0.5 (+ increase glucose infusion)
Progress. When the patient can eat and drink s.c. insulin is restarted. The rate of fall of blood glucose/hour is proportional to the rate of infusion of insulin over the range of 1-10 units/h. A reasonable rate of fall during treatment is 4-5.5 mmol/1 (75-100 mg/100 ml) per hour.
Intravenous fluid and electrolytes.11 Patients are often more deficient in water than in saline and although initial replacement is by isotonic (0.9%) sodium chloride solution, occurrence of hyper-natraemia is an indication for half isotonic (0.45%) solution. A patient with diabetic ketoacidosis may have a fluid deficit of above 5 litres and may be given:
• then 4 litres in the next 24 hours, watching for signs of fluid overload.
Note that fluid replacement causes a fall in blood glucose by dilution.
Glucose should be given only when its concentration in blood falls below the renal threshold, in practice starting when the blood glucose falls to 10 mmol/1. If glucose is used at concentrations above the renal threshold it merely increases the diabetic osmotic diuresis, causing further dehydration and potassium and magnesium loss (but see Hypoglycaemia, above). When the blood glucose
11 In this situation glucose solution does not provide water replacement since the normal capacity to metabolise glucose is fully taken up.
level falls to 10 mmol/1, the fluid replacement should be changed from saline to 5% glucose, at the same rate as detailed above.
Potassium. Even if plasma potassium is normal or high, patients have a substantial total body deficit, and the plasma concentration will fall briskly with i.v. saline (dilution) and insulin which draws potassium into cells within minutes. Potassium chloride should be added to the second and subsequent litres of fluid according to plasma potassium (provided the patient is passing urine):
Bicarbonate (isotonic) should be used only if plasma pH is <7.0 and peripheral circulation is good; insulin corrects acidosis.
Success in treatment of diabetic ketoacidosis and its complications (hypokalaemia, aspiration of stomach contents, infection, shock, thromboembolism, cerebral oedema) depends on close, constant, informed supervision.
Mild diabetic ketosis. If the patient is fully conscious and there has been no nausea or vomiting for at least 12 h, intravenous therapy is unnecessary. It is reasonable to give small doses of insulin s.c. 4-6-hourly and fluids by mouth.
Hyperosmolar diabetic coma occurs chiefly in non-insulin-dependent diabetics who fail to compensate for their continuing, osmotic glucose diuresis. It is characterised by severe dehydration, a very high blood sugar (> 33 mmol/1:600 mg/100 ml) and lack of ketosis and acidosis. Treatment is with isotonic (0.9%) saline, at half the rate recommended for ketoacidotic coma, and with less potassium than in severe ketoacidosis. Insulin requirements are less than in ketoacidosis, where the acidosis causes resistance to the actions of insulin, and should generally be half those shown in Table 35.2. Patients are more liable to thrombosis and prophylactic heparin is used.
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