Lumbar Puncture

The successful Lumbar Puncture……Key points
A calm environment
A trained nurse to assist
Careful explanation to patient of what to expect
Spend time on positioning the patient properly
Make sure you achieve cutaneous anaesthesia
Remember the 6 layers from skin to CSF
Loosen manometer tap and connect to manometer guage before you insert needle
Collect adequate specimens (2mls per bottle)
Be confident - if your position and anatomical knowledeg are correct you will succeed
Don’t rush your patient afterwards, let them take their own time to get ready to leave

Introduction
Even today the word lumbar puncture still strikes fear in patients and practitioners. Like all fear, education will alleviate it! I’ve now done hundreds of LPs, teach about LPs and write LP guidelines. Here’s how I go about it. The information here would be very useful when counselling your patients prior to the test. Any postgraduate physician in training would be expected to have a detailed knowledge of how to do an LP, and it is a core skill for emergency medicine and neurology.

Before you do an LP, make sure you have observed several successful and unsuccessful procedures. Make yourself aware of the anatomy of the lumbar spine and spinal canal, and the layers that your needle will traverse. An LP will be a lot easier in a calm environment e.g. side room, treatment room, day-case theatre/OR. I strongly advise that you have with you a nurse or nursing auxiliary who has assisted at many LPs before.

Equipment
An LP is usually performed on a hospital bed, or treatment couch or procedure table. The room should be well lit, warm and private. You will need, anti-septic (chlorhexidine or iodine-based), sterile drapes, sterile gloves. You will need a hypodermic needle and 5 ml syringe to draw up local anaesthetic, and another hypodermic needle to inject the local anaesthetic. You need a spinal needle (will discuss choice of needle later), and a manometer to measure opening pressure. Specimen containers are required – usually 4 are needed, and a fluoride oxalate tube if glucose is being measured in CSF. Blood bottles and venepuncture equipment for paired blood glucose, protein and serum oligoclonal bands are also needed. Most hospitals will already have pre-packed trays to which you need to add your own manometer - pre-packed spinal amaesthesia trays usually have atraumatic needles, and may not be suitable for diagnostic or therapeutic LP. Alternatively you can use an ordinary dressing pack and add your own choice of LP needle and manometer.

Choice of needle
There has been debate for years about use of atraumatic needles versus the classic bevelled tip needle. The difficulty with atraumatic needles is that the aperture in the needle is small and the needle is of fine bore making pressure recording (arguably) unreliable and sample collection slow. A bevelled needle will give a more reliable pressure reading and in some cases you actually want to create a dural tear – such as therapeutic LP in Idiopathic Intracranial Hypertension. There is consensu that atraumatic needles do reduce the incidence of post-LP headache, but I think they should be reserved for spinal anaesthesia. There is a technique described where oblique insertion of the bevelled needle can create a self-sealing hole (see the LP Directory). For diagnostic LP I prefer a 20guage bevelled tip needle of 8-9cm (3.5 inch) length. In obese subjects a 5.5 inch needle (or longer) may be required.

Anatomy review
The layers you pass en route to the CSF are: 1. Skin, 2 Subcutaneous fat, 3 Interspinous ligament, 4 Ligamentum flavum, 5 Epidural space, 6 Meninges to arrive at the subarachnoid space. The usual distance to the CSF space according to most studies is about 4 to 7 centimeters, i.e. before the needle is in to the hilt. In obese subjects the subcutaneous layer obscures the anatomy and increases the distance to the spinal canal. You need to have this layering in your mind as you do the LP. The ligamentum flavum can often be heavily calified in older people and may give resistance, before the needle ‘pops’ gently into the epidural space. I would not say that a ‘give’ or ‘pop’ is felt in every case, but if you can learn to feel for this it will help you in some cases.

