Updated: 2/8/2019

Electrolyte Disturbances

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Snapshot
  • A 56-year-old man is brought to the emergency department by his son due to mild confusion and shortness of breath. Prior to symptom develop he needed to sleep on a recliner due to feeling short of breath while supine. Medical history is significant for chronic obstructive pulmonary disease and a prior myocardial infarction requiring coronary artery bypass grafting. On physical exam, the patient is altered but able to follow commands. There is jugular venous distension, an S3 heart sound, and 2+ lower extremity pitting edema. Laboratory testing is significant for a brain natriuretic peptide 950 pg/mL and serum sodium of 130 mmol/L. (Hyponatremia secondary to congestive heart failure)
Potassium
 
Electrolyte Disturbances
Hyponatremia Hypernatremia
  • Definition
    • serum sodium of < 135 mmol/L
  • Etiology
    • pseudohyponatremia
      • hyperglycemia
      • hyperlipidemia
    • hypervolemic hyponatremia
      • congestive heart failure
      • nephrotic syndrome
      • cirrhosis
      • renal insufficiency
    • hypovolemic hyponatremia 
      • vomiting and diarrhea
      • burns
      • sweating
      • cystic fibrosis
      • diuretic use (e.g., thiazides)
      • angiotensin converting enzyme (ACE) inhibitor
      • adrenal insufficiency
    • euvolemic hyponatremia
      • psychogenic polydipsia 
      • hypothyroidism
      • syndrome of inappropriate anti-diuretic hormone (SIADH)
      • diuretic use
      • ACE inhibitors
  • Presentation
    • stupor
    • coma
    • seizures 
    • nausea
    • malaise
  • Studies
    • assess volume status
    • serum electrolyte and urine studies
  • Treatment
    • address underlying cause
    • asymptomatic
      • free water restriction 
    • moderate hyponatremia
      • IV normal saline
        • loop diuretics may be added
    • severe hyponatremia
      • hypertonic (3%) saline
  • Complications
    • rapid correction of hyponatremia can lead to osmotic demyelination syndrome 
  • Definition
    • serum sodium of > 145 mmol/L
  • Etiology
    • insensible losses (e.g., sweating)
    • osmotic diarrhea
    • osmotic diuresis
      • e.g., diabetic ketoacidosis
    • poor fluid intake
    • diuretic use
    • osmotic diuresis
    • vomiting and diarrhea
    • central and nephrogenic diabetes insipidus
    • hypertonic sodium gain
  • Presentation
    • stupor
    • coma
    • seizure
  • Studies
    • assess volume status
    • serum electrolyte and urine studies
  • Treatment
    • address underlying cause 
    • intravenous (IV) 5% dextrose in water (D5W) 
    • isotonic fluids when hypovolemic 
  • Complications
    • rapid corrrection of hypernatremia can lead to cerebral edema and herniation
Hypokalemia Hyperkalemia
  • Defintion
    • serum potassium of < 3.5 mEq/L
  • Etiology
    • ↑ insulin
    • hyperglycemia
      • this stimulates endogenous insulin secretion from the pancreas in normal conditions
    • β2-adrenergic agonists
    • alkalosis
    • hyposmolality
    • diarrhea 
  • Presentation
    • muscle and cardiac dysfunction
      • muscular symptoms
        • abdominal cramping
        • muscle weakness and cramping
      • cardiac symptoms
        • palpitations
    • parasthesias
    • nausea and vomiting
  • Studies
    • electrocardiogram (ECG) findings
      • U waves
      • T wave flattening
  • Treatment
    • address underlying cause
    • potassium repletion
      • remember to not use dextrose-containing fluids as this will stimulate insulin release and shift potassium within the cell
        • this worsens the hypokalemia
    • replace magnesium in magnesium deficiency
  • Definition
    • serum potassium of > 5-5.5 mEq/L
  • Etiology
    • insulin deficiency
    • β2-adrenergic antagonists
    • acidosis
      • cells attempt to buffer excess hydrogen ions to shift these ions into the cells
        • in exchange for this intracellular uptake of hydrogen, potassium is transferred out the cell
          • this attempts to achieve electroneutrality
    • digitalis
      • secondary to dose-dependent Na+/K+ -ATPase pump inhibition
    • cell lysis (e.g., rhabdomyolysis)
    • exercise
    • hyperosmolarity
    • succinylcholine 
    • TMP-SMX 
    • ACE inhibitors 
  • Presentation
    • muscle and cardiac dysfunction
      • muscular symptoms
        • myalgias
        • muscle paralysis
        • chest pain
      • cardiac symptoms
        • arrhythmias and palpitations
    • nausea and vomiting
    • parasthesias
  • Studies
    • ECG findings
      • peaked T waves and wide QRS
  • Treatment 
    • address underlying cause
    • IV calcium gluconate  
      • has no effect on potassium levels but stabilizes the myocardium
    • shifting potassium within cells 
      • insulin plus glucose
      • β2-adrenergic agonists
    • lowering body potassium
      • sodium polystyrene sulfonate
        • this is a cation exchange resin
    • dialysis
