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9. Systemic hypertension primary and secondary, blood pressure measurement
Systemic hypertension, commonly known as high blood pressure, is a prevalent condition globally, impacting a significant portion of the adult population. It's characterized by a persistent elevation in blood pressure readings, which can lead to various serious health complications if not managed effectively. Here’s a detailed breakdown of the condition:
Definition and Prevalence
Systemic Hypertension: Defined as a sustained increase in blood pressure, typically diagnosed when blood pressure readings consistently exceed 140/90 mmHg.
Prevalence: Affects about 30-45% of the general population, with incidence increasing with age—65% of individuals over the age of 60 are affected. It is more common in African Americans, and gender prevalence varies with age; it predominates in males in younger populations but equalizes post-45 years.
Risk Factors and Associations
Age: Risk increases with age due to the natural loss of arterial elasticity.
Race: Higher prevalence and severity observed in African American communities.
Gender: Initially more common in men but becomes equally prevalent in older age groups.
Associated Risks: Hypertension is a major risk factor for cardiovascular diseases including stroke, myocardial infarction (MI), sudden cardiac death, and heart failure. It also contributes to peripheral artery disease and end-stage renal disease.
Blood Pressure Categories
Optimal: Blood pressure below 120/80 mmHg.
Normal: Systolic 120-129 mmHg and diastolic 80-84 mmHg.
High Normal: Systolic 130-139 mmHg or diastolic 85-89 mmHg.
Hypertension: Divided into three grades based on severity:
Grade I Hypertension: Systolic 140-159 mmHg or diastolic 90-99 mmHg.
Grade II Hypertension: Systolic 160-179 mmHg or diastolic 100-109 mmHg.
Grade III Hypertension: Systolic greater than 180 mmHg or diastolic greater than 110 mmHg.
Isolated Systolic Hypertension: Defined as a systolic pressure above 140 mmHg with a diastolic pressure below 90 mmHg, often due to arterial stiffness.
Primary Hypertension (essential)
Primary hypertension, also known as essential hypertension, is a prevalent condition with complex interactions between genetic and environmental factors contributing to its development. Let's explore the risk factors and mechanisms involved:
Overview
Prevalence: Primary hypertension accounts for approximately 85-95% of all cases of hypertension in adults.
Etiology: The exact cause of primary hypertension is largely unknown, but it is thought to result from a combination of genetic predispositions and lifestyle factors.
Risk Factors
Positive Family History:
Genetic predisposition plays a significant role. Having family members with hypertension increases one's risk, suggesting a hereditary component.
Age:
The risk of developing hypertension increases with age. It typically begins to manifest between the ages of 25 and 55.
Ethnicity:
Hypertension is more prevalent and tends to appear earlier and with more severity in the African American population compared to other ethnic groups.
Obesity:
Excess body weight is a strong risk factor. Adipose tissue produces several substances that can increase blood pressure, such as leptin, which may not only increase sympathetic nervous system activity but also cause direct effects on blood vessels.
Diabetes:
Both type 1 and type 2 diabetes are associated with an increased risk of developing hypertension, partly due to shared risk factors like obesity and inflammation.
Smoking and Excessive Alcohol or Caffeine Intake:
These substances can acutely increase blood pressure and, with chronic use, can lead to long-term hypertension.
High Sodium Diet:
Excessive salt intake leads to increased fluid retention, which raises blood pressure. Over time, a high sodium diet can also cause alterations in the balance of vasoactive substances and promote arterial stiffness.
Physical Inactivity:
A sedentary lifestyle contributes to weight gain and poor cardiovascular health, both of which can predispose individuals to hypertension.
Physiological Stress:
Chronic stress can lead to increased adrenal activity, resulting in higher levels of cortisol and adrenaline, which can raise blood pressure by tightening blood vessels.
Pathophysiology
The underlying mechanisms of primary hypertension are multifactorial and not fully understood. However, several theories include:
Neurohormonal Activation: Overactivity of the sympathetic nervous system and the renin-angiotensin-aldosterone system can lead to increased vascular resistance and water retention.
