Analgesia and Anaesthesia







‘No greater boon has ever come to mankind than the power thus granted to induce a temporary but complete insensibility to pain’.


Howard Wilcox Haggard


Devils, drugs, and doctors. the story of the science of healing from medicine-man to doctor . London: William Heinemann (Medical Books) Ltd, 1929.



Introduction


Labour is an intense and painful experience for most women, many of whom find it worse than they expected. For the woman having her first baby there is often additional fear and anxiety about the unknown.


Maternal pain and stress increase maternal sympathoadrenal activity which may lead to inco-ordinate uterine action, reduced uteroplacental perfusion, increased fetal oxygen requirements and adverse fetal effects.


There are two schools of thought around how women might cope with the pain of labour. The first suggests that in the 21st century there is no need to suffer unnecessarily during labour and that effective analgesia is available and should be offered. The second sees pain as part of the experience of birth and advocates that women should be supported and encouraged to ‘work with the pain’ of labour. Whatever the woman’s viewpoint, it is fundamental that she should be treated with respect and as an individual. Effective forms of pain relief are not necessarily associated with greater satisfaction with the birth experience and, conversely, failure of a chosen method can lead to dissatisfaction.The challenge for healthcare professionals is to recognize and respond appropriately to changes in the woman’s stance during labour.


Pain management strategies include non-pharmacological interventions (that aim to help women cope with pain in labour) and pharmacological interventions (that aim to relieve the pain of labour). Most methods of non-pharmacological pain management are non-invasive and appear to be safe for mother and baby; however, their efficacy is unclear, due to limited high-quality evidence. There is more evidence to support the efficacy of pharmacological methods, but these have more adverse effects.




Pain Pathways


In the first stage of labour the origin of pain is from effacement and dilatation of the cervix and formation of the lower uterine segment. These painful impulses pass through the hypogastric plexus to the lumbar sympathetic chain and, via the dorsal horn, to T10, T11, T12 and L1 at the spinal cord level. The nociceptive information passes from the dorsal horn via the spinothalamic tract through the brain stem and medulla to the posterior thalamic nuclei. From here fibres pass to the somatic sensory cortex and thence to the frontal cortex. These pathways help regulate the associated responses to pain, such as anxiety, adverse reaction and learned behaviour.


In the second stage of labour, in addition to the uterine contractions, pain results from stretching of the pelvic floor and perineum. These painful stimuli enter the spinal cord via the somatic pudendal nerves: S2, S3 and S4.




Methods of Pain Relief


Analgesia provides a varying amount of relief for a painful condition. Anaesthesia provides total relief of pain which is necessary for a surgical operation.


Non-Pharmacological Methods


Most of these techniques rely on counter-stimulation as the basis for their success.


Prepared Childbirth


The so-called ‘natural childbirth’ movement started in the early part of the 20th century in response to the ‘twilight sleep’ era at the beginning of the century with its excessive use of narcotics and sedatives. The basis of childbirth preparation is that women who are properly prepared can control the pain of labour themselves and either do without or reduce their need for pharmacological pain relief. There have been a number of prominent, often consumer-led, movements following the lead of Grantly Dick Reid in Britain, Velvoski in Russia and Lamaze and Le Boyer in France. In addition to these specific techniques many regions and hospitals will provide antenatal classes with information about the various methods of pain relief in labour (both non-pharmacological and pharmacological) as well as infant care classes, with the overall aim of engendering confidence in the couple.



Natural Childbirth


‘It is not generally recognized that in childbirth there is an “emotional labour” which is as definite and important as its physical counterpart. This must be understood if parturition is to be conducted as a physiological performance … Is a woman pained and frightened because her labour is difficult, or is her labour difficult and painful because she is frightened? … Pain is the mental interpretation of harmful stimulus, and fear the intensifier of stimulus-interpretation. The biological purpose of each is protective. The physiological reaction to each is tension’.


Grantly Dick Read


Natural childbirth. London: Heinemann, 1933



Continuous Support


No woman in labour should be left alone. In addition to the trained nurse or midwife many women will have social support in the form of their male partner or other family member and some will choose to have a specially trained lay person (sometimes known as a doula). These personnel can provide reassurance, encouragement and explanation during labour. In addition, they may help guide counter-stimulation techniques such as touch, massage, change of position, baths, ambulation, music, etc. Cultural factors may dictate the personnel and techniques used for support to the woman in labour.


Hypnosis


This often requires extensive antenatal training sessions and individual receptivity to hypnosis varies. In some cases the hypnotherapist also needs to be present during labour. When successful, the results of hypnosis are very impressive; however, the time and personnel commitment required are such that this is not practical for the majority of women.


Transcutaneous Electrical Nerve Stimulation (TENS)


This consists of a small, battery-driven pulse generator which is connected to two pairs of electrodes on either side of the spine overlying the dermatomes, T10 to L1, and attached to the skin with adhesive tape. When activated it causes a tingling sensation in the skin under the electrodes. The strength of the stimulus can be adjusted by the control generator. It is said to be most helpful in early labour with back pain and may stimulate the release of endorphins. The woman can remain ambulant but TENS equipment may interfere with electronic fetal heart rate monitoring using a fetal scalp electrode.


Intradermal Injection of Water


Using a 1 ml syringe and a 25-gauge needle, injections of 0.05–0.1 ml of sterile water are injected into the skin in four sites: one on each side over the posterior iliac spines and one each just medial and below the upper sites. This causes intense stinging for about 30 seconds and may provide amelioration of back pain for 45–90 minutes. It is thought to act by counter-irritation, possible release of endorphins or, according to the gate-control theory of pain, the intense superficial sensory stimulation may inhibit pain signals in the deeper, slower nerve fibres. In general this technique may give short-term relief from backache but rarely influences the total analgesia requirements.


Acupuncture


This and related procedures may have application in societies which have practitioners skilled in this technique and in women who are knowledgeable and receptive to this method.


Pharmacological Methods


Inhalation Analgesia


The safest and most practical agent for inhalation analgesia is nitrous oxide. The aim is to administer subanaesthetic concentrations of nitrous oxide providing analgesia without loss of consciousness and with retention of protective laryngeal reflexes. Nitrous oxide is absorbed from and excreted by the lungs. It crosses the placenta but is also eliminated efficiently and there are no untoward neonatal effects. It has no effect on uterine contractility. The exact mode of action is unknown but it works at the level of the brain, producing analgesia in low doses and anaesthesia with higher and sustained doses.



First Use of Nitrous Oxide/Oxygen Inhalation Analgesia in Labour


‘The woman should be coached to exhale deeply and then inhale as much gas as possible … It is important to begin the first anaesthesia early in order to obtain good pain relief; a late start will prevent the deep inhalation and, thus render the effect incomplete … Thereafter the inhalation is begun at one-half to one minute prior to the anticipated next contraction. Two to five breaths of the gas mixture usually suffice to produce the desired effect’.


Stanislav Klikovich


Über das Stickstoffoxydul als Anaestheticum bei Geburten. Arch Gynäk 1881; 18:81–108

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Jul 21, 2019 | Posted by in OBSTETRICS | Comments Off on Analgesia and Anaesthesia
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