Labour Analgesia: What is it?
Labour Analgesia is the relief of pain during labour contractions. Medications that provide pain relief are called analgesics. These medications work by blocking the pain signals that pass along the nerves in the body to the brain.
The pain that women experience during labour is affected by multiple physiological and psychosocial factors and its intensity can vary greatly. Most women in labour require pain relief. The contractions usually become more painful as labour progresses. If medication is used to start off labour or speed up labour, contractions may be more painful.
Types of Labour Analgesia
The pain relief methods available include:
- Neuraxial analgesia for labour
- Epidural Analgesia
- Combined Spinal-Epidural Analgesia (CSEA)
- Alternative methods of pain relief
- Entonox (laughing gas)
- Parenteral Opioids (Remifentanil Patient-Controlled Analgesia and intramuscular Pethidine)
Neuraxial Analgesia for Labour
Neuraxial Analgesia is one of the most effective and reliable ways of relieving labour pain. There are two types of Neuraxial Analgesia available:
Epidural Analgesia (EA)
In Epidural Analgesia (EA), an injection is done to locate the epidural space within the back-bone canal and a fine plastic tube inserted. Pain relief is accomplished by the administration of medications through the small tube via a continuous infusion pump or an automated patient-controlled pump.
Combined Spinal-Epidural Analgesia (CSEA)
In Combined Spinal-Epidural Analgesia (CSEA), in addition to the above, an initial dose is given for pain relief into the spinal space, which provides for a faster onset than epidural injection. Similarly, a fine tube is inserted to deliver the medications continuously throughout labour.
Neuraxial Analgesia has the following benefits:
- It is safe and gives consistent, reliable pain relief in labour.
- The placenta delivery and therefore, the baby, may get better blood flow during and between contractions.
- It reduces many stress-related responses of the body to pain, which is beneficial for patients with high blood pressure, pre-eclampsia, heart problems or diabetes.
- It can be extended to provide Anaesthesia for emergency Caesarean if time allows.
The decision for EA/CSEA should be left to the discretion of the Anaesthetist, as dictated by the stage and progress of labour.
Complete pain relief cannot be guaranteed throughout labour as different women respond differently. A minor degree of pain may still be felt with EA/CSEA, especially near the time of delivery of the baby.
Alternative methods of pain relief
Entonox (laughing gas)
Entonox, also known as “laughing gas,” is made up of 50% nitrous oxide and 50% oxygen. It is delivered through a breathing mask or mouthpiece. Although Entonox does not eliminate labour pain as effectively as EA/CSEA, it may help to alleviate it. It can be used throughout labour. To get the best effect, timing is important. The patient should start inhaling the Entonox as soon as she feels a contraction is coming on, as this will give her the full effect when the pain is at its worst.
Intramuscular Injection of Pethidine
Pethidine is an opioid medication that may be given as an intramuscular injection into a large muscle in the arm or leg. The pain relief is often of limited duration and effectiveness.
Remifentanil Patient-Controlled Analgesia (Remifentanil PCA)
Patient-controlled analgesia (PCA) is an intravenous drug delivery system that allows patients to administer their own pain medication when needed. The medication used in this case is a short-acting opioid called Remifentanil. The PCA device is programmed to administer a fixed dose of Remifentanil upon demand, with appropriate pre-set limits on maximal dose of medications delivered in a fixed time interval. To use Remifentanil PCA effectively, patients need to activate a dose of pain relief medication when she feels the onset of a contraction.
When using the Remifentanil PCA device, patients will also be provided with oxygen supplementation and continuous monitoring of oxygen saturation through a finger-probe.
Current medical literature suggests that Remifentanil PCA is less effective than EA/CSEA in providing labour pain relief. It may be considered in patients who cannot or prefer not to have EA/CSEA e.g. bleeding tendencies, previous spinal instrumentation, blood clotting abnormalities, heart disease, severe systemic infection and previous back surgeries.
Complete pain relief cannot be guaranteed throughout the labour as different women respond differently. Some degree of pain may be felt near the time of delivery of the baby but the patient can continue to use Remifentanil PCA to relieve pain up to the time of the delivery.
