Hypokalemia

Aka: Hypokalemia, Hypokalemia Related EKG Changes

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II. Pathophysiology

  1. Approximate Total body Potassium = 55 meq/kg
  2. Serum Potassium decreased 0.3 mEq/L: 100 mEq K+ total body deficit
  3. Serum Potassium decreased 1 mEq/L: 350 mEq K+ total body deficit
  4. Serum Potassium less than 2 mEq/L: 1000 mEq K+ total body deficit

III. Causes

  1. Hypokalemia due to Transcellular Potassium Shift
    1. See Transcellular Potassium Shift
    2. Medications (Beta-agonists, Insulin excess)
    3. Metabolic Alkalosis
    4. Hypokalemic Periodic Paralysis
    5. Thyrotoxicosis
  2. Hypokalemia due to Renal Potassium Loss
    1. See Renal Potassium Loss (Hyperkaluria)
    2. Hypertension: Obtain Plasma Renin and Aldosterone
      1. Renin high
        1. Renovascular disease, renin secreting tumor or Malignant Hypertension
      2. Renin normal
        1. Liddle's Syndrome
      3. Renin low
        1. Aldosterone High: Primary Hyperaldosteronism, Bilateral adrenal hyperplasia
        2. Aldosterone Low: Congenital Adrenal Hyperplasia, Cushing's Syndrome, Ectopic ACTH
    3. Normotensive: Obtain serum bicarbonate and Urine Chloride
      1. Serum Bicarbonate Low
        1. Renal Tubular Acidosis
      2. Serum Bicarbonate High
        1. Urine Chloride Low: Vomiting
        2. Urine Chloride High: Barter's Syndrome, Normotensive primary Hyperaldosteronism, Diuretic use
  3. Hypokalemia due to Extrarenal Potassium Loss
    1. See Extrarenal Potassium Loss
    2. Normal Acid-Base Status or Metabolic Alkalosis
      1. Gastrointestinal or skin losses, Hypomagnesemia, Penicillin or Aminoglycosides, Acute Leukemia
    3. Metabolic Acidosis
      1. Diabetic Ketoacidosis, Diarrhea, Laxatives
  4. Other causes
    1. Inadequate Potassium intake (typically in hospitalized patients)
      1. Total Parenteral Nutrition
      2. Anorexia or Starvation
      3. Dementia
    2. Pseudohypokalemia
      1. Delayed lab analysis of sample
      2. Severe Leukocytosis (>75,000/mm3)

IV. Findings: Symptoms and Signs (when Serum Potassium < 2.5 mEq/L)

  1. General
    1. Malaise
    2. Fatigue
  2. Neurologic
    1. Weakness
    2. Decreased Deep Tendon Reflexes
    3. Paresthesia
    4. Cramps
    5. Restless Legs Syndrome
    6. Rhabdomyolysis
    7. Paralysis
  3. Gastrointestinal
    1. Constipation
    2. Ileus
    3. Exacerbated Hepatic Encephalopathy
  4. Cardiovascular
    1. Orthostatic Hypotension
    2. Hypertension
    3. Arrhythmias (rare in otherwise healthy patients)
      1. Acute or recent Myocardial Infarction (5 fold increased risk of Ventricular Fibrillation if K+ <3.9 mEq/L)
      2. Digoxin use and Hypokalemia predisposes to arrhythmia
  5. Renal
    1. Metabolic Alkalosis
    2. Polyuria, Polydipsia
    3. Decreased GFR
    4. Glucose Intolerance

V. Labs

  1. Serum Potassium <3.5 mEq/L
  2. Serum Magnesium
    1. Confirm no Hypomagnesemia (Hypokalemia cause)
  3. Complete Blood Count
    1. Confirm no severe Leukocytosis (pseudohypokalemia)
  4. 24 hour Urine Potassium and Urine Sodium
    1. Most accurate evaluation of Urine Potassium excretion
    2. However, Urine Potassium-to-Creatinine ratio is typically obtained instead
    3. Sample should have total Urine Sodium > 100 meq
    4. Urine Potassium <20-30 meq/day
      1. See Extrarenal Potassium Loss
    5. Urine Potassium >20-30 meq/day
      1. See Renal Potassium Loss
  5. Urine Potassium-to-Creatinine ratio
    1. Ratio <=1.5 mEq/mmol: Hypokalemia due to Extrarenal Potassium Loss
      1. Manage underlying losses
    2. Ratio >1.5 mEq/mmol: Hypokalemia due to Renal Potassium Loss
      1. Elevated Blood Pressure or hypervolemia (mineralcorticoid excess)
        1. Hyperaldosteronism
        2. Renal Artery Stenosis
        3. Cushing Syndrome
        4. Congenital Adrenal Hyperplasia
      2. Metabolic Acidosis
        1. Type I and II Renal Tubular Acidosis
      3. Metabolic Alkalosis
        1. Diuretics
        2. Renal Tubular transport disorders (e.g. Bartter Syndrome)

