Pharmacology Questions Flashcards
How does norepinephrine work, and when would you use it in the ICU?
Norepinephrine primarily stimulates alpha-1 receptors for vasoconstriction, increasing SVR and BP; mild beta-1 activity increases contractility. It’s the first-line vasopressor in septic shock.
What is the difference between dopamine and dobutamine?
Dopamine is dose-dependent: low = renal vasodilation, moderate = beta-1 (inotropy), high = alpha-1 (vasoconstriction). Dobutamine mainly stimulates beta-1, increasing cardiac output without significant vasoconstriction.
When would you use dopamine vs. dobutamine?
Use dopamine in hypotensive patients needing inotropy. Use dobutamine in low-output heart failure patients with preserved BP.
Describe vasopressin’s mechanism and how it differs from norepinephrine.
Vasopressin acts on V1 receptors (vasoconstriction) and V2 (water retention). It’s non-adrenergic, making it useful in catecholamine-refractory septic shock.
When is phenylephrine (neosynephrine) preferred, and why?
It’s a pure alpha-1 agonist—causes vasoconstriction without increasing heart rate. Preferred in tachycardic patients with hypotension.
What is epinephrine’s role in resuscitation and its pharmacodynamic profile?
Stimulates alpha and beta receptors; low dose = beta-1 effects, high dose = alpha-1 vasoconstriction. Used in CPR to increase perfusion pressure and cardiac output.
What is the mechanism of action of propofol?
GABA-A agonist; increases chloride influx, causing sedation and hypnosis.
Why might propofol not be ideal in a hypotensive patient?
Causes vasodilation and myocardial depression, which can worsen hypotension.
What are the hemodynamic effects of ketamine?
Increases HR, BP, and CO due to sympathomimetic effects; preserves airway reflexes.
What is the main concern when using fentanyl in a critically ill patient?
Respiratory depression, chest wall rigidity at high doses, and accumulation in hepatic/renal impairment.
How does Precedex differ from other sedatives?
Alpha-2 agonist; provides sedation with minimal respiratory depression and some analgesia.
What is the mechanism of action of norepinephrine (Levophed)?
Alpha-1 and beta-1 agonist; increases SVR and CO with minimal beta-2 effect.
When would you consider vasopressin in septic shock?
When patients are refractory to catecholamines; helps restore vascular tone via V1 receptor agonism.
What’s a key risk of using high-dose vasopressors?
Ischemia of peripheral tissues/organs due to excessive vasoconstriction.
