Plasma Volume Oscillations during Fluid Therapy in Humans

Area of Science:

• Physiology
• Fluid dynamics
• Medical diagnostics

Background:

• Plasma dilution curves are frequently used in intravenous fluid therapy.
• Observed oscillations on these curves during fluid infusion require explanation.

Purpose of the Study:

• To determine the prevalence of oscillations in plasma dilution curves during fluid therapy.
• To investigate the physiological basis of these observed oscillations.

Main Methods:

• Analysis of 269 plasma dilution curves using Fourier transforms.
• Application of a volume kinetic model to identify oscillating patterns.
• Population kinetic analysis to study fluid distribution between body compartments.

Main Results:

• Oscillating patterns were identified in approximately 67% of fluid infusion experiments.
• Oscillations typically exhibited a dominant frequency of 1 hour or multiples thereof.
• Amplitudes of 1-4% of plasma volume suggested blood volume changes of 60-240 mL, linked to doubled interstitial fluid turnover.

Conclusions:

• Low-frequency oscillations are common during fluid therapy.
• These oscillations are associated with rapid interstitial fluid turnover.
• The findings suggest that oscillations may result from accelerated lymphatic flow.