PRO:

William C. Oliver, Jr., MD
Division of Cardiothoracic Anesthesiology
Mayo Foundation, Rochester, MN

Paraplegia after thoracic or thoracoabdominal aortic (TAA) repair ranges from 0.2 - 40% depending on acuity and extent of surgery.^{1, 2} Paraplegia may be related to thrombosis, embolization, intercostal artery disruption, reperfusion injury, or spinal cord hypoperfusion during aortic cross-clamping (AXC). Many approaches have been tried to reduce the incidence of paraplegia but no single measure, or combination of techniques has eliminated this problem.

Thoracic AXC reduces spinal cord blood flow. The extent to which this happens is a function of variable anatomic considerations of the thoracolumbar intercostal arteries to the anterior spinal artery. Thoracic AXC also increases cerebrospinal fluid (CSF) pressure acutely in both animal models³ and humans undergoing TAA repair.⁴ Increased CSF pressure after AXC is one important factor contributing to spinal cord ischemia.⁵ Improved spinal cord blood flow has been demonstrated with CSF drainage.⁶ Maintaining or improving spinal cord perfusion, defined as the difference between the mean arterial pressure and CSF pressure, is the basis of CSF drainage. Since the 1960s, CSF drainage before and after aortic cross-clamping has been reported to reduce the incidence of paraplegia in animal models.² Even when other techniques reported to reduce the incidence of paraplegia are employed, such as distal aortic perfusion with a centrifugal pump; AXC may still increase CSF pressure and the risk for decreased spinal cord perfusion.⁴ The likelihood of increased CSF pressure after AXC, and the extremely low risk of this technique, justify the use of CSF drainage.

Reversal of delayed neurologic deficits after TAA repair following CSF drainage has been reported.⁷ Many uncontrolled, clinical observations support the use of CSF drainage⁸ although not all.^{1, 9} Crawford et al. found no reduction in the incidence of paraplegia with CSF drainage in a randomized prospective trial of 98 patients for TAA, but CSF pressure remained above 10 mm Hg in 57% of their patients despite CSF drainage.⁹ Murray et al.¹ also found no difference in the incidence of paraplegia with CSF drainage in a retrospective analysis; however, the treatment group may have been at higher risk for paraplegia than the control group. Svensson et al. conducted a randomized, controlled trial of TAA with CSF drainage and terminated their study early due to a significant difference in the neurologic outcome with CSF drainage.⁶ In the treatment group, the incidence of paraparesis was 12% with CSF drainage, while the control group had an incidence of 44%. Recently, LeMair et al. reported 80% reduction in the incidence of paraplegia in 145 patients undergoing Crawford extent I or II TAA repair in a randomized, prospective study with standardized operative strategy.¹⁰ The CSF pressure was maintained at 10 mm Hg with CSF drainage in the treatment group, while the control group had no CSF drainage.

The routine use of CSF drainage is a simple technique to decompress the spinal cord. The safety of placement of the drainage system in anesthetized patients has been demonstrated¹¹ even in patients requiring subsequent heparinization and cardiopulmonary bypass.¹² The risk of hematoma and neurologic injury is exceedingly rare and can be minimized by following certain guidelines.¹³

In conclusion, spinal cord protection is best accomplished with a multifaceted approach that includes the use of CSF drainage. The many different experimental conditions and strategies reported in the literature make it difficult to prove the value of CSF drainage alone. However, in light or recent evidence, it is prudent to consider the use of CSF drainage in all patients undergoing TAA repair.

References:

1. Murray MJ, Bower TC, Oliver Jr WC, Werner E, Gloviczki P: Effects of cerebrospinal fluid drainage in patients undergoing thoracic and thoracoabdominal aortic surgery. J Cardiothorac Vasc Anesth 1993; 7:266-72

2. Gharagozoloo F, Larson J, Dausmann MJ, Neville Jr RF, Gomes MN: Spinal cord protection during surgical procedures on the descending thoracic and thoracoabdominal aorta. Chest 1999; 109:

3. McCullough JL, Hollier LH, Nugent M: Paraplegia after thoracic aortic occlusion: Influence of cerebrospinal fluid drainage. Experimental and early clinical results. J Vasc Surg 1988; 7:153-60

