24.1 Introduction

Although many physicians treat children as “little adults,” a child’s physiological state is different from an adult’s, both metabolically and electrophysiologically. It should also be noted that children are in a constant state of growth that disrupts their equilibrium and necessitates adjustments. For these reasons, as well as because of the variety of disease pathologies, the treatment of children, particularly in the pediatric neurosurgical intensive care unit (NICU), requires extensive training and a degree of familiarity and comfort. Comanagement of the patient with a pediatrician or intensivist is recommended. ¹ Management of pediatric neurosurgical patients, especially after intracranial procedures, requires a multidisciplinary approach to ensure the best outcomes. This includes full disclosure of intraoperative events, postoperative prognosis and expectations, in addition to all potential complications expected. Dedicated critical care teams in pediatric intensive care units are essential. ² Pediatric neurosurgical procedures, barring an emergency, should preferably be performed with a neurosurgeon well experienced in treating children. There are special neurosurgical considerations when treating the pediatric population in an intensive care situation. ³ , ⁴

24.2 General Care Guidelines for Pediatric NICU Patients

The lack of familiarity with and misunderstanding of necessary medical treatment often frighten children and their families. Any child under the age of 16 years should be placed in the pediatric ward. Special visitation should be allowed by close family members to comfort the child. Early involvement of a child life specialist or social worker is encouraged to help with expectations and transitions, as well as to follow up on concerns. Several studies confirm the benefit of a location within the ward of a “safe haven.” This is usually the playroom or family room. Within this safe haven there should be no medical conversations, patient care checks, or treatments. ⁵ , ⁶ , ⁷

24.3 Intravenous Fluids and Electrolytes

Intracellular fluid, as a percentage of total body water, is ~ 30% at birth and increases to 40% by 1 year of life. Adequate fluid and electrolyte maintenance is needed for general health maintenance, as well as for recovery from neurologic injury (► Table 24.1). ⁸

Children have a higher body surface area to weight ratio, greater caloric expenditure, increased water losses from the skin, and a higher rate of insensible losses, leading to higher fluid requirements than adults. ⁹

There are two ways to calculate baseline fluid requirements in children. ¹⁰ The “kg method” is based on the weight of the patient, as follows:

• 
  

  For the first 10 kg of body weight: 100 mL/kg/d plus.

  
  
• 
  

  For the second 10 kg of body weight: 50 mL/kg/d plus.

  
  
• 
  

  For the weight above 20 kg: 20 mL/kg/d.

An alternative method for determining baseline intravenous (IV) fluids in children is the “meter-squared method,” which is as follows:

• 
  

  Maintenance fluids are 1,500 mL/m²/d.

  
  
• 
  

  Divide by 24 to get the flow rate per hour.

  
  
• 
  

  To calculate the surface area, use the “rule of sixes” (see ► Table 24.2) or a formal body surface area chart or equation (see discussion in Nutrition section). ¹⁰

The healthy and ideal fluid and electrolyte status of any patient is normovolemic with normal chemical balance. Of special consideration is brain injury or parenchymal edema from trauma or disease process. Like adult patients, pediatric patients with brain injury need to stay normal volemic to prevent brain edema. Sodium should stay on the high end of normal and glucose on the low end to decrease the risk of edema in patients with a broken blood–brain barrier. This rule of thumb does not hold true in endocrinological or systemic comorbidities or in spinal shock patients; these cases should treat the underlying pathology directly. ¹¹

Hyperosmolar therapy is used often in pediatric patients with traumatic brain injury (TBI). Level II evidence from pediatric TBI guidelines suggests that 3% hypertonic saline should be given at the rate of 6.5–10 mL/kg, as a continuous infusion. Level III evidence suggests the minimum dose required to maintain intracranial pressure (ICP) less than 20 to be used and to maintain serum osmolarity less than 360 mOsm. Mannitol was not recommended in these guidelines. ¹²

24.4 Respiratory Maintenance

As with adults, pulmonary function and stability must be maintained in the pediatric NICU patient. Data regarding neurologic injury secondary to hypoxia in children are sparse. In general, adult guidelines should be followed, including oxygen saturation maintenance > 95% and minimum hemoglobin and hematocrit levels of 10.0 and 33.0, respectively, realizing that the normal pediatric values vary with age but are not much higher than these minimums. Children are much more sensitive to hemodynamic shifts than adults. ¹³ , ¹⁵ , ¹⁶

The indications for endotracheal intubation are vast. The most obvious, of course, is respiratory distress or failure of any etiology. With pediatric NICU patients specifically, damage to the central nervous system (CNS) from infection, hemorrhage, trauma, hydrocephalus, or mass lesions can lead to the need for mechanical ventilation. Also, uncooperative patients, due to age, disease pathology, or closed head injury, may require temporary intubation to assist in ongoing care, including diagnosis, imaging, and treatment. Patients with cervical spine injuries should be intubated via an inline technique to minimize the risk of additional neurologic deficit. Those patients with possible or diagnosed facial trauma or anterior skull fractures should be intubated with direct visualization through the oral or nasal cavity as appropriate to minimize possible brain penetration, additional damage, or misplacement of the tubing.

