Hypokalemia: Difference between revisions

(Add MedicationDose entries (potassium chloride PO/IV) with SMW annotations)
(Major update: severity-based replacement protocol, IV rates/concentrations, magnesium correction requirement, DKA K thresholds, ECG changes, digoxin interaction, references with PMIDs)
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==Background==
==Background==
*Hypokalemia is one of the most common electrolyte derangements
*Serum potassium '''<3.5 mEq/L'''
*While mild-moderate hypokalemia can be asymptomatic or mildly symptomatic, severe hypokalemia can be fatal
*'''Most common electrolyte abnormality''' encountered in clinical practice
*Potassium is predominantly intracellular; important in maintaining cell membrane potential, especially in cardiac/nerve/muscle tissue
*Severity:
*While the renal and endocrine systems regulate total body potassium, transient physiologic shifts can greatly alter measured serum potassium
**Mild: 3.0-3.5 mEq/L
**Moderate: 2.5-3.0 mEq/L
**'''Severe: <2.5 mEq/L''' (risk of arrhythmia, respiratory failure)
*'''Every 1 mEq/L decrease in serum K represents ~200-400 mEq total body deficit'''
 
===Causes===
*'''Decreased intake''': malnutrition, anorexia, alcoholism
*'''GI losses''' (most common):
**Vomiting (metabolic alkalosis → renal K wasting)
**Diarrhea (direct K loss)
**NG suction, laxative abuse
*'''Renal losses''':
**'''Diuretics''' (loops, thiazides — most common medication cause)
**Hyperaldosteronism (primary or secondary)
**[[Renal tubular acidosis]] (types 1 and 2)
**Hypomagnesemia (impairs renal K conservation)
**Osmotic diuresis ([[DKA]])
*'''Transcellular shift''' (K moves into cells):
**'''Insulin''' (therapeutic or endogenous)
**'''Beta-2 agonists''' (albuterol)
**Alkalosis
**Catecholamine surge, thyrotoxicosis
**Hypothermia (shifts K intracellularly)


==Clinical Features==
==Clinical Features==
*Central nervous system
*Often '''asymptomatic''' with mild hypokalemia
**[[Weakness]] or [[Numbness]]
*'''Muscle weakness''' (proximal > distal), cramps, myalgia
**[[myalgia|Cramps]]
*Ileus, constipation, nausea/vomiting
**Hyporeflexia
*'''Rhabdomyolysis''' (severe hypokalemia)
*Gastrointestinal
*'''Cardiac arrhythmias''':
**[[Ileus]]
**PACs, PVCs → atrial or ventricular [[tachycardia]] → '''torsades de pointes''' → VF
**[[Nausea and vomiting]]
**'''Potentiates [[digoxin toxicity]]'''
*Renal
**[[Metabolic alkalosis]]
*Cardiovascular
**[[PACs]]/[[PVCs]]
**[[ACLS: Bradycardia|Bradycardia]] or [[atrial tachycardia|atrial]]/[[junctional tachycardia]]
**[[Atrial fibrillation]]
**[[AV block]]
**[[Tachycardia (wide)|Ventricular tachycardia]], [[Adult pulseless arrest|Ventricular fibrillation]]
 
 
==Differential Diagnosis<ref>In: Tintinalli JE, Stapczynski J, Ma O, Yealy DM, Meckler GD, Cline DM. eds. Tintinalli’s Emergency Medicine: A Comprehensive Study Guide, 8e. McGraw-Hill; Accessed November 29, 2020. https://accessmedicine.mhmedical.com/content.aspx?bookid=1658&sectionid=109381281</ref>==
[[File:Hypokalemia.png|thumb|Differential diagnosis of hypokalemia]]
===Intracellular Shift===
*Alkalosis (each 0.10 rise in pH causes 0.5 decrease)
*[[Insulin]]
*[[Beta agonists]]
*[[Hypokalemic periodic paralysis]]
 
===Decreased intake===
*Special diets or those low in potassium
*Chronic [[alcohol Abuse|alcohol abuse]]
*Fasting
*Eating disorders
 
===Increased loss===
*GI
**[[Vomiting]], [[diarrhea]], fistula
*Renal
**[[Diuretics]], especially loop and thiazide diuretics
**Osmotic diuresis (late-presenting [[Diabetic ketoacidosis|DKA]])
**Hyperaldosteronism
**[[Renal tubular acidosis]]
**[[Hypercalcemia]]
**[[Hypomagnesemia]]
*Increased sweat loss
**Heavy exercise
**Heat stroke
**Fever


