Bret Alvis, MD
Vanderbilt University Medical Center
Nashville, Tennessee
Disclosure information not submitted.
Monica Polcz, MD
Resident Physician
Vanderbilt University Medical Center
Nashville, Tennessee, United States
Disclosure information not submitted.
Eric Wise, MD, MA
Assistant Professor of Surgery
University of Minnesota Medical School
Minneapolis, Minnesota
Disclosure information not submitted.
Colleen Brophy, MD
Professor
Vanderbilt University Medical Center, United States
Disclosure information not submitted.
Kyle Hocking, PhD
Assistant Professor
Vanderbilt University, United States
Disclosure information not submitted.
.jpg "Meghan Breed, MD photo")
Meghan Breed, MD
Vanderbilt University Medical Center
Nashville, Tennessee
Disclosure information not submitted.
Title: The relationship of key hemodynamic parameters in a hemorrhage and volume overload porcine model
Introduction: Central hemodynamic parameters remain the key data points used in critical care patients when diagnosing and managing volume. To date, little research exists investigating the relationship of these parameters. This investigation uses a porcine model to measure stroke volume (SV) and systemic vascular resistance (SVR) at key volume points during hemorrhage and induced volume overload. The aim of this study was to identify how SVR, and SV changed in relation to the pulmonary capillary wedge pressure (PCWP).
Methods: Sixteen pigs were anesthetized and cannulated with an arterial line and a pulmonary artery catheter. Pigs were hemorrhaged at 30 mL/min up to 800 mL, returned to euvolemia using autologous blood, and then given up to 5000 mL of Plasmalyte via a central catheter. SVR, PCWP and SV (via thermodilution) were measured at the different volume states at every 100 mL during hemorrhage and 500 mL during volume overload. To determine the differences in SVR between the three conditions ANOVA with multiple comparisons was conducted, for correlations of data Pearson correlations were used, and for determining the slope and its significance linear regression was conducted.
Results: SVR demonstrated an inverse relationship to PCWP and was significantly higher (p < 0.05) when the pig was undergoing hemorrhage and at baseline compared to volume overload conditions. SVR decreased linearly with a significantly non-zero slope with increased volume administration and it did not have a significantly non-zero slope relative to the amount of volume lost. SV demonstrated a direct relationship to PCWP and exhibited a linear correlation with a significant slope under all conditions observed, but the slope for hemorrhage (1.61e-5) was ten times greater than that of volume overload (1.64e-6). A contour plot of the three variables together (PCWP, SVR, SV) was plotted as the color variable with SVR on the x-axis and SV on the y-axis it is observable that with decreasing SVR which occurred in the volume overload state the stroke volume discontinues to rise with increasing PCWP.
Conclusion: An understanding of SV and SVR is important when caring for a critically ill patient. The dynamics of PCWP and SV through various volume states under different SVRs will help a clinician understand their patients resuscitation.