Hypertonic saline resuscitation abrogates neutrophil priming by mesenteric lymph

Objective: Neutrophil (PMN) priming after hemorrhagic shock is predictive of the subsequent development of multiple organ failure, but the mechanism remains unknown. Recently, we and others have demonstrated that mesenteric lymph from shock animals resuscitated with lactated Ringer's solution (LR) is not only a potent PMN priming agent but also causes lung injury. Work by others has shown that resuscitation with hypertonic saline (HTS) protects animals from lung injury after hemorrhagic shock. Therefore, we hypothesize that resuscitation with HTS will abolish PMN priming by postshock mesenteric lymph. Methods: After mesenteric lymph duct catheterization, male rats underwent hemorrhagic shock (mean arterial pressure of 40 mm Hg for 90 minutes) and resuscitation with shed blood plus either LR (2x volume of shed blood) or 4 mL/kg of 7% HTS (isonatremic), Priming for superoxide by PMN was measured after fMLP (1 mu M) activation. Results: Shock significantly decreased mesenteric lymph flow from preshock levels in both groups, LR resuscitation produced significantly more mesenteric lymph than HTS resuscitation. Mesenteric lymph from LR animals primed PMN for superoxide production, whereas, HTS eliminated this priming. Conclusion: I-ITS not only decreases postshock mesenteric lymph production, it eliminates PMN priming by mesenteric lymph, suggesting a mechanism for the beneficial effects of HTS resuscitation.