Neuroanesthesia

with controlled moderate hyperventilation, and many pediatric neuroanesthesiologists use nitrous oxide despite evidence that it is a significant cerebral vasodilator in children [25]. Muscle relaxants and analgesics are given as indicated. Good positioning is essential to avoid venous congestion, but positioning can be more difficult in small children as their relatively large heads and short necks can easily give rise to venous obstruction if the head is rotated.

Because of the relatively large size of the head in a child, significant blood loss is to be expected in craniotomies and excellent venous access is essential. Accurate estimation of blood loss can be difficult and the anesthesiologist may be aided by cardiovascular parameters such as heart rate, blood pressure, capillary refill time and core-peripheral temperature difference in maintaining normovolemia. Small children can become hypoglycemic during long procedures and blood glucose levels should be monitored during surgery.

Children, because they have a larger surface-area-to-weight ratio and less subcutaneous fat, can become significantly hypothermic during long operations unless active steps are taken to maintain body temperature. As with adults, the aim is for normo- or mild hypothermia. Hyperthermia is highly detrimental.

Midline posterior fossa tumors account for a significant proportion of brain tumors in children, and some pediatric neurosurgeons prefer to operate on them with the patient in a sitting position. This provides excellent operating conditions and is associated with decreased blood loss [11]. Venous air embolism (VAE) is a serious complication that must be detected and treated immediately. Nitrous oxide will equilibrate rapidly with the air bubbles and, being 30 times more soluble than nitrogen, will cause them to increase in size. If an air embolus is suspected, immediate attempts should be made to aspirate the air via a right atrial catheter. The surgeon should flood the wound with saline and the anesthesiologist should apply digital pressure to the jugular veins. This allows the site of the open vein or sinus to be identified and controlled.

Surgery for tumors in the floor of the fourth ventricle can be associated with cardiovascular instability, usually bradycardia and hypertension, owing to surgical interference with vital areas in the brainstem. This may also lead to bulbar problems post-operatively and such children may need prolonged intubation.

Craniofacial surgery often involves children who have difficult airways, and special techniques and expertise may be needed to gain control of the airway. These operations are frequently prolonged and major blood loss is likely. Post-operatively the airway may be in jeopardy from local edema and it may be safer to keep the child intubated and ventilated until the swelling has abated.

Children who are awake, warm and breathing well with no airway problems can be extubated at the end of surgery.

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