intraspinal epidermoid tumor (23).

4. To prevent traumatic tap caused by overpenetration,

insert the needle slowly while removing the stylet at frequent intervals to detect CSF as soon as the subdural

space is entered (24–27). Use of local anesthetic may

also help reduce the incidence of traumatic tap (26,27).

5. Never aspirate CSF with a syringe. Even a small

amount of negative pressure can increase the risk of

subdural hemorrhage or herniation.

6. Palpate landmarks accurately to prevent puncture

above the L2–L3 interspace (lower interspace should

be used for preterm infants; see discussion under E2).

E. Technique (20,21) (See Procedures

Website for Video)

1. Have an assistant restrain the infant in the lateral decubitus or sitting position, with spine flexed (Figs. 17.1

and 17.2). Avoid flexion of the neck, as this increases

the chance of airway compromise.

2. Palpate the interspace that falls immediately above or

below an imaginary line drawn between the iliac crests

(L3–L4 and L4–L5 interspaces, preferred sites for LP)

(Fig. 17.3).

 The termination of the spinal cord relative to the

spine changes during fetal development and early

infancy (28–30). The normal adult termination,

between the middle of T12 and the lower portion of L3

vertebrae, is not achieved until 2 months postterm (30).

Between 25 and 40 weeks’ gestation, the cord termination gradually ascends from L4 to L2 (30). This should

be taken into account, and the lower L4–L5 interspace

used for lumbar puncture in significantly preterm

infants, to avoid possible cord penetration (28).

3. Prepare as for major procedure (see Chapter 5). Put

mask on. Wash hands thoroughly and wear sterile gloves.

Fig. 17.1. Restraining infant for LP in the lateral recumbent position. Neck should not be flexed.

106 Section IV ■ Miscellaneous Sampling

4. Clean the lumbar area three times with antiseptic.

a. Begin at the desired interspace and wash in enlarging circles to include the iliac crests.

b. Allow antiseptic to dry or blot excess with sterile

gauze.

5. Drape, leaving the puncture site and infant’s face

exposed. A transparent aperture drape is recommended

because it does not obstruct the view of the patient.

 Use of local anesthetic cream prior to cleaning the

area may be helpful in reducing pain during LP (31–

33). Use of local anesthetic does not reduce physiologic

instability, but may reduce struggling by the infant during the procedure (34,35) and the incidenc of traumatic tap (26,27).

6. Insert the needle in the midline into the desired interspace.

a. Aim slightly cephalad (on a plane with the umbilicus) to avoid the vertebral bodies (Fig. 17.4).

b. If resistance is met, withdraw the needle slightly and

redirect more cephalad.

c. Hold a finger on the vertebral process above the

interspace to aid in locating the puncture site if the

infant moves.

7. Advance the needle slowly to a depth of approximately

1 to 1.5 cm in a term infant, less in a preterm infant,

until the epidermis and dermis are traversed.

a. As the needle is further advanced, remove the stylet

frequently to check for fluid. Replace the stylet

before advancing the needle.

b. A change in resistance can often be felt as the needle passes through the ligamentum flavum and dura

(Fig. 17.5). This may be more difficult to appreciate

in a young infant than in an older child.

c. Wait for fluid after removing the stylet, as the flow

may be slow.

d. If no fluid is obtained, rotate the needle to reorient

the bevel. If no fluid is obtained, replace the stylet,

Fig. 17.2. Restraining infant for LP in the sitting position.

A B

Fig. 17.3. A: Externally palpable anatomic

landmarks. B: Vertebral bodies removed to

show anatomy of spinal cord in lumbosacral

area in relation to external landmarks.