Positioning the patient
The aim of positioning is to create the widest possible gap between the L3 and L4 spinous processes for your needle, and to set the patient up as geometrically as possible to create easy reference points to allow you to plan the needle’s trajectory. An LP is easiest performed in the sitting position, with forward flexion of the trunk, as the midline of the spine is easy to see. However a seated patient has a 60cm column of pressure from the base of the neck to the entry point of the LP needle and manometer, so a high pressure is always measured! I am not a great fan of inserting the needle seated and then gently lowering the patient on to their side to measure pressure. I have done it, but the potential for neural injury must be present, and it is disquieting to withdraw a kinked needle. Usually, if pressure is needing to be measured (and it almost always does, especially in acute headache), lie the patient on their left hand side - the left lateral position, with knees flexed up towards the abdomen. The head should be supported by one pillow only, and your patient may feel more comfortable with another pillow between their knees. In a horizontal plane, make sure that your patient’s back is parallel with the edge of the bed. In a vertical plane imagine that a plumb line suspended from the ceiling will touch both posterior iliac spines. If you take time to position in this way, you are most likely to have acheived adequate separation of the spinous processes between lumbar vertabrae L3 and L4, making the path for your needle as wide as possible. If you maintain the correct vertical orientation you are less likely to pass the needle to the left (too low) or right (too high) of the midline. Remember that if you can aim for the small target between spinous processes towards the small diamond of exposed ligamentum you could be well on your way to a near painless LP needle insertion! Most pain associated with LP is due to contact of the needle with periosteum of the spinous processes.

Confirming the L3/L4 intervertebral space
This can be very difficult, and some studies sugest that accuracy in identifying this space could be as low as 50%. Ultrasound can assist in identification of the interspinous space, especially if there is an excess of subcut tissue. Unfortunately Ultraound is not widely used, but I expect to make this standard in my own practice shortly, especially if anatomical landmarks are indistinct. The line between the right (upper as you see it) and left (lower as you see it) posterior superior iliac spines - named Tuffiers Line - runs through closest to the L4/5 interspace i.e. too low. You want to go for the interspace immediately cephalad (towards the head) to Tuffiers Line. The L3/4 space is wider and easier to penetrate. L2/3 is wider still, but you are more likely to hit an abnormally low lying spinal cord tip at L2/3. Your needle wants to enter the skin at a point on the surface in the midline in horizontal and vertical planes. You can mark the skin with a pen, or indent the skin with a blunt marker (e.g. the cap of one of your hypodermic needles).

Preparing the skin
Use aseptic technique (and do not, under any circumstance, penetrate the skin through an obvious focus of cutaneous infection - you could cause meningitis), start at the proposed puncture site and in a circular motion move outwards until your field is covered. Wait for the solution to dry (takes 2-3 minutes - will feel like a long time) and apply another. While waiting for the second application to dry, draw up local anaesthetic, get your LP needle out of its cover, and connect up your manometer. When connecting your manometer make sure you test the 3-way tap at the bottom as it is usually very stiff and almost impossible to undo with one hand holding the manometer steady! In one of my earliest LPs I did not loosen the 3-way, and struggled to open it while trying to steady the manometer guage with the same hand.

Local Anaesthetic
I normally use about 1 to 2ml of lidocaine 2%. My initial injection is a subdermal bleb, which almost immediately freezes the dermis (a tip taught me by a staff grade anaesthetist from Ninewells Hospital, Dundee - whose name I forget - sorry!). If you achieve immediate anaesthesia - test by pricking the skin with the needle over your bleb, then I usually go straight for the LP needle. If you do not acheive immediate anaesthesia, put 1-2 mls a bit deeper. I avoid using too much local as it can eventually distort the palpable anatomy. You may have been taught to put in 5 to 10mls, but I am letting you know I rarely use more than 2mls. Acute lidocaine toxicity can provoke a generalised tonic clonic seizure (I’ve seen it happen) and is another good reason to avoid too much LA.