      • used in patients unresponsive to medical therapy
Hypocalcemia Hypercalemia
  • Definition
    • serum total calcium < 8.4 mg/dL
      • decreased albumin can cause a decreased total calcium but a normal free calcium (thus the patient is asymptomatic) 
    • ionized fraction of calcium < 4.4 mg/dL 
  • Etiology
    • renal failure
    • hypoparathyroidism
    • vitamin D deficiency
    • hypomagnesemia
      • inhibits PTH release
    • pancreatitis
    • alkalemia 
  • Presentation
    • seizures
    • tetany 
    • Chvostek sign
      • ipsilateral facial muscle contraction caused by tapping the facial nerve
    • Trousseau sign
      • carpopedal spasms by inflating the sphygmomanometer above systolic blood pressure
  • Studies
    • QTc prolongation
  • Treatment
    • address underlying cause
    • asymptomatic or patients with chronic hypocalcemia
      • oral calcium replacement therapy such as
        • calcium citrate
        • calcium carbonate
      • vitamin D supplementation
      • thiazides for patients with hypoparathyroidism
    • symptomatic patients
      • IV calcium gluconate
        • first-line
    • chronic renal failure
      • phosphate binders
      • oral calcium replacement
      • calcitriol
  • Definition
    • serum total calcium > 10.5 mg/dL
    • ionized fraction of calcium > 5.6 mg/dL
  • Etiology
    • hyperparathyroidism
    • humoral hypercalcemia of malignancy
      • secondary to parathyroid hormone-related peptide (PTHrP)
      • associated with squamous cell cancer and solid tumors involving the
        • lung
        • esophageus
        • skin
        • cervix
        • breast
        • kidney
    • vitamin D overdose
    • granulomatous diseases like
      • sarcoidosis
    • thiazide diuretics
    • lithium
    • calcium-containing antacids
    • familial hypocalciuric hypercalcemia 
    • immobilization
  • Presentation
    • nephrolithiasis
    • polyuria
    • muscle weakness
    • bone pain
    • abdominal pain 
      • secondary to bowel hypomotility and constipation 
    • confusion
    • stupor
    • coma
    • mnemonic: stones (renal), bones (pain), groans (abdominal pain), thrones (↑ urinary frequency), and psychiatric overtones (altered mental status)
  • Studies
    • ECG
      • shortened QTc interval
  • Treatment
    • address underlying cause
    • IV isotonic normal saline 
      • increases urinary calcium excretion
    • calcitonin
      • impairs bone resorption
      • increases urinary calcium excretion
    • bisphosphonates (e.g., zoledronic acid and pamidronate)  
      • has a delayed onset of action
      • impairs bone resorption
      • long term calcium control
    • loops diuretics
      • increases urinary calcium excretion
Hypomagnesemia Hypermagnesemia
  • Definition
    • typically serum magnesium < 1.8 mg/dL
  • Etiology
    • magnesium redistribution
      • refeeding syndrome
    • malnutrition
    • alcohol use disorder
    • anorexia nervosa
    • proton pump inhibitors
    • loop diuretics
    • digoxin
  • Presentation
    • tetany
    • torsades de pointes
    • hypokalemia
    • hypocalcemia
      • when significant (< 1.2 mg/dL)
  • Studies
    • ECG
      • U waves
      • T wave flattening
      • QT prolongation
      • widened QRS complexes
  • Treatment
    • magnesium repletion
      • asymptomatic
        • oral magnesium supplementation
      • severe or symptomatic hypomagnesemia
        • IV magnesium sulfate
  • Definition
    • typically serum magnesium > 2.6 mg/dL
  • Etiology
    • increased magnesium ingestion
      • magnesium cathartics
      • antacids
      • laxatives
      • dietary supplements
    • renal insufficiency
  • Presentation
    • ↓ deep tendon reflexes
    • bradycardia
    • cardiac arrest
    • hypocalcemia
  • Studies
    • ECG
      • PR, QRS, and QT prolongation
      • heart block
  • Treatment
    • address underlying cause
    • IV isotonic saline
    • loop diuretics can be considered
Hypophosphatemia Hyperphosphatemia
  • Definition
    • serum phosphate < 2.5 mg/dL
  • Etiology
    • refeeding syndrome 
    • hungry bone syndrome
    • inadquate phosphate intake
    • hyperparathyroidism
    • phosphate binders
  • Presentation
    • weakness
    • muscle and bone pain
    • osteomalacia
    • rickets
  • Treatment
    • address underlying cause
    • mild hypophosphatemia
      • increase dietary phosphate intake
    • moderate hypophosphatemia
      • oral phosphate replacement therapy
        • IV phosphate replacement in patients who are on a ventilator
    • severe hypophosphatemia
      • IV phosphate replacement
  • Definition
    • serum phosphate > 4.5 mg/dL
  • Etiology
    • acute phosphate ingestion
    • hypoparathyroidism
    • vitamin D toxicity
    • renal failure
    • rhabdomyolysis
    • tumor lysis syndrome
  • Presentation
    • typically asymptomatic
  • Treatment
    • address underlying cause
    • dietary modifications
    • phosphate binders
      • calcium carbonate or acetate
 