Renal Function: Changes in kidney function can affect salt and water balance, influencing blood pressure control.
Vascular Dysfunction: Changes in the endothelial function and reduced arterial elasticity can increase peripheral resistance, contributing to elevated blood pressure.
Secondary Hypertension
The text you provided discusses secondary hypertension, which is high blood pressure resulting from an identifiable underlying secondary cause. This type of hypertension accounts for about 5-15% of all cases and is characterized by more specific diagnostic and treatment approaches compared to primary hypertension. Let’s delve into the details of the two common causes mentioned: renal parenchymal disease and renovascular disease.
1. Renal Parenchymal Disease
Overview: This is the most common cause of secondary hypertension. It involves any condition that impairs the kidneys' ability to function properly, leading to decreased glomerular filtration rate (GFR).
Causes:
Urinary Tract Infections (UTI) and Analgesic Abuse: Both can lead to chronic kidney damage.
Glomerulonephritis: An inflammation of the glomeruli, which are tiny structures within the kidneys that filter blood.
Hereditary Polycystic Kidney Disease: A genetic disorder characterized by the growth of numerous cysts in the kidneys.
Lupus Nephritis: An autoimmune disease that causes inflammation of the kidneys.
Renal Tumors: Can also impair kidney function and affect blood pressure regulation.
Symptoms and Diagnosis:
Patients might show rising creatinine levels, indicating kidney dysfunction.
There is typically an inability to concentrate urine, which can become more apparent as kidney damage progresses.
Ultrasound: May reveal kidneys that appear small and shrunken, except in cases like polycystic kidney disease where kidneys are enlarged.
Hormonal Changes: Often, there is low aldosterone and renin activity unless the kidney damage has led to a compensatory overactivation of these systems.
2. Renovascular Disease
Overview: This condition involves the narrowing (stenosis) of one or both renal arteries, which can be caused by atherosclerosis or fibromuscular dysplasia.
Causes:
Atherosclerosis: The most common cause, where plaque builds up in the arteries.
Fibromuscular Dysplasia: More common in young women, this is a condition characterized by abnormal growth within the arterial wall, affecting blood flow.
Mechanism: The stenosis causes reduced blood flow to the kidneys, which might mistakenly sense this as low overall blood pressure. In response, the kidneys activate the renin-angiotensin-aldosterone system (RAAS), increasing blood pressure throughout the body.
Symptoms and Diagnosis:
Normal urine concentration, but possibly increased creatinine levels.
Elevated levels of aldosterone and renin due to RAAS activation.
Ultrasound and CT Angiography: Useful for assessing blood flow to the kidneys and confirming renal artery stenosis.
3. Endocrine Disorders
Primary Hyperaldosteronism (Conn's Syndrome):
Characteristics: Overproduction of aldosterone, leading to sodium retention, potassium loss, and metabolic alkalosis.
Diagnostic Marker: Increased aldosterone/renin ratio, with decreased renin activity due to negative feedback.
Cushing's Syndrome (Hypercortisolism):
Symptoms: Central obesity, thin limbs, moon face, and possibly a buffalo hump.
Cause: Excess cortisol, which increases glucose and has mineralocorticoid effects that increase sodium and water retention, raising blood pressure.
Hyperthyroidism:
Effects: Increased metabolism and enhanced sensitivity to sympathetic stimulation due to excess thyroid hormones (T4), leading to increased heart rate and blood pressure.
Laboratory Findings: Elevated T4 levels and suppressed TSH.
Pheochromocytoma:
Presentation: Episodic or sustained hypertension due to catecholamine-secreting tumors typically found in the adrenal medulla.
Diagnosis: High levels of urinary metanephrines, which are catecholamine metabolites.
Primary Hyperparathyroidism:
Mechanism: Excess parathyroid hormone (PTH) leads to increased calcium levels; hypercalcemia can increase vascular resistance.
