Ann Thorac Surg 2001;72:85
© 2001 The Society of Thoracic Surgeons
Invited commentary
John C. Laschinger, MDa
a Midatlantic Cardiovascular Associates, P.A., 7505 Osler Dr, Suite 410, Towson, Maryland 21204, USA
e-mail: johnlaschinger{at}home.com
Wada and associates are to be congratulated for their outstanding results achieved in patients undergoing repair of aneurysms of the descending thoracic and thoracoabdominal aorta. The authors describe a retrospective series which, over the last 17 years, has employed the routine use of somatosensory evoked potential monitoring (SEP), cerebrospinal fluid pressure monitoring (CSFP), and mean distal aortic pressure monitoring (MDAP). The authors use the difference between the latter two measurements to calculate the spinal cord perfusion pressure (SCPP). Their results show that they were successful in preventing paraplegia in patients in whom SCPP was maintained at greater than 40 mm Hg who had no significant ischemic changes in spinal cord function as detected by SEP monitoring. Specifically, the only two patients in whom paraplegia was encountered in this series were those in whom a passive shunt was used, where distal perfusion pressure could not be controlled and spinal cord perfusion pressure could not be maintained over 40 mm Hg. In both patients, neurologic injury was predicted by intraoperative SEP monitoring. Paraplegia was not observed in any patient who had normal SEPs and SCPP maintained during the cross clamp interval.
The last 20 years has seen a striking evolution in the surgical management of aneurysms of the descending thoracic aorta. The standard surgical approach to these patients has been a "clamp and sew" technique. Although this technique is associated with good results in skilled hands, current studies increasingly support the use of one or more adjuncts in an attempt to reduce the incidence of spinal cord injury following these procedures. The most common is provision of distal aortic perfusion using a temporary left atrial femoral artery bypass or femoral vein to femoral artery bypass with an oxygenator in line. Although passive shunts are still used by some, their disadvantages, as illustrated by this article, is the inability to control distal perfusion pressure resulting in a higher incidence of paraplegia. In addition, CSF fluid drainage, both intraoperatively and postoperatively is now being employed by numerous groups to decrease the incidence of both intraoperative and delayed paraplegia. Finally, motor evoked potentials (MEP) have been used successfully and may, in fact, be more accurate than SEP’s in detecting intraoperative spinal cord ischemic dysfunction.
This article confirms several important observations that have been made by numerous groups over the past 20 years. The most striking of these is the importance of maintaining spinal cord perfusion during procedures on the descending thoracic aorta. Although much attention has been paid to the reimplantation of intercostals during thoraco-abdominal aortic procedures, it is striking to this author how rarely that is truly indicated (as directed intraoperatively by SEP/MEP findings) if attention is paid to maintaining SCPP by manipulating MDAP and CSFP during these procedures. In addition, postoperative delayed paraplegia has been prevented and in several cases, reversed by drainage of cerebral spinal fluid and by maintaining the CSF pressure below 10 mm Hg. Although, likely to be a controversial recommendation, it now seems we are accumulating sufficient amount of information to recommend that the vast majority of these procedures when performed electively, be done in institutions where invasive monitoring, including SEP/MEPs, CSFP measurements, and MDAP measurements can be performed in patients undergoing these procedures. The routine use of postoperative CSFP monitoring is also recommended along with CSF drainage as needed should delayed paraplegia result.
Related Article
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Prevention and detection of spinal cord injury during thoracic and thoracoabdominal aortic repairs
- Torazo Wada, Hideki Yao, Takashi Miyamoto, Sukemasa Mukai, and Mitsuhiro Yamamura
Ann. Thorac. Surg. 2001 72: 80-84.
[Abstract]
[Full Text]
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