Page 1169 - Hall et al (2015) Principles of Critical Care-McGraw-Hill

808 PART 6: Neurologic Disorders

platelet levels (using platelet transfusion if <50,000 per µL). The correc- indicated as the primary treatment for intracranial hypertension due to
tion of platelet and coagulation profiles is more urgent in the presence of hydrocephalus. In addition, placement of a ventricular drain allows for
an intracranial monitoring device or recent brain surgery. easy CSF sampling for cultures and administration of either antibiot-
Hyperthermia in patients with brain injury increases cerebral ics in the setting of a meningitis or ventriculitis as well as intrathecal
metabolic demand and the potential for ischemia in those with elevated thrombolytic agents (t-PA) in the setting of an obstructive intraven-
ICP. Therefore, a targeted core temperature of ~36.5°C (goal <37°C) is tricular hemorrhage. The use of an EVD in TBI patients is a common
utilized in most patients. Most commonly, hypothermia is achieved with and routine practice to provide monitoring of ICP as well as continu-
noninvasive surface cooling devices. Shivering may limit the benefits of ous drainage of CSF to reduce global elevation in ICP. CSF drainage
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cooling, since it increases metabolic demand. through lumbar puncture should generally be avoided in patients with
Nutrition is important to optimize outcome in the setting of brain intracranial hypertension.
injury. Enteral nutrition should ideally be started within 24 hours. Simultaneous CSF drainage and ICP monitoring (“leaving the EVD
Gastroparesis, which is common in neurologically injured patients, may open”) may misrepresent the actual ICP as the monitored ICP can be
impede efforts to achieve adequate nutrition. markedly different from intraparenchymal ICP. Defective CSF cycling
Endotracheal intubation with suspected or verified ICP elevation within the cranium in patients with intracranial mass lesions may lead
should follow distinct guidelines (Table 86-10). Short-acting medica- to additional ICP gradients between the parenchyma and ventricles.
80
tions (eg, propofol) at minimal doses should be used. Medications that Closure of the drainage port during measurements allows ICP gradients
potentially elevate ICP (eg, succinylcholine alone, nitroglycerin) or to equilibrate throughout the cranial vault and this timepoint is best
that produce sustained paralysis should be avoided. Succinylcholine in estimated when both a stable ICP value and waveform are visible. The
patients with chronic muscular disease or spasticity should be avoided extent of CSF drainage should be guided by the achieved control of
due to the potential for severe hyperkalemia. A physician with experi- target ICP and often, an hourly rate of 10 to 15 mL will be an effective
ence in rapid sequence intubations should be assigned as prolonged approach. Removal of a ventricular drain can be indicated when ICP has
supine positioning can increase ICP; immediate head elevation after been normal for 2 to 3 days and no elevation in ICP is seen when the
the airway is secured is essential. Patients with acute herniation requir- drain is continuously clamped. If a patient fails a clamp trial, that is, the
ing intubation may be pretreated with a mannitol bolus to reduce ICP ICP increases and/or the patient becomes symptomatic, a permanent
during the procedure. Once the airway is secured, the tube should be ventriculoperitoneal shunt is indicated.
stabilized without tight wrapping around the neck, skull fractures, or
craniectomy defects. Brain oxygen tension around the brain injury area Hyperosmolar Therapy: With the use of hypertonic solutions, moderate
is generally lower than expected from simultaneously measured arte- hypernatremia should be expected and tolerated. Mannitol, hypertonic
, and it seems prudent to allow for an extra oxygenation “safety saline solutions (HTS), and hypertonic sodium lactate (HTSL) are all
rial P O 2 effective in reducing elevated ICP in brain trauma patients as delineated

margin” to avoid borderline systemic hypoxemia, that is, keeping P O 2 in observational studies but unfortunately, there are no large random-
75 is titrated to 35 to 40 mm Hg
>100 mm Hg. Following intubation, P CO 2 ized studies to compare equiosmolar doses of different hyperosmolar
to prevent cerebral arterial dilation or constriction and the respective
risks of brain hyper- or hypoperfusion. Positive end-expiratory pressure treatments.
(PEEP) up to 12 cm H O can be used safely. 76,77 Mannitol: Osmotherapy is directed at increasing plasma osmolality
2
The initial management of raised ICP in head trauma focuses on both and establishing an osmotic gradient across the normally imperme-
normalizing the ICP and stabilizing CPP (Table 86-12). Early emphasis able blood-brain barrier. Mannitol, the most widely used osmotic
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in brain injured patients with cardiorespiratory compromise targets agent, can improve cerebral perfusion through transient hypervolemia
>60 mm Hg, systolic BP >90 mm Hg, and and hemodilution, leading to autoregulatory cerebral vasoconstriction,
2
O saturation >90% or Pa O 2
euvolemia. The CPP goal is 50 to 70 mm Hg, as CPP <50 mm Hg is decreased cerebral blood volume, and lower ICP. 81-85 Mannitol can also
associated with increased mortality 5,33,74 and CPP >70 mm Hg has not increase CSF absorption. Most brain injury, however, results in disrup-
86
been shown to improve outcome. A general approach to control ICP is tion of the blood-brain barrier and loss of normal autoregulation. As a
78
listed in Table 86-12. result, osmotic agents establish an incomplete osmotic gradient resulting
in less effectiveness in injured brain regions.
■ NEUROMEDICAL ICP MANAGEMENT treatment of elevated ICP in TBI, SAH, ICH, large cerebral infarctions,
Mannitol has been advocated as the first-line osmotic agent for the
Cerebrospinal Fluid Drainage: One of the most rational approaches and acute liver failure. 87-91 Mannitol is an effective agent for rapid reduc-
toward control of elevated ICP is to insert an EVD to release CSF. tion of ICP in an emergency setting, and it can buy time to stabilize the
However, initial imaging should clarify the ventricular size and whether patient while other treatment strategies are being prepared and planned.
there is sufficient CSF volume for drain placement. An EVD is Mannitol has been shown to improve mortality when compared to
TABLE 86-12 General Strategies in Reducing Elevated Intracranial Pressure
Intracranial Volume Reductions Decrease Metabolism Cerebrospinal Fluid Diversions Other Volume Reductions
Stabilize cerebral perfusion pressure (CPP) at 50-70 mm Hg Barbiturates External ventricular drainage (EVD) Surgical
Transient hyperventilation Analgesia Internal shunt and drainage in patients with evacuation (eg, hematoma)
Head elevation Sedation chronic CSF accumulation Surgical
Inotropics to avoid ischemia (eg, phenylephrine, norepinephrine) Paralytics decompression (eg, hemicraniectomy)
Euvolemia Anticonvulsants
Corticosteroids (eg, tumor, infection, inflammation injuries) Hypothermia
Osmotic agents (eg, mannitol, hypertonic solution)
Diuretics (eg, furosemide)
A proposed systematic approach of understanding and managing elevated ICP.

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