Fluid And Electrolytes

Question 1

Low urinary fractional excretion of sodium, high urine osmolality, high serum osmolality

Answer 1

Dehydration

Question 2

High urinary fractional excretion of sodium, low serum sodium, low serum osmolality, inappropriately high urine osmolality

Answer 2

Syndrome of inappropriate ADH secretion (SIADH)

Question 3

Low urine osmolality, high serum sodium, and serum osmolality (urine osmolality

Answer 3

Diabetes insipidus

Question 4

Low serum and urine osmolality

Answer 4

Primary polydipsia

Question 5

Child with mild to moderate dehydration because of diarrhea, able to drink with no emesis. What is the best treatment?

Answer 5

Oral rehydration solution (ORS)

Question 6

What is the mechanism of action of ORS?

Answer 6

Sodium-glucose transporter in the gut (co-transports one sodium with one glucose)

Question 7

Child with moderate dehydration, no emesis, and low serum potassium (K) level 2.6mEq/L.No other symptoms. What is the best treatment?

Answer 7

ORS and oral K chloride supplementation (oral replacement is better than IV if tolerating oral intake)

Question 8

Child with vomiting, weakness, lethargy, moderate-severe dehydration, and low serum potassium (K) level 2.6mEq/L.What is the best treatment?

Answer 8

IV bolus 20ml/kg normal saline, then IV fluids and electrolyte replacement

Question 9

Based on the Holliday-Segar method, what is the maintenance fluid rate for 45kg child?

Answer 9

First 10kg × 4=40
2nd 10Kg × 2=20
25kg × 1=25
40 + 20 + 25=85ml/h

Question 10

A 12-month-old girl with 4days of frequent watery stool; she is listless. O/E: dry mucous membrane, skin is tenting, HR 150, BP 85/45mmHg. Weight 8.5kg. Weight before illness 10kg, serum Na 136mEq/dL. 200mL of NS given IV.What is the most appropriate IV fluid and rate for this child?

Answer 10

D5 ½ NS +KCl 40meq/L to run at 95mL/h (15% dehydration; fluid deficit is 1500 + 1000 (maintenance—200 (bolus) = 2300/24h = 95ml/h)

Question 11

A 12-month-old girl with 4days of frequent watery stool, she is listless. O/E: dry mucous membrane, skin is tenting, HR 170, BP 80/40mmHg. Weight 8kg. Weight before illness 10kg, serum Na 136mEq/dL. 200mL of NS given IV.What is the most appropriate IV fluid and rate for this child?

Answer 11

D5 ½ NS + KCl 40meq/L to run at 116mL/h (20% dehydration; fluid deficit is 2000 + 1000 (maintenance—200 (bolus) = 2800/24h = 116ml/h)

Question 12

A quick calculation in the previous case?

Answer 12

The maintenance rate for a 10kg child = 40ml/h → triple the maintenance rate in 20% dehydration → 120ml/h (close to 116)

Question 13

A quick calculation of IV fluid rate in 5% dehydration

Answer 13

1½ times the maintenance rate

Question 14

A quick calculation of IV fluid rate in 10% dehydration

Answer 14

Double the maintenance

Question 15

A quick calculation of IV fluid rate in 15% dehydration

Answer 15

2 ½ times the maintenance rate

Question 16

What is the advantage of ORS over other fluid options?

Answer 16

Low carbohydrate, high sodium and potassium (minimizing osmotic loads that drive more diarrhea)

Question 17

What is a normal anion gap?

Answer 17

Na+ – (Cl– + HCO3–) = 10–12mEq/L

Question 18

What are the causes of anion gap metabolic acidosis?

Answer 18

Methanol poisoning, Uremia, DKA, Paraldehyde, Iron toxicity, INH, Lactic acidosis, Ethylene glycol, Salicylate poisoning (MUD PILES)

Question 19

What are the causes of non-anion gap metabolic acidosis?

Answer 19

Renal tubular acidosis
Diarrhea
Chronic total parenteral nutrition (TPN) Acetazolamide (carbonic anhydrase inhibitor)

Question 20

A 3-week-old boy with projectile vomiting after each feed, dehydration, metabolic alkalosis, hypochloremia, hypokalemia, oliguria, and low urinary chloride (

Answer 20

Pyloric stenosis (metabolic alkalosis and low urine chloride)

Question 21

Child with bloody diarrhea, high fever, weakness, edema, oliguria, BUN 80mg/dL, creatinine 5mg/ dL, K level is 7.5mg/dL.EKG shows a widening of QRS complexes and an increased PR interval. What is the best management?

Answer 21

Intravenous calcium gluconate, glucose, and insulin, beta agonists, cation exchange resins (sodium polystyrene sulfonate), until dialysis can be initiated

Question 22

What is the earliest EKG manifestations in cases of mild hyperkalemia?

Answer 22

Tall and peaked T waves

Question 23

What is the EKG manifestation in cases of moderate hyperkalemia?

Answer 23

Widening of QRS complexes and an increased PR interval

Question 24

What is the EKG manifestation in cases of severe hyperkalemia?

Answer 24

Broad and low amplitude P waves, a prolonged QT interval, and ST-segment changes (elevation or depression)

Question 25

What is the EKG manifestation of hyperkalemia >8mEq/L?

Answer 25

Gradually widening QRS complexes and absent P waves → ventricular fibrillation or asystole