A MODEL FOR EVALUATING THE EFFECTS OF BLUNT SKELETAL MUSCLE TRAUMA ON MICROVASCULAR PERMEABILITY AND PLASMA VOLUME IN THE RAT

Abstract

The objective of the present study was to develop an experimental model suitable for studying the effects of a nonhemorrhagic soft tissue trauma on plasma volume (PV) and microvascular permeability. Anesthetized Sprague-Dawley rats were exposed to a sham procedure or a laparotomy followed by a standardized trauma to the abdominal rectus muscle. We evaluated the effects of trauma on transcapillary escape rate and on PV (3 h after trauma) using 125I-albumin as tracer and on edema formation in the traumatized muscle with a wet- versus dry-weight method. The effects of the trauma on the cytokines IFN-gamma, IL-4, IL-6, IL-10, and TNF-alpha were investigated 1 and 3 h after trauma in a separate group. Transcapillary escape rate was 13.9% per hour in the sham animals compared with 18.5% per hour in the traumatized animals (P < 0.05). Because arterial and venous blood pressures were not altered by the trauma, the change in transcapillary escape rate most likely reflects a change in microvascular permeability. Plasma volume decreased from 42 mL/kg at baseline to 31 mL/kg at the end of the experiments (P < 0.05) in the trauma group, whereas PV remained unchanged in the sham group. Only 15% of the PV loss could be referred to edema in the traumatized muscle. Trauma induced a significant increase in IL-6 and IL-10 after 1 h. We conclude that the present nonhemorrhagic trauma induces an increase in microvascular permeability in the traumatized tissue and in other parts of the body, resulting in hypovolemia. The model may be used for the evaluation of different therapeutic interventions aimed at the correction of hypovolemia.