title: Moderate and deep hypothermia produces hyporesposiveness to phenylephrine in isolated rat aorta.
abstract: BACKGROUND
  Moderate and severe hypothermia with cardiopulmonary bypass during aortic surgery can cause some complications such as endothelial cell dysfunction or coagulation disorders. This study found out the difference of vascular reactivity by phenylephrine in moderate and severe hypothermia.
  
  
  METHODS
  Preserved aortic endothelium by excised rat thoracic aorta was sectioned, and then down the temperature rapidly to 25℃ by 15 minutes at 38℃ and then the vascular tension was measured. The vascular tension was also measured in rewarming at 25℃ for temperatures up to 38℃. To investigate the mechanism of the changes in vascular tension on hypothermia, NG-nitro-L-arginine methyl esther (L-NAME) and indomethacin administered 30 minutes before the phenylephrine administration. And to find out the hypothermic effect can persist after rewarming, endothelium intact vessel and endothelium denuded vessel exposed to hypothermia. The bradykinin dose-response curve was obtained for ascertainment whether endothelium-dependent hyperpolarization factor involves decreasing the phenylnephrine vascular reactivity on hypothermia.
  
  
  RESULTS
  Fifteen minutes of the moderate hypothermia blocked the maximum contractile response of phenylephrine about 95%. The vasorelaxation induced by hypothermia was significantly reduced with L-NAME and indomethacin administration together. There was a significant decreasing in phenylephrine susceptibility and maximum contractility after 2 hours rewarming from moderate and severe hypothermia in the endothelium intact vessel compared with contrast group.
  
  
  CONCLUSIONS
  The vasoplegic syndrome after cardiac surgery might be caused by hypothermia when considering the vascular reactivity to phenylephrine was decreased in the endothelium-dependent mechanism.
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, Catholic University of Daegu School of Medicine, Korea.
authors.forename: Jun Woo
authors.initials: JW
authors.lastname: Cho
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, Catholic University of Daegu School of Medicine, Korea.
authors.forename: Chul Ho
authors.initials: CH
authors.lastname: Lee
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, Catholic University of Daegu School of Medicine, Korea.
authors.forename: Jae Seok
authors.initials: JS
authors.lastname: Jang
authors.affiliation: Department of Cardiovascular and Thoracic Surgery, Catholic University of Daegu School of Medicine, Korea.
authors.forename: Oh Choon
authors.initials: OC
authors.lastname: Kwon
authors.affiliation: Department of Anesthesiology, Catholic University of Daegu School of Medicine, Korea.
authors.forename: Woon Seok
authors.initials: WS
authors.lastname: Roh
authors.affiliation: Department of Anesthesiology, Catholic University of Daegu School of Medicine, Korea.
authors.forename: Jung Eun
authors.initials: JE
authors.lastname: Kim
keywords: Endothelium-dependent hyperpolarization factor; Epoprostenol; Hypothermia; Nitric oxide; Phenylephrine