Insert the Needle
Insert the needle into your dermal bleb. Try to keep the needle parallel with the ceiling, and perpendicular to the inter-iliac line. Aim the needle slightly cephalad (meaning aim for the umbilicus area - mid anterior abdomen). After about 4 cm start to feel if you get a very slight give as you penetrate the 4th layer in the LP cake called ligamentum flavum. If you feel that give, you are nearly there. If you are slightly too high (right) or too low (left) you may make contact with a lumbar nerve root, which will produce sciatic-type pain into the thigh. Ask your patient to report any shooting pain as it can help you reposition the needle back toweards the middle. Once you have felt the “give” advance the needle another 2-3mm and withdraw the central part of the needle called the stylet. Wait about 10 seconds to see if CSF appears. If you get venous blood you are most likely in the epidural space and are only a few mm from glory. In a non-obese subject you may find that you have advanced the needle almost up to the hilt (9cm / 3.5inches). If you do not have CSF, pull the needle back 3-5mm and remove the stylet to see if you get CSF. Check that you have not deviated from the midline and are still heading in the direction of the centre of the anterior abdomen.

Collecting CSF
If you get CSF (well done!), connect the 3-ay tap and manometer tubing. The CSF will rise up the tube and once it has reached its peak you may see it rise and fall with respiration. Open the three way tap to drain the manometer intoa CSF container (this will come out in a rush). Then you have the option of removing the manometer completely and allowing CSF collection to proceed directly from the end of the open needle. Collect about 20 drops per container (I’m talking about adults), which will be about 2mls per container. This means you will never have to explain to your patient that despite all the trouble of getting an LP needle the lab report said insufficient sample (you must avoid this!). An adult makes about 500mls of CSF per day, and isotope studies suggest that CSF is replaced about 4 times daily. This means that your 8 ml CSF sample is replaced by the brain within about 20 minutes of LP completion. You have been warned.

Withdrawing the Needle and Skin Dressing
Before removing the needle, replace the stylet. If you don’t there is the potential for a suction effect to draw soft tissues, such as a nerve root into contact with the LP needle, leading to nerve injury and pain for your patient. Please make sure you replace the stylet. An elastoplast is sufficient dressing after an LP. There is no need to bandage the patient up like they have had major surgery. (I’ve seen it done!).

Aftercare
Prolonged bed rest is not mandatory after an LP, as clinical trial evidence does not support its use to prevent post-LP headache. A short period of rest is of course kind and considerate, and I advise my patients to sit up once they feel comfortable to do so. Avoid driving home after an LP as your patient may develop an acute post-spinal headache which could impair driving ability. The dry skin dressing can be removed after 12-24 hours.

Complications
About 30-50% of people after LP will experience a new headache, worse with upright and better with supine posture. This is due to low pressure of CSF within the cranial cavity, caused by persistent leak of CSF through your dural tear into the lumbar canal. About 1-2% will dvelop a real stinker of a post-LP headache and may not be able to lift their head from the pillow without vomiting or experiencing extreme pain. I normally reserve epidural blood patching for the latter group. Most post-LP headaches will resolve with a mix of bed rest, additional 2 litres per day fluid intake and regular dosing with non-steroidals or paracetamol. Tangential needle insertion, is a skill that may be worth acquiring, as there is a logical, but not widely accepted, argument that this simple technique will reduce post-LP headache by creating a self-healing hole.

Pictures
There are videos of LP posted on YouTube: you can view them on my LP videos page. Viewing may be slow depending upon your connection. Watchout for the practical joke video where a nurse collects CSF into a coffee cup - I don’t endorse that one).

Consent forms
All procedures require a patient’s consent. In emergencies it may not be possible to obtain a patient’s consent e.g. confusion or coma, and it is reasonable in that situation to record that consent is not possible (as a courtesy you should explain the procedure to next of kin). Your patient should be consented for the following: 1 Reason for LP, 2 initial pain of local anaesthesia, 3 potential for discomfort of inserting needle close to bone or nerve root 4 transient low back discomfort in the days after an LP, especially if it was difficlut to obtain, 5 post-LP headache 30-50% rate, 1-2% are severe and may require additional intervention.