Lab Values: High calcium, high PTH, and low phosphate levels.
Acromegaly:
Cause: Overproduction of growth hormone usually due to a pituitary adenoma.
Effect: Increased growth hormone and IGF-1 levels cause fluid retention and increase cardiac output, contributing to hypertension.
Congenital Adrenal Hyperplasia:
Specific Forms: Deficiencies in 17alpha- and 11beta-hydroxylase can lead to overproduction of mineralocorticoids, which mimic aldosterone effects.
Result: Sodium retention and potassium loss, which elevate blood pressure.
4. Structural Abnormalities
Coarctation of the Aorta:
Description: Narrowing of the aorta, typically distal to the left subclavian artery branch.
Symptoms: Higher blood pressure in the arms than in the legs, and delayed or weaker femoral pulses compared to radial pulses.
5. Lifestyle Factors and Conditions
Obstructive Sleep Apnea (OSA):
Mechanism: Intermittent hypoxia and hypercapnia from repeated airway closures increase sympathetic activity and blood pressure.
Drug-Induced Hypertension:
Includes substances like sympathomimetics, corticosteroids, NSAIDs, oral contraceptives, amphetamines, and cocaine, all of which can raise blood pressure through various mechanisms.
Pregnancy:
Mechanism: Increased estrogen stimulates the renin-angiotensin system, enhancing water retention and expanding blood volume.
Chronic Stress:
Effect: Persistent elevation of catecholamines (adrenaline and noradrenaline) increases heart rate and vascular resistance.
Other Types of Hypertension
White Coat Hypertension
Description: This condition occurs when patients exhibit high blood pressure readings in a clinical setting but have normal readings elsewhere.
Prevalence: About 13% of people may experience this form of hypertension.
Monitoring: Ambulatory blood pressure monitoring over 24 hours can help confirm true blood pressure levels, as this method provides readings in a variety of settings and times, reducing the influence of anxiety associated with doctor's visits.
Masked Hypertension
Description: Opposite of white coat hypertension, where patients show normal blood pressure readings in a clinical setting but have high readings in their daily life.
Prevalence: Also affects an estimated 13% of individuals.
Risks: Often goes undetected without the use of ambulatory or home blood pressure monitoring, potentially leading to untreated hypertension and its complications.
Isolated Systolic Hypertension
Characteristics: Characterized by elevated systolic pressure (>140 mmHg) while diastolic pressure remains normal (<90 mmHg).
Causes: Common in the elderly due to decreased arterial elasticity or in conditions that increase cardiac output, such as anaemia, hyperthyroidism, chronic aortic regurgitation, and arteriovenous fistulas.
Symptoms: Often asymptomatic, though it may present with signs of increased pulse pressure, such as visible pulsation of the head (De Musset's sign).
Clinical Features and Symptoms of Hypertension
Hypertension is typically asymptomatic in its early stages, which is why it is so dangerous and often goes undetected until serious health issues arise. However, some individuals may experience symptoms that could indicate high blood pressure or its complications:
Headaches: Often occur in the morning, can be intense and located at the back of the head.
Dizziness and Tinnitus: Dizziness and ringing in the ears are nonspecific but common in those with high blood pressure.
Visual Changes: Blurred vision may occur as hypertension can affect the blood vessels in the eyes.
Epistaxis: Nosebleeds, though not exclusively caused by hypertension, can sometimes be a sign of chronically high blood pressure.
Cardiac Symptoms: Chest discomfort, palpitations, and a strong bounding pulse are often signs of significant hypertension.
Nervous System Symptoms: Nervousness, fatigue, and sleep disturbances like insomnia can be associated with high blood pressure, particularly when it spikes during the night.
Diagnostics
Medical History
Risk Factors and Family History: A detailed account of personal and family medical history helps identify genetic predispositions and lifestyle factors contributing to hypertension. This includes discussing cases of hypertension or cardiovascular diseases among immediate family members.
