Pulse Pressure Variation for Hydration Status

Pulse Pressure Variation is used to determine fluid responsiveness in mechanically ventilated casualties. It assesses the heart-lung interaction and predicts the need for additional volume or intravenous fluids. The concept is based on the fact that changes in intrathoracic pressure during mechanical ventilation can impact cardiac preload and stroke volume, thus causing alterations in pulse pressure. When fluid is given to fluid-responsive patients, an elevation in cardiac preload increases stroke volume and pulse pressure. Conversely, an increase in cardiac preload will not significantly increase stroke volume or pulse pressure in patients not responsive to fluid administration.

Significant limitations to this option. The casualty needs to be on mechanical ventilation to enable this assessment. Also, Vt needs to be at 8mL/kg, the usual range of tidal volume is 6-8mL/kg. Additionally, most studies required arterial lines, which is fantastic for a resource-rich ICU. For those working in remote, austere and challenging environments, getting an arterial line is problematic at best and dangerous.

How reliable is this? This meta-analysis focused on 22 studies that had 807 patients. They found that using Pulse Pressure Variation to determine fluid responsiveness was at a 94% success rate.

Using Pulse Pressure to Assess fluid responsiveness in spontaneously breathing patients. This study found that Pulse Pressure change is one of the variables that can successfully be used to assess positive outcomes for fluid responsiveness.

Pulse Pressure for indications of Haemorrhage. In this study, a narrowed pulse pressure, even without hypotension, was associated with active haemorrhage requiring blood product transfusion and intervention for haemorrhage control.?This study also found that a pulse pressure of less than 30mmHg was an independent predictor for increased blood loss.

The bottom line. As Remote Medics, we focus on getting the BP and MAP as part of our secondary vital signs. Make sure that you consider the pulse pressure when assessing your critical patient.

Resources

Eddy J. Gutierrez, “Fluid Resuscitation in Sepsis and Volume Responsiveness”, eddyjoemd blog, October 27, 2021. Available at:?https://eddyjoemd.com/pulse-pressure-variation.

Mehta Y, Arora D. Newer methods of cardiac output monitoring. World J Cardiol. 2014 Sep 26;6(9):1022-9. doi: 10.4330/wjc.v6.i9.1022.