Lecture 6: Hypertension

Lecture 6: Hypertension Hypertension · most common form of cardiovascular disease · closely linked to diet and lifestyle factors · BMR = 10 calories/Ib ↑ Blood Pressure · 3 elements of BP: ① Blood Volume - fluid loss, fluid retention ② Peripheral Resistance - SNS, renin-angiotensin, viscosity ③ Cardiac output - stroke volume, HR ↳ Preload: Stretching of the heart prior to contraction ↳ Afterload: the force against which the heart has to contract to eject the blood ↳ Contractility: the ability of the heart to contract BP Review: · expected findings: ↳ BP = 120/80 ↳ MAP: 70-100 ↳ CO = SV + HR (usually 70 mL) · CPP = MAP - ICP ↳ CPP = 55-60 ↳ ICP: 5-15 · Hypertension if SBP > 135 High BP 3 Types of Hypertension: ① Essential Hypertension (idiopathic) ② Secondary Hypertension ↳ Gestational Hypertension ③ Sudden Onset Hypertension Low BP Age & HTN · decreased elasticity of vessels, increased PVR, renal blood flow, baroreceptor sensitivity ① Essential Hypertension (ideopathic) · hard to know exact cause · age, diet, ethnicity, gender, lifestyle · BW: glucose, electrolytes, creatinine clearance, cholesterol, lipids · TX: collect data, focus on modifiable risk factors, tx BP PRN & titrate to effect, BW - ② Secondary Hypertension · organ disease (eg. diabetes, renal, adrenal, congenital defects) · pregnancy ↳ TX: BW, treat cause, tx BP - Gestational Hypertension (preeclampsia) · blood volume increase by 50% · > 20 weeks gestation · inflammatory etiology: clotting, organ damage, placental flow compromised, risk of DIC · TX: sodium restriction, antihypertensive medications ↳ Labetalol (beta blockers) IV locations: median cubital (anticubital), median antibrachial, ulnar, or external/internal jugular in babies or no other option ③ Sudden Onset Hypertension · sudden change of > 20 mmHg · assess patient for cause: ↳ pain, infection, hypervolemia, drug induced (stimulants) · TX: treat the cause, tx BP PRN · if SBP > 180 ↳ malignant HTN = medical emergency!! ↳ concern for hemorrhage and organ damage - HTN Drug Classes: 1. Direct Acting Vasodilators 2. Diuretics 3. Renin-Angiotensin Drugs ↳ ACE inhibitors ↳ Angiotensin II Receptor Blockers 4. Calcium Channel Blockers 5. Adrenergic Antagonists (Beta Blockers) 6. Centrally Acting A2 Adrenergic Agonists - Retinopathy (bleed) Aorta can split Kidneys shut down Orthostatic Hypotension · sudden drop of SBP > 20 mmHg or DBP > 10 ↳ venous pooling in lower extremities (elevate legs) · S&S: faintness, dizziness (decreased CNS perfusion) · at risk: elderly, dehydrated or fluid restricted, antihypertensive medications · tx: titrate drugs, adrenergic agonists ↳ phenylephrine is selective for alpha 1 - 1. Direct Acting Vasodilators · emergency treatment for hypertension → malignant hypertension · MOA: Stimulates NO synthesis + secretion from endothelial cell causing vasodilation ↳ s/e: reflex tachycardia, hypotension, syncope, headache · Drugs: Nipride (Nitroprusside), Hydralazine ↳ IV t1/2 = 2 mins ↳ lower BP to 165 then titrate down slowly - 2. Diuretics · increases urine output, decreases blood volume, lowers BP ↳ decreases H2O and electrolytes * · 1st line HTN treatment · 4 types (drug classes) ① Loop ② Thiazides ③ Potassium Sparing ④ Osmotic (note: not for HTN) · side effects of diuretics: ↳ dehydration ↳ hyponatremia, ↳ hypokalemia (loop & thiazide), ↳ hyperkalemia (potassium sparing), ↳ Nocturia Thiazides - Loop K+ Sparing 4 Groups of Diuretics ① Loop Diuretics ("high