Page 1163 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

802 PART 6: Neurologic Disorders

very likely that the scope of clinical practice depends on location, and Third, the degree of brain injury among the study patients may already
more decentralized areas within South America are likely to be dissimi- have been severe enough that potential improvements based on ICP mon-
lar to those found in North America and Western Europe. De Silva et al itoring would not impact outcome. Future research could focus on iden-
showed that 6-month outcome among severe traumatic brain injuries tifying distinct subgroups of severe TBI patients who are likely to benefit
was associated with a higher (51%) mortality in low- and middle- from multimodal brain monitoring with optimizing ICP and other brain
income countries compared to the mortality in high-income countries parameters. Lastly, the device used to measure pressure in the study
(30%). 36,37 Important treatment differences between continents as well participants was the intraparenchymal ICP monitor, unlike the external
as between individual South American centers and among patients (eg, ventricular drains used in many American and European NeuroICU set-
quality of prehospital stabilization efforts) may have induced significant tings. Ventricular drains not only allow CSF drainage to reduce ICP, but
bias in addition to contributing to worse overall outcomes. Furthermore, also measure ICP in the center of the skull, closer to important brainstem
initial hospital emergency care and access to rehabilitation were not and diencephalic structures, reducing artifact and missed ICP elevations
considered in the study. more commonly seen with the more superficial hemispheric measure-
Second, even though the intensivists treating the study participants ments of intraparenchymal monitors. In this study, all efforts were directed
would routinely manage severe TBI patients, there was a lack of prior toward lowering pressure within the cranium, but clinical outcome in
experience and skills in inserting ICP monitors, dealing with ICP survivors also reflects involvement of specific areas of compression, nota-
equipment, interpreting and trending the ICP values, understanding bly, the upper midbrain, thalamus, and reticular activating system.
ICP waveform morphologies, and correlating ICP findings with imag- Other recent systematic reviews on ICP monitoring emphasize
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ing and clinical results. Furthermore, the time from primary injury to that the outcome of severe TBI patients depends on guideline-driven
placement of ICP monitor was not considered, and some patients may management integrating various monitoring elements, and demon-
therefore have already suffered from secondary brain injury on inclu- strates that utilizing an ICP monitor alone does not result in better
sion in the study. In addition, there is variability in the decision-making clinical outcome. In comparison, a study by Barmparas et al showed
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process and surgical management of elevated ICP, that is, immediate that decreased use of ICP monitoring in trauma patients was associated
surgical decompression via hemicraniectomy versus isolated placement with increased mortality. An explanation for these variable results is
of intracranial pressure monitor. Importantly, the trial did not integrate that alteration of a single parameter (eg, ICP) may not be expected to
brain tissue oxygen tension, cerebral blood flow monitoring, brain tem- significantly impact overall outcome. We recommend that ICP should
perature modulation, and other treatment modalities commonly used be treated as an important vital sign but that its values must be care-
in modern neurocritical care units to treat severe TBI patients. Also, fully integrated into the moment-to-moment clinical and coparameter
monitoring for vasospasm in the setting of subarachnoid hemorrhage settings. The concept of managing patients focused on “one ICP value
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or contusion was not performed. As many as one-third of all severe TBI fits all” may only be a part of a more complex strategy in dealing with
patients can develop arterial vasospasm detected on TCD or CTA, and complicated cases such as acute brain injuries; therefore, management
its incidence and risk for ischemia can readily abolish an ICP treatment should be tailored to the specific requirements of the individual patient
efficacy given the rather small study sample. In addition, the use of a making use of other multimodal monitoring. 38
universal, absolute ICP treatment threshold may not be of such great
CPP-targeted therapy (ie, between 60 and 70 mm Hg) has been shown ■ PLACING ICP MONITORING DEVICES
importance as integrating the ICP values to obtain optimal CPP. Of note,
to be of high importance in improving outcome in moderate to severe ICP can be monitored from several intracranial sites (Fig. 86-16).
TBI as mortality takes on a U-shape form for values below and above The most commonly employed ICP monitoring devices are ventricu-
this range. The protocol used in the study under discussion was to raise lar catheters and intraparenchymal monitors 42-44 . External ventricular
the MAP and/or decrease ICP ≤20 mm Hg but not necessarily targeting drains (EVDs) are considered the gold standard for ICP monitoring,
specific CPP goals as recommended. predominantly because of their reliability and the added ability to drain

Intraventricular Skull Epidural Lateral ventricle
(anterior horn)

Intraparenchymal
Subarachnoid
Subarachnoid
space

Dura mater

FIGURE 86-16. Various anatomic sites to monitor intracranial pressure and different modalities of ICP monitoring. Intraventricular device with external ventricular catheter drain (EVD)
allows accurate measurements and drainage of CSF for treatment and culture. Intraparenchymal devices are inserted into the cortical-subcortical brain region, also allow reliable ICP monitoring
especially with collapsed ventricles. In addition, it is less invasive and has low infection rate but CSF drainage is not possible. Subdural, subarachnoid and epidural ICP monitoring are inaccurate
and unreliable methods.

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