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51 Cards in this Set

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How does the human body weight change since when a human is born?
Initially human is 90% water, by first year of life muscle mass increases and by 1 year of age, 60% body weight is water
what are critical to the maintenace of normal physiology?
Electrolyte homeostasis, fluid distribution, and pH balance. The younger the patient the more intolerant he is to challeng of these symptoms
What are mainteance fluids?
Amount of fluid needed to maintain normal body function. Related to caloric expenditure and child's weight
What is the Holliday-Seger Method?
4ml/kg/hr for the first 10kg
2ml/kg/hr for the second 10kg
1ml/kg/hr for each additional kg
What electrolytes are necessary in maintenance fluids?
3 mEq of sodium and 2 mEq of potassium as well as carbohydrate source

One-fourth to one-half normal saline with 5% dextrose (10% in infants) and 20mEq/L KCl meets mainteance glucose and electrolyte needs
Why do most pediatric patients have dehydration?
Vommiting, diarrhea, immature kidney
What are quantitiave measures of fluid loss?
Recent weight loss and decreased urine output
What are some chronic medical illnesses that may present acutely with dehyration?
diabetes, metabolic disorders, cystic fibrosis, and congenital adrenal hyperplasia
what three coniditions may have poluria in the presence of physical signs of dehydration?
Diabetes Mellitus
Diabetes Inspidus
Renal Tubular Acidosis
What are the child's primary mechanism of compensationg for decreased plasma volume?
tachycardia, hypotension
very late and ominous finding
What are the clinical factors found in mild dehydration?
Weight: <5% weight loss, Vitals: increased heart rate, normal RR, normal BP
Skin: <2 sec cap refil, normal/dry mucous membranes, nl Anterior fontanelle
Eyes: normal tearing, normal appearace
Mental: Normal
Lab Values: Urine 600 mOsm/L. 1.020 specific gravity, BUN<20, normal pH
NOT IN SHOCK
What are the clinical factors found in moderate dehydration?
Weight: 5-10% weight loss, Vitals: increased heart rate, normal RR, normal BP (orthostasis)
Skin: 2-3 sec cap refil, dry mucous membranes, depressed Anterior fontanelle
Eyes: absent tearing, sunken appearace
Mental: Altered
Lab Values: Urine 800 mOsm/L. 1.025 specific gravity, BUN elevated, mildly acidotic pH
COMPENSATED SHOCK
What are the clinical factors found in severe dehyration?
Weight: >10% weight loss, Vitals: greatly increased heart rate, increased RR, decreased BP
Skin: >3 sec cap refil, dry mucous membranes, depressed Anterior fontanelle
Eyes: absent tearing, sunken appearace
Mental: Depressed
Lab Values: Urine Max mOsm/L, High specific gravity, BUN elevated, mildly acidotic pH
UNCOMPENSATED SHOCK
What helps guide the choice of fluid composition and rate of replancement?
Serium electrolyte level: hypotonic(hyponatremic), Hypertonic (hypernatremic), isotonic
What is the most common form of dehyration?
Isotonic dehyration is the most common form and suggest that either compensation has occured or that water loss roughly parallels sodium losses
What is the definition of hypotonic (hyponatremic) dehyration?
Serum sodium less than 130 mEq/L, happens to children who lose electrolytes in their stool and are supplemented with free water or very dilute juices
What is the definition of hypertonic,hypernatremic?
Na>150mEq/L
uncommon in children but implies an excessive loss of free water compared with electrolyte loss (diabetes inspidus)
What is the usual pH of patients with dehyration?
usually serum bicarbonate concetration is decreased secondary to metabolic acidosis
when is the pH of patients with dehydration not acidotic?
when patient has had protracted vommiting, results in alkalosis result of acid loss from gastric secretions
What happens in significant dehydration? And how is this reflected?
perfusion of kidneys may be impaired, BUN and creatinine levels elevated as GFR falls
BUN/Creatine ratio greater than 20 is consisten with prerenal failure
What is the treatment for dehyration?
Oral Rehydration Therapy is the prefered treatment for mild to moderate dehydration
contains 90mEq/l sodium, 20 mEq/l K, 20g/l glucose

comercial preparations: pedialyte
What is the problem with ORT?
Requires small volumes given very frequently, takes time, but is very effective
What can happen with severe dehyration?
Can lead to life-threatening hypovolemic shock
What is the treatment of severe hypovolemic shock?
20ml/kg iv bolus of isotonic fluid (normal saline or Ringer's lactate) until their condition stabilizes
How are most deficits of maintance fluids replaced?
Most given in 24 hrs, 1/2 first 8 hrs and rest over 16 hrs with the exception being hypernatremic dehdration in whom the deficit should be replaced over 48 to 72 hours to prevent excessive fluid shifts and brain edema
How do you replace ongoing losses?
Usually in stool, replaced milliliter for millilter with IV fluid comparable in electrolyte content with being lost
How does the composition of the replacement fluid vary with the initial laboratory values?
Replacement (and maintenace) fluid should be potassium free untill the patient urinates
Bicarbonate or acetate therapy may be indicated if the pH and serum bicarbonate levels remain dnagerously low after the initial boluses

