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INTERACTIVE CASE DISCUSSION
Fluid and Electrolyte Disorders
Part I
Introduction to Fluids and Electrolytes
Fluid & Electrolyte Status Assessment
• Sodium (Na) balance
• Potassium (K) balance
• Water balance
• Other ions: Ca, Mg, Phosphate, etc.
Introduction to Fluids and Electrolytes
Fluid & Electrolyte Status Assessment
• “Hypo” – deficit
• “Hyper” – excess
• “Eu” or “Normo” - normal; adequate
Introduction to Fluids and Electrolytes
Assessment of Potassium (K) Balance
• Measuring tool: serum K
• K = 3.5 - 5meq/L
• Hypokalemia: < 3.5 meq/L
• Normokalemia: 3.5 – 5meq/L
• Hyperkalemia: > 5meq/L
Introduction to Fluids and Electrolytes
Assessment of Water Balance• Measuring tool: serum Na• Hypernatremia ( >145 meq/L): water
deficit• Normonatremia ( 135-145 meq/L):
normal water balance• Hyponatremia ( <135 meq/L): water
excess
Introduction to Fluids and Electrolytes
Assessment of Sodium (Na) Balance• Measuring tool: Physical examination of
the patient’s volume status• Hypervolemia: Na excess; BP, JVP,
edema, ascites, effusion etc.• Normovolemia: normal Na balance; normal
BP, JVP = 8-12; good skin turgor• Hypovolemia: Na deficit; BP, JVP, dry
mucosa, poor skin turgor etc.
Introduction to Fluids and Electrolytes
REMEMBER !
Serum K = K balanceSerum Na Na balance
Serum Na = Water balance
Volume status = Na balance
Introduction to Fluids and Electrolytes
Sample Question: A 50 year old male with chronic renal failure has a serum K of 6 meq/L. What is his K status?
Introduction to Fluids and Electrolytes
Answer:
• Normal serum K = 3.5- 5meq/L
• Serum K = 6meq/L ( > 5 meq/L)
• Hyperkalemia
• K excess
Fluids and Electrolytes Part I
CASE #1: A 45 year old Japanese tourist collapsed in a shopping mall and was brought to the ER.
• 90/60, HR = 110/min
• JVP = 4, proximal muscle weakness
• Labs: Na = 140, Cl = 110, HCO3 = 16, K = 2.
Fluids and Electrolytes Part I
Question #1: How will you approach the problem of hypokalemia?
HYPOKALEMIAUrinary K excretion
<15 mmol/d > 15mmol/d
Metabolic acidosis Metabolic alkalosis
Lower GI K loss Remote diuretic useRemote vomitingK loss via sweating
Singer, 2001
HYPOKALEMIA
Urine K excretion
> 15 mmol/d
TTKG > 4 TTKG < 2
Na wasting nephropathyOsmotic diuresisDiuretic
Singer, 2001
HYPOKALEMIATTKG > 4
Metabolic acidosisMetabolic alkalosis
DKARTAAmpho B
Hypertension
YesNo
Mineralocorticoid excessLiddle’s syndrome
VomitingBarrter’s syndromeDiuretic abuseHypomagnesemia
Singer, 2001
Fluids and Electrolytes Part I
Question #2: What test will you order next in order to work-up the cause of the hypokalemia?
Fluids and Electrolytes Part I
Answer #2: 24-hour urine collection to measure 24-hour urinary K excretion.
Fluids and Electrolytes Part I
Question #3: The 24-hour urinary K excretion rate is 10 mmol/day. Which of the following is the most likely cause of hypokalemia?
A. Barrter’s syndromeB. DiarrheaC. HypomagnesemiaD. Liddle’s syndrome
Fluids and Electrolytes Part I
Answer #3: Diarrhea• The 24-hour urine K excretion is less than 15
mmol/day.• Rest of the choices are renal K-wasting states
wherein the 24-hour urine K excretion should be > 15mmol/d.
• The patient later admitted thru an interpreter that he ate fishballs from a sidewalk vendor 2 days ago and has been having diarrhea since then.
Fluids and Electrolytes Part I
Case # 4: 38 y/o male alcoholic with cirrhosis. Admitted bec. of anorexia and cachexia. He is not on any medications.
• BP = 90/60, HR = 105/min• ABGs: pH= 7.42, pCO2 = 35, HCO3 = 22 • Creatinine = 0.7 mg/dl (normal)• Urea = 8 mg/dl ()• K = 6 meq/L ()
Fluids and Electrolytes Part I
Question #4:How will you approach the problem of hyperkalemia in this patient?
HYPERKALEMIA
Exclude pseudohyperkalemiaExclude transcellular K shiftExclude oliguric renal failureStop NSAIDs and ACE-inhibitors
Assess K excretion
Singer, 2001
HYPERKALEMIA
Assess K excretion
TTKG < 5 TTKG > 10(increased distal flow)
Response to 9fluodrocortisone
Low protein diet Effective circulating volume
Singer, 2001
HYPERKALEMIAResponse to 9-fluodrocortisone
TTKG 10 TTKG < 10
Primary or Secondaryhypoaldosteronism
BP renin & aldosterone
BP renin &aldosterone
Measure renin& aldosterone
PseudohypoaldosteronismK-sparing diureticsTrimethoprimPentamidine
Gordon’s syndromeCyclosporineRTA (IV)
Singer,2001
Fluids and Electrolytes Part I
Question #5: What is the next test to order in order to work-up the cause of this patient’s hyperkalemia?
Fluids and Electrolytes Part I
Answer #5: Compute for the Transtubular K Gradient (TTKG).
TTKG = Uk/Pk Uosm/Posm
Uk = Urine K
Pk = Plasma K
Uosm = Urine osmolality
Posm = Plasma osmolality
Fluids and Electrolytes Part I
TTKG (Transtubular K Gradient):
• In hyperkalemia:
< 5, diminished aldosterone effect
10, normal aldosterone effect,
non-renal hyperkalemia
Fluids and Electrolytes Part I
Question #6: The urine and plasma values are as follows:
Pk = 6 meq/L
Uk = 54 meq/L
Posm = 280 mmosm/kg
Uosm = 260 mmosm/kg
Compute for the TTKG.
Fluids and Electrolytes Part I
Answer #6: TTKG = 10
TTKG = Uk/Pk Posm/Uosm
= 54/6 280/260
= 9/0.9
= 10
Fluids and Electrolytes Part I
Question #7: What is the most likely cause of the patient’s hyperkalemia?
A. Hypoaldosteronism
B. K - sparing diuretics (Spironolactone)
C. Low protein intake
D. Renal tubular acidosis (RTA)
Fluids and Electrolytes Part I
Answer # 7: Low protein intake• TTKG 10 means normal aldosterone
effect (not hypoaldosteronism)• In the rest of the choices, the TTKG should
be < 5.• Patient is likely to have a low food intake
(history of anorexia, low serum urea) due to his alcoholism.