The skull is a rigid container for the brain with a volume of about 1500 cc. The contents consist of brain
parenchyma (80%), blood (10%), and cerebrospinal
fluid (CSF) (10%). When injured, the brain swells, and
because of the noncompliance of the skull, intracranial pressure
(ICP) rises quickly. Treatment for ICP includes drugs that decrease
the size of neurons (ie, mannitol, diuretics), drugs to put the
brain to sleep (ie, barbiturates), hypothermia, brain resection,
and craniectomy. The placement of a catheter in one of the ventricles
permits both ICP monitoring and CSF drainage to reduce intracranial
pressure. There are several alternative approaches to ICP monitoring,
including intraparenchymal, subarachnoid, and epidural monitors.
The latter tend to be less reliable than intraventricular monitors and
preclude CSF drainage.
- ▪ CPP: Cerebral perfusion pressure (mean arterial pressure minus ICP).
- ▪ CBF: Cerebral blood flow which is normally autoregulated
should have a CPP value between 50 and 150 mm Hg.
- ▪ Ventriculostomy: Placement of a catheter in one of the
brain ventricles through a small “burr hole” in
the skull (Figure 15-1).
- ▪ Intraventricular monitor—considered to be the “gold
standard” ICP monitor
- —Relatively high infection rate
- —Accurate and reliable
- ▪ Intraparenchymal monitor—a fiberoptic transducer placed in
the brain parenchyma
- —Low infection rate
- —Tendency to “drift” over time
- ▪ Subarachnoid—fluid-coupled transduction of pressure on subarachnoid
- —Low infection rate
- —Tendency to clog with debris
- ▪ Epidural—optical transduction of dural pressure
- —Tend to be inaccurate because pressure is damped
- —May be used in coagulopathic patients
Diagram of ventriculostomy catheter in lateral ventricle.
- ▪ The following procedures should be performed prior to the
- —Obtain informed consent.
- —Wash hands, gown, and glove, prepare, and drape
site as described in Section I.
- —The hair surrounding the site should be clipped
- ▪ Craniotomy
- —The skin over the selected site is anesthetized
with local anesthesia (typically the nondominant hemisphere).
insertion point is 1 cm anterior to the coronal suture in the mid-pupillary
- —A small incision is made in the skin down to the bone.
- —A burr hole is made in the skull (Figure 15-3).
- —The dura is then opened.
- ▪ Ventriculostomy
- — The catheter is passed through the dura and advanced, approximately, 7 cm ipsilateral
eye and the from the tragus of the ear to the incision point toward
the ipsilateral foramen of Monro (Figures 15-4, 15-5, 15-6, and 15-7).
- ▪ Correct intraventricular position can be verified by the
free drainage of CSF through the catheter.
- ▪ The intraventricular catheter is attached to a transducer
to permit waveform and pressure monitoring, as well as stopcocked
to allow intermittent CSF drainage.
- ▪ Normal ICP is less than 20 mm Hg.
- ▪ ICP should be treated (reduced) ...
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