Diagnosis and Management of Common Electrolyte Disorders

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Diagnosis and Management of Common Electrolyte
Disorders

• Eric I. Rosenberg, MD, MSPH, FACP

Rev 11/06 electrolytes1106
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Objectives

• To discuss diagnostic and therapeutic
  strategies for
• Hyponatremia
• Hypernatremia
• Hyperkalemia
• Hypokalemia

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Case 1

• 60 year old man
• Admit for weakness and hyponatremia
• Na 120 mg/dL

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Clinical Evaluation

• History
• Symptomatic?
• Predisposed?
• Medications? IVFs?
• Physical
• Volume status?
• Labs
• Confirm (if unusually abnormal)
• Context
• Additional diagnostic tests

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Case 1 (contd)

• Nausea, weak, confused x 1 week
• HTN, CHF
• JVD, crackles (rales), edema
• Na 120 mEq/L
• BUN 93 mg/dL
• Cr 3 mg/dL
• Glucose 135 mg/dL
• Albumin 2.9 mg/dL
• Plasma osm 252 mOsm/kg
• Urine osm 690 mOsm/kg

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Choose the most appropriate treatment

• 3 I.V. NaCl
• 0.9 I.V. NaCl
• 50 mg hydrochlorothiazide daily
• Salt and water restriction
• Demeclocycline

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Differential diagnosis
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Hyponatremia usually reflects excessive H20
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Common Differential Dx

• Decreased Water Excretion
• GFR
• Kidney perfusion
• SIADH

• Addisons Disease
• Malnutrition
• Pseudohyponatremia
• Psychogenic (gt1 L / hour)

100mg/dL glucose increase ? 1.6 mEq/L Na
decrease
Urine specific gravity lt 1.003
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COMMON CAUSES of HYPONATREMIA

1. History predisposing features
2. Exam volume status (including orthostatics
   supine/standing)
3. BMP Urinalysis Serum Osmolality (Urine Sodium
   Urine Osmolality)
4. Head C.T. (if symptomatic)
5. Other imaging/labs to evaluate CV, Renal,
   Endocrine systems as needed

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Complications of Treating Hyponatremia

• Delayed treatment
• Cerebral edema
• Permanent neurological injury
• Death
• Inappropriately rapid treatment
• Cerebral dehydration/demyelination
• Permanent neurological injury
• Death
• Inappropriate treatment
• Failure to improve ? morbidity
• Delayed improvement ? morbidity
• Further deterioration

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Common Treatment Options

• Water restriction
• Diuresis (with loop diuretic)
• Volume infusion (with crystalloid)
• Hypertonic saline
• Demeclocycline

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What if he had cerebral edema?

1. Correct Na to 125-130mEq/L to temporarily
   relieve edema
2. Na should NOT increase by more than 10-12
   mEq/L in 1st 24 hours
3. Slow/Stop infusion as soon as symptoms improve

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3 NaCl Calculation

• Na 116 mEq/L
• Goal Na 125 mEq/L at 24 hours
• Amount of Na to be given as 3 infusion
• Serum Na (desired) Serum Na(measured)
  (TBW)
• 125 116 (0.5)(60kg)
• 270 mEq Na
• 3 saline 513 mEq sodium/L
• 270/513 0.5 L 500 ml over 24 hrs.

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Hyponatremia Key Points

• 127 mEq/L
• Excess water
• If symptomatic, treat rapidly
• Slowly correct Na towards normal
• Find the underlying cause

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Case 2

• 40 y/o woman s/p hypertensive brain hemorrhage 2
  weeks ago.
• This morning shes less responsive.
• What may have caused this new problem?

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• Stuporous
• BP 150/70, HR 94
• Dry mouth, poor turgor
• Na 160 mEq/L K 2.8 mEq/L HCO3 18 mEq/L Cl 137
  mEq/L

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Differential diagnosis
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Hypernatremia usually reflects insufficient H20
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Differential Diagnosis

• Lack of water
• Severe diarrhea
• Severe burns
• H20 excretion
• Osmotic diuresis
• H20 conservation
• Diabetes insipidus

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Guidelines for Hypernatremia Rx

• Determine and treat likely cause(s)
• Most common error is underguesstimation of
  water deficit
• TBW x (Na(measured) Na(desired) )/Na
  (desired)
• Replace H20 enterally if possible
• Frequent monitoring

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Sodium Content of IVFs (mEq/L)

• 3 saline 513
• 0.9 (normal) saline 154
• Ringers Lactate 130
• Half Normal (0.45) saline 77
• 5 Dextrose (D5W) 0

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Hypernatremia Key Points

• Na gt145 mEq/L
• Net water loss
• Calculate the water deficit

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Case 3

• 29 y/o man with severe muscle weakness.
• No vomiting or diarrhea.
• Normal physical exam.