VI. Diagnostics: Electrocardiogram

  1. Early changes
    1. T Waves decreased amplitude to flattened
  2. Later changes
    1. Prominent U Waves
    2. ST depression
    3. T Wave inversion
    4. PR prolongation (first degree AV Block)
    5. QTc Prolongation
  3. Arrhythmias associated with Hypokalemia
    1. Sinus Bradycardia
    2. Ventricular Tachycardia or Ventricular Fibrillation
    3. Torsade de pointes

VII. Management: General

  1. Potassium Replacement
    1. Goal Serum Potassium >3.5 mEq/L (>4.0 in CAD, CHF)
    2. Total body Potassium deficit
      1. Serum Potassium: <3.5 mEq/L = 100 meq total Potassium deficit
      2. Serum Potassium: 3.2 mEq/L = 200 meq total Potassium deficit
      3. Serum Potassium: 2.9 mEq/L= 300 meq total Potassium deficit
      4. Serum Potassium: 2.6 mEq/L = 400 meq total Potassium deficit
    3. Avoid rebound Hyperkalemia (over-shooting replacement)
      1. Hyperkalemia with replacement is unlikely if normal Renal Function, adequate fluid intake
    4. Dietary Potassium (Potassium phosphate) is less efficient replacement than Potassium chloride
      1. Most Hypokalemia is associated with concurrent chloride depletion
      2. However Potassium chloride compliance is poor (Dyspepsia, Dietary Potassium tastes better)
    5. Half of Potassium Replacement is typically excreted by the Kidneys
      1. Aside from Renal Failure and dehydration, at least half of Potassium Replacement (esp. oral) is excreted
    6. Approximate oral replacement
      1. Serum Potassium < 3.0 mEq/L (total body deficit 200-300 meq)
        1. Start with KCl 20 meq orally every 2 hours for 4 doses and consider recheck level
        2. Typically continue Potassium Replacement at 20 meq twice daily for 4-5 days
      2. Serum Potassium: 3.0 to 3.5 mEq/L(total body deficit 100-200 meq)
        1. Give KCl 20 mEq orally every 2 hours for 2 doses OR KCl 40 mEq once
        2. Typically continue Potassium Replacement at 20 meq twice daily for 2-3 days
  2. Magnesium Replacement (empirically or based on lab demonstrated Hypomagnesemia)
    1. Especially consider empiric Magnesium Replacement in refractory Hypokalemia
    2. Take oral Magnesium supplement 400-500 mg tabs 1-2 daily along with Potassium supplement
  3. Emergent replacement indicated for serious findings or risks
    1. EKG changes (esp. QTc Prolongation, see above)
    2. Severe Hypokalemia (Serum Potassium <2.5 mEq/L)
    3. Rapid onset Hypokalemia
    4. Serious comorbidity (heart disease, Cirrhosis)
  4. Consider pseudohypokalemia
    1. Consider re-drawing lab for confirmation if delayed analysis
    2. Confirm no severe Leukocytosis (WBC >75,000/mm3)
  5. Consider Transcellular Potassium Shift
    1. See Transcellular Potassium Shift
    2. Hypokalemia from transcellular shift is typically transient

VIII. Management: Hospital Replacement Criteria

  1. Hypokalemia with Serum Potassium <3.0 mEq/L AND QTc Prolongation >500 ms
  2. Severe Hypokalemia with Serum Potassium <2.5 mEq/L

IX. References

  1. Orman and Slovis in Herbert (2018) EM:Rap 18(8): 4-5
  2. Viera (2015) Am Fam Physician 92(6): 487-95 [PubMed]

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Related Studies

Ontology: Hypokalemia (C0020621)

