Impaired arteriolar constriction to hemorrhage in obese Zucker rats with orthopedic trauma

Abstract

During hemorrhage, increased sympathetic activity and vasoconstrictor responses in skeletal muscle occurs to improve blood pressure. Obese patients with orthopedic trauma and hemorrhage exhibit higher mortality than nonobese patients. We hypothesize that the vasoconstrictor responses in skeletal muscle to hemorrhage is attenuated in animal model of obesity with orthopedic trauma. Lean (LZ) and obese Zucker rats (OZ) (11–13 wk) were used to test this hypothesis. Orthopedic trauma was induced in both hindlimbs with a soft tissue injury and local injection of bone components. One to three days after orthopedic trauma, the spinotrapezius muscle was prepared for microcirculatory observation and the vasoconstrictor responses of arcade arterioles to phenylephrine and hemorrhage were measured. The arteriolar tone was not different between control LZ and OZ (67 ± 2%, 61 ± 2%, respectively). Orthopedic trauma resulted in a decreased arteriolar tone (39 ± 6%) and attenuated responses to phenylephrine in OZ (Figure 1) with no effect in LZ. Hemorrhage resulted in arteriolar constriction in control animals and trauma treated-LZ, whereas in trauma treated-OZ the vasoconstrictor response to hemorrhage was absent. These results suggest that orthopedic trauma blunts the adrenergic vasoconstriction in OZ via a loss of tone during hemorrhage. Figure 1Open in figure viewerPowerPoint