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Alpha Adrenergic Receptor Antagonists

• Alpha adrenergic receptor antagonists prevent endogenous catecholamines from reaching alpha receptors.
• These antagonists lower blood pressure, particularly diastolic pressure, and decrease systemic vascular resistance.
• Non-selective blockade of alpha 2 receptors can cause reflex tachycardia due to increased norepinephrine secretion.
• Patients are prone to orthostatic hypotension when taking alpha adrenergic receptor antagonists.
• Alpha adrenergic receptor antagonists are prescribed for patients with hypertension, enlarged prostate, and glaucoma.
• Clonidine is primarily an alpha 2 receptor agonist used early for emergency hypertension treatment; it suppresses norepinephrine release, causing vasodilation.
• Phentolamine can reverse vasoconstriction in affected tissue if catecholamines or sympathomimetics cause profound tissue necrosis from extravasation and is injected sub-Q.
• Labetalol has alpha 1, beta 1, and beta 2 antagonism properties.
• Patients at risk for unopposed alpha stimulation may receive another alpha adrenergic antagonist before labetalol.

Angiotensin-Converting Enzyme (ACE) Inhibitors

• ACE inhibitors alter the function of the renin-angiotensin system, which causes vasoconstriction and fluid retention in response to hypotension or hypoperfusion.
• ACE inhibitors cause decreases in blood pressure and cardiac afterload.
• ACE inhibitors are useful for treating hypertension, cardiomyopathy, and CHF.
• Patients taking ACE inhibitors may experience a chronic dry cough and sudden life-threatening angioedema.
• Close monitoring and supportive treatment are necessary for patients on ACE inhibitors.
• Intubation can be extremely difficult in patients experiencing angioedema.

Anticholinergic Medications

• Anticholinergic medications treat cholinergic symptoms associated with excessive acetylcholine release.
• Atropine is a competitive muscarinic receptor agonist.
• Atropine's effect depends on its concentration at receptor sites compared with acetylcholine (ACh).
• Massive atropine doses may be required when ACh increases dramatically due to acetylcholinesterase inhibition.
• Atropine is used for bradycardia and suspected vagal stimulation of muscarinic 2 receptors.
• Atropine is administered empirically to exclude vagal stimulation during bradycardia of unidentified cause.
• Atropine is unlikely to be effective for bradycardia caused by blocked cardiac conduction (heart blocks).
• Atropine is used before airway manipulation to prevent drug-induced bradycardia and suppresses saliva and other airway secretions.

Catecholamines and Sympathomimetics

• Catecholamines and sympathomimetics are naturally occurring chemicals that stimulate receptor sites in the sympathetic nervous system.
• Endogenous catecholamines include epinephrine, norepinephrine, and dopamine.
• Endogenous catecholamines are rapidly metabolized with a brief duration of action.
• Synthetic chemicals mimicking catecholamines include amphetamines, albuterol, cocaine, and phenylephrine.
• Synthetic chemicals mimicking catecholamines have a longer duration of action.
• Epinephrine (adrenaline) stimulates alpha, beta 1, and beta 2 receptor sites.
• Epinephrine causes potent vasoconstriction and increases heart rate, contractility, and cardiac output.
• Epinephrine causes powerful bronchodilation and can be administered IV, IO, IM, SubQ, ET, and via nebulizer.
• Epinephrine can dramatically increase cardiac workload and myocardial oxygen demand.
• Norepinephrine (Levophed) stimulates beta 1 and alpha receptor sites.
• Norepinephrine causes an increase in blood pressure, cardiac contractility, and heart rate.
• Norepinephrine Indications include sepsis, neurogenic shock, and anaphylactic shock.
• Norepinephrine is administered by continuous IV infusion, titrated according to patient response.
• Norepinephrine can cause tissue necrosis if extravasation occurs, requiring frequent IV site reassessment.
• Central venous catheter administration is advised, if available.
• Dopamine is used as a primary medication for hypotension refractory to volume resuscitation.
• Dopamine is administered using a weight-based infusion calculation, with clinical effects varying dramatically by dose.
• Dopamine dose of 2.5-5 mcg/kg/min causes renal and mesenteric artery vasodilation.
• Dopamine dose of 5-10 mcg/kg/min causes increased heart rate and contractility.
• Dopamine dose of 10-20 mcg/kg/min causes vasoconstriction.
• Dobutamine is a synthetically manufactured catecholamine similar to dopamine.
• Dobutamine does not activate dopaminergic receptors but stimulates beta 1, beta 2 and alpha receptors.
• Dobutamine may increase heart rate and provide inotropic effects.
• Dobutamine is administered with an infusion pump with careful cardiac and hemodynamic monitoring.
• Hypotension is a possibility with Dobutamine.
• Milrinone is similar in functionality to dobutamine and can be given orally or IV for heart failure.
• Milrinone increases cardiac contractility while causing dilation of systemic arteries and veins.
• MIlrinone improves cardiac output but increases mortality when used over long periods.
• Phenylephrine is a synthetic, almost pure alpha agonist medication.
• Phenylephrine is used by paramedics as a mucosal vasoconstrictor for artificial airway placement.

