Myocardial Infarction or Stroke

The DIGAMI study (Malmberg K et al 1995, 1997) showed that after myocardial infarction an insulin/glucose infusion with subsequent basal/bolus regimen improved survival in the diabetic person with Type 2 diabetes. This study is slightly complicated by several factors (Fisher 1998). Many of the control group went on to insulin, many of the intervention group came off insulin, some of the subjects may have had stress hyperglycaemia rather than diabetes. Nonetheless, many would now recommend an insulin-glucose infusion for acute myocardial infarction in diabetic subjects with appropriate blood glucose control afterwards, not necessarily with insulin. The DIGAMI protocol is given in Table 5.6, but many units use their own, less complicated glucose-insulin-potassium infusion schemes.

There is also a strong suggestion that an insulin-glucose infusion should be used after a cerebrovascular accident (Scott et al 1998, 1999). Although this is still very much at the research stage, it appears safe and may well become clinical practice.

If a subject is unable to eat, then an insulin-glucose infusion is the best way to maintain good control (having tackled any hyperglycaemic coma as above); 10% dextrose (with 10mmol KCl per 500 mL) is infused at 100 mL/h along with an insulin infusion. The insulin infusion rate is either derived from the individual's insulin requirements, or a trial of 3 units per hour is given (Husband, Thai and Alberti 1986). The morbidly obese patient will need a higher insulin rate (e.g. 4 units per hour), and the frail thin person will need less (e.g. 2 units per hour). Monitor the fingerprick plasma glucose hourly initially, aiming for 510 mM, and adjust the insulin infusion appropriately (Table 5.7). Once the patient stabilizes, the frequency of testing may be partly relaxed. The initial descriptions mixed the insulin in the bag of dextrose, but it is more convenient and gives more frequent acceptable blood glucose levels to use a bag of dextrose and a separate insulin pump. Simmons et al (1994) give different regimens for different classes of patient based on a bedside estimate of their insulin requirements; this

Table 5.7 Adjusting the insulin-glucose infusion

Fingerprick glucose level Action

Above target range Within target range Below target range Below 3.0 mM

Increase insulin infusion by 25% Leave insulin infusion at same rate Decrease insulin infusion by 25% Stop insulin infusion, run in 200 mL 10% dextrose over 5min; restart insulin infusion at 50% previous rate is eminently sensible. These infusions are known by many names depending on location.

If the patient has to be nil-by-mouth for an operation or procedure there are several scenarios (Gill and Al-berti 1989). If the patient has a serious problem needing major surgery, then he or she needs resuscitation and an insulin-glucose infusion. If the patient is well controlled (FPG <10mM) on diet, metformin, acarbose or short-acting sulphonylurea, and the procedure is short, the patient can undergo the procedure, omitting breakfast and the morning anti-diabetic medication (i.e. needs to be first on the operating list), and can then have normal breakfast and usual treatment later in the morning. This does mean that these patients have to be on the main hospital site, or have good transport and support if this is being done from home. If the patient is not insulin-requiring, but is going for a prolonged operation, then it would be wise to institute an insulin-glucose infusion and set it up preoperatively. Often these matters are ignored, and the anaesthetist is left to sort it out shortly before the op-eration—which they do extremely well, but it is not best clinical practice.

In insulin-treated patients, an insulin-glucose infusion may be used, except in Type 2 diabetic subjects on short- or intermediate-acting insulins who can tolerate a short delay in insulin and breakfast if monitored.

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