 

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Questions (11)
Lab Values
Blood, Plasma, Serum Reference Range
ALT 8-20 U/L
Amylase, serum 25-125 U/L
AST 8-20 U/L
Bilirubin, serum (adult) Total // Direct 0.1-1.0 mg/dL // 0.0-0.3 mg/dL
Calcium, serum (Ca2+) 8.4-10.2 mg/dL
Cholesterol, serum Rec: < 200 mg/dL
Cortisol, serum 0800 h: 5-23 μg/dL //1600 h:
3-15 μg/dL
2000 h: ≤ 50% of 0800 h
Creatine kinase, serum Male: 25-90 U/L
Female: 10-70 U/L
Creatinine, serum 0.6-1.2 mg/dL
Electrolytes, serum  
Sodium (Na+) 136-145 mEq/L
Chloride (Cl-) 95-105 mEq/L
Potassium (K+) 3.5-5.0 mEq/L
Bicarbonate (HCO3-) 22-28 mEq/L
Magnesium (Mg2+) 1.5-2.0 mEq/L
Estriol, total, serum (in pregnancy)  
24-28 wks // 32-36 wks 30-170 ng/mL // 60-280 ng/mL
28-32 wk // 36-40 wks 40-220 ng/mL // 80-350 ng/mL
Ferritin, serum Male: 15-200 ng/mL
Female: 12-150 ng/mL
Follicle-stimulating hormone, serum/plasma Male: 4-25 mIU/mL
Female: premenopause: 4-30 mIU/mL
midcycle peak: 10-90 mIU/mL
postmenopause: 40-250
pH 7.35-7.45
PCO2 33-45 mmHg
PO2 75-105 mmHg
Glucose, serum Fasting: 70-110 mg/dL
2-h postprandial:<120 mg/dL
Growth hormone - arginine stimulation Fasting: <5 ng/mL
Provocative stimuli: > 7ng/mL
Immunoglobulins, serum  
IgA 76-390 mg/dL
IgE 0-380 IU/mL
IgG 650-1500 mg/dL
IgM 40-345 mg/dL
Iron 50-170 μg/dL
Lactate dehydrogenase, serum 45-90 U/L
Luteinizing hormone, serum/plasma Male: 6-23 mIU/mL
Female: follicular phase: 5-30 mIU/mL
midcycle: 75-150 mIU/mL
postmenopause 30-200 mIU/mL
Osmolality, serum 275-295 mOsmol/kd H2O
Parathyroid hormone, serume, N-terminal 230-630 pg/mL
Phosphatase (alkaline), serum (p-NPP at 30° C) 20-70 U/L
Phosphorus (inorganic), serum 3.0-4.5 mg/dL
Prolactin, serum (hPRL) < 20 ng/mL
Proteins, serum  
Total (recumbent) 6.0-7.8 g/dL
Albumin 3.5-5.5 g/dL
Globulin 2.3-3.5 g/dL
Thyroid-stimulating hormone, serum or plasma .5-5.0 μU/mL
Thyroidal iodine (123I) uptake 8%-30% of administered dose/24h
Thyroxine (T4), serum 5-12 μg/dL
Triglycerides, serum 35-160 mg/dL
Triiodothyronine (T3), serum (RIA) 115-190 ng/dL
Triiodothyronine (T3) resin uptake 25%-35%
Urea nitrogen, serum 7-18 mg/dL
Uric acid, serum 3.0-8.2 mg/dL
Hematologic Reference Range
Bleeding time 2-7 minutes
Erythrocyte count Male: 4.3-5.9 million/mm3
Female: 3.5-5.5 million mm3
