10 Alterations in Blood Pressure

Alterations in Blood Pressure  Formula for Blood Pressure o Blood pressure= Cardiac Output x Systemic Vascular Resistance  Vascular resistance- coming from a number of different components mostly sympathetic tone  When we’re measuring blood pressure- we’re measuring the force applied to the artery walls o   The distribution of systolic and diastolic pressure throughout the circulatory system starting with 120 over 70 in the arteries and then gradually falling off into much lower pressure in the veins  The pressure will vary depending on whether the ventricle is contracting or relaxing  During systole- 120  During diastole- it drops to 70 or 80 Factors Affecting Cardiac Output o Heart rate  The faster the heart is beating, the faster the cardiac output o Contractility of the heart muscle o Preload- volume work of the heart, amount of blood coming in the ventricle before the heart contracts o Afterload- pressure work of the heart, amount of pressure the blood has to pump against  Increased afterload occurs with increased resistance to ejection of blood from the ventricle  Increased systemic vascular resistance   Increased diastolic blood pressure  Aortic stenosis  (Anything that makes it harder for the ventricle to pump out)  Increased afterload  decreased stroke volume Control of Blood Pressure o Baroreceptors: SNS  Sends information to SNS o Hormones  *Renin-angiotensin-aldosterone  *Antidiuretic hormone  Adrenal catecholamines- more localized  Atrial natriuretic peptide- more localized o Paracrine mediators  Nitric oxide, endothelin o Renal mechanisms o      When our blood pressure falls, the kidney will release renin which combines with angiotensinogen from the liver The renin then is converted into angiotensin 1 and travels to the lungs where angiotensin-converting enzyme in the lung capillaries converts it to angiotensin 2 Angiotensin 2 goes to the adrenal cortex, tells it to release aldosterone which causes retention of sodium and water Angiotensin 2 also causes vasoconstriction Between those 2 mechanisms the blood pressure should go back up again  Think of aldosterone as a saline hormone- the one responsible for both sodium and water o    Puts together some of these mechanisms  All work together to keep blood pressure in normal range Hypertension Definition o Hypertension is sustained elevation of BP o Systolic blood pressure > 140 mm Hg o Diastolic blood pressure > 90 mm Hg o This is an either/or, you don’t need to have both elevated to be given a diagnosis of hypertension o Normal BP: <120/80 o Prehypertension: 120-139 / 80-89 o Hypertension stage 1: 140-159 SBP or 90-99 DBP o Hypertension stage 2: >160 SBP or >100 DBP o Hypertension stage 3: >180 SBP or >110 BDP o It’s the higher number that determines the category  Ex: if diastolic is below 80, but systolic is 145, they we say they have stage 1 hypertension Classification of hypertension o Primary (essential) hypertension  Elevated BP without an identified cause  90% to 95% of all cases (majority)  Several contributing factors: (not direct causes)    SNS activity  Diabetes mellitus (especially Type 2)  Sodium intake  Excessive alcohol intake Pathophysiology of primary hypertension (influences)  Heredity/family history o Level of HTN is strongly familial o In most cases results from the interaction of:  Genetic factors  Environmental factors  Demographic factors  Water and sodium retention o A high sodium intake may activate a number of pressor mechanisms and cause water retention and to have a higher BP  Altered Renin-Angiotensin mechanism o May contribute to the development and maintenance of hypertension  Stress and increased SNS activity o Produces increased vasoconstriction o Heart rate o Renin release  Risk factors for Primary Hypertension  Age- increasing age  Alcohol  Cigarette smoking  Diabetes mellitus (type 2)  Elevated serum lipids  Excess dietary sodium    Gender o Varies throughout the lifespan, a little more common in men in younger age and more common in women in older age  Ethnicity- African Americans are at higher risk  Sedentary lifestyle  Socioeconomic status- low SES  Stress  Family history  Obesity o Secondary hypertension  Elevated BP with a specific cause  Some other disease causes the BP to be high  Ex: renal abnormality  5% to 10% in adults  Pathophysiology of secondary hypertension  Common contributing factors: (specific causes that we can identify, not just general risk factors) o Coarctation of aorta