title: Moderate hypothermia increased the incidence of delayed paralysis through activation of the spinal microglia in an aortic cross-clamping rat model.
abstract: BACKGROUND
  Hypothermia reduces immediate paralysis during surgical repair of aortic aneurysms. However, it is unknown what the impact of hypothermia is on delayed paralysis, a serious complication of this type of surgery.
  
  
  METHODS
  Sprague-Dawley rats were subjected to occlusion of the descending aorta at different duration under normothermia (38.0±0.5) or hypothermia (33.0±0.5°). Neurologic function was assessed. Motor neuron number, glial activation, and cytokine expression in the spinal cord were examined. Minocycline was administered perioperatively by intraperitoneal injection in the rats subjected to the aorta occlusion.
  
  
  RESULTS
  In contrast to normothermia conditions at which immediate paralysis occurred when the duration of aorta occlusion exceeded 11.5min, hypothermia did not induce immediate paralysis if the duration of aorta occlusion was less than 41min. However, delayed paralysis was developed when the duration of aorta occlusion exceeded 18min, and reached peak level when the duration of aorta occlusion was 40min at hypothermia condition. The number of motoneurons was significantly decreased (P<0.05) at 30h postoperation. In addition, microglia was activated, and interleukin-1β and interleukin-6 levels were upregulated, both of which were co-localized in microglia at 24h postoperation in the hypothermia group. Minocycline treatment attenuated the incidence and degree of paralysis but did not decrease the mortality.
  
  
  CONCLUSIONS
  Hypothermia, a neuroprotective strategy in cardiothoracic surgery, increased the incidence of delayed paralysis through activation of spinal microglia and cytokines. Blocking the activated microglia may be a potential intervention to prevent the incidence of delayed paralysis.
authors.affiliation: Department of Anesthesia, The Second Xiangya Hospital of Central South University, Ren-Min Road 139#, Changsha 410011, China.; Department of Anesthesiology, The Affiliated Hospital of Guilin Medical University, Lequn Road 15#, Guilin 54100, China.
authors.forename: Liang
authors.initials: L
authors.lastname: He
authors.affiliation: Department of Anesthesia, The Second Xiangya Hospital of Central South University, Ren-Min Road 139#, Changsha 410011, China.
authors.forename: Jun-Mei
authors.initials: JM
authors.lastname: Xu
authors.affiliation: Department of Anesthesia, The Second Xiangya Hospital of Central South University, Ren-Min Road 139#, Changsha 410011, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Li
authors.affiliation: Department of Anesthesia, The Second Xiangya Hospital of Central South University, Ren-Min Road 139#, Changsha 410011, China.
authors.forename: Feng
authors.initials: F
authors.lastname: Zhong
authors.affiliation: Department of Anesthesia, The Second Xiangya Hospital of Central South University, Ren-Min Road 139#, Changsha 410011, China.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Liu
authors.affiliation: Department of Anatomy and Neurobiology, Xiangya School of Medicine, Central South University, Changsha 410000, China.
authors.forename: Chang-Qi
authors.initials: CQ
authors.lastname: Li
authors.affiliation: Department of Anesthesia, The Second Xiangya Hospital of Central South University, Ren-Min Road 139#, Changsha 410011, China.. Electronic address: xyeyyrupingdai@gmail.com.
authors.forename: Ru-Ping
authors.initials: RP
authors.lastname: Dai
mesh_terms: D000818:Animals; D001013:Aorta, Thoracic / Q000378:metabolism*; D001014:Aortic Aneurysm / Q000378:metabolism* / Q000473:pathology; D004195:Disease Models, Animal; D007036:Hypothermia, Induced / Q000379:methods*; D015994:Incidence; D008297:Male; D017628:Microglia / Q000378:metabolism*; D010243:Paralysis / Q000378:metabolism* / Q000473:pathology / Q000517:prevention & control; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley; D013116:Spinal Cord / Q000378:metabolism*; D013997:Time Factors
keywords: Delayed paralysis; Microglia; Minocycline; Moderate hypothermia; Spinal cord ischemia