BASAL insulin
Longer-acting insulins (e.g., glargine, detemir, and NPH) which provide a constant supply of “background” insulin, regardless of meals. All patients with type 1 diabetes require this and many with type 2 diabetes need this, especially in the perioperative period
BOLUS (prandial/mealtime) insulin
The fixed dose (or altered dose for larger or smaller meals) of rapid-acting insulin (e.g., lispro, aspart, glulisine, or regular) which is given before a meal to mimic the body’s normal response to a caloric load
CORRECTION insulin (replaces the older term “sliding scale”)
The variable amount of rapid-acting insulin given in addition to the prandial and/or basal insulin to correct hyperglycemia. Correction insulin can also be given at bedtime although it is reasonable to be more conservative at this time due to the greater risk of nocturnal hypoglycemia
Preoperative Evaluation
Note the duration of the diabetes, the presence of complications (especially kidney disease), current management, and quality of glycemic control. An elevated HbA1c has been associated with worse surgical outcomes in observational and small prospective trials [11]; however, evidence to validate its use as a predictor of outcomes is lacking. Bariatric patients, for example, may only be able to achieve good glycemic control after surgery, so denying them surgery on the basis of an elevated HbA1c may not be optimal management. (Note: The HbA1c may be inaccurate due to end-stage renal disease, erythropoietin therapy, acute anemia, RBC transfusions, hemoglobinopathies, microhemolysis from heart valve replacement, increased RBC mass from testosterone therapy, HIV/AIDS, etc. [12]).
Perioperative Management
For Procedures that Require a Restricted Caloric Intake
For outpatient procedures, patients usually can resume home insulin, oral diabetes medication, and non-insulin injectable medication after the procedure, if they are eating. The following is applicable for patients who are to be NPO at midnight and are likely to have decreased caloric intake postoperatively:
Hold bolus insulin the morning of surgery. Continue basal insulin the night before and the morning of surgery, but reduce the dose per Table 13.2.
Table 13.2
Preoperative insulin recommendations
Basal insulin
NPH (has a peak, thus provides some prandial coverage)
75 % of the usual evening dose the night before surgery (no less than 80 % for type 1 DM)
50 % of the usual AM dose (if applicable) on the morning of surgery (80 % for type 1 DM)
Glargine
Take 50–75 % of the usual evening dose (50 % if the patient takes more than 50 units, no less than 80 % for type 1 DM)
Detemir
Take 50–75 % of the usual morning dose (50 % if the patient takes more than 50 units normally but no less than 80 % for type 1 DM)
Premixed insulin (NPH/regular 70/30, Humalog® 75/25 or 50/50 mix, NovoLog® 70/30 mix)
Take 75 % of the usual evening dose (80 % type 1)
Take 50 % of the usual morning dose (80 % type 1)
Insulin pump
In general, continue basal rate, then switch to D5NS and an insulin infusion just prior to surgery, and disconnect the pump. Continue IV insulin until tolerating an adequate diet, and then resume the SC pump if the patient is stable, alert, and able to manage the pump. Endocrinology consultation should be considered
Bolus/prandial (mealtime) insulin
Short-acting insulin
Do not take on the morning of surgery with the exception of correction algorithms for hyperglycemia using rapid-acting analogues—lispro, aspart, or glulisine
Note: Do not use regular insulin (U-100 and U-500) for correction due to prolonged duration of effect
No oral hypoglycemic or non-insulin injectable meds the morning of surgery.
In the recovery room/postanesthesia care unit, review the hyperglycemia plan for adequate insulin orders (see below for detailed recommendations).
American Diabetes Association/American Association of Clinical Endocrinologists (ADA/AACE) guidelines recommend managing non-insulin-requiring type 2 patients with insulin and not resuming oral diabetes medication and non-insulin injectable medication until the patient is ready to go home [6].
If the patient has an insulin pump or continuous glucose monitor, consider recommending an endocrinology consultation.
Using an Institutional Infusion Protocol and Transitioning to SC Insulin
Start protocol when the patient presents to the preoperative holding area.
Continue the insulin infusion until the patient is likely to be eating ~50 % of meals and has a reasonably stable blood sugar on the insulin infusion (see Table 13.3 to calculate the dose).
Table 13.3
Transitioning from IV to SC insulin: calculating the dose
Guidelines
– The subcutaneous (SC) dose is only 60–80 % of the IV dose
– Post-op insulin requirements also tend to go down with time, so a reasonable plan is to calculate the amount of insulin given via infusion over the last 16 h to give you the estimated 24-h subcutaneous insulin requirement. Thus, the last 16-h total IV dose = next 24-h total SC dose
– Next, divide the 24-h SC dose into basal and prandial/premeal bolusa,b:
~ 50 % of the estimated requirement is given as basal glargine, usually at bedtime, or NPH or detemir BID
~ 50 % of the estimated requirement is given as lispro, aspart, or glulisine as three equally divided mealtime (prandial) doses
Example
Your patient has required 3 units of insulin IV per hour for the last 16 h
1. Calculate SC dose: 3 × 16 = 48 units total SC dose
2. Divide into basal and prandial:
– Basal: ½ × 48 = 24 units of basal insulin (e.g., glargine qhs)
– Prandial: ½ × 48 = 24 units of prandial insulin (e.g., lispro, aspart, or glulisine) divided before each meal. Thus, 24 units/3 = 8 units before each meal (if isocaloric)
If the patient normally takes basal insulin (e.g., glargine) in the morning, give the basal and bolus insulin before breakfast and stop the insulin infusion.
If the patient normally takes basal insulin (e.g., glargine) at night and is starting to eat in the morning, give a one-time dose of NPH (roughly half the dose of the planned evening glargine) in the morning along with the short-acting bolus to serve as a bridge to the first glargine dose that evening.
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