Hypertension in Kidney Disease

Pathophysiology in CKD HTN - Pressure Cooker Kidneys

Kidneys in CKD struggle to manage fluid and blood pressure, acting like overloaded pressure cookers.

• Core Mechanisms:
  • Volume Expansion: ↓ GFR → Impaired $Na^{+}$ & $H_{2}O$ excretion → ↑ Extracellular fluid → ↑ Cardiac output.
  • RAAS Upregulation: Renal hypoperfusion/ischemia → ↑ Renin → ↑ $Ang ext{ II}$ (vasoconstrictor) & Aldosterone ($Na^{+}$ retention).
  • Sympathetic Nervous System (SNS) Overdrive: Afferent signals from diseased kidneys stimulate central SNS.
  • Endothelial Dysfunction: ↓ Nitric Oxide ($NO$), ↑ Endothelin-1 → Impaired vasodilation & pro-inflammatory state.
• Consequences: Systemic vasoconstriction, increased vascular resistance, and arterial stiffness.

⭐ Nocturnal hypertension (loss of normal nighttime BP dip) is a hallmark in CKD, strongly predicting cardiovascular events and faster kidney disease progression.

Diagnosis of CKD HTN - Sizing Up Pressure

• BP Measurement Methods:
  • Standardized Office BP (SOBP): Baseline, multiple readings.
  • Ambulatory BP Monitoring (ABPM): Gold standard; detects white-coat/masked HTN, nocturnal patterns (non-dipping).
  • Home BP Monitoring (HBPM): Valid alternative for diagnosis & ongoing monitoring.
• Diagnostic Criteria (HTN in CKD):
  • SOBP: ≥130/80 mmHg.
  • ABPM (24h avg): ≥130/80 mmHg.
  • HBPM (avg over ≥1 week): ≥130/80 mmHg.
• KDIGO 2021 Target: Aim for SBP <120 mmHg (using standardized office BP), if tolerated.

⭐ ABPM is superior in CKD for diagnosis and prognosis, especially by identifying non-dipping patterns (absent nocturnal BP fall of 10-20%), which are linked to significantly increased cardiovascular risk and faster CKD progression.

Management of CKD HTN - Deflating Pressure

BP Target: <130/80 mmHg. Consider <120 mmHg SBP if tolerated (high-risk).

1. Lifestyle Modifications (LSM):

• Salt: <2 g/day Na (or <5 g/day NaCl)
• Weight: Target BMI <25 kg/m²
• DASH diet (monitor K+)
• Exercise: ≥150 min/week
• Limit alcohol

2. Pharmacotherapy:

• First-line: ACE inhibitors (ACEi) or ARBs
  • Preferred if albuminuria >30 mg/day (ACR >3 mg/mmol)
  • Monitor SCr (↑ up to 30% acceptable) & K+.
  • ⚠️ Avoid: Bilateral renal artery stenosis, angioedema.
• Add-on therapy:
  • Diuretics: Thiazides (eGFR ≥30 mL/min/1.73m²), Loops (eGFR <30 mL/min/1.73m² / overload).
  • CCBs (Dihydropyridines e.g., Amlodipine).
  • MRAs (e.g., Finerenone, Spironolactone) if eGFR/K+ allow, esp. with albuminuria.
  • Beta-blockers (if compelling indication e.g., CAD, HFrEF).

⭐ ACEi/ARBs are vital in proteinuric CKD for renoprotection via ↓ intraglomerular pressure & proteinuria, beyond BP reduction.

Special CKD HTN Cases - Tricky Pressure Points

• Resistant HTN: BP >140/90 mmHg on ≥3 drugs (incl. diuretic). Rule out pseudo-resistance. Maximize diuretics, add MRA (spironolactone/eplerenone), then others.
• ADPKD: Early HTN. ACEi/ARB first-line. Target BP <130/80 mmHg; consider <110/75 mmHg if young (HALT-PKD trial).
• Glomerulonephritis (GN): Volume & RAAS driven. ACEi/ARB for BP & proteinuria. Loop diuretics for volume control.
• Post-Transplant HTN: Multifactorial (CNIs, steroids). CCBs (e.g., amlodipine) often initial choice. ACEi/ARB cautiously (monitor K+, GFR).

⭐ In ADPKD, rigorous BP control with ACEi/ARB can slow cyst growth and GFR decline, a key finding from the HALT-PKD trial supporting aggressive targets in select patients (e.g., younger, preserved GFR).

High‑Yield Points - ⚡ Biggest Takeaways

• Chronic Kidney Disease (CKD) is the most common cause of secondary hypertension.
• Target Blood Pressure (BP) in most CKD patients is <130/80 mmHg.
• ACE inhibitors (ACEi) or Angiotensin II Receptor Blockers (ARBs) are first-line agents, especially with proteinuria.
• Monitor for hyperkalemia and an initial ↑ in serum creatinine with ACEi/ARBs.
• Renal artery stenosis is a significant cause of renovascular hypertension; screen if suspected.
• Sodium and water retention (volume overload) is a major pathogenic factor in CKD-associated hypertension.
• Lifestyle modifications, including strict salt restriction, are fundamental in management.