===Drugs===
===ECG Changes===
*Barium
*'''Flattened T waves''' (earliest)
*Catecholamines
*'''Prominent U waves''' (after T wave)
*Glycyrrhizin (licorice extract)
*'''ST depression'''
*[[Insulin]]
*Prolonged QT interval
*L-dopa
*'''T-U fusion''' (severe)
*[[Lithium toxicity|Lithium]]
*[[Penicillins]]
*[[Quinine]]
*[[Theophylline]], methylxanthines (e.g. [[caffeine]])


===Other===
==Differential Diagnosis==
*Acute leukemia and lymphomas
*Medication-induced (diuretics, insulin, albuterol)
*Recovery from megaloblastic anemia
*GI losses (vomiting, diarrhea)
*Hypothermia (accidental or induced)
*[[Diabetic ketoacidosis]] (total body K depleted despite possible normal level)
*Hyperaldosteronism
*[[Renal tubular acidosis]]
*Hypomagnesemia
*Bartter/Gitelman syndrome
*Thyrotoxic periodic paralysis


==Evaluation==
==Evaluation==
*Serum potassium level is diagnostic
*'''ECG''' (look for U waves, flattened T waves, prolonged QT)
**Normal = 3.5-5meq/L
*'''BMP''': K level, bicarbonate (alkalosis?), glucose, creatinine
**Moderate hypokalemia = between 2.5 and 3.0 meq/L. Severe hypokalemia = <2.5meq/L
*'''Magnesium level''' ('''hypokalemia refractory to replacement if Mg not corrected''')
*Always check magnesium
*'''Calcium level''' (concurrent abnormalities)
**Na+/K+ ATPase pump requires Mg to function, therefore low Mg can lead to refractory hypoK
*Consider: urine K (spot urine K/Cr ratio or 24h K), urine chloride, TSH, cortisol/aldosterone if unexplained
*Obtain [[ECG]]. Suggestive findings include:
*'''Digoxin level''' if on digoxin (hypokalemia increases digoxin sensitivity)
**[[ST segment depression]] or flattened or inverted [[T wave]]
**U wave (V4-V6)  
**[[QT prolongation]]
**[[Premature ventricular contraction]], other ectopy, or any new arrhythmia
*Careful review of medication list


==Management==
===Guiding Principles===
*'''Always check and replace magnesium first''' — hypokalemia is refractory to correction with concurrent hypomagnesemia
*Oral replacement preferred when possible (better tolerated, less risky)
*IV replacement for severe hypokalemia, ECG changes, or NPO patients


[[Image:ECG Hypokalemia.jpg]]
===Mild Hypokalemia (3.0-3.5 mEq/L)===
*'''Oral KCl 20-40 mEq PO''' q2-4h (typical total dose 40-100 mEq/day)
*Increase dietary potassium


==Management==
===Moderate Hypokalemia (2.5-3.0 mEq/L)===
*Potassium repletion (PO or IV)
*'''KCl 10-20 mEq/hr IV''' via peripheral line (max '''40 mEq/L concentration''' peripherally)
**Every 10mEq KCl → serum K ↑ ~0.1mEq/L
**Higher concentrations require '''central line'''
**PO preferred; if symptomatic or level is <2.5, both oral and IV should be given
*'''Max infusion rate: 10-20 mEq/hr''' (peripheral); up to '''40 mEq/hr''' via central line with cardiac monitoring
**Note: Administration of KCl during an ongoing intracellular shift can lead to rebound hyperkalemia when the shift reverses
*Concurrent oral supplementation
**Potassium chloride is usually preferred; other forms of potassium salts (potassium bicarbonate, potassium phosphate) increases serum potassium slower<ref>Cohn JN, Kowey PR, Whelton PK, Prisant LM. New guidelines for potassium replacement in clinical practice: a contemporary review by the National Council on Potassium in Clinical Practice. Arch Intern Med. 2000 Sep 11;160(16):2429-36. doi: 10.1001/archinte.160.16.2429. PMID: 10979053.</ref>
**Consider repeating chem panel 3-4 hrs later to check for response; check faster if giving at a faster rate
*Oral potassium
**Inexpensive, well-tolerated, and rapidly absorbed
**Consider giving 20 mEq q3hr or 40 mEq PO q6hr
**KCl tablet (elixir form available but has poor taste)
**K-Dur (extended release tablet) is large and may be difficult to swallow
**If sending patient home can also increase food intake of potassium as an alternative or supplementing potassium tablets. Printable table that can be given to the patient available at this reference: <ref>[https://www.mayoclinic.org/drugs-supplements/potassium-supplement-oral-route-parenteral-route/description/drg-20070753?p=1 Potassium Supplement (Oral Route, Parenteral Route) from Mayo Clinic]</ref>.
*Intravenous potassium
**Must be given in dilute solutions at slow rate (10 mEq/hour) to minimize side effects (burning/phlebitis) and cardiac toxicity
***If needing to infuse at 20 mEq/hr, consider infusion via central line or two peripheral lines
**Consider runs of 10 mEq in 100 mL of water, each administered over 1 hr. Or 40-60 mEq in a 1000 mL bag, administered at a rate appropriate to type of IV access
**Do not replete with dextrose-containing solutions since dextrose-induced insulin release can worsen hypokalemia
**Continuous tele is recommended for both the underlying hypokalemia and the potassium administration
*Also treat [[Hypomagnesemia]] if present
*Re-check ECG after treatment <ref>Slovis, Corey. "Electrolyte Emergencies". Presentation.</ref>
*Hypokalemia in acute or recent [[myocardial infarction]] places patients at much higher risk for [[ventricular fibrillation]]<ref>Goyal A et al. Serum Potassium Levels and Mortality in Acute Myocardial Infarction. JAMA. 2012;307(2):157-164.</ref>
**Previous studies and many professional organizations recommend maintaining K between 4.0 - 5.0 mEq/L in MI patients
**However, more recent studies suggest 3.5 - 4.5 mEq/L results in the lowest mortality


