8.2.4 - Hyperglycemic, Hyperosmotic, Nonketotic Coma (HHNC)

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As mentioned in the previous section, type 2 diabetics are much less likely to develop DKA. However, they are at risk of developing a potentially much more serious condition called hyperglycemic, hyperosmotic, nonketotic coma (HHNC). Those at risk for this complication are typically elderly patients who are experiencing some other major medical event. The onset is slower than with DKA and the mortality rate is much higher (up to 15%). As the name implies, this condition is associated with hyperglycemia (blood glucose levels as high as 600-1200 mg/dl) and hyperosmolarity of the extracellular fluids.

Causes 

HHNC is usually brought on by some major medical event such as a heart attack, stroke, an infection, or another acute illness. Because of the severity of the precipitating condition, HHNC often goes undiagnosed until it has progressed to a critical stage. The relative insulin deficiency with inadequate fluid intake seems to be the underlying causes of HHNC. Since there is not an absolute absence of insulin ketosis does not accompany this condition. Blood glucose levels are very high, 600-1200 mg/dl, resulting in polyuria and dehydration.

Symptoms

Presenting symptoms include profound dehydration and hyperosmolarity. Due to the loss of body fluids the patient usually has very low blood pressure and a fast heart rate. The patient may experience confusion, and reduced mental function, eventually leading to coma. One notable difference between HHNC and DKA is a lack of the nausea, vomiting, abdominal pain and altered respiration seen with DKA. This is probably due to the lack of ketogenesis and acidosis in HHNC.

Preventions and Treatment 

As with all complications of diabetes the best means of prevention is to carefully monitor and regulate blood glucose levels. Since this condition is more common in elderly patients who may suffer from mental incapacities associated with old age, caregivers must be vigilant to ensure that the patient’s blood glucose levels are maintained, and that they are getting proper nourishment and drinking enough amounts of fluids.

Treatment is like that of DKA with an emphasis on rehydrating the patient and lowering the blood glucose levels. Since HHNC is usually caused by some other medical event it is critical to identify and treat the precipitating illness.