Lignocaine, also widely known as lidocaine, is an amino-amide local anaesthetic that plays a vital role in routine and emergency obstetric care across Nigeria. Midwives frequently rely on it to eliminate pain during minor surgical procedures such as perineal infiltration, episiotomy repairs, and managing perineal tears. Its reliability, rapid onset, and generally safe profile when used correctly make it a standard medication in maternity units from primary health centres to tertiary hospitals.
Beyond simple surface or local infiltration, lignocaine is valued for its versatility. It can be administered via different routes depending on the clinical need, including topical sprays, subcutaneous infiltration, and regional nerve blocks like the pudendal block. Understanding its properties allows midwives to provide humane, pain-free care during childbirth, easing the physical and emotional trauma often associated with perineal trauma and repair.
Lignocaine exerts its local anaesthetic effect by blocking sodium channels in the neuronal cell membrane. Normally, the influx of sodium ions generates the action potential that transmits pain signals along nerve fibres. By binding to these voltage-gated sodium channels, lignocaine prevents nerve depolarisation, stopping pain impulses from reaching the brain.
Adding adrenaline (epinephrine) to lignocaine causes localized vasoconstriction. This slows down the systemic absorption of the anaesthetic, prolongs the duration of the nerve block, and reduces peak blood concentration levels.
While lignocaine is remarkably safe, exceeding recommended dosage thresholds can lead to systemic toxicity. Midwives must calculate doses carefully based on the patient's weight, especially when using solutions with or without adrenaline.
Accidental intravascular injection is a major hazard in obstetric practice. If injected directly into a blood vessel, even a normal dose can cause rapid, high blood levels leading to central nervous system and cardiovascular toxicity. Always aspirate the syringe plunger before injecting any local anaesthetic to confirm the needle is not inside a blood vessel.
Infiltration of the perineum is a daily skill for midwives performing episiotomy repairs or suturing second-degree tears. Before starting, explain the procedure to the mother and check for any known drug allergies.
Insert the needle through the vaginal mucosa or the fourchette, and inject a small skin wheal. As you advance the needle along the proposed line of the tear or episiotomy, aspirate gently, then inject the solution slowly as you withdraw the needle. This fanning technique ensures the tissue layers are thoroughly anaesthetised with minimal discomfort to the mother. Wait two to three minutes after infiltration before testing sensation with a gentle touch or pinch to confirm the local anaesthetic has taken full effect.
A pudendal nerve block provides excellent perineal anaesthesia for outlet forceps delivery, vacuum extraction, or repair of complex perineal lacerations. The pudendal nerve originates from the sacral plexus (S2-S4) and travels close to the ischial spine.
To perform the block, the midwife guards the needle point using a special guide (such as a Iowa trumpet) inserted into the vagina. The needle is directed toward the ischial spine, where the pudendal nerve crosses beneath the interspinous ligament. After careful aspiration, about 5 to 10 mL of 1% lignocaine is injected on each side. This blocks sensation to the lower vagina, vulva, and perineum while leaving uterine contractions and the mother's ability to push largely unaffected.
Local Anaesthetic Systemic Toxicity is a rare but life-threatening emergency caused by excessive blood concentrations of lignocaine, usually due to accidental intravascular injection or massive overdose. Symptoms progress sequentially from mild neurological signs to severe cardiovascular collapse.
Immediate management requires stopping the injection at once, calling for emergency help, and ensuring a patent airway with 100% oxygen ventilation. If seizures occur, administer a short-acting benzodiazepine. For severe cardiovascular collapse, initiate advanced cardiac life support and prepare for the prompt administration of 20% lipid emulsion therapy as the specific antidote.