›Renal excretion accounts for 90-95% of daily K+ elimination
›Principal cells of cortical collecting duct primary site
›Aldosterone drives K+ secretion via ROMK channels
›Colonic K+ secretion accounts for 5-10%
›Increases adaptively in CKD
›Mechanisms of hyperkalemia
›Reduced renal excretion
›GFR < 15 mL/min/1.73m2 critically impairs excretion
›Aldosterone deficiency or resistance
›Type IV RTA (hyporeninemic hypoaldosteronism)
›Transcellular shift (extracellular redistribution)
›Acidosis: pH decrease 0.1 raises K+ 0.4-0.6 mmol/l
›Insulin deficiency
›Beta-blockade reducing cellular uptake
›Hyperosmolality (hyperglycemia)
›Excess potassium load
›Dietary intake in setting of reduced excretion
›Endogenous release: rhabdomyolysis, hemolysis, TLS
›Exogenous: supplements, salt substitutes, blood products
›Cardiac toxicity mechanism
›Hyperkalemia depolarizes resting membrane potential
›Reduces gap between resting potential and threshold
›Results in reduced cardiac excitability paradoxically
›Slows conduction velocity
›QRS prolongation and arrhythmia
›Rate of K+ rise matters as much as absolute level
›Patients with chronically elevated K+ may have partial adaptation
Therapeutic Considerations
›Rationale for three-tier approach
›Tier 1 protects the heart but does not lower K+
›Calcium buys 30-60 minutes only
›All three tiers must be initiated simultaneously in severe cases
›Tier 2 provides temporary shift — not elimination
›Without Tier 3, K+ will rebound within 4-6 hours
›Shift therapies critical for time while elimination begins
›Tier 3 is the only definitive treatment
›Renal excretion preferred when feasible
›Dialysis for oliguric-anuric patients
›Newer potassium binders vs SPS
›Sodium zirconium cyclosilicate (Lokelma)
›FDA approved 2018
›Phase III HARMONIZE trial: K+ lowering in 48 hours
›Faster onset than patiromer (1-2 hours vs 7 hours)
›Patiromer
›FDA approved 2015
›OPAL-HK trial: enabled continued RAAS inhibitor therapy in CKD-HF
›Better suited for chronic management
›Both preferred over SPS due to safety and efficacy profile
›RAAS inhibitor continuation debate
›Discontinuing RAAS inhibitors trades reduced hyperkalemia for increased CV and renal risk
›RAAS inhibitors provide mortality benefit in HF and diabetic CKD
›KDIGO 2024 guideline: use potassium binders to maintain RAAS inhibitors
›Dietary modification enables RAAS inhibitor continuation in many cases
›Reduction in nonplant potassium sources more impactful than blanket restriction
›Plant-based K+ lower bioavailability
›Monitoring strategy after treatment
›Shift therapies (insulin, albuterol): effect begins 15-30 min, peaks 60 min
›Repeat K+ at 1-2 hours
›Elimination therapies: effect over hours
›Repeat K+ at 4-6 hours
›Rebound hyperkalemia common if source not eliminated
›Serial K+ every 4-6 hours until stable