2016 FSA Posters

P034: COMPLICATIONS FOLLOWING ANEURYSM REPAIR DESPITE THE USE OF NEUROMONITORING UNDER GENERAL ANESTHESIA
Wasef Muzaffar, MD, Sonia Mehta, MD; University of Florida

Introduction: 71-year-old woman status post previous cerebral aneurysm repair was found to have on recent imaging a right middle cerebral artery bifurcation aneurysm which had enlarged. Patient was consented for craniotomy and clipping, with neuromonitoring with electroencephalogram (EEG), somatosensory evoked potentials (SSEPs), and motor evoked potentials (MEPs).

Case Report: Patient was taken to the operating room and was induced with general anesthesia using a total intravenous technique with propofol and remifentanil infusions. Depolarizing muscle relaxant succinylcholine was used during intubation. Baseline EEG, SSEPs, and MEPs signals were obtained with adequate signal strength and with the normal ranges for this procedure. Mean arterial pressures were maintained at a value greater than 80 and neurosurgeons were able to identify and clip both right internal carotid artery and middle cerebral artery aneurysms without complication. Patient did not experience any changes of increased latency nor decreased amplitude of signals throughout the duration of the operation. Additionally, she did not have any significant changes to her EEG waveform.

Following completion of aneurysm repair and during closing of craniotomy, neuromonitoring was discontinued. Upon emergence while still intubated patient maintained spontaneous ventilation but did not exhibit significant movement of any of her extremities. Patient demonstrated the ability to protect her airway and adequate minute ventilation and was extubated. She continued to maintain saturations on room but after greater than forty-five minutes after completion of discontinuation of anesthesia did not demonstrate any response to commands, any purposeful movement of extremities nor withdrawal to noxious stimuli. Immediate computed tomography (CT) imaging study following operation demonstrated no evidence of stroke and patient was transferred to the neurosurgical intensive care unit (NICU) for close neurologic and hemodynamic monitoring. EEG monitoring was resumed following admission to the NICU which demonstrated subclinical status epilepticus, so the patient was electively intubated and placed on antiepileptic medications for burst suppression.

Eventually her seizures were controlled on the most effective low dose oral antiepileptic drug schedule possible. She had several CT scans and an MRI scan which demonstrated no stroke, no mass, and no bleed except for normal postoperative changes.  Her ventricles were slightly enlarged so lumbar punctures were performed to measure opening pressure and to look for infectious causes of Mrs. Messer's altered mental status.  No organisms grew in the cerebrospinal fluid culture, and the opening pressure was within normal limits. Her Ammonia levels were found to be slightly elevated (70's at highest). She was discharged to a rehabilation facility non-verbal, weakly withdrawing bilateral upper extremities with a percutaneous endoscopic gastrostomy (PEG) tube.

Discussion:  What are the benefits and disadvantages of neuromonitoring for aneurysm repair and when should monitoring be discontinued?  Seizures under general anesthesia are a rare occurrence.  Despite this patient’s surgical repair, what other etiologies contribute to this finding?  In a patient with no history of liver disease, should additional testing of all lab values including liver function tests be mandatory for a high risk surgical procedure given ammonia has been linked to a reduction in seizure threshold?