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Correction Made Easy 

Correction Made Easy . By Adrian Paul J. Rabe, MD. Clinically Relevant Electrolytes. H 2 O – intracellular Na – extracellular K – intracellular Ca – intracellular Mg – intracellular. Water. ICF: 55-75% ECF: 25-45% Intravascular: Extravascular (1:3) Total Body Water

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Correction Made Easy 

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  1. Correction Made Easy  By Adrian Paul J. Rabe, MD

  2. Clinically Relevant Electrolytes • H2O – intracellular • Na – extracellular • K – intracellular • Ca – intracellular • Mg – intracellular

  3. Water • ICF: 55-75% • ECF: 25-45% • Intravascular: Extravascular (1:3) • Total Body Water • 60% of Body weight (men) • 50% of Body weight (women, elderly) • Osmolar Loss vs Free Water Loss • Plasma osmolality = 275-290 mosm/kg • 2(Na+K) + BUN/2.8 + Glucose/18 • Na is the major determinant of osmolality • Posm = 2(Na+K) + BUN/2.8 + Glucose/18 • Free water deficit (L) = TBW x ([Actual Na/140]-1)

  4. Water: Exercise • 55/F with diarrhea • Poor skin turgor, thirst • 45 kg • Is there water loss? • Is it osmolar loss or free water loss? • Posm = 346 mOsm/kg • Free water deficit = 4.34 L

  5. Na: Low Posm High N Low Urine output Maximal Non-maximal Hyperglycemia Mannitol Hyperproteinemia Hyperlipidemia Bladder irrigation Primary Polydipsia Reset osmostat ECF Volume Corrected Na (mg/dL) = Na + ((Gluc – 100)/100) if Gluc > 100

  6. Na: Low ECF Inc N Dec Urine Na > 20 mmol/L < 10 mmol/L SIADH Hypothyroidism Adrenal Insufficiency Heart Failure Hepatic Cirrhosis Nephrotic Syndrome Renal Insufficiency Na-wasting Nephropathy Hypoaldosteronism Diuretics Vomiting Extra-renal Na loss Remote diuretic use Remote vomiting

  7. Na: Low • Goals • Restrict water intake • Promote water loss • Correct underlying disorder • ECF volume increased • Isotonic saline: removes stimulus for AVP release • Water restriction to less than urine output • Loop diuretics • ECF volume N • Dietary water restriction

  8. Na: Low • ECF volume decreased or symptomatic hyponatremia • Correct! • Na deficit = TBW X (Desired – Actual Na) • Liters per day = (Na def)/(Infusate Na) • Osmotic Demyelination Syndrome – neurologic disorder with flaccid paralysis, dysarthria and dysphagia

  9. Na: Low • ECF volume decreased or symptomatic hyponatremia • Correct! • Na deficit = TBW X (Desired – Actual Na) • Liters per day = (Na def)/(Infusate Na) • But… correct at 10-12 mmol/L per day (e.g. correct from Na 100 to 110-112) • In a 50 kg female = 12 x TBW = 12 x 25 = 300

  10. Hyponatremia: Exercise • 65/M hypertensive patient • Deterioration in sensorium • 60 kg, xerosis, dry armpits • Na corrected = 111.2 • Posm = 242.6 mOsm/kg • ECF: decreased • Na def: 900 • Daily Correction: 360

  11. Na: High ECF Increased Not increased Urine output Minimal Non-minimal Give hypertonic solutions (hypertonic NaCl or NaHCO3) Water losses (GI, insensible, remote renal) Urine Osmolality Uosm = 2 (Na + K) + BUN + RBS

  12. Na: High Uosm > 750 < 750 DDAVP response Uosm increase Uosm decrease Diuretics Osmotic Diuresis Nephrogenic DI Central DI

  13. Na: High • Goals • Stop ongoing water loss • Correct water deficit • Safest is oral correction • D5W or pNSS are alternative solutions • Water deficit = ([Actual Na/140]-1)x TBW • Change in serum Na/L = (infusate Na-serum Na) (TBW + 1) • -12/H2O def = (infusate Na-serum Na) (TBW + 1) • (-12/H2O def)(TBW +1) = infusate Na – serum Na • Infusate Na = (-12/H2O def)(TBW +1) +serum Na • -12(TBW +1)/(Infusate Na-serum Na) = Liters

  14. Na: High • Goals • Stop ongoing water loss • Correct water deficit • Safest is oral correction • D5W or pNSS are alternative solutions • Water deficit = ([Actual Na/140]-1)x TBW • Change in serum Na/L = (infusate Na-serum Na) (TBW + 1) • Na 162 in a 40 y/o 50 kg female • Deficit: 3.93 L = 4 cycles • -12/4 = (x-162)/(TBW+1) • -3(25+1) + 162 = x • -78+162 = 84

  15. Hypernatremia: Exercise • 21/M with vomiting • 60 kg, dry buccal mucosa, UO 30cc/3h • Na corrected = 182.4 • Posm = 388.6 • Free H20 deficit = 10.9L • ECF: decreased • UO: minimal • Given infusate pLR: 8L/day for 3 days, 4L/day on the 4th day

  16. K: Low Urine K excretion > 15 mmol/d < 15 mmol/d Acid-base? TTKG? (Urine K/Plasma K) (Uosm /Posm) Acidosis Alkalosis TTKG < 2 TTKG > 4 Remote diuretic use Remote vomiting Sweat losses Lower GI K loss Na wasting nephropathy Osmotic diuresis Diuretic Acid-base Acidosis Alkalosis DKA RTA Amphotericin B Vomiting Bartter’s/Liddle’s Hypomagnesemia