Digitalis Preparations

• Digitalis preparations are prescribed for chronic heart failure or certain rapid atrial dysrhythmias.
• DIgitalis increases the strength of cardiac contractions, improving cardiac output and slowing conduction through the AV junction.
• Digitalis allows fewer impulses to be conducted to the ventricles, slowing the overall heart rate.
• Digitalis may produce a wide variety of adverse reactions, including virtually any cardiac dysrhythmia.
• Dysrhythmias are caused by the toxic effects of digitalis.
• Patients are sensitive to calcium preparations and a decline in serum potassium levels while taking Digitalis.
• Common digitalis preparations include digoxin and digitoxin.

Vasodilator Medications

• Vasodilator medications are used for the management of uncontrolled hypertension, congestive heart failure, myocardial infarction, cardiac ischemia and cardiogenic shock.
• Nitroglycerin dilates veins and coronary arteries.
• Nitroglycerin decreases cardiac preload, reduces myocardial oxygen demand, and improves coronary circulation when administered sublingually by tablet or spray.
• Effects following IV administration begin almost immediately and persist only for a few minutes.
• Sublingual nitroglycerin tablets need to be stored in a closed, light-protected container for degradation.
• Nitroglycerin binds with plastic containers and IV fluids or tubing, so glass bottles should be used.
• Patients taking nitroglycerin should not be taking ED medications due to the risk of severe hypotension.
• Sodium nitroprusside (Nipride) is a potent IV vasodilator affecting smooth muscle in veins and arteries.
• Sodium nitroprusside is often used with inotropic medications for cardiogenic shock.
• Sodium nitroprusside is also used for malignant hypertension and in situations where intentional hypotension is desired.
• Sodium nitroprusside requires an adjustable IV infusion rate to maintain optimal blood pressure and cardiac output.
• Sodium nitroprusside should be administered by continuous IV infusion with frequent or constant blood pressure monitoring.
• Sodium nitroprusside has rapidly decreasing effects once infusion is discontinued.
• Sodium nitroprusside is metabolized into cyanide and thiocyanate so can cause toxicity during prolonged infusion.
• Hydralazine can be used for patients with pregnancy-induced hypertension.
• Hydralazine dilates arterioles, lowering pulmonary and systemic vascular resistance.
• Nesiritide is a potent vasodilator impacting pulmonary and systemic blood vessels which inhibits platelet aggregation.
• Continuous infusions for some patients are needed.
• Nesiritide is not typically administered to patients for the first time in the prehospital setting.
• Adverse effects of Nesiritide include tachycardia, palpitations, cardiac dysrhythmias, bleeding, and flushing.
• Online medical control consultation should be used if considering adjustments to the continuous infusion rate.

Diuretic Medications

• Diuretic medications are administered to correct volume overload and manage heart failure.
• Diuretic medications improve respiration in patients with pulmonary edema.
• Diuretic medications help preserve kidney function, eliminate certain toxins, and promote excretion of excess electrolytes.
• Loop diuretics disrupt sodium reabsorption (e.g., Lasix/furosemide).
• Potassium-sparing diuretics impair sodium reabsorption in the cortical collecting tubule of the kidney (e.g., spironolactone).
• Furosemide is used in the management of hypertension, CHF, liver disease, or kidney dysfunction.
• Careful consideration before administering furosemide to patients who are hemodynamically unstable or have known electrolyte disturbances is crucial.
• Furosemide is administered IV over 1-2 minutes per 40mg dose.
• Mannitol is an osmotic diuretic used to decrease intracranial pressure associated with cerebral edema.
• Mannitol can target specific body tissues while removing excess water from the brain and eyes.
• Mannitol draws water out of selected body tissues through the kidneys.

Antihypertensive Agents

• Many diuretics are also used as antihypertensives or in combination with them.
• Beta blockers may also be used in the treatment of hypertension.
• Patients taking antihypertensives may have symptoms of hypotension.
• Orthostatic hypotension is the feeling of giddiness due to hypotension with a change in position when sitting down and then standing up too quick.