Continuous Monitoring and Visualization of Optimum Spinal Cord Perfusion Pressure in Patients with Acute Cord Injury

Abstract

The optimum spinal cord perfusion pressure (SCPP) after traumatic spinal cord injury (TSCI) is unknown. Here, we describe techniques to compute and display the optimum SCPP in real time. We recruited adults within 72 h of severe TSCI (American Spinal Injuries Association [ASIA] grades A-C). A pressure probe and a microdialysis catheter were placed on the injured cord. SCPP was computed as mean arterial pressure (MAP) minus intraspinal pressure (ISP), spinal pressure reactivity index (sPRx) as the running ISP/MAP correlation coefficient, and continuous optimum SCPP (cSCPP_opt) as the SCPP that minimizes sPRx in a moving 4-h window. In 45 patients, we monitored ISP and blood pressure. In 14 patients, we also monitored injury site metabolism. cSCPP_opt could be computed 45% of the time. Mean cSCPP_opt varied by up to 60 mm Hg between patients. Each patient's cSCPP_opt varied with time (standard deviation 10-20 mm Hg). Color-coded maps showing the sPRx/SCPP curve evolution enhanced visualization of cSCPP_opt. Periods when SCPP ≈ cSCPP_opt were associated with low injury site glucose, high pyruvate, and high lactate. Mean SCPP deviation from cSCPP_opt correlated with worse neurological outcome at 9–12 months: ASIA grade improved in 30% of patients with <5 mm Hg deviation, 10% of patients with 5–15 mm Hg deviation, and no one with >15 mm Hg deviation. We conclude that real-time computation and visualization of cSCPP_opt after TSCI are feasible. cSCPP_opt appears to enhance glucose utilization at the injury site and varies widely between and within patients. Our data suggest that targeting cSCPP_opt after TSCI might improve neurological outcome.