  17. K: Low • Goals • Correct deficit • Minimize losses • K deficit = (Desired – actual)/0.27 – academic only • K depletion DOES NOT correlate well with plasma K • For every decrement in serum K mmol = 200-400 mmol deficit • If ~3.0 to correct to 4.0, give 200-400 mEqs of K • < 3.0 = >600 mmol

  18. K: Low • Oral correction • Bananas, fruits • Oral KCL = 40 mEqs/30 cc • IV correction (ideally, in saline) • 60 mEqs if via central line • 40 mEqs if via peripheral line • Not more than 20 mmol/h unless with paralysis or malignant ventricular arrhythmias

  19. K: High • Goals • Depends on ECG and weakness • Measures • Ca gluconate 10% in 10 mL over 2-3 minutes • NaHCO3 3 vials in saline solution • Glucose-Insulin solution • B-adrenergic drugs • Diuretics • Dialysis

  20. Ca: High • Goals • Rule out hyperalbuminemia as a cause • Corrected Ca = (40-alb) x 0.02 + Ca • Take intact PTH • Measures • Forced saline diuresis (e.g. Furosemide 200 mg + pNSS 1L x 6 hours) • Bisphosphonates (Pamidronate 60-90 mg IV x 2-4 hours) • Calcitonin • Phosphate IV • Glucocorticoids – decrease Vit D production • Dialysis

  21. Ca: Low • Goals • Rule out hypoalbuminemia as a cause • Corrected Ca = (40-alb) x 0.02 + Ca • Take intact PTH • Measures • Ca gluconate 10% solution 10 mL + D5 50 cc x 5min • Ca gluconate drip • Ca CO3 500 mg BID with meals • Vit D 2 ug/day

  22. Mg: Low • Goals • Correct K concentration • Correct Ca concentration • Measures • 1g = 0.10 increase in Mg • MgSO4 3 g in D5W 250 cc x 240 = increase by 0.3

  23. 11 Equations to memorize! • Posm = 2(Na+K) + BUN/2.8 + Glucose/18 • Uosm = 2 (Na + K) + BUN/2.8 + Glucose/18 • Corrected Na (mg/dL) = Na + ((Gluc – 100)/100) for Gluc > 100 • Na deficit = TBW X (Desired – Actual Na) • Liters per day = (Na def x 1000)/(Infusate Na) • Water deficit = ([Actual Na/140]-1) x TBW • Change in serum Na/L = (infusate Na-serum Na) (TBW + 1) • TTKG = (Urine K/Plasma K)/(Uosm /Posm) • K deficit = (Desired – actual)/0.27 • Corrected Ca = (40-alb) x 0.02 + Ca • Creatinine Clearance = [(140-age) x weight in kg] x 88.4; multiply by 0.85 for females • [72 x Creatinine in umol] • BUN:Creatinine Ratio = (BUN/Crea) in umol x 247 • *TBW fraction: 0.6 in males, 0.5 in females and elderly

  24. Before starting any calculation • Correct everything (Na, Calcium) • Get TBW • Get BUN:Crea ratio and Creatinine Clearance • Get Plasma Osmolality

  25. Exercises • 49 y/o female diabetic • 45 kg • Vomiting, decreased sensorium • Dry buccal mucosa, drowsy • BUN 13.6, Crea 223, Na 168, K 2.2, Cl 110, Mg 0.55, Ca 1.24, alb 23, RBS 21.3 • TBW: 22.5 • Creatinine Clearance: 19 • BUN:Crea Ratio: 15 • Corrected Na: 170.8 • Corrected Calcium: 1.58 • Plasma Osmolality: 380.9 (high)

  26. Exercises • 49 y/o female diabetic • 45 kg • Vomiting, decreased sensorium • Dry buccal mucosa, drowsy • BUN 5.6, Crea 223, Na 168, K 2.2, Cl 110, Mg 0.55, Ca 1.24, alb 23, RBS 21.3 • Hypernatremia • Free water deficit: 4.95 L • Change in Na for 1L pLR: -1.74 • Daily: ~7L for 2 days then 3.5 L for the 3rd day • Hypokalemia: > 600 mEqs correction • Hypomagnesemia: MgSO4 4g in D5W 250cc x 12-24h • Hypocalcemia: Ca Gluconate 1 amp SIVP or drip

  27. Exercises • 58 y/o male with diarrhea, previously with Lung CA • 62 kg • Watery non-bloody diarrhea, poor urine output • Awake, poor skin turgor, complaining of thirst • BUN 21.6, Crea 254, Na 128, K 1.8, Cl 97, Mg 0.67, Ca 2.51, alb 16, RBS 8.7 • TBW: 37.2 • Creatinine Clearance: 25 • BUN:Crea Ratio: 21 • Corrected Na: 128.6 • Corrected Calcium: 2.99 (mild) • Plasma Osmolality: 291 (normal to high)

  28. Exercises • 58 y/o male with diarrhea, previously with Lung CA • 62 kg • Watery non-bloody diarrhea, poor urine output • Awake, poor skin turgor, complaining of thirst • BUN 22.3, Crea 254, Na 128, K 1.8, Cl 97, Mg 0.67, Ca 2.51, alb 16, RBS 8.7 • Hyponatremia • Sodium deficit: 424.08 mEqs • Daily Sodium correction: 446.4 • pNSS: 2.9L/day • Hypokalemia: >600 to 1200 mEqs • Hypomagnesemia: MgSO4 3g in D5W 250cc x 12 • Hypercalcemia: Forced saline diuresis, Pamidronate

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