Approach to the patient with
electrolyte disorders
Hyponatremia-Hypernatremia
Zehra Eren, M.D.
LEARNING OBJECTIVES
• recall body water and fluid distribution
• recall serum osmolality
• recall etiology of hyponatremia and hypernatremia
• describe sing and symptoms of hyponatremia and
hypernatremia
• describe laboratory findings of hyponatremia and
hypernatremia
• explane treatment of hyponatremia and
hypernatremia
Solute Composition of Body Water
• Predominant solutes in ECF:
Sodium (Na+)
Chloride (Cl−)
Bicarbonate (HCO3−)
• Predominant solutes in ICF:
Potassium (K+)
Protein−
Phosphate−
Osmolality
• Posm=2×plasma Na+ +
Glucose/18 + BUN/2.8
Osmolality
• Normal ECF osmolality: 280-290mOsm/kgH2O
• ECF and ICF are in osmotic equilibrium, at
steady state
• Vasopressin (antidiuretic hormone (ADH)
-osmotic stumuli
-nonosmotic stumuli: HF, Cirrhosis, vomiting,
postoperative pain, pregnancy
Hyponatremia
• Serum Na <135 mEq/L
European Society of Intensive Care Medicine (ESICM)
European Society of Endocrinology(ESE)
European Renal Association – European Dialysis and Transplant
Association (ERA–EDTA)
Hyponatremia
• Serum Na <135 mEq/L
Hyponatremia is a disorder of water balance
Dısorders of water and sodium balance
• Hyponatremia (too much water)
• Hypernatremia (too little water)
• Hypovolemia (too little sodium, the main
extracellular solute)
• Edema (too much sodium with associated
water retention)
Hyponatremia
• almost always due to the oral or intravenous
intake of water that cannot be completely
excreted
• impaired water excretion that is most often
due to an inability to suppress the release of
antidiuretic hormone (ADH) or to advanced
renal failure
Diagnosis
• Volume status and serum osmolality are
essential to determine etiology
• Hyponatremia usually reflects excess water
retention relative to sodium rather than sodium
deficiency, the sodium concentration is not a
measure of total body sodium
• Hypotonic fluids commonly cause hyponatremia
in hospitalized patients
Differences between SIADH and
cerebral salt wasting
Sherlock M, O’Sullivan E, et all. The incidence and pathophysiology of hyponatraemia after
subarachnoid haemorrhage. Clinical Endocrinology; 2006, 64: 250–254
6.3. Which parameters to be used for differentiating
causes of hypotonic hyponatraemia?
Clinical practice guideline on
diagnosis and treatment of
hyponatraemia; Nephrol Dial
Transplant (2014) 0: 1–39
Symptoms and Sing of Hyponatremia
• symptoms depends on severity and acuity
hyponatremia
• the symptoms reflect neurologic dysfunction
induced by cerebral edema and possible adaptive
responses of brain cels to osmotic swelling
• Nausea, malaise, headache, lethargy, seizures,
coma, respiratory arrest
• the physical examination should help categorize
the patient's volume status into hypovolemia,
euvolemia, or hypervolemia.
Classification of symptoms of hyponatraemia
Clinical practice guideline on diagnosis and treatment of
hyponatraemia; Nephrol Dial Transplant (2014) 0: 1–39
Adaptation of the brain to hypotonicity
Adrogue HJ & Madias NE. Hyponatremia. NEJM; 2000 342 1581–1589
Complications of hyponatraemia
Hyponatraemia with severe symptoms
7.2. Hyponatraemia with moderately
severe symptoms
7.3. Acute hyponatraemia without severe
or moderately severe symptoms
7.4. Chronic hyponatraemia without
severe or moderately severe symptoms
7.4. Chronic hyponatraemia without
severe or moderately severe symptoms
7.4. Chronic hyponatraemia without
severe or moderately severe symptoms
Na+ deficit ≈
body weight X 0.6 X
(desired plasma Na+ concentration –
plasma Na+ concentration)
1mg/dl/ h
10-12mg/dl /24h
Hypernatremia
• Serum Na>145 mEq/L
Symptoms and Sings of Hypernatremia
• Dehydrated patient → orthostatic hypotension
and oliguria
• Rise in plasma Na and osmolality
→water movement out of the brain
→rupture of the cerebral veins
→focal intracerebral and subarachnoidal hemorrages
→possible irreversible neurologic damage
• Lethargy, weaknees, irritability, twitching, seuzures,
coma
• Osmotic demyelination (uncommon)
Laboratory Findings
• Urine osmolality > 400 mosm/kg → renal
water-conserving ability is functioning (hypotonic
fluid losses from excessive sweating, the respiratory tract, or bowel
movements and lactulose)
• Urine osmolality < 250 mosm/kg →
characteristic of DI
-Central DI: inadequate ADH release
-Nephrogenic DI: renal insensitivity to ADH
(lithium, demeclocycline, relief of urinary obstruction, interstitial nephritis,
hypercalcemia, and hypokalemia)
• Water deficit ≈
body weight X 0.6 X
(plasma Na concentration/
desired plasma Na concentration) - 1
Case 1
• A 72-year-old woman from a nursing home presents to the
emergency department with a change in her mental state
over the past few hours. She has a medical history of
coronary artery disease and hypertension.
• Her medications include hydrochlorothiazide: 25 mg a
day, and aspirin, 80 mg a day.
• On physical examination, she has decreased skin turgor,
orthostatic hypotension, and disorientation to time, place,
and person without focal neurologic deficits.
• Initial laboratory tests show a serum sodium level of 110
mmol/L;blood urea nitrogen 65 mg/dL; creatinine
3.6mg/dL and plasma osmolality, 278 mOsm/kg of water.
• Her serum sodium level 2 months before admission was
135 mmol/L, and her urine output was 400 mL a day.
Case2
• A 82-year-old women with Dementia, HTN and DM is
admitted for work-up of hyponatremia. Her sodium has
been 118 for the last 4 days.
• She is taking Paxil for depression and she is not on any
diuretics.
Case 3
• A 85 year-old male presents to the emergency room with
pneumonia. He has been febrile for several days and has
had a cough productive of yellow sputum.
• On physical exam he is a well-developed, thin male in
moderate respiratory distress. Blood pressure (supine)
120/86, pulse 74, blood pressure 115/85, pulse 70,
respirations 24. Temperature was 39oC. Body weight 60 kg.
Cardiopulmonary exam demonstrated decreased breath
sounds at the base of the right lung.
• Sodium 120 mmol/L, Potassium 3.9, BUN 10 mg/dl ,
Creatinine 0.8 mg/dl, U Osmolality 500
mosm/kg, Glucose 90 70-110 mg/dl
• Urine Sodium 60 mmol/L,Potassium 30 mmol/L,
Case4
• A 60 year-old male with alcoholic cirrhosis presents to your
office because of worsening edema.
• On physical exam the patient is a well-developed, poorly
nourished, jaundiced male in mild distress due to his
anasarca. Blood pressure (supine) 110/75, pulse 100,
(standing) 90/60, pulse 120, respirations 23 and he was
afebrile. Body weight 80 kg. Cardiopulmonary exam was
unremarkable. The abdomen was remarkable for tense
ascites and a shrunken liver. Lower extremities had 3+
pitting edema.
• Sodium 127 mmol/L, Potassium 3.63mmol/L, BUN 35
mg/dl, Creatinine 1.8 mg/dl, Glucose 105 mg/dl
• Urine Sodium 6 mmol/L
Osmolality 600 mosm/kg