ damage. The degree and severity of end-organ damage observed in MDMA-induced hyperpyrexia seem to be a function of initial core body temperature. Higher core body temperature tends to correlate with more forms of end-organ damage and a higher severity of end-organ damage. Intervention with dantrolene and cooling measures appeared to have no effect on reducing the risk of developing end-organ damage in this patient population.

[Therapeutic effects of novel type1 ryanodine receptor inhibitor on skeletal muscle diseases]

Type 1 ryanodine receptor (RyR1) plays a key role in Ca²⁺ release from the sarcoplasmic reticulum (SR) during excitation-contraction coupling of skeletal muscle. Mutations in RyR1 hyperactivate the channel to cause malignant hyperthermia (MH). MH is a serious complication characterized by skeletal muscle rigidity and elevated body temperature in response to commonly used inhalational anesthetics. Thus far, more than 300 mutations in RyR1 gene have been reported in patients with MH. Some heat stroke triggered by exercise or environmental heat stress is also related to MH mutations in the RyR1 gene. The only drug approved for ameliorating the symptoms of MH is dantrolene, which has been first developed in 1960s as a muscle relaxant. However, dantrolene has several disadvantages for clinical use: poor water solubility which makes rapid preparation difficult in emergency situations and long plasma half-life, which causes long-lasting side effects such as muscle weakness. Here we show that a novel RyR1-selective inhibitor, 6,7-(methylenedioxy)-1-octyl-4-quinolone-3-carboxylic acid (Compound 1, Cpd1), effectively rescues MH and heat stroke in new mouse model relevant to MH. Cpd1 has great advantages of higher water solubility and shorter plasma half-life compared to dantrolene. Our data suggest that Cpd1 has the potential to be a promising new candidate for effective treatment of patients carrying RyR1 mutations.

A novel RyR1-selective inhibitor prevents and rescues sudden death in mouse models of malignant hyperthermia and heat stroke

Mutations in the type 1 ryanodine receptor (RyR1), a Ca²⁺ release channel in skeletal muscle, hyperactivate the channel to cause malignant hyperthermia (MH) and are implicated in severe heat stroke. Dantrolene, the only approved drug for MH, has the disadvantages of having very poor water solubility and long plasma half-life. We show here that an oxolinic acid-derivative RyR1-selective inhibitor, 6,7-(methylenedioxy)-1-octyl-4-quinolone-3-carboxylic acid (Compound 1, Cpd1), effectively prevents and treats MH and heat stroke in several mouse models relevant to MH. Cpd1 reduces resting intracellular Ca²⁺, inhibits halothane- and isoflurane-induced Ca²⁺ release, suppresses caffeine-induced contracture in skeletal muscle, reduces sarcolemmal cation influx, and prevents or reverses the fulminant MH crisis induced by isoflurane anesthesia and rescues animals from heat stroke caused by environmental heat stress. Notably, Cpd1 has great advantages of better water solubility and rapid clearance in vivo over dantrolene. Cpd1 has the potential to be a promising candidate for effective treatment of patients carrying RyR1 mutations.

Mutations in ryanodine receptor 1 (RyR1), a Ca2+ release channel in skeletal muscle, cause malignant hyperthermia (MH) and are involved in heat stroke. Here, the authors show that an oxolinic acid-derivative RyR1 inhibitor effectively prevents and treats MH and heat stroke in various MH mouse models.

Beneficial effects of dantrolene in the treatment of rhabdomyolysis as a potential late complication associated with COVID-19: a case report

Background

Patients with severe COVID-19 have disorders of the respiratory, cardiovascular, coagulation, skeletal muscle, and central nervous systems. These systemic failures may be associated with cytokine release syndrome, characterized by hyperpyrexia, thrombocytopenia, hyperferritinemia, and the elevation of other inflammatory markers. Rhabdomyolysis with high fever is a complication that is rarely found in COVID-19. The exact relations of these clinical conditions in patients with COVID-19 remain unknown.

Case presentation

We present the case of a 36-year-old man with severe COVID-19 complicated by rhabdomyolysis and high fever. After admission, his condition continued to deteriorate, with a high body temperature. On day 9, the patient had elevated creatine kinase and myoglobin levels consistent with rhabdomyolysis (26,046 U/L and 3668 ng/mL, respectively). In addition to viral therapy, he was immediately treated with hydration. However, the patient had persistent fever and elevated creatine kinase levels. The patient was diagnosed with malignant hyperthermia as a late complication of COVID-19, although he had no hereditary predisposition to malignant hyperthermia or neuroleptic malignant syndrome. The administration of dantrolene with muscle relaxation and anti-inflammatory function showed potential efficacy for rhabdomyolysis, high fever, and increased plasma inflammatory markers.

