Critical Care Medicine-Neurologic Disorders>>>>>Arrhythmias and Pacemaker
Question 3#

A 51-year-old male underwent an uncomplicated triple-vessel coronary artery bypass grafting 4 weeks ago and now presents to the emergency department with chest pain, a friction rub on auscultation, and diffuse ST-segment elevations on ECG. While blood samples are drawn for analysis, the patient states that he “feels lightheaded”. A noninvasive blood pressure obtained is recorded to be 62/36 mm Hg. An ECG reveals a heart rate of 33/min with narrow complex QRS complexes. The patient is quickly given three boluses of 1 mg atropine IV with no response in heart rate.

While you are waiting for the transcutaneous pacing (TCP) equipment to arrive, which of the following interventions is MOST appropriate?

A. Administer more atropine
B. Administer norepinephrine
C. Administer dopamine
D. Administer dobutamine
E. Administer isoproterenol

Correct Answer is C

Comment:

Correct Answer: C

Atropine is an anticholinergic, which is a muscarinic acetylcholine receptor antagonist. The Advanced Cardiovascular Life Support guidelines suggest a maximum dose of up to 3 milligram in the setting of symptomatic sinus bradycardia. If atropine does not yield a sufficient heart rate increase, TCP is recommended. Should TCP not be available or require time to be obtained, it is reasonable to start either an epinephrine or dopamine infusion. Norepinephrine has a nonlinear effect on heart rate; at lower doses, norepinephrine may cause reflex bradycardia, whereas at higher doses, it causes an increase in heart rate. Dobutamine and isoproterenol are strong chronotropes. Because of their isolated beta activities, their administration is associated with hypotension due to vasodilation, which would be deleterious in this patient. Dopamine and epinephrine are the preferred chronotropes should atropine fail and TCP not be immediately available. Although isoproterenol is a possible third alternative chronotrope, the known hypotensive effects are of particular concern in this patient. 

References:

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