Download Fluid & electrolyte Disorders Part 2

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 balance
Serum 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?
HYPOKALEMIA
Urinary K excretion
<15 mmol/d
Metabolic acidosis
Lower GI K loss
> 15mmol/d
Metabolic alkalosis
Remote diuretic use
Remote vomiting
K loss via sweating
Singer, 2001
HYPOKALEMIA
Urine K excretion
> 15 mmol/d
TTKG > 4
TTKG < 2
Na wasting nephropathy
Osmotic diuresis
Diuretic
Singer, 2001
HYPOKALEMIA
TTKG > 4
Metabolic alkalosis
Metabolic acidosis
Hypertension
DKA
RTA
Ampho B
No
Vomiting
Barrter’s syndrome
Diuretic abuse
Hypomagnesemia
Yes
Mineralocorticoid excess
Liddle’s syndrome
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 syndrome
B. Diarrhea
C. Hypomagnesemia
D. 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 pseudohyperkalemia
Exclude transcellular K shift
Exclude oliguric renal failure
Stop NSAIDs and ACE-inhibitors
Assess K excretion
Singer, 2001
HYPERKALEMIA
Assess K excretion
TTKG < 5
Response to
9fluodrocortisone
TTKG > 10
(increased distal flow)
Low protein diet
 Effective circulating volume
Singer, 2001
HYPERKALEMIA
Response to 9-fluodrocortisone
TTKG  10
TTKG < 10
Primary or
Secondary
hypoaldosteronism
Measure
renin
& aldosterone
BP
 renin &
aldosterone
BP
 renin &
aldosterone
Pseudohypoaldosteronism
K-sparing diuretics
Gordon’s syndrome
Trimethoprim
Cyclosporine
Pentamidine
RTA (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.