Conclusions

Malignant hyperthermia is triggered by not only anesthetic agents but also viral infections. A possible mechanism of malignant hyperthermia is hypersensitivity of calcium release from the sarcoplasmic reticulum. These include mutations in or the activation of the skeletal muscle ryanodine receptor calcium release channel. Dantrolene is a ryanodine receptor antagonist and is used as an anti-inflammatory agent. The administration of dantrolene showed potential efficacy for rhabdomyolysis, high body temperature due to inflammation, and increased inflammatory markers. The underlying mechanism of the association of rhabdomyolysis and high fever in COVID-19 might be similar to the pathogenesis of malignant hyperthermia.

Pharmacological evidence for the involvement of ryanodine receptors in halothane-induced liver injury in mice

Drug-induced liver injury (DILI) is a major safety concern in drug development. Halothane (HAL), an inhaled anesthetic, induces severe and idiosyncratic liver injury. Ryanodine receptors (RyR) are major intracellular calcium release channels found on the plasma membrane of the endoplasmic reticulum (ER). It has been reported that disordered hepatic calcium homeostasis is a feature of HAL-induced liver injury (HILI) in guinea pigs. However, there are no reports on whether RyR could mediate the pathogenesis of HILI. The aim of the present study was to investigate the effect of RyR on HILI. Ryanodine (RYA, RyR agonist, 50 μg/kg, i.p.) was administered to BALB/c female mice 1 h before HAL administration (15 mmol/kg, i.p.), which significantly elevated plasma transaminase levels and induced severe hepatic inflammation and necrosis. In contrast, dantrolene sodium (DAN, RyR antagonist) treatment significantly suppressed HILI in a dose- and time-dependent manner and alleviated liver damage. The number of infiltrated neutrophils in the liver were higher in the group treated with HAL + RYA than in the group treated with HAL alone, while DAN treatment decreased neutrophil infiltration in HILI. The hepatic mRNA levels of proinflammatory cytokines; chemokines; and factors related to danger signals, neutrophils, oxidative and ER stress, pro-apoptosis, and RyR were significantly increased with RYA pretreatment, whereas these levels were decreased with DAN treatment. These results suggest that RYA exacerbates HILI, and DAN exerts a protective effect against HILI. Hence, our study provides a novel insight regarding the effect of RyR in the mechanism underlying HILI.

Heat related illnesses. Review of an ongoing challenge

Climate change is the most challenging natural calamity of chronic nature that presents intense episodes of heat waves, and events. Effects of heat waves and increasing average temperature on heat-related illnesses (HRIs) demand a review of existing preventive and treatment strategies to direct future research. Heat-related illnesses are presented as minor to severe life-threatening conditions. Despite the understanding of the pathophysiology of HRI, pharmacological interventions are limited. Prevention is the best strategy against HRI. There is a dearth of epidemiological studies that reviewed the effect of pharmacological interventions on mortality, and there remains a need to identify critical key components other than inflammatory modulators, which can be targeted to decrease HRI.

Consideration of Occult Infection and Sepsis Mimics in the Sick Patient Without an Apparent Infectious Source

BACKGROUND

Evaluation and treatment of the acutely ill patient is typically complicated by multiple comorbidities and incomplete medical histories. This is exemplified by patients with sepsis, whose care is complicated by variable presentations, shifting definitions, and a variety of potential sources. Many practitioners fail to consider and recognize less-common sources of infection in a timely manner. Additionally, multiple noninfectious conditions can present with the fever and tachycardia typical of the septic patient. The errors of anchoring and premature closure may lead to delay in, or failure of, diagnosis of these conditions.

OBJECTIVE

This review addresses the evaluation of the acutely ill-appearing patient without an apparent source, focusing on occult sources of infection and conditions that mimic sepsis.

DISCUSSION

Musculoskeletal, cardiac, neuraxial, and abdominal sources of sepsis should be considered in the acutely ill patient. Indwelling devices should be carefully examined for signs of infection. Consideration for sepsis mimics, such as neuroleptic malignant syndrome, malignant hyperthermia, medication toxicity, and thyroid storm, in patients who fail to respond to standard therapies for sepsis, may lead the physician to potentially reversible life-threatening diagnoses and management.

