The influence of haemorrhage and fluid resuscitation with either Plasma-Lyte A or Ringer's Lactate in Beagle dogs under sevoflurane anaesthesia-part 1: Macrocirculation.

Both crystalloid solutions restore cardiac output; MAP should not be used alone to assess fluid responsiveness.

This randomized, blinded experimental study compared macrocirculatory effects of two crystalloid solutions—Plasma-Lyte A (PA) and Ringer's Lactate (RL)—for fluid resuscitation following controlled hemorrhage in 12 anesthetized Beagle dogs. Dogs underwent controlled blood removal (30 mL/kg over 15 minutes) followed by two sequential fluid boluses (10 mL/kg each) of either PA or RL. Cardiac output (CO), mean arterial blood pressure (MAP), and heart rate were measured at baseline, after hemorrhage, and after each fluid bolus. Both solutions significantly increased CO compared to hypovolemia, with RL showing slightly greater increases at both boluses. However, only RL produced significant MAP increases at both boluses, while PA demonstrated no significant MAP changes. The authors conclude that both fluids effectively restore cardiac output, but emphasize that MAP changes should not be used as surrogate markers for assessing fluid responsiveness or tissue perfusion.

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