Management of Systemic Vascular Resistance in the CVICU

Assessment and Management of SVR

Clinical signs of increased SVR include absent or weak distal pulses, cool extremities, prolonged capillary refill, and narrow pulse pressure with relatively increased diastolic blood pressure, as recommended by the American College of Critical Care Medicine 1
Norepinephrine is recommended for maintaining mean arterial pressure in hyperdynamic states, which has been shown to improve urine output and creatinine clearance, according to the American College of Critical Care Medicine 1
Vasopressin at replacement doses can effectively offset the potential drop in SVR when using inotropes like dobutamine or milrinone, as suggested by the American College of Cardiology 2
In septic patients with low SVR, maintaining a cardiac index between 3.3 and 6.0 L/min/m² is associated with best outcomes, as recommended by the American College of Critical Care Medicine 1
Vasodilator therapy with additional volume loading is the effective approach for patients with high SVR, according to the American College of Critical Care Medicine 1
Nitroprusside is effective for high-afterload left ventricular failure due to its potent arterial and venous dilation properties, as suggested by the American College of Cardiology 2
Phosphodiesterase inhibitors (milrinone) or α-adrenergic blockers (phenoxybenzamine, phentolamine) are effective for reducing SVR in patients with single-ventricle physiology, as recommended by the American Heart Association 3

Maintain SVR greater than PVR to ensure adequate right ventricular coronary perfusion, as recommended by the American Heart Association 4
Right ventricular coronary perfusion occurs during both systole and diastole, so if PVR exceeds SVR (systolic pulmonary arterial pressure > systolic systemic arterial pressure), right ventricular ischemia can result, according to the American Heart Association 4
Inhaled nitric oxide can acutely decrease PVR and improve cardiac output without affecting SVR, making it valuable in managing right ventricular failure, as suggested by the American College of Cardiology 4
Intravenous or inhaled pulmonary vasodilators can reduce right ventricular afterload for pulmonary arterial hypertension and right ventricular failure, according to the American College of Cardiology 2

Continuous monitoring of physiologic parameters (blood pressure, heart rate, and other measurements such as pulmonary capillary wedge pressure) is essential to achieve the correct dose of vasoactive medications, as recommended by the American College of Critical Care Medicine 1
Cardiac index between 3.3 and 6.0 L/min/m² is associated with best outcomes in septic shock patients compared with patients without septic shock for whom a cardiac index above 2.0 L/min/m² is sufficient, according to the American College of Critical Care Medicine 1

Volume status assessment in pulmonary hypertension patients is notoriously difficult, and non-invasive estimates of central venous pressures may be misleading, as noted by the American Heart Association 4
The traditional belief that the right ventricle is preload dependent often leads to inappropriate and detrimental volume loading in right ventricular dysfunction, according to the American College of Cardiology 2
The right ventricle prefers euvolemia with a central venous pressure of 8-12 mmHg, as suggested by the American College of Cardiology 2

Systemic vascular resistance represents the resistance to blood flow generated by all systemic vasculature, excluding pulmonary vasculature 5, 6
SVR is calculated as (systemic mean arterial blood pressure minus right atrial pressure) divided by cardiac output 5, 6
The major determinant of SVR is arteriolar tone, but blood viscosity and vascular capacitance are also contributing factors 6
SVR is typically measured in dynes/s/cm² 6

The American College of Cardiology recommends that SVR should be maintained higher than pulmonary vascular resistance (PVR) to ensure adequate right ventricular coronary perfusion and prevent right ventricular ischemia 7
Maintaining appropriate SVR is essential for ensuring adequate coronary perfusion pressure 7
Maintaining appropriate SVR is essential for preventing right ventricular ischemia 7

Direct measurement via pulmonary artery catheter provides the most accurate assessment of SVR 7
Central venous pressure monitoring is helpful in detecting and treating abnormal SVR 7

Vasopressin at replacement doses can be used to offset potential drops in SVR when using inotropes like dobutamine 7

Vasodilators are indicated when SVR is excessively elevated 7
Short-acting calcium channel blockers are preferred over preload-reducing agents like nitroglycerin in patients with aortic stenosis 8
In patients with regurgitant valve lesions (AR or MR), decreasing systemic afterload will augment systemic LV output and reduce regurgitant volume 8

Surgical repair is recommended when pulmonary vascular resistance is less than one-third of SVR 9, 10, 11, 12, 13
Closure of atrial septal defects should not be performed when pulmonary vascular resistance is greater than two-thirds of SVR 9, 10

In ICU settings, maintaining SVR greater than PVR is a major guideline for selecting inotropes and vasopressors 7
Inotropes with neutral or beneficial effects on PVR include dobutamine, milrinone, and epinephrine 7
Inhaled nitric oxide can be used to decrease PVR without affecting SVR in hypotensive pulmonary hypertension patients 7

Anesthetic management should take into account the effects on SVR, particularly in patients with valvular heart disease 8
Regional anesthetics may be beneficial in patients with regurgitant valve lesions due to favorable systemic vasodilation 8
In patients with aortic stenosis, maintaining adequate SVR is critical to ensure coronary perfusion 8

The American Heart Association recommends a normal range of systemic vascular resistance (SVR) of 800-1200 dyn·s·cm⁻⁵ for hemodynamic management in critically ill patients and heart donors 14, 15
The American College of Cardiology suggests that SVR should be maintained between 800-1200 dyn·s·cm⁻⁵ to ensure adequate coronary perfusion of the right ventricle 14, 15
In patients with congenital heart disease, surgical repair is recommended when pulmonary vascular resistance is less than one-third of SVR 16

The American Heart Association recommends titrating vasopressin to maintain SVR between 800-1200 dyn·s·cm⁻⁵ in aggressive hemodynamic management of heart donors 14, 15
For low SVR (<800 dyn·s·cm⁻⁵), vasopressin replacement therapy (0.5-4 U/h) can effectively compensate for the potential drop in SVR when using inotropics 14, 15

Right atrial (central venous) pressure should be obtained with a central venous catheter to provide the pressure component needed for SVR calculation. 17
Cardiac output must be measured by thermodilution using a pulmonary artery catheter to ensure accurate SVR determination. 17

The external pressure transducer must be zeroed at the mid‑thoracic level before acquiring arterial and right‑atrial pressures to prevent systematic measurement error. 18