Analgesia in Labour

Introduction

The pain threshold may be low during labour on account of fear, anxiety and uncertainty.
Adequate pain relief during labour results in less anxiety and good progress.
In the first stage of labour pain relief may be required for painful uterine contractions, whereas in the second stage of labour, analgesia is required for instrumental delivery and when an episiotomy is given.

Pharmacological treatment

A. During the first stage of labour – parenteral

Evidence Rating: [C]
Morphine, IV,

  • 2.5-5 mg 4 hourly as required

And

Metoclopramide, IV,

  • 5-10 mg 8 hourly as required for vomiting

Or

Pethidine hydrochloride, IM,

  • 50-100 mg stat. repeated as required 3-4 hours later (Maximum 400 mg in 24 hours)

And

Promethazine, IV/IM,

  • 25 mg as required (Maximum 25 mg 6 hourly) as required to reduce the chances of vomiting and to potentiate the analgesic effect of Pethidine

Points to Note

Given IM, the maximum analgesic effect of Pethidine is obtained after 45 minutes and lasts for 3-4 hours.
It is therefore best not to give it when delivery is anticipated within 4 hours i.e. up to 6-7 cm dilatation.
If the baby born within 6 hours of Pethidine administration it may have respiratory depression requiring narcotic antagonists such as Naloxone IM, 100 microgram/kg stat.
(If no response, give subsequent dose of 100 micro gram after 3-8 minutes).
Continue resuscitation with oxygen via a facemask or through an endotracheal tube and self inflating (Ambu) bag until the de pression is reversed.
However, Pethidine should not be withheld from patients who need anal gesia when the cervix is already 6-7 cm dilated in which case 50-75 mg IM Pethidine with 12.5-25 mg.
Promethazine may be given intravenously.

B. During the first stage of labour – inhalational

Nitrous oxide and Oxygen mixture, 50:50
Note

  • To be used in the late first stage when delivery is expected within 1 hour.

C. During the first stage of labour- epidural

Note

This procedure is best carried out by an anaesthetist.

D. During the second stage of labour

  • Local Anaesthetics for episiotomy and pudendal block anaesthesia to facilitate instrumental delivery.
  • Lidocaine hydrochloride (Xylocaine/Lignocaine) 1%, with or without adrenaline, infiltrated in the perineum before an episiotomy. If not given before delivery it can be given before the repair of the episiotomy.

E. Anaesthesia for short obstetric procedures e.g. manual removal of placenta, repair of large vaginal and cervical tears
Pethidine, IM or IV,

  • 1 mg/kg slowly (max. 100 mg) if no anaesthetist is available

Promethazine hydrochloride, IM,

  • 25 mg stat. (if vomiting occurs)

Or

Metoclopramide, IV,

  • 5-10 mg 8 hourly as required

And

And Diazepam, slow IV,

  • 5-10 mg (at a rate of 2.5 mg per minute)

Note

Monitor respiratory rate closely. Stop Diazepam if respiratory rate is less than 10/minute).
Do not mix the two drugs in the same syringe.

2nd Line Treatment
Ketamine, IM,

  • 5-10 mg/kg stat.

Or

Ketamine, IV slowly,

  • 1-2 mg/kg

Or

Ketamine, IV infusion,
(For longer procedures)

  • 1 mg per ml of ketamine in dextrose 5% or normal saline (maintenance dose 10-45 microgram per kg per minute adjusted according to response.

And

Diazepam, slow IV,

  • 5-10 mg, administered over 2-3 minutes (approximately 2.5 mg per minute) to prevent Hallucinations

F. Premedication before Ketamine administration

Atropine, IM,

  • 600 microgram stat.

And

Oxygen, by face mask,

  • 6-8 L/minute

Note

Ketamine is contraindicated in patients with high blood pressure (Hypertension) and heart disease.