Anaesthesia

1 Anaesthesia


These drugs depress part of the central nervous system, causing the loss of sensation in a part of or in the whole of the body. There are two main groups, inhalational and intravenous.


These drugs are the specialty of an anaesthetist, although midwives do use certain ones, e.g. 50% nitrous oxide and 50% oxygen via Entonox™ apparatus (or piped supply), or local agents such as lidocaine for perineal infiltration and bupivacaine for epidural top-ups. This chapter explores the anaesthetics used by midwives and not those administered by anaesthetists alone. It is also of note that in the 2006–2008 Saving Mother’s Lives, the 8th Report of the Confidential Enquiries into Maternal Deaths in the United Kingdom (Centre for Maternal and Child Enquiries, 2011), anaesthesia was directly responsible for seven deaths (3%), although anaesthesia contributed to 18 (a considerable number), several where the outcome was compromised by the anaesthetic management and provision of high-dependency care.


Midwives need to be aware of the action of anaesthetics, and maternity units need to provide recovery areas for patients having a caesarean section and high-risk clients.


The student should be aware of:



image the difference between analgesia and anaesthesia


image the difference between local, regional and general anaesthesia


image the physiology and pathophysiology of the perception of pain


image the physiological principles underpinning epidural anaesthesia


image problems that occur with obstetrical anaesthesia, i.e. the effects of progesterone on the mother, the presence of two patients rather than one, the pressure of the gravid uterus


image updated resuscitation techniques


image how to apply cricoid pressure if requested to in an emergency.





BP

Nitrous oxide

Proprietary

Entonox™ (BOC Healthcare)

Group

Anaesthetic, inhalational

Uses/indications

Analgesia during labour

Type of drug

POM, midwives’ exemptions or PGD

Presentation

Colourless gas with slightly sweet odour in cylinders – blue with blue and white quarters at the valve end and labelled Entonox
Cylinders should be: stored under cover; not stored near stocks of combustible materials
F size cylinders and larger should be stored vertically. D size cylinders and smaller may be stored horizontally
ensure cylinders are maintained at a temperature above 10°C for at least 24 h before use to ensure the gases are mixed correctly. Care needed when handling and using gas-filled cylinders, including transportation – cylinders should be separate from the driver area, securely held, and emergency procedures known to the driver. Use of a hazard warning label is essential

Dosage

50% nitrous oxide : 50% oxygen, self-administered via mask or Entonox™ equipment

Route of admin

Inhalational

Contraindications

Pneumothorax, facial or jaw injuries, diving accidents, overt drunkenness

Side effects

Drowsiness, nausea, vomiting

Interactions

None specific, but BNF (2011) indicates that it may be appropriate to consider that nitrous oxide enhances the effect of other anaesthetics or analgesics, and is similar in action to a general anaesthetic. Relevant interactions to obstetrics are that:

Anxiolytics and hypnotics – enhances the sedative effect


Methyldopa – increases the hypotensive effect


Pharmacodynamic properties

Medical gas – colourless
Oxygen – odourless and present in the atmosphere at 21%; nitrous oxide – sweet smelling and potent analgesic from endorphin release when at 25% concentration, but weak anaesthetic

Fetal risk

Can depress neonatal respiration (BNF 2011). It is also of note that it may increase the risk of spontaneous abortion and low birthweight in female workers where levels of exposure are raised, i.e. operating theatres, labour wards

Breastfeeding

No data available on controlled studies during breastfeeding


BP

Lidocaine hydrochloride

Proprietary

Lidocaine hydrochloride 1% and 2% (Goldshield Group Ltd)

Group

Local anaesthetic

Uses/indications

Perineal infiltration – prior to episiotomy or suturing, or for nerve blocks
Emergency use, e.g. cardiac arrest – see Chapter 25 for indications, usage, and dosage

Type of drug

POM, midwives’ exemptions or PGD

Presentation

Glass or polypropylene ampoules 2, 5, 10 or 20 mL, with strength, 1% or 2%, indicated on the ampoule
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Jul 11, 2016 | Posted by in MIDWIFERY | Comments Off on Anaesthesia

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