It is most important for the HCPs to recognize potential problems rather than specific temperatures at which to expect these problems.
Hyperglycemia is common in mild and moderate hypothermia; specific measures to reduce blood sugar are seldom necessary. Hypoglycemia can develop in severely hypothermic patients, and dextrose supplementation (5% in IV fluids) is recommended empirically.
Hypokalemia is common in mild-to-moderate hypothermia, and supplementation is necessary (KCl in IV fluids, 20 mEq/L) empirically. Hyperkalemia is reported in severe hypothermia; specific measures (e.g., insulin-dextrose administration, bicarbonate administration) may be necessary if potassium is >7-8 mmol/L. Check electrolytes, if able.
Metabolic and respiratory acidosis are reported in most types and degrees of hypothermia; these typically correct with fluid therapy and patient warming.
Hemostatic defects are common. MWDs are commonly in a hypocoagulable state with prolonged clotting times, and platelet abnormalities are also noted. Monitor for bleeding diasthesis. Given the inability to correct coagulopathies and thrombocytopenias in MWDs in the deployed setting, any MWD with evidence of bleeding should be evacuated URGENTLY to a veterinary facility.
Tachycardia and hypertension are common in mild-to-moderate hypothermia. As hypothermia worsens, bradycardia and hypotension develop, and other cardiac arrhythmias may develop. Monitor continuous ECG and blood pressure. Avoid giving drugs, to include anti-arrhythmic agents, until the body temperature is >90°, as drugs are believed ineffective at temperatures below this.1,5
HCPs must be aware that measures to correct hypothermia can actually cause complications to develop, such as “afterdrop” and “rewarming shock;” thus, careful warming and close monitoring are essential when managing hypothermic patients.3,5
“Afterdrop” is the continued decrease in core temperature as warming is provided, due to the return of cold peripheral blood to the central circulation. To prevent “afterdrop,” it is important to warm the patient’s trunk (chest and abdomen), not the extremities.
“Rewarming shock” develops with excessively rapid warming and is due to the sudden development of systemic vasodilatation. This vasodilatation causes hypotension at a time when the circulatory system may not be able to react. The systemic hypotension is aggravated by the increased metabolic demand that develops as hypothermic patients are rewarmed, which increases the demand for perfusion. To prevent or reduce “rewarming shock,” IV fluid therapy must be provided and assessment of volume status (e.g., serial body weight measurement, clinical signs of hydration), systemic blood pressure, and tissue perfusion (e.g., evaluation of CRT, lactate clearance, change in mentation, urine output) must be monitored carefully.