Obstetrics: Epidurals in labour

What is an epidural? (with pictures so you can show your patients)

Definitions:

Epidural space: an anatomic space that is the outermost part of the spinal canal.

Epidural catheter: A thin plastic tube which is threaded into the epidural space, through which medications can be given.

Epidural injection: Injecting medication into the epidural space without leaving a catheter.

Epidural analgesia: Analgesic medication being infiltrated into the epidural space either by single shot injection or catheter.

‘Spinal’: Actually a misnomer because it is the subarachnoid space that this technique refers to. This is the space between the pia mater and arachnoid mater which contains the spinal cord and nerves, and cerebrospinal fluid.

As you can see, the epidural space is before the dura but after the ligamentum flavum. It contains adipose tissue and connective tissue, a venous network called the Batson’s Plexus, and as you can see it connects out both sides of the spinal canal following the spinal nerve roots, so it also contains the nerve roots and the dural sac. The aim of the procedure is to infiltrate this space with analgesic medication such as local anaesthetic which can then block the dorsal nerve roots as they enter the spinal canal – if you remember your pain module, nociception is transmitted to the central nervous system via A delta or C fibres through the dorsal root ganglion. If the signals don’t reach the central nervous system, then they are not perceived – Voila, patient happiness all round.
This is a side view of where your needle needs to go. Remember the layers: Skin, subcutaneous tissue, supraspinous ligament, interspinous ligament, ligamentum flavum, epidural space.
In this photo you can see how the spinal cord (conus medullaris) terminates at around L1/2. The cauda equina then continues down to the sacrum. The epidural space is millimetres away from the subarachnoid space. This is why it is important to use the loss of resistance technique to avoid inadvertent dural puncture. If you are performing a spinal anaesthetic, patients may get shooting nerve pain if your needle inadvertently contacts a caudal equina nerve.
Here is a photo of the epidural catheter in place – as you can see, the Tuohy finds the space and the catheter is threaded in, ideally upward (helped by the Huber point on the end of the Tuohy needle that angles upward). You leave 5cm of catheter inside the epidural space, and the medication comes out through the holes at the end of the catheter and diffuses through the tissue of the epidural space.
This is the anatomy of a paramedian approach to neuraxial blockade. This is usually used in the thoracic spine as the spinous processes are so large that even with good position, a midline approach will not be successful in finding the epidural/subarachnoid space. The approach is to identify the spinous process at the level of interest, and insert the needle 1cm inferior and 1cm lateral to the spinous process, and advance medially. You might have to ‘walk up’ from the transverse process or off a facet joint. The first resistance encountered will be the ligamentum flavum.

See our spinal page for a description of the bones involved.

Physiological effects

All depends on the level of block, but in general:

  • Differential blockade: motor level different to sensory level different to autonomic level
  • Central nervous system: analgesia, may be MAC sparing if undergoes a GA afterward
  • Cardiovascular system: effects of blocked sympathetic nerve fibres: venous and arterial vasodilation, reduced SVR, changes in chronotropy and inotropy (for higher blocks), and associated alterations in blood pressure and cardiac output. The type and intensity of these changes are related to the level of block, the total number of dermatomes blocked, and, relatedly, the type and dose of LA administered.
  • Respiratory system: Mildly impaired ability to cough, clear secretions as accessory muscles are impaired, but any significant impairment is likely related to a complication such as accidental spinal catheter/local anaesthetic toxicity/high spinal
  • Hypothermia due to vasodilation and sympathetic block

Contraindications

AbsolutePatient refusal
Severe coagulation abnormalities
(eg, frank disseminated intravascular coagulation)
Relative and controversialSepsis
Elevated intracranial pressure
Anticoagulants
Thrombocytopenia
Other bleeding diatheses
Preexisting central nervous
system disorders (eg, multiple sclerosis)
Fever/infection (eg, varicella zoster virus)
Preload dependent states (eg, aortic stenosis)
Previous back surgery, preexisting neurologic injury, back pain
Placement in anesthetized adults
Needle placement through tattoo

