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INTERACTIVE CASE DISCUSSION
Fluid and Electrolyte Disorders Part II
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Fluid and Electrolytes Part II
CASE # 1: 60 y/o male with ischemic cardiomyopathy and CHF. Admitted because of orthopnea. 150/60, HR=120/min, RR = 38/min JVP = 20 (); bibasal inspiratory crackles S3 gallop; ascites; pedal edema Na = 125meq/L () Posm = 270 mosm/kg () Uosm = 500 mosm/kg
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Fluid and Electrolytes Part II
Question # 1: Describe the patient’s fluid and electrolyte status. Na deficit, water deficit Na deficit, water excess Na excess, water deficit Na excess,water excess
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Fluid and Electrolytes Part II
Answer #1: Na excess, water excess Hyponatremic (Na=125) hence he has water excess. Hypervolemia on physical examination ( BP, JVP,crackles, ascites, edema ) hence he has Na excess.
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Fluid and Electrolytes Part II
REMEMBER ! Serum Na Na balance Serum Na = Water balance Volume status = Na balance
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Fluid and Electrolytes Part II
Question # 2: How will you approach the problem of hyponatremia?
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HYPONATREMIA Plasma Osmolality (285-295) Normal Hyperproteinemia
Hyperlipidemia Bladder irrigaton Low True Hyponatremia High Hyperglycemia Mannitol Maximally Dilute urine Singer, 2001
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HYPONATREMIA Maximally dilute urine Uosm < 100 No Yes ECF Volume
Primary polydipsia Reset osmostat Singer, 2001
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HYPONATREMIA ECF Volume Increased Normal Decreased CHF Cirrhosis
Renal failure Nephrosis Hypothyroid Hypoadrenal SIADH Urine Na Singer, 2001
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HYPONATREMIA Urine Na UNa < 10 meq/L UNa > 20 meq/L
Na wasting nephropathy Hypoaldosteronism Diuretics Vomiting Extrarenal Na loss Remote diuretics Remote vomiting Singer, 2001
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Fluid and Electrolytes Part II
Question # 3: What is the most likely cause of hyponatremia in this patient? Congestive heart failure Diuretics Hypothyroidism Syndrome of Inappropriate ADH secretion (SIADH)
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Fluid and Electrolytes Part II
Answer # 3: Congestive heart failure Low Posm excludes pseudohypoNa. Uosm > 100 (500) hence not primary polydipsia or reset osmostat Volume status increased (Na excess) Compatible with CHF
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Fluid and Electrolytes Part II
CASE # 2: 30 y/o 70kg male suffered a skull fracture due to MVA. 86/60,HR=110/min. JVP = 4, poor skin turgor Dry mucosa, no edema Na = 168 meq/L Posm = 350mosm/kg; Uosm = 80mosm/kg 24 hr urine output = 4 liters
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Fluid and Electrolytes Part II
Question # 4: Describe the patient’s fluid and electrolyte status. Na deficit, water deficit Na deficit, water excess Na excess, water deficit Na excess, water excess
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Fluid and Electrolytes Part II
Answer # 4: Na deficit, water deficit Hypernatremic ( Na = 168) hence he has water deficit. Hypovolemic on physical examination ( BP, JVP,poor skin turgor, drymucosa) hence he has Na deficit.
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Fluid and Electrolytes Part II
REMEMBER ! Serum Na Na balance Serum Na = Water balance Volume status = Na balance
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Fluid and Electrolytes Part II
Question # 5: Calculate the amount of water deficit in this patient.
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Fluid and Electrolytes Part II
Answer # 5: 7 liters Water deficit = Plasma Na – 140/140 X ( 0.5 X BW ) = 168 – 140/140 X ( 0.5 X 70 ) = 7 liters.
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Fluid and Electrolytes Part II
Question # 6: How will you approach the problem of hypernatremia?
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HYPERNATREMIA ECF Volume Increased Not increased Administration of
Hypertonic NaCl and NaHCO3 Minimum volume of maximally concentrated urine (Uosm) Singer, 2001
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HYPERNATREMIA UOsm > 800 No Yes Urine osmolar excretion rate
Insensible H2O loss GI H20 loss Remote renal H2O loss Singer, 2001
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HYPERNATREMIA Urine osmolar excretion rate > 750 mosm/day No Yes
Renal response to desmopressin Osmotic diuresis Diuretic UOsm Uosm no Central DI Nephrogenic DI Singer, 2001
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Fluid and Electrolytes Part II
Question # 7: What is the most likely cause of the patient’s hyperNa? Diabetes insipidus GI water losses IV hypertonic NaCl Osmotic diuresis
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Fluid and Electrolytes Part II
Answer # 7: Diabetes insipidus Not hypervolemic hence not IV hypertonic NaCl. Uosm < 100 (dilute) hence not extrarenal water losses (GI losses). Urine osmolar excretion rate = Uosm X U volume; 80mosm/kg x 4 liters/d = 320 mosm/d (< 750mosm/d); hence not osmotic diuresis.
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Fluid and Electrolytes Part II
Question # 8: The patient was given a dose of desmopressin (ADH analog). The Uosm after the dose is 800 mosm/kg. What is the cause of the diabetes insipidus? Central diabetes insipidus Nephrogenic diabetes insipidus
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Fluid and Electrolytes Part II
Answer # 8: Central DI The Uosm increased after the desmopressin dose. The Uosm will not change even after repeated desmopressin doses in patients with nephrogenic DI.
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