TABLE 1874 Comparison of Cooling Techniques

We favor evaporative cooling as the technique of choice: it is simple and the fastest noninvasive cooling technique in humans. Other simple measures include ice packs placed at the groin and axillae to cool blood in the axillary and femoral vessels. Gastric lavage is safe if a patient is intubated. Cooling with peritoneal lavage is an effective and rapid central cooling technique. Immersion cooling should be limited to situations where evaporative cooling is not possible.

Evaporative cooling is performed by positioning fan(s) close to the completely undressed patient and then sponging the skin or spraying tepid water on the patient. Inexpensive plastic spray bottles work the best. We avoid covering the patient with sheets and then wetting the sheets, because this impairs evaporation of heat from the skin. Only one person is needed to monitor and continue cooling the patient.

An extremely effective means of evaporative cooling reported in the literature is the Makkah body cooling unit (BCU). 16 Patients are placed undressed on a modified hammock or litter, sprayed with lukewarm water, and room temperature air is blown over them with powerful fans. This is the method of field treatment for pilgrims traveling to Mecca who succumb to heatstroke. The BCU is very effective in treating patients who are vasodilated and in a dry environment. This mode of therapy would not be ideal for patients in shock or in a humid environment. Also, it may be difficult to reproduce these physical conditions in conventional clinical practice.

Two problems associated with complications of evaporative cooling are shivering and inability of cardiac electrodes to adhere to the skin. Shivering is treated primarily with intravenous benzodiazepines and secondarily with phenothiazines. Phenothiazines, however, lower the seizure threshold. Cardiac electrodes can be applied to a patient's back.

Immersion cooling is performed by placing an undressed patient into a tub of water deep enough to cover the trunk and extremities. The head must be kept out of the water. Cardiac monitoring electrodes and rectal temperature probes must be secured to the patient. Problems associated with immersion cooling include shivering, displacement of monitoring leads, and inability to perform defibrillation or resuscitative procedures.

The most rapid method of cooling a heatstroke victim is cardiopulmonary bypass. Although the logistics and availability are major drawbacks, it may be required if a patient's condition is recalcitrant to all other measures.

Regardless of the cooling technique chosen, cooling efforts should be discontinued when the rectal temperature reaches 40°C (104°F). Continued cooling below this temperature will lead to "overshoot hypothermia."

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