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• Na 141 mEq/L
• K 1.4 mEq/L
• Cl 116 mEq/L
• HCO3- 11 mEq/L
• pH 7.25, pCO2 21 mmHg

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Consequences of Hypokalemia K lt3

• Neuromuscular manifestations
• Weakness, fatigue, rhabdomyolysis, myonecrosis,
  respiratory failure
• GI symptoms
• Constipation, ileus
• Nephrogenic Diabetes Insipidus
• Dysrhythmias (if heart disease)

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Common Causes of Hypokalemia

• Malnutrition/NPO
• Diarrhea (100 mEq/L)
• Vomiting (volume depletion)
• DRUGS
• Thiazides (stimulate excretion)
• Amphotericin B
• Penicillins
• Gentamicin
• Foscarnet

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Choose the most likely diagnosis

• Bartters syndrome
• Laxative abuse
• Primary aldosteronism
• Diuretic abuse
• Distal renal tubular acidosis

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Less Common Causes

• Hormonal
• Primary hyperaldosteronism
• Adenomas, hyperplasia, ectopic ACTH, ectopic
  mineralocorticoid (licorice, chaw)
• Secondary hyperaldosteronism
• Renal hypoperfusion (CHF, RAS, severe HTN)
• Renin-secreting tumor
• Renal tubular disease
• Type 1 or 2 RTA
• Bartters syndrome (metabolic alkalosis,
  polyuria)
• Chronic magnesium depletion
• Laxative abuse (metabolic alkalosis)

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Hypokalemia Rx

• Recognize likely total body depletion
• 1 mEq/L decrease 150-400mEq total deficiency
• Gradual oral replacement
• I.V. replacement if serum level less than 3 mEq/L
  
• Check Replace magnesium
• Consider telemetry

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Hypokalemia Key Points

• K lt 3.5 review medications, review health
  status
• K lt 3 intervention
• Recognize Mg is cofactor
• Renal/CV monitoring

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Case 4

• 59 y/o man with 3-days malaise, decreased mental
  acuity and responsiveness, slurred speech.
• ESRD on hemodialysis HTN, DM, Hypothyroidism

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• Disoriented and lethargic
• BP (supine) 148/79mmHg, HR 101/min (supine) RR
  26/min, T 37.7oC.
• Mucous membranes are moist, neck veins are
  distended. Bilateral crackles and wheezes. Loud
  S4. 3 peripheral edema.

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• What is the next most appropriate step in
  managing this patient?
• Begin I.V. infusion of normal saline for volume
  repletion
• Administer 1 ampule dextrose and 10 units insulin
  I.V. for hyperkalemia
• Transfer to the ICU and perform emergent
  peritoneal dialysis
• Transfer to the ICU and perform emergent
  hemodialysis

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Dialysis machine available in 20 minutes
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Emergency Treatment K gt 6 mEq/L

• STAT ECG
• STAT repeat K
• Give IV Calcium

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Additional Rx

• More IV Calcium
• Glucose and Insulin
• Bicarbonate
• Inhaled Beta-2 agonists
• Sodium polystyrene sulfonate (Kayexalate)

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Severe hyperkalemia is usually preceded by
moderate, uncorrected hyperkalemia
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Differential Dx

• Renal Failure (GFR lt 10 ml/min)
• Extra Renal Causes
• Metabolic acidosis
• Cell lysis (chemotherapy, trauma)
• Salt substitutes, ACE-I/ARB,
• Addisons Disease
• Pseudo (coagulated RBCs/platelets)

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Hyperkalemia Key Points

• Kgt4.5 caution with medications, monitor
• Kgt5.5 intervene
• Calcium (not kayexalate) is 1st line
• Check ECG

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SUMMARY

• Construct your differential
• Know the complications of therapy
• Know the implications of lack of therapy
• Calculate water/electrolyte needs
• But repeated and frequent monitoring is most
  important.
• Electrolyte disorders may be a diagnostic clue or
  an expected consequence of therapy