Based on the AAGBI regional anaesthesia and abnormalities of coagulation guidelines:

  • For a normal risk profile for bleeding in obstetric patients having neuraxial block:
  • Wait 12 hours after prophylactic LMWH before neuraxial block
  • Wait 24 hours after treatment dose LMWH before neuraxial block
  • Platelet count >100 in preeclampsia, >75 in idiopathic thrombocytopenia
  • INR <1.4 if on Warfarin or obstetric cholestasis or liver problems
  • Normal FBC/clotting within 6 hours of block for patients presenting after intrauterine foetal death.

These are of course guidelines, but if you are considering deviating from these, please discuss with your supervisor in your local centre.

Risks of epidurals

This is the Labour Pains Epidural information card – the link to translations is here.

Equipment

I’m afraid I’ve watched at least 15 videos on Youtube with epidural insertion but all of them are risky or wrong for IAOC in random ways (resheathing needles/old videos using air and intermittent), so you’ll have to bear with the written down description of how I do it! This is pretty much the same as how NYSORA advocates doing it, with some additional tips.

After consenting the patient, scrub (sterile cap, mask, gown and gloves), prepare your equipment:

  • Chlorhexidine 2% spray or liquid or stick
  • Sterile drape
  • Local anaesthetic syringe + 5ml of 1 to 2% lidocaine, orange + blue needle.
  • 16G Tuohy needle standard size (8cm) or extended size (18G 10cm is usually what’s available in our trust) as required, make sure stylet inside moves easily in and out.
  • Loss of resistance syringe with saline in it (I’m usually very generous with the saline)
  • Epidural catheter hub (small blue piece you can see in the photo below – has a hole to thread epidural catheter through once it’s mounted on the back of the Tuohy)
  • Epidural catheter which needs to be primed with saline by connecting it to the non-luer lock connector + epidural filter and flushing some saline through (the photo below shows it already connected. Make sure it is locked properly because a loose connector is the number 1 reason why people find they can’t give a test dose by injection!). The catheter markings are 1cm spacing, 2 dots = 10cm, 3 dots = 15cm, 4 dots = 20cm. There has been a case report that some catheters don’t accurately have the dots on them – best way to check is to align the dots with your Tuohy needle so you know how much 8cm is (see photo below).
  • Dressing
  • Tape for securing the line up the back
  • Epidural infusion line
  • Pump for patient controlled epidural analgesia + background infusion
  • Bag of local anaesthetic (our usual is 0.125% levobupivacaine + 2mcg/ml fentanyl).
This is the Portex epidural catheter set, very commonly used. The catheter is quite stiff in this set – risk of intravascular puncture, so I tend to give 5-8ml saline into the epidural space before threading.
Align your catheter to your Tuohy and make sure the markings correspond to the depth of your catheter. If it’s wrong, you may need to change your estimation, or just get another catheter if you can.
Protip – open the connector with a non luer-lock syringe tip – don’t try to prise it open with your fingers!
This is what the connector looks like once it is open. the catheter is threaded through the blue tube to the top of the white cap. A filter is connected to that end of the connector, and you can connect your epidural infusion through that filter.

Procedure

Position the patient – this is key. I usually get them sitting close to the edge of the bed toward me, shoulders relaxed, curled over a pillow. My usual instruction to them is to sit up straight, now relax shoulders, now hold pillow (should be up in armpits) as if you’re touching your chin to your knees. I check that they can sit still like this and that the midwives are happy with foetal monitoring before proceeding. Keep noise level to a minimum, ask the patient to follow your voice.

You can also ask the patient to lie in lateral decubitus position (photo below). The landmarks are the same but with lateral position the knees have to be brought as close to the chest as possible, neck flexed ideally with a pillow to support the neck to avoid rolling forward, and the spine needs to be aligned with the edge of the bed/trolley. An assistant may have to help hold the patient’s hip in the right orientation to prevent it rolling away from you. If your alignment is wrong, you’ll make the procedure harder for yourself.