Complications of Labour Analgesia
It is generally safe to receive EA/CSEA. The side effects are usually predictable, short-lived and not harmful. They can be divided into:
Common side effects
- Loss of feeling
Numbness of the legs and the lower part of the body may occur. Bladder sensation may also be lost and hence the patient may not have the urge to pass urine. A urinary catheter is usually placed after neuraxial analgesia procedure.
- Muscle weakness
Some weakness of the legs will exist but this is usually not severe, and the weakness should wear off when the drug effect subsides.
This may occur although the patient may not be feeling cold. This usually does not require any treatment.
Generalised mild itch is more common after CSEA than EA. This usually does not need any treatment as it is self-limiting.
This may result from a lowering of blood pressure with the application of CSEA. Proper positioning and blood pressure-raising drugs may be used for treatment.
- Bruising and backache
Occasionally, patients may experience bruising over the needle injection site. If this occurs, it usually resolves in a few days. Backache is common among pregnant women after delivery, with or without the use of labour epidural. Studies have not been able to establish a causative link between severe long-term backache and EA/CSEA.
On occasion, a mild electric shock-like feeling may be experienced in the lower back or legs during the insertion of the epidural catheter. Some patients may have persistent numbness over some areas of their legs. This is usually temporary and will resolve spontaneously on its own.
Although the use of labour epidural analgesia has been associated with development of maternal fever, it rarely results in higher temperatures. However, if the patient’s fever is greater than 38 degrees, the patient and her baby may be investigated for infection, be prescribed antipyretic / antibiotic treatment and have an increased length of hospital stay.
- Effects on the baby
EA/CSEA does not harm the baby, although a transient drop in the baby’s heart rate may occur. If this occurs, it is usually temporary and may be treatable with medications.
- Spinal headache
The risk of spinal headache is about 1% after EA/CSEA. This characteristic headache is felt in the forehead and the back of the head and neck and is worsened by the upright position. Symptoms usually improve in 7 to 10 days. The headache is treatable with simple analgesics and a procedure called ‘epidural blood patch’ if it is severe or persistent.
- Failure to achieve epidural analgesia/ No analgesia
Rarely, the epidural may not work or patients may get a patchy/ inadequate block. This may be due to reasons such as migration of epidural catheter out of the epidural space (due to movement, wet dressing etc.), suboptimal placement of the catheter and disconnection of catheter from the infusion pump. Sometimes, if there is rapid progression of labour (rapid cervical dilatation in a short period of time), the EA/CSEA may not have adequate time to work. If labour pain persists after epidural insertion, patients should inform their Anaesthetist immediately so that the problem can be rectified. The epidural catheter may need to be adjusted or reinserted in some instances through a repeat procedure.
- Accidental high block which might affect normal functioning of other muscles and organs
- Breathing difficulty
- Permanent nerve damage, resulting in numbness or weakness in thigh, leg or foot
- Serious spinal/brain infection
- Dizziness or nauseous if used between contractions or for prolong periods
- Dry mouth
Intramuscular Injection of Pethidine
- Effects on the baby
If pethidine injection is received in more advanced stages of labour when birth is imminent, the pethidine may cross the placenta and case breathing difficulties in the newborn.
The side effects are generally predictable and short-lived, but an antidote may need to be given in severe cases.
- Nausea/ Vomiting
In severe cases, treatment may be given intravenously.
- Drop in Maternal Heart Rate or Blood Pressure
This may occur but is usually transient and not severe. Proper positioning and heart rate- or pressure-raising drugs may be given to treat severe cases.
- Respiratory Depression of the Mother
This may occur from the use of Remifentanil. As the patient is monitored continuously, this can be detected promptly and appropriate treatment given. In mild cases, Anaesthetists may increase the oxygen supplementation and/or decrease the dose of Remifentanil given. In severe cases, the pump may be stopped and an antidote given.
- Sedation of the Mother
Transient drowsiness may occur from the use of Remifentanil. It usually does not require any treatment but in severe cases, we may decrease the dose of Remifentanil or stop the PCA device.
- Life threatening complications, whilst rare, include:
Muscle rigidity, breathing difficulty and complete cessation of breathing.
- Effects on the baby
In studies, Remifentanil has not been shown to harm the baby. However, there are theoretical risks of causing respiratory depression and sedation in the newborn. In the event that this occurs, a neonatologist will attend to the baby immediately.