Isolated Brain Trauma in Cats Triggers Rapid Onset of Hypovolemia.

Abstract

BACKGROUND: Hemodynamic instability responsive to fluid resuscitation is common after a traumatic brain injury (TBI), also in the absence of systemic hemorrhage. The present study tests if an isolated severe TBI induces a decrease in plasma volume (PV). METHODS: The study was performed in three groups of anesthetized and tracheostomized male cats (n&#xa0;=&#xa0;21). In one group (n&#xa0;=&#xa0;8), the cats were prepared with a cranial borehole (10&#xa0;mm i.d) used to expose the brain to a fluid percussion brain injury (FPI) (1.90-2.20&#xa0;bar), and two smaller cranial boreholes (4&#xa0;mm i.d) for insertion of an intracranial pressure (ICP) and a microdialysis catheter. To differentiate the effect of FPI from that of the surgical preparation, a sham group was exposed to the same surgical preparation but no FPI trauma (n&#xa0;=&#xa0;8). A control group had no brain trauma and no surgical preparation (n&#xa0;=&#xa0;5). PV was determined by aI-albumin dilution technique. PV, electrolytes, pH, BE (base excess), hematocrit (Hct), PO, and PCOwere measured at baseline and after 3&#xa0;h. Mean arterial pressure (MAP) was measured continuously. ICP was measured in the FPI and the sham group. RESULTS: In the FPI group, PV decreased by 11.2&#xa0;mL/kg from 31.7&#xa0;mL/kg (p&#xa0;<&#xa0;0.01) with a simultaneous increase in Hct and decrease in pH. In the sham group, PV decreased by 5.7&#xa0;mL/kg from 32.7&#xa0;mL/kg (p&#xa0;<&#xa0;0.01). The control group showed no PV reduction. CONCLUSIONS: The results support that an isolated severe head trauma triggers a significant and rapid reduction in PV, most likely due to vascular leak.