1. In Starting Maintenance Fluids
  2. In Starting Fluids To Correct Deficit
  3. In Starting Fluids in Shock
A. In Starting Maintenance Fluids
Isolyte-P is an ideal and most widely used maintenance fluid for younger children because...
  1. Ideal electrolyte concentration (Na 25 & K + 20 mEq/l)
  2. Contains acetate, which provides bicarbonate
  3. Provides magnesium and phosphate
  4. Provides 50 g/l of glucose to provide calories
  5. Uniform administration of fluid and electrolytes

Remember: Isolyte-P is not an ideal maintenance fluid for older children
Reason: In children as weight increases, water requirement reduces rapidly, 100 ml/Kg (1-10 kg)? 50 ml/Kg (11-20 kg) ? 20 ml/Kg (> 20 kg)
But sodium requirement remains static (2.5 mEq/kg). So children with greater weight will need I.V. fluids with greater sodium concentration.
Example: In older children with 30 kg water requirement is 1000 + 500 + 200 = 1700 ml and sodium requirement is 75 mEq. So sodium concentration required is 44 mEq/l, while Isolyte-P contains only 25 mEq/l sodium. Because of low sodium concentration Isolyte-P is not an ideal maintenance I.V. fluid for older children.

Consequences of improper selection of maintenance fluid ...
Isotonic saline : Hypernatremia, hypokalemia & hypoglycemia
Ringer's lactate :Hypernatremia, hypokalemia & hypoglycemia
Dextrose 5% : Hyponatremia & hypokalemia

Summary: In younger children low sodium-containing (Na = 25 mEq/l) fluid, Isolyte-P is an ideal maintenance fluid. But for the children with weight greater than 15 kg, additional sodium supplementation is needed. Isolyte-M contains greater (Na = 40 mEq/l) sodium.
B. Where Do We Go Wrong In Starting Fluids To Correct Deficit
After proper assessment of dehydration, fluid deficit is calculated. Fluid volume required to be replaced in mild dehydration is 40-50 ml/kg; moderate dehydration is 60-90 ml/kg, and severe dehydration is 100-110 ml/kg.

Remember Misleading Signs In Assessment of Dehydration:
  1. In obese infant degree of dehydration is often under-estimated
  2. In marasmic infant degree of dehydration is often over-estimated
  3. In hypernatremic dehydration, skin and circulatory changes may be very less, with predominant neurological signs.

Proper selection of fluids: To replace fluid deficit which fluid to be infused is an important issue. Three important factors to be considered are:
  1. Etiology of Deficit
  2. Presence of Electrolyte Disorders
  3. Presence of Acid Base Disorders
  1. Select I.V. Fluid Considering Etiology of Deficit:

    Preferred solutions for initial fluid replacement are Ringer's lactate for diarrhea and Isotonic Saline for vomiting. As approximate sodium content of viral diarrhea, cholera and Ringer's lactate are 50,100 and 130 mEq/l respectively, fluid deficit due to diarrhea should not be corrected totally with RL. It carries risk of development of hypernatremia.
    • (a) Select I.V. Fluid Considering Presence of Electrolyte Disorders: Important electrolyte disorders are related sodium and potassium.
    • (b) Select I.V. Fluid Considering Sodium Status to Correct Deficit. Dehydration is divided in three groups considering sodium status.
      1. Isonatremic (Isotonic) Dehydration : 70%
      2. Hyponatremic (Hypotonic) Dehydration : 20%.
        Etiology : Deficit corrected solely by plain water, 5% Dextrose or Isolyte-P is an important cause !
        Clues :Drowsiness, colder skin, very poor skin turgor and hemodynamically unstable patient.
        Treatment :Needs high sodium containing fluids (NS, RL) to correct deficit gradually.

      3. Hypernatremic (Hypertonic) Dehydration : 10%
        Hypernatremic (Hypertonic) Dehydration : 10%
        Clues :Hyperirritability, skin and circulatory changes may be very less.
        Treatment :Needs low sodium containing fluid (Isolyte-P) to correct deficit gradually.

  2. To select proper sodium containing fluid, it is important to remember sodium concentration (mEq/L) of various I.V. fluids and ORS.

    Sodium Concentrations of various I.V. Fluids
    Sodium mEq/L
    0.9% NaCI 154
    Ringer's Lactate 130
    Isolyte-G 63
    Isolyte-M 40
    Isolyte-P 25

    Sodium Concentration of ORS :
    Old WHO Formula : 90 (mEq/L)
    New WHO Formula : 75 (mEq/L)
    Low Osmolar Formula : 50 (mEq/L)
    (One gram of salt (NaCI) contains 17.1 mEq sodium)

    Select I.V. Fluid Considering Potassium Status to Correct Deficit:
    is the most common potassium problem. Two most common causes of dehydration with hypokalemia are diarrhea and vomiting.

    Clues : Weakness, hypotonia, abdominal distension and paralytic ileus.
    Treatment : Select appropriate potassium containing I.V. Fluid or add Inj. Potassium Chloride (KCI) in pint

    Potassium Concentrations of various I.V. Fluids
    I. V. Fluids K+ (mEq/L)
    Isolyte-M 35
    Isolyte-M 20
    Isolyte-G 4
    RL 35

    Potassium chloride (KCI) 15% 10 ml Amp. = 20 mEq of Potassium or 1 ml KCI = 2 mEq of potassium
  3. Select I.V. Fluid Considering Presence of Acid Base Disorders:
    Metabolic Acidosis:
    Most common acid base disorder in patients with dehydration. Metabolic acidosis occurs commonly due to Diarrhea. If dehydrated child looks dyspneic (Kussmaul's breathing), think of metabolic acidosis.
    Treatment: Ringer's lactate, preferred I.V. fluid in patients with diarrhea provides 28 mEq/L of bicarbonate. Injection Sodium Bicarbonate 7.5%, 10 ml provides 9 mEq Bicarbonate.
    Summary:To correct fluid deficit, after calculating volume of fluid to be infused, select appropriate fluid considering etiology of deficit and presence of electrolytes as well as acid base disorders.

C. Where Do We Go Wrong In Starting Intravenous Fluids In Hypovolemic Shock?
It is very important to remember that initial treatment of hypovolemic shock is same in all type of dehydration (Isotonic / hypotonic / hypertonic dehydration). Which I.V. solutions should be used to correct hypovolemic shock? Why? Prompt and perfect selection of I.V. fluid is mandatory for proper treatment of hypovolemic shock. Fluids, which can expand intravascular compartment effectively, are preferred. Amongst crystalloids, sodium-containing fluid is potent and effective.

Selection of I.V. Solutions in initial treatment of Hypovolemic Shock:
  1. Isotonic Saline / RL are most preferred fluids
  2. Colloids & Blood are most effective
  3. Colloids & Blood are most effective

Rise in Intravascular Compartment with Various I.V. Agents
Type of fluid (1000 ml) Increase in Intravascular volume
5% Dextrose 83 ml
Isotonic Saline 300 ml
Colloids / B.T. 100 %

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