Once the fluid therapy plan is underway, ongoing assessment is critical. When an adequate amount of fluids has been administered and reasonable resuscitation endpoints have not been reached, several causes should be considered: inadequate volume administration, ongoing hemorrhage, third body fluid spacing, heart disease, severe vasodilation, vasoconstriction, hypoglycemia, hypokalemia, arrhythmias, or brain pathology. These variables should be rapidly assessed and corrected. If a central venous pressure (CVP) line is available, it should be checked to see if CVP is near the endpoints assigned in Table 3: Fluid Therapy: Endpoint Resuscitation. If not, or if no CVP is available, a fluid challenge can be given. This typically consists of a bolus (10–15 mL/kg) of crystalloids and a bolus (5 mL/kg) of hetastarch. If the perfusion parameters improve with this challenge, then the likely cause of the nonresponsive shock is inadequate volume, and colloids are titrated to reach the desired endpoints.
If fluid volume appears adequate and the patient is still hypotensive, vasopressors can be used. Oxyglobin® can be given at the dosages listed above if it has not yet been used. If stroma-free hemoglobin fails to increase the blood pressure, then dopamine is administered at 5–15 mg/kg/min as a constant rate of infusion. This is weaned once the blood pressure has stabilized.
Last full review/revision March 2012 by Rebecca Kirby, DVM, DACVIM, DACVECC; Andrew Linklater, DVM, DACVECC