Drug Information: Angiotensin II
Detailed information regarding Angiotensin II, a medication commonly used in clinical settings to raise blood pressure in adults with septic or other distributive shock. Angiotensin II is a potent vasoconstrictor, acting directly on angiotensin II receptors in blood vessels to increase systemic vascular resistance and thereby elevate blood pressure. Its short half-life necessitates continuous intravenous infusion to maintain therapeutic effects. It is particularly useful when hypotension persists despite adequate fluid resuscitation and initial vasopressor therapy.
Category
Vasopressor
Mechanism of Action
Angiotensin II exerts its effects by binding to angiotensin II type 1 (AT1) receptors, which are Gq protein-coupled receptors located on vascular smooth muscle cells, adrenal glands, and the kidneys. When Angiotensin II binds to these receptors, it activates intracellular signaling pathways, leading to a cascade of physiological effects. In vascular smooth muscle, this binding leads to vasoconstriction, resulting in an increase in systemic vascular resistance (SVR) and, consequently, an elevation in blood pressure. In the adrenal glands, AT1 receptor activation stimulates the release of aldosterone, which promotes sodium and water retention by the kidneys, further contributing to blood pressure elevation. Angiotensin II also has direct effects on the kidneys, influencing sodium reabsorption and fluid balance. Furthermore, Angiotensin II can promote the release of vasopressin (antidiuretic hormone, ADH) from the posterior pituitary, which also increases water reabsorption in the kidneys. This combined effect of vasoconstriction, aldosterone release, and vasopressin release makes Angiotensin II a potent regulator of blood pressure and fluid balance.
Clinical Uses
Angiotensin II is primarily indicated for raising blood pressure in adults with septic or other distributive shock who remain hypotensive despite fluid resuscitation and the use of initial vasopressors like norepinephrine or dopamine. Septic shock is a life-threatening condition characterized by widespread vasodilation and decreased systemic vascular resistance, leading to dangerously low blood pressure. Angiotensin II is particularly useful in cases where the patient is refractory to conventional vasopressors. It provides a more direct vasoconstrictive effect compared to vasopressors that rely on adrenergic receptors, which may become less responsive in severe sepsis. Angiotensin II can also be used in other forms of distributive shock, such as neurogenic shock or anaphylactic shock, where vasodilation is a primary component of the hypotension. The use of Angiotensin II should be guided by hemodynamic monitoring to ensure appropriate blood pressure control and to minimize potential adverse effects.
Dosage
Adults:
- Initial Dose: 20 ng/kg/min via continuous intravenous infusion.
- Titration: Titrate every 5 minutes by increments of up to 15 ng/kg/min as needed to achieve or maintain target blood pressure, not to exceed 80 ng/kg/min during the first 3 hours of treatment. Maintenance dose should be titrated to maintain the desired blood pressure.
- Maintenance Dose: After the first 3 hours, decrease the rate by increments of up to 15 ng/kg/min every 5 to 15 minutes as needed to maintain the target blood pressure. The maximum maintenance dose is 40 ng/kg/min.
- Route of Administration: Continuous intravenous infusion.
Pediatrics: The safety and efficacy of Angiotensin II in pediatric patients have not been established.
Indications
* Hypotension in Septic Shock
* Hypotension Refractory to Other Vasopressors
* Distributive Shock
Contraindications
Angiotensin II is contraindicated in patients with:
* Known allergy to Angiotensin II or any of its components.
* Thromboembolic events: Due to the increased risk of arterial and venous thromboembolic events, Angiotensin II is generally contraindicated in patients with a history of these conditions unless the benefits clearly outweigh the risks.
FAQ
Q: What is Angiotensin II used for?
A: Angiotensin II is used to raise blood pressure in adults with septic or other distributive shock when their blood pressure remains dangerously low despite fluid resuscitation and other vasopressors.
Q: How is Angiotensin II administered?
A: It is administered as a continuous intravenous infusion, allowing for precise control of the dosage and blood pressure response.
Q: What are the potential side effects of Angiotensin II?
A: Common side effects include thromboembolic events (blood clots), hypertension, and peripheral ischemia. Monitoring for these complications is crucial during treatment.
Q: How does Angiotensin II work?
A: Angiotensin II works by binding to AT1 receptors on blood vessels, causing vasoconstriction and increasing systemic vascular resistance, which in turn raises blood pressure. It also stimulates the release of aldosterone, promoting sodium and water retention.
Q: What should I do if my blood pressure gets too high while on Angiotensin II?
A: Inform your healthcare provider immediately. The infusion rate can be adjusted to lower your blood pressure.
Q: Can Angiotensin II be used in patients with a history of blood clots?
A: Angiotensin II should be used with caution in patients with a history of blood clots due to the increased risk of thromboembolic events. The potential benefits should be carefully weighed against the risks.
Q: Is Angiotensin II safe for pregnant women?
A: The safety of Angiotensin II during pregnancy has not been established. It should only be used if the potential benefit justifies the potential risk to the fetus.
Q: How often will my blood pressure be monitored while receiving Angiotensin II?
A: Your blood pressure will be monitored frequently, often continuously, to ensure the medication is working effectively and safely.
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