4. Drenger B, Parker SD, Frank SM, Beattie C: Changes in cerebrospinal fluid pressure and lactate concentrations during thoracoabdominal aortic aneurysm surgery. Anesthesiology 1997; 86:41-7

5. Berendes JN, Bredee JJ, Schipperheyn JJ, Mashhour YAS: Mechanisms of spinal cord injury after cross-clamping of the descending thoracic aorta. Circulation 1982; 66(suppl I):112-6

6. Svensson LG, Von Ritter CM, Groeneveld HT, Rickards ES, Hunter SJ, Robinson MF, Hinder RA: Cross-clamping of the thoracic aorta. Influence of aortic shunts, laminectomy, papaverine, calcium channel blocker, allopurinol, and superoxide dismutase on spinal cord blood flow and paraplegia in baboons. Ann Surg 1986; 204:38-47

7. Azizzadeh A, Huynh TTT, Miller III CC, Safi HJ: Reversal of twice-delayed neurologic deficits with cerebrospinal fluid drainage after thoracoabdominal aneurysm repair: A case report and plea for a national database collection. J Vasc Surg 2000; 31:592-8

8. Ling E, Arrellano R: Systematic overview of the evidence supporting the use of cerebrospinal fluid drainage in thoracoabdominal aneurysm surgery for prevention of paraplegia. Anesthesiology 2000; 93:1115-22

9. Crawford ES, Svensson LG, Hess KR, Shenaq SS, Coselli JS, Safi HJ, Mohindra PK, Rivera V: A prospective randomized study of cerebrospinal fluid drainage to prevent paraplegia after high-risk surgery on the thoracoabdominal aorta. J Vasc Surg 1991; 13:36-45

10. LeMaire SA, Koksoy C, Schmittling ZC, Miller CC, Oberwalder PJ, Curling PE, Coselli JS: Cerebrospinal fluid drainage during thoracoabdominal aortic aneurysm repair prevents spinal cord ischemia. Ann Thorac Surg 2000; 70:1790A

11. Grady RE, Horlocker TT, Brown RD, Maxson PN, Schroeder DR, groups M: Neurologic complications after placement of cerebrospinal fluid drainage catheters and needles in anesthetized patients: Implications for regional anesthesia. Anesth Analg 1999; 88:388-92

12. Safi HJ, Hess KR, Randel M, Illiopoulos DC, Baldwin JC, Mootha RK, Shenaq SS, Sheinbaum R, Green T: Cerebrospinal fluid drainage and distal aortic perfusion: Reducing neurologic complications in repair of thoracoabdominal aortic aneurysm types I and II. J Vasc Surg 1996; 23:223-9

13. Chaney MA: Intrathecal and epidural anesthesia and analgesia for cardiac surgery. Anesth Analg 1997; 84:1211-21

CON:

Elizabeth Ling MD, MSc, FRCPC
Assistant Clinical Professor
Dept. of Anesthesia
McMaster University
Hamilton Health Sciences Corporation
Hamilton, ON

Cerebrospinal fluid drainage (CFSD) is frequently used in thoracoabdominal aorta aneurysm (TAAA) surgery to prevent the devastating complication of post-operative paraplegia. However, evidence for the potential benefit of CFSD from good quality human studies is inconclusive.¹ Only two randomized controlled trials (RCT) have been done; one advocating the use of CSFD² and the other failing to demonstrate any benefit.³ These trials and other non-randomized human studies advocating CSFD all contain major methodological limitations and provide inconclusive evidence on the potential benefits of CSFD.^1,4,5,6,7,8

The most recent RCT by Svensson et al.² studied CSFD and intrathecal papaverine in high-risk TAAA patients. After one third of the estimated sample size had been entered, the incidence of neurologic injury was statistically lower in the intervention group (P=0.039) and the study was terminated. Significance tests are a useful stopping criterion. However, when used in interim analysis, a more stringent significance level than P<0.05 must be set (i.e., P< 0.01) so that the cumulative (overall) P value is kept reasonable.⁹ Analyzing accumulating data
increases the chance of finding a treatment effect (type I error). It is unfortunate that this trial was terminated early.

