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Corresponding author. G.B. Brunnekreef, M.D., Department of Anesthesiology and Intensive Care, St. Antonius Hospital, Koekoekslaan 1, Postbus 2500, 3430 EM Nieuwegein, The Netherlands.
Thoracic endovascular aortic repair is associated with postoperative spinal cord ischemia in approximately 1 to 12.5% of all cases.
S100β is a protein that is released during acute damage of the central nervous system. This study was performed to determine the concentration of S100β in cerebrospinal fluid during and after stenting of the thoracic aorta in patients at high risk for spinal cord ischemia.
Design
Prospective clinical study.
Materials and methods
Eight patients who underwent elective thoracic aortic stent grafting underwent lumbar spinal fluid drainage. These patients were at high risk to develop spinal cord ischemia.
Methods
CSF samples for analysis of S100β protein were drawn after induction of anesthesia, during stenting, once every hour the following six hours and 20 hours after repair.
Results
No significant increase in S100β protein could be detected in CSF and no neurological deficits were detected postoperatively.
Conclusions
The results of this study show us that there is no significant release of S100β protein in CSF during stenting of the thoracic aorta in this subgroup of patients at high risk for spinal cord ischemia, consistent with clinical exam that there was no significant damage to the central nervous system.
Surgical treatment of thoracic and thoracoabdominal aortic aneurysms may be associated with a significant risk of perioperative morbidity, including paraplegia and paraparesis. The risk to develop paraplegia or paraparesis has been reported to be 4 to 21%.
Cerebrospinal fluid drainage to prevent paraplegia during thoracic and thoracoabdominal aortic aneurysm surgery: a systematic review and meta-analysis.
In selected thoracic aneurysms, there is a possibility for endovascular aortic repair, which is accompanied with far less morbidity and mortality. The risk to develop postoperative paraplegia or paraparesis however remains 1 to 12.5% with an average of 2.7%.
Cerebrospinal fluid (CSF) drainage theoretically can improve the blood supply to the spinal cord. CSF drainage reduces the risk of postoperative paraplegia after open surgical repair of thoracic and thoracoabdominal aneurysms.
Cerebrospinal fluid drainage to prevent paraplegia during thoracic and thoracoabdominal aortic aneurysm surgery: a systematic review and meta-analysis.
The S100β protein is such a marker: it is a calcium binding protein which is found in high concentrations in glial and Schwann cells and is unique to the central nervous system. The S100β protein is released during acute damage of the central nervous system such as spinal cord ischemia due to hypoperfusion.
Normal serum concentrations of S-100 protein and changes in cerebrospinal fluid concentrations of S-100 protein during and after thoracoabdominal aortic aneurysm surgery: is S-100 protein a biochemical marker of clinical value in detecting spinal cord ischemia?.
The relationship between evoked potentials and measurements of S-100 protein in cerebrospinal fluid during and after thoracoabdominal aortic aneurysm surgery.
Baseline values of S100β protein in CSF range from approximately 0.9 to 1.7 μg/L and may rise to approximately 4.0 μg/L during surgical thoracoabdominal aortic replacement without postoperative neurological deficits.
Normal serum concentrations of S-100 protein and changes in cerebrospinal fluid concentrations of S-100 protein during and after thoracoabdominal aortic aneurysm surgery: is S-100 protein a biochemical marker of clinical value in detecting spinal cord ischemia?.
This study was performed to determine the concentration of S100β protein in CSF during and after stenting of the thoracic aorta in patients at high risk for spinal cord ischemia.
Materials and Methods
Eight patients, three men and five women, aged 58 to 76 years (mean, 68 years) who underwent elective thoracic aortic stent grafting participated in the study. All patients were free from any neuromuscular disorder. The spinal fluid drainage and S100β measurements were approved by the Institutional Ethics Committee.
All stent grafts were inserted for treatment of thoracic aortic aneurysms. The studied patients were considered at a higher risk than the previously mentioned 2.7% to develop postoperative paraplegia or paraparesis. This assumption was made because the aneurysms involved critical intercostal arteries (T8-L2), the total thoracic descending aorta was to be covered or the patient had a history of previous abdominal aortic aneurysm repair. For these reasons patients underwent lumbar spinal fluid drainage in order to keep the spinal fluid pressure at a maximal level of 10 mm Hg. The catheter (Integra NeuroSciences Implants S.A., Sophia Antipolis, France) was left in place for 20 hours postoperatively.
In one patient critical intercostal arteries (T8-L2) were covered, after previous surgical treatment of an abdominal aortic aneurysm. The other seven patients received stents covering the total thoracic descending aorta. Four of these seven patients also had a history of abdominal aneurysm repair.
CSF samples for analysis of S100β protein were drawn after induction of anesthesia, during stenting, once every hour the following six hours and 20 hours after repair.
One patient was considered to run a higher risk of developing postoperative paraplegia or paraparesis compared to the other patients. This assessment was made because of this patient's history of infrarenal and thoracoabdominal aortic replacement. The final part of his native descending aorta was going to be excluded by stenting. For these reasons the decision was made to continue CSF drainage for 48 hours postoperatively and an extra CSF sample was taken after 48 hours.
The CSF concentrations of S100β protein were analyzed with a commercially available enzyme-linked immunosorbent assay kit (Sangtec_100 ELISA kit, Sangtec Molecular Diagnostics AB, Bromma, Sweden). All samples were analyzed in duplicate, with a variation of less than 10%. A measurement takes approximately two hours.
Results
No significant increase in S100β protein during the procedures could be demonstrated in CSF and no central or peripheral neurological deficits were detected postoperatively.
However in the one patient, who was considered to have the highest risk for developing postoperative paraplegia or paraparesis, we found a more than three fold increase in the S100β concentration in CSF. This relative increase normalized during the second postoperative day (Fig. 1). Despite this temporary relative increase the absolute value of S100β protein stayed within the normal range. This patient showed no clinical signs of neurological damage postoperatively.
Fig. 1Vertical axis: Boxplots show the median, interquartile range and extremes of the concentration (μg/L) of S100β protein in CSF. The asterisk shows the samples of the extreme high risk patient, while the boxplots represent the samples of the other seven patients.
Horizontal axis: the different samples taken:
Sample 1: After induction of anesthesia
Sample 2: During placement of the stent
Sample 3: One hour after stent placement
Sample 4: Two hours after stent placement
Sample 5: Three hours after stent placement
Sample 6: Four hours after stent placement
Sample 7: Five hours after stent placement
Sample 8: Six hours after stent placement
Sample 9: Twenty hours after stent placement
Sample 10: Forty-eight hours after stent placement
The results of this study show that there is no significant release of S100β protein in CSF during stenting of the thoracic aorta in this small subgroup of patients at high risk for spinal cord ischemia. This correlated with the absence of postoperative neurological deficits and suggests that there may have been no significant damage to the central nervous system.
The normal range of S100β protein in CSF however may differ per person and it remains unknown whether one should focus on absolute or relative increases in S100β protein when monitoring damage to the central nervous system.
Postoperative neurologic deficits are caused by interruption of sufficient duration of spinal cord blood supply. A CT angiography was performed in all patients in order to accurately size the stents needed, however, in our hospital it was not accurate enough to reliably identify all intercostal arteries supplying the spinal cord. Preoperative spinal cord angiography was not performed. Angiographic localization itself can cause serious complications such as emboli. Furthermore paralysis after elective open repair still occurs among those with preoperative detailed spinal cord blood supply.
Important may be the fact that measuring the S100β protein concentration in CSF in this small group of patients meant that we also took a protective measure. All patients underwent CSF drainage to keep the spinal fluid pressure at 10 mm of Hg or less to help prevent damage to the spinal cord. Perfusion pressure of the spinal cord is equal to mean arterial blood pressure less venous pressure or CSF pressure, whichever is higher. Therefore keeping the CSF pressure low may improve perfusion of the spinal cord. For these reasons the release of S100β might have been altered by our treatment. It was considered unethical though not to keep the spinal fluid pressure at safe levels.
The value of 10 mm Hg was chosen because it has been proven that keeping the CSF pressure at 10 mm Hg or less helps to protect against ischemic damage to the spinal cord during and after surgical replacement of the thoracoabdominal aorta.
Cerebrospinal fluid drainage to prevent paraplegia during thoracic and thoracoabdominal aortic aneurysm surgery: a systematic review and meta-analysis.
Systematic overview of the evidence supporting the use of cerebrospinal fluid drainage in thoracoabdominal aneurysm surgery for prevention of paraplegia.
Whether there is an indication for CSF drainage in a subgroup of patients at high risk to develop neurological deficits after endovascular repair has never been defined.
Following endovascular thoracic aortic aneurysm repair, there are several case reports that show reversal of postoperative paraplegia after institution of cerebrospinal fluid drainage.
Patients after endovascular repair can be neurologically examined directly postoperative. Immediate postoperative CSF drainage may possibly be almost as effective as preoperative institution of CSF drainage, because of the short duration of preventable spinal cord ischemia.
The complications of CSF drainage can be life threatening, which is why its management should not be taken lightly. Considering the fact that lumbar CSF drainage is not without risks
the indications for its use during thoracic endovascular stent grafting remain to be studied, since even in this small subgroup of patients at high risk to develop postoperative paraplegia or paraparesis there was no rise in S100β protein in the CSF.
References
Cinà C.S.
Abouzahr L.
Arena G.O.
Laganà A.
Devereaux P.J.
Farrokhyar F.
Cerebrospinal fluid drainage to prevent paraplegia during thoracic and thoracoabdominal aortic aneurysm surgery: a systematic review and meta-analysis.
Normal serum concentrations of S-100 protein and changes in cerebrospinal fluid concentrations of S-100 protein during and after thoracoabdominal aortic aneurysm surgery: is S-100 protein a biochemical marker of clinical value in detecting spinal cord ischemia?.
The relationship between evoked potentials and measurements of S-100 protein in cerebrospinal fluid during and after thoracoabdominal aortic aneurysm surgery.
Systematic overview of the evidence supporting the use of cerebrospinal fluid drainage in thoracoabdominal aneurysm surgery for prevention of paraplegia.
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