(163) Dexmedetomidine and Complete Heart Block

Introduction: Dexmedetomidine produces anxiolysis and calming effect, resembling physiological sleep with minimal respiratory depression and narcosis.  Due to its desirable pharmacological effects and a good safety profile, it has been widely used in surgeries and intensive care units. However, several cardiovascular side effects have been reported. We present a rare case of dexmedetomidine induced complete heart block, which resolved once the medication was discontinued.

Description: The patient is a 91-year-old male, who was admitted to the intensive care unit (ICU) for sepsis, urinary tract infection and acute kidney injury. In the ICU, he was treated with intravenous fluids, broad spectrum antibiotics, and vasopressors support. Dexmedetomidine infusion was initiated for agitation.  Dexmedetomidine was infused at 0.5 mcg/kg/hr. Shortly thereafter, his heart rate dropped from 80 beats per minute to the 50s, 40s and as low as 30 beats per minute.  On telemetry, the patient developed a complete heart block for one minute. The dexmedetomidine drip was stopped and his heart rate started to rise gradually to 80-90 beats per minute and the rhythm was back to the baseline first-degree heart block. However, the patient’s overall clinical status remained guarded due to the underlying co-morbidities including worsening kidney function requiring dialysis, poor mental status, and general debility. The patient was discharged home on hospice after six days.

Discussion: Dexmedetomidine has been associated with various cardiovascular effects including hypotension and sinus bradycardia, especially in higher doses. The bradycardia usually resolves when the dosage is decreased or the medication is stopped. There may be a higher risk of arrhythmia in patients with renal impairment, as a high proportion of the medication is excreted through the kidneys. Clinicians should be cognizant of various cardiovascular side effects such as bradycardia and heart block. Most of the cardiovascular effects are dose dependent and resolve with discontinuation of the medication and may be reversible when the medication is stopped. Although bradycardia is reported commonly, complete heart blocks were rarely reported.