Wednesday, August 23, 2006

Pain Relief in Labour


Written for www.mumsandbubs.co.uk


Many women are frightened of labour and childbirth, everyone knows of a horror story where labour went on for three weeks, where the pain was constant throughout, and was like being burned alive. Chances are, it won't be quite that bad.

50% of women interviewed after delivery in a recent study said that their pain had been severe or very severe, so it's worth taking seriously and investigating the options for analgesia (pain relief). Primips (women with their first baby) are more likely to experience pain than multips (had one or more already). Babies who are not in the ideal position (e.g. back to back / cheek presentation) will cause more pain. Obstructed labour is more painful than normal labour.

Psychological factors:
Studies have suggested that women entering labour with the right frame of mind can experience less pain, having a supportive birth partner (women better than men), and knowing that labour will only last a finite amount of time can help. Unfortunately some women believe in the power of the mind to such an extent that they are expecting painfree labour - only to lose all self-confidence when it does hurt, making it hurt more.

Position:
During pregnancy you are told not to lie flat on your back, for reasons of aortocaval compression - your baby's weight will compress your major blood vessels, and can compromise the baby or make you dizzy and light headed. However, the most convenient (for the midwife) position for delivering your baby is flat on your back with your legs in stirrups! This position is possibly the most uncomfortable way to push and used to be encouraged, but more recent thinking allows for all manner of manoevures. The most natural position is probably on all fours, or squatting. These two are associated with less pain, so there is some benefit to remaining mobile. Many women find that a warm bath, or the water birth pool can be very effective at reducing pain.

TENS:
Transcutaneous Electrical Nerve Stimulation (TENS) is a device which attaches to your back. Tiny electrical impulses are passed between two/four/six electrode pads, which are stuck either side of your spine. The idea is to make some of the nerves going into your spinal cord fire impulses to the brain. These nerves would normally carry 'touch' information. 'Touch impulses' takThis is a super-charged version of having your partner rub your backe priority over 'pain impulses' which are carried by different nerves. The pain sensation is blocked on the way to the brain, so pain relief is acheived. This is a super-charged version of having your partner rub your back. Be aware that some hospitals require you to book a TENS machine in advance, so check with your midwife.

Non-invasive analgesia:
The only drug analgesia available without needles is paracetamol and entonox ("gas and air"). Paracetamol can of course be used without the need for monitoring, and can be quite successfully taken in early labour. Make sure you do follow the dose instructions on the packet if you are taking it at home.

Entonox is a gas mixture of 50% Oxygen and 50% Nitrous Oxide ("laughing gas"). It is an excellent pain relieving agent, and is breathed through a demand valve system. Most delivery suites have it piped through the wall, some have it straight from a bottle. When breathed deeply over several consecutive breaths, the level in the blood quickly increases. This level is directly linked to the amount of pain relief.

It is important to realise that there is an interval between starting to breath the entonox and getting pain relief, otherwise you will start breathing the gas too late, the contraction will hurt, and then you'll get dizzy, light-headed, and giggly after the contraction has faded. The gases coming out of the wall has no water vapour in it (air normally does), so using it will give you a dry mouth and you will get thirsty very quickly.

The main concern with entonox has been the recent suggestion that it can upset the bone marrow's ability to make DNA (and therefore cells) if breathed for long periods of time due to suppression of the enzyme methionine synthetase. Evidence seems to suggest that this doesn't become significant for mother or baby until entonox has been used continuously for over 24 hours. To be on the safe side, some maternity units try to restrict its use to less than this time.

Injections:
Pethidine:
Since the 1950s, midwives have had the ability to administer Pethidine to labouring mothers. This tradition is perhaps in need of some review, as more appropriate opiate based painkillers have been discovered and experimented with. Midwives understandably are reluctant to give up any potential means to help their patients, so Pethidine is often the drug recommended first. It is a strong opiate drug, similar to morphine. It is often found to be excellent at relieving the pain of contractions, and is given as an intra-muscular injection (shoulder, thigh, or buttock).

The half-life of Pethidine is about 3-7hours, and this is about as long as you can hope for it to last. There are some downsides of course, which make it less than ideal. Pethidine can make you feel drowsy, nauseated, vomit, and in some cases hallucinations have been reported. It may reduce the frequency and/or strength of contractions whilst it is working. Pethidine crosses the placenta, and is less able to get back into the maternal circulation. This means that your baby gets a stronger dose than you doYour baby gets a stronger dose than you do. This can make baby quite 'sleepy', and may affect the baby's heart rate trace. The real rub is that one of the metabolites of Pethidine (a substance made when Pethidine is broken down) called Norpethidine is quite toxic to baby. Norpethidine's half-life is approximately 21 hoursin the mother, and up to three times that in the baby, can cause convulsions/fits if in high enough levels when baby is born. It is important therefore that your midwife accurately predicts that your baby won't be born for at least 4 hours if you have pethidine.