Definition (MSHCZE) Nízká koncentrace draslíku v krvi. Vzniká při větších ztrátách kalia močí např. v polyurické fázi renálního selhání, při léčbě diuretiky (furosemidem, saluretiky), při hyperaldosteronismu, v důsledku ztrát při průjmech atd. Způsobuje svalovou slabost, poruchu trávení (hypotonie hladkých svalů), poruchy srdeční činnosti (arytmie), ledvin aj. Na EKG se projevuje zvýrazněním vlny U. (cit. Velký lékařský slovník online, 2012, http://lekarske.slovniky.cz/ )
Definition (NCI) Lower than normal levels of potassium in the circulating blood.
Definition (NCI_CTCAE) A disorder characterized by laboratory test results that indicate a low concentration of potassium in the blood.
Definition (MSH) Abnormally low potassium concentration in the blood. It may result from potassium loss by renal secretion or by the gastrointestinal route, as by vomiting or diarrhea. It may be manifested clinically by neuromuscular disorders ranging from weakness to paralysis, by electrocardiographic abnormalities (depression of the T wave and elevation of the U wave), by renal disease, and by gastrointestinal disorders. (Dorland, 27th ed)
Definition (CSP) abnormally low potassium concentration in the blood; may result from excessive potassium loss by the renal or gastrointestinal route, from decreased intake, or from transcellular shifts; manifested clinically by neuromuscular disorders ranging from weakness to paralysis, by electrocardiographic abnormalities, and by renal and gastrointestinal disorders.
Concepts Finding (T033)
MSH D007008
ICD9 276.8
ICD10 E87.6
SnomedCT 190900003, 154762003, 267508008, 166690008, 43339004
LNC LA15423-9
English Hypokalemias, Hypopotassemia, Hypopotassemias, HYPOKALAEMIA, HYPOKALEMIA, HYPOPOTASSAEMIA, HYPOPOTASSEMIA, LOW POTASSIUM SYNDROME, hypokalemia, hypokalemia (diagnosis), Syndrome hypokalemic, Low potassium syndrome, Potassium [K] deficiency, Hypokalemia [Disease/Finding], hypopotassemia, potassium deficiency, deficiency k, deficiency potassium, hypopotassaemia, k deficiency, potassium depletion, hypokalemias, Hypokalaemia (disorder), Hypokalemic disorder, Serum potassium concentration decreased below normal, Syndrome hypokalaemic, Hypokalemic syndrome, Hypopotassemia syndrome, Hypokalaemia, Hypopotassaemia, Hypokalaemic syndrome, Low serum potassium level, Hypokalemia (disorder), Hypopotassaemia syndrome, Low serum potassium level (finding), Low serum potassium level - finding, hypokalemic; syndrome, syndrome; hypokalemic, Hypokalemia, hypokalaemia
French HYPOKALIEMIE, Hypopotassémie, Syndrome hypocalémique, Syndrome de carence en potassium, HYPOPOTASSEMIE, SYNDROME HYPOKALIEMIQUE, Syndrome hypokaliémique, Hypokaliémie
German HYPOKALIAEMIE, Syndrom, hypokalaemisch, Kalium niedrig Syndrom, KALIUMMANGELSYNDROM, SERUMKALIUM NIEDRIG, Hypokaliaemie, Hypokaliaemie-Syndrom, Kaliummangel, Hypokaliämie
Portuguese HIPOPOTASSEMIA, Síndrome de falta de potássio, Síndrome hipocaliémica, HIPOKALIEMIA, SINDROME HIPOCALIEMICO, Hipocaliemia, Síndrome de hipocaliemia, Hipopotassemia
Spanish HIPOPOTASEMIA, Síndrome hipocaliémico, Síndrome de potasio bajo, Síndrome hipocalémico, HIPOCALIEMIA, HIPOPOTASEMIA, SINDROME, síndrome hipopotasémico, hipokalemia, hipocalemia, síndrome hipocálemico, hipocaliemia (trastorno), hipocaliemia, hipopotasemia, nivel sérico de potasio bajo (hallazgo), nivel sérico de potasio bajo, Hipocaliemia, Síndrome hipopotasiémico, Hipopotasemia, Hipokalemia
Italian Ipokaliemia, Sindrome ipokaliemica, Ipopotassemia, Sindrome da ipopotassiemia, Ipopotassiemia
Dutch hypokaliëmisch syndroom, laag kalium syndroom, hypokaliëmisch; syndroom, syndroom; hypokaliëmisch, hypokalemisch syndroom, hypokaliëmie, Hypopotassemie, Hypokaliëmie, Kaliëmie, hypo-
Japanese 低カリウム症候群, 低カリウム血症候群, ﾃｲｶﾘｳﾑｹﾂｼｮｳ, ﾃｲｶﾘｳﾑｹｯｼｮｳ, ﾃｲｶﾘｳﾑｼｮｳｺｳｸﾞﾝ, ﾃｲｶﾘｳﾑｹﾂｼｮｳｺｳｸﾞﾝ, 低カリウム血症, 低K血症, 低カリウム血, 低ポタシウム血症
Swedish Hypokalemi
Finnish Hypokalemia
Russian GIPOKALIEMIIA, ГИПОКАЛИЕМИЯ
Czech Hypokalemický syndrom, Hypokalemie, hypokalemie, hypokalémie
Korean 저칼륨혈증
Polish Hipopotasemia, Hipokaliemia
Hungarian Hypokalaemiás syndroma, Hypokalemia, Hypokaaemiás syndroma, Hypokalaemia, Hypopotassaemia, Alacsony kálium syndroma
Norwegian Hypokalemi
Derived from the NIH UMLS (Unified Medical Language System)

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