31: Temperature Disturbances

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CHAPTER 31 Temperature Disturbances

3 Does hypothermia have an impact on patient outcome?

Mild hypothermia (1° to 3° C) has the following effects:

TABLE 31-1 The Effects of Hypothermia on Organ Systems

System Effects
Vascular Increases systemic vascular resistance and peripheral hypoperfusion; plasma volume decreases because of cold diuresis
Cardiac Decreases heart rate, contractility, and cardiac output and produces arrhythmias
Pulmonary Increases pulmonary vascular resistance; decreases hypoxic pulmonary vasoconstriction; increases ventilation-perfusion mismatching; depresses ventilatory drive; decreases bronchial muscle tone increasing anatomic dead space; oxyhemoglobin dissociation curve shifts to the left
Renal Decreases renal blood flow and glomerular filtration rate; impaired sodium resorption and diuresis leading to hypovolemia
Hepatic Decreases hepatic blood flow, metabolic and excretory functions
Central nervous system Decreases cerebral blood flow; increases cerebral vascular resistance; oxygen consumption decreases by 7%/°C; evoked potential latencies are increased; MAC is decreased
Hematologic Decreased platelet aggregation and clotting factor activity; increased blood viscosity, impaired immune response
Metabolic Basal metabolic rate decreases; hyperglycemia and insulinopenia; decreased oxygen consumption and CO2 production
Healing Increased wound infections

MAC, Minimum alveolar concentration.

10 Describe the electrocardiographic manifestations of hypothermia

Mild hypothermia may be associated only with sinus bradycardia. Moderate hypothermia may result in prolonged PR intervals, widened QRS complexes, and a prolonged QT interval. Below 32° C an elevation of the junction of the QRS and ST segments known as the hypothermic hump or Osborne or J wave may be seen. Its size increases with decreasing body temperature; it usually is seen in leads II and V6 and may spread to leads V3 and V4. The J wave is not specific for hypothermia; it also may be seen in hypothalamic lesions and cardiac ischemia. Nodal rhythms are common below 30° C. Below 28° C premature ventricular contractions, atrioventricular blocks, and spontaneous atrial or ventricular fibrillation also occur. Ventricular fibrillation or asystole below 28° C is relatively unresponsive to atropine, countershock, or pacing. Resuscitative efforts should persist until the patient is rewarmed.