Patients with raised ICP regardless of etiology may benefit from intubation. Care should be taken to intubate these patients, as the procedure itself may increase cerebral blood flow and subsequently ICP. Adequate sedation may help alleviate this problem. Under normal circumstances, cerebral oxygen requirements are coupled with cerebral blood flow, and are increased with temperature, activity, agitation, seizure, and injury. Blood flow will increase as the partial pressure of oxygen in arterial blood (PaO₂) falls below 60 mmHg or as the partial pressure of carbon dioxide in arterial blood (PaCO2) increases. NICU patients require higher PaO₂ levels and low to normal PaCO₂ levels to optimize recovery. In an acute neurologic decline, a temporary period of mild hyperventilation may help minimize edema and provide the necessary time for definitive diagnostic or treatment measures, but it should never be used as maintenance treatment of elevated ICP. ¹³ , ¹⁴

Pediatric TBI guidelines include that prophylactic hyperventilation to PCO₂ less than 30 mmHg in the first 48 hours from injury should be avoided, and if it is used then advanced neuromonitoring would be indicated to evaluate for cerebral ischemia (level III evidence). ¹²

Arterial lines should be placed on all intubated patients to provide not only reliable, easily attainable blood pressure parameters but also arterial access for blood gas analysis. Arterial blood gas analysis should be performed with every ventilator adjustment, any clinical change, and as a baseline on intubated patients twice daily.

24.5 Intracranial Pressure and Cerebral Blood Flow

Cerebral perfusion pressure (CPP) is the pressure via which blood and nutrients are delivered to the brain. As ICP increases, or mean arterial pressure (MAP) decreases, the CPP will also decrease, which will ultimately decrease cerebral blood flow. Normal cerebral blood flow in adults is 50 mL/100 g/min. Gray matter blood flow is ~ 4 times higher than that of white matter. Newborn blood flow is ~ 40 mL/100 g/min. Cerebral blood flow then increases to accommodate growth and learning. By age 4, the average cerebral blood flow is 108 mL/100 g/min and can remain as high as twice that of adults until 18 years of age. ¹⁷ , ¹⁸ , ¹⁹

An injured brain requires a fine line of adequate cerebral blood flow to maintain function, perfuse any ischemic penumbra, and heal while not increasing edema. This is where CPP plays a role. According to 2012 guidelines for acute medical management of severe TBI in infants, children, and adolescents, level III evidence suggests CPP should be kept at 40 mmHg in children with traumatic brain injury. A CPP of 40–50 mmHg can be considered, with infants maintained at the lower end and adolescents at the higher end. ¹² Tight fluid control and pressors may be needed to maintain adequate MAP in the face of rising ICP to achieve this goal.

In children, it is often difficult to measure ICP. Ventriculostomies can be used as a direct measurement; however, an accurate examination can suggest elevated ICP as well. Papilledema is often a late finding of elevated ICP in children relative to adults, whereas vomiting occurs much more regularly and reliably as a predictive symptom. Assessment of fontanelles can also yield pressure data. Note that when children are lying flat or having a Valsalva maneuver, fontanelles can be bulging and firm without abnormality. However, in the sitting position, a calm child should have soft, nonbulging fontanelles; any firmness or bulge is suggestive of elevated ICP. Another useful clinical gauge of ICP is head circumference. Although head circumference abnormalities can stem from a variety of causes, they can be used to suspect intracranial pathology and possibly high ICP, particularly if augmented by other clinical findings. An estimation of ICP is 1.5 to 6.0 mm Hg in children < 2 years of age, equal to the child’sage in the 2 to 15 year range, and 8 to 15 mm Hg in children and adults > 15 years old.

ICP monitoring is strongly supported in the pediatric population with severe TBI. Level III evidence from pediatric TBI guidelines suggest that for refractory ICP, addition of a lumbar drain can also be considered as long as external ventricular drain (EVD) is functional, cisterns are open, and there is no evidence of a mass lesion or shift on imaging. Studies have demonstrated that there is a frequently reported high incidence of elevated ICP in children with severe TBI and a high association of elevated ICP and poor neurologic outcome. Also, the best neurologic outcomes have been with protocol-based management of ICP. Level III evidence suggests that ICP above 20 mm Hg in the pediatric population is associated with a poor outcome. There are also limited data suggesting varying thresholds of ICP treatment: 0–24 months, 15 mm Hg should be threshold to treat; 25–96 months, 18 mm Hg; and 97–156 months: 20 mm Hg. ¹²

In the pediatric NICU, ICP and CPP are treated as the fifth and sixth vital signs. Evaluation, early identification of trends, and rapid treatment can prevent additional neurologic decline and improve outcome.