Palpate your landmarks: Feel for the patient’s iliac crests (highest point in pelvis) on both sides. This marks Tuffier’s line and should demarcate L4 (you want to perform the procedure at L3/4). Once you know the horizontal landmark, you need to find the vertical landmark. I palpate the spinous processes to identify midline, and the intersection between midline and Tuffier’s line is where I will perform the procedure.

Intraspinal Analgesia (Epidural and Intrathecal) | Basicmedical Key

Local anaesthetic infiltration: Be generous with the local, I often use all 5ml- I tell the patient that we’re going to numb the skin (saying ‘This might be very painful’ often means it will be – pay attention to language). I usually use the orange needle to give the subcutaneous tissue a small bleb and then aspirating as I go, infiltrate perpendicular to the skin, then switch the orange to a blue needle and go through the same bleb, and again aspirating as I go, go perpendicular to the skin. The blue needle is useful to seek out where the bone is as well to confirm your position midline or otherwise. Give the local about 10-30 seconds to work before going in with the Tuohy.

Finding the epidural space: This is the key part of the process. I usually tell the patient that we’ll start the procedure and there will be some pushing and pulling. I encourage them to sit as still as they possibly can and to avoid sudden movements while the needle is in their back. The below photo is exactly my hand position when I insert the first 3cm of the Tuohy needle – that’s the classically described depth to which you insert it before you hit the supraspinous ligament. Some patients need more, others need less. I usually do this with the stylet still in, ie without the syringe connected.

After you have the Tuohy in the ligaments, the tough connective tissue tends to grip onto the needle and provide some resistance. This is the time to remove the stylet and attach your saline syringe and begin looking for loss of resistance. The NYSORA photo below shows you how I tend to do this (there are other ways of doing it, with palm of hand behind the syringe etc, follow local teaching, but this is a widely accepted method) – notice how part of my hand is stabilising the advancement by resting on the patient’s back. This is important to help guide your needle’s trajectory forward but also keeps you stable. During this time, your Tuohy is traversing the end of the interspinous ligaments and the ligamentum flavum. This is variably thick, so advance slowly at this stage, 1mm at a time. While you have the syringe on the needle, you should be testing for loss of resistance. This can be done by pressing the plunger of your loss of resistance syringe (which is filled with saline or air, but more commonly saline) continuously or intermittently with your finger or the palm of your hand. As the needle enters the epidural space, the plunger of the syringe suddenly “gives.” You have found the epidural space! Yay!

Do not let your excitement stop you from doing the basics at this point – STOP ADVANCING, note how far in you are (the end of the needle is 8cm so count back from there), remove the syringe, put the catheter hub (the little blue piece from the earlier Portex photo, or sometimes it’s a clear piece of plastic) onto the back of the Tuohy and then thread your epidural catheter. Warn the patient that it might feel odd with little tingles down the leg while you do this, that is normal, do not jump! I normally put in about 15cm (3dots on the catheter marking), then remove the Tuohy gently while keeping a grip on the catheter as it enters the patient’s skin. We normally leave 5cm of catheter in the epidural space, so if you remember your Tuohy found the epidural space at 7cm, you should leave in 12cm. I usually do a quick check at this point for the falling meniscus sign (hold the tip of the epidural catheter up to the light and watch the saline level drop as it is being absorbed into the epidural space), although there’s no evidence that the sign confirms or refutes the catheter being in the right place – but I’m a traditionalist. I also aspirate the catheter to ensure no blood comes back out the catheter which may signify intravascular placement.

