Lumbar Subarachnoid Drain

Indications

A lumbar subarachnoid drain is usually placed in cases of complicated dural tear or deficiency in which a water-tight repair cannot be obtained.
Usually this decision is made intraoperatively after a repair attempt appears insufficient.

Special Equipment

Lumbar drains come in a kit that consists of a large-bore spinal needle, catheter tubing, syringe, and a wire for threading the catheter (Figure 36-1).
In addition, the kit contains an external reservoir that is marked to allow for measurement of cerebrospinal fluid (CSF) output (Figure 36-2).

Figure 36-1 ▪ Subarachnoid drain kit, which contains the spinal needle, catheter tubing, cap for the tubing, guidewire, and a plastic sleeve, which is used to sew the tubing to the patient’s skin.

Figure 36-2 ▪ Reservoir for the subarachnoid drain, which contains a marked bag to allow measurement of cerebrospinal fluid (CSF) output, and an adjustable height ruler to allow movement of the bag up or down for titration of the CSF flow.

Positioning

If the drain is placed in an open fashion intraoperatively for a lumbar dural tear, then the positioning does not need to be changed.
However, if the drain is to be placed postoperatively, or in a patient who underwent cervical or thoracic spine surgery, then the patient should be rolled onto their side in the lateral decubitus position, with the knees flexed up to the chest in order to open up the spinal canal, similar to the position for a lumbar puncture.

Anesthesia/Neuromonitoring Concerns

It is possible to place the drain postoperatively, but for patient comfort it is preferable to place the drain prior to extubation while the patient is still sedated.
In cases at very high risk for irreparable dural defects (eg, massive ossification of the posterior longitudinal ligament being removed anteriorly), we consider placing a drain before the spine portion of the operation.

Localization of Incision

In open lumbar cases, the drain is placed through the open wound and no incision localization is required.
In cervical, thoracic, or minimally invasive surgery lumbar cases, the drain is placed percutaneously. The spinous processes are palpated through the skin, and the drain is placed roughly at the L4-5 or L5-S1 interspaces. If difficulty is encountered at these locations then the surgeon may move higher, but the drain should not generally be placed percutaneously above L1-2 or else the surgeon risks injuring the conus with needle passage. Examine the MRI to determine the location of the conus in a given patient.
In open cases, the drain can be placed under direct visualization at any level.
Fluoroscopy can be used as needed and is helpful to verify final catheter tip position.

Percutaneous Drain Placement

The patient is turned into the lateral decubitus position with knees pulled up to their chest, that is, with the lumbar spine in flexion.

The spinous processes are palpated and a level is selected roughly between L4 and L5 or L5 and S1 (Figure 36-3). If these levels cannot be accessed, the surgeon can move higher, but as noted earlier it is generally not advisable to move higher than L2-3 or else the surgeon risks injuring the conus with needle passage.

Figure 36-3 ▪ Palpation of landmarks. After prepping and draping the patient, the surgeon palpates for the soft spot between the spinous processes, generally around the L4-5 level. In this image the patient is in the right lateral decubitus position with the head to the right of the frame.

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