NEUROPROTECTIVE STRATEGIES
Praveen Khilnani *
MD FAAP FCCM, Senior Consultant, Pediatric Intensivist, IP Apollo Hospital, New Delhi. *
Raised Intracranial pressure is a common occurrence in comatose patients. Neuroprotective strategies are meant to maintain cerebral perfusion pressure (CPP) to reduce mortality and morbidity.

Cerebral perfusion pressure (CPP):
CPP is the difference between mean arterial blood (MAP) pressure and the intracranial pressure (ICP).

Cerebral autoregulation: Cerebral blood flow (CBF) can be maintained over the wide range of 60-120 mm of Hg of MAP by autoregulation of the cerebral vascular tone but such autoregulation is impaired in traumatic brain injury and ischemia. Hypertension and bradycardia occur commonly with increased ICP (Cushing's triad) as a physiological reflex to maintain CBF.

Munroe Kelly doctrine:
In rigid skull, volume of the skull remains constant, thus any additional volume such as blood, tumor, edema will lead to increased ICP reducing the CBF. Therefore a localized lesion may result into midline shift and diffuse lesion may lead to tonsillar (brainstem) herniation and brain death.


Factors reducing MAP Factors increasing the ICP

Hypotension (hypovolemia, blood loss), septic shock, neurogenic shock

Hypoxemia and hypercarbia (cerebral blood flow) space occupying lesion, blood, tumor, abscess, obstructive hydrocephalus, cerebral edema (injury, infection, drugs - succinyl choline, ketamine), tumors, ketoacidosis, ischemia, hyperthermia, seizures, cough, suction, pain, high PEEP, intrathoracic pressure, intraabdominal pressure.


Neuroprotective strategies: They are aimed at prevention and definitive treatment of factors listed in the table.

Treatment of the primary condition: i.e. extradural or massive subdural hematoma, hydrocephalus, tumor or other space occupying lesion need neurosurgical intervention.

Indications of intubation: Children with GCS <8 (various causes), resistant seizures or refractory status epilepticus, posturing (decerebrate or decorticate) should be intubated for airway protection and maintenance of normal oxygenation and ventilation.
  • Avoid awake intubation because cough, gag, pain can raise ICP, Jaw injury, teeth breakage and laryngospasm can occur.
  • Use midazolam, propofol or barbiturates such as thiopentone. Avoid succinyl choline, use nondepolarizing muscle relaxant such as vecuronium, spray the vocal cords with local anesthetic 2% xylocaine.

Precautions during Intubation:
  • Avoid awake intubation because cough, gag, pain can raise ICP, Jaw injury, teeth breakage and laryngospasm can occur.
  • Use midazolam, propofol or barbiturates such as thiopentone. Avoid succinyl choline, use nondepolarizing muscle relaxant such as vecuronium, spray the vocal cords with local anesthetic 2% xylocaine.
Mechanical ventilation:
  • Volume / pressure limit cycling (both equally good).
  • Keep paCO2 between 30-35 Torr and normal PaO2. Hyperventilation to 25-30 Torr of PaCO2 is recommended for acute increase in ICP in traumatic brain injury. Hyperventilation to below paCO2 of 25 Torr is not recommended.
  • Avoid high PEEP to prevent cerebral venous pressure from rising venous pressure indirectly leads to - ICP
  • Avoid cough, gag, excessive suctioning, painful stimuli and vigorous physiotherapy.
  • Give adequate sedation and muscle relaxation as necessary.
Position:
Midline head and 45 degrees elevation (reduces venous pressure and congestion and also reduce intrathoracic pressure by pushing the diaphragm down).

Maintenance of circulation (MAP): Aggressive treatment (fluid therapy / blood products) to maintain a normal MAP. Ionotropes and vasopressors may also be used. Fluids overload and excess vasopressors can cause hypertension increasing the ICP by increasing the cerebral blood flow.

Avoid hyperthermia:
Increases CBF and hence brain oxygen requirement. On the other hand induced hypothermia has been shown to reduce the CBF and also oxygen requirement.

Osmotherapy:
Mannitol and hypertonic saline (limited pediatric data) have been used to reduce cerebral edema by osmotic effect.

Steroids:
Not recommended (except in cerebral edema due to tumors) for traumatic brain injury or diffuse encephalitis. (steroids are indicated in TBM, H influenzae meningitis and as a stress dose in septic shock).

High dose barbiturates:
Pentobarbitone, thiopentone or propofol drip can be considered in refractory raised intracranial pressure> 20-25 in traumatic brain injury. In such patients with refractory intracranial hypertension ventriculostomy / decompression craniectomy has been recommended in traumatic brain injury.

ICP monitoring:
No evidence to show that ICP monitoring changes the ultimate outcome.

Guidelines (1) - evidence highlights:
  1. Pediatric patients with Traumatic Brain Injury (TBI) should be treated in a pediatric trauma center or failing that, a tertiary care hospital with pediatric trauma care capability.
  2. Hypoxia must be treated appropriately; however, there is no evidence to support endotracheal intubation versus bag-mask ventilation during transfer to the hospital.
  3. Prophylactic treatment with mannitol or mild hyperventilation is usually unnecessary but should be used in patients with evidence of cerebral herniation or worsening neurological function.
  4. Intra cranial pressure monitoring is indicated for children with a Glasgow coma score of less than 8, but it may also be employed for children whom serial neurological examination is not feasible.
  5. Treatment for increased intracranial pressure should be initiated when the pressure rises more than 20-25 mm Hg.
  6. The sensitivity of ventricular catheters, external gauge transducers, or catheter tip pressure transducers in monitoring intracranial pressure appears equal. Subarachnoid, subdural, epidural, and externally placed monitors are less accurate.
  7. Cerebral perfusion pressure should be maintained at more than 40 mm Hg. Further research is needed to determine an optimal cerebral perfusion pressure range.
  8. The routine use of sedation and neuromuscular blockade in severe pediatric traumatic brain injury is not supported by scientific evidence.
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