Hemodynamic Parameters to Guide Fluid Therapy, Dr. Perz

Katie Perz, DO

Hemodynamic Parameters to Guide Fluid Therapy

Paul E Marik, Xavier Monney, Jean-Louis Teboul

Journal Ann Intensive Care, 2011

Introduction: The cornerstone of treating patients with shock remains as it has for decades: IV fluids.  Surprisingly, dosing IV fluid during resuscitation of shock remains largely empirical.  Multiple studies have demonstrated that only approximately 50% of hemodynamically unstable patients in the ICU and OR respond to a fluid challenge.  Cardiac filling pressures, including CVP and PAOP have been traditionally used to guide fluid management, but studies during the past 30 years have demonstrated that cardiac filling pressures are unable to predict fluid responsiveness.  During the past decade, a number of dynamic test of volume responsiveness have been reported.  This article outlines a recommendation for assessing hemodynamic management with consideration of useful parameters for volume status and ventilatory status of the patient (mechanically vs. spontaneous vs. combination).

Recommendations for accurately assessing volume status:

1.     Pulse Pressure Variation (PPV):

a.     Derived from analysis of arterial waveform

b.     Some authors predict that PPV was a reliable predictor of fluid responsiveness only when tidal volumes are >8mL/kg

2.     Stroke Volume Variation (SVV):

a.     Derived from pulse contour analysis

3.     Pulse Oximeter Plethysmographic Waveform Amplitude Variation

a.     Dynamic changes of this waveform with positive pressure ventilation have shown a significant correlation and good agreement with the PPV and have accurately predicted fluid responsiveness in the OR in ICU

4.     Doppler Echocardiography

a.     Respiratory changes in aortic blood velocity as measure by TEE can predict fluid responsiveness in mechanically ventilated patients

b.     Changes in vena-caval diameter can be measured to predict fluid responsiveness

5.     End Expiratory Occlusion Test

a.     Interrupting mechanical ventilation during an end-expiratory occlusion can increase cardiac preload sufficiently for such a test being used to predict fluid responsiveness

6.     Passive Leg Raising

a.     Can be used in patients who are mechanically ventilated or those who have a spontaneous component to their mechanical ventilation

b.     The change in aortic blood flow, measured by esophageal Doppler, during a 45 degree  leg elevation was shown to predict the changes in aortic blood flow produced by a 500mL fluid challenge even in patients with arrhythmias and/or spontaneous ventilator triggering (a situation when PPV loses its predictive ability)

c.     Can be assessed with use of Flo-trac Vigileo, PiCCO, or NICOM devices

                                               i.     Less invasive than PA catheterization but not ideally suited to resuscitate in the ER or ward.

Conclusion: All these methods have a useful place in the continuum of the resuscitation process.  This article recommends that CVP no longer be used to guide fluid management in the OR, ICU or ER.