General Pediatrics Board Review Nephrology Fluids and Electrolytes

1. General Pediatrics Board Review Nephrology Fluids and Electrolytes Jeffrey M. Saland, M.D. Department of Pediatrics Mount Sinai School of Medicine

2. An 8 year old proudly announces to you that she did a report on jellyfish and they are 96% water. She asks you what is her “percent water?” What is the best estimate of her fluid compartments by percent of body weight?

3. An 8 year old proudly announces to you that she did a report on jellyfish and they are 96% water. She asks you what is her “percent water?” What is the best estimate of her fluid compartments by percent of body weight?

4. Composition of Body Fluids Babies are moist– but not quite jellyfish!

5. Finberg L. Water and Electrolytes in Pediatrics 1993 (data from Friis-Hansen BJ Pediatrics 1961) TBW ICW ECW

6. Distribution of body water as a percentage of body weight Compiled by Finberg, L. from data by BJ Friis-Hansen, ActaPaed Scand 1958 Technique: D2O for TBW and thiosulfate for ECW

7. Approx Body Composition > 1 year TBW = 60% Lean Body Mass: ICF = 2/3 TBW ECF = 1/3 TBW Plasma = 1/4 ECF (rest is interstitial fluid) TBW Na ~ 13 K ~ 140 Na ~ 140 K ~ 4 Plasma ICF ECF

8. A previously healthy 23 kg child is admitted for gingivostomatitis and refusal of oral intake. What is the most appropriate maintenance intravenous fluid prescription?

9. A previously healthy 23 kg child is admitted for gingivostomatitis and refusal of oral intake. What is the most appropriate maintenance intravenous fluid prescription?

10. What are maintenance fluids? The fluid and electrolytes necessary for a person to remain in net balance over the long term INTAKE ICF ECF Plasma OUTPUT

11. Sounds Easy!

12. What are maintenance fluids? Barratt M: Pediatric Nephrology 4th Ed 1998

13. What are maintenance fluids? Why did that graph estimate caloric needs? We need to know how many mL of fluid to order, not how many calories!

14. For the “average” patient, the use of 1 Cal corresponds to the use of 1 mL of water Insensible losses: respiratory 30 cc / 100 Cal + evaporative not sweat 15 cc / 100 Cal 45 cc / 100 Cal Urine output losses 50-75 cc / 100 Cal Stool losses 5-10 cc / 100 Cal Growth “loss” 0-15 cc / 100 Cal Water of oxidation (a gain) 10-15 cc / 100 Cal TOTAL Approximately100 cc / 100 Cal

15. Summary “maintenance fluids” Fluid needs are linked to the metabolic rate. Maintenance is approximately insensible plus urine losses. Maintenance fluids of the “average” patient are approximately:

16. Changes in the metabolic rate or the environment change insensible fluid loss Increased INSENSIBLE Losses Fever (each deg > 38): 12.5% Prematurity 100-300% Radiant warmer 50-100% Phototherapy 25-50% Increased activity 5-25% Decreased INSENSIBLE Losses Ventilation (humidified air) 25-40% Sedation 5-25% Decreased activity 5-25% Hypothermia 5-15% Enclosed Incubator 25-50%

17. Maintenance Fluid DOES NOT Include Abnormal Losses Common / “Community” losses Gastrointestinal: diarrhea, vomiting Activity: sweating, increasedventilation, heat Burns: (evensunburn!) Uncommon / “Nosocomial” losses Drainage (egchesttube, NG tube, et cetera) Bleeding Pathological renal losses (egsaltwasting, diabetes) Theselosses are universallyhypo- orisotonic

18. Composition of Various Body Fluids Harriet Lane Handbook

19. “Salt” Maintenance Requirements Na: 2-5 mEq / kg /day K: 1-2 mEq / kg /day There is a large variability in the intake of Na, and to a lesser extent K, by healthy people. Renal ability to conserve or excrete Na is very large. The ability to conserve or secrete K is also larger than the average variation in intake.

