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94
VOLUME 9 NUMBER 2 • JUNE 2012
HANDS ON
SA JOURNAL OF DIABETES & VASCULAR DISEASE
If blood glucose levels are persistently below 5.9 mmol/l, the adjust-
ment insulin dosages must be reduced to avoid possible hypoglycaemia.
The in-patient setting is aimed at avoiding excessive hyperglycaemia
and not to achieve ideal diabetic control. Hypoglycaemia is defined as
a glucose level ≤ 3.9 mmol/l and will require specific instructions and
modification of the supplementary insulin protocol.
If the glucose level remains low, intravenous glucose must be given to
maintain safe levels until the cause of the hypoglycaemia has been elimi-
nated. If blood glucose levels remain above 14 mmol/l, an incremental
increase in insulin dosages can be planned, usually by two units at a
time, to avoid excessive hyperglycaemia, while at the same time, basal
insulin should be considered.
Timing of glucose tests
The use of sliding scales and the testing of glucose six hourly have both
become obsolete practices.
5
Pre-meal testing in hospital provides safe
adjustments of glucose levels, and with the availability of short-acting
insulin analogues, insulin can be administered at the time of the meal,
thus avoiding delays and the risk of hypoglycaemia. The ‘supplementary’
short-acting insulin doses are added to basal insulin or even oral
anti-diabetic agents as appropriate and provide a rational and safe
physiological adjustment of insulin requirements.
Planned surgery in the previously diabetic patient
The use of insulin and glucose infusion is recommended for the following:
type 1 diabetes patients
•
insulin-treated type 2 diabetes patients
•
poorly controlled type 2 diabetes patients
•
if they are undergoing general anaesthesia, irrespective of the length of
the proposed anaesthesia and surgery.
The intravenous infusion of insulin provides a predictable, easily adjusted
and easily monitored effect on glucose levels. Subcutaneous administration
of insulin is unpredictable in the surgical patient. Minor procedures such as
endoscopy and procedures done under light sedation would not warrant in-
travenous insulin and glucose infusions, as patients will have a limited period
where they are at risk of transient hyperglycaemia, they will commence eat-
ing early, and can return to their normal treatment without complications.
It is preferable to use separate infusions for glucose and insulin to
enable independent adjustments as required (Table 2). Potassium levels
must also be carefully monitored to avoid hypokalaemia. It is necessary to
do hourly capillary blood glucose measurements to allow adjustments.
Patients undergoing coronary artery bypass graft surgery or surgery
requiring cardiopulmonary bypass may require higher doses of insulin to
achieve adequate glycaemic control during surgery and post-operatively.
In this situation, tighter glucose control has been shown to improve car-
diovascular morbidity and mortality and post-operative outcome in diabetic
patients.
6-9
Treatment goals in these patients should be 5.6–6.9 mmol/l but
with the same safeguards against hypoglycaemia as mentioned above.
Diabetes management for diabetic patients during minor
surgical procedures
The following protocol is advised (Table 3). If breakfast is allowed on the
day of the procedure, the normal morning dose of insulin, or oral agents
as used by the patient, can still be given. Then measure glucose levels
before and after the procedure and use supplemental insulin/protocol if
the glucose levels exceed 13.9 mmol/l.
The patient in the ICU
The ICU presents very specific challenges to the treating physician. It is in
this setting that the benefits of glycaemic control have best been studied
in various clinical situations. As discussed above, glucose variability is the
- Discontinue all subcutaneous insulin once the glucose–insulin infusion is
commenced.
- Measure capillary blood hourly.
- Infuse 5% dextrose–water in an infusion pump, preferably.
- Infuse a solution of 200 IU rapid-acting insulin (NovoRapid/Humalog/
Apidra) in 200 ml NaCl to achieve 1 IU/1 ml. This can be used as a pig-
gyback infusion to the dextrose infusion.
- Adjust the infusion/hourly glucose levels per suggested protocol.
Blood glucose
Insulin infusion
5% dextrose–water
(mmol/l)
(ml/hour) (units/hour)
(ml/hour)
< 3.9
0.5
0.5
150
3.9–5.6
1
1
125
5.7–8.0
2
2
100
8.1–10
4
4
50
10.1–12
6
6
0
12.2–14
8
8
0
≥ 14.1
10
10
0
If the patient is at risk of fluid overload, the insulin can be mixed in a more
concentrated solution, e.g. 400 IU/200 ml = 2 IU/ml. The infusion of dextrose
can be done via a central line and 50% dextrose can be used to limit the
volume required.
Table 2.
Example of insulin–glucose infusion for peri-operative periods.
On the day of the procedure if the patient is nil per os:
– Withhold the morning dose of insulin/oral agents.
– Measure capillary blood pre-operatively and at two to four hours.
– Give short-acting insulin (NovoRapid, Humalog, Apidra) subcutaneously
as follows:
Blood glucose
NovoRapid/Humalog/Apidra
(mmol/l)
(units)
< 5.6
0
5.7–11.1
4
11.2–13.9
6
14–16.7
8
≥ 16.8
10
Post-operatively give the usual insulin/oral agent.
Table 3.
Example of insulin supplementary scale for minor surgical
procedurers.