Perioperative fluid management in Infants and Children
Department of Anesthesiology
J.W. Goethe University Frankfurt/Main, Germany
Theodor Stern Kai, D-60596
Perioperative infusion therapy should be adapted to the physiologic
differences between newborns and adults, and fluid and electrolyte
regulation during growth. Fluid requirements and maturation of the
kidney set limits on the type and quantity of intraoperative fluids
The major difference between infants and adults is the fact that 40%
of body water in newborns is extracellular fluid (ECF), while in
adults, the ECF is 20%. This extracellular water is in the
interstitial fluid volume, while plama volume is similar at all
ages. The high percentage of ECF causes a high turnover of water and
electrolytes, especially sodium. A newborn child may lose 10% of its
body weight if it drinks nothing for a day.
Pre- and perioperative fluid losses consist of hypotonic and isotonic
components. The hypotonic fluid losses from the body are from sweat
and diarrhea. This is low in sodium, i.e. 0.25 to 0.5 normal
saline. Isotonic fluid losses include those that result from trauma,
burns and losses from the upper GI tract, e.g. due to vomiting. Ileus
and peritonitis may lead to great volume shifts and acute hypovolemia.
Fluid requirements are higher in hot rooms and in fever. For every 1 C
fever about 10% more fluid is necessary. Intraoperative fluid
deficits may result from exposure of large areas of tissue, as in
abdominal and thoracic surgery, as well as from blood loss.
The fetal kidney produces only amniotic fluid. Renal vascular
resistance (RVR) is high, renal blood flow (RBF) and glomerular
filtration rate (GFR) are low. The low GFR limits the renal function
in the first 24h. Postpartum renal RVR decreases and with increasing
systemic blood pressure RBF and GFR increase. By four to five days
there is a marked improvement in renal function, and the ability to
conserve fluid and excrete an overload. After one month the kidney is
approximately 60% mature. Fluid and sodium conservation is limited in
newborns and infants, while excretion of water and electrolytes is
possible even in premature infants. Tubular function is especially
limited for special excretion and reabsorption mechanisms. Prematures
have limited ability to reabsorb sodium, and will therefore become
hyponatremic without adequate replacement. The tresholds for glucose
and sodium bicarbonate are lower than in adults. Hyperglycemia may
lead to osmolar diuresis with consequent deficits in water and
sodium. By 18 months, renal function is completely matured.
There has been a change in the recommended time for patients to be
fasted. Fat and milk slow gsatric emptying time. For infants younger
than one year milk should be given up to 6 h before surgery, and clear
fluids up to 3 h. In the age of 1 and 2 years clear fluids are allowed
up to 4h before surgery . Children older than 3 years can be
handled as adults. The NPO time should be as short as possible to
reduce preoperative volume deficiency the child's discomfort.
Clinical signs of volume depletion
In young infants the fontanelles, the eyes and the tongue are good
indicators of volume deficit. Fontanelles and eyes may be sunken when
the volume deficit is about 5%. The tongue is small in hypovolemia and
the mucous membranes are dry. Blood pressure and heart rate may remain
normal even when the fluid deficit is as high as 10% of body weight.
Intraoperative fluids must be replace bothpreoperative deficit, and
intraoperative hypotonic and isotonic deficits. When hypotonic solutions
are administered, the kidney must excrete the extra water and therefore
loses sodium. Because of the ability of the kidneys to dilute urine
and excrete sodium even in young infants, administering of balanced salt
solutions is the better choice. In the first hour patients under 4 years
should receive 25 ml/kg of balanced salt solution. In children older
than 4 years, fluid replacement during the first hour should be 15
ml/kg-h. Tis volume should replace the preoperative deficit, e.g., a
child who has been NNPO for 6 hours = 6 * 4 ml/kg = 24 ml/kg. In the
next hour, maintenance luid (about 4 ml/kg) and trauma requirements
should be replaced depending on the severity of the trauma. Mild trauma
- 2 ml/kg-h, in moderate trauma 4 ml/kg-h, and in severe trauma 6
ml/kg-h should be administered. 
Because of immature kidney function, hydroxyethylstarch should no be
administered to children younger than two years. The large starch
molecules cannot be filtered by the kidneys and therefore remain for an
unpredictable length of time in the circulation. Human albumin 5% may
be administered in cases where blood loss requires more than crystalloid
solutions but less than blood transfsion. In acute hypovolemia, 10 - 20
ml/kg of human albumin 5% may be necessary to compensate for
intravascular deficit. In infans and children, intraoperative blood
pressure is a good reflection of blood volume and volume depletion.
Postoperative Fluid Problems
Acute dilutional hyponatremia may occur when the postoperative infusion
is immediately changed to hypotonic saline or glucose solutions. The
renal threshold for glucose is low in young children and might therefore
produce an osmotic diuresis with depletion oof sodium and water. The
sodium depletion due to tissue damage or postoperative vomiting may
produce a further decrease in plasma sodium. The plasma in acute
dilutional hyponatermia is hypotonic, thus a shift of water from the
hypotonic ECF to the isotonic ICF may result. This shift results in
cerebral edema with clinical symptoms of central nervous system
irritability, decreasing consciousness, disorientation, vomiting, and,
in severe cases, seizures.
The drug of choice is sodium bicarbonate 6% in dosages of 2 ml/kg
intravenously. After this, balanced salt solutions should be
administered. The intravenous sodium will increase plasma osmolarity
and concurrently shift waer out of brain cells. If the sodium is still
below 120 mmol/l, a further dosage of 1 mg/kg may be necessary.
Seizures are treated with oxygen and antiseizure medications, such as
diazepam. Physiologic sodium chloride should not be used for treatment
of acute dilutional hyponatremia because of its high chloride content.
1. Berry FA: Perioperative fluid management for pediatric patients.
1992 ASA Annual Refresher Course Lectures: 422.
2. Berry FA: Practical aspects of fluid and electrolyte therapy.
pp89-120 in: Anesthetic management of difficult and routine pediatric
patients. Berry (ed) New York, Churchill Livingstone, 1990.
3. Cote CJ: NPO after midnight for children - a reappraisal.
Anesthesiology 72: 589 - 592, 1990.
4. Johr M: Kinderanasthesie. Gustav Fischer Verlag, Stuttgart, 1993.
5. Steward DJ: Manual of pediatric anesthesia - British Columbia
Children's Hospital, Churchill Livingstone, New York, 1990.