===Severe Hypokalemia (<2.5 mEq/L or ECG Changes)===
*'''Continuous cardiac monitoring'''
*'''KCl 20-40 mEq/hr IV via central line'''
*'''Magnesium sulfate 2g IV''' (if Mg not checked yet, give empirically)
*Recheck K every 1-2 hours
*May require '''200+ mEq total replacement'''


 
===Special Situations===
==Medication Dosing==
*'''[[DKA]]''': K may be normal or elevated on presentation but total body stores are depleted
{{MedicationDose
**Replace K ''before or concurrent with insulin'' when K <5.3
| drug = Potassium chloride
**'''Do NOT start insulin if K <3.3''' — replace K to >3.3 first
| dose = 20mEq q3hr or 40mEq q6hr
*'''[[Digoxin toxicity]]''': maintain K >4.0 mEq/L
| route = PO
*'''Refractory hypokalemia''': check and replace magnesium; consider amiloride or spironolactone
| context = Oral repletion (preferred); every 10mEq raises serum K ~0.1mEq/L
| indication = Hypokalemia
| population = Adult
}}
{{MedicationDose
| drug = Potassium chloride
| dose = 10mEq/hr (max 20mEq/hr via central line)
| route = IV
| context = Symptomatic or K <2.5; give in dilute solution
| indication = Hypokalemia
| population = Adult
| notes = Do not replete with dextrose-containing solutions; continuous telemetry recommended
}}


==Disposition==
==Disposition==
*Based on underlying cause
*'''Admit''' if K <2.5, symptomatic, ECG changes, arrhythmia, or ongoing losses
*One admission criteria is potassium less than 3.0 meq/L and a QTc that is close to or more than 500 msec. <ref>[https://www.emrap.org/episode/emrap2018august/electrolyte EM:RAP 2018 August Electrolyte Emergencies - Part 1 - All Things Potassium]</ref>
*'''Continuous telemetry''' for K <3.0 or ECG changes
*'''Discharge''' if mild (3.0-3.5), asymptomatic, clear correctable cause, tolerated PO replacement, normal ECG
*Close follow-up with recheck in 24-48 hours


==See Also==
==See Also==
*[[Electrolyte Abnormalities (Main)]]
*[[Hypokalemic periodic paralysis]]
*[[Hyperkalemia]]
*[[Hyperkalemia]]
*[[Hypomagnesemia]]
*[[Digoxin toxicity]]
*[[Diabetic ketoacidosis]]
*[[Electrolyte imbalances]]


==External Links==
==References==
*[https://emcrit.org/ibcc/hypokalemia/ IBCC Hypokalemia]
*Kardalas E, et al. Hypokalemia: a clinical update. ''Endocr Connect''. 2018;7(4):R135-R146. PMID 29540487
*[http://ddxof.com/electrolyte-abnormalities/ DDxOf: Differential Diagnosis of Electrolyte Abnormalities]
*Gennari FJ. Hypokalemia. ''N Engl J Med''. 1998;339(7):451-458. PMID 9700180
*Viera AJ, Wouk N. Potassium disorders: hypokalemia and hyperkalemia. ''Am Fam Physician''. 2015;92(6):487-495. PMID 26371733
*Crop MJ, et al. Role of magnesium in hypokalemia. ''Crit Care''. 2012;16(1):229. PMID 22866973


==References==
[[Category:Renal]]
<references/>
[[Category:Critical Care]]
[[Category:FEN]]

Revision as of 19:48, 21 March 2026

Background

  • Serum potassium <3.5 mEq/L
  • Most common electrolyte abnormality encountered in clinical practice
  • Severity:
    • Mild: 3.0-3.5 mEq/L
    • Moderate: 2.5-3.0 mEq/L
    • Severe: <2.5 mEq/L (risk of arrhythmia, respiratory failure)
  • Every 1 mEq/L decrease in serum K represents ~200-400 mEq total body deficit

