Pathophys ch 16

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Pathophys ch 16
2010-02-08 14:09:23

Alterations in Blood Pressure
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  1. Hypertension:
    adult BP persistently elevated 140 systolic, 90 diastolic or both. (120/80 or less is better)
  2. Risk factors:
    Increasing age, race (esp. African-Americans), obesity, high-sodium diet, genetics, smoking, sedentary life style.
  3. Classifications of Hypertension:
    i. Primary (essential or idiopathic) hypertension—95% of cases

    ii. Secondary hypertension—can be explained by a specific disease.

    iii. Isolated systolic hypertension in the elderly—affects about ½ of people > age 65;

    iv. Hypertension during pregnancy—BP normally decreases in 1st & 2nd trimesters, returns to normal in 3rd.

    v. Accelerated (malignant) hypertension—rapidly progressive, potentially fatal; diastolic BP > 120; present < 1% of hypertensives; 1-year mortality if untreated = 90%!
  4. Primary (essential or idiopathic) hypertension—95% of cases. Physiology (3 points):
    i. renin-angiotensin-aldosterone system

    ii. Vascular endothelium is a hormone-producing endocrine gland in its own right—endothelin-1 in particular is vascoconstrictive.

    iii. Hyperinsulinemia & insulin resistance—account for about ½ of all cases of essential hypertension.
  5. Secondary hypertension—can be explained by a specific disease. (3 then drugs):
    i. Renal disorders—most common cause; for instance, renal artery stenosis causes reduced renal perfusion & activation of the renin-angiotensin-aldosterone system.

    • ii. Endocrine disorders (these are examples—not an exhaustive list)—
    • a. Adrenocortical hormone excess (both mineralocorticoids & glucocorticoids)
    • 1. Steroid hormones are synthesized from cholesterol.
    • b. Pheochromocytoma (rare, but obvious)-tumor of the adrenal gland that causes too
    • much release of epinephrine and norepinephrine
    • c. Acromegaly
    • d. Hypo- or hyper-thyroidism

    • iii. Vascular disorders
    • a. Arteriosclerosis—increases systemic vascular resistance, therefore blood pressure; also narrows renal arteries as in #1 above
    • b. Coarctation of the aorta—markedly elevated BP in arms, low BP in legs
    • c. Neurologic disorders—elevated intracranial pressure, spinal cord injuries can cause autonomic hyperreflexia

    iv. Drugs—amphetamines, steroids, oral contraceptives, caffeine, nicotine, cocaine, etc.
  6. Isolated systolic hypertension in the elderly—affects about ½ of people > age 65;
    Defined as systolic BP > 140 with diastolic < 90

    More common in women

    Associated with decreased arterial distensibility
  7. Edema means:
    swelling caused by fluid in your body's tissues. It usually occurs in the feet, ankles and legs, but it can involve your entire body
  8. Hypertension during pregnancy—BP normally decreases in 1st & 2nd trimesters, returns to normal in 3rd.
    i. Complicates 12-22% of pregnancies; defined as BP > 140/90 after 20 weeks of pregnancy

    • ii. Predisposing factors
    • a. Young (teenage) & older (late 30’s & 40’s) mothers
    • b. Multiple fetuses
    • c. Preexisting diabetes, HTN, renal, or cardiovascular disease

    • iii. preeclampsia—elevated BP, proteinuria-protein is urine, & edema
    • a. a serious threat to mother & fetus

    iv. eclampsia—further progression to seizures & possibly coma

    v. Chronic hypertension may also pre-date pregnancy & continue into & through it.

    vii. complicates 0.5-10% of pregnancies in US; elevated BP accompanied by proteinuria.
  9. Renin-angiotensin mechanism (aldosterone)in primary hypertension:
    i. Kidney bp drops--> Juxtaglomerular apparatus secretes renin into blood.

    ii. Renin (an enzyme)- causes angiotensinogen (in blood) to be converted to angiotensin I.

    iii. Angiotensin I circulates to lungs where enzymes convert it to angiotensin II.

    iv. Angiotensin II circulates to adrenal cortex, stimulating aldosterone secretion.

    v. Aldosterone causes increased Na absorption thus water retention, increasing blood volume = increased BP.

    vi. Higher BP causes renin secretion to stop.
  10. Cardiac Effects of hypertension—
    i. left ventricle (LV) must work harder to overcome resistance to ejection of blood (afterload).

    ii. This causes LV hypertrophy,

    iii. increases myocardial O2 consumption,

    iv. raises risk of ischemia, heart failure.
  11. Vascular effects of hypertension-
    i. Atherosclerosis & arteriosclerosis—lesions in brain, retinas, kidneys.

    HTN is one of the leading preventable causes of renal failure
  12. Signs & symptoms of hypertension—very few!! “silent killer”
    a. Signs/symptoms usually only appear when target organ damage occurs.

    b. Strokes and all forms of cerebrovascular disease

    c. Coronary artery disease in all its forms;

    d. Development & rupture of aortic aneurysms;

    e. Renal problems—

    i. Proteinuria—loss of protein in urine,

    ii. Nocturia—urination during sleeping hours

    iii. Azotemia—accumulation of nitrogenous wastes in the blood stream)
  13. Diagnosis of hypertension—made after a minimum of 2 BP measures on separate occasions.
    a. Ambulatory blood pressure monitoring may play an increasing role.
  14. Management—goal should be AT LEAST 130/80
    a. Lifestyle modifications—weight reduction, decrease alcohol consumption, sodium restriction, high K+ & Ca2+ intake, exercise, cholesterol reduction

    • b. Medications—
    • i. Typically begin with diuretics or β-blockers
    • ii. ACE (angiotensin converting enzyme) inhibitors & angiotensin receptor blockers useful in hypertension, congestive heart failure & diabetes.
    • iii. Good enough for us, but lots of other info out there!
  15. 6. Low blood pressure
    a. Shock—inadequate blood pressure to perfuse vital organs. More later.

    b. Orthostatic hypotension—excessive drop in blood pressure when upright posture assumed. If present in elderly, care must be taken to minimize risk of falling, fractures, etc.