Slow breathing points to opiate or barbiturate intoxication and occasionally to hypothyroidism, whereas deep, rapid breathing (Kussmaul respiration) should suggest the presence of pneumonia, diabetic or uremic acidosis, pulmonary edema, or the less-common occurrence of an intracranial disease that causes central neurogenic hyperventilation. Diseases that elevate intracranial pressure or damage the brain often cause slow, irregular, or cyclic Cheyne-Stokes respiration. The various disordered patterns of breathing and their clinical significance are described further on. Vomiting at the outset of sudden coma, particularly if combined with pronounced hypertension, is characteristic of cerebral hemorrhage within the hemispheres, brainstem, cerebellum, or subarachnoid spaces. Marked hypertension is observed in patients with cerebral hemorrhage and in hypertensive encephalopathy and in children with markedly elevated intracranial pressure. Hypotension is the usual finding in states of depressed consciousness because of diabetes, alcohol or barbiturate intoxication, internal hemorrhage, myocardial infarction, dissecting aortic aneurysm, septicemia, Addison disease, or massive brain trauma. The heart rate, if exceptionally slow, suggests heart block from medications such as tricyclic antidepressants or anticonvulsants, or if combined with periodic breathing and hypertension, an increase in intracranial pressure.
Inspection of the skin may yield valuable information. Cyanosis of the lips and nail beds signifies inadequate oxygenation. Cherry-red coloration is typical of carbon monoxide poisoning. Multiple bruises (particularly a bruise or boggy area in the scalp), bleeding, CSF leakage from an ear or the nose, or periorbital hemorrhage greatly raises the likelihood of cranial fracture and intracranial trauma or of a severe coagulopathy causing intracranial bleeding. Telangiectases and hyperemia of the face and conjunctivae are the common stigmata of alcoholism; myxedema imparts a characteristic puffiness of the face, and hypopituitarism an equally characteristic sallow complexion. Marked pallor suggests internal hemorrhage. A macular-hemorrhagic rash indicates the possibility of meningococcal infection, staphylococcal endocarditis, typhus, or Rocky Mountain spotted fever. Excessive sweating suggests hypoglycemia or shock, and excessively dry skin, diabetic acidosis, or uremia. Large blisters, sometimes bloody, may form over pressure points such as the buttocks if the patient has been motionless for a time; this sign is particularly characteristic of the deeply unresponsive and prolonged motionless state of acute sedation, alcohol and opiate intoxication. Thrombotic thrombocytopenic purpura (TTP), disseminated intravascular coagulation, and diffuse fat embolism after bone injury may cause diffuse petechiae or purpura; the last of these are often aggregated in the anterior axillary folds.
The odor of the breath may provide a clue to the etiology of coma. Alcohol is easily recognized. The spoiled-fruit odor of diabetic ketoacidotic coma, the uriniferous odor of uremia, the musky and slightly fecal fetor of hepatic coma, and the burnt almond odor of cyanide poisoning are distinctive enough to be identified by physicians who possess a keen sense of smell. The distinctive odor of melena, experienced in the former open wards of large hospitals, is a sign of rapid gastrointestinal bleeding.
Neurologic Examination of the Stuporous or Comatose Patient