Systemic Vascular Resistance Calculation and Clinical Significance

Formula and Definition

The American College of Cardiology defines SVR as (Mean Arterial Pressure - Right Atrial Pressure) divided by Cardiac Output, typically expressed in dynes/sec/cm⁵ 1
SVR represents the resistance generated by all systemic vasculature, excluding pulmonary circulation, with the major determinant being arteriolar tone, though blood viscosity and vascular capacitance also contribute 1

Organ blood flow correlates directly with perfusion pressure and inversely with vascular resistance, making SVR a critical determinant of tissue perfusion, according to the American Heart Association 2
When ventricular function is healthy, elevated SVR produces hypertension while maintaining cardiac output, as stated by the Critical Care Medicine society 2, 3
With reduced ventricular function, normal blood pressure combined with high SVR indicates reduced cardiac output, as recommended by the American College of Cardiology 2, 3
Marked elevation in vascular resistance reduces blood flow sufficiently to cause shock, according to the Critical Care Medicine society 2, 3
In septic shock, maintaining cardiac index between 3.3-6.0 L/min/m² is associated with best outcomes, compared to >2.0 L/min/m² for non-septic patients, as stated by the Critical Care Medicine society 2, 3

Clinical signs of high SVR include absent or weak distal pulses, cool extremities, prolonged capillary refill, and narrow pulse pressure with relatively increased diastolic blood pressure, according to the American Heart Association 3, 1
The effective approach is vasodilator therapy with additional volume loading as vascular capacity expands, as recommended by the Critical Care Medicine society 3, 1

The American College of Cardiology states that pulmonary artery catheter provides the most accurate SVR assessment 4, 1

In the cardiovascular ICU, SVR must be maintained greater than pulmonary vascular resistance (PVR) to ensure adequate right ventricular coronary perfusion, according to the American College of Cardiology 1
Vasoactive agents must be selected based on their effects on SVR, with continuous monitoring of physiologic parameters essential for correct dosing, as stated by the Critical Care Medicine society 4
Dobutamine is indicated when low cardiac output exists with adequate or increased SVR, as recommended by the Critical Care Medicine society 5, 4

The American College of Cardiology defines systemic vascular resistance (SVR) as SVR = (MAP − RAP) / CO, and to express the result in standard units (dynes·s·cm⁻⁵) the value is multiplied by 80. 6

The Society of Critical Care Medicine identifies cold extremities as a bedside sign suggesting markedly increased SVR. 7
The Society of Critical Care Medicine also notes that a prolonged capillary refill time correlates with high SVR. 7

The Society of Critical Care Medicine recommends maintaining a cardiac index of 3.3 – 6.0 L·min⁻¹·m⁻² in patients with septic shock to achieve the best clinical outcomes. 7

According to the Society of Critical Care Medicine, the relationship between cardiac output, perfusion pressure, and SVR is: CO = (MAP − CVP) / SVR. 7
The Society of Critical Care Medicine advises that perfusion pressure (MAP − CVP) should be kept above a critical threshold to preserve adequate organ blood flow. 7