definition of HHNK by Medical dictionary

1. characterized by or causing hyperglycemia.

2. an agent that has this effect.

hyperglycemic hyperosmolar nonketotic (HHNK) coma a metabolic derangement in which there is an abnormally high serum glucose level without ketoacidosis. It can occur as a complication of borderline and unrecognized diabetes mellitus, in pancreatic disorders that interfere with the production of insulin, as a complication of extensive burns, and in conditions marked by an excess of steroids, as in steroid therapy, or acute stress conditions, such as infection. It also may develop during total parenteral nutrition, hemodialysis, or peritoneal dialysis. Called also hyperosmolar nonketotic coma.

Symptoms. The hyperglycemia of HHNK coma is usually extreme, with fasting blood sugar levels ranging from 600 to 3000 mg per 100 ml of blood. In contrast to typical diabetic coma, however, the serum acetone level is normal or only slightly elevated. This occurs because, although there is sufficient insulin available to avoid ketosis, there is not enough to metabolize the glucose and thereby relieve the hyperglycemia.

Hyperosmolality, resulting from the extremely high concentration of sugar in the blood, causes a shift of water from the intracellular fluid (the less concentrated solution) into the blood (the higher concentrated solution). This results in cellular dehydration. Another symptom of HHNK coma, polyuria, occurs because the high plasma osmolality prevents the normal osmotic return of water to the blood by the renal tubules, and it is excreted in the urine. This leads to a decreased blood volume, which severely hampers the kidney’s excretion of glucose and a vicious cycle is begun.

Treatment. It is essential that HHNK coma be recognized early and treatment begun immediately to break the chain of metabolic aberrations that are occurring. It is estimated that the mortality rate of HHNK coma is 60 to 70 per cent; the probable reason for this is failure to recognize the condition and institute prompt corrective measures.

Insulin is administered in small doses, the amount and frequency depending on periodic assessment of blood glucose levels. The objective is to avoid the extremes of hyperglycemia and insulin shock. Intravenous fluids are administered cautiously, so that the sodium and water deficits can be corrected without producing extreme shifts of water from the blood into the intracellular compartment and thus failing to correct the hyperosmolar condition of the blood. Electrolytes other than the sodium lost through diuresis also must be replaced as indicated by laboratory findings.

Patient Care. Fluid volume deficit plays a major role in the development of severe HHNK coma; thus patient care is concerned with careful monitoring of those patients susceptible to its development, especially the elderly, the debilitated, and the mild or unsuspected diabetic. Maintenance of an adequate fluid balance can do much to prevent the hyperosmolar condition and the development of a chain of events that can rapidly lead to coma and death.

Miller-Keane Encyclopedia and Dictionary of Medicine, Nursing, and Allied Health, Seventh Edition. © 2003 by Saunders, an imprint of Elsevier, Inc. All rights reserved.

Leave a Comment