Each year almost a million people worldwide will have to have a lumbar puncture (or spinal tap) test performed.   A lumbar puncture (also called LP) is a test where a needle is put into the lower back to obtain a sample of fluid called cerebrospinal fluid (or CSF).   The usual reason for the test is to investigate a sudden onset headache such as suspected meningitis or subarachnoid haemorrhage (a type or brain haemorrhage).   It can also be used to investigate other headaches such as the one caused by raised pressure within the skull - idiopathic intrancranial hypertension. Lumbar puncture has a notorious reputation, and while any medical procedure can be uncomfortable, why is this particularly true for LP?

LPs were first performed in the late 1800, by an Englishman called Wynter in 1889, although Quincke - a German physician - is most widely creditied with the first LP in 1890. These first LP tests were performed in children with a very grave illness called TB meningitis.  Many of these first LP cases died from their disease - it is easy to see how LP could get a bad reputation.  Even until relatively recently, an LP was seen as a test which could be performed at the bedside by fairly inexperienced doctors, and training in LP has been poorly organised - there is an old phrase (now discredited) called see-one - do-one - teach-one. There is no doubt that an experienced person will be much more likely to perform a skilled and relatively painless LP.  If most people’s experience of LP is performance by a very junior doctor the bad reputation can only be re-inforced.

To get a better picture of the reality of performing and experiencing a LP you shold ask people who have had several LPs or speak to experienced LP operators. Idiopathic Intracranial Hypertension is a rare condition causing headaches and impaired vision due to high pressure of cerebrospinal fluid within the nervous system.  People with IIH often need many LPs to relieve the pressure and prevent visual problems. Here’s a quote from one patient:

“I was really nervous about it, they caught a nerve but i told them and they moved the needle, it was a bit uncomfortable lying in the same position for 2 and a half  hours while they drained me, but then afterwards my back ached for a while and the next day it felt like when you have a bruise, but then I was ok”

Maybe this doesn’t seem too bad.  Note how she was nervous and I’m sure not knowing what to expect is part of the reason for the bad experiences reported by many.  Another IIH sufferer has had over 15 LPs (another says she has stopped counting!) I think it is interesting to note that not being prepared mentally may have contributed to her discomfort:

“I have had about 15 + LP’s. The first one hurt but I think that was because I was so tense and didn’t know what to expect. I apologise to those reading this who have a bad time but after that first one I had no problems at all and was fine about having them. I only ever had the expected discomfort of that sort of tugging in your back but that’s it”

While the actual LP may not be that bad, the most feared complication is a bad post-lumbar puncture headache (or spinal headache).  In an LP a small hole has been made in the base of the contained that holds brain and spinal fluid.  This contained called the meninges will usually seal spontaneously.  In some the seal does not occur, and CSF continues to leak out into the spine.  This causes a drop in pressure, and means that the brain is no longer supported by a normal amount of CSF.  In reality the brain is rattling around in the head causing irritation to the meninges and creating a severe pain, which is a lot worse when standing and is only relieved by lying flat.  Not knowing that this may occur is another cause for distress.

To keep discomfort from an LP to a minimum, it is important to be fully aware of the range of experiences an LP may bring.  Having performed many LPs in his career, he would vouch that many patients will have virtually no pain, except for the sting of local anaesthetic injection.  “There is no doubt that some people are very distressed by their LP.  Usually this is becasue it is not possible to find a pathway for the needle which avoids contact with the bones of the spine.  This can be a particular problem in people who are very overweight, and we all know that the trends in obesity will make LPs more difficult for more patients in the coming years”

If there is a problem with the needle path or trajectory, why don’t doctors use x-rays to guide their needles?  One reason is that the majority of LPs are done easily and it is perhaps unreasonable to expose people to x-rays without good cause. However, a recent review by Dr Michael Murphy Dr Arun Nagdev of the American College of Emergency Physicians outline the value of using ultrasound  to guide needles in difficult cases.  This technique may be useful in children or obese patients, or people who have previously had back surgery.  At present x-ray guided LPs are rarely used except in the most difficult cases.  Ultrasound may become more widely used, but this will involve provision of new equipment to financially stretched hospitals and additional training for doctors.

