In hyperosmolar nonketotic hyperglycemia, the blood glucose is extremely high, more than 600 mg/dL, but ketoacidosis does not develop, or if it does develop, it is mild. Osmolality is usually in excess of 330 mOsm/L. There is also hemoconcentration and prerenal azotemia. Appreciation of the neurologic syndrome is generally credited to Wegierko, who published descriptions of it in 1956 and 1957. Most of the patients are elderly diabetics but some were not previously known to have been diabetic. An infection, enteritis, pancreatitis, dehydration, or a drug known to upset diabetic control (thiazides, corticosteroids, and phenytoin) leads to polyuria, fatigue, confusion, stupor, and coma. Often the syndrome arises in conjunction with the combined use of corticosteroids and phenytoin (which inhibits insulin release), for example, in elderly patients with brain tumors. The use of osmotic diuretics enhances the risk.
Seizures and focal signs such as a hemiparesis, a hemisensory defect, choreoathetosis, or a homonymous visual field defect are more common than in any other metabolic encephalopathy and may erroneously suggest the possibility of a stroke. Fluids should be replaced cautiously, using isotonic saline and potassium. Correction of the markedly elevated blood glucose requires relatively small amounts of insulin, since these patients often do not have a high degree of insulin resistance.
Hepatic Stupor and Coma (Hepatic, or
Chronic hepatic insufficiency with portosystemic shunting of blood is punctuated by episodes of stupor, coma, and other neurologic symptoms—a state referred to as hepatic stupor, coma, or encephalopathy. It was clearly delineated by Adams and Foley over 70 years ago. This state complicates all varieties of liver disease and is unrelated to jaundice or ascites. Any form of shunting, even without hepatic disease, such as surgical portal–systemic shunt (Eck fistula) is attended by the same clinical picture (see further on). There are also a number of hereditary hyperammonemic syndromes, usually first apparent in infancy or childhood (discussed extensively in Chap. 36) that lead to episodic coma with or without seizures. In all these states, it is common for an excess of protein derived from the diet or from gastrointestinal hemorrhage to induce or worsen the encephalopathy. Additional predisposing factors are hypoxia, hypokalemia, metabolic alkalosis, excessive diuresis, use of sedative hypnotic drugs, and constipation. A special from of the syndrome in epilepsy patients exposed to valproate; confusion and ataxia may occur acutely or subacutely in these patients (Gomcelli et al). Reye syndrome following viral infections in children, now infrequent, was also associated with very high levels of ammonia in the blood and encephalopathy (see further on).