Hypertension and the Kidney Lecture

Hypertension and the Kidney

Introduction

  • Presenter: Dr. Himabindu Yerneni MD

  • Affiliation: Case Western Reserve University School of Medicine

  • Date: January 15, 2026

Supplemental Reading

  • Recommended Reading: Journal of the American College of Cardiology, Volume 71, Issue 19, May 2018, DOI: 10.1016/j.jacc.2017.11.006

  • Title: 2017 ACC/AHA/AAPA/ABC/ACPM/AGS/APhA/ASH/ASPC/NMA/PCNA Guideline for the Prevention, Detection, Evaluation, and Management of High Blood Pressure in Adults

Learning Objectives

  1. Discuss the hemodynamic determinants of systemic hypertension, focusing on kidney regulation of blood pressure.

  2. Distinguish between primary and secondary hypertension.

  3. Recognize common risk factors for essential hypertension.

  4. Describe the increased risk of kidney, heart, and peripheral vascular disease associated with hypertension.

  5. Identify the three main classes of diuretics (loop, thiazide, K⁺ sparing) and their kidney action sites.

  6. Explain how diuretics, ACE inhibitors, and beta-blockers lower blood pressure.

  7. Describe the major treatments for hypertension.

Checklist for Accurate Measurement of Blood Pressure (BP)

  • Step 1: Properly prepare the patient.

  • Step 2: Use proper technique for BP measurements.

  • Step 3: Take necessary measurements for diagnosis and treatment.

  • Step 4: Document accurate BP readings.

  • Step 5: Average the readings.

  • Step 6: Provide BP readings to the patient.

Selection Criteria for BP Cuff Size for Measurement in Adults

  • 22–26 cm: Small adult

  • 27–34 cm: Adult

  • 35–44 cm: Large adult

  • 45–52 cm: Adult thigh

Out-of-Office and Self-Monitoring of Blood Pressure

  • Recommendation: Out-of-office BP measurements are advised to confirm hypertension diagnosis and guide medication adjustment, complemented by telehealth counseling or clinical interventions.

Categories of Blood Pressure in Adults

  • BP classification based on an average of ≥2 careful readings obtained on ≥2 occasions:

    • Normal: SBP < 120 mm Hg and DBP < 80 mm Hg

    • Elevated: SBP 120–129 mm Hg and DBP < 80 mm Hg

    • Hypertension Stage 1: SBP 130–139 mm Hg or DBP 80–89 mm Hg

    • Hypertension Stage 2: SBP ≥ 140 mm Hg or DBP ≥ 90 mm Hg

Prevalence of Hypertension

  • Global Statistics: Approximately 1 billion people globally exhibit hypertension.

  • U.S. Statistics: 60 million Americans have hypertension, with rising prevalence.

  • Framingham Heart Study Data: Indicates that 90% of individuals over age 55 will develop hypertension in their lifetime.

Age and Gender Prevalence

  • Overall prevalence of HTN:

    • Crude: 46%

    • Men: 48% | Women: 43%

    • Age Specific:

    • 20–44 years: Men 30%, Women 19%

    • 45–54 years: Men 50%, Women 44%

    • 55–64 years: Men 70%, Women 63%

    • 65–74 years: Men 77%, Women 75%

    • 75+ years: Men 79%, Women 85%

Race and Ethnicity Prevalence

  • Non-Hispanic White: Men 47%, Women 41%

  • Non-Hispanic Black: Men 59%, Women 56%

  • Non-Hispanic Asian: Men 45%, Women 36%

  • Hispanic: Men 44%, Women 42%

Health Implications of Hypertension

  • HTN is a major public health risk factor for:

    • Coronary artery disease

    • Stroke

    • Heart failure

    • Renal disease

    • Peripheral vascular disease

  • Awareness Gap: Over 2/3 of hypertensive individuals are unaware or inadequately treated.

  • Asymptomatic Nature: Elevated BP often remains asymptomatic until a cardiovascular event occurs, underscoring the need for screening.

Risk Factors for Essential Hypertension

Non-modifiable Risk Factors

  • Family History: Increased risk if close relatives have high blood pressure.

  • Age: Risk increases with age due to reduced elasticity of blood vessels.

  • Gender: Men have a higher risk until age 65, when women surpass.

  • Race: African-Americans have a higher incidence and severity.

Modifiable Risk Factors

  • Physical Activity: Lack of can elevate risk.

  • Unhealthy Diet: High in sodium can contribute to hypertension; balanced nutrition is essential.

  • Overweight/Obese: Extra weight strains the circulatory system.

  • Alcohol: Excessive intake leads to spikes in BP and related health issues.

  • Sleep Apnea: Linked with incidence of hypertension.

  • High Cholesterol and Diabetes: Commonly co-occur with hypertension.

  • Tobacco Use: Increases BP temporarily and damages arteries.

  • Stress: Can elevate BP and lead to unhealthy coping behaviors.

