Prevention of spinal cord ischemia during aortic cross-clamping of thoracic aorta--use of somatosensory evoked potential
Sekine, S.
Nihon Kyobu Geka Gakkai 36(12): 2598-2607
1988
ISSN/ISBN: 0369-4739 PMID: 3235864 Document Number: 315292
Paraplegia, as a complication of thoracic surgery requiring temporary aortic occlusion, has not been prevented entirely despite various protective procedures. Using somatosensory evoked potential (SEP) reflecting long-truct neural conduction, we evaluated a spinal cord of function during aortic occlusion (1) without any adjunct measure and (2) with the use of temporary external bypass for preventing spinal cord injury. Five dogs were subjected to exclusion of the entire descending aorta for 30 minutes without any adjunct. All demonstrated immediate loss of SEP within 15 minutes, with the decrease of femoral artery pressure (FAP) to 22.0 .+-. 4.6 mmHg. One of 5 dogs could not recover SEP by 30 minutes after reperfusion. In another 16 dogs, entire descending aorta was excluded with all intercostal arteries ligated following institution of temporary external bypass from aortic arch to abdominal aorta. Bypass flow (BF) was then altered at 30 minutes interval with serial SEP monitoring so that abdominal aortic flow (AbF)/cardiac output (CO) of 0.3 and 0.2 was maintained. Of 8 dogs with normothermia (Group I), SEP was maintained in 7 at AbF/CO = 0.3 and in only 2 at AbF/CO = 0.2, with FAP decrease to 46.1 .+-. 10.9 mmHg and 30.6 .+-. 8.1 mmHg respectively. On the other hand, 8 dogs with hypothermia (Group II), SEP was maintained in all dogs at AbF/CO = 0.3 and in 4 at AbF/CO = 0.2, with FAP decrease to 49.3 .+-. 9.9 mmHg and 36.5 .+-. 11.4 mmHg respectively. However, loss of SEP occurred in the majority of cases with a distal aortic pressure of less than 45 mmHg na BF/CO of less than 45% in both groups. Therefore, moderate hypothermia (30.degree. C) was not demonstrated to be efficient in terms of prevention of spinal cord injury during temporary aortic occlusion. Maintenance of distal aortic pressure greater than 50 mmHg and BF greater than 45% of CO will preserve spinal blood flow in the absence of critical intercostal occlusion. Failure to institute measures to reverse ischemic SEP changes may result in paraplegia.