Environmental 2:
Hyperthermia/Heat Stroke Portal
Heat-related illnesses occur when the thermoregulatory capacities of the body are exceeded. This imbalance between heat loss and heat produced by the body may result from excess heat production or an inability to effectively dissipate the body's heat.
Heat-related illnesses may be manifested as heat cramps characterized by painful muscle spasms, heat syncope with the patient fainting due to hypotension caused by peripheral vasodilation, heat exhaustion due to hypovolemia, or heat stroke where the heat generated in the body overwhelms the body's heat dissipation ability, resulting in core body temperature rises to levels in excess of 105°F to 106°F.
Treat the life-threatening emergency of heat stroke aggressively.
Symptoms
- Light headedness, nausea, weakness, blurred vision, anorexia, tachycardia, tachypneic syncope, and orthostatic hypotension
- The triad of heat stroke symptoms includes hyperpyrexia, CNS dysfunction, and anhidrosis (lack of sweating). (Sweating does not rule out heat stroke.)
- The sweating mechanism occurs early and briefly, then stops.
- The body’s core temperature rises higher than 104°F to 106°F.
- Severe cases include hot, dry skin, disorientation, unsteady gait, and unconsciousness.
Laboratory Findings
- Hematuria, proteinuria, leukocytosis, elevated BUN
- Thrombocytopenia, prolonged clotting studies
- ABGs may indicate respiratory alkalosis.
- Hypoglycemia, decreased calcium, hypokalemia
- In severe cases, the patient may develop DIC, profound lactic acidosis, increased intracranial pressure secondary to cerebral edema, and progressive renal or liver damage.
In practice, consider 3 factors:
- degree of body temperature elevation,
- duration of elevated temperature, and
- presenting signs and symptoms of the hyperthermia.
Treatment
The goal of therapy is rapid reduction of the core temperature to 104° F. Cooling below this level may result in overshooting and cause a hypothermic condition.
- Quickly secure the airway and apply high-flow oxygen.
- Monitor the cardiac function, SaO2, and core temperature.
- Establish intravenous access and give an initial bolus of 20 to 40 cc/kg cool NS or lactated Ringer’s as needed to establish and maintain a normal hemodynamic state as manifested by normalization of pulse, BP, LOC, and renal output.
- Continue IV infusions at 200 to 250 cc/h.
- Consider use of CVP to monitor resuscitation.
- Insert a Foley catheter as soon as possible.
- Obtain an ECG and chest x-ray.
- A brain CT and lumbar puncture may also be needed to establish a diagnosis. Laboratory tests should include CBC, complete electrolytes, liver function, BUN, cardiac enzymes, coagulation studies, ABGs, and urinalysis.
Mechanisms for cooling include: immersion in ice water baths; cold packs to the abdomen, neck, and groin; use of tepid water and fans to facilitate evaporation; cold water gastric lavage; cold peritoneal lavage; and IV fluid therapy with IV solution that has been cooled.
Antipyretics are not effective in heat stroke, so attend to other means of reducing the temperature. Choose a method of cooling that is easy to perform and that accommodates patient monitoring. Some methods (such as water baths) may reduce temperature quickly but may interfere with patient monitoring. Evaporative techniques (such as spraying the patient with tepid water and then using fans for cooling) are effective. Place monitoring electrodes on the patient's back if they will not adhere to the wet skin. Shivering is a common complication and may be initially controlled with the use of intravenous benzodiazepines and then maintained with phenothiazines. Do not use gastric lavage unless the airway is secured by ET intubation.
Management of Complications of Hyperthermia
- Seizures: Use benzodiazepine initially to control; then use phenobarbitals to maintain suppressed seizure activity.
- Hematologic: Treat DIC with platelets or FF plasma.
- Cardiac: For persistent hypotension, cardiac failure, or cardiac arrhythmias, use standard treatment guidelines.
- Renal and hepatic: Standard management guidelines apply to cases where renal failure and liver damage are present.
- For associated injury or illness, use standard treatment guidelines.