In the next 5 years I expect that image guided LP with ultrasound will become more commonplace - I’ve yet to use it in my own practice, but can see the advantages and hope to try it very soon.  Better patient information is also needed.  We have to move away from telling people that there will be a ‘wee scratch’ and make sure that before LP our patients are properly informed. Using best available technology they should then go on to have a technically competent procedure.

There is more information, being added to weekly at www.lumbarpuncture.net, and I am indebted to the IIH forum www.iihsupport.org for personal descriptions of LP.

You can view and order books from Amazon here.  Books specifically on LP are very rare now, and ususally you can only find informatioon in nursing procedure or neurology or acute medicine texts.  I’ve set upa  filter which will try (emphasise - try, it is not perfect) to selct out potential books here.

Nursing Practice: Hospital and Home -- The Adult: Hospital and Home - The Adult
Amazon Price: £30.39
Customer Review: This book is big engough to squish spiders in their tracks, act as a makeshift door stop and provide a great stand for the televisions as well as many other uses that student nurses moving away from home ...

ECG Interpretation Made Incredibly Easy! (Incredibly Easy! Series)
by Springhouse
Amazon Price: £19.95
Customer Review: This book is so useful & I come back to it 'time & time' again as a reference review. Easy layout with helpful 'reminders'

Surgical Talk: Revision in Surgery
by Andrew Goldberg, Gerald Stansby
Amazon Price: £19.00
Customer Review: I used this book for finals.It's a fantastic introduction to surgery (as it assumes very little knowledge), and a great revision guide for finals (since it's orientated to exams right from the start) ther...


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There are very few books devoted to lumbar puncture.  It usually appears as a chapter in a medical procedure textbook.  However, here are some listings from amazon specifically on lumbar puncture (they are very old!).

Preparing for a lumbar puncture
by Barbara Bowens
Amazon Price:

Lumbar Puncture and Spinal Analgesia: Intradural and Extradural
by Sir Robert Macintosh, J Alfred Lee
Amazon Price:

Lumbar Puncture and Related Tests (Nursing in Depth S)
by U Jolly
Amazon Price:


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The most frequent use of an LP is to investigate a new onset headache - suspected meningitis is probably the most common reason worldwide.  I hope you will agree that it is helpful to have acces to regularly updated lists of the very latest publications in the filed of headache.  You can access these via my Headache listing.  This listing is from the 2 most widely read Headache journals - Cephalalgia and Headache.  The problem is that the major neurology journals (Neurology, JNNP, Brain, Annals of Neurology, Archives of Neurology, Lancet Neurology, Journal of Neurology) also publish on headache - no problem.  I’ve included headache and migraine articles from there too!  This is the same listing as seen in neurologyfeeds.com a sister site to lumbarpuncture.net.

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.

There are 6 layers your needle must pass through from skin to CSF.

1. Dermis

2. Subcutaneous fat (most variable distance - more fat, further to go)

3. Interspinous ligament

4. Ligamentum flavum

5. Epidural space

6. Meninges

Today lumbarpuncture.net officially became a leading google listed website.  Hopefully I can be true to this by maintaining a relevant site, with useful information for you.

Apologies for such an ugly looking site, but the content will hopefully compensate.

Please leave comments here, so that I know what you are looking for.  Thanks for contributions on personal LP experience from Idiopathic Intracranial Hypertension Support Forum - people with this rare disorder are likely to have to have many LPs in their lifetime.  NB -If you have IIH and have arrived at lumbarpuncture.net, I would recommend their site www.iihsupport.org.
Thanks. HB