Patients admitted to a surgical department are often fasted for long period and for multiple days while on the acute theatre lists. Insulin dependent patients (both type 1 and 2 diabetics) require monitoring to ensure (something close to) euglycaemia.
Fasting patients with a basal insulin requirement
The general rule is to continue basal insulin in the fasted patient. Consider that the insulin dependent patient is taking the insulin because their endogenous supply is absent or insufficient…
Long acting insulins (Lantus, Protophane, Isophane NPH)
These should be continued, usually 80% of the usual dose. Fasting is not a reason to withhold basal insulin unless there is significant risk of hypoglycaemia, in which case one should start thinking about glucose-insulin infusion.
Short acting insulins (Actrapid, Apidra, Novorapid, Humalog)
These should be withheld unless required to prevent or treat hyperglycaemia.
Glucose-insulin infusions…
Are probably the best way to manage blood sugar in the insulin dependent inpatient. They can be charted in many ways and most hospitals will have a protocol so you should consult that…
Generally some kind of dextrose containing saline solution (commonly 5% dextrose + 20mmol KCl in half normal saline) with a rapid acting insulin. These are continuous infusion with fast-on/fast-off profiles, if they are stopped it should not be for long.
If you are lost...
- 5% dextrose + 20mmol potassium chloride in 0.45% sodium chloride at 80-125mL/hour;
- 50 IU neutral insulin (Acrapid) in 50mL (1IU/mL) per sliding scale;
- Probably continue long acting insulins during continuous infusions (but don’t forget the clinical judgement you learned in medical school).
Standard insulin sliding scale for continuous infusions
| Capillary glucose (mmol/L) | Rate (mg/hour=IU/hour) |
|---|---|
| <4.0 | STOP |
| 4.1 - 8.0 | 1 |
| 8.1 - 12.0 | 2 |
| 12.1 - 16.0 | 4 |
| 16.1 - 20.0 | 5 |
| 20.1 - 24.0 | 6 |
| >24.1 | 8 |
Warning
If the insulin drops below 4.0: STOP the infusion, treat the hypoglycaemia, and RESTART the infusion within 20 minutes.
If the the capilliary glucose is consistently borderline (~4.0-6.0mmol) the insulin dosing should be reduced to maintain something closer to euglycaemia. Particularly in patients with CVA or ACS.