Insulin (Humulin, Novolin, Lantus, Humalog, Novalog, Levemire, Tresiba)

Hypoglycemia risk - the primary perioperative danger; glucose monitoring every 30–60 min intraoperatively is standard practice, especially with insulin infusions or in NPO patients who received their usual dose. Symptoms (diaphoresis, tachycardia, confusion) may be masked by general anesthesia — rely on glucose monitoring, not clinical signs.

Formulation matters - regular insulin (Humulin R, Novolin R) is the only formulation suitable for IV infusion; all other formulations are subcutaneous only.

Tight glycemic control target - most perioperative guidelines recommend maintaining glucose 140–180 mg/dL intraoperatively; aggressive control below 110 mg/dL increases hypoglycemia risk without proven benefit.

Stress response - surgical stress, catecholamine release, and corticosteroid use all drive hyperglycemia intraoperatively — anticipate higher insulin requirements.

Hypokalemia concern - insulin drives K+ intracellularly; monitor potassium closely during infusions, particularly in patients receiving insulin-glucose-potassium solutions or those already prone to hypokalemia.

Hold long-acting insulin strategically - patients on basal insulin (glargine, detemir, degludec) should typically receive 50–80% of their usual dose the night before surgery; consult endocrinology for complex cases.

Rapid-acting insulin and NPO status - short- and rapid-acting insulin should generally be withheld when the patient is NPO — administration without a carbohydrate source creates immediate hypoglycemia risk.

Renal & Liver Patients - Renal impairment significantly prolongs insulin action and increases hypoglycemia risk — reduce doses and increase monitoring frequency in patients with CKD or AKI

Insulin-glucose infusion timing - for IV regular insulin infusions, glucose checks should be completed before initiation and rechecked within 30 minutes of any rate change.

Perioperative insulin protocols - most institutions use standardized insulin infusion protocols; always defer to your facility's protocol and involve endocrinology/pharmacy for complex insulin-dependent diabetic patients.

Insulin pump (CSII) patients - Institutions typically have protocols for either continuing the pump at a reduced basal rate or transitioning to IV infusion — confirm your institutional approach preoperatively.

Drug Interactions - Beta-blockers mask tachycardia (a warning sign of hypoglycemia) and may prolong hypoglycemic episodes by inhibiting glycogenolysis; Corticosteroids antagonize insulin action and cause significant hyperglycemia; insulin requirements increase substantially — often require insulin infusion in previously diet-controlled patients. Sympathomimetics like epinephrine and vasopressors raise blood glucose via glycogenolysis and gluconeogenesis, which may require insulin adjustment; Somatostatin analogs (eg octreotide) may inhibit glucagon release, potentially blunting the counterregulatory response to hypoglycemia.

Documentation - document all insulin formulations, doses, and timing in the anesthesia record; intraoperative glucose values and interventions must be recorded to guide postoperative management

Absolute - Hypoglycemia (active)

Relative - Hypokalemia (insulin will worsen K+ depletion), renal failure with erratic glucose metabolism

Caution - Hepatic impairment (reduced gluconeogenesis, altered insulin clearance), NPO status without glucose supplementation, concurrent beta-blocker therapy, elderly patients, patients with adrenal or pituitary insufficiency

Treatment of hyperglycemia: 0.1 units/kg regular insulin. Reassess BG in 30-60 min

Treatment of hyperkalemia: 10 units regular insulin with 25-50 g dextrose (D50W); Onset of K+ lowering is 15-30 min. Duration is ~2-6 hrs.

Perioperative glucose control: Start at 0.5–2 units/hour & titrate based on BG level. Target 140-180 mg/dL.

Binding the insulin receptor (tyrosine kinase receptor) on muscle, adipose, and hepatic cells activates receptor autophosphorylation → phosphorylation of IRS-1/IRS-2 → PI3K/Akt signaling cascade → GLUT4 translocation to cell membrane (muscle, fat), glycogen synthesis (liver, muscle), suppression of gluconeogenesis and glycogenolysis (liver), inhibition of hormone-sensitive lipase (fat)

Liver (~50%), kidney (~30%), and peripheral tissues

Hypoglycemia Reversal

Dextrose — first line for symptomatic hypoglycemia; 25–50 g (50–100 mL of D50W) IV bolus; repeat as needed. Onset is 2–5 min, duration is 15–30 min. Titrate to glucose > 70 mg/dL. May require dextrose infusion (D10W) for prolonged hypoglycemia from long-acting insulin. Dextrose boluses may cause rebound hyperglycemia, so monitor closely.

Glucagon IM/SQ/IN — second line when IV access unavailable. 1 mg (adult); onset 10–20 min, duration 60–90 min. Requires intact glycogen stores — unreliable in patients with depleted glycogen stores (prolonged NPO, hepatic disease, alcohol use).

SQ Rapid Acting (lispro, aspart, glulisine): Typically 0.05 - 1 units/kg per meal. Hold when NPO

SQ Regular: Per sliding scale. Onset slower than rapid acting (30-60 min) Not preferred for perioperative management

SQ Basal (glargine, detemir, degludec): Reduce 20-50% evening prior to surgery. Resume postoperatively when eating.