Monitoring
Monitoring requirements for infants and children are generally similar
to those for adults with some minor modifications. Alarm limits should be
appro-priately adjusted. Smaller electrocardiographic elec-trode pads may be
necessary so that they do not encroach on sterile surgical areas. Blood
pressure cuffs must be properly f ttedi. Noninvasive blood pressure monitors
have proved to be reliable in infants and children. A precordial stethoscope
pro-vides an inexpensive means of monitoring heart rate, quality of heart
sounds, and airway patency. Finally, monitors may sometimes need to be first
attached (or reattached) following induction of anesthesia in less cooperative
patients.
Small pediatric patients have a reduced
margin for error. Pulse oximetry and capnography assume an even more important
role in infants and small children because hypoxia from inadequate ventila-tion
remains a common cause of perioperative mor-bidity and mortality. In neonates,
the pulse oximeter probe should preferably be placed on the right hand or
earlobe to measure preductal oxygen saturation. As in adult patients, end-tidal
CO2 analysis allows assessment of the adequacy of ventilation, confirma-tion of
endotracheal tube placement, and early warning of malignant hyperthermia.
Flow-through (mainstream) analyzers are usually less accurate in patients
weighing less than 10 kg. Even with aspiration (sidestream) capnographs, the
inspired (baseline) CO 2 can appear falsely elevated and the expired (peak) CO2
can be falsely low. The degree of error depends on many factors but can be
mini-mized by placing the sampling site as close as possi-ble to the tip of the
endotracheal tube, using a short length of sampling line, and lowering
gas-sampling flow rates (100–150 mL/min). Furthermore, the size of some
flow-through sensors may lead to kinking of the endotracheal tube or
hypercapnia as a result of increased equipment dead space.Temperature must be
closely monitored in pediatric patients because of the greater risk
for malignant hyperthermia and greater potential for intraoperative
hypothermia or hyperthermia. The risk of hypothermia can be reduced by
main-taining a warm operating room environment (26°C or warmer), by warming and
humidifying inspired gases, by using a warming blanket and warming lights, and
by warming all intravenous and irrigation fluids. The room temperature required
for a neutral thermal environment varies with age; it is greatest in premature
newborns. Note that care must be taken to prevent accidental burns and
hyperthermia from overzealous warming efforts.
Invasive monitoring (eg, arterial cannulation,
central venous catheterization) demands expertise and judgment. Air bubbles
should be removed from pressure tubing and small volume flushes should be used
to prevent air embolism, unintended heparin-ization, or fluid overload. The
right radial artery is often chosen for cannulation in the neonate because its
preductal location mirrors the oxygen content of the carotid and retinal
arteries. A femoral artery catheter may be a suitable alternative in very small
neonates, and left radial or right or left dorsalis pedis arteries are
alternatives in infants. Critically ill neonates may retain an umbilical artery
catheter. Internal jugular and subclavian approaches are often used for central
lines. Ultrasonography should be used during placement of internal jugular
catheters and provides useful information for arterial cannu-lation as well.
Urinary output is an important (but neither sensitive nor specific) indicator
of the ade-quacy of intravascular volume and cardiac output. Noninvasive
monitors of stroke volume have only recently been tested in infants and young
children.
Premature or small-for-gestational age neo-nates, and neonates who have
received total paren-teral nutrition or whose mothers are diabetic, are prone
to hypoglycemia. These infants should have frequent blood glucose measurements:
levels below 30 mg/dL in the neonate, below 40 mg/dL in infants, and below 60
mg/dL in children and adults indi-cate hypoglycemia requiring immediate
treatment. Blood sampling for arterial blood gases, hemoglo-bin, potassium, and
ionized calcium concentration can be invaluable in critically ill patients,
particu-larly in those undergoing major surgery or who may be receiving
transfusions.
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