FUNDAMENTALS OF FLUID AND ELECTROLYTE BALANCE

1. FUNDAMENTALS OF FLUID AND ELECTROLYTE BALANCE

3. FLUID REQUIREMENTS

4. FLUID CONTENT OF THE BODY • Varies with age, sex, adipose tissue • Females 45-50% TBW • Males 50-60% TBW • Infants 77% TBW

5. BODY FLUID COMPARTMENTS RULE OF THIRDS • Intracellular: 2/3 (40% TBW) • Extracellular: 1/3 (20% TBW) • Interstitial + Lymph: 2/3 (15% TBW) • Intravascular: 1/3 (5% TBW)

6. ELECTROLYTES IN BODY FLUID COMPARTMENTS

7. IV FLUID DISTRIBUTION IN BODY COMPARTMENTS

8. SOLUTES • Non-electrolytes • Dextrose • Urea • Creatinine • Electrolytes • Anions • Cations

9. MAINTENANCE vs. REPLACEMENT • Maintenance: • Provide normal daily requirements: Water: 2.5 L Sodium ½ or ¼ NS KCl 40-60 meq/L • Example: D5 ½ NS with KCL 20 meq/L running at 100 ml/hr

10. MAINTENANCE vs. REPLACEMENT • Replacement: • Replace abnormal losses with a fluid and electrolytes similar to that which was lost.

13. OSMOLALITY Definition: Concentration of particles (osmotically active) in solution. It is usually expressed in millosmoles of solute per kg of solution. • Osmolality is independant of valence. • Osmolality (mOsm/Kg) of dilute solutions approximate osmolarity (mOsm/L) • Plasma: 280-300 mOsm/Kg • Same in all body compartments • Water distribution

14. Normal Laboratory Values Sodium 135-145 meq/L Potassium 3.5-5.0 meq/L Chloride 95-105 meq/L Bicarbonate 22-28 meq/L Calcium 9-11 mg/dL Phosphate 3.2-4.3 mg/dL Glucose 70-110 mg/dL BUN 8-18 mg/dL Creatinine 0.6-1.2 mg/dL Osmolality (P) 280-295 mOsm/kg Osmolality (U) 50-1200 mOsm/kg

17. ELECTROLYE DISORDERSSODIUM JO is a 58 year-old male with cirrhosis of the liver due to ethanol abuse. Physical examination reveal ascites. Baseline lab is as follows: Na 128, K 3.8, Cl 95, CO2 24 JO is to be started on TPN, Should we request additional sodium to correct his hyponatremia?

18. ELECTROLYE DISORDERSSODIUM • Primary extracellular cation • Hyponatremia • Excess of TB water • Decrease in TB sodium • Isotonic hyponatremia (factitious) • Hypertonic hyponatremia (dilutional)

19. ELECTROLYTE DISORDERSHypotonic Hyponatremia

20. ELECTROLYE DISORDERSSODIUM JO is a 58 year-old male with cirrhosis of the liver due to ethanol abuse. Physical examination reveal ascites. Baseline lab is as follows: Na 128, K 3.8, Cl 95, CO2 24 JO is to be started on TPN, Should we request additional sodium to correct his hyponatremia? JO’s is in an edematous state. He has an excess of TB water and sodium. The appropriate treatment is water and sodium restriction. He should also receive diuretic treatment. The drug of choice is Aldactone (spironolactone), an aldosterone antagonist.

21. ELECTROLYE DISORDERSModel for Distribution and Elimination of Intracellular Ions Intake K Phos Mg ICF ECF Stomach Intestine Renal Losses GI (stool) Losses

22. ELECTROLYE DISORDERSPOTASSIUM • Primary intacellular cation • Hypokalemia: Causes • Decreased dietary intake • Redistribution Insulin Metabolic Alkalosis Dehydration

23. ELECTROLYE DISORDERSPOTASSIUMMetabolic Alkalosis and Hypokalemia Intracellular Fluid H+ Extracellular Fluid K+

24. ELECTROLYE DISORDERSPOTASSIUM • Hypokalemia: Causes • Increased Urinary or GI Losses Diuretics NG Suction Diarrhea

25. ELECTROLYE DISORDERSPOTASSIUM Drugs which may cause hypokalemia Urinary wasting: aminoglycosides, amphotericin B, corticosteroids, diuretics, levodopa, nifedipine, penicillins, rifampin Gastrointestinal losses: laxatives Redistribution: Beta-2 agonists, lithium

26. ELECTROLYE DISORDERSPOTASSIUM • Hypokalemia: Treatment/Estimation of Deficit If serum K > 3meq/L: 100-200 meq required per each change in serum K of 1 meq/L If serum K < 3 meq/L: 200-400 meq required per each change in serum K of 1 meq/L

27. ELECTROLYE DISORDERSPOTASSIUM • Hypokalemia: Estimation of Deficit If serum K > 3meq/L: 100-200 meq required per each change in serum K of 1 meq/L If serum K < 3 meq/L: 200-400 meq required per each change in serum K of 1 meq/L Example: Serum K = 2.5 How much K is required to correct serum K to 4.0? Step 1 To increase from 2.5 to 3.0: 200-400 meq X 0.5=100-200meq Step 2 To increase from 3.0 to 4.0: 100-200 meq X 1.0=100-200meqTo Total=200-400meq

28. ELECTROLYE DISORDERSPOTASSIUM Hypokalemia: Treatment

29. ELECTROLYE DISORDERSPOTASSIUM Mrs D. is a 62 year-old female who is having an acute exacerbation of Crohn’s disease. She complains to you of severe and frequent diarrhea over the last four days. She experiences dizziness when she stands. Your physical examination reveals dry mucous membranes. In the supine position her BP=110/65 and in the upright position her BP=90/45 and her pulse=140. Your lab values are as follows: Na 132, K 2.9, Cl 92, CO231, BUN 25, Cr 1.0 Discuss Mrs. D’s fluid and electrolyte problems.