Blood Pressure History: Information on the duration, onset, and previous levels of blood pressure, as well as any previous diagnoses or treatments for hypertension.
Symptoms of Organ Damage: Identifying symptoms that may indicate end-organ damage such as renal dysfunction, retinal changes, cardiovascular events (e.g., chest pain, palpitations), or neurological symptoms (e.g., headaches, visual disturbances) is crucial.
Assessment for Secondary Hypertension: Certain features suggest secondary hypertension, such as hypertension onset before age 30 or after 55, very high diastolic pressure, resistant hypertension (not controlled despite three different classes of antihypertensive medications, including a diuretic), and signs of disproportionate end-organ damage or recurrent hypertensive crises.
Blood Pressure Measurement Techniques
Office Blood Pressure Measurement:
Procedure: The patient should be seated comfortably, with their back supported, legs uncrossed, and arm supported at heart level. It’s important that the patient rests quietly in this position for 3-5 minutes before the measurement.
Diagnosis: Hypertension is typically diagnosed based on the average of multiple blood pressure readings taken on at least two separate occasions.
Ambulatory Blood Pressure Monitoring (ABPM):
Procedure: A portable device is worn by the patient, which automatically measures blood pressure at regular intervals throughout the day and night. This method provides a more comprehensive picture of the blood pressure changes over a 24-hour period and avoids the white-coat effect (elevation of blood pressure in a medical setting).
Criteria for Hypertension: An average daytime blood pressure greater than 130/80 mmHg or a 24-hour average greater than 130/80 mmHg is generally considered hypertensive. Notably, blood pressure normally dips during sleep, so nocturnal readings are typically lower.
Laboratory Tests
Complete Blood Count (CBC) and Hemoglobin:
Purpose: Helps in evaluating the overall health status, detecting anemia, and other hematological abnormalities which can influence or be influenced by hypertension.
Fasting Plasma Glucose:
Purpose: Essential for detecting diabetes mellitus, which is a common comorbidity with hypertension and significantly affects its management and prognosis.
Lipid Profile:
Components: Includes measuring High-Density Lipoprotein (HDL), Low-Density Lipoprotein (LDL), and triglycerides.
Purpose: Assesses cardiovascular risk as dyslipidemia is closely linked with atherosclerotic disease, which can be both a cause and a complication of hypertension.
Electrolytes (Na, K, Ca):
Purpose: Imbalances can be indicative of underlying disorders affecting blood pressure, such as hyperaldosteronism or renal insufficiency.
Serum Urea, Creatinine, Uric Acid:
Purpose: Provides insight into kidney function, which is crucial since hypertension can be both a cause and a consequence of renal damage.
Urinalysis:
Tests: Looks for proteinuria and hematuria, which indicate kidney damage. Metanephrines are measured to rule out pheochromocytoma, a rare cause of secondary hypertension.
Hormone Levels:
Purpose: Specific hormones are tested if secondary hypertension is suspected, such as aldosterone, renin, cortisol, and thyroid hormones, to diagnose conditions like Conn's syndrome, Cushing's syndrome, or thyroid dysfunction.
Other Tests
Electrocardiogram (ECG):
Purpose: Screens for heart conditions linked to hypertension, such as left ventricular hypertrophy, arrhythmias, or ischemic heart disease.
Echocardiography:
Purpose: Assesses cardiac structure and function, looking for signs of heart failure, valve diseases, or cardiac hypertrophy.
Exercise Testing:
Purpose: Evaluates the cardiovascular response to physical stress, which can help in diagnosing coronary artery disease or other cardiac limitations.
Holter Monitoring:
Purpose: Continuous recording of the heart's electrical activity over 24 to 48 hours to detect intermittent arrhythmias or ischemic episodes.
Carotid and Peripheral Artery Ultrasound:
Tests: Includes assessment of the carotid arteries via ultrasound to look for atherosclerotic changes; the Ankle-Brachial Index (ABI) measures and compares blood pressures in the ankle and arm to assess peripheral arterial disease.
