Effects of Crystalloid and Colloid Resuscitation on Hemorrhage-Induced Vascular Hyporesponsiveness to Norepinephrine in the Rat.

摘要

We have shown previously that hemorrhagic hypotension is associated with a progressive development of vascular hyporeactivity to norepinephrine (NE). The present study investigated whether select crystalloid or colloid resuscitation fluids would ameliorate this effect. Method: Anesthetized male rats were hemorrhaged to and maintained at a mean arterial pressure (MAP) of 50 mm Hg for 60 minutes. Rats (n = 7 per group) were then resuscitated with lactated Ringer's (LR), 7.5% hypertonic saline (HS) for 1 hour followed by LR (HS-LR), Hespan, or Hextend to restore and maintain MAP to 70 mm Hg over 4 hours. Additional hemorrhaged groups were resuscitated with LR to the baseline MAP (LR-BL) or received no resuscitation. A sham hemorrhage group served as controls. The responses of MAP and the blood flow of the superior mesenteric, celiac, left renal, and left femoral arteries to NE (3 g/kg ad- ministered intravenously) were measured at BL (prehemorrhage); at the end of the hypotensive period; and at 1, 2, and 4 hours after resuscitation. Results: Hemorrhagic hypotension significantly (p less than 0.01) reduced the NE-induced pressor response in MAP and significantly reduced the contractile responses (reflected by the reduction of blood flow after NE administration) of the four arteries to NE. Hespan and Hextend infusion improved the NE response of MAP and the contractile responses of the observed arteries to NE significantly better than LR, HS-LR, or LR-BL. The colloids improved the vascular contractile responses to NE in the superior mesenteric and left femoral arteries and the pressor response of MAP to NE, to 80% to 90% of their basal response level compared with 40% to 60% with the crystalloid fluids (p less than 0.05). LR-BL infusion resulted in he- modilution, with no added benefit to vascular responsiveness.