The RCT by Crawford et al.³ studied high-risk type I and II TAAAs and failed to demonstrate a reduction in neurologic deficit using CSFD. However, CSFD was volume-limited to 50 ml and in only 20 of 46 patients was cerebrospinal fluid pressure reduced below 10 mmHg.

The practice of good medicine involves interpreting unbiased data from the published findings of good quality clinical trials. Case reports describe the potential benefits of postoperative CSFD for delayed-onset paraplegia.^10,11 Although enlightening, inferences made from such evidence are grossly inadequate. There are reported risks associated with the use of CSFD.¹² I am also aware of one case of meningitis associated with CSFD (unpublished).

It is possible that the critical pressure for initiating CSFD is variable and depends on a multitude of anatomical and physiological factors. This end-point must be clearly determined in order to maximize the potential relative risk reduction of postoperative neurological deficits. Is the critical threshold related to the intrinsic blood pressure? Should we drain at 10 or 15 mmHg? How long should we drain postoperatively? What are the relative benefits of other adjuncts (i.e., distal aortic perfusion)? I believe the theory behind CFSD is sound. Until we practice evidence-based medicine, can we really define the benefits of CFSD?

References:

1. Ling E, Arellano R. Systematic overview of the evidence supporting the use of cerebrospinal fluid drainage in thoracoabdominal aneurysm surgery for prevention of paraplegia. Anesth 2000; 93(4):1115-22

2. Svensson LG, Hess KR, D'Agostino RS, Entrup MH, Hreib K, Kimmel WA, Nadolny E, Shahian DM: Reduction of neurologic injury after high-risk thoracoabdominal aortic operation. Ann Thorac Surg 1998; 66:132-8

3. Crawford ES, Svensson LG, Hess KR, Shenaq SS, Coseli JS, Safi JH, Mohindra PK, Rivera V: A prospective randomized study of cerebrospinal fluid drainage to prevent paraplegia after high-risk surgery on the thoracoabdominal aorta. J Vasc Surg 1990; 13:36-46

4. Acher CW, Wynn MM, Hoch JR, Popic P, Archibald J, Turnipseed WD: Combined use of cerebral spinal fluid drainage and naloxone reduces the risk of paraplegia in thoracoabdominal aneurysm repair. J Vasc Surg 1994; 19:236-48

5. Acher CW, Wynn MM, Archibald J: Naloxone and spinal fluid drainage as adjuncts in the surgical treatment of thoracoabdominal and thoracic aneurysms. Surgery 1990; 108:755-61

6. Hollier LH, Money SR, Naslund TC, Procter CD, Buhrman WC, Marino RJ, Harmon DE, Kazmier FJ: Risk of spinal cord dysfunction in patients undergoing thoracoabdominal aortic replacement. Am J Surg 1992; 164:210-4

7. Safi HJ, Winnerkvist A, Miller CC, Iliopoulos DC, Reardon MJ, Espada R, Baldwin JC: Effect of extended cross-clamp time during thoracoabdominal aortic aneurysm repair. Ann Thorac Surg 1998; 66:1204-9

8. Safi HJ, Hess K, Randel M, Iliopoulos DC, Baldwin JC, Mootha RK, Shenaq SS, Sheinbaum R, Greene T: Cerebrospinal fluid drainage and distal aortic perfusion: Reducing neurologic complications in repair of thoracoabdominal aortic aneurysm types I and II. J Vasc Surg 1996; 23:223-9

9. Fleming TR, DeMets LD: Monitoring of clinical trials: Issues and recommendations. Control Clin Trials 1993; 14:183-97

10. Khong B, Yang H, Doobay B, Skala R: Reversal of paraparesis after thoracic aneurysm repair by cerebrospinal fluid drainage. Can J Anesth 2000; 47:992-5

11. Azizzadeh A, Huynh TT, Miller CC 3^rd, Safi HJ: Reversal of twice-delayed neurologic deficits with cerebrospinal fluid drainage after thoracoabdominal aneurysm repair: a case report and plea for a national database collection. J Vasc Surg 2000; 31:592-8

12. Basauri LT, Concha-Julio E, Selman JM, Cubillos P, Rufs J. Cerebrospinal fluid spinal lumbar drainage: indications, technical tips, and pitfalls. Crit Rev Neurosurg 1999; 26(9):21-7