Hypoproteinemia does not alter plasma volume expansion in response to a 0.9% saline bolus in awake sheep.

OBJECTIVE

To test the hypothesis that hypoproteinemia reduces plasma volume expansion produced by a bolus of crystalloid solution given to awake sheep.

DESIGN

Prospective and observational.

SETTING

Laboratory.

SUBJECTS

Five female merino sheep (n = 5) weighing 37 ± 3 kg were anesthetized.

INTERVENTIONS

Each animal was subjected to a 5-day test period: day 1: 50 mL/min 0.9% saline infusion over 20 mins. Days 2-4: daily plasmapheresis and replacement of the shed plasma with 6 L of 0.9% saline were performed in increments.

MEASUREMENTS AND MAIN RESULTS

Fractional plasma volume expansion after rapid infusion of saline on days 1 and 5 was calculated from changes in hemoglobin concentration. There was a significant reduction in total plasma protein concentration after plasmapheresis (p < .05). Colloid osmotic pressures were also significantly lowered (p < .05). A crystalloid infusion of 0.9% saline did not alter any of these values compared with baseline. The hemodynamic measurements did not show significant differences between the experiments. The plasma volume expansion reached approximately 20% at the end of infusion and stayed at 10-15% during the experiments. No difference was found in plasma volume expansion produced by a bolus of 50 mL/min of 0.9% in the hypoproteinemic state when compared with the euproteinemic state (p = .61). No difference in cumulative urinary output was found between the two states.

CONCLUSIONS

In contrast to our hypothesis, severe acute hypoproteinemia does not reduce plasma volume expansion in response to 50 mL/min 0.9% saline infusion in nonspleenectomized sheep when compared with the resultant plasma volume expansion after a 50 mL/min of 0.9% infusion in the euproteinemic state.