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

2. Clinically Relevant Electrolytes H 2 O – 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 P osm = 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 Na 167Mg 0.55 K 3.1BUN 2.13 Cl 111Crea 115 Ca 2.1Gluc 3.4 Is there water loss? Is it osmolar loss or free water loss? P osm = 346 mOsm/kg Free water deficit = 4.34 L

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

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

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 5% NaCl855 3% NaCl513 0.9% NaCl154 0.45% NaCl77 0.2% NaCl34 Plain LR130 D5W0

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 5% NaCl855 3% NaCl513 0.9% NaCl154 0.45% NaCl77 0.2% NaCl34 Plain LR130 D5W0

10. Hyponatremia: Exercise 65/M hypertensive patient Deterioration in sensorium 60 kg, xerosis, dry armpits Na 110Mg 0.46 K 2.9BUN 2.13 Cl 88Crea 120 Ca 1.99Gluc 12.22 Na corrected = 111.2 P osm = 242.6 mOsm/kg ECF: decreased Na def: 900 Daily Correction: 360 5% NaCl855 3% NaCl513 0.9% NaCl154 0.45% NaCl77 0.2% NaCl34 Plain LR130 D5W0

11. Na: High ECF Not increasedIncreased Give hypertonic solutions (hypertonic NaCl or NaHCO 3 ) Urine Osmolality Water losses (GI, insensible, remote renal) Urine output Minimal Non-minimal U osm = 2 (Na + K) + BUN + RBS

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

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 0.9% NaCl154 0.45% NaCl77 0.2% NaCl34 Plain LR130 D5W0

15. Hypernatremia: Exercise 21/M with vomiting 60 kg, dry buccal mucosa, UO 30cc/3h Na 180Mg 1.1 K 3.1BUN 3.46 Cl 115Crea 120 Ca 2.4Gluc 18.9 Na corrected = 182.4 P osm = 388.6 Free H20 deficit = 10.9L ECF: decreased UO: minimal Given infusate pLR: 8L/day for 3 days, 4L/day on the 4 th day

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

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 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 MgSO 4 3 g in D5W 250 cc x 24 0 = increase by 0.3

23. 11 Equations to memorize! P osm = 2(Na+K) + BUN/2.8 + Glucose/18 U osm = 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)/(U osm /P osm ) 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 3 rd day Hypokalemia: > 600 mEqs correction Hypomagnesemia: MgSO4 4g in D5W 250cc x 12-24h Hypocalcemia: Ca Gluconate 1 amp SIVP or drip 0.9% NaCl154 0.45% NaCl77 0.2% NaCl34 Plain LR130 D5W0

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 5% NaCl855 3% NaCl513 0.9% NaCl154 0.45% NaCl77 0.2% NaCl34 Plain LR130 D5W0