Dr James F Peerless March 2015 Pain Relief in Labour

Introduction Potentially the most painful experience a woman will encounter Experience of labour and pain severity varies hugely between women Multiple factors, including social and cultural Provision of good information prior to labour shown to increase the feeling of control.

Objectives Anatomy & Physiology Non-regional techniques – Non-pharmacological Methods – Pharmacological Methods Regional techniques – Epidural

Anatomy & Physiology

Physiology of Labour Stages of Labour – First onset of labour to effacement and full cervical dilatation – Latent – slow cervical dilatation, weak contractions – Active – strong, effective contractions – Second full dilatation to delivery of the baby – Third delivery of the placenta

Pain Transmission First Stage – Distension of the lower uterine segment and cervical dilatation – Contraction of the uterine muscles – C-fibres transmit pain via T10-L1 uterine sympathetics Second Stage – Stretching of vagina and perineum – Pudendal nerve (S2-4) from sacral plexus

The Ideal Obstetric Analgesic Effective and simple Co-operation and consciousness preserved No effect on labour progression Low complication risk for mother and baby

Non-pharmacological Methods

TENS Based on gate theory Non-invasive, easy to use ?Useful in latent stage Not endorsed by NICE (CG 190, 2014) “There is high-level evidence that TENS is not an effective analgesic in established labour. “There is no high-level evidence on the analgesic effect of TENS in the latent phase of labour.”

Water Pool Warm water – inhibits pain transmission – supports the gravid uterus Popular, backed by Government Health Committee Limited access, cannot be used with other methods Cochrane review: no difference in pain relief between immersion/non-immersion groups

Alternative Methods Hypnotherapy – Meta-analysis showed no evidence Aromatherapy – No evidence – (1 RCT compared lemongrass with ginger) Homeopathy – No evidence

Alternative Methods Continuous support – Shown to improve the psychological and physiological aspects of labour – Cochrane review of 15 RCTs shows reduced intrapartum analgesia and improved experiences

Pharmacological Methods

Remifentanil PCA Ultra-short acting fentanyl derivative – Rapidly hydrolysed by red-cell esterases – No accumulation, even following prolonged infusion – Bolus ~15mcg (2min lockout) Superior pain relief cf. pethidine Good alternative when epidural is contraindicated Requires high-dependency monitoring May require supplemental oxygen

Entonox N 2 O/O 2 mixture in obstetric practice since 1880s Low blood-gas sol. coefficient allows rapid wash-in and out Technique of use important – 10 breaths achieves near-maximal effect – Requires timing with contraction pain Self-control of analgesia gives mother control SF X : drowsiness, disorientation, nausea – Hyperventilation  alkalosis (vasoconstriction and reduced uterine blood flow)

Pethidine (Meperidine) Legally available for independent use by midwives since 1950 Phenylpiperidine derivative Acts on mu and kappa opioid receptors Weak base; 28x more fat soluble than morphine Metabolised to norpethidine

Pethidine Presentation – 50 mg tab – Clr clrlss soln 10/50 mg.mL -1 Dose – mg 4hrly IM, IV, PO Action – Mu and kappa opioid receptors

Pethidine Pharmacodynamics – CVS Anticholinergic properties Histamine release  hypotension – RS Respiratory depression Obtunds response to hypoxia and hypercapnia – CNS 0.1 potency of morphine Euphoria and sedation, hallucinations and dependence – AS Reduced gastric emptying N&V

Pethidine Pharmacokinetics – A 100% bioavailability IM – D Bound to alpha-1 glycoprotein Crosses the placenta and achieves higher concentrations – M Pethidine  norpethidine  norpethidinic acid Accumulates in renal failure Norpethidine has convulsant properties – E Half-life 4-20h; 13-62h in neonates

Regional Techniques

Epidural Analgesia Introduced for labour in 1970s. Controversy still remains on their effect on the labour process Uptake rate: – 25% of women in the UK; 66% of women in the US

Effects of Epidurals More likely to need an instrumental delivery – Variable, according to dosing regime No increase in LSCS; self-selecting population – Long, painful labours more likely to require analgesia Quality of analgesia superior to other techniques – But not necessarily maternal satisfaction

Effects of Epidurals Duration of Labour – First and second stages minimally increased – ?significance Effect on neonate – No consistent differences found – Some studies show transient bradycardias on initiation – ?significance

Indications Maternal request Slow or painful labour High-risk pregancies: PIH & PET Cardiac or respiratory disease High-risk foetus Multiple pregnancy Raised BMI Trial of labour (VBAC)

Contraindications Absolute – Systemic/localised infection – Maternal refusal – Coagulopathy/anticoagulation – Insufficient staff Relative – Hypotension/hypovolaemia – Neurological disease – Gross spinal deformities

Epidural – Advantages Greater maternal satisfaction Maternal participation (no sedation) Reduced catecholamines  improved placental blood flow

Epidural – Disadvantages Prolonged labour; increased instrumental rate Failure/incomplete/patchy analgesia Urinary retention Hypotension Subdural block Accidental IV injection Total spinal PDPH (1:100) Neurological injury (1:25 000) Abscess (1: ) Haematoma (1: )

Failing Epidural History – From midwife and patient – Time of last top-up – Did it ever function properly? Examination – Epidural site – Quality and block height – Bilateral warm feet?

Failing Epidural Solution(s) – Withdraw catheter – Large volume, low dose mixture, e.g. 20mL – 10mL x 0.25% l-bupivocaine – Fentanyl mcg – Resite

Reference Sasada & Smith, Drugs in Anaesthesia and Intensive Care, 3 rd Edition Fortescue C, Wee M. Analgesia in labour: non- regional techniques. CEACCP, 2005 McGrady E, Litchfield K. Epidural analgesia in labour. CEACCP, 2004