Beta blocker overdose

Sinus bradycardia with HR of 50

A 70 yo female presents with lightheadedness and feeling "crummy."  She was started on metoprolol yesterday by her PCP for an elevated heart rate.  Initial vital signs reveal HR of 31, BP 121/85, RR of 15, and T 37.  She had been having intermittent burning substernal chest pain but denies any currently.  On physical exam she is awake and alert but looks pale and uncomfortable.  Pupils are PERRL, CV exam reveals bradycardia with regular rhythm, there is no respiratory distress, lungs are clear to auscultation bilaterally, abdomen is soft and nondistended, neuro exam is intact.  Skin is warm and dry.  EKG shows sinus bradycardia with T wave inversions in leads II, III, and aVF.

The differential for bradycardia is broad and includes vasovagal response, sick sinus syndrome, myocardia ischemia involving right coronary artery, atrioventricular block, increased intracranial pressure (seen with elevated BP in Cushing's reflex), hypokalemia, hypothermia, hypothyroidism, and medications (beta blockers, calcium channel blockers, digoxin, clonidine).  Bradycardia can also be a normal finding, often seen in well-conditioned athletes.

The key branch point for management of bradycardia is whether or not signs of adequate perfusion are present.  If the bradycardia is leading to hypoperfusion, according to ACLS guidelines, transcutaneous pacing should be initiated while reversible causes (H's and T's) are investigated.  If the bradycardia is not causing hemodynamic compromise, patients can be monitored and observed.

While transcutaneous pacing is being set up, atropine 0.5 mg IV push should be given (repeat for total dose of 3 mg).  Dopamine is a second-line agent for when atropine is not effective.  Dose is 2-10 mcg/kg/min infusion.  Epinephrine is a third-line agent, dose 2-10 mcg/min infusion.  If beta blocker overdose is suspected, glucagon 1-5 mg IV should be given.  If heart rate responds, a glucagon infusion should be started.

Pacer pads were placed on the patient, but because she was maintaing her blood pressure and mentating well, transcutaneous pacing was not required.  She was given a fluid bolus as well as atropine 0.5 mg IV x 2 doses without improvement.  Because beta blocker overdose was a consideration, she was given glucagon 3.5 mg IV.  Because of possible ischemic changes on EKG, an aspirin was administered and cardiology was consulted.