This retrospective study examined the effectiveness of IV fluid resuscitation in treating hypotension (defined as a systolic arterial blood pressure [BP] <90 mm Hg as measured using a Doppler device) by examining emergency room records from 35 dogs with hypotension. Dogs in cardiogenic shock were excluded from the study. IV fluid resuscitation included isotonic crystalloid therapy (n = 23), synthetic colloid therapy (n = 1), or both (n = 11). IV fluid resuscitation in hypotensive dogs produced a significantly increased BP; 23 dogs regained a BP within normal range (>90 mm Hg) after receiving IV bolus fluid therapy within 1 hour of presentation. A crystalloid bolus was defined as a quarter to a third of a shock dose (80–90 mL/kg in dogs, 50–60 mL/kg in cats) with possible repeat doses of crystalloids. Dogs that had a positive response in BP to the IV fluid therapy were less likely to be euthanized. Unexpectedly, heart rate was not significantly decreased by IV fluid therapy.

Commentary
This retrospective study outlined important points about hypotensive dogs presenting to an urban emergency room. If there was no response to fluid resuscitation, as evidenced by normalization of Doppler BP, euthanasia was more likely. In addition, no difference was found in regard to responders and nonresponders between the type of fluid used for initial resuscitation; the dose of fluids administered did not differ between the 2 groups. Although normalization of heart rate may be regarded as a sign of adequate fluid resuscitation, this study showed no difference in mean heart rate before and after fluid resuscitation for either group. Although sepsis-induced hypotension may be less responsive to fluid therapy because of the effects of inflammatory mediators on vascular tone, no difference was found between either group based on a septic diagnosis. Here, survival to discharge was only 26%, warranting a guarded prognosis.—Lisa L. Powell, DVM, DACVECC

Source
Effectiveness of intravenous fluid resuscitation in the emergency room for treatment of hypotension in dogs: 35 cases (2000-2010). Silverstein DC, Kleiner J, Drobatz KJ. JVECC 22:666-673, 2012.