Erythrocyte sedimentation rate (Westergren) Male: 0-15 mm/h
Female: 0-20 mm/h
Hematocrit Male: 41%-53%
Female: 36%-46%
Hemoglobin A1c ≤ 6 %
Hemoglobin, blood Male: 13.5-17.5 g/dL
Female: 12.0-16.0 g/dL
Hemoglobin, plasma 1-4 mg/dL
Leukocyte count and differential  
Leukocyte count 4,500-11,000/mm3
Segmented neutrophils 54%-62%
Bands 3%-5%
Eosinophils 1%-3%
Basophils 0%-0.75%
Lymphocytes 25%-33%
Monocytes 3%-7%
Mean corpuscular hemoglobin 25.4-34.6 pg/cell
Mean corpuscular hemoglobin concentration 31%-36% Hb/cell
Mean corpuscular volume 80-100 μm3
Partial thromboplastin time (activated) 25-40 seconds
Platelet count 150,000-400,000/mm3
Prothrombin time 11-15 seconds
Reticulocyte count 0.5%-1.5% of red cells
Thrombin time < 2 seconds deviation from control
Volume  
Plasma Male: 25-43 mL/kg
Female: 28-45 mL/kg
Red cell Male: 20-36 mL/kg
Female: 19-31 mL/kg
Cerebrospinal Fluid Reference Range
Cell count 0-5/mm3
Chloride 118-132 mEq/L
Gamma globulin 3%-12% total proteins
Glucose 40-70 mg/dL
Pressure 70-180 mm H2O
Proteins, total < 40 mg/dL
Sweat Reference Range
Chloride 0-35 mmol/L
Urine  
Calcium 100-300 mg/24 h
Chloride Varies with intake
Creatinine clearance Male: 97-137 mL/min
Female: 88-128 mL/min
Estriol, total (in pregnancy)  
30 wks 6-18 mg/24 h
35 wks 9-28 mg/24 h
40 wks 13-42 mg/24 h
17-Hydroxycorticosteroids Male: 3.0-10.0 mg/24 h
Female: 2.0-8.0 mg/24 h
17-Ketosteroids, total Male: 8-20 mg/24 h
Female: 6-15 mg/24 h
Osmolality 50-1400 mOsmol/kg H2O
Oxalate 8-40 μg/mL
Potassium Varies with diet
Proteins, total < 150 mg/24 h
Sodium Varies with diet
Uric acid Varies with diet
Body Mass Index (BMI) Adult: 19-25 kg/m2
Calculator

(M2.RL.30) A 19-year-old male with cystic fibrosis is evaluated in the clinic for regular health maintenance. He is compliant with his respiratory therapy, but states that he often "forgets" to take the medications before he eats. A panel of labs is drawn which reveals a moderate vitamin D deficiency. Which of the following electrolyte abnormalities might be seen as a consequence of vitamin D deficiency? Review Topic

QID: 104304
1

Increased calcium and increased phosphate

0%

(0/76)

2

Increased calcium and decreased phosphate

4%

(3/76)

3

Decreased calcium and increased phosphate

36%

(27/76)

4

Decreased calcium and decreased phosphate

55%

(42/76)

