Calcium Channel Blocker Overdose.

Abstract

Audience: Emergency medicine residents and medical students on emergency medicine rotation.

Background: Calcium channel blocker (CCB) overdoses can be severe with potentially serious adverse outcomes. CCBs work by blocking the calcium channels on smooth and cardiac muscle tissue. At low dose ranges, dihydropyridine CCBs (such as nifedipine, amlodipine, and nicardipine) block the L-type calcium receptors in the peripheral vasculature, whereas non-dihydropyridine CCBs (such as: verapamil and diltiazem) affect the L-type calcium receptors in the myocardium.1 Because of this distinction, dihydropyridine CCB toxicity manifests as arterial vasodilation and non-dihydropyridine CCB toxicity is associated with cardiac manifestations such as bradycardia and negative inotropy.2 It is important to note that in high concentrations (such as in overdoses), CCBs lose specificity for their specific receptors and can show all the manifestations of toxicity such as bradycardia, peripheral vasodilation, and hypotension. Patients can develop both vasoplegic shock from peripheral vasodilation and cardiogenic shock. This is a high acuity low occurrence case with infrequently used but specific treatments, and thus this case provides educational value.

Educational objectives: At the end of this oral board session, examinees will: (1) demonstrate ability to evaluate a patient with undifferentiated shock with bradycardia and discuss the differential diagnosis, (2) recognize the signs and symptoms of calcium channel blocker overdose, (3) demonstrate ability to manage treatment of a patient with calcium channel overdose.

Educational methods: This oral board case followed the standard American Board of Emergency Medicine-style case in a tertiary care hospital with access to all specialists and resources needed. This case was tested using 12 resident volunteers ranging from PGY 1-2 in an ACGME (Accreditation Council for Graduate Medical Education) accredited emergency medicine residency program.

Research methods: Immediate feedback was solicited both from the learners and from the evaluators following the debriefing session. Residents were asked to evaluate the educational value of the case using a 1-5 Likert scale (5 being excellent). Evaluators were asked to score the residents using the ACGME core competencies with a scale of 1-8, 1-4 being unacceptable and 5-8 being acceptable.

Results: Seven PGY1 residents and five PGY2 residents, thus twelve residents in total, completed the case. The average score was 5.10/8. Three residents missed zero critical actions. The most common critical action missed was consulting cardiology or cardiothoracic surgery for circulatory support options. Many residents failed to recognize that the patient did not have a perfusing blood pressure at the beginning of the case and did not start CPR. Although most residents recognized the patient's hemodynamic collapse was from a calcium channel blocker overdose, most did not know the treatment for this beyond atropine and intravenous fluids.The learners rated the educational value of the case as 4.9/5. Seven residents reported that the case definitely increased their medical knowledge; five residents reported that it somewhat increased their medical knowledge. All residents rated the case as helpful in preparing to manage this medical condition.

Discussion: The educational content from this case was effective. This is a high acuity low occurrence case that has unique treatments that are not commonly used. This makes this case excellent for practice and discussion. We learned during implementation that this case has a high degree of difficulty compared to other cases, and junior learners will need more prompting. It is also important for the proctor to keep the case moving because there is a lot to cover in the allotted amount of time.

Topics: Calcium channel blocker overdose, toxicology.