Hypertension: the silent killer Leslie Mickles, RN, MSN Statistics • Afflicts almost 1 billion people worldwide and is a leading cause of morbidity and mortality. • More than 20% of Americans are hypertensive, and one-third of these Americans are not even aware they are hypertensive. Blood Pressure Physiology Pressure in cardiovascular system controlled by: •Heart rate •Stroke volume: • Actual blood volume • Contractility •Total peripheral resistance: • small arterioles are most important due to small diameter and ability to constrict to the point of almost stopping blood flow. Compensatory Mechanisms Effecting BP • Baroreceptor reflex • Carotids and Aortic Arch • Brainstem to the vasomotor centre (VMC) • Activation of the sympathetic nervous system • increased contractility of the heart (beta receptors) • vasoconstriction of both the arterial and venous side of the circulation (alpha receptors) • Renin-angiotensin system (RAS) • Aldosterone release Renin Angiotensin Cycle Receptor Tissue Stimulation Causes Subtype Stimulation of these receptors in the heart produces a more rapid heart rate as well as more forceful heart Heart Muscle muscle contractions. Drugs that stimulate beta1 beta 1 and Fatty Tissue receptors may, therefore, be useful in the treatment of clients with depressed cardiac function Stimulation of the beta2 receptors in bronchial muscle Smooth Muscle results in muscle relaxation, thereby increasing the of the Peripheral diameter of the air channels and promoting improved Vasculature and beta 2 gas exchange. Beta2 stimulants (agonists) are sometimes Airway used, therefore, to treat bronchial asthma or other (bronchial) conditions marked by breathing difficulty. When alpha1 (α1) receptors are stimulated, either by a Peripheral Blood neurotransmitter or a drug, the smooth muscle Vessels and associated with them contracts. This contraction may alpha 1 Sphincters of GI result in an increase in blood pressure due to and GU Tracts constriction of peripheral blood vessels. These receptors seem to function as “controllers” of Located on the neurotransmitter release by the presynaptic neuron. Presynaptic alpha 2 Inhibition of tansmitter release causes hypotension, Neuron anaesthesia, vasoconstriction Receptor Sites Stumulation alpha-receptor beta-receptor vasoconstriction vasodilation (b2) iris dilation cardioacceleration (b1) intestinal relaxation intestinal relaxation (b2) intestinal sphincter uterus relaxation (b2) contraction bladder sphincter contraction bronchodilation (b2) Hypertension Definitions • Hypertension is a systolic BP >140 and a Diastolic BP >90 based on the average of two or more correct blood pressure measurements taken during two or more contacts with a health care professional. Types of Hypertension • Primary (essential) Hypertension: means the cause can not be identified (90-95%) • Secondary Hypertension: cause can be traced to some underlying disorder (e.g. renal disease, tumor of the adrenal medulla) 5% Identifiable Causes • Drug induced • Renal failure • Primary aldosteronism • Renovascular disease • Thyroid and parathyroid disease Risk Factors • Smoking • Age • Gender • Race • Family history • Obesity • Stress • Excess Sodium intake • Alcohol intake • Elevated serum lipids Cultural Considerations African Americans develop hypertension earlier in life, and it is more severe at any decade of life. The estimated prevalence of individuals with hypertension in the population at large is as follows: POPULATION MALES FEMALES American Indians 26.8% 27.5% African Americans 35.0% 34.2% Anglo-Americans 24.4% 19.3% Asian/Pacific Islanders 9.7% 8.4% Cuban Americans 22.8% 15.5% Mexican Americans 5.2% 22.0% Puerto Ricans 15.6% 11.5% (American Heart Association, 1999d) Aging Effect on BP • As one ages there is an accumulation of atherosclerotic plaque in arteries. • Arteries become less elastic. • Since arteries are less elastic the arterial pressure is elevated with the force of blood being pumped out from the left ventricle. BP SBP DBP Lifestyle Meds Class (mm Hg) (mm Hg) Mod Normal <120 <80 Enc No meds indicated PreHTN 120-139 80-89 Yes No Meds indicated Stage I 140-159 90-99 Yes Thiazide HTN Diuretics, (poss ACE, CCB.ARB, BB) Stage II 160 100 Yes Two meds HTN Target Organs Damaged by Hypertension • Heart (Angina, MI, hypertrophy, failure) • Brain (TIA or Stroke) • Eyes (loss of vision, retinopathy) • Kidneys (chronic renal failure) • Peripheral artery disease Manifestations • Retinal hemorrhages • Visual changes • Papilledema (swelling of the optic nerve) • Headaches • Heart failure, or chest pain • Slurred speech, hemiparesis, weakness – suggestive of TIA (temporary) or CVA • Elevated BUN and Creatinine Treatment • Identify underlying cause if possible • Keep BP <140/90 • Stepped Care Approach • Step I: Life style modifications: wt reduction, restrict Na intake, stop smoking, reduce alcohol consumption, reduce stress, increase exercise. • Step II: One medication started, usually a diuretic, but may be an ARB, ACE inhibitor or calcium channel blocker. • Step III: If ineffective, change