neurosurgical aspects of critical care neurology

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Neurosurgical Aspects of Critical Care Neurology

Edward R. Smith and Joseph R. Madsen

he management of the pediatric neurosurgical patient requires a detailed understanding of the diagnosis andanagement of disorders of ICP. Frequently the care of these patients will require collaboration between severalifferent teams of physicians. Most important, frequent and clear communication between the ICU physician andhe neurosurgeon will facilitate the delivery of the best-quality care to these children. This chapter will identify andiscuss issues relevant to neurosurgeons and intensive care physicians taking care of children with complexroblems related increased intracranial pressure.
2004 Elsevier Inc. All rights reserved.
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EDIATRIC NEUROSURGERY is a field thatcommonly focuses on operative intervention

o treat disease. However, for the neurosurgicalatient, the perioperative care is often equally im-ortant in determining outcome. Nowhere is themportance of this care more evident than in thentensive care unit (ICU).

In addition to disorders of increased intracranialressure (ICP), discussed in detail elsewhere in thisssue, the ICU physician will often be faced withiseases that may have indistinct boundaries be-ween the realm of the neurosurgeon and the realmf the intensive care physician. Although there areany possible areas of overlap, there are five

opics that merit special attention:. Management of patients with elevated ICP with

invasive monitoring or operative intervention. Management of patients in the ICU with neu-

rosurgical hardware, particularly ventricularshunts, nerve stimulators, and baclofen pumps

. Management of patients without neurosurgicalhardware but with infection that may have neu-rosurgical implications

. Management of patients with bleeding disorderswho may be at risk for spontaneous intracere-bral hemorrhage or may be considered for ICPmonitoring

. Management of endocrine disorders as theyrelate to neurosurgical disease.

NEUROSURGICAL MANAGEMENT OFPATIENTS WITH ELEVATED ICP

The indications for ICP monitoring are dis-ussed in detail elsewhere in this issue. In brief, theuidelines for the Management of Severe Head

njury suggest that ICP monitoring is indicated inomatose head-injured patients with Glasgowoma Scale (GCS) score between 3 and 8 andbnormal cranial findings on computed tomogra-hy (CT) scan.1-3 Invasive monitoring is usually
ot indicated in patients who are awake and able to
eminars in Pediatric Neurology, Vol 11, No 2 (June), 2004: pp 169-178

ollow commands. An exception to this rule occurshen an awake patient is at risk of elevated ICP

nd needs to have general anesthesia for surgery,endering clinical evaluation impossible during an-sthesia. Clinically, this may occur in patients whoave sustained trauma, have evidence of a smalletechial hemorrhage on CT, and need nonneuro-ogic surgery, such as treatment of orthopedic in-uries. In general, invasive monitoring of ICP isndicated in patients who are:4

Suspected to be at risk for elevated ICPComatose (GCS score �8)Diagnosed with a disorder that merits aggres-sive medical care.

Types of Monitors

Four main anatomical sites are used in the clin-cal measurement of ICP: intraventricular, intrapa-enchymal, subarachnoid, and epidural. Noninva-ive and metabolic monitoring of ICP has alsoeen studied, but its clinical value is unclear atresent. Each technique requires a unique monitor-ng system and has associated advantages andisadvantages.

ntraventricular Monitors

Intraventricular monitors are considered thegold standard” of ICP monitoring catheters. Theyre surgically placed into the ventricular systemnd affixed to a drainage bag and pressure trans-ucer with a three-way stopcock. Intraventricularonitoring has the advantage of accuracy, simplic-

From the Department of Neurosurgery, Children’s Hospital,oston, MA.Address reprint requests to Edward R. Smith, MD, Depart-

ent of Neurosurgery, Children’s Hospital, 300 Longwoodve., Boston, MA 02115.© 2004 Elsevier Inc. All rights reserved.1071-9091/04/1102-0000$30.00/0
doi:10.1016/j.spen.2004.04.002
169

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170 SMITH AND MADSEN

ty of measurement, and the unique characteristicf allowing for treatment of some causes of ele-ated ICP via drainage of cerebrospinal fluidCSF).

The primary disadvantage is infection, whichay occur in up to 20% of patients. This risk

ncreases the longer that the device remains inlace.5,6 Prophylactic catheter changes did not ap-ear to reduce the risk of infection.6 At our insti-ution, we have been able to leave external drainsn place safely for up to 2 weeks. All patients arereated with prophylactic gram-positive antibioticoverage and have serial CSF cultures sampledvery 2 to 3 days.

Another disadvantage of intraventricular sys-ems includes a low (approximately 2%) risk ofemorrhage during placement; this risk is greatern patients with coagulopathies. In addition, plac-ng an intraventricular drain into a small ventricleay be technically difficult, particularly in the

etting of trauma and cerebral edema complicatedy ventricular compression.7

ntraparenchymal Monitors

Intraparenchymal devices consist of a thin cableith an electronic or fiberoptic transducer at the

ip. The most widely used device is the fiberopticamino system. These monitors can be insertedirectly into the brain parenchyma via a small holerilled in the skull. Advantages include ease oflacement, and a lower risk of infection and hem-rrhage (�1%) than with intraventricular de-ices.8-10

Disadvantages include the inability to drain CSFor diagnostic or therapeutic purposes and the po-ential to lose accuracy (or “drift”) over severalays, because the transducer cannot be recalibratedfter initial placement. In addition, these monitorsarry a greater risk of mechanical failure due toheir complex design. The reliability of intraparen-hymal devices has been debated. One group foundnly a small (1 mmHg) drift in a group of 163atients;11 however, a second report found thateadings varied by more than 3 mmHg in morehan half of the 50 patients studied.12

ubarachnoid Monitors

Subarachnoid bolts are fluid-coupled systemsithin a hollow screw that can be placed through

he skull adjacent to the dura. The dura is then
unctured, which allows the CSF to communicate c
ith the fluid column and transducer. The mostommonly used subarachnoid monitor is the Rich-ond (or Becker) bolt; other types include thehilly bolt, the Leeds screw, and the Landy screw.hese devices have low risk of infection and hem-rrhage, but often clog with debris and are unreli-ble; therefore, they are rarely used.

pidural Monitors

Epidural monitors contain optical transducershat rest against the dura after passing through thekull. They are often inaccurate, as the dura dampshe pressure transmitted to the epidural space, andhus are of limited clinical utility.13 They are usedn the management of coagulopathic patients withepatic encephalopathy complicated by cerebraldema. In this setting, use of these catheters isssociated with a significantly lower risk of intra-erebral hemorrhage (4% vs 20% and 22% forntraparenchymal and intraventricular devices, re-pectively) and fatal hemorrhage (1% vs 5% and%, respectively).14

OPERATIVE MANAGEMENT FORELEVATED ICP

The decision to treat elevated ICP with a surgi-al procedure depends on the underlying etiologyf the increased pressure. Focal hematomas orther mass lesions in a surgically accessible regionre usually amenable to operative intervention. Theecision to treat is often obvious and necessitateshe earliest possible consultation with the neuro-urgeon.

Decompressive craniectomy is an increasinglyopular procedure. This operation removes theigid confines of the bony skull, increasing theotential volume of the intracranial contents andircumventing the Monro-Kellie doctrine (Figs 1nd 2). The indications for this procedure arexpanding, with a growing body of literature sup-orting its efficacy.15-24 Importantly, it has beenemonstrated that in patients with elevated ICP,raniectomy alone lowers ICP by an average of5%, but opening the dura in addition to the bonykull resulted in an average ICP decrease of 70%.25

apid and sustained control of ICP, including these of decompressive craniectomy, has beenhown to improve outcomes in trauma, stroke, andubarachnoid hemorrhage in carefully selected

26-30
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171NEUROSURGICAL ASPECTS OF CRITICAL CARE NEUROLOGY

NEUROSURGICAL HARDWARE

When a patient presents to the ICU with preex-sting neurosurgical hardware, two issues can arisehat may result in a neurosurgical consult: concernor infection and magnetic resonance imagingMRI) compatibility.

Infection

There are two primary concerns surroundingeurosurgical hardware in the setting of infection.

Fig 1. The premise behind decompressive craniectomyepresented graphically. The normal ICP compliance curve isutlined in green, changing to red with increasing intracranialolume resulting in a rapid increase in ICP after compensa-ory mechanisms have been exhausted. In contrast, the blueine demonstrates continued low ICP even with increasedolume in a patient who underwent decompressive craniec-omy.

Fig 2. Noncontrast head CT demonstrating before (A) a
raniectomy. Note the decreased cerebral edema and decompressio
irst, as with all implants, the presence of a foreignody has the potential to serve as a nidus forontinued infection. Second, specific to CSFhunts and baclofen pumps, the tubing presents aossible route of entry of infection to the centralervous system (CNS). If CNS infection is docu-ented, then removal of some or all of the hard-are may be indicated.Establishing the presence of a CNS infection isost commonly done by obtaining a CSF speci-en for analysis. If possible, it is preferable to

btain a specimen before the initiation of antibioticherapy. It is important to note that there can beany concealed pitfalls when evaluating CSF from

eurosurgical patients. Both shunt taps and lumbarunctures have potential risks and benefits. Shuntaps may be physically easier to perform than aumbar puncture, and the possibility exists that annfection may be present in the closed system of ahunt for noncommunicating hydrocephalus thatay not be initially detected by a lumbar puncture.owever, neurosurgeons will occasionally prefer a

umbar puncture for CSF sampling, because theres a risk of contamination when sampling CSFrom a shunt valve. Poor technique in setting theap can lead to a false-positive result, showingram-positive organisms in the CSF. Equally im-ortant, the possibility exists that a previouslyterile shunt system may be seeded with bacteriauring the setting of a tap. The request to violate a

r (B) imaging of a patient who underwent decompressive
nd afte n of the cerebral hemispheres.

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hunt system with a tap should be undertaken onlyfter careful deliberation by the ICU team andhould not be performed without neurosurgicalonsultation.

Several issues must be taken into considerationhen performing a lumbar puncture. First, chron-

cally shunted patients will not have normal circu-ation of CSF in the thecal sac. This means thatSF obtained by lumbar puncture may have arofile suggestive of infection (high protein, lowlucose, and abnormal cell counts), which may inact be due to a sedimentation effect. Thus, onlyhe results of the gram stain and culture should beonsidered reliable. Second, care must be takenhen performing a lumbar puncture in patientsith lumbar hardware (baclofen pumps, lumbo-eritoneal shunts), because there is a risk of dam-ge to the tubing during the procedure. Finally,atients with a history of myelomeningocele mayot be candidates for lumbar puncture, becausehey may have tethered (and thus caudally dis-laced) spinal cords that could be injured by theassage of a needle.For a child with a ventricular shunt, it is impor-

ant to ascertain the location of the distal end of theatheter. Most shunts terminate in the peritoneum,ut other locations include the pleural space, theight atrium of the heart, and, rarely, the gallblad-er. Any peritoneal infection in the setting of ahunt that terminates in the peritoneal cavity ne-essitates a neurosurgical consultation. Obviously,iolation of any of the potential spaces in whichhe catheter rests (such as a chest tube in a ven-riculopleural shunt or a new gastrostomy tube in aentriculoperitoneal shunt) also mandates a neuro-urgical consultation.

The presence of suspected or culture-provenacteremia is of significance in a patient with aentriculoatrial shunt. These patients will need aeurosurgical consult and should be considered forchocardiogram evaluation to inspect the distal endf the shunt for possible septic thrombi. In allatients with neurosurgical hardware and culture-roven bacterima, a neurosurgical consult shoulde obtained.

MRI Compatibility

Nearly all neurosurgical hardware is compatibleith MRI, and any concerns can generally be

lleviated by referring to the device’s specifica-
ions. However, a more common and less well- a
nown problem with MRI and neurosurgical hard-are is the problem of reprogramming. Allrogrammable shunts currently in use can be resety suitably powerful magnetic fields. In addition,everal other neurosurgical devices, such as vagalerve stimulators (VNSs), can be affected by mag-etic fields. Thus, in a patient with one of theseevices, a pre-MRI evaluation of settings must beone, followed by appropriate post-MRI evalua-ion to confirm that the device has been returned tots correct setting. A cranial MRI can be done inatients with a VNS, because the actual device isot within the magnetic field generated by a headoil. A spinal MRI is contraindicated, because theevice is within the magnetic field generated by theody coil, and there is the potential for nervenjury.

INFECTIONS WITH NEUROSURGICALIMPLICATIONS

Four general categories of infections that may bereated in the pediatric ICU have potential neuro-urgical implications. Children with severe, recur-ent ear infections with possible mastoiditis are atisk for subdural empyema or brain abscess, usu-lly caused by direct extension of infection. Pa-ients with prolonged bacteremia or endocarditisay develop brain abscess or mycotic aneurysms.rofoundly immunosuppressed children, such as

ransplant recipients, are also at risk for brainbscess or meningitis. Finally, children with bac-erial (or occasionally viral) meningitis may havelevated ICP and may be candidates for CSF di-ersion by an external ventricular drain if symp-omatic.

The best approach to diagnosing and treatinghese conditions is to maintain a high index ofuspicion and to involve the neurosurgical teamarly in the hospitalization of these patients.

BLEEDING DISORDERS WITHNEUROSURGICAL IMPLICATIONS

Children with disorders of coagulation or plate-et function may be at risk for spontaneous intra-erebral hemorrhage. If a patient with a bleedingisorder has a change in mental status or neuro-ogic exam, diagnosis of intracranial bleeding isest made with a noncontrast CT scan. After diag-osis is made, urgent neurosurgical consultationhould be obtained. Acute correction may be
chieved by transfusion of platelets or coagulation

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Fig 3. Clinical practice guideline for the perioperative management of a pediatric patient with DI. (Reprinted with permission
rom Children’s Hospital Boston.)

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actors, but the best approach to treating theseatients is correcting the underlying disorder. Spe-ial attention must be given to these patients’ fluid

Fig 3.

alance in the heat of readying them for the oper- t

ting room, because fluid overload can be a signif-cant problem. Furthermore, normalization of theleeding disorder must continue after the operation

nued)

o minimize postoperative rebleeding. However,

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oth the ICU team and the neurosurgeons mayave to realize that there may be situations when itay not be feasible to operate if the goal of

ntraoperative hemostasis does not seem to bettainable.

Fig 3.

A rare but important situation involving disor- a

ers of coagulation is fulminant liver failure inoma. In patients with fulminant hepatic failure,rain edema and the resulting intracranial hyper-ension often lead to death; ICP monitoring thusay be valuable. However, there is uncertainty

nued)

bout the hazards of implanting ICP monitoring

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evices. Epidural transducers are commonly usednd had the lowest complication rate in a recenttudy (3.8%).14 Subdural bolts and parenchymalonitors (fiberoptic pressure transducers in direct

Fig 3.

ontact with brain parenchyma and intraventricular c

atheters) were associated with complication ratesf 20% and 22%, respectively. Fatal hemorrhageccurred in 1% of patients undergoing epiduralCP monitoring, whereas subdural and intraparen-

nued)
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hymal devices had fatal hemorrhage rates of 5%

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nd 4%, respectively. Thus, in the setting of ful-inant hepatic failure, epidural transducers may be

he safest choice for ICP monitoring, even thoughhey are known to be less precise than the otherevices.14

ENDOCRINE DISORDERSEndocrine disorders are common sequelae of

eurosurgical disease. Often overlooked is theeed for stress-dose corticosteroids in patients withong-term steroid use or recent surgery involvinghe region of the pituitary gland. These patients canresent with rapid and profound hemodynamicnstability. If in doubt, hydrocortisone may bedministered as a one-time dose of while an endo-rine consultation is obtained. The usual dose is 50o 100 mg/m2/day.

Perhaps most prevalent are disorders of salt andater homeostasis: diabetes insipidus (DI), the

yndrome of inappropriate secretion of antidiureticormone (SIADH), and cerebral salt wastingCSW). There is often confusion over the diagnosisnd treatment of these diseases. In general, theyan be diagnosed by evaluating serum sodium andrine sodium levels, along with volume status (asetermined by central venous pressure [CVP] andrine output). DI is usually manifested by higherum sodium, low urine sodium, and volumeepletion (low CVP, high urine output). SIADH is
he opposite, with low serum sodium, high urine b
REFERENC

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odium, and volume overload (high CVP, lowrine output). CSW is manifested by low serumodium, high urine sodium, and volume depletionlow CVP, high urine output). A detailed discus-ion of these disorders is beyond the scope of thisrticle, but it is useful to note that CSW rarelyccurs outside of the setting of aneurysmal sub-rachnoid hemorrhage and that DI is common afterurgery near the pituitary gland or after trauma.

DI merits special attention, because it is perhapshe most common endocrine disorder present ineurosurgical patients. The management of thisisease often involves overlap between the endo-rinologist, the neurosurgeon, and the ICU physi-ian. To standardize care and minimize differencesn management, a protocol for the management ofI was created at Children’s Hospital Boston

Fig 3).

CONCLUSION

The management of the pediatric neurosurgicalatient requires a detailed understanding of theiagnosis and management of disorders of ICP.requently the care of these patients will requireollaboration between several different teams ofhysicians. Most important, frequent and clearommunication between the ICU physician and theeurosurgeon will facilitate the delivery of the
est-quality care to these children.
ES

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