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1134 PART 10: The Surgical Patient

administration of mannitol may be preferable to continuous infusion. Decompressive craniectomy (DC) is the removal of a bone flap (eg,
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There is concern that the prolonged use of mannitol (eg, >24 hours) hemicraniectomy, or bifrontal craniectomy) in an effort to reduce ICP
may result in mannitol crossing the BBB into the brain where it may by providing more space for brain expansion. DC is associated with such
cause reversal of osmotic shifts leading to ineffective ICP control or complications as hydrocephalus and hygroma (a subdural collection of
frank elevation of ICP; however, there is a paucity of data on the use of CSF) formation and also requires a second operation to reconstruct
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continuous mannitol in patients with IH. 79,166,167 When giving repeated the cranial defect. The bone can be stored in a subzero freezer or the
boluses or continuous infusions of mannitol, the fluid balance, blood subcutaneous fat layer of the abdominal wall, the latter providing good
pressure or hemodynamics, and the serum osmolality must be carefully substrate to maintain vascularity and bone viability through recruitment
monitored. Immediately after bolus administration of mannitol, the of blood supply to the diploic space.
intravascular volume is increased, but subsequently mannitol causes an DC, a more controversial method of ICP control, may be beneficial
osmotic diuresis that can result in hypovolemia and hypotension. Excess when there is intractable intracranial hypertension resulting in a high
dosing, that is, serum osmolality >320 mOsm/L, should be avoided 166,167 burden of intensive care required to maintain cerebrophysiological
and mannitol held until the serum osmolality drops below this level. parameters, for example, vasoactive drugs, barbiturates, hypothermia.
There is class III evidence that mannitol is superior to barbiturates in DC was first introduced for the initial management of acute subdural
improving CPP, ICP, and mortality. 166,168 hematomas in severe TBI patients by Ransahoff et al in 1971 when
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35 patients underwent unilateral skull removal and opening of the dura
Hypertonic Saline: Bolus administration of hypertonic saline has after subdural evacuation. The survival rate in these patients increased
been found, in a randomized prospective clinical trial, to effectively from 15% to 40% with 28% achieving functional outcomes. Most
reduce ICP without exacerbating IH in patients after TBI. After patients had pupillary abnormalities and exhibited posturing, such pre-
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polytrauma, a subgroup of patients with TBI given hypertonic saline/ sentations often being associated with dire prognoses. After a promising
dextran appeared to maintain or improve hemodynamics. In start, a follow-up study by Cooper et al showed that in 50 patients
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TBI, hypertonic saline and mannitol boluses appear to be equally effi- treated since 1971, the mortality was 90% with only 4% functional
cacious in the acute reduction of ICP. In a recent randomized, blinded survival. Further, in 1979, Cooper et al reported a study involving cra-
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study of patients with severe TBI, using an alternating treatment niectomies in dogs subjected to cryogenic lesions and found improved
protocol, equivalent bolus doses of either mannitol (20%; 2 mL/kg) ICP control but “…at the cost of enhanced edema production.”
or hypertonic saline (15%; 0.42 mL/kg) were administered for ele- Afterward, DC fell out of favor. These studies were conducted in an era
vated ICP. With each subsequent ICP elevation, the treatments prior to the management of patients according to cerebrophysiological
were alternated. Data on 199 separate ICP elevations in 29 different parameters and may, at least in part, explain why there was little effect
patients revealed an equivalent reduction in ICP obtained with man- on survival.
