P017: IDENTIFICATION OF LOWER LIMIT OF CEREBRAL AUTOREGULATION DURING VATS
Rita S Patel, MD, Jay W Johansen, MD, PhD; UFCOM Jacksonville
Introduction: Several monitors are available for various forms of monitoring the anesthetized patient. Although debated on standardized usage for all cases, monitors like bispectral index(BIS) and cerebral oximetry are useful in patients with multiple comorbidities undergoing complex procedures1,2. We discuss a case of a patient undergoing thoracotomy with changes in cerebral oximetry without corresponding changes in BIS.
Case: A 64 year old man with a history of tonsillar cancer, who later developed osteosarcoma of the mandible with resection and reconstruction, presented in sepsis with post-obstructive pneumonia, was found to have a right upper lobe mass suspected of being metastatic osteosarcoma underwent right thoracotomy. Past medical history included OSA, HTN, HLD, DM, A fib, hypertrophic cardiomyopathy with dual chamber pacemaker, and CAD with inferior wall infarct 4 months prior to the procedure.
After induction, a single lumen endotracheal tube was placed and the double lumen tube was exchanged over a bougie, due to small mouth opening and Grade III view with video laryngoscopy. BIS, placed over the left forehead, and cerebral oximetry monitors were placed. After 1mg of hydromorphone was administered, BP decreased immediately to as low as MAP of 38. Cerebral oximetry readings decreased from a baseline of 60s to 40s in a linear fashion with MAP. Perfusion was noted to reverse from initially greater in the right to greater in the left, and returned to baseline after blood pressure increased. No changes in BIS were noted. He required boluses of vasopressin and norepinephrine to correct his blood pressure over 33 minutes and return cerebral oximetry values to baseline. The remainder of the case was uneventful.
Discussion: Cerebral oximetry can be used for monitoring cerebral autoregulation3. Some have used cerebral oximetry as a means to determine the lower limit of CPP4. In our case, the differential between right and left cerebral oximetry may suggest clinically significant vascular disease in the patient’s anterior cerebral circulation.
BIS, typically used for monitoring anesthetic depth, showed a correlation in changes of cerebral perfusion with cerebral oximetry in some studies5, while others, like the case at hand, did not note this correlation2.
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