dose or class of antihypertensive med or add a second medication. • Step IV: Adjustment of previous dosages, and addition of another antihypertensive med until desired control of BP obtained. Note many medications come as a fixed combination of drugs Hypertensive Crisis • Hypertensive Emergency: • A situation in which the BP must be lowered immediately to halt damage to target organs • Hypertensive Urgency; • situation in which BP must be lowered with a few hours. Hypertensive Crisis • Treatment: • Arterial line • Intravenous medication – typically nipride or nitroglycerin • May also use cardene, or IV vasotec • Lower BP but with MDs parameters. Typically not below 140/90 or you will impede cerebral perfusion • Supportive care for any symptomatology Hypertensive Urgency • Managed with oral medication such as • Fast acting loop diuretics (Lasix, Bumex) • ACE inhibitors, ARBs, calcium channel blockers, beta blockers • Close monitoring of BP – A line or Dynamap cycling Loop Diuretics Action Named because the work int eh loop of Henle. Block the chloride pump in the ascending loop of Henle (where normally 30% of all filtered Na is reabsorbed) decreasing Na reabsorption and producing copious amounts of urine. Naming Generic names tend to end in “…ide” i.e. furosemide (Lasix), bumetanide (Bumex), torsemide (Demadex). Indication Used in treatement of severe edema, acute pulmonary edema, CHF or hypertension because they can precipitate the lose of up to 20 lbs of water per day. Preferred diuretic for rapid and extensive diuresis. Contraindication Hypersensitivity, electrolyte imbalance, anuria, severe renal failure, hepatic coma, pregnancy and lactation. Adverse Effects Hypokalemia, alkalosis (due to lose of bicarb with urine), hypotenison, dizziness, ototoxicity and even deafness, hyperglycemia (with long term use), dehydration/ hypovolemia. Nursing Teaching regarding daily weights, potassium replacement. Considerations Report signs of hypotension or hypovolemia. Also monitor BUN and creatinine to ensure not overly dehydrated. Thiazide Diuretics Action Belong to the chemical class of drugs called sulfonamides. They work by blocking the chlorides movement out of the renal tubules (and thereby Na+ movement). Blocking the chloride pump keeps the Na and Cl in the tubules for excretion in the urine. Naming Generic name tends to end in “….thiazide” i.e. hydrochlorothiazide (Hydrodiuril), chlorothiazide (Diuril), bendroflumethiazide, (Naturetin), hydroflumethiazide (Saluron), methyclothiazide (Enduron) Indication Monotherapy or adjunctive thearpy for hypertension. Also, treatement of edema associated with CHF or with liver or renal disease. Mild diuretics compared to loop diuretics. Contraindication Hypersensitivity, fluid or electrolyte imbalance, renal and/or liver disease. Pregnancy and lactation. Adverse Effects GI upset, CNS complications, hypovolemia, hypokalemia, hypovolemia/dehydration. Nursing Monitor fluid and electrolyte balance closely, especially for Considerations hypokalemia. Hypokalemia may cause leg cramps and cardiac arrhythmias. Also monitor BUN and creatinine to ensure not overly dehydrated. Potassium Sparing Diuretics Action Potassium-sparing diuretics decrease sodium reabsorption at collecting tubules, inducing diuresis; decrease activity of aldosterone at collecting tubules. Naming No common ending to their names. Include: amiloride (Midamor), sprionolactone (Aldactone), and triamterene (Dyrenium) Indication Particularly useful in treating hypertension and edema associated with CHF in patients at high risk if hypokalemia would develop (i.e. patients on digoxin). Drug of choice for hyperaldosteronism. Contraindication Hypersensitivity, hyperkalemia, renal disease, or anuria. Adverse Effects Hyperkalemia which can lead to lethargy, confusion, ataxia, muscle cramps and cardiac arrhythmias. Nursing Closely monitor fluid and electrolyte balance (especially K+). Considerations Also monitor BUN and creatinine to ensure not overly dehydrated. Vasodilators: Nitroprusside Action Liberates nitric oxide (-NO)spontaneously in solution and thus causes arteriolar and venous dilitation. Indication Nipride is indicated for immediate reduction of BP in hypertensive crisis. Also utilized post-op to control blood pressure and reduce bleeding (i.e. post craniotomy). Utilized to reduce afterload and preload and thereby improving Cardiac Output in CHF and Cardiogenic Shock. Contraindication Hypersensitivity to nitroprusside or any component of the formulation; treatment of compensatory hypertension (aortic coarctation, arteriovenous shunting) Adverse Effects Cyanide toxicity. Thiocynate levels > 100 mcg/ml may cause: drowsiness, lethargy, nausea and vomiting and muscle twitching progressing to convulsions and coma. High concentrations suppress thyroid function Nursing Light sensitive. Infusion bag must be covered to block light and Considerations changed every 24 hours to prevent more rapid degredation to thicynate. Monitor for manifestation of cyanide toxicity.
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