The patient with chronic hypothermia may resemble one with hypothyroidism with puffy facies, slow hoarse speech and mental changes. The skin has a doughy consistency. Neurological features include dysarthria, ataxia and amnesia. With worsening, the pulse gets weaker and slower, shivering ceases, respirations are slow and shallow and the patient becomes very pale. Confusion worsens sometimes to delirium and muscular rigidity develops.
Further deterioration leads to stupor or coma.
The clinical context of the hypothermia is often the best clue to the underlying cause. Environmental exposure to cold or a history or findings or a high cervical cord lesion, polyneuropathy, hypothyroidism are usually obvious. Evoked responses are less affected. This effect is modified by anesthesia and carbon dioxide concentration. Serum potassium should be checked, as hyperkalemia is a common accompaniment.