Author: Fernando F. Cuadrado, MD and Matthew Monteleone, MD - Cincinnati Children’s Hospital Medical Center
A seven-year-old boy with a history of orthotopic heart transplantation is undergoing cardiac catheterization and biopsy under general endotracheal anesthesia. He is erroneously administered a 15 mcg/kg bolus dose of dexmedetomidine due to an infusion pump programming error. The heart rate immediately decreases to 67 bpm with a blood pressure of 72/43. Which of the following side effects is MOST likely to be observed in this patient?
EXPLANATION
Dexmedetomidine is a highly selective alpha2 adrenergic receptor agonist that induces sedation, anxiolysis, and analgesia by inhibiting norepinephrine release, thereby reducing sympathetic tone and promoting sedation without respiratory depression. In pediatric anesthesia, it is frequently used for postoperative sedation, particularly following cardiac catheterization. Dexmedetomidine is preferred in this setting because it provides sedation with stable hemodynamics and minimal to no respiratory depression, making it an ideal choice for children with cardiac conditions.
The most common side effects include hypotension, bradycardia, and, less frequently, hypertension, which typically occurs shortly after rapid bolus administration. The hypotensive effects are mediated via stimulation of central alpha2A receptors, resulting in decreased catecholamine release and sympathetic outflow from the locus ceruleus of the brainstem. In heart transplant patients, the bradycardic effects may be diminished due to cardiac denervation, though hypotension and hypertension can still occur. While these side effects are well-documented, less common adverse events such as hypoglycemia and miosis may arise, particularly with high doses or prolonged high-dose infusions. In a 2009 case report, a 20 month-old, 11kg patient was accidentally administered 36 mcg/kg of dexmedetomidine over 36 minutes. A blood glucose check prompted by several shaking episodes in the recovery unit was 26 mg/dL. The authors speculate that the hypoglycemia was due to the drug’s sympatholytic effects of reducing circulating norepinephrine levels with a reduction in gluconeogenesis and glycogenolysis. Additionally, a decrease in serum cortisol levels may blunt the stress response induced by surgery, further affecting glucose homeostasis. In another case report, a 3-year-old, 11 kg child was accidentally given 100 mcg of dexmedetomidine as a bolus. The child presented with significant bradycardia, hypotension, bradypnea, deep hypnosis, and miosis, requiring treatment with an epinephrine infusion. Although this patient’s glucose remained normal, the authors speculate that this may have been due to the epinephrine counteracting the sympatholytic effects of dexmedetomidine. In summary, when there is concern about oversedation, blood glucose levels should be closely monitored because of the increased risk of hypoglycemia with the administration of high-dose dexmedetomidine.
The correct answer is B, hypoglycemia. Dexmedetomidine offers effective sedation with a favorable safety profile in pediatric patients, particularly after cardiac procedures. However, there is a potential for hypoglycemia with higher-than-usual clinical doses. Notably, dexmedetomidine does not cause hyperglycemia. Additionally, xerostomia, rather than sialorrhea, is a common side effect due to reduced salivary gland activity. Finally, dexmedetomidine produces pupillary constriction in awake volunteers, possibly due to absent inhibition of the pupilloconstrictor nucleus and reduced sympathetic tone of the iris muscles.
REFERENCES
Bernard PA, Makin CE, Werner HA. Hypoglycemia associated with dexmedetomidine overdose in a child? J Clin Anesth. 2009; 21:50–53.
Görges M, Poznikoff AK, West NC, Brodie SM, Brant RF, Whyte SD. Effects of Dexmedetomidine on Blood Glucose and Serum Potassium Levels in Children Undergoing General Anesthesia: A Secondary Analysis of Safety Endpoints During a Randomized Controlled Trial. Anesth Analg. 2019;129:1093-1099
Nath SS, Singh S, Pawar ST. Dexmedetomidine overdosage: An unusual presentation. Indian J Anaesth 2013; 57(3):289-291.
Jooste EH, Muhley WT, Ibinson JW, et al. Acute hemodynamic changes after rapid intravenous bolus dosing of dexmedetomidine in pediatric heart transplant patients undergoing routine cardiac catheterization. Anesth Analg. 2010;111(6):1490-1496.