o Renal disease (common) o Endocrine disorders o Neurologic disorders  Other causes of secondary hypertension: o Contraceptive use o Renal artery stenosis o Cushing syndrome o Pheochromocytoma o Pregnancy-induced hypertension o Polycythemia o Sleep apnea o Drug-induced  Cocaine  Ephedra  NSAIDs o Hyperthyroidism o Primary aldosteronism Blood Pressure Targets for Treatment o Uncomplicated hypertension:  <140 systolic and <90 diastolic o With diabetes or chronic kidney disease  <130 systolic and <80 diastolic Hypertension Clinical Manifestations  o Frequently asymptomatic until it becomes severe and target organ disease has occurred  Fatigue, reduced activity tolerance  Dizziness  Palpitations, angina  Dyspnea Hypertension Complications o The common complications are target organ diseases occurring in the  Heart  Brain  Kidney  Eyes o There can be damage occurring without symptoms (why it is often referred to as “The Silent Killer”) o Increased risk of stroke, heart attack, heart failure, kidney failure o Hypertensive Heart Disease  Coronary artery disease  Left ventricular hypertrophy  Heart failure o Cerebrovascular Disease  Stroke/CVA o MI o Peripheral Vascular Disease o Nephrosclerosis- damage to kidneys o Retinal damage o   Potential changes you could see, any of the blood vessels can be affected, the heart, kidneys, aneurysms, stroke, and retinal damage Hypertension Diagnostic Studies o History and physical examination     o BP measurement in both arms  Use arm with higher reading for subsequent measurements  BP highest in early morning, gradually falls during the day, lowest at night o Routine urinalysis- to see effect of kidneys o Serum electrolytes o BUN and serum creatinine o Serum lipid profile- to see if cholesterol is high o ECG- to see if there’s heart damage Benefits of Lowering BP o o Lowering BP  it can have a significant effect on the complications they’re likely to develop Hypertension o For persons over age 50, SBP is more important than DBP as a CVD risk factor (but both numbers are important) o Starting at 115/75 mmHg, CVD risk doubled with each increment of 20/10 mmHg (mercury) throughout the BP range o Persons who are normotensive at age 55 have a 90% lifetime risk for developing HTN Hypertension in Older Persons o More than two-thirds of people over 65 have HTN o This population has the lowest rates of BP control Hypertension Minority Populations o Prevalence and severity of HTN increased in African Americans (but not for Africans living in Africa), combination of diet/SES/genetics o In general, treatment similar for all demographic groups o Socioeconomic factors and lifestyle important barriers to BP control    Complication- Hypertensive Crisis o Severe, abrupt elevation in BP o The rate of in BP is more important than the absolute value o In patients with a history of HTN who have failed to comply with medications or who have been under-medicated o Hypertensive crisis Clinical Manifestations  Hypertensive encephalopathy (brain damage)  Renal insufficiency  Heart failure  Pulmonary edema  Diaphoresis Pregnancy Induced Hypertension (PIH) o Also called toxemia of pregnancy and preeclampsia (mean the same thing) o Risk factors:  Young maternal age  First pregnancy  Multiple fetuses (twins, triplets, etc.)  Diabetes  Previous hypertension o Pathology  Not well understood  Should be open and free blood flow through placenta, with PIHsomehow the vessels constrict and we get less blood flow than normal and raises the BP o Manifestations:  Hypertension  Proteinuria- skill protein in urine  Edema (very common in late pregnancy for legs/feet, but this edema is in hands/face)  Sudden weight gain (5 lbs overnight)  Vision changes- blurred vision, spots  Nausea and vomiting o Complications:  Eclampsia  Seizure activity in mother during late pregnancy, can be very dangerous for mother/baby, can result in maternal/fetal demise  HELLP syndrome  Hemolysis- breaking down of RBCs  Liver changes  Low platelets  Fetal and/or maternal death Orthostatic Hypotension o Drop in systolic pressure >20 mmHg or pulse increase >20 bpm o Causes: hypovolemia, dehydration (poor thirst mechanism in elderly), prolonged bed rest, blood loss  When we stand up o More common in the elderly o S&S: dizziness, light-headedness, syncope, fainting o   The way things should work when BP drops Baroreceptors sense that and send feedback to SNS, between various mechanisms the BP should come right back up, but not with orthostatic hypotension