Meptid/Meptazinol:
A recent addition to the midwife arsenal is a drug very similar to Pethidine, it works much the same way, but has less severe side-effects. Unfortunately, in my experience, women report that it provides less effective analgesia too. It is given in the same way as Pethidine, but baby is OK if born within 2-3 hours.

Patient Controlled Analgesia (PCA):
Some maternity units are able to provide a special pump which is attached to an intra-venous drip. This pump has a button which the mother can press to release a small quantity of opiate into the blood stream.

A PCA Machine

This way, the mother can precisely control the dose on board, balancing need for pain relief with side-effects. The actual drug in the system varies from unit to unit, but there are two main concerns:

If your baby is healthy, the main concern is not to allow high peak levels of a long acting drug to affect the baby - so a potent, short acting drug such as alfentanil is used.
If however, you are one of the very unfortunate who are delivering a stillborn, a PCA with a longer acting drug such as morphine could be used, as there is no concern about intoxicating the baby, and pain relief is more easily acheived.

It is not possible for you to overdose with a PCA device, as they are designed with a lockout period. Commonly, you are able to get a dose at most every five minutes.

Epidural:
Anatomy of the spine

This is the only mode of analgesia that potentially offers complete pain relief. It is a small plastic tube that is inserted through a needle into the epidural space (see above) in your back. The needle is then removed, and the tube can be used to inject local anaesthetics to provide the block. It is inserted by an anaesthetist - a specially trained doctor with experience in all types of anaesthetics.

An epidural is inserted very cleanly to minimise the chance of introducing infection. The mother must sit very still, any sudden movements may increase the chance of complications. It is dangerous to insert any needles into the back when the mother has a contraction, as the pressures in the tummy and back increase dramatically. If a contraction does occur, the anaesthetist just needs to be informed, and he/she will stop until it passes. It is still OK to use entonox during these contractions, it helps you to stay still!

There are risks associated with having an epidural, but they are generally very safe. They can drop your blood pressure, which can make you feel dizzy or light-headed. Your baby must be monitored in case the drop reduces the blood supply to the placenta. Before an epidural is sited, an intravenous drip is placed in your hand/arm so that fluids or drugs can be given to stop the drop in blood pressure from becoming a problem.

In approximately 1 in every 100 epidurals in labour, the needle or plastic tube puncture the membrane between the epidural space and the subarachnoid space. The subarachnoid space is filled with nerves floating around in fluid. The hole made by the needle/tube can allow this fluid to leak out, giving the mother a headache. It is important to mention a headache to a healthcare professional should it occur. The Post Dural Puncture Headache (PDPH) is like a migraine, is worse when sitting, standing, or straining on the toilet. It is made better by lying down, and is sometimes associated with neck stiffness or changes in vision. If you do get this complication, one of the most effective treatments is the 'blood patch'. This is another epidural needle inserted into the back, and 20mls of the mother's blood inserted into the space. The blood forms a clot over the hole, stopping the leak while the hole fixes itself over the following six weeks.

Often, an epidural will cause weakness in the legs, so the mother is usually confined to the bed. This is not the case in some units, where a low-dose 'mobile' epidural is used. It is still currently uncertain whether epidurals cause an increased chance of instrumental delivery (Ventouse / Forceps) recent evidence is that there is, but there are so many other factors that it may be impossible to tease out the difference. There isn't an increased chance of having a Cesarean section if you have an epidural.

There are two different dose regimes that could be used. One is to give bolus top-ups of local anaesthetic each time it starts to wear off, and the other is to give a continuous infusion. Both are similar in their effectiveness, the bolus technique has been shown to have a lower total dose overall, and gives a longer time until other forms of analgesia is required post-natally.

Many women are worried about the risk of nerve damage from the insertion of an epidural. Recent audits suggest that the chance of any temporary nerve damage only occurs in 1 per 10,000 epidurals, and permanent nerve damage only occurs in 1 in 20,000 epidurals, so they are considered to be particularly safe.

Summary:
There are many techniques for dealing with the pain of labour and delivery, some are simple, and some are more complicated, but more effective. It is important to make informed decisions about what you want in your labour, and to get advice from your healthcare providers, they can give you more information and discuss what's best for you.

Written by Dr. Michael Greenway, SHO in Anaesthesia



9 Comments:

At 6:43 AM, Blogger figur8 said...

Thanks for your article, Michael. It was very informative.

 
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