ICU Med 101: Nipride (Sodium Nitroprusside)

Introduction

• Purpose: To discuss the drug Nipride (Sodium Nitroprusside) used in ICU settings, especially for heart failure patients.
• Audience: CRNA interview preparation or professional competence.
• Use Location: Primarily in CCUs or CVICUs, not commonly in general ICUs.

Drug Overview

• Name: Nipride or Sodium Nitroprusside.
• Use: Manages hypertension, particularly in acute heart failure patients.
• Mechanism: Vasodilation that decreases systemic vascular resistance (SVR) and reduces afterload and preload.

Mechanism of Action

• Metabolization: Metabolized by hemoglobin to produce four CN- ions.
  • Binds to: methemoglobin, forming cyanmethemoglobin.
  • Cyanide Production: Broken down into cyanide, which the body can process unless levels are too high.
• Binding: Binds reversibly with ferric ions.
  • Iron States: Ferric (Fe3+) vs. Ferrous (Fe2+) ions, with ferrous being preferable for oxygen transport.
• Biochemical Process:
  • Releases nitric oxide.
  • Activates guanylate cyclase, leading to conversion of GTP to cGMP.
  • Activates protein kinase G, decreasing intracellular calcium.
  • Result: Hyperpolarization, preventing muscle contraction, leading to vasodilation.
• Calcium and Myosin: Decrease in calcium causes dephosphorylation of myosin fibers, preventing muscle constriction.

Nursing Considerations

• Monitor for Hypotension: Maintain MAP as per cardiac ICU standards.
  • Maps: Cardiac ICUs focus on MAP rather than systolic numbers.
• Watch for Bradycardia.
• Cyanide Toxicity: Monitor cyanide levels.
• Increased ICP: Avoid in neuro ICUs unless for heart failure patients.
• Methemoglobinemia: When hemoglobin iron is oxidized to ferric state (Fe3+), preventing effective oxygen transport.
  • Diagnosis: Normal PO2 but low pulse oximetry due to perfusion issues.

Examination Tips

• Key Knowledge for Interviews: Nipride activates protein kinase G, reduces intracellular calcium, and causes vasodilation.
• Depth of Knowledge: Deeper understanding of mechanisms may not be required but beneficial.

Conclusion

• Summary: Understanding of Nipride is crucial for ICU settings, especially for heart failure management.
• Future Learning: Additional resources and formal education can enhance comprehension and confidence.