Lumbar Puncture Opening Pressure - What is Good Practice?
Lumbar Puncture Opening Pressure Measurement
Accurate recording of CSF pressure is very important, especially in the investigation of acute headache.
This video is about 7 minutes long but will ilustrate needle insertion and opening pressure measurement for you:
Please note opening pressure must be measured with the patient lying absolutely horizontal on their side.
When CSF appears it is usually clear with a sheen to it ("Gin Clear").
Don't worry if there is slight blood staining, or the CSF is discoloured - you are going to need laboratory analysis no matter what.
Once you see CSF..
- Measure the opening pressure
Allow the CSF to rise up the columnKnow the normal Range of Opening Pressure
- Connect the manometer to the end of the spinal needle.
The manometer has a three-way tap at the end.
The tap is rotated so that it blocks CSF from coming out of the end of the needle and therefore flows up the manomter tubing.
Holding a manometer and spinal needle in place while CSF pressure is recorded takes dexterity!
Know factors that Influence Opening Pressure
- Strictly the normal range of lumbar puncture opening pressure is 8cm to 21cm.
However, obesity, which is much more widespread since normal values were estimated (in the 1960s and 1980s) increases CSF pressure so between 20-25cm is a bit of a grey area in obese subjects.
In the 1960's, 105 normal subjects recorded opening pressures of 15cm +/- SD 3.3cm, which means that 95% will be found between 8.4cm and 21.6cm.
Pressures over 25cm are definitely abnormal.
Elevated pressure may be the only clue to cerebral venous sinus thrombosis or can indicate idiopathic intracranial hypertension.Low pressure can cause acute headache (usually 6cm or less), and CSF is difficult to obtain).Any reason for not being able to measure opening pressure should be recorded in the patient’s notes.The actual opening pressure should routinely be recorded when writing up a lumbar punctureClosing pressures are often measured, but the rationale for this is uncertain. It is not known if closing pressure readings have any predictive value
- Minor changes in posture, respiration, degree of knee flexion, increased blood pressure and slight degrees of inadvertent head up tilt.
In hospital beds, a slight incline is often overlooked and as the bed is not fully horizontal opening pressure is overestimated.
Too many pillows under the head can raise pressure by several centimetres too!
Now you know about Lumbar Puncture Opening Pressure, read more about the Lumbar Puncture Procedure
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