A Rare Case of Propofol-Induced Myoclonus after Prolonged Infusion

SESSION TITLE: Student/Resident Case Report Poster - Critical Care V SESSION TYPE: Student/Resident Case Report Poster PRESENTED ON: Tuesday, October 25, 2016 at 01:30 PM - 02:30 PM INTRODUCTION: Propofol is an intravenous anesthetic used in the intensive care unit primarily for its sedative and hypnotic properties. The use of propofol as an anticonvulsant in refractory status epilepticus is well documented in the literature. We present a case of propofol-induced myoclonus after prolonged intravenous administration. CASE PRESENTATION: A 27- year-old male was admitted to the intensive care unit for treatment of respiratory failure secondary to smoke inhalation injury suffered during a residential fire. Social history was positive for alcohol and tobacco abuse. He was intubated and mechanically ventilated. Carboxyhemoglobin level was 9.0%. Smoke inhalation injury treatment was initiated with inhaled heparin, acetylcysteine, albuterol, and intravenous dexamethasone. Propofol and fentanyl infusion were initiated for sedation and analgesia, respectively. On hospital day 16, the patient developed non-rhythmic involuntary facial twitching and jerking movements of the neck, shoulders, and upper extremities. Two electroencephalograms (EEG) were within normal limits, without any epileptiform discharges associated with the movements. Head computerized tomography (CT) and brain magnetic resonance imaging (MRI) did not exhibit focal pathology. Benztropine and midazolam did not resolve the symptoms. Propofol was discontinued and the patient's neuromuscular symptoms gradually resolved over the next 48 hours. DISCUSSION: Propofol has anticonvulsant properties. In rare cases, it is linked to seizure-like phenomena including generalized clonic-tonic seizures, focal motor seizures, muscle twitching, opisthoclonus, and myoclonus in the intraoperative period or shortly after anesthesia. However, there is a paucity of reports of propofol-induced neurological symptoms after prolonged infusion. In contrast to the perioperative seizure-like phenomena, the neurologic symptom in this case was refractory to treatment and only ceased shortly after discontinuation of propofol. The etiology of the seizure-like phenomena linked to propofol still remains unknown. Carbon dioxide poisoning is also associated with delayed movement disorders ranging from Parkinsonism to myoclonus; however, these symptoms are seen in patients with encephalopathy and/or brain ischemia. In this patient, the negative EEG and brain MRI further support the diagnosis of propofol-induced myoclonus. CONCLUSIONS: Propofol is a well-known antiepileptic used in refractory status epilepticus. Interestingly, in this case, propofol had a paradoxical effect causing myoclonus after prolonged infusion. A thorough workup is mandated to exclude life-threatening etiologies before attributing the seizure-like phenomena to propofol. Reference #1: Choi IS, Cheon HY. Delayed movement disorders after carbon monoxide poisoning. Eur Neurol 1999;42:141-4. Reference #2: Tam MKP, Irwin MG, Tse ML, Lui YWA, Law KI, Ng PW. Prolonged myoclonus after a single bolus does of propofol. Anaesthesia 2009; 64: 1254-7. DISCLOSURE: The following authors have nothing to disclose: Stamatis Baronos, Danny Basri, William Darko, Ryan Dean, Anuj Sharma, Anil Ghimire No Product/Research Disclosure Information