The effect of normal saline resuscitation on vital organ blood flow in septic sheep

Objective: To study the effect of resuscitation with normal saline on vital organ blood flow and renal function in sepsis. Design and setting: Randomized controlled cross-over animal study in the animal laboratory of university physiology institute. Subjects: Six merino cross-ewes. Interventions: Chronic implantation of flow probes around aorta, coronary, renal and mesenteric arteries. Intravenous administration of live Escherichia coli. Random allocation to normal saline resuscitation ( 20 ml/kg over 15 min) or observation ( control) for 210 min. Continuous measurement of central haemodynamics, organ blood flow and renal function. Results: Live E. coli induced hyperdynamic sepsis with oliguria (28.3 +/- 12.6 to 16.7 +/- 11.9ml/30min) and reduced creatinine clearance (87.9 +/- 24.5 to 44.3 +/- 34.5ml/min). During this septic state mesenteric, coronary and renal blood flow increased. During the first hour ( early effect) after saline resuscitation, central venous pressure, cardiac output, stroke volume, coronary blood flow, mesenteric blood flow, urine output and creatinine clearance increased, but there was no change in renal blood flow. In the following 2 h these increments were significantly attenuated, but urine output and creatinine clearance remained greater than controls; renal blood flow decreased slightly and the fractional excretion of sodium increased significantly. Conclusion: In hyperdynamic sepsis resuscitation with normal saline increases central venous pressure, cardiac output, mesenteric blood flow, urine output, creatinine clearance, and fractional excretion of sodium despite a lack of effect on renal blood flow. These effects, however, are transient.