CONCLUSION

In the seemingly septic patient who does not respond to antimicrobials and fluids, the differential should be broadened to include acutely life-threatening conditions that can mimic sepsis. A review of the patient's medical history, medications, and recent exposures can assist in identifying the source of the patient's elevated body temperature and tachycardia. Consideration of potential sources and other mimics of sepsis is needed in the emergency department.

Effects of Therapeutic Hypothermia Combined with Other Neuroprotective Strategies on Ischemic Stroke: Review of Evidence

Ischemic stroke is a major cause of death and disability globally, and its incidence is increasing. The only treatment approved by the US Food and Drug Administration for acute ischemic stroke is thrombolytic treatment with recombinant tissue plasminogen activator. As an alternative, therapeutic hypothermia has shown excellent potential in preclinical and small clinical studies, but it has largely failed in large clinical studies. This has led clinicians to explore the combination of therapeutic hypothermia with other neuroprotective strategies. This review examines preclinical and clinical progress towards developing highly effective combination therapy involving hypothermia for stroke patients.

[Neuroleptic malignant syndrome]

BACKGROUND

Neuroleptic malignant syndrome (NMS) is a rare but severe undesired complication of psychopharmacological treatment. The mortality has shown a significant decrease since its first description. Knowledge of NMS is important for every clinician because of the need for rapid diagnosis and treatment.

OBJECTIVE

This article presents a review and critical appraisal of the current study situation for NMS. Recommendations for diagnostics, differential diagnostics and treatment are presented particularly from a clinical perspective.

MATERIAL AND METHODS

A literature review with the keywords "neuroleptic malignant syndrome", "Malignes neuroleptisches Syndrom" and various psychotropic drugs was performed in PubMed. The database of the Working Group for Pharmaceutical Treatment of Psychiatric Diseases (Arbeitsgemeinschaft für Arzneimitteltherapie bei psychiatrischen Erkrankungen, AGATE) was analyzed with respect to registered cases of the undesired side effect NMS.

RESULTS

In contrast to the first description, which also led to the name, there are now case reports of clinical conditions similar to NMS, which were obviously triggered by several groups of psychotropic drugs not just antipsychotic agents (German: Neuroleptika). Treatment recommendations exist whereby the effectiveness cannot always be scientifically substantiated; however, it is still undisputed that a rapid initiation of treatment is of great importance.

DISCUSSION

The psychiatrist must be familiar with the symptoms of NMS, its differential diagnosis and the therapeutic options for a rapid and effective treatment. Further studies are urgently needed for scientific substantiation of the pathophysiology of NMS and to develop evidence-based guidelines for treatment.

Is It Exertional Heatstroke or Something More? A Case Report

BACKGROUND

Heat stroke, heat-related illness, and malignant hyperthermia all present with hyperthermia. The former two are common presentations in the emergency department (ED). On the other hand, malignant hyperthermia (MH) is an uncommon but equally dangerous condition that requires prompt recognition and specific treatment with dantrolene sodium and avoidance of certain medications to reduce morbidity and mortality. Recent research focusing on nonanesthetic or exercise-induced MH has demonstrated a relationship between certain gene mutations and malignant hyperthermia susceptibility.

CASE REPORT

We report the case of a 19 year-old man with a family history of MH who was treated for exertional heat stroke, but despite cooling and adequate fluid resuscitation, demonstrated worsening rhabdomyolysis that subsequently responded to the administration of dantrolene sodium. WHY SHOULD AN EMERGENCY PHYSICIAN BE AWARE OF THIS?: This case illustrates the importance of recognizing the potential relationship between exertional heat stroke and malignant hyperthermia. The overlap between heat stroke and malignant hyperthermia susceptibility has important implications in the treatment and evaluation of patients presenting with signs and symptoms of heat stroke or heat-related illness in the ED.

