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) 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 could be computed 45% of the time. Mean cSCPP varied by up to 60 mm Hg between patients. Each patient's cSCPP varied with time (standard deviation 10-20 mm Hg). Color-coded maps showing the sPRx/SCPP curve evolution enhanced visualization of cSCPP. Periods when SCPP ≈ cSCPP were associated with low injury site glucose, high pyruvate, and high lactate. Mean SCPP deviation from cSCPP 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 after TSCI are feasible. cSCPP appears to enhance glucose utilization at the injury site and varies widely between and within patients. Our data suggest that targeting cSCPP after TSCI might improve neurological outcome.

Targeted Perfusion Therapy in Spinal Cord Trauma

“…Potential mechanisms of hyperperfusion-induced cord injury include cord swelling, cord hemorrhage, and a local steal phenomenon [22]. sPRx versus SCPP plots for individual patients, rather than pooled patient data, yield SCPP opt values that differ markedly, by up to 60 mmHg, between patients [23]. The patientdependent SCPP opt suggests that individualized patient management is required to achieve targeted perfusion therapy.…”

“…Second, there is often a range of SCPPs, rather than a single value (minimum of the sPRx versus SCPP curve), associated with intact autoregulation. We thus extended the concept of SCPP opt to represent a range of pressures, computed from a sliding window of the preceding 4 h, updated each minute [23]. An enhanced display technique allows the SCPP and SCPP opt to be visualized in real time in a clinically meaningful way on the ICU monitors ( Fig.…”

Predictors of Intraspinal Pressure and Optimal Cord Perfusion Pressure After Traumatic Spinal Cord Injury

“…Hyper-perfusing injured cord is associated with more deranged injury site metabolism [35]. In TBI patients, hyper-perfusion of the brain is associated with worse neurological outcome [36], although this finding has not yet been replicated in TSCI (due to insufficient number of TSCI patients exceeding the SCPP opt ), the same trend may apply [8]. To date, the only way to avoid hyper-perfusing the injured cord is by determining the SCPP opt by ISP monitoring.…”

“…TSCI patients with mean SCPP ≈ SCPP opt more often improve their AIS (American spinal injuries association Impairment Scale) grade than patients with SCPP very different from SCPP opt [8]. Thus, targeting the SCPP opt could form the basis for individualizing the treatment of TSCI in a physiologically meaningful manner.…”

“…When compared with the current guideline of maintaining MAP at 85–95 mmHg in all TSCI patients [11], the concept of individualized management, based on SCPP opt , represents a paradigm shift. A universal MAP target is inadequate because TSCI patients have different ISPs and because the SCPP opt varies widely between patients [4, 5, 8]. The aim here is to identify clinical and magnetic resonance imaging (MRI) features for predicting ISP and SCPP opt in each TSCI patient.…”