Lumbar Puncture fact#5
Lumbar Puncture: Remember to Measure Opening Pressure
The usual reason for not measuring opening pressure at lumbar puncture is forgetting to include a manometer (pressure guage) in your equipment.
At LP, opening pressure should be measured without exception in the investigation of acute headache. Always remember to measure opening pressure with your patient lying on their side, not sitting upright. The zero point for opening pressure is at the base of the skull, so if you are sitting up and you needle is in the lumbar spine the opening pressure will be at least 30cm (or whatever height the base of the skull is above your needle! If you then add the 10-20cm of intracranial pressure you have a reading in excess of 40cm guaranteed! This is not to be confused with intracranial hypertension, it is a simple but potentially serious error, but it is easy to forget the basics.
When I use Lumbar Puncture to investigate for inflammatory disorders, such as multiple sclerosis, I will deliberately sit the patient up if I don’t have very clear anatomical landmarks, as opening pressure is not crucial in this situation.
However, you need to maintain your skill in Lumbar Puncture with your patient lying on their side, so that if you have to do one for an emergency presentation with headache you have the necesary skill to get the needle inserted with your patient on their side - allowing you to measure opening pressure.