Fluid Optimization

Fluid Optimization

Fluids are routinely administered to account for losses during surgery, prevent dehydration, and maximize oxygen delivery to tissue. As shown below, however, there is a "sweet spot", called normovolemia, for fluid management. Too little fluids, or hypovolemia, or too much fluids, or hypervolemia, are both associated with increased rates of complications.

Complications large

Cannesson M., J Cardiothorac Vasc Anesth. 2010;24(3):487-497.

 

The clinical standard of administering fluids has been to administer fluids based on pre-operative weight and "overfill" slightly to increase body weight by 3 – 6 kg. However, as deviations from hemodynamic stability increase (caused by more invasive surgery and/or more severe clinical conditions), it becomes more difficult to choose a fixed dose of fluids to administer to reach normovolemia. At this point, advanced monitoring and goal-directed fluid administration to maintain enough intravascular volume is recommended.

As shown in the Figure below, fluid challenges are administered in combination with hemodynamic monitoring for stroke volume (which is Cardiac Output divided by Heart Rate) changes. The goal is to reach Point B, where further administration of fluids does not significantly increase stroke volume.

 

Stroke volume

Adapted from Grocott, Mythen, and Gan, 2005.

 

More than 32 independently-conducted studies have shown that optimized fluid and drug management with accurate CO monitoring can lead to significantly improved outcomes including reduced mortality, morbidity, and shorter length of hospital stay.

 

References:

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