5. Fluid Management in Children Undergoing Surgery and Anesthesia
KeywordsPreoperative fastingBlood transfusion in childrenPediatric intravenous fluidsPediatric fluid managementMassive transfusion in childrenCritical bleeding in childrenTransfusion trigger in children
As with drug treatment, fluid treatment in children demands more precision than in adults. This chapter explains the management of fluids in infants and children in the peri-operative period. Topics include fluid resuscitation, maintenance fluids and the replacement of ongoing losses. Fasting guidelines and the management of electrolyte disturbances are also included.
5.1 Body Fluid Composition
Blood volume at different ages
Estimated blood volume (mL/kg)
Infants and children
5.1.2 Coagulation Changes
Coagulation factors are produced by the fetus and have low levels at birth, but this is balanced by lower levels of inhibitors than in adults, a stronger binding fibrinogen molecule and lower activity of the fibrinolytic system. Clotting tests can therefore be prolonged despite no bleeding tendency. The rotational thromboelastogram (ROTEM) of a neonate has clinically minor differences until about 4 months of age, when it becomes the same as that of an adult.
5.2 Preoperative Fasting
Minimizing fasting in children reduces anxiety and irritability as well as physiologic and metabolic derangements. Neonates in particular, have low glucose stores and are at risk of hypoglycemia—a 10% glucose in 0.22% saline infusion is started if the fasting time is longer than the usual time between the baby’s feeds.
The duration of fasting of children before anesthesia has traditionally followed the 6-4-2 rule: 6 h for light food and milk, 4 h for breast and formula milk, and 2 h for clear fluids. Recently, this has changed to the 6-4-1 rule in many countries and is discussed below.
5.2.1 Clear Fluids
Clear fluids include drinks that contain no fats or solids, such as clear apple juice, cordial, lemonade and pulp-free orange juice.
Many centers are moving away from a 2 h clear fluid fasting time, instead encouraging children to consume clear fluids (up to 3 mL/kg) until 1 h before elective or minor emergency surgery (the 6-4-1 rule). This is safe and does not increase the incidence of aspiration. Some centers accept even shorter fasting times (using a 6-4-0 rule).
Milk is cleared from the stomach in a biphasic pattern—an initial phase of rapid clearance of liquid followed by a slower phase of clearance of solids.
Gastric emptying times vary between milk products and depend on protein (whey and casein) and fat content. Breast milk has a higher whey-to-casein ratio than other milks and empties faster from the stomach. Because of this, many centers accept shorter fasting intervals for breast milk than other types of milk. Cow’s milk is rich in casein and fat, and empties slowly. Formula milk is intermediate in composition and emptying time.
While there is consensus about fasting periods with clear fluids, this is not the case with milk, and there is variation across different regions. A fasting duration of 3 h for breast milk and 4 h for formula is commonly used for infants, with fasting increased to 6 h for all types of milk in children 1 year and older.
Fasting times for children
3 h if <12 months age
4 h if <12 months age
Solids, cow’s milk
Different types of milk have different fat and protein contents, and the fasting duration after ingestion of each type is different.
Solids tend to have variable gastric clearance times. Emptying may be prolonged with increasing fat and calorie content and the size of the meal, and the 6 h duration generally applies only to a ‘light’ meal.
In children with traumatic injuries, the time to complete gastric emptying is unknown. However, not all of these children need to be treated as if they have a full stomach. Factors that affect gastric emptying include the severity of trauma, pain, anxiety, administration of opioids and the time interval between trauma occurring and last meal.
5.2.4 Unusual Foods
Food that becomes liquid in the stomach (jelly, icy poles, and lollipops) can be considered the same as liquids. Chewing bubble gum is also considered a clear liquid for fasting, but if it is swallowed, it is treated as a solid. Fluid thickeners do not alter gastric emptying and fasting times should be determined by the type of fluid they are used to thicken.
Rare conditions affected by fasting:
Glycogen storage diseases, Fatty acid oxidation disorders, Urea cycle defects, Organic acidurias (including MMA), Homocystinuria.
5.3 Intravenous Fluid Requirements
There are three components to fluid management in children: replacement of existing deficits, maintenance requirements, and replacement of ongoing losses.
5.3.1 Replacement of Existing Deficits
Fluid deficit can cause dehydration or shock, and may be due to hemorrhage, gastrointestinal losses, insensible losses or sequestration from the intravascular space into tissues. These deficits can be estimated from weight loss, clinical signs and laboratory investigations.
Signs and symptoms of dehydration and shock in children
Signs and symptoms
Looks unwell or deteriorating a
Altered consciousness: lethargy, restless a
Decreased skin turgor a
Sunken eyes a
Tachycardia, then bradycardia
Increased respiratory rate a
Increased or decreased respiratory rate
Normal skin color
Mottled skin, pale
Dry mucous membranes
Normal blood pressure
Capillary refill <2 s
Capillary refill >3 s
Normal peripheral pulses
Reduced peripheral pulses
Reduced urine output
Dehydration may be detectable when a child is 2.5–5% dehydrated. Severe dehydration causes circulatory shock, and the child may become acidotic and hypotensive. Hypotension is a late, premorbid sign because young children are able to mount a strong sympathetic response and maintain blood pressure until severe hypovolemia develops. Clinical signs, serum electrolytes and glucose can guide replacement.
If a child is 5% dehydrated, this means they have lost 5 mL per 100 g of body weight, or 50 mL/kg.
Clinical dehydration is detectable when a child is 2.5–5% dehydrated.
If a child presents with symptoms and signs of dehydration in the absence of shock, they are approximately 5% dehydrated.
If shock is present, there is at least 10% dehydration.
The capillary refill time—Pressure on the skin for 5 s then observe the time for blanching to disappear. Normal refill time is 2 s or less. 2–3 s is borderline abnormal. The finger is the best site, the sternum is an alternative. Refill times are longer in the foot. Refill time doesn’t correlate with blood pressure, reflecting the child’s ability to maintain BP until late.
Skin turgor—Gently pinch a fold of skin for a few seconds and let go. Normally, the skin will recoil to its original position instantly. A delay in return to normal suggests dehydration. In a child, the best place to test skin turgor is on the abdomen.
If the child has signs of shock or is at increased risk of developing shock (presence of red flags), 10–20 mL/kg of an isotonic crystalloid solution should be given immediately. A further 10–20 mL/kg bolus may be given if signs of shock persist. Judicious fluid boluses of 5–10 mL/kg should be used in cardiac disease and severe trauma.
After resolution of signs of shock, rehydration should occur with an isotonic crystalloid +/− glucose. 100 mL/kg (ie. 10% dehydration) should be given over 24–48 h in addition to maintenance fluid requirements.
For children presenting with dehydration in the absence of shock, 50 mL/kg (ie. 5% dehydration) of an isotonic crystalloid +/− glucose should be given over 24–48 h in addition to maintenance fluids.
5.3.2 Maintenance Fluids
Maintenance fluids replace fluid and solute losses from the kidney, gut, respiratory tract and skin. Approximately 50% of the losses are from the renal system and 50% from the lungs and skin. Maintenance fluid requirements are a function of metabolic rate and caloric requirements, and so are higher in neonates than in children and adults. They are also higher in the presence of fever, burns, or sepsis.
The 4-2-1 formula for calculating hourly maintenance fluid requirements of children
Fluid rate (mL/kg/h)
First 10 kg
Next 10–20 kg
Part of weight over 20 kg