2016 Spinal Cord Perfusion Pressure Correlates With Breathing Function in Patients With Acute, Cervical Traumatic Spinal Cord Injuries

INTRODUCTION: Traumatic spinal cord injury (TSCI) is a catastrophic event which significantly impairs breathing function. It is not known whether spinal cord perfusion pressure (SCPP) correlates with diaphragmatic and intercostal muscle function. METHODS: Prospective cohort study of 13 cervical TSCI patients (ASIA AIS grades A-C) and 8 patients without cervical TSCI. During surgery within 72 hours of injury, intradural probes were inserted for monitoring the injury site intraspinal pressure (ISP), tissue oxygen (psctO2) and microdialysis (MD), in the intensive care unit (ICU). Breathing function was evaluated using diaphragmatic electromyography (EDI), diaphragmatic and intercostal ultrasound (total 1,511 measurements). 1,458 hours of continuous data were analysed. RESULTS: During quiet breathing, low SCPP (<60 mmHg) was associated with reduced peak & minimum EDI. EDI increased and plateaued at SCPP 60–100 mmHg. During quiet and deep breathing, the diaphragmatic thickening fraction (force of contraction) plotted against SCPP had an inverted-U relationship, with a peak at SCPP 80–90 mmHg. Diaphragmatic excursion (up and down movement) during quiet breathing did not correlate with SCPP, but during deep breathing plotted against SCPP had an inverse-U relationship with a peak at SCPP 80–90 mmHg. Intercostal muscle thickening fraction plotted against SCPP also had inverted-U relationship, with normal intercostal function at SCPP 80–100 mmHg, but failure of the upper and middle intercostals to contract during inspiration (i.e. abdominal breathing) at SCPP < 80 or > 100 mmHg. Therefore, spinal cord hypoperfusion or hyperperfusion may negate beneficial trends in breathing parameters. CONCLUSIONS: After acute cervical TSCI, breathing function depends on the SCPP. SCPP 80–90 mmHg correlates with optimum diaphragmatic and intercostal muscle function. Our findings raise the possibility that intervention to maintain SCPP in this range may accelerate ventilator liberation which may reduce stay in the neuro-ICU.