How diabetic ketoacidosis develops

Diabetic ketoacidosis (DKA) is a medical emergency. All metabolic disturbances seen in DKA are the indirect or direct consequences of the lack of insulin (Fig 33.1). Decreased glucose transport into tissues leads to hyperglycaemia, which gives rise to glycosuria. Increased lipolysis causes overproduction of fatty acids, some of which are converted into ketones, giving ketonaemia, metabolic acidosis and ketonuria. Glycosuria causes an osmotic diuresis, which leads to the loss of water and electrolytes – sodium, potassium, calcium, magnesium, phosphate and chloride. Dehydration, if severe, produces pre-renal uraemia and may lead to hypovolaemic shock. The severe metabolic acidosis is partially compensated by an increased ventilation rate (Kussmaul breathing). Frequent vomiting is also usually present and accentuates the loss of water and electrolytes. Thus the development of DKA is a series of interlocking vicious circles all of which must be broken to aid the restoration of normal carbohydrate and lipid metabolism.

The most common precipitating factors in the development of DKA are infection, myocardial infarction, trauma or omission of insulin.

Treatment

The management of DKA requires the administration of three agents:

In most cases, rehydration and insulin therapy will correct the metabolic acidosis, and no further therapy is indicated. However, in the most severe cases when the hydrogen ion concentration is greater than 100 nmol/L, IV sodium bicarbonate may be indicated.

The detailed management of diabetic ketoacidosis is shown in Figure 33.2. The importance of good fluid balance charts, as in any serious fluid and electrolyte disorder, cannot be over-emphasized. The initial high input of physiological (0.9%) saline is cut back as the patient’s fluid and electrolyte deficit improves. Intravenous insulin is given by continuous infusion using an automated pump, and potassium supplements are added to the fluid regimen. The hallmark of good management of a patient with DKA is close clinical and biochemical monitoring.