Retinal Examination:
Purpose: Performed by an ophthalmologist to look for signs of damage from hypertension in the blood vessels of the eyes, which can mirror vascular changes in the brain and elsewhere in the body.
TREATMENT
1. Lifestyle Changes
Lifestyle modifications are recommended for all patients with blood pressure over 120/80 mmHg and are particularly emphasized for those with higher readings. These changes can significantly lower blood pressure, reduce the need for medications, or enhance the effectiveness of blood pressure medication.
Weight Loss: Even a modest reduction in weight can lead to significant improvements in blood pressure.
Diet: Adopting a heart-healthy diet such as the DASH (Dietary Approaches to Stop Hypertension) diet that includes fruits, vegetables, fiber-rich foods, and reduced saturated and total fats.
Sodium Reduction: Limiting sodium intake to less than 5-6 grams per day can help control blood pressure.
Alcohol Moderation: Limiting alcohol intake to no more than two drinks per day for men and one drink per day for women.
Smoking Cessation: Quitting smoking not only reduces blood pressure but also decreases the overall cardiovascular risk.
Regular Exercise: Engaging in at least 30 minutes of moderate-intensity exercise, such as brisk walking, daily.
2. First-Line Pharmacotherapy
If lifestyle modifications are insufficient to achieve blood pressure goals, medication may be necessary. The choice of drugs depends on the individual's overall health, presence of other medical conditions, and specific characteristics of the hypertension.
ACE Inhibitors (e.g., enalapril, captopril, perindopril):
Benefits: Cardioprotective and nephroprotective effects by decreasing fibrosis and mesangial proliferation.
Side Effects: Dry cough, angioedema, hyperkalemia, and potential teratogenic effects during pregnancy.
Angiotensin Receptor Blockers (ARBs) (e.g., losartan, valsartan, telmisartan, candesartan):
Benefits: Similar cardioprotective and nephroprotective effects as ACE inhibitors.
Side Effects: Hyperkalemia and teratogenic effects.
Note: Should not be used in combination with ACE inhibitors.
Thiazide Diuretics (e.g., hydrochlorothiazide, indapamide):
Usage: Often used in combination with ACE inhibitors or ARBs.
Side Effects: Hypokalemia, hyponatremia.
Calcium Channel Blockers (e.g., nifedipine, amlodipine):
Benefits: Effective in reducing arterial pressure.
Side Effects: Headaches, constipation, gastrointestinal disturbances.
Beta-Blockers (e.g., metoprolol, labetalol, bisoprolol, nebivolol, carvedilol):
Indications: Particularly beneficial for patients with ischemic heart disease and heart failure.
Benefits: Nebivolol also offers vasodilatory effects, and carvedilol acts as a mixed alpha- and beta-blocker.
Side Effects: Fatigue, cold extremities, sleep disturbances, and bradycardia.
Second-Line Pharmacotherapy for Hypertension
Loop Diuretics (e.g., furosemide, torsemide):
Use: Particularly effective in managing fluid overload in patients with heart failure and chronic kidney disease.
Mechanism: Work by inhibiting sodium and chloride reabsorption in the kidneys, increasing urine output.
Aldosterone Antagonists (e.g., spironolactone, eplerenone):
Use: Beneficial in conditions like hyperaldosteronism and as an adjunct in heart failure.
Side Effects: Can cause hyperkalemia and, particularly with spironolactone, gynecomastia due to its anti-androgen effects.
Renin Inhibitors (e.g., aliskiren):
Use: Directly inhibits renin, which is involved in the angiotensin-renin-aldosterone system, thereby reducing blood pressure.
Note: Should not be used in combination with ACE inhibitors or ARBs due to an increased risk of adverse effects like hyperkalemia and renal impairment.
Alpha-1 Blockers (e.g., doxazosin):
Use: Can be used in treating hypertension associated with pheochromocytoma and is also commonly prescribed for benign prostatic hyperplasia to improve urinary flow.
