From the FDA Drug Label
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From the Research
Precapillary and postcapillary sphincters play crucial roles in the body's response to shock, regulating blood flow through capillary beds to preserve vital organ function, as evidenced by the most recent study in 2022 1.
Role of Precapillary Sphincters
- Located at the arteriolar end of capillaries, precapillary sphincters constrict in response to sympathetic stimulation during shock, reducing blood flow to less essential tissues like skin and digestive organs.
- This vasoconstriction helps maintain blood pressure and redirects blood to critical organs such as the brain and heart.
Role of Postcapillary Sphincters
- Postcapillary sphincters, found at the venous end of capillaries, may remain relatively dilated compared to precapillary sphincters, creating a pressure differential.
- This pressure imbalance can lead to fluid movement out of the capillaries into the interstitial space, contributing to edema seen in prolonged shock states.
Clinical Implications
- The dysfunction of these sphincters explains many clinical manifestations of shock, including cold, clammy skin from peripheral vasoconstriction, and later, tissue edema and organ dysfunction from capillary leak.
- Understanding these mechanisms helps guide shock management, which focuses on restoring adequate tissue perfusion through fluid resuscitation and vasopressors that work by influencing these vascular control points, as discussed in recent studies 2, 3, 4.
Management of Shock
- The use of vasopressors, such as norepinephrine, can help increase systemic vascular resistance and cardiac contractility, improving tissue perfusion and outcomes in shock patients, as shown in studies 5, 4.
- Early recognition and management of shock, including the use of capillary refill time as a prognostic indicator, can improve patient outcomes, as demonstrated in a recent observational study 1.