Neurological Outcome in Spinal Cord Blood Flow Reduction by Cerebrospinal Fluid Pressure Increase—A Chronic Large Animal Model

Background: Spinal cord ischemia is a known and devastating complication after open and endovascular thoracoabdominal aneurysm replacement. Several neuroprotective adjuncts have been established to improve spinal cord perfusion or at least early detection of spinal cord ischemia. Drainage of cerebrospinal fluid is one major support in peri- and postoperative optimization of spinal cord blood flow by reducing the intrathecal pressure. A previous acute large animal model already demonstrated a decrease to 50% of blood flow, even with open segmental arteries, however, we aimed for an investigation of the (neurological) outcome.

Methods: We used our established large animal model. Twenty juvenile pigs received CSF placement of CSF catheter, left atrium catheter for microsphere injection and aortic catheter for reference blood acquisition. Afterwards iatrogenic CSF pressure elevation x3 from their individual baseline pressure was realized. Pressure increase was maintained for 30 minutes (mimicking clinical response time). After CSF pressure increase the dural sack was depressurized against gravity allowing CSF pressure to return to baseline values - either slowly (group 1) or rapidly (group 2) . Measurements were taken 30 minutes after normalization and 24, 48 and 72 hours. Microspheres for regional blood flow analysis were injected at each time point. Pigs were sacrificed three days after surgery.

Results: Neurological assessment of the pigs show no paraplegia during the three day follow up. However, spinal cord perfusion was significantly diminished in both groups solely by CSF pressure increase (even in the physiological setting of open segmental arteries). In both groups perfusion after normalization was significantly higher than in the postoperative course at 24, 48 and 72 hours. However, slow depressurization led to less pronounced hyperperfusion. Collateral network near-infrared spectroscopy displayed stable values during the whole experiment. Post mortem histological analysis did not show any pathological findings.

Conclusion: Although an increase in CSF pressure reduced spinal cord perfusion to 50% of baseline, no neurological impairment could be detected in the postoperative three day follow up. Hyperperfusion was worse in pigs receiving rapid depressurization but did not impact outcome. In a physiological setting ischemic tolerance of the spinal cord is sufficient to survive even a reduction to 50% of baseline blood flow.

Publication History

Article published online:
13 February 2024