Coma in Diabetes Mellitus

GR Sridhar, Endocrine and Diabetes Centre, Visakhapatnam - 530002.

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Coma has been defined as unarousable unresponsiveness to stimulation, in contrast to stupor, where the individual is markedly unresponsive, but arousal is possible by stimulation and lethargy, characterised by dullness, decreased mental alertness, confusion and drowsiness (Duman S, 1996).

The causes of coma can be classified into metabolic, diffuse intracranial disease, cerebral hemispheric lesions and brain stem lesions (Harrison 1996). Among metabolic causes, Hyperglycemia and hypoglycemia due to diabetes are prominent in certain populations. Other metabolic causes include drug overdosage,cardiac, respiratory, hepatic and renal failure, hyponatremia, hypercalcemia, sepsis and alcohol overdosage.

In diabetes altered consciousness leading to come can occur due to

Hypoglycemia

Euglycemia is maintained by a complex interplay of hormones, neurotransmitters and substrate effects. Insulin is the predominant glucose lowering hormone. There are redundant glucose raising factors including glucagon, catecholamines and growth hormone. Glucose is the major metabolic fuel for the brain, which must be preserved and therefore the redundant counter-insulin hormones.

Excess insulin can result in diabetes mellitus due to a variety of factors

How common is hypoglycemia in type 1 diabetes mellitus ? It has been stated that an individual with type 1 diabetes mellitus, who is treated for 30 years with two daily doses of insulin to avoid symptoms of hyperglycemia will have 1482 hypoglycemic episodes which are self treated, and another six severe episodes of hypoglycemia which require intravenous glucose or leading to come (Santiago RV, 1994).

When the aim is to achieve euglycemia, the risk of developing hypoglycemia is much more. In the Diabetes Control and Complications Trial (DCCT) the group in intensive insulin therapy ran three times the risk of hypoglycemia compared to the conventional treatment group (DCCT, NEJM 1993....).

Considering that type 1 diabetes is less commonly reported in most reports from India (ref....) what is the risk of hypoglycemia in treatment of type 2 diabetes ? The UK Prospective Diabetes Study, done in type 2 diabetes patients, is comparable to DCCT in type 2 diabetes. Mild hypoglycemia was reported in 35% of insulin treated patients after three years. In comparison, 12% of those treated with chlorpropamide and 29% with glibenclamide reported mild hypoglycemia in the same period. By contrast, 6.6% patients on insulin had at least one attack of hypoglycemia that was severe enough to need outside assistance. The prevalence was 2% in chlorpropamide treated group and 3.7% in glibenclamide treated group (ref.....).

The question then arises whether hypoglycemia is less common in type 2 diabetes. One reason that has been put forward is that counterregulatory hormones are preserved in type 2 diabetes, and the risk of hypoglycemia is less. Secondly, one may be attempting to achieve less strict glycemic control than in type 1 patients. Lastly there is a suggestion that retained endogenous insulin reserve in type 2 diabetes mellitus results in lesser dependence on injected insulin, and a more stable insulin profile (Heller SR, 1993).

How is hypoglycemia defined ? A blood glucose level less than 50 mg/dl is the biochemical definition of hypoglycemia. Such a definition may not be clinically useful or relevant, as hypoglycemic symptoms may be perceived at much higher or lower levels by different individuals and by the same individual at different times.......

A clinical definition of hypoglycemia has been employed. Mild hypoglycemia is characterised by the occurrence of cholinergic manifestations such as sweating, and adrenergic manifestations such as tachycardia. In moderate clinical hypoglycemia there is readily apparent neurologic dysfunction, such as poor concentration, confusion, blurred vision or poor coordination. Severe hypoglycemia is defined as neurological status which is so severely compromised that external assistance is required.

Clinical definition of hypoglycemia does not require measurement of blood glucose. If clinical features of hypoglycemia are rapidly reversed by measures that raise blood glucose, hypoglycemia is presumed to have occurred (Santiago, 1994).

Risk factors for hypoglycemia

The six S's of hypoglycemia. The following memory grid can be useful to remember hypoglycemic symptoms, especially in a child

  1. Shaky
  2. Sweaty (but cool to touch)
  3. Sleepy (not tired)
  4. Starving
  5. Stubborn
  6. 'Spacey'

Symptoms and signs of hypoglycemia can be grouped into:

15/15 rule for treatment of mild hypoglycemia: When blood glucose falls below 70 mg/dl the following guidelines can be employed for management:

*15 gm carbohydrate is equivalent to 1 teaspoonful of honey or sugar/ 1/2 cup of orange juice/ 1 cup skim milk/ 3/4 cup of soft drink


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