Effect of intravenous administration of lactated Ringer's solution or hetastarch for the treatment of isoflurane-induced hypotension in dogs.

Objective: To determine the effect of IV administration of crystalloid (lactated Ringer's solution [LRS]) or colloid (hetastarch) fluid on isoflurane-induced hypotension in dogs.

Animals: 6 healthy Beagles.

Procedures: On 3 occasions, each dog was anesthetized with propofol and isoflurane and instrumented with a thermodilution catheter (pulmonary artery). Following baseline assessments of hemodynamic variables, end-tidal isoflurane concentration was increased to achieve systolic arterial blood pressure (SABP) of 80 mm Hg. At that time (0 minutes), 1 of 3 IV treatments (no fluid, LRS [80 mL/kg/h], or hetastarch [80 mL/kg/h]) was initiated. Fluid administration continued until SABP was within 10% of baseline or to a maximum volume of 80 mL/kg (LRS) or 40 mL/kg (hetastarch). Hemodynamic variables were measured at intervals (0 through 120 minutes and additionally at 150 and 180 minutes in LRS- or hetastarch-treated dogs). Several clinicopathologic variables including total protein concentration, PCV, colloid osmotic pressure, and viscosity of blood were assessed at baseline and intervals thereafter (0 through 120 minutes).

Results: Administration of 80 mL of LRS/kg did not increase SABP in any dog, whereas administration of
Conclusions And Clinical Relevance: Results indicated that IV administration of hetastarch rather than LRS is recommended for the treatment of isoflurane-induced hypotension in dogs.