21. An 18 month old boy presents to the ER with a history of vomiting and diarrhea for several days. He is lethargic, has poor skin turgor, dry mucus membranes, and has tachycardia. He took 5 ml oral fluid but vomited almost immediately. The next most appropriate step is to: • Give 20 ml/kg of D5 ½ NS intravenously over 20-30 min • Give 5 ml/kg of D5 NS intravenously over 20-30 min • Give 20 ml/kg of NS intravenously over 20-30 min • Give 10 ml/kg of 3% NS intravenously over 20-30 min • Await serum electrolytes before giving IV fluid

22. A nearly 1 month old boy has been vomiting his feedings forcefully for 2 days. He is afebrile and has no diarrhea. He had 1 wet diaper in the last day. He appears dehydrated. He eagerly takes fluids but vomits (non-bilious) immediately and while he does so you note “waves” on his abdomen. What is the most likely set of labs?

23. A nearly 1 month old boy has been vomiting his feedings forcefully for 2 days. He is afebrile and has no diarrhea. He had 1 wet diaper in the last day. He appears dehydrated. He eagerly takes fluids but vomits (non-bilious) immediately and while he does so you note “waves” on his abdomen. What is the most likely set of labs?

24. Signs & Symptoms of Dehydration I (fairly reliable) Harriet Lane Handbook

25. Signs & Symptoms of Dehydration II (less reliable) Harriet Lane Handbook

26. A 2 year-old presents with a 1 day history diarrhea and a 5% weight loss. Which of the following best represents the distribution of the fluid loss?

27. A 2 year-old presents with a 1 day history diarrhea and a 5% weight loss. Which of the following best represents the distribution of the fluid loss? 3 or more days: the correct answer would have been B. The ICF is relatively protected from volume loss. Harriet Lane Handbook

28. A nearly 13 month old girl has had diarrhea for 5 days. She has few wet diapers. Her BP is 86/40, pulse is 135. She weighs 9 kg and you estimate she is 10% dehydrated based on clinical parameters. Disregarding Na losses from the ICF, which of the following estimates is best?

29. A nearly 13 month old girl has had diarrhea for 5 days. She has few wet diapers. Her BP is 86/40, pulse is 135. She weighs 9 kg and you estimate she is 10% dehydrated based on clinical parameters. Disregarding Na losses from the ICF, which of the following estimates is best?

30. A 13 month old child was seen for a checkup and weighed 10 kg. 10 days later in the ER with gastroenteritis she weighs 9 kg. 10% Dehydration. A liter weighs 1 kg. A pint’s a pound the world around.

31. A high school student and her friend have multiple episodes of vomiting and watery diarrhea after sharing lunch from a food cart at the park earlier in the day. Her bp is 95/45 and her pulse increases from 90 to 115 standing. She feels light-headed and has not urinated in the last 6 hours. Which is the most likely type of dehydration?

32. A high school student and her friend have multiple episodes of vomiting and watery diarrhea after sharing lunch from a food cart at the park earlier in the day. Her bp is 95/45 and her pulse increases from 90 to 115 standing. She feels light-headed and has not urinated in the last 6 hours. Which is the most likely type of dehydration?

33. A 14 year old girl is treated with a prolonged course of antibiotics for sinusitis. She develops profuse watery diarrhea that lasts several days. She had not been eating due to abdominal pain but had taken at least 2 liters of a yellow sports drink each day. In the ER, she still appears moderately dehydrated. You diagnose C. Dificile colitis. The most likely type of dehydration is:

34. A 14 year old girl is treated with a prolonged course of antibiotics for sinusitis. She develops profuse watery diarrhea that lasts several days. She had not been eating due to abdominal pain but had taken at least 2 liters of a yellow sports drink each day. In the ER, she still appears moderately dehydrated. You diagnose C. Dificile colitis. The most likely type of dehydration is:

35. A 14 year old boy with cerebral palsy and mental retardation develops fever to 40 °C. He is able to tolerate his usual liquid formula diet by gastric tube. You diagnose him with streptococcal pharyngitis but also note he has very dry mucus membranes and his skin feels thick. Which is the most likely set of lab findings?

36. A 14 year old boy with cerebral palsy and mental retardation develops fever to 40 °C. He is able to tolerate his usual liquid formula diet by gastric tube. You diagnose him with streptococcal pharyngitis but also note he has very dry mucus membranes and his skin feels thick. Which is the most likely set of lab findings?