Hemodynamic Determinants of Systemic Hypertension

Key Equations

  • Mean Arterial Pressure (MAP): MAP = CO imes SVR

    • Where CO = Cardiac Output

    • SVR = Systemic Vascular Resistance

  • Blood Pressure and Cardiac Output Relation: BP = CO imes TPR

    • Where CO = SV imes HR

    • SV = Stroke Volume

    • HR = Heart Rate

Role of Kidneys in BP Regulation

  • Juxtaglomerular apparatus: Produces renin in response to low blood volume or sodium levels, initiating a cascade:

    • Renin → Angiotensin I → (Angiotensin II → Vasoconstriction, Aldosterone secretion)

  • Function of Angiotensin II: Promotes sodium and water retention to restore BP and volume.

Classes of Diuretics

  1. Loop Diuretics: Acts on the ascending loop of Henle, affecting 20-25% of sodium reabsorption.

  2. Thiazide Diuretics: Sites of action include the distal convoluted tubule (DCT), affecting approximately 5% sodium reabsorption.

  3. Potassium-Sparing Diuretics: Inhibit sodium reabsorption in the collecting duct while preserving potassium.

Primary vs. Secondary Hypertension

Primary Hypertension

  • Definition: Accounts for 90-95% of cases; no identifiable cause; pathogenesis is poorly understood.

Secondary Hypertension

  • Definition: Many identifiable causes, including:

    • Renal parenchymal disease

    • Renovascular disease

    • Primary aldosteronism

    • Obstructive sleep apnea

    • Drug/alcohol induced

  • Uncommon causes include: Pheochromocytoma, Cushing’s syndrome, aortic coarctation, among others.

Health Consequences of Hypertension

  • Cardiovascular Effects: Left ventricular hypertrophy, atherosclerosis, heart failure.

  • Neurological Effects: Stroke or transient ischemic attack (TIA).

  • Renal Effects: Chronic kidney disease.

  • Ocular Effects: Retinopathy.

  • Peripheral Effects: Peripheral arterial disease.

  • Cognitive Effects: Impairment in cognition and memory.

Increased Cardiovascular Risk

  • There is a direct statistical relationship between the increasing systolic blood pressure and cardiovascular mortality risk:

    • Example Data: Higher systolic BP correlates with an increased percentage of participants exhibiting cardiovascular death.

Treatment and Management of Hypertension

Initial Evaluation

  • Importance of thorough history and physical exams to uncover possible secondary hypertension causes, alongside assessments of lifestyle.

Basic and Optional Laboratory Tests for Primary Hypertension

  • Basic Tests Include:

    • Fasting blood glucose

    • Complete blood count

    • Lipid profile

    • Serum creatinine with eGFR

    • Thyroid-stimulating hormone

  • Optional Tests Include: Echocardiogram, uric acid, urinary albumin-to-creatinine ratio.

Pharmacological Treatment Recommendations

Treatment Thresholds and Follow-Up

  • Normal BP (<120/80 mm Hg): Promote lifestyle habits.

  • Elevated BP (120-129/<80 mm Hg): Reinforce lifestyle changes; reassess in 1 year.

  • Stage 1 Hypertension (130-139/80-89 mm Hg): Nonpharmacologic therapy alone or with medication; reassess in 3-6 months.

  • Stage 2 Hypertension (≥140/90 mm Hg): Nonpharmacologic therapy plus BP-lowering medications.

Nonpharmacological Interventions and Impact on SBP

  • Weight Loss: Reduce body weight for an expected 1 mm Hg drop in BP for each 1 kg lost (approx. -5 mm Hg effect).

  • Healthy Diet (DASH diet): Significant reduction (-11 mm Hg).

  • Sodium Reduction: Aim for a daily intake of <1500 mg; reduces SBP by approximately -5/6 mm Hg.

  • Regular Physical Activity: Involves aerobic exercise leading to a drop in BP.

Pharmacological Classes of Hypertension Medication

  • Diuretics (Thiazide, Loop)

  • Beta-blockers

  • Alpha-blockers

  • Calcium channel blockers (Dihydropyridine, Non-dihydropyridine)

  • ACE inhibitors

  • Renin inhibitors

  • Angiotensin receptor blockers (ARBs)

  • Centrally acting agents

  • Aldosterone antagonists

  • Vasodilators

Specific Recommendations for Initial Treatment

  • Initiate therapy using first-line agents such as thiazides, CCBs, and ACE inhibitors/ARBs as appropriate depending on patient profile.

Racial and Age Considerations in Treatment

  • Race Considerations: For African American adults, initial treatment should include thiazide-type diuretics or CCBs.

  • Pregnancy Guidelines: Transition hypertensive women to safer medications during pregnancy; avoid ACE inhibitors, ARBs, and renin inhibitors.

  • Older Adults: Treatment target should maintain SBP <130 mm Hg for noninstitutionalized older adults.

Conclusion

  • The discussion should encompass hemodynamic determinants, differentiation of hypertension types, risk factors, potential health risks associated with hypertension, and the comprehensive treatment approaches to managing hypertension effectively.

  • The focus on early detection and appropriate interventions is crucial in reducing long-term health repercussions associated with hypertension.