How to place a subdural drain
NB:
- this only works for chronic or mostly chronic subdurals (a few streaks of acute or some layering subacute is OK)
- if you think there is a good chance you'll have to convert to a crani, just do it in the OR instead
Entry:
- For 80-90% of subdurals, the optimal entry point will be frontal, slightly above temporalis (you don't want to be cutting through that at bedside) - to find it, ask patient to bite down, feel the temporalis, and feel head for superior nuchal line. I like to go right above that.
-Enter right around coronal suture. I like going 1cm anterior to coronal suture - you can go on it or behind it. Look on scan beforehand for membranes; where the dura attaches to the suture often has a membrane, which can represent thicker dura and higher chance of bleeding.
Shave from entry point to 4-5 cm behind
Prep, lido all around tract, prep again, drape
Incision. Retractors.
Drill--
- some people drill perpendicular, and some drill biased aiming in goal direction.
Open dura with preferred method.
Passing catheter (we typically use EVD catheters)
- some people just put in the stylet in the direction of their goal, +/- biased drilling, and soft pass the catheter over it.
- I prefer to put ~70-80 degree bend on tip of EVD catheter, then insert through burr hole in an angle manner. Then, you soft pass over the angle. This way, you can control the directionality of the catheter.
Insert catheter ~5cm in. The important thing is to stop if you feel resistance, even if you are only 1-2 cm in. If you don't feel any resistance and you are confident in the direction of the catheter, you can go 7-8 cm in. Remove stylet while holding catheter tight.
As much as possible during the procedure, keep a wet raytec over the burr hole to prevent sucking in air. This is especially important when you are aspirating on the catheter within the burr hole.
Attach syringe (raytec over hole) aspirate ~10cc to make sure you are in. Tunnel EVD, suture closed incision, then aspirate however much you want -- in old people, probably don't want to take more than 40cc, old people brains don't tolerate massive shifts. Young people, ok to be more aggressive, can even put suction bulb on subdural drain.
