maintenance iv fluids in pediatrics
TRANSCRIPT
Goals of maintenance therapy• Prevent dehydration (replace sensible & insensible water loss)• Prevent electrolyte disturbances• prevent ketoacidosis• prevent proteins degradation
Duration• Few days (no enough calories, proteins, other electrolytes)• If more, need enteral feeding or TPN
First,We need to understand some important concepts
Osmolarity vs. Tonicity
total solutes in water(Osmolarity)
Semi-permeable membrane
(Tonicity)
Osmolarity vs. Tonicity
Osmolarity : concentration of solute in a volume of fluid (eg. mOsmol/Liter)
Tonicity : As Osmolarity but measures only solutes which can NOT pass the semipermiable membrane
• Hyperosmolar solution is NOT necessarily a Hypertonic solution • eg. Osmolarity of Glucose 5% in the Bag = ~250 mOsm/L (near plasma
osmolarity) ,but once infused in body is rapidly metabolized = considered hypotonic solution
• Normal plasma Na level = 135 - 145 mEq/L • Any fluid with sodium content near this concentration = Isotonic (eg.
NS or LR )• fluids with lower Na content = Hypotonic (eg. Saline 0.18% - 30
mEq/L)
Effect of plasma fluid tonicity on body cells
Normal Plasma
Body cell
Hypertonicity
Smaller cell
Hypotonicity
Edematous cell
Brain cellsRBCs
Challenges in Hospitalized Children • Normally :
Hyponatremia -> Inhibit thirst center -> Decrease water intake• Hospitalized child :
No control of fluid intake (IV fluids) -> more hyponatremia
Role of ADH in producing hyponatremia • Effect :
prevent water loss in urine -> retention -> decrease Na concentration (dilution)• Triggers :• Osmotic : Hypernatremia• Non-osmotic : GE (Vol. deplition) / Chest infection / CNS infection / Surgery
(Pre or Post) / Stress / Pain
Isotonic VS. Hypotonic maintenance fluids • Many studies on pubmed (RCTs, Meta-analysis) compared effect of
Isotonic vs. hypotonic solutions and all suggested Isotonic to be of choice due to less side effects (hyponatremia) compared with hypotonic solutions.
Isotonic VS. Hypotonic maintenance fluids • Nelson 20th Textbook : • 0.2NS is no longer recommended as a standard maintenance fluid and its use
is restricted at many hospitals.• D5 1/2NS + 20 mEq/L KCl is recommended in the child who is NPO and does
not have volume depletion or risk factors for nonosmotic ADH production.• Children with volume depletion, baseline hyponatremia, or at risk for
nonosmotic ADH production (lung infections such as bronchiolitis or pneumonia; central nervous system infection) should receive D5 NS + 20 mEq/L KCl.
Isotonic VS. Hypotonic maintenance fluids • Nelson 20th Textbook : • Electrolytes should be measured at least daily in all children receiving more
than 50% of maintenance fluids intravenously unless the child is receiving prolonged intravenous fluids (TPN).• Patients with persistent ADH production because of an underlying disease
process (syndrome of inappropriate ADH secretion, congestive heart failure, nephrotic syndrome, liver disease) should receive less than maintenance fluids.
Isotonic VS. Hypotonic maintenance fluids • Nelson 20th Textbook : • Fever increases 10-15% maintenance water needs for each 1°C above 38°C (if
persistent)• Replace ongoing loss in Diarrhea
Solution: D5 1/2NS + 30 mEq/L sodium bicarbonate + 20 mEq/L KCl• Replace ongoing loss in Vomiting
Solution: normal saline + 10 mEq/L KCl
From history : Holliday and Segar calculations (1957)• Caloric requirements = between BMR & Energy Expenditure after normal
activity• 100 cal/kg per day (for patients weighing up to 10 kg)• 1000 cal + 50 cal/kg per day per kg over 10 kg (10-20 kg)• 1500 cal + 20 cal/kg per day per kg over 20 kg (>20 kg)
• After calculating Urine output + Insensible water loss (Skin/Respiratory) >> for every 100 kcal = 100 mL water loss (Urine loss 66.7 + Insensible 50 - Metabolic product 16.7 = 100)• Estimation of electrolytes requirements was based on human milk content
of sodium, potassium & chloride• Na = 3mEq/100 mL = 30mEq/L = 0.18% Saline (4:1)
Glucose• D5 = 20% of caloric needs per day• Prevent protein degradation & ketone production• will loose weight (1% per day) = need TPN or Enteral feeding
Hypotonic fluids are preferred ? • The purpose of maintenance fluids is not to restore volume deficit but
to replace urinary and insensible losses. Thus, giving an isotonic solution to a hypovolemic ill patient to restore intravascular volume will suppress ADH secretion. When ADH secretion is suppressed, a hypotonic maintenance fluid will not cause hyponatremia.
• The answer : The tonicity of the maintenance fluid therapy is more important than volume in the prevention of hyponatremia. As hypotonic maintenance fluid therapy administered at a lower volume (one-half to two-thirds maintenance) has a higher rate of hyponatremia compared with isotonic maintenance fluid therapy.
Hypotonic fluids are preferred ? • the increased sodium load may lead to volume overload and/or
hypernatremia; isotonic maintenance fluids contain approximately 5 times as much sodium as the ‘‘old maintenance."
• The answer : randomized studies have addressed these concerns & isotonic maintenance fluid can be safely administered in standard maintenance volume without causing hypernatremia.
Some basic calculations
10 grams glucose+ 100 mL water= glucose 10%
5 grams glucose+ 50 mL water= glucose 10%
5 grams glucose+ 50 mL water= glucose 10%
5 grams glucose+ 100 mL water= glucose 5%
Some basic calculations
0.9 gram Saline+ 100 mL water= Saline 0.9%(Normal Saline)
0.45 gram Saline+ 50 mL water = Saline 0.9%(Normal Saline)
0.45 gram Saline+ 50 mL water= Saline 0.9%(Normal Saline)
0.45 gram Saline+ 100 mL water= Saline 0.45%(Half Normal Saline)
D5 NS= each 100 mL contains 5 grams glucose + 0.9 grams saline
D5 1/2NS= each 100 mL contains 5 grams glucose + 0.45 grams saline
Indications for fluid restriction • Cases with persistent ADH secretion• ALI & ARDS• CNS Infection (SIADH ?)• CHF• Liver disease• Surgery
• Cases with decrease water loss• Renal Failure (Oliguria)• Mechanical ventilation
Final thoughts1. Maintenance fluids are only temporary and you should start oral
feeding as soon as possible.2. Only restrict fluids in previously mentioned cases3. Apply the suggested new fluids concentration (D5 ½NS)4. Increase maintenance fluids according to the condition (Fever,
Vomiting, Diarrhea)
Thanks