Hemmelgarn , DVM

Heatstroke is a complex disease process that, in its most severe form, can result in multiorgan dysfunction and death. Heatstroke stems from the failure of the body’s thermoregulatory mechanisms, resulting in cellular damage and death. The organ systems most commonly affected in this disease process include the gastrointestinal tract and the coagulation, renal, cardiac, pulmonary, and central nervous systems. Heatstroke is diagnosed based on the patient history, physical examination, and clinicopathologic findings. Treatment should be instituted immediately to improve patient outcome and includes active cooling, fluid resuscitation, and supportive care. Patients with altered mental status, hypoglycemia, prolonged prothrombin time, and prolonged activated partial thromboplastin time at admission have increased mortality rates. Additional negative prognostic indicators include elevated serum creatinine level, delayed admission to the hospital, seizures, and obesity. Heatstroke: Clinical Signs, Diagnosis, Treatment, and Prognosis Heatstroke is the most severe form of heat-related illness. Recently, a new definition of heatstroke for human patients has been proposed: “A form of hyperthermia associated with a systemic inflammatory response leading to a syndrome of multi-organ dysfunction in which encephalopathy predominates.”1 A similar disease process has been seen in veterinary patients. Regardless of the definition, this disease process is often progressive and can be life threatening. Multiorgan dysfunction is the hallmark of heatstroke. Affected organ systems often include the gastrointestinal tract and the coagulation, renal, pulmonary, and central nervous systems. Common sequelae of heatstroke include disseminated intravascular coagulation (DIC), acute lung injury or acute respiratory distress syndrome, and acute kidney injury. This article discusses the clinical signs and diagnosis of, as well as treatment options and prognosis for, heatstroke. Clinical Signs and Diagnosis History and Patient Assessment Patients suffering from heat-related illnesses have clinical signs that vary greatly depending on the severity of the disease. Therefore, a thorough history is key in the initial stages of heatstroke management. Often, the history includes exposure to increased environmental temperatures or strenuous exercise without acclimatization. During the initial evaluation, owners should be questioned about underlying medical conditions and concurrent medication administration. Known predisposing factors or heatstroke include obesity, cardiovascular disease, neurologic/neuromuscular disease, upper airway abnormalities, strenuous exercise, and confinement with poor ventilation. Patient assessment and treatment should be performed simultaneously. Initial assessment of the patient using the CAB (cardiovascular-airway-breathing) approach is essential for all patients that are potentially suffering from a heat-related illness. The patient should be assessed for the presence of a heartbeat, a patent airway, and normal respiratory excursions. After the initial assessment is done, a second, more comprehensive examination of all body systems should be performed and appropriate therapies initiated (FIGURE 1). Evaluation of the patient’s cardiopulmonary systems to determine if signs of shock are present should include a visual assessment in conjunction with thoracic auscultation and assessment of perfusion parameters (mentation, pulse quality, mucous membrane color, capillary refill time; TABLE 1). Apnea or agonal breathing is an indication for immediate intubation to secure the patient’s airway. Breathing patients should be examined closely for evidence of upper airway obstruction (inspiratory stridor), abnormal respiratory patterns, or both, as upper and lower airway disease can be concurrent in patients with heatstroke. Systematic auscultation of the thoracic cavity aids in identifying cardiac arrhythmias, murmurs, and adventitious breath For more information, please see the companion article, “Heatstroke: Thermoregulation, Pathophysiology, and Predisposing Factors.”