Chapter 41 Pain relief in labour
About two-thirds of women in labour consider the pain very severe and intolerable. There is a need for antenatal preparation, with balanced information and opportunity to discuss options of analgesia.
Analgesia in labour
Non-pharmacological methods
Pharmacological methods
• Systemic opioid analgesia: pethidine has a more rapid onset (20–30 minutes, with peak effects at 1 hour) of action than morphine because of its higher lipid solubility. Neonatal depression can occur when administered 2–3 hours before delivery. Side effects include nausea, vomiting and reduced gastric motility.
• Regional anaesthesia: lumbar epidural is the most effective and reliable form of pain relief in labour. The local anaesthetic may be delivered by intermittent boluses or constant infusion.
Advantages of lumbar epidural
• There is minimal or no fetal/neonatal depression with higher Apgar scores than those associated with narcotic analgesia.
Disadvantages of lumbar epidural
• There may be hypotension from reduced peripheral vascular resistance. This is a result of sympathetic blockade with decreased vasoconstriction and increased venous pooling. The blockade also produces a secondary tachycardia. Hypotension is managed with intravenous fluids and ephedrine 5–10 mg intravenously.
Complications of lumbar epidural
• Local anaesthesia toxicity. Central nervous system effects of circumoral numbness, restlessness, visual changes, confusion and convulsion, and arrhythmia and hypotension, are managed by ensuring adequate airway/ventilation, assessing cardiorespiratory status and treating convulsions.
• Massive subarachnoid injection of local anaesthetic. This is avoided by applying a small test dose. The complications, including hypotension, nausea, coma, fixed dilated pupils, phrenic nerve paralysis and ventilatory failure, are managed by providing ventilatory support, assessing cardiovascular status and giving intravenous fluids (maintain these until the anaesthetic wears off).