5

Normal calcium and decreased phosphate

4%

(3/76)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 4

(M2.RL.4830) A 75-year-old man with coronary artery disease and mitral valve stenosis status-post coronary artery bypass graft and mitral bioprosthetic valve replacement is evaluated in the intensive care unit. His postsurgical course was complicated by ventilator-associated pneumonia and bilateral postoperative pleural effusions requiring chest tubes. He has been weaned from the ventilator and has had his chest tubes removed but has required frequent suctioning to minimize aspirations. He has been dependent on a percutaneous gastrostomy tube for enteral nutrition for the past four weeks. He is currently on aspirin, carvedilol, atorvastatin, ceftazidime, and pantoprazole. He has a history of prostate cancer status post radical prostatectomy. His temperature is 96°F (35.6°C), blood pressure is 95/55 mmHg, pulse is 50/min, and respirations are 20/min. On physical exam, he is not alert and oriented but responds with moans when stimulated. His laboratory data are listed below:

Serum:
Na+: 145 mEq/L
Cl-: 110 mEq/L
K+: 3.4 mEq/L
HCO3-: 26 mEq/L
BUN: 10 mg/dL
Glucose: 112 mg/dL
Creatinine: 1.4 mg/dL
Thyroid-stimulating hormone: 10 µU/mL
Ca2+: 11.1 mg/dL
PO4-: 1.0 mg/dL
AST: 6 U/L
ALT: 10 U/L
Albumin: 2.5 mg/dL
Lactate dehydrogenase: 200 U/L (140-280 U/L)
Haptoglobin: 150 mg/dL (30-200 mg/dL)
1,25-(OH)2 D3: 10 pg/mL (15-75 pg/mL)
Parathyroid hormone: 9 pg/mL (10-60 pg/mL)

Leukocyte count: 10,000 cells/mm^3 with normal differential
Hemoglobin: 9 g/dL
Hematocrit: 30 %
Platelet count: 165,000 /mm^3

His electrocardiogram and chest radiograph are shown in Figures A and B. What is the most likely cause of his hypercalcemia? Review Topic

QID: 109466
FIGURES:
1

Hemolytic anemia

0%

(0/43)

2

Euthyroid sick syndrome

12%

(5/43)

3

Immobilization

70%

(30/43)

4

Malignancy

12%

(5/43)

5

Primary hyperparathyroidism

7%

(3/43)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 3

(M2.RL.4799) A 62-year-old male with a history of chronic lymphocytic leukemia is admitted to the hospital for chemotherapy with fludarabine after transformation into prolymphocytic leukemia. Three days later, the nurse calls you because the patient is vomiting. The patient reports he is nauseous and he feels weak. On physical exam, he is ill-appearing, and you appreciate diffuse, bilateral lymphadenopathy, symmetrical muscle weakness, and bilateral areflexia. Labs are drawn and an electrocardiogram (EKG) is obtained, which is shown in Figure A. In addition to cardiac stabilization, which of the following is the best next step in management? Review Topic

QID: 109340
FIGURES:
1

Albuterol

52%

(15/29)

2

Allopurinol

7%

(2/29)

3

Furosemide

3%

(1/29)

4

Rasburicase

21%

(6/29)

5

Sodium polystyrene sulfonate

17%

(5/29)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 1

(M2.RL.20) A 58-year-old man complains of ascending weakness, palpitations, and abdominal pain. He has a history of hypertension, type II diabetes mellitus, diabetic retinopathy, and end-stage renal disease requiring dialysis. He denies any recent infection. Physical examination is notable for decreased motor strength in both his upper and lower extremities, intact cranial nerves, as well as decreased bowel sounds. On further questioning, the patient shares that he has been depressed, as he feels he may not be able to see his grandchildren grow due to his complicated medical course. This caused him to miss two of his dialysis appointments. Which of the following will mostly likely be found on electrocardiography? Review Topic

QID: 105386
1

Progressive PR prolongation, followed by a 'drop' in QRS

0%

(0/0)

2

S wave in lead I, Q wave in lead III, and inverted T wave in lead III

0%

(0/0)

3

ST-segment elevation in leads II, III, and aVF

0%

(0/0)

4

Peaked T-waves and shortened QT interval

0%

(0/0)

5

Diffuse PR segment depression and ST-segment deviations

0%

(0/0)

M2

Select Answer to see Preferred Response

PREFERRED RESPONSE 4
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