Arteriolar Vasodilators (e.g., hydralazine):
Use: Often used in pregnancy-induced hypertension due to its safety profile.
Mechanism: Directly dilates arterioles, reducing systemic vascular resistance and blood pressure.
Pregnancy-Specific Hypertension Treatments:
Methyldopa: A central-acting alpha-2 agonist considered safe during pregnancy.
Labetalol: A beta-blocker safe for use from the second trimester onwards.
Hydralazine and Nifedipine: Both are safe and effective for managing hypertension in pregnant women.
Complications of Hypertension
Hypertension can lead to serious complications across multiple organ systems:
Cardiovascular System:
Accelerated atherosclerosis, leading to coronary artery disease.
Congestive heart failure and hypertrophic cardiomyopathy.
Increased risk of atrial fibrillation, which can complicate into stroke.
Aortic dissection and peripheral artery disease.
Brain:
Increased risk of stroke and transient ischemic attacks.
Potential for cognitive decline and changes due to chronic reduced cerebral perfusion.
Kidneys:
Hypertensive nephrosclerosis, leading to a decrease in kidney function and potentially progressing to end-stage renal disease.
Eyes:
Hypertensive retinopathy, which includes arteriosclerotic changes, microaneurysms, and papilledema.
HYPERTENSIVE CRISES
Hypertensive crises are severe and potentially life-threatening elevations in blood pressure that require immediate medical attention. These crises are categorized into two types, hypertensive urgencies and hypertensive emergencies, based on the presence or absence of acute end-organ damage. Here’s an in-depth look at both categories, including their causes, symptoms, and treatment strategies:
Hypertensive Urgency
Definition: A hypertensive urgency occurs when blood pressure exceeds 180/120 mmHg without causing direct, immediate damage to the body’s organs.
Symptoms: Patients may experience nonspecific symptoms such as headaches, dizziness, or epistaxis (nosebleeds), but there are no signs of acute organ damage.
Common Causes: Often results from non-adherence to prescribed antihypertensive medication, which might be due to forgetfulness, financial constraints, or misunderstanding the medication regimen.
Management:
Outpatient Treatment: Involves the cautious lowering of blood pressure with oral antihypertensive medications such as captopril (an ACE inhibitor) or labetalol (a beta-blocker).
Monitoring: Close monitoring is necessary to ensure that blood pressure is gradually reduced to safer levels without precipitating adverse events.
Medication Adjustment: Reinstating or adjusting the existing antihypertensive regimen is crucial to prevent recurrence.
Hypertensive Emergency
Definition: This is a more severe form of hypertensive crisis where blood pressure rises above 180/120 mmHg and is associated with signs of impending or progressive end-organ damage.
Symptoms: Can include severe chest pain, breathlessness, back pain, numbness/weakness, vision changes, difficulty speaking, or confusion, indicating potential heart failure, myocardial infarction, stroke, renal failure, or acute retinopathy.
Management:
Immediate Care: Requires prompt medical intervention, typically in an intensive care unit (ICU).
IV Antihypertensives: Medications such as nicardipine (a calcium channel blocker), labetalol, or sodium nitroprusside are administered to rapidly control blood pressure.
Controlled Reduction: The goal is to reduce blood pressure by no more than 25% within the first hour. Rapid reduction beyond this can lead to decreased coronary, cerebral, or renal perfusion and potentially precipitate ischemic complications.
Gradual Normalization: After the initial stabilization, blood pressure should be slowly lowered to a normal level over the next 24-48 hours under close supervision to avoid rebound hypertension or other complications.
Critical Points in Management
Monitoring: Continuous monitoring of blood pressure and organ function is critical during the management of hypertensive crises.
Risk Reduction: Long-term, ensuring strict adherence to antihypertensive therapy and regular follow-ups are essential to prevent future hypertensive crises.
Patient Education: Educating patients about the importance of adherence to treatment, lifestyle modifications, and the potential complications of uncontrolled hypertension is vital.