37. Tonicity Classification of Dehydration

39. A 10 year old boy has high fever and dehydration due to seasonal influenza. He has not urinated in over 24 hours. His serum creatinine is elevated from 0.7 to 1.6. Urine is taken to calculate fractional excretion of Na. Two days later he is rehydrated and has normal urine output and his creatinine is baseline. What best describes his diagnosis and most likely FENa on presentation? • Acute kidney injury 3% • Acute kidney injury 0.3% • Pre-Renal Azotemia 3% • Pre-Renal Azotemia 0.3%

40. Consider a child with sepsis and decreased urine output with the following labs: SERUM: Na 124, K 4, Cl 94, Total CO2 12 Creat 0.8 mg/dL, BUN 40, Glucose 70 URINE: specific gravity 1.030, trace protein, no blood or glucose, small ketones; urine Na 15, creat 40

41. FENa is a useful test when: • The urine output is low. • No current use of diuretics. • < 1% (0.01): pre-renal azotemia (“acute renal success”) • > 2% (0.02): acute kidney injury (“acute renal failure”) • Exceptions: acute GN has low FENa, obstruction can vary

42. A 4 year-old girl with a ventriculoperitoneal shunt presents with a week of vague symptoms progressing toward listlessness and decreased speech, finally with a 5 minute seizure. The bulb of the shunt empties with pressure but is slow to refill. She does not appear dehydrated. The most likely set of laboratory findings is:

43. A 4 year-old girl with a ventriculoperitoneal shunt presents with a week of vague symptoms progressing toward listlessness and decreased speech, finally with a 5 minute seizure. The bulb of the shunt empties with pressure but is slow to refill. She does not appear dehydrated. The most likely set of laboratory findings is:

44. SIADH: Too Much ADH • Etiologies: • CNS disease (hydrocephalus, meningitis, etc) • Lung (pneumonia, RSV, etc) • Nausea or Pain • Cancer or Stem Cell transplantation • Drugs (SSRI’s) • Should exclude: • Thyroid, adrenal, cardiac, or renal disease • Volume deficits / dehydration • Hyponatremia, inappropriately high urine Osm (>100) • Urine Na can be variable– usually “highish”

45. A 7 year-old girl presents for secondary enuresis. On review of systems she has significant polyuria, polydipsia, and severe daily headaches that awaken her in the morning. Urinalysis in your office is negative for glucose and ketones. The most likely set of laboratory findings is:

46. A 7 year-old girl presents for secondary enuresis. On review of systems she has significant polyuria, polydipsia, and severe daily headaches that awaken her in the morning. Urinalysis in your office is negative for glucose and ketones. The most likely set of laboratory findings is:

47. Diabetes Insipidus: Not Enough ADH Or ADH not Effective • Etiologies: • CNS disease (pituitary infiltration, damage) • Drugs (lithium) • Nephrogenic (V2 receptor or aquaporin defect) • Others more rare • With access to water, just polyuria, polydipsia • Without access to water, hypernatremia, polyuria, polydipsia • Hypernatremic dehydration • Inappropriately dilute urine • Water deprivation test diagnostic but dangerous • Response to DDAVP diagnostic of central DI • Genetic testing for nephrogenic DI

48. An overweight 15 year old girl is admitted with polyuria and severe dehydration. Severe hyperglycemia of 800 mg/dl without ketoacidosis is discovered. Serum electrolytes are significant for Na of 140, K of 4.3, Cl of 98, CO2 of 19, BUN is 53, Creatinine is 1.6. Which of the following is NOT true? • Excessive 0.9% NS may exacerbate the situation • Serum K can be expected to fall with rehydration • Serum Na can be expected to rise with rehydration • Hyperglycemia causes the lab equipment to malfunction and produce falsely low Na values • Dehydration is the result of osmotic diuresis

49. Acid / Base Mr. Osborne, may I be excused? My brain is full.

50. A 6 month old girl born at term and with no apparent illnesses presents with failure to thrive. She is mildly tachypneic at rest. Lab evaluation is remarkable for serum Na 140, K 2.5, Chloride of 115, bicarbonate of 11 and creatinine of 0.3 mg/dL. Which of the following is most consistent with distal (type I) renal tubular acidosis (RTA)?