Emergency surgery and diabetic ketoacidosis

Diabetic ketoacidosis results from inadequate insulin dosage or increased insulin requirements, often precipitated by infection, trauma or surgical stress. Diabetics who require emergency surgery often have a grossly elevated blood glucose concentration and occasionally overt ketoacidosis. Such patients require rehydration, correction of sodium depletion, correction of subsequent potassium depletion and i.v. soluble (Humulin S) insulin by infusion at an initial rate of 4-8 unit h~l.

Initial fluid replacement should consist of isotonic (0.9%) saline: 1 L in the first 30 min, 1 L in the next hour and a further 1 L over the next 2 h.

Progress is monitored by regular measurements of blood glucose, sodium and potassium concentrations, and arterial pH and blood gas tensions. Correction of acidosis with bicarbonate is rarely, if ever, required. Cellular potassium depletion is present from the outset, but hyperkalaemia or normokalaemia may be found initially because potassium shifts out of the cells in the presence of acidosis. Potassium replacement is required as the plasma concentration begins to decrease with the correction of the acidosis. Magnesium 5-10 mmol is also required. An infusion of glucose 5% should be given when the blood glucose concentration decreases to approximately 15 mmol L-1. When volume resuscitation is under way, and some reversal of acidosis and hyperglycaemia has been achieved, surgery may be carried out while management of the diabetes is continued intra- and postoperatively.

Table 35.9 Perioperative management of the insulin-dependent diabetic

Preoperative

Blood glucose profile; urea and electrolytes; urine ketones Adjust insulin therapy; most patients b.d. soluble + isophane

Poor control: change to t.i.d. soluble insulin and delay surgery Urgent surgery: glucose/instil in infusion (see below) Day of surgery

Check tasting blood glucose; repeat 2-hourly No subcutaneous insulin

Start infusion of 10% glucose [500 ml) with soluble (Humulin S) insulin 10 units and KCI 10 mmol at 0800 h to run 4—6 hourly

Adjust insulin in bag as follows depending on blood glucose: < 4 mmol L"t; no insulin

4-6 mmol L insulin 5 units per S00 ml glucose 10% 6-10 mmol L1: infusion as above

10-20 mmol L': insulin 15 units per 500 ml glucose 10%

> 20 mmol L1: insulin 20 units per 500 ml glucose 10%

Adjust potassium dosage depending on plasma K+concentration <■ 3 mmol I 1: add KCI 20 mmol L

Postoperative

Check blood glucose 2-6 hourly; check urea and electrolytes daily

Continue 4-6-hourly infusion until oral diet re-established

If delayed, change to decreased volume of 20-50% glucose with independent insulin infusion by syringe pump

When oral diet resumed, t.i.d. soluble insulin s.c.; daily dosage as preoperative

When requirements stable, restart normal regimen

Table 35.10 Sliding scale for infusion of insulin

Glucose concentration Infusion rate of insulin

<4.0

-

4.1-7

1

7.1-9

1.5

9.1-11

2

11.1-17

3

17.1-28

4

>28

6

Insulin administered via separate cannula from syringe pump.

Infusion comprises 50 units of human Actrapid insulin in 49,5 ml normal saline.

Glucose 4%/saline 0.18% solution is given via a separate cannula at a rate of 1.5 ml kg-' h-1 Blood glucose concentration is measured at 1-hourly intervals (initially) using BM stix and rate of insulin infusion adjusted according to sliding scale. When stability has been achieved blood glucose concentration may be measured at 4-hourly intervals.

Insulin administered via separate cannula from syringe pump.

Infusion comprises 50 units of human Actrapid insulin in 49,5 ml normal saline.

Glucose 4%/saline 0.18% solution is given via a separate cannula at a rate of 1.5 ml kg-' h-1 Blood glucose concentration is measured at 1-hourly intervals (initially) using BM stix and rate of insulin infusion adjusted according to sliding scale. When stability has been achieved blood glucose concentration may be measured at 4-hourly intervals.

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