Dantrolene enhances the protective effect of hypothermia on cerebral cortex neurons

Therapeutic hypothermia is the most promising non-pharmacological neuroprotective strategy against ischemic injury. However, shivering is the most common adverse reaction. Many studies have shown that dantrolene is neuroprotective in in vitro and in vivo ischemic injury models. In addition to its neuroprotective effect, dantrolene neutralizes the adverse reaction of hypothermia. Dantrolene may be an effective adjunctive therapy to enhance the neuroprotection of hypothermia in treating ischemic stroke. Cortical neurons isolated from rat fetuses were exposed to 90 minutes of oxygen-glucose deprivation followed by reoxygenation. Neurons were treated with 40 μM dantrolene, hypothermia (at 33°C), or the combination of both for 12 hours. Results revealed that the combination of dantrolene and hypothermia increased neuronal survival and the mitochondrial membrane potential, and reduced intracellular active oxygen cytoplasmic histone-associated DNA fragmentation, and apoptosis. Furthermore, improvements in cell morphology were observed. The combined treatment enhanced these responses compared with either treatment alone. These findings indicate that dantrolene may be used as an effective adjunctive therapy to enhance the neuroprotective effects of hypothermia in ischemic stroke.

Malignant hyperthermia: clinical and molecular aspects

CONTENT

Malignant hyperthermia (MH) is a potentially lethal pharmacogenetic disorder that affects genetically predisposed individuals. It manifests in susceptible individuals in response to exposure to Inhalant anesthetics, depolarizing muscle relaxants or extreme physical activity in hot environments. During exposure to these triggering agents, there is a rapid and sustained increase of myoplasmic calcium (Ca(2+)) concentration induced by hyperactivation of ryanodine receptor of skeletal muscle (RyR1), causing a profound change in Ca(2+) homeostasis, featuring a hypermetabolic state. RyR1, Ca(2+) release channels of sarcoplasmic reticulum, is the primary locus for MH susceptibility. Several mutations in the gene encoding the protein RyR1 have been identified; however, other genes may be involved. Actually, the standard method for diagnosing MH susceptibility is the muscle contracture test for exposure to halothane-caffeine (CHCT) and the only treatment is the use of dantrolene. However, with advances in molecular genetics, a full understanding of the disease etiology may be provided, favoring the development of an accurate diagnosis, less invasive, with DNA test, and also will provide the development of new therapeutic strategies for treatment of MH. Thus, this brief review aims to integrate molecular and clinical aspects of MH, gathering input for a better understanding of this channelopathy.

Heat-related illness

Environmental exposure to high temperatures can result in abnormalities ranging from mild heat exhaustion to heat stroke with multiorgan system failure. An understanding of the mechanisms of thermoregulation and how those mechanisms fail with extreme heat stress is critical for management of the patient with elevated body temperature in the emergency department.

Heat-related illness: a hot topic in critical care

With current predictions of climate change, the incidence of heat-related illnesses is projected to increase. Heat-related illnesses occur on a continuum from mild symptoms to fatalities. To prevent heat-related illnesses, nurses should have comprehension of persons at risk. Primary treatment of heat-related illness centers on cooling, but not overcooling, the patient. Heatstroke involves coagulopathies and cytokines, and can result in systemic inflammatory response syndrome and multiple organ dysfunction. Critical care nursing intervention requires more than effective cooling to support bodily processes that have been damaged or destroyed by the pathophysiology of heatstroke.

Exertional Heat Stroke – The Athlete's Nemesis

Heat stroke represents the extreme end of a spectrum of heat-related illnesses. It can occur in endurance athletes. Its incidence is probably under-reported. Patients present confused, drowsy or comatose, with a raised core temperature, but often a falsely reassuring peripheral temperature. Treatment is centred on reducing the core temperature as rapidly as possible and appropriate supportive management. Even with prompt treatment, it is associated with multi-organ dysfunction and death. Patients are often misdiagnosed, or diagnosed late. This is probably exacerbated by a wide differential diagnosis, the need for a core temperature measurement to reach the diagnosis and clinicians being unfamiliar with the disease. The need for immediate recognition, and immediate treatment compounds the problem. Survivors may experience long-term neurological disability and may be at risk of a further episode. Patients should return to sport gradually and only when they feel well. Its epidemiology, pathophysiology and clinical management are reviewed.

Effects of continuous venous-venous hemofiltration on heat stroke patients: a retrospective study

BACKGROUND

Heat stroke (HS) is a fatal illness characterized by an elevated core body temperature above 40°C and complicated with rhabdomyolysis and acute renal failure. We retrospectively analyzed the effect of continuous veno-venous hemofiltration (CVVH) in patients with HS.

METHODS

A total of 16 patients with HS were retrospectively analyzed. All patients were treated by CVVH for at least 96 hours, and CVVH was initiated with replacement fluid between 25°C and 30°C for 2 hours to 2.5 hours, and 36°C thereafter. The vital signs were monitored and blood samples were collected during CVVH to measure serum urea, creatinine, myoglobin, creatine kinase, and total bilirubin.