You would then attach your non luer lock connector + filter to the epidural catheter tip, apply your dressing. There are several types, these are the most common methods:

Just taping over the area with tegaderm (or any clear occlusive dressing) and tape – risky as patients will be moving around in bed and can sometimes accidentally dislodge their catheters
Epifix dressing – slightly fiddly with multiple pieces of tape! The catheter is held in the kink free position on sticky tape.
Lock-it dressing – requires you to thread the dressing over the tip of the catheter before attaching your non-Luerlock connector+ filter, but has a handy clip that locks the catheter in place.
After using the main epidural dressing at the insertion site, I fix the catheter to the patient’s back using strong tape. I sometimes put the tape around the original dressing too to avoid it coming out with sweat/blood.
Oxford University Hospitals have produced an excellent patient information video on epidurals.
NYSORA has produced an excellent video on using ultrasound to guide neuraxial blockade for anaesthetists and has a very good explanation of risks at the end, sonoanatomy and benefits of using ultrasound

Troubleshooting

During the procedure:

This NYSORA table of what to do is excellent and is exactly what I’ve been taught also.

After the procedure (I have summarised the following from NYSORA because the epidural article is so long I thought you might like it all in once place):

Incomplete or no analgesia

Causes:

  • Catheter has migrated
  • Infusion pump disconnected
  • Incomplete blockade (‘window of pain’)
  • Catheter has gone down one side more than the other
  • Poor sacral spread

Identifying the problem:

Ensure you do a full check: History, review dose infused, number of top ups, patient’s status (sometimes OP presentation of foetus + almost fully dilated patient can unmask less sacral spread of the epidural block, especially if it was working well for hours and has suddenly stopped). Examine the patient for the following:

  • Check the back to ensure catheter has not come out (otherwise you may be topping up the subcutaneous tissue and distorting the anatomy)
  • Check sensory dermatomes of both leg comparing one to the other using ethyl chloride spray.
  • Check motor function of legs
  • Feel both legs for warmth – if one side is colder the catheter may be down one side

Solution:

  • Window/spotty block: Top up and turn the patient toward the painful side of the catheter down. So if pain on the left leg, lie left side down just after topping up.
  • Epidural down one side: Withdraw the catheter up to 2cm (minimum length of catheter in space should be 3cm) and place the patient with the painful side of catheter down and top up.
  • May need CSE if poor sacral spread, or position the patient sitting up and top up.
  • If no effect, and patient still very uncomfortable, offer re-site.
  • You may need a higher strength LA eg. 10ml of 0.25% bupivacaine to top up – it will give you the answer faster. If you’ve given this top up and the patient is still in pain, offer re-site.

In the event that you are taking a patient with an epidural that has not been working properly to theatre for a caesarean section, your options are:

  • Top up the patient with a small predetermined dose of your usual epidural top up (our centre uses 2% lidocaine x 20ml and 1:1000 adrenaline x 0.1ml (gives 1:200000 mix) +/- 8.4% sodium bicarbonate x 2ml = approximately 22ml in total) – so for example give 8-10ml of this instead of the whole 20ml to ensure it is starting to work to avoid local anaesthetic toxicity or further distortions of the anatomy. You may decide not to even top it up if the patient has been in pain for the entire time that they’ve had an epidural infusion despite multiple top ups.
  • Resite epidural preferably at a different space and cautiously re-dose if you have time eg. Cat 3
  • Remove epidural and perform spinal – but risk of high or total spinal especially if you’ve already administered a large volume of epidural local anaesthetic while troubleshooting. So you may need to be careful with dose and positioning.
  • Convert to GA if no time for any of the above eg. Cat 1.

Complications

Drug related:

  • Local anaesthetic systemic toxicity
  • Anaphylaxis or allergy to local anaesthetics
  • Nervous tissue injury by local anaesthetic induced mechanism
  • Errors: Wrong drug, wrong mode of delivery (eg. IV drugs given intraepidurally instead)

Procedure related:

  • Mild: Back pain
  • Moderate: Post dural puncture headache, pneumocephalus
  • Severe/life threatening: Subdural injection of high dose local anaesthetic leading to high or total spinal, infectious or aseptic meningitis, cardiac arrest, spinal epidural abscess, epidural haematoma formation, permanent neurologic injuries

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