INTERACTIVE CASE DISCUSSION Fluid and Electrolyte Disorders Part I.

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.