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S. Lee Woods

18 Subdural Tap

A. Indications (1–4)

1. To diagnose acute subdural collection over the cerebral

convexities (hemorrhage, effusion, empyema) (5–7)

 Computerized tomography (CT) is now generally

available and is a safer method for detecting subdural

fluid. Subdural tap should be reserved as a diagnostic

tool for the infant who is too unstable to be transported

for CT scanning.

2. To sample convexity subdural collection for hematologic, microbiologic, and biochemical studies

3. To drain convexity subdural collection to reduce

increased intracranial pressure or to prevent the development of craniocerebral disproportion

 Repeated therapeutic subdural taps should not be

performed unless the infant is symptomatic or the head

size is growing rapidly. Surgical intervention is indicated if subdural taps are not effective in controlling

these symptoms (2).

B. Contraindications

1. Clinical instability when risk exceeds potential benefit

2. Uncorrected thrombocytopenia or bleeding diathesis

3. Infection in the skin or underlying tissue at or near the

puncture site

C. Equipment

All equipment must be sterile, except safety razor and face

mask.

1. Gloves and face mask

2. Cup with iodophor antiseptic solution

3. Gauze swabs

4. Drapes or surgical towels

5. Two short bevel needles, 19 to 22 gauge × 1 inch, with

stylets

6. Specimen tubes with caps

7. Adhesive bandage

8. Safety razor

D. Precautions

1. Use strict aseptic technique as for a major procedure

(see Chapter 5).

2. Insert the needle as far laterally as possible at the border

of the anterior fontanelle or along the coronal suture, at

least 1 to 2 cm from the midline, to avoid puncturing

the sagittal sinus. Do not direct the needle medially

during insertion.

3. Remove the needle if there is not a definite change in

resistance on penetrating the dura after insertion to

approximately 0.5 to 1 cm.

4. Hold the needle securely at all times to avoid inadvertent movement of the needle tip. Grasp the needle

firmly or apply a hemostat at approximately 1 cm

from the beveled end of the needle, to prevent inadvertent advancement of the needle into the cerebral

cortex.

5. Allow fluid to drain spontaneously. Do not aspirate

with a syringe.

6. Limit fluid collected to 15 to 20 mL from each side.

Removal of larger volumes can lead to bleeding into

the subdural space.

7. If frequent taps are required, vary the puncture site

slightly to prevent fistula formation.

8. Following the procedure, apply pressure to the scalp for

2 to 3 minutes to prevent fluid leak from the puncture

site or subgaleal fluid collection.

E. Technique (1,8,9)

1. Place the infant supine, with the crown of the head at

the table edge. Monitor cardiorespiratory status.

2. Have the assistant restrain the infant and steady the

infant’s head (Fig. 18.1).

3. Shave the head over a wide area surrounding the anterior fontanelle (Fig. 18.1).

4. Locate the junctions of the coronal sutures and anterior

fontanelle.

5. Put on mask. Wash hands thoroughly and put on sterile

gloves.