What is the proper management for a patient with an inferior myocardial infarction (MI) who was mistakenly given nitroglycerin, including the appropriate amount of intravenous (IV) fluid bolus to administer?

Management of Nitroglycerin-Induced Hypotension in Inferior MI

For a patient with inferior MI (II, III, aVF) who was mistakenly given nitroglycerin and developed hypotension, immediately administer a rapid IV fluid bolus of 500-1000 mL of normal saline while elevating the patient's legs and discontinuing the nitroglycerin. 1, 2

Immediate Management Steps

1. Discontinue nitroglycerin immediately 1
2. Position the patient supine with legs elevated to improve venous return 1, 2
3. Administer rapid IV fluid bolus of 500-1000 mL normal saline 2
   • Start with 500 mL and reassess
   • May require additional fluid depending on response and patient's cardiac status
4. Monitor vital signs continuously including blood pressure, heart rate, oxygen saturation, and ECG 1

Additional Interventions if Hypotension Persists

• If bradycardia is present, consider atropine administration 3, 1
• Continue fluid resuscitation as needed, but monitor carefully for signs of volume overload, especially in patients with heart failure 2
• Avoid epinephrine or other arterial vasoconstrictors as they may do more harm than good 2

Rationale and Pathophysiology

Patients with inferior MI frequently have right ventricular (RV) involvement (up to 60% of cases) 4. These patients are particularly sensitive to nitroglycerin because:

• RV infarction makes patients preload-dependent to maintain cardiac output 3, 1
• Nitroglycerin causes venodilation, reducing preload and potentially causing profound hypotension 3
• A study showed that 15 of 20 patients with inferior MI who developed marked hypotension after nitrate administration had evidence of RV involvement 4

Monitoring and Follow-up

• Continuously monitor blood pressure, heart rate, and oxygen saturation
• Obtain a right-sided ECG if not already done to assess for RV involvement
• Consider hemodynamic monitoring in patients with refractory hypotension or heart failure 2
• Watch for signs of methemoglobinemia (rare complication of nitrate overdose) including chocolate-brown blood and signs of impaired oxygen delivery despite adequate cardiac output 2

Cautions and Pitfalls

• Avoid excessive fluid administration in patients with left ventricular failure or pulmonary edema
• Do not use epinephrine or arterial vasoconstrictors as first-line treatment for nitrate-induced hypotension 2
• Be aware that in patients with renal disease or congestive heart failure, central volume expansion requires careful monitoring 2
• Recognize that computer interpretation of inferior STEMI alone cannot predict which patients will develop hypotension following nitroglycerin 5

The management of nitroglycerin-induced hypotension in inferior MI focuses on restoring preload through fluid administration and positioning, while avoiding interventions that could worsen the patient's condition.