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 > 15mmol/d Metabolic acidosis Metabolic alkalosis Lower GI K loss 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 Yes Vomiting Barrter’s syndrome Diuretic abuse Hypomagnesemia 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? Barrter’s syndrome Diarrhea Hypomagnesemia 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 > 10 TTKG < 5 (increased distal flow) TTKG < 5 Response to 9fluodrocortisone Low protein diet  Effective circulating volume Singer, 2001

HYPERKALEMIA Response to 9-fluodrocortisone TTKG  10 TTKG < 10 Primary or Secondary hypoaldosteronism BP  renin & aldosterone BP  renin & aldosterone Measure renin & aldosterone Pseudohypoaldosteronism K-sparing diuretics Trimethoprim Pentamidine Gordon’s syndrome Cyclosporine 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? Hypoaldosteronism K - sparing diuretics (Spironolactone) Low protein intake 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.