M9 Hypertension___Antihypertensives *

  1. Hypertension & Antihypertensives

1.1 Blood Pressure BasicsBlood Pressure (BP) is a critical physiological parameter calculated as:BP = Cardiac Output (CO) x Systemic Vascular Resistance (SVR).Understanding blood pressure involves recognizing various categories:

  • Hypotension: A decrease in blood pressure defined as readings below 90/60 mmHg.

  • Hypertension: Defined as blood pressure consistently above 139/89 mmHg, categorized into stages for clinical management:

    • Stage 1 Hypertension: 130-139 systolic or 80-89 diastolic

    • Stage 2 Hypertension: 140 or higher systolic or 90 or higher diastolicSymptoms of Hypertension: While some individuals may remain asymptomatic, hypertension can present through various warning signs, including:

  • Persistent headaches

  • Tinnitus (ringing in the ears)

  • Episodes of vertigo (dizziness)

  • Syncope (fainting)

QUIZ

  1. What is the formula to calculate blood pressure? sv x systemic resistance

  2. What defines stage 1 hypertension?

  3. Name one symptom of hypertension.

  4. What is classified as hypotension?

1.2 Blood Pressure Regulation and HomeostasisBaroreceptors, primarily located in the carotid sinuses and aortic arch, are integral for blood pressure regulation. They send impulses to the CNS, primarily affecting the:

  • Cardioinhibitory Center: Activates to lower heart rate during high pressures.

  • Cardioacceleratory Center: Inhibited when blood pressure is elevated to reduce HR.

  • Vasomotor Center: Additional regulation occurs here, coordinating vessel constriction and dilation.When pressure exceeds normal thresholds, vasodilation occurs, facilitated by released nitric oxide and reduced sympathetic activity, leading to decreased systemic vascular resistance. Conversely, a drop in BP triggers sympathetic impulses, enhancing vasoconstriction and readying the body for potential threats.

1.3 Types of Hypertension

  • Primary Hypertension (Essential): The predominant form of hypertension where the exact cause remains elusive; a complex interplay of genetic, environmental, and lifestyle factors, significantly contributing to its development. Risk factors include age (more common in older adults), sex (more prevalent in men), and race (notably higher incidence in African Americans).

  • Secondary Hypertension: A result of identifiable medical conditions such as chronic kidney disease, hormonal disorders, or cardiovascular abnormalities. Management involves treating the underlying cause, often resulting in normalized blood pressure levels.

1.4 Risk Factors for Hypertension

  • Uncontrollable Risk Factors:

    • Genetics: Family history of hypertension increases risk.

    • Age: Risk increases as individuals age due to vascular stiffening.

    • Sex: Men typically develop hypertension earlier than women.

    • Race: Certain ethnic groups are more predisposed.

  • Controllable Risk Factors:

    • Obesity: Excess body weight elevates blood pressure.

    • Sedentary Lifestyle: Physical inactivity contributes to weight gain and vascular health issues.

    • Alcohol Consumption: High intake can lead to elevated BP.

    • Diet (sodium intake): High salt consumption is directly linked to increased blood pressure.

    • Stress: Chronic stress can influence dietary choices and lifestyles that elevate BP.

  1. The Renin-Angiotensin-Aldosterone System (RAAS)

2.1 RAAS MechanismRenin Release: The kidneys respond to reduced blood flow or pressure by releasing renin from the juxtaglomerular apparatus, which is crucial for fluid balance.Renin converts angiotensinogen (produced by the liver) to angiotensin I.ACE Function: The Angiotensin-Converting Enzyme (ACE), primarily located in the lungs, transforms angiotensin I into angiotensin II, a potent vasoconstrictor.Action of Angiotensin II: Functions to elevate blood pressure through:

  • Vasoconstriction: Increases peripheral resistance and BP.

  • Stimulation of Aldosterone Secretion: Initiates sodium and water reabsorption in the kidneys, further increasing blood volume and pressure.

2.2 Effects of AldosteroneAldosterone plays a pivotal role in regulating blood pressure by increasing blood volume through sodium and water retention, thus raising systemic blood pressure levels. It is a target for antihypertensive therapy due to its significant impact on fluid balance and hypertension management.

  1. Treatment of Hypertension

3.1 Classifications of Antihypertensive Drugs

  • ACE Inhibitors:Mechanism: Prevent the conversion of angiotensin I to II, facilitating vasodilation and lowering BP.Indications: Heart Failure (HF), Hypertension (HTN), Myocardial Infarction (MI).Side Effects: Include cough, hypotension, hyponatremia, and risk of angioedema (more common in African American patients).Contraindications: Include bilateral renal artery stenosis, pregnancy, and known allergies to medications.

  • Angiotensin II Receptor Blockers (ARBs):Act as antagonists at angiotensin II receptor, promoting vasodilation and reduced blood pressure.Indications: Commonly prescribed for hypertension, Chronic Kidney Disease (CKD), and Heart Failure.Side Effects: Generally well-tolerated; however, hyperkalemia and hypotension can occur.

  • Diuretics:Initially used in fluid retention instances, they are now first-line therapy for hypertension due to their ability to decrease blood volume.Golden Rule: Water follows sodium, meaning that sodium management leads to fluid balance.

3.2 Types of Diuretics

  • Loop Diuretics:Act at the ascending loop of Henle preventing Na+, K+, and Cl- reabsorption.Examples: Furosemide (Lasix), Bumetanide, Torsemide.Indications: Indicated in severe heart failure and acute pulmonary edema scenarios.Side Effects: Risks of ototoxicity and electrolyte imbalance.

  • Thiazide Diuretics:Function by acting on the distal convoluted tubule, inhibiting Na+ and Cl- reabsorption.Example: Hydrochlorothiazide (HCTZ), frequently used as a first-line agent for hypertension.Side Effects: Include hypotension and electrolyte imbalance.

  • Potassium Sparing Agents:Targeting the collecting ducts, these agents promote potassium retention while facilitating sodium excretion.Medications: Amiloride, Spironolactone.Side Effects: Potential for hyperkalemia, particularly in patients with renal impairment.

  1. Goals of Hypertension ManagementThe primary aim is to maximize protection against cardiovascular complications while minimizing discomfort to the patient.Effective strategies encompass:

  • Non-drug therapies: Such as sodium reduction in diets, implementing weight management programs, personalized dietary plans, and exercise regimens.

  • Medical therapy: Encompasses the strategic use of antihypertensive medications while ensuring patient compliance for long-term management of hypertension, with periodic monitoring and adjustments as necessary.

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