1. INTERACTIVE CASE DISCUSSION
Fluid and Electrolyte Disorders
Part II

2. 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

3. 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

4. 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.

5. Fluid and Electrolytes Part II
REMEMBER !
Serum Na  Na balance
Serum Na = Water balance
Volume status = Na balance

6. Fluid and Electrolytes Part II
Question # 2: How will you approach the problem of hyponatremia?

7. HYPONATREMIA Plasma Osmolality (285-295) Normal Hyperproteinemia
Hyperlipidemia
Bladder irrigaton
Low
True Hyponatremia
High
Hyperglycemia
Mannitol
Maximally
Dilute urine
Singer, 2001

8. HYPONATREMIA Maximally dilute urine Uosm < 100 No Yes ECF Volume
Primary polydipsia
Reset osmostat
Singer, 2001

9. HYPONATREMIA ECF Volume Increased Normal Decreased CHF Cirrhosis
Renal failure
Nephrosis
Hypothyroid
Hypoadrenal
SIADH
Urine Na
Singer, 2001

10. 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

11. 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)

12. 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

13. 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

14. 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

15. 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.

16. Fluid and Electrolytes Part II
REMEMBER !
Serum Na  Na balance
Serum Na = Water balance
Volume status = Na balance

17. Fluid and Electrolytes Part II
Question # 5: Calculate the amount of water deficit in this patient.

18. 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.

19. Fluid and Electrolytes Part II
Question # 6: How will you approach the problem of hypernatremia?

20. HYPERNATREMIA ECF Volume Increased Not increased Administration of
Hypertonic NaCl and
NaHCO3
Minimum volume
of maximally
concentrated urine
(Uosm)
Singer, 2001

21. HYPERNATREMIA UOsm > 800 No Yes Urine osmolar excretion rate
Insensible H2O loss
GI H20 loss
Remote renal H2O loss
Singer, 2001

22. 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

23. 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

24. 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.

25. 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

26. 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.