RESULTS

All patients survived. The core temperature of the patients decreased from 41.3 ± 0.2°C to 38.7 ± 0.1°C after 2 hours and to 36.7 ± 0.1°C after 5 hours during CVVH (p < 0.05). Compared with values before starting CVVH, there were remarkable improvements in mean arterial blood pressure, heart rate, and oxygenation index (p < 0.05). The serum creatinine, urea, myoglobin, and creatine kinase decreased significantly (p < 0.05), while the bilirubinemia had no obvious decline (p > 0.05). The scores of APACHE II and arterial lactate had also obvious decline (p < 0.05). The hemodynamic variables were stabilized during CVVH, and no obvious side effects related to CVVH were found.

CONCLUSIONS

CVVH is safe and feasible in the treatment of patients with HS by lowering core temperature, removal of myoglobin, support of multiorgan function, and modulating systemic inflammatory response syndrome (SIRS). The impact of CVVH on patient outcome, however, still needs proof by larger randomized controlled trials.

A case of severe heatstroke and review of pathophysiology, clinical presentation, and treatment

Heatstroke is life-threatening condition characterized by hyperthermia and central nervous system disturbances. It can also be classified as a form of systemic inflammatory response syndrome with multiple organ dysfunction and in many ways resembles sepsis. Like sepsis, most patients with heatstroke demonstrate a hyperdynamic hemodynamic response. In contrast to sepsis, rhabdomyolysis may complicate management and initial fluid resuscitation is not well defined. We present an illustrative case report and review of literature.

Dantrolene: mechanisms of neuroprotection and possible clinical applications in the neurointensive care unit

Calcium plays a central role in neuronal function and injury. Dantrolene, an inhibitor of the ryanodine receptor, inhibits intracellular calcium release from the sarco-endoplasmic reticulum. We review the available data of dantrolene as a potential neuroprotective agent and briefly summarize its other pharmacologic effects that may have potential applications for patients in the neurointensive care unit (NICU). Areas with the need for continued research are identified.

3,4-Methylenedioxymethamphetamine (Ecstasy) Activates Skeletal Muscle Nicotinic Acetylcholine Receptors

Adverse 3,4-methylenedioxymethamphetamine (MDMA; ecstasy) effects are usually ascribed to neurotransmitter release in the central nervous system. Since clinical features such as fasciculations, muscle cramps, rapidly progressing hyperthermia, hyperkalemia, and rhabdomyolysis point to the skeletal muscle as additional target, we studied the effects of MDMA on native and cultured skeletal muscle. We addressed the question whether malignant hyperthermia (MH)-susceptible (MHS) muscle is predisposed to adverse MDMA reactions. Force measurements on muscle strips showed that 100 microM MDMA, a concentration close to that determined in some MDMA users, regularly enhanced the sensitivity of skeletal muscle to caffeine-induced contractures but did not cause contractures on its own. The left-shift of the dose-response curve induced by MDMA was greater in normal than in MHS muscle. Furthermore, MDMA did not release Ca(2+) from isolated sarcoplasmic reticulum vesicles. These findings do not support the view of an MH-triggering effect on muscle. However, MDMA induced Ca(2+) transients in myotubes and increased their acidification rate. Surprisingly, alpha-bungarotoxin, a specific antagonist of the nicotinic acetylcholine receptor (nAChR), abolished these MDMA effects. The nAChR agonistic action of MDMA was confirmed by patch-clamp measurements of ion currents on human embryonic kidney cells expressing nAChR. We conclude that the neuromuscular junction is a target of MDMA and that an activation of nAChR contributes to the muscle-related symptoms of MDMA users. The drug may be of particular risk in individuals with abundant extrajunctional nAChR such as in generalized denervation or muscle regeneration processes and may act on central nAChR.

Dantrolene and heatstroke: a good molecule applied in an unsuitable situation

Because they share one pathognomonic sign (major hyperthermia), classic or environmental heatstroke and malignant hyperthermia have often been confronted from the therapeutic point of view. As expected and according to major physiopathological discrepancies between both syndromes, analysis of published data does not support effectiveness of dantrolene in heatstroke despite its significant reduction in mortality in malignant hyperthermia. If cooling methods still represent the cornerstone of the heatstroke therapeutic approach, the magnitude of heat-related deaths and the morbidity associated with the August 2003 French heatwave have highlighted the need for more ambitious methods of treatment.