Small-volume resuscitation restores hemorrhage-induced microcirculatory disorders in rat pancreas

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Abstract
Objectives Pancreatic hypoxia/ischemia, as a consequence of shock-induced microcirculatory failure, is considered a causative facter in the initiation and/or progression of pancreatic tissue injury. The aim of this study was to compare the effects of ``small-volume resuscitation'' with conventional isovolemic colloid and hypervolemic crystalloid resuscitation on pancreatic microcirculation after hemorrhagic shock. Design Randomized, controlled intervention trial. Setting University laboratory. Subjects Twenty-three male Sprague-Dawley rats anesthetized with a-chloralose and mechanically ventilated. Interventions Rats subjected to 1 hr of hemorrhagic shock (mean arterial pressure of 40 mm Hg) were resuscitated with lactated Ringer's solution (four-fold shed volume/20 mins), 10% hydroxyethyl starch (shed volume/5 mins), or 7.2% sodium chloride-10% hydroxyethyl starch (10% shed volume/2 mins). Measurements and Main Results The microcirculation of pancreatic acinar tissue was studied by means of intravital fluorescence microscopy and laser Doppler flowmetry. At 1 hr after resuscitation, mean arterial pressure, pancreatic capillary erythrocyte velocity, and erythrocyte flux were found to be significantly increased when compared with those values in the shock state. However, mean arterial pressure, pancreatic capillary erythrocyte velocity, and erythrocyte flux did not completely return to preshock values, regardless of the type of fluid used for resuscitation. At 15 mins and 1 hr after resuscitation, shock-induced capillary perfusion failure (reduction of functional capillary density) was restored to 91% to 94% of baseline values in all groups. Pancreatic capillary narrowing, indicating microvascular endothelial cell swelling, was abolished by resuscitation with both isotonic hydroxyethyl starch and hypertonic hydroxyethyl starch (p less than .05 vs. lactated Ringer's solution). Conclusions Despite replacement of only 10% of actual blood loss, small-volume resuscitation with hypertonic hydroxyethyl starch is as effective as the ten-fold volume of isotonic hydroxyethyl starch and, due to prevention of microvascular endothelial cell swelling, superior to the 40-fold volume of isotonic lactated Ringer's solution in regard to restoration of the shock-induced microcirculatory disturbances of rat pancreatic acinar tissue. (Crit Care Med 1996; 24:445-450)

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