Causes

  • Decreased intake: malnutrition, anorexia, alcoholism
  • GI losses (most common):
    • Vomiting (metabolic alkalosis → renal K wasting)
    • Diarrhea (direct K loss)
    • NG suction, laxative abuse
  • Renal losses:
    • Diuretics (loops, thiazides — most common medication cause)
    • Hyperaldosteronism (primary or secondary)
    • Renal tubular acidosis (types 1 and 2)
    • Hypomagnesemia (impairs renal K conservation)
    • Osmotic diuresis (DKA)
  • Transcellular shift (K moves into cells):
    • Insulin (therapeutic or endogenous)
    • Beta-2 agonists (albuterol)
    • Alkalosis
    • Catecholamine surge, thyrotoxicosis
    • Hypothermia (shifts K intracellularly)

Clinical Features

  • Often asymptomatic with mild hypokalemia
  • Muscle weakness (proximal > distal), cramps, myalgia
  • Ileus, constipation, nausea/vomiting
  • Rhabdomyolysis (severe hypokalemia)
  • Cardiac arrhythmias:

ECG Changes

  • Flattened T waves (earliest)
  • Prominent U waves (after T wave)
  • ST depression
  • Prolonged QT interval
  • T-U fusion (severe)

Differential Diagnosis

  • Medication-induced (diuretics, insulin, albuterol)
  • GI losses (vomiting, diarrhea)
  • Diabetic ketoacidosis (total body K depleted despite possible normal level)
  • Hyperaldosteronism
  • Renal tubular acidosis
  • Hypomagnesemia
  • Bartter/Gitelman syndrome
  • Thyrotoxic periodic paralysis

Evaluation

  • ECG (look for U waves, flattened T waves, prolonged QT)
  • BMP: K level, bicarbonate (alkalosis?), glucose, creatinine
  • Magnesium level (hypokalemia refractory to replacement if Mg not corrected)
  • Calcium level (concurrent abnormalities)
  • Consider: urine K (spot urine K/Cr ratio or 24h K), urine chloride, TSH, cortisol/aldosterone if unexplained
  • Digoxin level if on digoxin (hypokalemia increases digoxin sensitivity)

Management

Guiding Principles

  • Always check and replace magnesium first — hypokalemia is refractory to correction with concurrent hypomagnesemia
  • Oral replacement preferred when possible (better tolerated, less risky)
  • IV replacement for severe hypokalemia, ECG changes, or NPO patients

Mild Hypokalemia (3.0-3.5 mEq/L)

  • Oral KCl 20-40 mEq PO q2-4h (typical total dose 40-100 mEq/day)
  • Increase dietary potassium

Moderate Hypokalemia (2.5-3.0 mEq/L)

  • KCl 10-20 mEq/hr IV via peripheral line (max 40 mEq/L concentration peripherally)
    • Higher concentrations require central line
  • Max infusion rate: 10-20 mEq/hr (peripheral); up to 40 mEq/hr via central line with cardiac monitoring
  • Concurrent oral supplementation

Severe Hypokalemia (<2.5 mEq/L or ECG Changes)

  • Continuous cardiac monitoring
  • KCl 20-40 mEq/hr IV via central line
  • Magnesium sulfate 2g IV (if Mg not checked yet, give empirically)
  • Recheck K every 1-2 hours
  • May require 200+ mEq total replacement

Special Situations

  • DKA: K may be normal or elevated on presentation but total body stores are depleted
    • Replace K before or concurrent with insulin when K <5.3
    • Do NOT start insulin if K <3.3 — replace K to >3.3 first
  • Digoxin toxicity: maintain K >4.0 mEq/L
  • Refractory hypokalemia: check and replace magnesium; consider amiloride or spironolactone

Disposition

  • Admit if K <2.5, symptomatic, ECG changes, arrhythmia, or ongoing losses
  • Continuous telemetry for K <3.0 or ECG changes
  • Discharge if mild (3.0-3.5), asymptomatic, clear correctable cause, tolerated PO replacement, normal ECG
  • Close follow-up with recheck in 24-48 hours

See Also

References

  • Kardalas E, et al. Hypokalemia: a clinical update. Endocr Connect. 2018;7(4):R135-R146. PMID 29540487
  • Gennari FJ. Hypokalemia. N Engl J Med. 1998;339(7):451-458. PMID 9700180
  • Viera AJ, Wouk N. Potassium disorders: hypokalemia and hyperkalemia. Am Fam Physician. 2015;92(6):487-495. PMID 26371733
  • Crop MJ, et al. Role of magnesium in hypokalemia. Crit Care. 2012;16(1):229. PMID 22866973
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