While much of the treatment of diabetes focusses on the avoidance of long-term complications in an outpatient setting, hospitalisation of diabetes patients frequently is the result of a metabolic emergency. The hyperglycaemic emergencies, diabetic ketoacidosis and the hyperosmolar non-ketotic state, are usually found in those with new-onset diabetes or with poor self-management. On the other hand, severe hypoglycaemia is most frequently encountered in those with long durations of diabetes and tightly-controlled insulin therapy. As the term 'metabolic emergency' implies, both severe hyperglycaemia and severe hypoglycaemia are potentially lethal and require urgent attention.
Diabetic keto-acidosis and the hyperosmolar non-ketotic state
When there is a shortage of insulin, glucose will rise, and this is generally considered the hallmark of diabetes. However, insulin has an influence on many metabolic pathways, including protein and fatty acid metabolism. This is illustrated by diabetic keto-acidosis, where the real problem arises from the presence of large amounts of keto-acids (or ketones). These ketones are an oxidative metabolite of the free fatty acids which flood the plasma in response to very low or absent insulinemia (so called uncontrolled lipolysis). Because of the overwhelming metabolic acidosis, patients will usually present to the emergency ward with only moderately elevated glucose values. In contrast, in the hyperglycaemic hyperosmolar state there is usually just enough insulin to suppress lipolysis, so ketone-formation is not an issue and symptoms arise only when hyperglycaemia has resulted in severe dehydration.
While not all glucose-lowering medication will result in hypoglycaemia, those who use sulfonylurea derivatives (SUs) or insulin do run a risk of hypoglycaemia. Since definitions of hypoglycaemia vary, it is hard to ascertain the frequency of 'true' hypoglycaemia in daily practice. Many of those with type 2 diabetes using SUs and other oral drugs only will go without hypoglycaemia for years. On the other end of the spectrum are those with long-standing type 1 diabetes, complex insulin regimens and hypoglycaemia unawareness who may suffer from several episodes per day and who have a high risk of severe hypoglycaemia. The exact risks for an individual patient are hard to estimate, since many patient related factors, such as age, duration of diabetes, co-morbidity and co-medication will influence this risk.