Subarachnoid Fluid Lactate and Paraplegia after Descending Aorta Aneurysmectomy: Two Compared Case Reports

We report a comparison of two cases regarding subjects who underwent thoracoabdominal aorta aneurysmectomy. During the procedure we monitored cerebrospinal fluid lactate concentration. One patient experienced postoperative paraplegia and his cerebrospinal fluid lactate concentration was much higher than that in the other case, whose postoperative outcome was uneventful. Consequently we consider that monitoring the lactate concentration in cerebrospinal fluid during thoracic aorta surgical procedures may be a helpful tool to predict the ischemic spine-cord injury allowing for trying to recover it precociously. 1. Introduction During descending aorta surgical repair, spinal cord deficit due to ischemia is a dreadful complication that comes with paraparesis/paraplegia in 6–40% of patients [1, 2]. In this setting, lactate releasing is the epiphenomenon of cellular suffering due to insufficient oxygen delivery. When spinal cord experiences an ischemic event, lactate production occurs as neurons switch on anaerobic metabolism. As literature reports, when blood brain barrier (BBB) is intact, subarachnoid lactate level depends on local production, then it is due to neuronal hypoxic suffering [3]. To prevent spinal cord injury cerebrospinal fluid (CSF) drainage, aimed to reduce intrathecal pressure to provide a better blood perfusion, is a technique now accepted by anesthesiologists and cardiovascular surgeons, although its effectiveness is controversial [4, 5]. During descending aorta surgery, we usually monitor the lactate trend in CSF, as this type of operation exposes the patient to the risk of spinal ischemia due to aortic clamping proximally to Adamkiewicz artery. Normal spinal fluid lactate concentration ranges from 0.6 to 3.1？mmol/L. Its level is age related and it can rise when spinal ischemic event occurs, also depending on the lasting of the low flow state [6, 7]. In our hospital, descending aorta surgical repair is performed without cardiopulmonary by-pass. Our experience on this kind of operation arises from a series of 8–10 cases per year. Out of 8 cases observed in the last year, we report two comparable cases of thoracic aorta repair with different neurological outcome that could have been predicted by intraoperative trend of lactate in subarachnoid fluid. 2. Case Report 1 A 61-year-old male patient (ASA 3; BMI 26.0？kg/mq body surface area) underwent general anesthesia for thoracic aorta aneurysmectomy. Preoperative blood test did not show any significant alteration but high level of serum creatinine (4.0？mg/dL) due to chronic renal failure (CRF)