What is the glucose insulin potassium (GIK) protocol?

Glucose-Insulin-Potassium (GIK) Protocol

The glucose-insulin-potassium (GIK) protocol is not recommended for routine use in acute myocardial infarction as recent clinical trials have shown no significant benefit in ST-elevation myocardial infarction (STEMI). 1

Definition and Composition

The GIK protocol involves intravenous administration of a solution containing:

• Glucose (typically 10-25%)
• Insulin (20-50 units)
• Potassium (80 mEq/L)

This solution is typically administered as an infusion over 24 hours at rates of approximately 1-1.5 mL/kg/hour.

Historical Context and Mechanism

GIK therapy was first proposed by Sodi-Pallares in the 1960s as a metabolic modulator for myocardial protection. The theoretical benefits include:

• Promotion of glucose utilization as an energy substrate during ischemia
• Reduction of free fatty acid levels
• Stabilization of cell membranes
• Reduction of myocardial acidosis
• Decreased ventricular arrhythmias
• Improved myocardial function

Evidence and Recommendations

Acute Myocardial Infarction

• Current Status: Class IIb, Level of Evidence C (weak recommendation) 1
• The American Heart Association guidelines explicitly state that "GIK did not show any benefit in STEMI" and "there is little evidence to suggest that this intervention is helpful" 1
• Early small studies showed promise, but larger trials have been disappointing:
  • The Pol-GIK trial found low-dose GIK ineffective in acute MI 2
  • The Glucose-Insulin-Potassium Study found no significant mortality reduction in all patients undergoing primary angioplasty for acute MI, though a subgroup of patients without heart failure showed some benefit 3

Cardiac Surgery

• Mixed results have been reported:
  • A meta-analysis of 33 RCTs showed GIK was associated with fewer perioperative MIs, less inotropic support requirements, and better cardiac index in patients undergoing cardiac surgery 4
  • However, benefits appear to be limited to specific patient populations, particularly diabetic patients with glycemic control 4
  • In off-pump coronary artery bypass surgery, GIK showed no demonstrable benefit and caused insulin-resistant hyperglycemia 5

Blood Glucose Management

• Rather than using GIK, current guidelines focus on appropriate glycemic control:
  • Target blood glucose of 140-180 mg/dL for critically ill patients 1, 6
  • Avoid aggressive correction that can cause fluid shifts and electrolyte abnormalities 6
  • Initiate insulin therapy when blood glucose is ≥180 mg/dL 6

Important Considerations and Pitfalls

1. Hyperglycemia Risk: GIK infusions can cause significant hyperglycemia, which is associated with worse outcomes in acute cardiovascular conditions 1

2. Monitoring Requirements: If GIK is used, frequent blood glucose monitoring is essential (every 1-2 hours initially) 6

3. Electrolyte Disturbances: Potassium levels must be closely monitored to prevent hypokalemia or hyperkalemia

4. Patient Selection: Evidence suggests GIK may be harmful in patients with heart failure (Killip class ≥2) 3

5. Alternative Approaches: Modern management focuses on direct reperfusion strategies (PCI, thrombolytics) and evidence-based pharmacotherapy rather than metabolic modulation

In summary, while GIK was once thought promising for myocardial protection, current evidence does not support its routine use in acute myocardial infarction. Specific applications in cardiac surgery may be considered in selected patients, particularly when combined with appropriate glycemic control.