Hemodynamic Measurement The term hemodynamic is defined as the study of the forces that influence the circulation of blood. Hemodynamic measurements are made with a pulmonary artery catheter. Figure 15-1 depicts the insertion and movement of a pulmonary artery catheter.
Stroke Volume Stroke Volume (SV) is the amount of blood ejected from the ventricles with each contraction. SV is derived from cardiac output divided by Heart rate SV=CO/HR Table 15-3 is a list of factors that will influence cardiac performance
Stroke Volume Index Note: Any index measurement standardizes the measurement to account for body size. Stroke volume index (SVI) is: SV/BSA BSA= Body surface area
Stroke Volume Index The stroke volume index (SVI) relates SV to body size and is derived by dividing the stroke volume by the body surface area (BSA): – SVI = SV / BSA The stroke volume index reflects: -contractility of the heart-overall blood volume status-amount of venous return
Factors Increasing SV Factors that increase stroke volume include: -positive inotropic drugs – epinephrine, dopamine, isuprel, digitalis-early sepsis-hyperthermia-hypervolemia-decreased vascular resistance
Cardiac Index Standardizes CO to body surface area CI=CO/BSA
Central Venous Pressure Normal CVP is about 0-8 mm Hg. The following may cause CVP to increase: – increase preload – hypervolemia, VSD – increase afterload – ARDS, COPD, PE – increase contractility The following may cause CVP to decrease: – hypovolemia – arrhythmias -right ventricular failure
Pulmonary Capillary Wedge Pressure The pulmonary capillary wedge pressure (PCWP) is normally between 4 – 12 mm Hg. The PCWP reflects the downstream pressure in the pulmonary venous system. Pulmonary venous pressure, in turn, reflects left atrial pressure.
Computed Hemodynamic Measurements A number of hemodynamic values can be calculated from those values that are directly measured. The most common and practical calculated measurements are: -stroke volume -stroke volume index -cardiac index -pulmonary vascular resistance -systemic vascular resistance
Pulmonary Vascular Resistance (PVR) The PVR measurement reflects the afterload of the right ventricle or the resistance that the right ventricle must overcome to eject blood into the pulmonary vasculature: – PVR = (PA – PCWP / CO) x 80
Factors that Decrease PVR Factors that decrease PVR include: -oxygen-isuprel-aminophylline-calcium channel blockers-acetlycholine
Factors that increase SVR Factors that increase SVR include: -medication – dopamine, epinephrine, phenyephrine -hypovelemia-late septic shock-decreased PCO2-CHF