30. ELECTROLYE DISORDERSCase Study: Hypokalemia Mrs D. is a 62 year-old female who is having an acute exacerbation of Crohn’s disease. She complains to you of severe and frequent diarrhea over the last four days. She experiences dizziness when she stands. Your physical examination reveals dry mucous membranes. In the supine position her BP=110/65 and in the upright position her BP=90/45 and her pulse=140. Your lab values are as follows: Na 132, K 2.9, Cl 92, CO2 31, BUN 25, Cr 1.0 Mrs D’s has extracellular volume depletion due to prolonged diarrhea. The ECVD is supported by her physical assessment and postural hypotension and her BUN/Cr is > 20:1. The diarrhea has resulted in a loss of fluid and sodium chloride. Some potassium was lost directly in the stools, but the main cause of her hypokalemia is her ECVD which has induced a metabolic alkalosis (contraction alkalosis.) The alkalosis contributed to her hypokalemia by two mechanisms. Some potassium has moved to the intracellular compartment but much of it has been lost in the urine where potassium wasting occurs secondary to chloride deficit. Administration of Normal Saline with Potassium Chloride will correct her fluid and electrolyte problems (and alkalosis.)

31. ELECTROLYE DISORDERSPOTASSIUM • Hyperkalemia: Causes • Decreased Renal Excretion CRF and ARF Drug induced: K-sparing diuretics (spironolactone, triamterine, amiloride) Angiotensin converting enzyme inhibitors NSAIDS

32. ELECTROLYE DISORDERSPOTASSIUM • Hyperkalemia: Causes • Redistribution Trauma, burns Acidosis Hyperosmolar states • Increased intake Salt substitutes Blood transfusions K salts of antibiotics

33. ELECTROLYE DISORDERSPOTASSIUMMetabolic Acidosis and Hyperkalemia Intracellular Fluid K+ Extracellular Fluid H+

34. ELECTROLYE DISORDERSPOTASSIUM • Hyperkalemia: Treatment • Potassium Antagonist Calcium Chloride • Redistribution • Insulin + dextrose • Sodium bicarbonate • Cationic binding resins Kayexalate (polystyrene sulfonate) • Renal Elimination/dialysis

35. ELECTROLYE DISORDERSMAGNESIUM • Hypomagnesemia: Causes • Decreased Intake Malnutrition Alcoholism • Decreased Absorption • Increased Losses GI losses Renal losses

36. ELECTROLYE DISORDERSMAGNESIUM • Drug Induced Hypomagnesemia • GI Losses Laxatives • Renal Losses Diuretics, cisplatin, aminoglycosides, amphotericin B

37. ELECTROLYE DISORDERSMAGNESIUM • Hypomagnesemia: Treatment • IV Magnesium Sulfate Replace over several days Renal threshold for reabsorption of Mg 1 mEq/kg on day 1 0.5 mEq/kg on days x 3-5 days • Oral replacement Mylanta

38. ELECTROLYE DISORDERSMAGNESIUM • Hypermagnesemia: Causes • Exogenous ingestion • Impaired renal excretion • Treatment: Eliminate exogenous source of Mg

39. ELECTROLYE DISORDERSPHOSPHOROUS • Hypophosphatmeia: Causes • Impaired absorption Aluminum or calcium binding • Redistribution Respiratory alkalosis Glucose + insulin • Increased Excretion

40. ELECTROLYE DISORDERSPHOSPHOROUS • Hyperphosphatmeia: Causes • Renal impairment • Increased intake • Treatment Phosphate binders: Alternagel, Amphojel, Calcium Suppliments

41. ELECTROLYE DISORDERSPHOSPHOROUS M.T. is a 55 year-old female with a history of chronic renal failure who is admitted to the SICU following a motor vehicle accident. She is started on a TPN solution with minimal K, no Mg and no Phos. She also receives Mylanta II 30 ml per NG tube every four hours. Although her baseline labs were normal on day six her labs are as follows: K 4.3, Mg 2.6, Phos 1.6 • What role did the antacid play in her electrolyte abnormalities? • What role did the TPN play?

42. ELECTROLYE DISORDERSPHOSPHOROUS M.T. is a 55 year-old female with a history of chronic renal failure who is admitted to the SICU following a motor vehicle accident. She is started on a TPN solution with minimal K, no Mg and no Phos. She also receives Mylanta II 30 ml per NG tube every four hours. Although her basline labs were normal on day six her labs are as follows: K 4.3, Mg 2.6, Phos 1.6 M.T’s K is normal, but she has hypermagnesemia and hypophosphatemia. The antacid contributed to both of these abnormalities. It provided a significant source of Mg this patient with impaired excretion. Also the aluminum in the antacid acted a phosphate binder contributing to the hypophosphatemia. The TPN could have contributed to the hypophosphatemia by inducing an intracellular shift of phosphate (refeeding.) The potassium probably remained normal because some was being provided. Mg was being provided enterally.