Ann Thorac Surg 1999;67:1595
© 1999 The Society of Thoracic Surgeons
Invited Commentaries
Tam T.T. Huynh, MD,
Hazim J. Safi, MDa
a Baylor College of Medicine, The Methodist Hospital, 6550 Fannin, Smith Tower, Suite #1603, Houston, TX 77030, USA
e-mail: hsafi{at}bcm.tmc.edu.
Invited commentary
The development of neurologic deficits remains the most devastating complication in patients undergoing thoracoabdominal aortic aneurysm repair. Despite much effort spent in the search for the optimal method of spinal cord protection, paraparesis and paraplegia still occur in 0.5% of 38% of such cases. Recent advances in the use of adjunctive therapy, however, have had an impact on this dreadful complication. In a rabbit model, Parrino and associates have elegantly demonstrated a near complete prevention of neurologic deficits with hypothermic saline retrograde perfusion containing adenosine. The authors clearly showed that retrograde venous perfusion of the spinal cord with cold saline, or cold saline and adenosine improved the objective neurologic scores, as compared with no perfusion, or warm saline perfusion. However, the effects of the addition of adenosine, a cyclic adenosine-monophosphate (cAMP) activator, to the perfusate were less clear. The neurologic scores for subjects that received cold saline with adenosine were not significantly different from those without adenosine, as analyzed by the Tukey’s HSD multiple comparisons test. The improved neurologic outcome with adenosine over cold saline perfusion alone was based on contrast analysis, a statistical manipulation that would support, at best, a weak significance. It is noteworthy that the lower mean arterial pressure induced by perfusion with adenosine may have protective effect on the spinal cord. Nevertheless, adenosine is known to be involved in a diverse series of physiological responses such as vascular smooth muscle relaxation, neurotransmitter release, platelet and white blood cell function, cardiac conduction, and contractility, and its potential role in spinal cord protection would deserve more studies.
The concept of spinal cord protection using retrograde perfusion is novel and should be further explored. However, retrograde venous perfusion of the spinal cord alone may not be sufficient for complete spinal cord protection, as we have shown in an experimental canine model. The use of adjunct interventions such as perioperative cerebrospinal fluid drainage with, or without distal aortic perfusion, has significantly reduced the development of neurologic deficits in our patients undergoing repair of thoracoabdominal aneurysms with extent I, II, III, and IV. In our hand, this practice has eliminated immediate neurologic complications in patients with extent I thoracoabdominal aneurysms. Repair of extent II thoracoabdominal aneurysms remains the main culprit of neurologic impairment. However, any new methods to protect the spinal cord during repair of thoracoabdominal aneurysms should be studied prospectively, as the previously published data with the "clamp-and-sew" technique do not reflect the current practice. Further research in spinal cord protection is, therefore, critical for continued improvement in the outcome of thoracoabdominal aortic surgery.
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Spinal cord protection during aortic cross-clamping using retrograde venous perfusion
- Patrick E. Parrino, Irving L. Kron, Scott D. Ross, Kimberly S. Shockey, Michael J. Fisher, John R. Gaughen, Jr, John A. Kern, and Curtis G. Tribble
Ann. Thorac. Surg. 1999 67: 1589-1594.
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