- Establish the diagnosis first.
- Hyperglycaemia. Ususally plasma glucose is greater than 11 mmol/L.
- Acidosis. Arterial pH less than 7.3 and/or venous bicarbonate <15 mmol/L.
- Ketosis. Measured in whole blood with a ketone meter ideally, but measure urine or serum ketones if this is not available.
- Fluid resuscitation is the first priority.
- Give isotonic (normal saline initially. The following regimen is suggested but must be adusted to individual requirements.
- Give 1 L over 30 mins, followed by 1 L over 1 hour, 1 L over 4 hours, 1 L over 6 hours, and then 1 L every 8 hours.
- Once the plasma glucose is below 11 mmol/L, switch to 5% glucose (dextrose).
- The aim is to replace the fluid deficit within 24 hours.
- Measure the serum urea and electrolytes at baseline, 2 hours, 6 hours, and beyond as indicated. Use these to guide your fluid and potassium replacement regimen. See potassium, p. 552.
- The insulin regimen is aimed at reducing the blood glucose by 6 mmol/L per hour.
- Very large doses are not usually required, even if the blood glucose is very high.
- More insulin may be required if the patient is very acidotic, as this causes a degree of insulin resistance.
- Give an immediate dose of 10 units of soluble insulin intramuscularly.
- Set up an intravenous insulin sliding scale (see box on p. 397 for scale).
- 50 units of soluble insulin (e.g. Actrapid) in 50 mL isotonic (normal saline. Infuse according to the sliding scale (see box).
- If intravenous access is impossible, insulin can be given intramuscularly, 10 units each hour.
- Stop intramuscular insulin once the blood glucose falls below 15 mmol/L.
- Identify the underlying cause and identify strategies to avoid ketoacidosis in the future (see patient advice below).
- Switch to a subcutaneous regimen once the patient is clinically well, non-ketotic, non-acidotic, and normoglycaemic, and eating normally. Do not stop intravenous insulin until 1 hour after the first subcutaneous dose.
Treatment of non-ketotic hyperglycaemia, known as hyperosmolar non-ketotic coma (HONK)
- The clinical picture is usually one of insidious onset, unlike the acute presentation of ketoacidosis.
- The mortality from this condition is about 30%; seek help from specialists and intensive care.
- Establish the diagnosis:
- Hyperglycaemia. The blood glucose is frequenly greater than 40 mmol/L.
- Hyperosmolarity. Usually greater than 340 mosmol/L.
- Exclude ketosis. Patients may have a lactic acidosis owing to sepsis.
- Excessively rapid rehydration can cause cerebral oedema owing to the intracellular hyperosmolarity. Rehydrate the patient with isotonic (normal saline (avoid hypotonic saline). Aim to replace the fluid deficit over about 48 hours.
- Measure the serum urea and electrolytes at baseline, 2 hours, 6 hours, and beyond as indicated. Use these to guide your fluid and potassium replacement regimen. See potassium (p. 552).
- Set up an intravenous insulin sliding scale (see box below for scale)
- These patients are usually very sensitive to insulin and require lower doses than patients with ketoacidosis.
- Aim to reduce blood glucose by 3 mmol/h.
- Patients with non-ketotic hyperglycaemia are at risk of venous thromboembolism; anticoagulate the patient if there are no contraindications.
- Identify the underlying cause. Infection is the cause in more than 50% of cases; other causes include furosemide and phenytoin.
- Most patients presenting with non-ketotic hyperglycaemia will not require insulin in the long term.
Long-term insulin regimens
- Most patients are given recombinant human insulin. A dose reduction of 10% is usually required if a patient is switched from beef to human insulin; no dosage adjustment is usually required for pork insulin.
- All of these regimens are based on insulin given subcutaneously.
- Note that soluble insulin given subcutaneously takes 30 minutes to act, so it should be taken 30 minutes before a meal.
- The choice of insulin is often determined by the patient's preference for delivery device. There are many delivery systems available. Familiarize yourself with several of these, and involve a diabetes liaison nurse if you have access to one.
- The optimal regimen is one that takes account of the patient's lifestyle. The following are given as examples.
Basal-bolus regimen
- A long-acting insulin is given at bedtime.
- A short-acting insulin is given 3 times daily with meals.
- This regimen has the advantage that it allows flexibility to take account of different meal times and meal sizes. It is commonly used for patients with Type I diabetes. However, it requires a high level of monitoring and understanding in order to adjust dosages safely.
Twice-daily biphasic insulin regimen
- This regimen is less flexible but may be suitable for patients who have predictable meal times.
- A biphasic insulin is given twice daily, once at breakfast and once with the evening meal.
- Biphasic insulins contain soluble insulin and intermediate (isophane) insulin in variable proportions. The number in the name refers to the proportion of soluble insulin (e.g. Humulin M3 and Mixtard 30 contain 30% soluble insulin and 70% isophane insulin.
- The major disadvantage of this regimen is that increasing the dose increases both the short- and intermediate-acting components.
- Patients using this regimen will often need to have snacks mid-morning and during the evening.
- The insulin dosage will always need to be adjusted to the patient's requirements. The following is offered as an initial calculation. Add up the daily requirement while the patient is on a sliding scale, and make sure that they are eating and drinking normally during this time. The average daily requirement is 0.5 units/kg. Use the two-thirds rule:
- Use a biphasic insulin containing two-thirds isophane insulin (i.e. 30% soluble insulin).
- Give two-thirds of the daily dose in the morning and one-third in the evening (e.g. in a 70 kg man requiring 36 units daily, give 24 units in the morning and 12 units in the evening).
- See azathioprine (p. 515) for more information on giving drug dosages by body weight.
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