Lumbar Puncture

The perfectionists will argue that an LP should always be attempted with your patient lying on their side.  There are some situations where this is unavoidable - a comatose patient, someone in whom opening pressure needs measured.  However, an LP is easier to perform with the patient seated - it is much easier to appreciate the midline, and you are more likely to localise the interspinal space and reach CSF.

I think there are certain situations where it is excusable, in the name of patient comfort, to go straight for a seated position LP.  The one I encounter most frequently is the person with suspected CNS inflammation, who may have had symptoms for weeks or months, and has already been imaged.  The reason for LP here is to detect oligoclonal bands, and pressure measurement is not a primary concern.  If the landmarks or midline are difficult to palpate (feel), then I have no hesitation in sitting the patient up so I can get CSF as quickly and painlessly as possible.

The situations where I think you should always have your patient in the left lateral position are those where they have presented with acute headache.  In this situation measurement of opening pressure is essential.  If you are finding difficulty with obtaining CSF in acute headache, you could sit the patient up and once CSF is obtained, lie them on their side to permit CSF pressure measurement - however, this should not be attempted without the assistance of at least 2 other people, but is, in my view, inadvisable.  We should be moving towards use of ultrasound or x-ray guidance to insert needels in difficult acute headache cases, or invent a manometry system which will compensate for the presure gradient that occurs in the seated position.