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Anaesthesia and Perioperative Care 57

induction begins. All equipment, including the anaesthetic machine, and children, the higher oxygen requirements per kilogram produce
must be checked and confirmed to be working properly. hypoxia more rapidly when there is airway obstruction. Perioperative
Adequate preoperative preparation (including building rapport with paediatric airway obstruction occurs commonly when the conscious-
the patient) and the rational use of premedication will facilitate safe and ness level is depressed and the airway is not properly positioned to
2
atraumatic induction of anaesthesia. maintain its patency.
Induction of Anaesthesia Airway Maintenance Equipment
Like premedication, induction of anaesthesia should be tailored to Paediatric airway equipment is usually designed to minimise trauma,
the individual patient. The same factors used to determine suitable dead space, airway resistance, and rebreathing. Equipment for airway
premedication come into play when choosing an induction method. maintenance includes face masks (Figure 10.1), oropharyngeal and
Inhalational and intravenous routes of induction are more common than nasopharyngeal airways (Figure 10.2), breathing circuits and Ambu
rectal and intramuscular routes, although ketamine can be used in the bags, laryngoscopes, endotracheal tubes, and laryngeal mask airways.
paediatric population when an IV line is not in place or not needed for Face Masks
a very short procedure such as a dressing change.
Because of their fear of needles, inhalational induction is most Face masks come in different sizes (00 for neonates, 0 for infants, 1 for
common for children up to 10 years of age (and perhaps even well into small children, 2 for bigger children), shapes, and colours (see Figure
the teenage years) who are undergoing elective surgery. This method 10.1). The neonatal face mask has minimal dead space and is designed
is particularly useful because inhaled anaesthetic drugs increase in to limit rebreathing. It must fit closely over the mouth and nose without
concentration in the alveoli of children more rapidly than they do obstructing the nares.
in adults. Inhalational induction should be a slow, smooth process Breathing Circuits
with care taken to keep the airway patent at all times. Sevoflurane The Ayre’s T-piece breathing circuit (Figure 10.3) is used for children
is replacing halothane as the agent of choice because it appears to weighing less than 20 kg because it is a low-resistance circuit. For
have fewer cardiovascular side effects while being faster in onset and children weighing more than 20 kg, an adult circuit (Bain or Magill)
recovery. However, many anaesthesia care providers in developing can be used. The Ayre’s T-piece can be used for both spontaneous and
countries may not have access to sevoflurane, and halothane will be assisted ventilation.
the available agent. Halothane in the hands of a trained paediatric
anaesthesia care provider will allow for a very smooth induction
with the patient ventilating spontaneously, but very careful cardiac
monitoring needs to be vigilantly performed.
Intravenous induction is the method of choice when there is a pre-
existing IV or when inhalational induction is contraindicated (e.g.,
in the event of trauma or any full stomach scenario). Thiopentone,
ketamine, and propofol remain the main induction agents. Etomidate,
when available, can also be useful. Intramuscular induction is often
used in the older uncooperative child who cannot be reasoned with, Figure 10.1: Various sizes of paediatric masks.
such as a child with autism or mental retardation. In settings where
resources are limited, intramuscular ketamine can be useful for very
short procedures such as circumcision and wound debridement.
If the patient is cooperative, monitors are applied before induction;
otherwise, they are put on as early as possible during induction and kept
on until the patient is fully awake. The use of a precordial stethoscope
and, if available, a pulse oximeter can provide sufficient monitoring
for the induction period, allowing one to assess the airway and cardiac Figure 10.2: Oropharyngeal airway.
system with limited monitoring equipment.
Maintenance of Anaesthesia
The anaesthetic may be continued by using inhalational agents, intrave-
nous agents (including muscle relaxants and opioids), or a combination
of these agents in a balanced technique. During this stage, the airway
is kept patent by either a face mask, a laryngeal mask airway (LMA),
or an endotracheal tube.
Airway Management
One of the greatest challenges in paediatric anaesthesia is the manage-
ment of the airway, particularly in neonates. Combinations of anatomi-
cal, physiological, and developmental factors conspire to make airway
management in children more difficult than that in adults. Normal Figure 10.3: An Ayre’s T-piece.
respiratory rates are 40 per minute in neonates and 20–30 per minute in
infants. The smaller size of the paediatric airway means that any small Laryngoscopes
decrease in diameter, such as occurs from secretions, bronchconstric-
tion, oedema, or compression, may more readily lead to significant The relatively high position and inclination of the larynx in infants
airway obstruction. Respiration is mainly diaphragmatic in infants; make a straight laryngoscope blade (e.g., the Miller 0 (Figure 10.4)
therefore, any slight abdominal distention will greatly embarrass respi- or the infant Magill) a good choice, whereas children older than 1
ration. Oxygen consumption in the neonate is approximately 7 ml/kg year of age can generally be managed with a curved blade (e.g., size 2
per minute, as opposed to 3–4 ml/kg per minute in the adult. For infants Macintosh (Figure 10.5)).