Patients with profund hyperglycemia or electrolye disturbances due to underlying patholigic process (diabetic ketoacidosis) may require more specialized management
What is the most common situation of hyponatremia?
serium sodium level less than 130 mEq/L may occur in face of decreased normal, or increased total body sodium content most commonly dehyration, SIADH, water intoxication, Congestive heart failure, adrenal insufficiency
What are the symptoms of hyponatremia?
depends on level of sodium loss and the rate of change: anorexia, nasuea, neurologic findings, confusion, lethargy, decreased deep tendon reflexes, seizures, and respiratory arrest
What is included in the laboratory workup of hyponatremia?
serum electrolytes, glucose, blood urea nitrogen and creatine, serum osmolality, liver function tests, protein, lipid levels
What is used for the treatment of dehyration hyponatremia?
cautious use of 3% of hypertonic saline
What are the signs and symptoms of hypernatremia?
muscle weakness, irritability, lethargy, seizures and coma
What is normal potassium values?
3.5-5.0 mEq/L
hyperkalemia is 5.5 mEq/L
what is the most common cause of hyerpkalemia in child?
hemolysis of red cells, transcellular shifts in hydrogen ions increase serum potassium without changing total body content
How does plasma potassium level change with arterial pH? what percipitates hyperkalemia?
for every unit reduction in arterial pH, plasma potassium increases 0.2 to 0.4mEq/l

disorders and medications that interfere with renal excretion of the electrolyte precipitate true hyerpkalemia
What are common casues of hyperkalemia?
Acidosis
Severe dehyration
Potassium-sparing diuretics
Excessive parenteral infusion
Renal failureAddison's Disease
Renal Tubular Acidosis
Massive Crush injury
Beta-blocker or theophylline intoxication
How does hyperkalemia present?
early: paresthesias and weakness
late: tetany, flaccid paralysis, cardiac involvement ECG Changes, Twave peaking is followed by loss of T waves, widening of QRS complex, and ST Depression, V Fib and Cardiac arrest
What level of potassium would lead to Ventricular Fibrilliation and cardiac arrest?
9meq/l
What is the treatment for hyperkalemia?
calcium gluconate protects the heart by stabilizing the cardiac cell membrane

infusion of sodium bicarbonate or insulin (and glucose) drives potassium into the cells

cation exchange resins (Kayexlate) and hemodialysis are the only measures that actually remove potassium from the blood
when is hypokalemia encountered?
cases of alkalosis secondary to vomiting, administration of loop diuretics, or diabetic ketoacidosis
what are the signs and symptoms of hypokalemia?
weakness, tetany, constipation, polyruia, polydipsia, muscle breakdown leading to myoglobinuria and compromise renal function
when are ECG changes noted in hypokalemia?
levels less than or equal to 2.5 mEq/L; cardiac arrhythmias more likely when patient being treated with digitalis
what is the treament of hypokalemia?
correcting pH when increased and replenishing potassium stores
how is the extreacellular fluid pH (hydrogen ion concetration) kept in a very narrow range?
bicarbonate buffer system
hydrogen ions combine with HC03- to form H2CO3 which in turn breaks down to water and CO2 which is expired by the lungs

the addition of H+, the loss of HCO3- abnormal pulmonary function can all affect the buffering system and lead to acid-base disturbances
how does metabolic acidosis result?
loss of HCO3- or the addition of H+ in the extracellular fluid and is the most common acid- base disorder encountered in the pediatric population
what formula predicts the expected PaC02 in the presence of metabolic acidosis
PaCO2= 1.5x HC03- +8(+/-2)
if the measured PaCO2 is higher than expected than there is a primary respiratory acidosis, if it is lower than expected then there is primary respiratory alkalosis
What is the most common clinical finding in metabolic acidosis?
Hyperpnea
How is the anion gap calculated?
the difference between the sums of the measured cation (Na+ + K+) and anions (Cl- + HCO3-) normally 12+/- 4
When is sodium bicarbonate given to patients with metabolic acidosis?
IV administration of sodium bicarbonate is reserved for cases in which the serum pH is less than 7.0 and the cause is unknown or difficult to reverse

Patients receiving alkali thereapy require frequent pH, sodium, potassium, and calcium monitoring, complications include, alkalosis, hypokalemia, hypernatremia, and hypocalcemia
What is contraction alkalosis?
loss of fluid high in H+ or Cl- as may occur with protracted gastric vomiting or chronic thiazide or loop diuretic administration
why might patients with cystic fibrosis develop metabolic alkalosis?
due to excessive electrolyte losses in the sweat