Supraventricular Tachycardia Associated With Ondansetron

Dear editor,

We present a case of supraventricular tachycardia after ondansetron administration for postoperative nausea treatment.

A 41-year-old woman, weighted 51 kg and 167 cm high, presented to the OR for an elective laparotomy for ovarian cyst removal.

Her prior medical history included hypothyroidism on medication, well managed, according to laboratory testing and lack of relevant symptoms during physical examination. The patient mentioned no other condition or drug use.

Induction and maintenance of anesthesia were unremarkable. The procedure lasted for 2 hours and was uneventful, without significant blood loss. Vital signs and blood gas results were within normal limits throughout the operation. The patient recovered well form anesthesia and was transferred to PACU for postoperative monitoring.

During the first hour in PACU, the patient additionally received incrementally 4 mg of morphine i.v., due to reported pain. Her vitals were steady, with a BP around 110/70 mm Hg and a heart rate 65 to 75 bpm. Soon after, she complained of nausea, and a slow bolus of ondansetron 4 mg was administered. Two minutes later, the patient developed a narrow-complex tachycardia (160-180 bpm). An esmolol drip was started, while obtaining a 12 lead ECG, and the on-call cardiologist was informed. The patient was administrated adenosine 6 mg i.v., following by 2 more boluses of 12 mg i.v., unsuccessfully. Verapamile 10 mg i.v. was administered afterward, still with no effect in cardiac rhythm control.

Next, direct current cardioconversion was attempted, after patient’s light sedation. Three synchronized shocks of 50 and 100 J were delivered.

Finally, an amiodarone drip of 150 mg in 20 minutes, followed by an infusion of 1 mg/min for 6 hours, controlled the heart rate to be 100 to 120 bpm. The patient was then transferred in the Cardiology ICU for surveillance, without any recurrent episode in the next 36 hours, and was then transferred to general ward and discharged the day following.

Throughout the whole episode, which lasted approximately 90 minutes, the patient was fully alert and oriented, maintaining a MAP > 65 mm Hg. All laboratory tests and arterial blood gas analysis remained within normal limits.

Ondansetron is a selective 5-HT3-receptor antagonist, known to prolong QT interval. The risk of arrythmia is described, with special precaution when treating a patient with congenital long QT syndrome, or on the ground of electrolyte imbalances. ¹ None of the mentioned was applicable in this patient.

Most cases reported in literature concern children with an underlying cardiac condition, ² with 2 deaths reported in this age group. ³

Concerning adults, there are a few cases in the literature discussing arrythmias following ondansetron administration in a perioperative setting.

A case of pulseless VT requiring CPR has been reported following ondansetron administration intraoperatively, on a ground of hypomagnesemia and hypokalemia, which was successfully managed, ⁴ whereas another case of VT required cardioconversion to return to sinus rhythm. ⁵

Another arrythmia associated with ondansetron has been atrial fibrillation, with Kasinath et al reporting a case who finally needed pharmaceutical treatment and surveillance, ⁶ while Havrilla et al a case developing ST segment alterations on top of atrial fibrillation onset. ⁷ Both cases had unremarkable previous medical history and the arrythmia was manifested after a second ondansetron dosage.

Overall, 3 out of 4 mentioned cases concerned young women.

Perioperative patients must always be closely monitored, as even old and daily used pharmacological agents can reveal unexpected side effects.