NM-324
Use of ketamine-based total IV anesthetic in a pediatric patient with complex cardiac history to augment decreased baseline motor evoked potentials during urgent spine surgery complicated by severe postoperative delirium
Hamilton A, Yalamanchili V
Children's Healthcare of Atlanta/ Emory University, Atlanta, GA, USA
Intro:
We evaluate a uniquely challenging case of a 12 year old, 39kg female with history of tetralogy of fallot and complete atrioventricular canal defect s/p repair, complete heart block and reduced cardiac function due to cardiac dyssynchrony with CRT pacemaker, and severe congenital kyphoscoliosis who presented with worsening lower extremity myelopathy due to spinal cord compression. The patient underwent urgent posterior spinal fusion, hemivertebrectomy and spinal cord decompression.
Case:
The patient arrived to preoperative holding without an IV and refusing oral premedication. Cardiology reprogrammed her pacemaker from DDD to DOO to minimize electrocautery interference while maintaining cardiac stability. Despite gradual titration of sevoflurane during inhalational induction, the patient developed marked hypotension. Intravenous access was rapidly obtained and IV induction proceeded with 1mg/kg ketamine, 0.5mcg/kg fentanyl, 0.5 mg/kg propofol and intermittent bolusing of epinephrine. The patient was easily intubated. An additional peripheral IV, arterial line, and central line were placed. Maintenance anesthesia consisted of 0.5 MAC isoflurane, 50mcg/kg/min propofol infusion, and 1mcg/kg/hour fentanyl infusion. Epinephrine infusion was placed in line prior to prone positioning. A BIS monitor was used to guide anesthetic titration.
Due to severely diminished baseline motor evoked potentials, we anticipated a high likelihood of “wake up†testing and fentanyl was changed to remifentanil infusion. Repeat MEPs declined further and “wake up†test was initiated. To maximize further neurophysiologic monitoring, we changed to a total IV anesthetic with ketamine 1mg/kg/hour, propofol 25mcg/kg/min, and remifentanil 0.1-0.3mcg/kg/min. Midazolam was bolused hourly to reduce recall and prevent postoperative delirium associated with ketamine. Epinephrine infusion was titrated to maintain mean arterial pressures greater than 80mmHg to optimize spinal cord perfusion. Serial arterial blood gases showed adequate arterial oxygen content and hematocrit. The case proceeded with improvement in MEPs. Patient was extubated in the OR and able to move all extremities on command. She received toradol and additional boluses of fentanyl for pain control. She developed severe postoperative delirium related to the ketamine and was treated with IV diazepam and dexmedetomidine.
Discussion:
We evaluate our anesthetic concerns from a cardiac standpoint, including pacemaker management in setting of sizable electrocautery near generator and preservation of RV-PA conduit patency with prone positioning and manipulation of thoracic curvature/diameter. Additionally, we compare and contrast strategies for maintaining a balanced anesthetic while optimizing cardiac function and neurophysiologic monitoring in a patient with decreased baseline MEPs. Furthermore, the patient needed to rapidly recover from the anesthetic and cooperate with “wake up†testing. We also discuss the benefits and limitations of ketamine based anesthetics, particularly in regards to hemodynamic stability, BIS monitoring, pain control, and delirium.
1. Lotto, M et al. Effects of anesthetic agents and physiologic changes on intraop MEPs. J Neurosurg Anes Vol 16, 1, 2004
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