Targeted Perfusion Therapy in Spinal Cord Trauma

Abstract

We review state-of-the-art monitoring techniques for acute, severe traumatic spinal cord injury (TSCI) to facilitate targeted perfusion of the injured cord rather than applying universal mean arterial pressure targets. Key concepts are discussed such as intraspinal pressure and spinal cord perfusion pressure (SCPP) at the injury site, respectively, analogous to intracranial pressure and cerebral perfusion pressure for traumatic brain injury. The concept of spinal cord autoregulation is introduced and quantified using spinal pressure reactivity index (sPRx), which is analogous to pressure reactivity index for traumatic brain injury. The Ushaped relationship between sPRx and SCPP defines the optimum SCPP as the SCPP that minimizes sPRx (i.e., maximizes autoregulation), and suggests that not only ischemia but also hyperemia at the injury site may be detrimental. The observation that optimum SCPP varies between patients and temporally in each patient supports individualized management. We discuss multimodality monitoring, which revealed strong correlations between SCPP and injury site metabolism (tissue glucose, lactate, pyruvate, glutamate, glycerol), monitored by surface microdialysis. Evidence is presented that the dura is a major, but unappreciated, cause of spinal cord compression after TSCI; we thus propose expansion duroplasty as a novel treatment. Monitoring spinal cord blood flow at the injury site has revealed novel phenomena, e.g., 3 distinct blood flow patterns, local steal, and diastolic ischemia. We conclude that monitoring from the injured spinal cord in the intensive care unit is a safe technique that appears to enable optimized and individualized spinal cord perfusion.

Implantable Osmotic Transport Device Can Reduce Edema After Severe Contusion Spinal Cord Injury

“…While the spinal cord and subarachnoid space are clearly non-uniform, this estimate addresses how minute increases in % water content due to swelling may lead to constriction of the local vasculature in SCI. This is consistent with experimental results observed by others (Saadoun and Papadopoulos, 2020).…”

“…(B) After injury, severe edema emanates from the central location of the spinal cord and forces tissue against the dura mater. This constricts local blood vessels in the subarachnoid space (illustrated as red) as well as reduces CSF movement in the local region (Saadoun and Papadopoulos, 2020). (C) The OTD is placed at the point of injury directly on the dura mater.…”

“…These initial studies suggest that spinal cord parenchymal swelling due to edema accumulation continues to expand radially until the tissue reaches the dura and can no long swell outward, despite routine decompressive laminectomy. This leads to an inevitable localized pressure build-up that causes the subarachnoid space to collapse at the epicenter and significant constriction of flow within local blood vessels (Soubeyrand et al, 2014a;Khaing et al, 2018;Saadoun and Papadopoulos, 2020). The collapsed blood vessels are no longer able to supply nutrients to the surrounding tissue and this creates local ischemia, further worsening tissue secondary injury (Gallagher et al, 2019).…”

Mechanical stress regulates autophagic flux to affect apoptosis after spinal cord injury

“…On the other hand, in addition to the direct regulation of mechanical stress, nutritional deficiencies and hypoxia are also effective stimuli for autophagy 56 . Decompression increases blood flow to the spinal cord and rebuilds cerebrospinal fluid circulation, thus preventing the spinal cord from continuing ischaemic injury 57,58 . Decompression partially alleviated nutritional deficiencies and hypoxia in nervous tissue.…”

“…56 Decompression increases blood flow to the spinal cord and rebuilds cerebrospinal fluid circulation, thus preventing the spinal cord from continuing ischaemic injury. 57,58 Decompression partially alleviated nutritional deficiencies and hypoxia in nervous tissue. Therefore, IMP may also have an indirect effect on autophagic flux.…”