title: Hypothermic retrograde jugular vein flush in heatstroke rats provides brain protection by maintaining cerebral blood flow but not by hemodilution.
abstract: OBJECTIVE
  To determine the fundamental mechanism of brain protection by hypothermic retrograde jugular vein flush (HRJVF) in heatstroke rats.
  
  
  METHODS
  Randomized, controlled, and prospective study.
  
  
  METHODS
  University physiology research laboratory.
  
  
  METHODS
  Sprague-Dawley rats (270-320 g, males).
  
  
  METHODS
  Rats were randomized into four groups as follows: a) normothermic control (NC, n = 8); b) heatstroke rats without cold saline delivery (HS, n = 8); c) heatstroke rats treated with cold saline via femoral vein (HS+F, n = 8); and d) heatstroke rats treated with HRJVF (HS+J, n = 8). Right external jugular vein and right femoral vein were cannulated in each rat. The cannulation in the jugular vein was with cranial direction. To produce heatstroke, rats were placed in a chamber with an ambient temperature of 43 degrees C. The cold saline (4 degrees C, 1.7 mL/100 g) was delivered via the cannula in either the femoral vein or jugular vein immediately after the onset of heatstroke. Glutamate release in the brain, cerebral blood flow (CBF), and hematocrit of arterial blood were determined.
  
  
  RESULTS
  After onset of heatstroke, HRJVF significantly decreased the glutamate release. In contrast, cold saline delivery via femoral vein could only delay the elevation of glutamate release in the brain. The CBF of HS and HS+F rats decreased rapidly after the onset of heatstroke, but the CBF of HS+J rats was initially elevated by HRJVF and was maintained at baseline 30 mins after onset of heatstroke. Hematocrit in all the rats did not change after testing.
  
  
  CONCLUSIONS
  HRJVF protects the brain by maintaining cerebral blood flow in rats after heatstroke. To preserve brain function and prolong survival after severe heatstroke, maintenance of cerebral blood flow is important in the management of heatstroke.
authors.affiliation: Institute of Clinical Medicine, National Yang-Ming Universityand Emergency Department, Taipei Veterans General Hospital, Taiwan. yswen@vghtpe.gov.tw
authors.forename: Yi-Szu
authors.initials: YS
authors.lastname: Wen
authors.forename: Mu-Shung
authors.initials: MS
authors.lastname: Huang
authors.forename: Mao-Tsun
authors.initials: MT
authors.lastname: Lin
authors.forename: Chen-Hsen
authors.initials: CH
authors.lastname: Lee
mesh_terms: D000818:Animals; D001921:Brain / Q000502:physiology*; D002560:Cerebrovascular Circulation / Q000502:physiology*; D018883:Heat Stroke / Q000628:therapy*; D006438:Hemodilution; D007036:Hypothermia, Induced; D007601:Jugular Veins; D008297:Male; D011446:Prospective Studies; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley