Bupivacaine is an amino-amide local anaesthetic that plays a vital role in modern obstetric care across Nigeria. Midwives frequently encounter this drug during regional anaesthesia procedures such as spinal anaesthesia for caesarean sections, epidurals for labour pain relief, and perineal infiltration. Its popularity stems from its reliable potency and a notable tendency to provide prolonged sensory block while leaving motor function relatively spared at lower concentrations. This characteristic makes it a preferred agent when a mother needs effective pain relief without losing the ability to move her lower limbs entirely during labour.
The drug works by reversibly binding to voltage-gated sodium channels on the inner membrane of nerve fibres. When these channels are blocked, the influx of sodium ions is prevented, halting the generation and conduction of nerve impulses. Consequently, pain signals fail to reach the central nervous system.
Midwives frequently use bupivacaine to infiltrate the perineum prior to performing an episiotomy or repairing a perineal tear. Plain bupivacaine, usually in a 0.25% or 0.5% concentration, is infiltrated along the planned incision line using a fine-gauge needle.
Aspirating the syringe plunger before injecting is mandatory to ensure the needle is not inside a blood vessel. Accidental intravascular injection can lead to rapid systemic toxicity. The midwife must wait a few minutes after infiltration for the drug to take full effect before cutting or suturing tissue.
A pudendal nerve block provides targeted perineal anaesthesia for spontaneous vaginal deliveries or instrumental births involving forceps or vacuum extractors. Bupivacaine is deposited near the pudendal nerve as it crosses the ischial spine. Midwives utilizing this block must be thoroughly familiar with internal anatomical landmarks, specifically locating the ischial spine via vaginal examination. Successful infiltration blocks the S2, S3, and S4 nerve roots, numbing the lower vagina, vulva, and perineum while leaving uterine contractions unaffected.
Calculating the correct dose of bupivacaine is critical to prevent overdose and systemic toxicity. The maximum recommended dose for plain bupivacaine without epinephrine is generally 2 milligrams per kilogram of body weight. Pregnant women exhibit heightened sensitivity to local anaesthetics due to hormonal changes and engorged epidural veins, which reduce the epidural space volume. Consequently, clinicians often reduce standard doses by up to 30 percent in late pregnancy to prevent sudden, high sensory blocks or maternal cardiovascular collapse.
Local Anaesthetic Systemic Toxicity (LAST) is a life-threatening emergency caused by excessive plasma levels of bupivacaine, usually following accidental intravascular injection.
Early signs often involve the central nervous system: a metallic taste in the mouth, ringing in the ears (tinnitus), circumoral numbness, dizziness, and confusion. If left unmanaged, this progresses rapidly to muscle twitching, generalized seizures, cardiovascular collapse, and cardiac arrest.
Management requires immediate cessation of the local anaesthetic injection, calling for emergency assistance, ensuring a patent airway with 100% oxygen, and preparing a 20% lipid emulsion therapy kit alongside standard resuscitation equipment.
Following any regional block or perineal infiltration using bupivacaine, the midwife holds primary responsibility for ongoing maternal surveillance. Vital signs—including blood pressure, pulse, and respiratory rate—must be monitored at regular intervals, as sympathetic blockade can cause sudden maternal hypotension. The midwife also assesses sensory block regression, motor function recovery in the legs, and bladder distension. Postpartum urinary retention is common after extensive perineal analgesia, so palpating the maternal bladder and encouraging timely voiding form an essential part of routine postnatal nursing care.