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J Surg Res. 2006 Mar;131(1):7-14. Epub 2005 Dec 2.

Adrenergic drugs alter both the fluid kinetics and the hemodynamic responses to volume expansion in sheep.

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  • 1Department of Anesthesiology, South Hospital, Stockholm, Sweden.

Abstract

BACKGROUND:

Plasma volume expansion is often performed during adrenergic therapy in the intensive care unit, but little is known about their combined effects.

MATERIALS AND METHODS:

The influence of three adrenergic drugs (50 microg/kg/min of dopamine, 0.1 microg/kg/min of isoprenaline, or 3 microg/kg/min of phenylephrine) on the relationship between plasma dilution (an index of volume expansion) and the central hemodynamic responses to volume loading with 24 ml/kg of 0.9% saline were evaluated in 6 adult sheep. Kinetic analysis was also applied to the data on plasma dilution and the urinary excretion measured during and after volume loading.

RESULTS:

The adrenergic agents markedly changed the baseline values for all hemodynamic parameters. The kinetic analysis showed that phenylephrine, which is an alpha-adrenergic receptor agonist, promoted renal excretion of infused fluid at the expense of fluid distribution to the periphery (P < 0.05 versus controls). Isoprenaline, which stimulates adrenergic beta-receptors, had the opposite effect. During volume expansion, cardiac atrial pressures increased by 25 to 90%, cardiac output by 13-80% and the arterial pressures by 2 to 22%. Plasma dilution during and after volume loading correlated, in a linear fashion, with these hemodynamic responses. The correlations were strong (r > 0.80) in the control and phenylephrine groups, but weaker in the dopamine and isoprenaline groups. Dopamine was associated with the most variable hemodynamic responses overall.

CONCLUSIONS:

Adrenergic drugs altered the hemodynamics at baseline (direct effects), changed the distribution and elimination of infused 0.9% saline (indirect effects) and, finally, modified most hemodynamic responses to plasma dilution (interaction effects).

[PubMed - indexed for MEDLINE]
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