nitol (7.96 mm Hg) versus hypertonic saline (8.43 mm Hg). 171 Within the last 15 to 20 years, there has been resurgence in the
The mechanism of action of hypertonic saline is likely similar to craniectomy procedure with more promising evidence for its utility
mannitol in regard to increasing the osmotic gradient across the BBB and effectiveness in TBI. Unlike the randomized studies that exist for
resulting in water egress from brain tissue, reducing cerebral volume and malignant ischemic stroke patients, 179-181 most of the evidence for DC
hence ICP. Hypertonic saline also causes plasma volume expansion after TBI is class III with only one large randomized trial completed and
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and it has been proposed that volume expansion along with reduced the other in progress. In 2006, a Cochrane review concluded that due
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leukocyte adhesion, increased red cell deformability and shrinkage of to a lack of randomized, controlled trials, DC cannot be recommended
endothelial cells results in increased blood vessel diameter and improved for routine use in adults, but another small randomized trial in children
microcirculatory flow. Hypertonic saline may effectively lower ICP in may indicate a positive effect in cases with intractable IH. The good out-
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patients refractory to mannitol and repeat boluses result in ICP reduc- come rate was 54% versus 14% with greater ICP reduction in 27 children
tion without rebound increases in ICP. 166,172 Small numbers of patients undergoing early DC as opposed to medical management. Among
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and inconsistent methods between studies make comparisons uncertain; retrospective studies, 50 consecutive severe TBI patients, 40 of whom had
however, a recent meta-analysis of eight prospective RCTs showed a intractable IH and underwent DC and DC lowered ICP to <20 mm Hg
higher rate of treatment failure with mannitol or normal saline versus in 85% of patients and was associated with better-than-expected func-
hypertonic saline infusion. 173 tional outcome compared to historical controls. Williams et al
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The risks of hypertonic saline infusion include hypernatremia, fluid reviewed 171 patients who underwent DC for severe head injury at a
overload, pulmonary edema and, in patients with preexisting hypona- single institution and found a 32% mortality rate with good outcome in
tremia, central pontine myelinolysis. In adults the role of continuous 82% of survivors (55% of all patients).
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infusion of hypertonic saline after TBI has not yet been established ; DC has demonstrated effectiveness in decreasing the burden of
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however, we routinely employ a continuous 3% saline infusion with intensive management, or the “therapeutic intensity,” in severe head
a therapeutic serum sodium goal of 140 to 145 mEq/L on admission injury patients. 185,186 However, in 2011, the first of two randomized,
after moderate and severe acute TBI to prevent potentially harmful and controlled trials for DC in TBI was published. The DECRA trial studied
commonly seen posttraumatic hyponatremia.
155 patients with severe diffuse TBI and intracranial hypertension
treated early (within hours) with bifrontal craniectomies. While
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■ OPERATIVE MANAGEMENT OF TBI the ICP and ICU length of stay was decreased, DC patients exhibited
AND DECOMPRESSIVE CRANIECTOMY more unfavorable outcomes at 6 months. The craniectomy cohort had
a higher incidence of pupillary nonreactivity and, after adjustment for
Evacuating mass lesions, such as subdural and epidural hematomas this parameter, the outcomes in the medical versus surgical groups were
and large intraparenchymal hematomas, has long been a mainstay of not statistically significant. The mortality rates for both groups were
TBI management. Such evacuation can be an important first step in comparable. This trial has come under criticism for the use of a 20-mm Hg
controlling devastating IH by decreasing midline shift and reducing treatment threshold for ICP, this level is thought to be too low to immedi-
excessive volume within the closed cranial cavity that occurs after the ately proceed with craniectomy, and the higher incidence of nonreactive
primary injury. Occasionally, surgical decompression may be performed pupils in the DC group introducing a selection bias. However, one can
in a delayed fashion due to flourishing of cerebral contusions, edema conclude that bifrontal craniectomy for diffuse severe head injury in
surrounding existing contusions, or generalized swelling as a result of the early treatment of IH should be performed with caution and greater
secondary brain injury. Depressed skull fractures often require eleva- attention should be paid toward optimizing medical parameters prior
tion. Diffuse or disseminated injuries, such as diffuse axonal injury and to surgery. A potential alternative is performing a unilateral hemi-
contusional injury, typically are not managed surgically. craniectomy on the nondominant side in the absence of radiographic

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