Hemodynamic Measurement Terminology

The following table illustrates common values associated with a hemodynamic printout.

• Please be aware that these normal values may vary depending on your instrumentation, so always rely on your institution's policies and procedures.
• Some of the values are actual measurements of pressure (mm Hg), volume (ml), or flow speed (L/min), and other values are calculated or "derived" from formulae. Click on the name of the parameter to link to the actual formula, if applicable.

• Afterload: Afterload describes the resistance that the heart has to overcome, during every beat, to send blood into the aorta. These resistive forces include vasoactivity and blood viscosity.
• Cardiac Index (CI): The amount of blood pumped by the heart, per minute, per meter square of body surface area.
• Cardiac Output (CO): The volume of blood pumped by the heart in one minute.
  • Increased cardiac output may indicate a high circulating volume.
  • Decreased cardiac output indicates a decrease in circulating volume or a decrease in the strength of ventricular contraction.
• Central Venous Pressure (CVP): CVP readings are used to approximate the Right Ventricular End Diastolic Pressure (RVEDP). The RVEDP assesses right ventricular function and general fluid status.
  • Low CVP values typically reflect hypovolemia or decreased venous return.
  • High CVP values reflect overhydration, increased venous return or right sided cardiac failure.
• Mean Arterial Pressure (MAP): Reflects changes in the relationship between cardiac output (CO) and systemic vascular resistance (SVR) and reflects the arterial pressure in the vessels perfusing the organs.
  
  • A low MAP indicates decreased blood flow through the organs.
• A high MAP indicates an increased cardiac workload.
• Preload: Preload occurs during diastole. It is the combination of pulmonary blood filling the atria and the stretching of myocardial fibers. Preload is regulated by the variability in intravascular volume.
  • Volume reduction decreases preload
  • Volume increase will increase preload, mean arterial pressure (MAP) and stroke index (SI).
• Pulmonary Artery Pressure (PA Pressure): Blood pressure in the pulmonary artery.
  • Increased pulmonary artery pressure may indicate: a left-to-right cardiac shunt, pulmonary artery hypertension, COPD or emphysema, pulmonary embolus, pulmonary edema, left ventricular failure.
• Pulmonary Capillary Wedge Pressure (PCWP or PAWP): PCWP pressures are used to approximate LVEDP (left ventricular end diastolic pressure).
  • High PCWP may indicate left ventricle failure, mitral valve pathology, cardiac insufficiency, cardiac compression post hemorrhage.
• Pulmonary Vascular Resistance (PVR): The measurement of resistance or the impediment of the pulmonary vascular bed to blood flow.
  
• An increased PVR or "Pulmonary Hypertension" is caused by pulmonary vascular disease, pulmonary embolism, or pulmonary vasculitis, or hypoxia.
• A decreased PVR is caused by medications such as calcium channel blockers, aminophylline, or isoproterenol or by the delivery of O2.
• Right Ventricular Pressure (RV Pressure): A direct measurement that indicates right ventricular function and general fluid status.
  • High RV pressure may indicate: pulmonary hypertension, right ventricle failure, congestive heart failure.
• Stroke Index or Stroke Volume Index: (SI or SVI): The amount of blood ejected from the heart in one cardiac cycle, relative to Body Surface Area (BSA). It is measured in ml per meter square per beat.
  
• An increased SVI may be indicative of early septic shock, hyperthermia, hypervolemia or be caused by medications such as dopamine, dobutamine, or digitalis.
• A decreased SVI may be caused by CHF, late septic shock, beta blockers, or an MI.
• Stroke Volume (SV): The amount of blood pumped by the heart per cardiac cycle. It is measured in ml/beat.
  • A decreased SV may indicate impaired cardiac contractility or valve dysfunction and may result in heart failure.
  • An increased SV may be caused by an increase in circulating volume or an increase in inotropy.
• Systemic Vascular Resistance (SVR): The measurement of resistance or impediment of the systemic vascular bed to blood flow.
  • An increased SVR can be caused by vasoconstrictors, hypovolemia, or late septic shock.
  • A decreased SVR can be caused by early septic shock, vasodilators, morphine, nitrates, or hypercarbia.