Changes of motor evoked potentials during descending thoracic and thoracoabdominal aortic surgery with deep hypothermic circulatory arrest.
BACKGROUND
Paraplegia is a serious complication of descending and thoracoabdominal aortic aneurysms (dTAAs and TAAAs) surgery. Motor evoked potentials (MEPs) enable monitoring the functional integrity of motor pathways during dTAA and TAAA surgery. Although MEPs are sensitive to temperature changes, there are few human data on changes of MEPs during mild and deep hypothermia. Therefore, we investigated changes of MEPs in deep hypothermic circulatory arrest (DHCA) in dTAA and TAAA surgery.


METHODS
Fifteen consecutive patients undergoing dTAA and TAAA surgery using DHCA were enrolled. MEPs were elicited and recorded during each degree Celsius change in nasopharyngeal temperature during both the cooling and rewarming phases. Hand and leg skin temperature were also recorded simultaneously.


RESULTS
In the cooling phase MEP amplitude decreased lineally in both the hand and leg. The MEP disappeared at ~16°C in both the hand and leg in 10 of 15 patients, but was still elicited in 5 patients. In the rewarming phase MEP in the hand recovered before the temperature reached 20°C for eight patients and 25°C for the other seven patients. In contrast, MEP in the leg recovered below 20°C for two patients and 30°C for three patients. For the other eight patients MEP waves did not recover during the rewarming phase.


CONCLUSIONS
In the cooling phase of DHCA, MEP disappeared at ~16°C in some patients but was still elicited in others. MEP recovered below 25°C in the hand. Recovery of MEP in the leg was, however, extremely variable.
Department of Anesthesiology, National Cerebral and Cardiovascular Center, 5-7-1 Fujishirodai, Suita, Osaka 565-8565, Japan.
Masahide
M
Shinzawa
Kenji
K
Yoshitani
Kenji
K
Minatoya
Tomoya
T
Irie
Hitoshi
H
Ogino
Yoshihiko
Y
Ohnishi
D000328:Adult; D000368:Aged; D001013:Aorta, Thoracic / Q000503:physiopathology / Q000601:surgery*; D017545:Aortic Aneurysm, Thoracic / Q000503:physiopathology / Q000601:surgery*; D050792:Circulatory Arrest, Deep Hypothermia Induced / Q000009:adverse effects / Q000379:methods*; D004525:Efferent Pathways / Q000502:physiology; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D016343:Monitoring, Intraoperative / Q000379:methods; D017694:Rewarming / Q000379:methods; D012881:Skin Temperature / Q000502:physiology; D014656:Vascular Surgical Procedures / Q000009:adverse effects / Q000379:methods*