Hyperosmolar hyperglycemic state

Hyperosmolar hyperglycemic state (HHS) is a complication of diabetes mellitus (predominantly type 2) in which high blood sugars cause severe dehydration, increases in osmolarity (relative concentration of solute) and a high risk of complications, coma and death. It is diagnosed with blood tests. It is related to diabetic ketoacidosis (DKA), another complication of diabetes more often (but not exclusively) encountered in people with type 1 diabetes; they are differentiated with measurement of ketone bodies, organic molecules that are the underlying driver for DKA but are usually not detectable in HHS.

The treatment of HHS consists of correction of the dehydration with intravenous fluids, reduction of the blood sugar levels with insulin, and management of any underlying conditions that might have precipitated the illness, such as an acute infection.

Older names for HHS are hyperosmolar non-ketotic coma (HONK), nonketotic hyperosmolar coma, hyperosmolar hyperglycemic nonketotic syndrome (favoured by the American Diabetes Association). )

Signs and symptoms
The increasing hemoconcentration and volume depletion may result in:
 * Altered mental status
 * Neurologic signs including focal signs such as sensory or motor impairments or focal seizures or motor abnormalities, including flaccidity, depressed reflexes, tremors or fasciculations.
 * Hyperviscosity and increased risk of thrombosis
 * Ultimately, if untreated, will lead to death
 * Increase thirst (polydipsia)

Diagnosis
The major differential diagnosis is diabetic ketoacidosis (DKA). In contrast to DKA, serum glucose levels in HHS are extremely high, usually greater than 40-50 mmol/L, but an anion-gap metabolic acidosis is absent or mild. Altered mental status is also more common in HHS than DKA. Although traditionally DKA has been associated with Type I Diabetes, whereas HHS has been associated with Type II, HHS can be seen in patients of both types.

Cranial imaging is not used for diagnosis of this condition. However, if MRI were performed, it may show cortical restricted diffusion with unusual characteristics of reversible T2 hypointensity in the subcortical white matter.

Pathophysiology
Nonketotic coma is usually precipitated by an infection, myocardial infarction, stroke or another acute illness. A relative insulin deficiency leads to a serum glucose that is usually higher than 33 mmol/l (600 mg/dl), and a resulting serum osmolarity that is greater than 320 mOsm. This leads to polyuria (excessive urination, an osmotic diuresis), which, in turn, leads to volume depletion and hemoconcentration that causes a further increase in blood glucose level. Ketosis is absent because the presence of some insulin inhibits hormone-sensitive lipase (lipolysis).

Intravenous fluids
Treatment of HHS begins with reestablishing tissue perfusion using intravenous fluids. People with HHS can be dehydrated by 8 to 12 L. Attempts to correct this usually take place over 24 hours with initial rates of normal saline often in the range of 1 L/h for the first few hours.

Electrolyte replacement
Severe potassium deficits often occur in HHS. They usually range around 350 mEq in a 70 kg person. This is generally replaced at a rate 10 mEq per hour as long as there is urinary output.

Insulin
Insulin is given to reduce blood glucose concentration; however, as it also causes the movement of potassium into cells, serum potassium levels must be sufficiently high or dangerous hypokalemia may result. Once potassium levels have been verified to be greater than 3.3 mEq/l, then an insulin infusion of 0.1 units/kg is begun.