Episode 189: Hyperkalemia 2.0

Show Notes

Introduction

1. Background

• • Physiology:
    • Normal range and the significance of deviations (>5.5 mEq/L)
  • Epidemiology:
    • Prevalence of hyperkalemia in the ER
    • ESRD missed HD → ECG, monitor

Causes / Risk Factors

• • Causes
    • Kidney Dysfunction, Medications,  Cellular Destruction,  Endocrine Causes, Pseudohyperkalemia

• • High-Risk Medications:

• • • Antibiotics: Bactrim, antifungals

• • • Calcineurin inhibitors

• • • Beta-blockers

• • • ACE/ARB

• • • K+ Sparing diuretics

• • • NSAIDs

• • • Digoxin

• • • SUX – high risks in neuromuscular disease

• • Lab errors, hemolysis in samples
    • VBG vs Chem accuracy 
    • When to repeat a hemolyzed sample 
    • 2023 study: Of the 145 children with hemolyzed hyperkalemia, 142 (97.9%) had a normal repeat potassium level. Three children (2.1%) had true hyperkalemia: one had known chronic renal failure and was referred to the ED due to concern for electrolyte abnormalities; the other 2 patients had diabetic ketoacidosis (DKA).

Clinical Presentation / eval 

• Symptomatic vs. Asymptomatic:
  • “First symptom of hyperkalemia is death” 
  • If severe, ascending muscle weakness → paralysis 
    • Point at which patients experience symptoms depends on chronicity
      • >7 mEq/L if chronic and can be lower if acute
  • Hyperkalemia can be a cause of non-specific GI symptoms
• EKG Changes:
  • ECG findings may be the first marker the ER doc gets that something is wrong
  • Typical changes: 
    • Peaked T-waves, shortened QT
    • Lengthening of PR interval and QRS duration 
    • Bradycardia / Junctional rhythm
      • Hyperkalemia can produce bradycardia without other ECG findings
    • Ones associated with VT/VF/code, death in one study: QRS widening (RR = 4.74), Junctional Rhythm (RR = 7.46), HR <50 (RR = 12.29) while no adverse outcomes with just peaked T waves or PR prolongation (Durfey, 2017)
  • Don’t be fooled by a normal ECG, may be normal, but it’s also on case report level to have K > 9 and a normal ECG
    • Series of 127 patient (K 6-9.3), no serious arrhythmia noted, only 46% had ECG changes, (Acker, 1998)
  • ECG changes are not linear, there is no exact association between K+ levels and ECG changes
  • ECG changes may be hidden and subtle in patients with underlying inter-ventricular conduction delay (BBBs)
    • Be suspicious of the patient with LBBB > 160 ms or RBBB > 140 ms
  • BRASH Syndrome
    • Synergism between hyperkalemia, renal failure/injury and AV nodal blocking agents -> may produce ECG changes out of proportion to serum potassium levels. 
• Labs
  • Chem, VBG, +/- CK if you think muscle breakdown is at play (Tintinalli talks about looking at urine K, but this is not most people’s practice)
  • Consider evaluation for adrenal insufficiency
  • Waiting for labs may not be an option
    • Renal dysfunction + consistent ECG findings → prompt treatment before chem results
    • Realistically 2 hours to get back chemistry in most settings ≈ eternity

Management in the ER

• Discontinue/hold any nephrotoxins or medications in suspected medication-induced hyperkalemia

• A. Acute Management Strategies:
  • Cardiac protection with calcium