In an adult surgical patient with intra‑operative hyperglycaemia who develops tachycardia during the case and after extubation, how should the hyperglycaemia and tachycardia be managed?

Management of Intraoperative Hyperglycemia with Tachycardia

Initiate continuous intravenous insulin infusion immediately, targeting blood glucose 90-180 mg/dL (5-10 mmol/L), as this directly addresses both the hyperglycemia and its cardiovascular manifestations including tachycardia. 1

Immediate Interventions

Glycemic Control

• Start IV insulin infusion without delay for any patient with intraoperative glucose >180 mg/dL (10 mmol/L), regardless of diabetic status, using ultra-rapid short-acting insulin analogues diluted to 1 IU/mL concentration 1, 2
• Target blood glucose between 90-180 mg/dL (5-10 mmol/L) to reduce perioperative morbidity and mortality while avoiding hypoglycemia risk 1, 3
• Provide simultaneous glucose infusion (equivalent to 4 g/hour) along with insulin to prevent hypoglycemia, except during active hyperglycemia 2, 3

Addressing the Tachycardia

The tachycardia in this scenario is likely multifactorial, driven by:

• Sympathoadrenal activation from hyperglycemia itself, which triggers catecholamine release and can cause cardiac arrhythmias 4, 3
• Stress hormone response (glucagon, cortisol, catecholamines) from surgical stress, which both worsens hyperglycemia and increases heart rate 3
• Potential hypokalemia induced by insulin therapy, which can precipitate arrhythmias 3, 2

The primary treatment is correcting the hyperglycemia with IV insulin, as this addresses the root cause of the sympathoadrenal activation 1, 4

Critical Monitoring Requirements

Glucose Monitoring

• Check blood glucose every 1-2 hours during active insulin infusion 3, 5
• If glucose exceeds 300 mg/dL (16.5 mmol/L), immediately check for ketosis 1, 5
• For severe hyperglycemia >300 mg/dL without ketosis, give 6 units rapid-acting insulin IV bolus, increase infusion rate, and ensure adequate hydration 1, 2

Electrolyte Monitoring

• Check serum potassium every 4 hours during IV insulin infusion, as insulin drives potassium intracellularly and can precipitate dangerous hypokalemia 3, 2
• Hypokalemia is a critical cause of cardiac arrhythmias and tachycardia in this setting 6
• Measure serum electrolytes urgently if glucose >300 mg/dL to assess for hyperosmolar state 5, 2

Cardiac Monitoring

• Continue ECG monitoring throughout the case and after extubation, as hyperglycemia-induced arrhythmias include premature ventricular contractions, ventricular tachycardia, and heart block 4, 6
• The tachycardia should improve as glucose normalizes; persistent tachycardia despite glycemic control warrants investigation of other causes 4

Fluid Management

• Use 0.9% normal saline as primary IV fluid to ensure adequate hydration 5, 2
• Adequate hydration is essential as it helps correct hyperglycemia and supports cardiovascular stability 1, 2
• Dehydration worsens hyperglycemia and can contribute to tachycardia 5

Critical Pitfalls to Avoid

Avoid Overly Aggressive Targets

• Do not target normoglycemia (<90 mg/dL or 5 mmol/L), as this significantly increases hypoglycemia risk without additional benefit 1, 3
• Moderate glycemic control (90-180 mg/dL) provides optimal benefit-to-risk ratio, reducing morbidity and mortality without increasing hypoglycemia 3

Hypoglycemia Recognition

• Severe hypoglycemia itself can cause lethal cardiac arrhythmias and tachycardia through sympathoadrenal activation 4
• Administer glucose immediately if blood glucose drops <60 mg/dL, even without symptoms 5, 2
• Intraoperative patients cannot report hypoglycemic symptoms, making frequent monitoring essential 5

Never Stop Insulin Abruptly

• Do not stop IV insulin until the patient is eating and subcutaneous insulin has been administered 1, 2
• Abrupt cessation causes dangerous rebound hyperglycemia and potential ketoacidosis 2

Prognostic Context

Understanding why this matters for patient outcomes:

• Perioperative hyperglycemia >180 mg/dL (10 mmol/L) increases mortality and morbidity in both diabetic and non-diabetic patients, with a 7-fold higher risk of postoperative complications when glucose exceeds 200 mg/dL (11 mmol/L) 3
• Each 0.2 g/L (1.1 mmol/L) increase in glucose above 100 mg/dL (5.5 mmol/L) increases postoperative complications by 34% 3
• Controlling hyperglycemia reduces infections, improves wound healing, decreases ICU length of stay, and reduces cardiac mortality 3
• The cardiovascular effects of hyperglycemia include endothelial dysfunction, abolished ischemic preconditioning, and increased free fatty acid release that is harmful to the myocardium 3

Post-Extubation Management

• Continue IV insulin infusion and frequent glucose monitoring (every 1-2 hours) in the immediate post-extubation period 5
• Maintain the same glycemic target of 90-180 mg/dL (5-10 mmol/L) 1, 5
• When transitioning to subcutaneous insulin, calculate total 24-hour IV insulin dose and give half as long-acting basal insulin subcutaneously, stopping IV insulin only after subcutaneous dose is administered 1, 2