Obstetric Analgesia and Anesthesia
last authored: Oct 2011, David LaPierre
last reviewed:
Introduction
Pain is a usual significant symptom during labour and delivery, though a wide variation in experience exists. Women should understand their normal response to pain and anticipate their strategies, though labour pain cannot reliably be predicted. Reaching the limits of pain tolerance can lead to high levels of stress hormones, which can decrease uterine contractility. This, in turn, can cause decreased progress, leading to anxiety and a worsening of the experience. Analgesia, which can occur in many ways, can allow release from this harmful cycle.
Visceral pain during labour from the uterus and cervix is transmitted by spinal nerves T10-L1. Somatic pain from pressure on the vagina and perineum is transmitted by the pudendal nerve (S2-S4).
Active involvement of caregivers can help reduce the pain experience, as has been known for many years. This begins before labour with a discussion regarding expected and possible events during labour and delivery, as well as analgesia options and side effects. During labour, the ongoing presence of a health provider with a calm, confident attitude can do much to calm and relax a mother in pain; indeed, it has been said that "a competent, unharassed mid-wife who has time to chat with the patients is the greatest boon in normal childbirth" (Crawford, 1966).
Health care providers should have a thorough knowledge of pain control pharmacology and side effects. No drug is completely risk-free, and efforts should be taken to prevent toxicity to mother and infant. Pain relief should be provided according to the mother's request, if contraindications do not exist. However, many women prefer not to use medications during labour, and they should be supported with effective non-pharmacologic options.
Non-Pharmacological Techniques
Active involvement of caregivers can help reduce the pain experience. This begins before labour with a discussion regarding analgesia options, including side effects. Many women prefer not to use medications during labour, and they should be supported with effective non-pharmacologic options.
Painful stimuli can be reduced by changing positions, ongoing movement, the hands and knees position, and upright positions in women who have not had epidural analgesia. A birthing ball can be helpful for movement and positions.
Touch and massage can be helpful for many women, and counter pressure may also be used. The birth attendant or partner pushes at or just above the sacrum, usually during the contraction. This may be facilitated by a hands and knees position. Some women, however, may find touch or massage irritating and unpleasant.
Superficial heat and cold may also be used. Immersion in water is associated with decreased rate of regional anagesia, though it is unclear what causes this effect. A birthing tub can be used for immersion.
Sterile water injections intradermally can decrease pain and Caesarean section rate. While safe and easy, these injections are initially incredibly painful, which may cause hesitation of use for providers or patients.
Other methods to consider include:
- shifting focus, ie through distraction
- hypnosis and self-hypnosis
- music
- biofeedback
- acupuncture
- transcutaneous electrical nerve stimulation
Medications
Pharmacotherapeutic pain relief should be provided according to the mother's request, if contraindications do not exist and medications are available.
- nitrous oxide
- opioids
- peripheral blocks
- regional analgesia
Nitrous Oxide
Nitrous oxide (NO) is often used for women who have done well without pain control until transition to the second stage and then require a short course of pain control. Deep breaths should be given as soon as a contraction begins and stopped once the contraction subsides.
Opioids
A variety of opioids are often used, with preference for shorter-acting drugs such as morphine or fentanyl. These may be given IV, IM, or subcutaneously, and are usually co-administered with an anti-emetic such as dimenhidrinate.
Meperidine is often avoided given the long half-life of metabolites that can remain in the infant.
Peripheral blocks
Pundendal nerve blocks can be very effective in the second stage of labour. Ten ml of 1% lidocaine, with or without epinephrine, is usually injected on each side of the pelvis, using a fanlike pattern focused around the sacrospinal ligament.
Perineal analgesia is used to repair lacerations and episiotomy, with injections into the mucosa and submucosa surrounding the injury.
Regional Analgesia
Regional analgesia can be helpful for pain control if other options are deemed inadequate, and a growing number of women around the world choose regional analgesia. In some hospitals, epidural rates approach 75%.
Epidurals are most commonly used, in which local anaesthetic is injected into the epidural space containing fat, lymphatics, and the internal venous plexus. Spinal blockade involves local anaesthetic infiltration directly into the subarachnoid space. This is less common, though faster than epidural analgesia.
For vaginal delivery, blockade of T10-S5 is ideal, while a Caesarean section necessitates block from T4-S1. Medications used commonly include lidocaine or bupivicaine. Fentanyl may be added to increase speed of onset and decrease shivering.
The process for epidural analgesias is as follows:
- maintain recuscitation equipment and drugs to address complications
- provide a 500-1000ml bolus of Ringer's lactate or normal saline to prevent hypotension
- monitor maternal and fetal heart rate continuously, and the maternal blood pressure, every 1-2 minutes during and 15 min after anaesthetic is given
- position the mother in a lateral decubitus or sitting position
- throughly cleanse the skin
- enter the epidural space between the lumbar vertebrae; a loss of resistance suggests penetration through the ligamentum flavum
- advance the epidural catheter 3-5 cm
- aspirate
- provide a test dose of lidocaine or bupivicaine with epinephrine in between contractions in order to rule out entry into the intravascular space (which would be suggested by tachycardia)
- provide an analgesic dose
- assess analgesia with ice or pinprick, after 15-20 min, aiming for T10 (bellybutton) blockade
- if no blockade is present, replace catheter; if blockade is asymmetric, withdraw catheter 0.5-1cm and inject further analgesic
- maintain mother in lateral or semilateral position to avoid vessel compression
- monitor fetal heart continuously and the maternal blood pressure every 5-15 minutes
- monitor analgesia at least hourly
Epidurals prolongs labour, increases the need for oxytocin augmentation, and increases the need for forceps delivery, though without increasing Caesarean rates or adversely affecting the neonate. Epidurals can be used in early labour, when the cervix is dilated to at least 1 cm, without apparent consequence on the rate of labour, as compared with waiting after active labour begins (Wang et al, 2009).
High dose motor block epidurals result in non-ambulation, while women with low dose epidurals are often able to walk. Low dose epidurals are also associated with, less motor block, hypotension, and fetal malposition, as well as a shorter second stage.
Absolute contraindications to regional anesthesia include:
- maternal hypotension refractory to treatment, eg severe hemorrhage
- coagulopathy
- LMW heparin taken within past 12 hours
- untreated bacteremia
- skin infection over injection site
- increased intracranial pressure, eg due to tumor
- neurological disease
option |
indications |
adverse effects |
epidural |
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spinal |
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combined spinal/epidural |
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general |
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Resources and References
Crawford JS. 1966. Obstetric analgesia and anaesthesia - the current scene. Postgrad Med J. 42: 351.
Wang F et al. 2009. Epidural analgesia in the latent phase of labour and the risk of Caesarean deliveyr; a 5-year RCT. Anesthesiology. 111(4):871-80.
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