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26 Fluids and Electrolyte Therapy in the Paediatric Surgical Patient
Table 5.4: Signs and symptoms of dehydration. cardiovascular instability are all symptoms commonly seen when a
4
paediatric patient has severe dehydration. Some common surgical
Percent of body Signs and symptoms of dehydration
weight paediatric issues that can cause severe dehydration include bowel
obstruction, acute burns, intestinal perforation, myelomeningocele
• History of 12–24 hours of vomiting and diarrhoea (open), and trauma. Table 5.4 presents signs and symptoms of dehy-
1–5% (mild) • Dry mouth dration by percentage of body weight. 5
The compensatory mechanisms for dehydration that are seen in the
• Decreased urination
adult population are less well defined in the term infant and even less so
• Tenting skin in the preterm infant. The body’s primary mechanism for compensation
is the renin-angiotensin-aldosterone system, which attempts to absorb
• Sunken eyes, fontanelle
6–10% (moderate) sodium and water. Renin is released from the kidneys, which then
• Oliguria prompts the release of aldosterone and ADH, which then allows
• Lethargy for the water and sodium to be reabsorbed. The newborn is able to
allocate some of the extracellular fluid to the plasma volume, but this
• Cardiovascular instability: mottling, hypotension, compensation is limited and will result in the loss of skin turgor. The
tachycardia newborn’s cardiac output is determined by the heart rate because the
11–15% (severe)
• Anuria intrinsic heart muscle is noncompliant, therefore making the adjustment
• Sensorium change in preload volume very difficult. If a patient arrives in a state of severe
dehydration and shock, then the infusion of 20–30 ml/kg of normal
• Coma saline must be started while others monitor for the improvement in
20%
• Shock fluid status. Urine output and concentration (appearance) will be
the most accurate and cost-effective measurements that will allow
for the monitoring of the overall fluid status. The placement of an
Glucose Requirements intraossaeous line is now preferred if a peripheral intravenous line
Carbohydrate reserves are relatively low in the newborn and certainly cannot be placed quickly during the resuscitation time in a severely
will drop to low levels during the prolonged labour course often seen in dehydrated child. Studies have shown that normal saline is as good a
some areas of Africa. Thirty percent of the glucose reserves are stored volume resuscitator as any fluid available (Table 5.5), and it certainly
as glycogen in the liver, but this cushion is less evident in the low-birth- is cost effective; therefore, there is no need to use the more expensive
weight or preterm infant. Within the first four hours of life, the newborn colloids during fluid resuscitation.
must be given some form of glucose. With prematurity and a gestational NPO Period in the Paediatric Population
age of less than 34 weeks, the ability to swallow is low, so the patient There has been considerable debate about NPO status in children, and
may need an intravenous (IV) line or a feeding tube. Adequate and NPO guidelines have undergone adjustment. At this time, we no longer
frequent measurement of the glucose levels of the newborn, especially use the former prolonged times that once produced surgical patients
the newborn pending surgery, is cost effective and will help manage the who were relatively volume depleted upon the start of surgery. It has
hypoglycaemia and hyperglycaemia episodes that may harm the infant. been shown that clear liquids given 3 hours before surgery results in a
Children who are small for gestational age (SGA), have chronic lower gastric volume and no change in gastric acidity. A clear liquid
illnesses, had a prolonged NPO (nothing by mouth) period, premature is one that has no particulate matter, which means that you can see
infants, and infants of diabetic mothers are all at risk for hypoglycaemia through the fluid if held up to the light without obstruction.
during their hospital course. In SGA infants, hypoglycaemia usually Infants who are on formula need 6 hours, and breast-feeding infants
occurs 24–72 hours after birth, when the glycogen stores are depleted and need 4 hours, at our institution in Kenya, but at some hospitals this
the breast milk production may not yet meet demand. In Kenya, we use D would be considered a “clear” liquid and only 3 hours are required for
10 (80 ml) mixed with normal saline (NS; 20 ml) in a buretrol of 100 ml NPO. These modifications have allowed for situations in which the
and then begin our maintenance fluids and monitor blood glucose levels. children’s veins are more distended and, hopefully, children and parents
The 60 drops per ml buretrols allow us to give the appropriate volume of who are happier during the preoperative period. The type of surgery and
fluids, which will prevent volume overload (never place more than the reason for the surgical intervention will also dictate the ability to take
volume for 4 hours of maintenance fluids in the buretrol) while adapting fluids by mouth. Many neonates who need emergency surgery have
the amounts of dextrose and normal saline based upon basic lab values. never been on any fluids, and NPO is not an issue, but if the patient has
Glucose level instability is commonly seen in those patients who are a bowel obstruction, for example, then the need for a rapid sequence
septic or have had a period of hypotension or asphyxia. These patients induction (anaesthesia) may override any NPO concerns.
need close monitoring every hour in the operating theatre to adjust Intraoperative Fluids
glucose levels; they all need glucose in their operative fluids to prevent The calculation of intraoperative fluid requirements can be allocated
the severe complications associated with hypoglycaemia. Intraoperative into the following sections: maintenance fluids, preoperative fluid defi-
glucose administration is controversial but, in general, 5% dextrose is cit, insensible losses, and estimated blood loss (Table 5.6). Maintenance
adequate because the metabolic stress response to surgery will avoid the fluids per hour required based upon a patient’s weight was discussed
patient becoming hypoglycaemic. Neurosurgical cases need very close earlier; typically, normal saline or Ringer’s lactate are the fluids of
glucose control due to cerebral ischaemia issues and hyperglycaemia.
choice, as they most closely represent the plasma components. The
Perioperative Fluid and Electrolyte Management preoperative deficit will be the patient’s weight in kilograms multi-
Dehydration plied by the number of hours without any fluids. The insensible losses
depend upon many factors, but primarily will be based upon the size of
The severity of dehydration should be estimated based upon the his-
the incision and whether exposure of the bowel or viscus is involved,
tory and clinical findings. There are no unique lab values that can
as this will increase fluid loss (see Table 5.6). The estimated blood loss
accurately determine the severity of dehydration, but certainly an
needs to be replaced as well, with a ratio of 3 ml of normal saline for
experienced medical care provider becomes adept at the estimation
every 1 ml of blood loss.
of dehydration in the paediatric population. Oliguria, lethargy, and