What is the recommended administration of adrenaline (epinephrine) in an adult patient with myocardial infarction and severe hypotension?

Administration of Adrenaline in Myocardial Infarction with Severe Hypotension

Adrenaline should be administered as a continuous intravenous infusion at 0.1–0.5 mcg/kg/min (7–35 mcg/min in a 70-kg adult) for severe hypotension (systolic BP <70 mm Hg) complicating myocardial infarction, preferably through a central venous line, with careful titration to maintain adequate perfusion while minimizing myocardial oxygen demand. 1

Preparation and Route of Administration

• Prepare the infusion by diluting 1 mg (1 mL) of 1:1000 epinephrine in 250 mL of D5W to yield a concentration of 4 mcg/mL 1
• Administer through a central venous line whenever possible, as peripheral extravasation can cause tissue necrosis 1
• If extravasation occurs, infiltrate 5-10 mg of phentolamine diluted in 10-15 mL of saline into the affected site immediately 1
• Intravenous administration is strongly preferred over peripheral routes in MI patients with cardiac arrest, as central IV and intracoronary routes achieve higher rates of return of spontaneous circulation compared to peripheral IV (OR = 0.14 for peripheral IV, p < 0.0001) 2

Dosing Strategy

• Start at 0.1 mcg/kg/min and titrate upward in increments of 0.05-0.2 mcg/kg/min every 10-15 minutes to achieve target mean arterial pressure 1, 3
• The typical dosing range is 0.1–0.5 mcg/kg/min, which translates to 7–35 mcg/min in a 70-kg adult 1
• Using an infusion pump, administer at an initial rate of 30-100 mL/h (5-15 mcg/min) and titrate based on clinical response 1
• Do not use high-dose epinephrine (>1 mg boluses), as this is not recommended for routine use and offers no mortality benefit 1

Hemodynamic Monitoring Requirements

• Establish continuous arterial blood pressure monitoring via arterial line in all patients receiving epinephrine for severe hypotension 1
• Consider pulmonary artery catheter placement to guide therapy when hypotension does not respond rapidly to initial interventions 1, 4
• Monitor continuously for arrhythmias with cardiac telemetry, as epinephrine's β-adrenergic effects can be proarrhythmic 1
• Measure blood pressure and pulse every minute during titration when continuous monitoring is unavailable 1

Special Considerations for MI Patients

Right Ventricular Infarction

• In inferior MI with suspected right ventricular involvement, prioritize aggressive volume loading with normal saline before initiating epinephrine 4, 5
• Look for the clinical triad of hypotension, clear lung fields, and elevated jugular venous pressure 4, 5
• If cardiac output remains inadequate after volume optimization, add dobutamine rather than epinephrine as first-line inotropic support 4, 5

Myocardial Oxygen Demand

• Use epinephrine cautiously in ischemic heart disease, as it increases myocardial oxygen requirements through β-adrenergic stimulation 1
• Physiological concentrations of epinephrine (30 ng/kg/min) can precipitate myocardial ischemia, ST-segment depression, angina, and ventricular arrhythmias in patients with stable coronary disease 6
• Titrate to the lowest effective dose that maintains adequate perfusion (systolic BP >90 mm Hg) 1

Weaning Strategy

• After hemodynamic stabilization, wean incrementally by decreasing doses every 30 minutes over a 12-24 hour period 3
• Do not discontinue abruptly, as this may precipitate rebound hypotension 3

Critical Pitfalls to Avoid

• Never administer epinephrine as the sole vasopressor without first ensuring adequate intravascular volume, particularly in inferior MI with potential RV involvement 4, 5
• Avoid administering epinephrine to patients in frank cardiac failure or low output states without mechanical circulatory support consideration, as increased afterload may worsen cardiac function 1, 7
• Do not use epinephrine in patients who are relatively hypovolemic, as it is relatively contraindicated in this setting 1
• Have emergency resuscitation equipment immediately available, including defibrillator, atropine, lidocaine, and pacing capability, as epinephrine can precipitate life-threatening arrhythmias 1, 4
• Recognize that epinephrine administration during cardiac arrest improves return of spontaneous circulation but may not provide meaningful neurological recovery 8

Alternative Vasopressor Considerations

• Consider norepinephrine (0.1-0.5 mcg/kg/min) as an alternative for severe hypotension with low total peripheral resistance, though it also requires cautious use in ischemic heart disease 1
• Dopamine (5-10 mcg/kg/min) may be preferred if hypotension is associated with symptomatic bradycardia 1
• For cardiogenic shock refractory to pharmacologic therapy, consider intra-aortic balloon pump placement 1, 5, 7