ceiling") · Blocks Na, Cl, K reabsorption in ascending loop of henle leading to water loss upon secretion of Na, Cl, and K · s/e: hypokalemia, ototoxicity, drug interactions (high PPB) · Drug: Furosemide (Lasix) ② Thiazide Diuretics * · decreases the reabsorption of Na, Cl, K in distal convoluted tubule leading to water loss upon secretion of Na, Cl, and K · s/e: hypokalemia “-thiazide” suffix · Drugs: Hydrochlorothiazide (HZTZ), Chlorothiazide (Diuril), Metolazone (Zaroxolyn) ③ Potassium Sparing Diuretics ("Aldosterone Antagonists") · antagonizes renal aldosterone in the collecting distal tubule which causes Na to leave and K to stay · s/e: hyperkalemia (long +↳ 1/2 of 1-2 days) · Drugs: Spironolactone (Aldactone) ↳ combo drug: Aldactazide (spironolactone + hydrochlorothiazide) - good for maintenance, frequently out of stock, balances out K+ (hyper/hypo) ④ Osmotic Diuretics · Drugs: mannitol (Osmitrol), Isosorbide · high solute, travels unchanged, excretes water with it · MOA: pulls water into circulation & into renal tubules (proximal & loop of henle) ↳ also inhibits renin release · TX: cerebral edema, intraocular hypertension, low use for CV * - 3. Renin-angiotensin Drugs ACE Inhibitors · "Angiotensin-converting enzyme inhibitors" · Inhibits ACE enzyme causing vasodilation · very potent, clinical urgency “-pril” suffix · 1st line drugs in heart failure · s/e: severe hypotension, angioedema of tongue, low RBC production · Drugs: Captopril, Ramipril (Altace), Enalapril (Vasotec), Monopril - - Long term idiopathic HTN Angiotensin II Receptor Blockers (ARBs) · blockers = antagonists · MOA: angiotensin II receptors are antagonized leading to decreased afterload and preload ↳ slow onset (a few weeks) · s/e: hypotension “-tan” suffix · Drugs: Losartan (cozaar), Ibesartan (Avapro) ↳ combo drug: Hyzaar, Cosart (thiazide diuretic + ARB) - ACE um ARB - 4. Calcium Channel Blockers · muscle contraction is regulated by calcium · MOA: CCBs block calcium from entering the cell, limiting muscular contraction · Drugs (2 types): 1)Vascular-selective: smooth muscle ↳ Nifedipine (Adalat), Amlodipine (Norvasc) 2)Cardio-selective: cardiac muscle ↳ Verapamil (Isoptin), Diltiazem (Cardizem) · Herbal Therapies → Ginseng - - Ginseng is weird for working like a CCB 5. Adrenergic Antagonists “Beta Blockers” · MOA: antagonism of the SNS at various adrenergic receptors which decreases catecholamine activity ↳ alpha 1, alpha 2, beta 1, beta 2 Note: Drug does opposite effect Alpha 1 Beta 1 · vasoconstriction · cardiac muscle: increased myocardial activity and HR · pupil dilation · AV node conduction · increased closure of urinary sphincter · secretions Beta 2 Alpha 2 · brochodilation · vasoconstriction · vasodilation · decreased GI motility · increased breakdown of glycogen and increased · decreased smooth muscle motility release of glucagon · contraction of male genitalia during ejaculation Drugs: Prazosin (alpha 1), Phentolamine (alpha 1 & 2) Drugs: Atenolol (beta 1), Propanolol (beta 1 & 2), Metoprolol (beta 1 & high doses cause beta 2) Combo drug: Lopressor HCT (thiazide diuretic + adrenergic antagonist) - - - - No more NE 6. Centrally Acting Alpha 2 Adrenergic Agonists · MOA: agonizes the CNS negative feedback mechanism at alpha 2 receptors of the vasomotor centre leading to the inhibition of NE (promotes vasodilation and lowers BP) · Tx: resistant HTN · s/e: hypotension, headache · Drugs: Clonidine, Methyldopa Note: chronic hypertension is hard on the kidneys