Continuous monitoring and visualization of optimum spinal cord perfusion pressure in patients with acute cord injury.
Chen S, Smieleweski P, Czosnyka M, Papadopoulos MC, Saadoun S
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 hours of severe TSCI (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 (cSCPPopt) as the SCPP that minimizes sPRx in a moving four-hour window. In 45 patients, we monitored ISP and blood pressure. In 14 patients, we also monitored injury site metabolism. cSCPPopt could be computed 45 % of the time. Mean cSCPPopt varied by up to 60 mmHg between patients and each patient's cSCPPopt varied with time (standard deviation 10-20 mmHg). Color-coded maps showing the sPRx/SCPP curve evolution enhanced visualization of cSCPPopt. Periods when SCPP ≈ cSCPPopt were associated with low injury site glucose, high pyruvate and high lactate. Mean SCPP deviation from cSCPPopt inversely correlated with neurological outcome at 9-12 months: ASIA grade improved in 30 % patients with <5 mmHg deviation, 10 % with 5-15 mmHg deviation and no-one with >15 mmHg deviation. We conclude that real-time computation and visualization of cSCPPopt after TSCI are feasible. cSCPPopt appears to enhance glucose utilization at the injury site and varies widely between and within patients. Our data suggest that targeting cSCPPopt after TSCI might improve neurological outcome.