From the Guidelines
The normal value of Systemic Vascular Resistance (SVR) is between 800 to 1200 dyne · s · cm-5. This range is crucial for maintaining optimal blood pressure and cardiac output, and is a key target in managing critically ill patients to ensure adequate tissue perfusion and minimize morbidity and mortality 1.
Key Points to Consider
- SVR represents the resistance to blood flow offered by all of the systemic vasculature, except for the pulmonary vasculature.
- It is calculated using mean arterial pressure, central venous pressure, and cardiac output.
- Factors such as blood viscosity, vessel length and diameter, and vascular tone can influence SVR.
- Understanding normal SVR values is essential for assessing cardiovascular function and diagnosing conditions like hypertension or shock.
Clinical Implications
- In clinical practice, maintaining SVR within the normal range is often a goal in managing critically ill patients to ensure adequate tissue perfusion and prevent organ dysfunction.
- The target range of 800 to 1200 dyne · s · cm-5 is based on expert consensus and is supported by studies such as the one published in Circulation in 2002 1.
- Deviations from this range may indicate underlying cardiovascular problems and require prompt attention to prevent adverse outcomes.
From the Research
Normal Value of Systemic Vascular Resistance (SVR)
The normal value of Systemic Vascular Resistance (SVR) can be defined based on several studies:
- A study published in 2011 2 classified SVR into three categories: below 900 dyn s cm(-5), between 900 and 1200 dyn s cm(-5), and above 1200 dyn s cm(-5).
- Another study from 1999 3 defined low SVR as less than 800 dynes x s/cm5.
- A 1999 study 4 defined low SVR as an indexed systemic vascular resistance (SVRi) of <1800 dyne x sec/cm5 x m2.
- A more recent study from 2022 5 used an estimated SVR analog (eSVR) based on echocardiographic methods, with a tertile-based classification system.
- A 2013 study 6 divided patients into three groups according to the SVRI value: low (<1200 dyn cm(-5) m(2)), normal (1200-2500 dyn cm(-5) m(2)), and high (>2500 dyn cm(-5) m(2)) SVRI states.
Key Findings
Some key findings related to SVR include:
- Low SVR is associated with increased mortality, regardless of the etiology 3.
- The incidence of low SVR was 44% in patients undergoing cardiopulmonary bypass 4.
- Elevated eSVR is associated with increased risk of heart failure, major cardiovascular events, and death 5.
- The reliability of the Vigileo-FloTrac system in measuring cardiac output and tracking cardiac output changes is impacted by SVR 6.
SVR Classification
SVR can be classified into different categories based on its value: