Pediatric emergency medicine trisk 1164

after each application. The shunt tap is performed by inserting a 23- or 25-gauge
butterfly obliquely into the reservoir and holding the butterfly tubing
perpendicular to the floor. The height of the CSF rise into the butterfly tubing,
measured in centimeters, is the ICP. Normal pressure is between 5 and 10 cm H2
O; pressure of more than 20 cm H2 O is indicative of distal shunt malfunction
requiring urgent revision. Slow or absent flow from the proximal reservoir
(especially with occlusion of the distal reservoir of a double-reservoir shunt) is
highly predictive of proximal shunt obstruction. In this case, the physician may
notice that the reservoir collapses when gentle suction is applied to the butterfly
with a syringe. It is important to avoid further suctioning of this reservoir because
this could lead to aspiration of debris into the proximal catheter, causing a
blockage where one did not previously exist. Poor flow during the shunt tap can
also indicate noncommunicating hydrocephalus, which may be diagnosed by
imaging studies and lumbar puncture.
The shunt tap can be therapeutic and diagnostic. The child with a distal shunt
obstruction or partial proximal obstruction may be eligible for urgent, rather than
emergent, shunt revision if symptoms of increased ICP are alleviated after the tap.
However, removal of too much fluid should be avoided because abrupt fluid
shifts within the cranial vault can lead to disruption of subdural vessels. It is
prudent to remove just enough fluid to decrease the ICP below 20 cm H2 O and
repeat the procedure if symptoms return before definitive surgical management.


FIGURE 135.5 Burr-hole puncture.

The child with complete obstruction of the proximal catheter does not obtain
relief of symptoms after a shunt tap because the obstruction prevents adequate
aspiration of fluid from the ventricles. These children usually respond temporarily
to medical management that decreases their ICP; however, it should be stressed
that restoration of shunt integrity and function is the permanent treatment of shunt
obstruction. In the emergent situation, this treatment includes the administration

of 3% normal saline (5 mL/kg bolus). Further therapy is with acetazolamide
(Diamox) 30 to 80 mg/kg/day and Decadron 1 mg/kg/day and hyperventilation in
the unstable patient.
The following procedures are not commonly performed in the ED, and even
more rarely performed by a clinician other than a neurosurgeon. If the child is
experiencing life-threatening symptoms from proximal obstruction, is unable to
undergo immediate surgical repair, and is unresponsive to medical management, a
burr-hole puncture procedure may be performed ( Fig. 135.5 ). This should be
performed only in dire circumstances, as the procedure carries with it lifethreatening risks such as disruption of intraparenchymal vessels and tissue. By
nature of the procedure itself, the proximal shunt catheter is torn and urgent
revision is therefore mandatory. The burr hole is best identified by direct
palpation and confirmation with the skull radiographs. For example, some
reservoirs are not always located over the burr hole. A 3½-in spinal needle is


inserted perpendicular to the skull through the burr hole to a depth of no more
than 5 cm H2 O. After the stylet is removed, fluid should drain spontaneously and
should be allowed to do so until flow slows down. The patient’s condition should
stabilize sufficiently for transport to an operating suite or tertiary care institution.
Another method of temporarily relieving a lumen obstruction is to flush a small
amount of sterile saline through the clogged tubing in an attempt to dislodge the
obstruction. This method can be used for distal or proximal obstructions, with the
caveat that instilling a few more milliliters into the ventricles may in fact worsen
the patient’s condition. If this procedure is performed with a double-bubble
device, the reservoir that is not being used must be compressed to allow the fluid
to go in only one direction.
In an infant with an open fontanel, the physician can aspirate fluid through a
direct ventricular puncture ( Fig. 135.6 ). This procedure also carries a significant
risk of parenchymal injury should be performed only when prompt surgery is
impossible.

FIGURE 135.6 Ventricular tap through open fontanel.

Infection
The reported incidence of CSF shunt infections ranges between 5% and 10% and
depends on the center performing the study and the criteria used to define
infection. The majority of infections are perioperative in nature. Recent advances
have reduced the rate of infection, including allowing fewer operating room
personnel, soaking the shunt in antibiotics before insertion, and administering


prophylactic antibiotics. Infections generally occur within 2 months of shunt
placement, with a higher incidence of infections in children younger than 4 years.
Other risk factors include insertion of the shunt into a premature infant and
insertion after a previous infection. The common organisms cultured from
infected CSF shunts are gram-positive bacteria ( Table 135.3 ). Staphylococci
adhere well to Silastic tubing, and these infections are often difficult to eradicate
without removal of the catheter. Infections with S. epidermidis , S. aureus , and P.
acnes are common within the first few weeks after surgery. Infections that occur
more than 6 months after shunt placement are more likely due to gram-negative
infections caused by H. influenzae infection, bowel erosion, or pressure necrosis
from the shunt apparatus. Fungi are rare pathogens occasionally seen in
premature infants.
External infection of skin and subcutaneous tissue overlying the shunt
hardware can occur; however, these superficial infections may not lead to shunt
infection if treated promptly. Necrosis of the area around the reservoir can occur
as a result of the constant pressure in infants or nonambulatory patients. Skin
breakdown leading to visualization of the shunt mechanism is, by definition, a
shunt infection and must be treated accordingly.
TABLE 135.3

COMMON ORGANISMS INVOLVED IN CEREBROSPINAL FLUID
SHUNT INFECTIONS
Gram positive

Gram negative

Coagulase-negative
Escherichia coli
staphylococci
(Staphylococcus epidermidis
)
Staphylococcus aureus
Enterococcus species
Streptococcus species
Haemophilus influenzae