Obstetric anaesthesia and caesarean section
- Patient and surgery
Anaesthesia for a pregnant woman, usually for caesarean birth, where two patients are cared for and most mothers stay awake with a spinal.
What it is
Pregnancy changes almost every system the anaesthetist relies on. Oxygen consumption rises while the functional residual capacity falls, so a pregnant woman desaturates fast when she stops breathing; airway tissues swell, the breasts are larger and the airway is more often difficult. Progesterone relaxes the lower oesophageal sphincter and the uterus displaces the stomach, so aspiration risk is higher, particularly in labour. From mid-pregnancy the uterus compresses the vena cava and aorta when she lies flat, reducing venous return and placental flow, so the uterus is displaced to the left. Blood volume and cardiac output rise, there is a relative dilutional anaemia and the blood is hypercoagulable; less local anaesthetic and less volatile agent are needed. For caesarean section, neuraxial anaesthesia (a single-shot spinal, a combined spinal-epidural or a top-up of a working labour epidural) is preferred because it avoids airway risk, lets the mother be awake for the birth and limits drug transfer to the baby. General anaesthesia is kept for when neuraxial is contraindicated, has failed or there is no time, and then a rapid-sequence induction is used. Urgency is graded from an immediate threat to the life of the mother or baby to an elective procedure, and the plan follows that grade. Women with serious heart disease need a team plan, careful titration of any block and close monitoring through delivery and the days after, when fluid shifts back into the circulation.
What changes in this patient
- Breathing: higher minute ventilation (mild respiratory alkalosis), lower functional residual capacity, faster desaturation.
- Airway: mucosal oedema and bleeding, weight gain and larger breasts; failed intubation is more common than in non-pregnant patients.
- Stomach: lower sphincter tone, raised intra-abdominal pressure and, in labour, slower emptying increase aspiration risk.
- Circulation: more blood volume and cardiac output, lower systemic resistance, aortocaval compression when supine.
- Blood: dilutional anaemia and a hypercoagulable state; venous thromboembolism risk is higher after delivery.
- Drugs: lower requirement for local anaesthetic and volatile agents; most drugs cross the placenta to some degree.
Anaesthetic plan (and why)
- Grade the urgency with the obstetric team — an immediate threat may need general anaesthesia; other grades allow neuraxial.
- Assess airway, bleeding risk, platelets in preeclampsia and anticoagulant timing — decides whether neuraxial is safe.
- Give antacid prophylaxis and keep the uterus displaced to the left — reduces aspiration harm and protects venous return.
- Prefer spinal or a top-up of the labour epidural, testing the block height before incision — avoids airway risk, mother awake.
- Treat hypotension early with a vasopressor and fluid co-loading — maternal pressure drives placental flow.
- If general anaesthesia: preoxygenate, rapid-sequence induction, videolaryngoscope, smaller tube, failed-airway plan ready.
- After delivery give uterotonics slowly and watch for bleeding — oxytocin given fast causes hypotension and tachycardia.
- In high-risk heart disease, titrate blocks slowly with invasive monitoring — avoids sudden falls in preload and afterload.
Urgency grades of caesarean section and the usual anaesthetic choice
| Grade | Meaning | Usual anaesthetic |
|---|---|---|
| 1 | Immediate threat to the life of mother or baby | Top-up of a working epidural or rapid spinal if very quick; otherwise general anaesthesia |
| 2 | Maternal or fetal compromise, not immediately life-threatening | Neuraxial in most cases |
| 3 | No compromise but early delivery needed | Neuraxial |
| 4 | Planned at a time to suit mother and team | Neuraxial |
Risks and complications
- Hypotension after spinal anaesthesia, with nausea and fetal heart rate changes.
- High or total spinal block, especially after a top-up of an epidural that has migrated into the subarachnoid space.
- Failed intubation and aspiration during general anaesthesia; awareness is also more frequent.
- Postpartum haemorrhage from uterine atony, placenta praevia or accreta; carboprost can cause bronchospasm and methylergometrine hypertension.
- Preeclampsia: low platelets, airway oedema, a hypertensive surge at intubation and magnesium potentiating relaxants.
- Rare but feared: amniotic fluid embolism, local anaesthetic toxicity and peripartum heart failure.
Next step
- Monitor the mother in recovery for bleeding, uterine tone, blood pressure, block regression and pain; obstetric early warning scores help.
- Give multimodal analgesia; neuraxial opioid needs respiratory monitoring for the following hours.
- Time thromboprophylaxis around neuraxial puncture and catheter removal according to the local interval rules.
- Call a senior anaesthetist for failed or high block, difficult airway, major haemorrhage, preeclampsia with complications or heart disease.
- Follow up for post-dural puncture headache or any new numbness or weakness, and explain the anaesthetic; breastfeeding can usually continue.
Test yourself
Think of the answer, then tap the question to see it.
Why do pregnant women desaturate faster than non-pregnant patients during apnoea?
Oxygen consumption is higher and functional residual capacity is lower, so the oxygen store in the lungs is smaller and used up faster.
Why is the uterus displaced to the left during caesarean section?
From mid-pregnancy the uterus compresses the vena cava and aorta when supine, reducing venous return, cardiac output and placental blood flow.
Why is neuraxial anaesthesia preferred for caesarean section?
It avoids the risks of difficult intubation and aspiration, lets the mother be awake for the birth and limits drug transfer to the baby.
Why are block onset and fluid shifts critical in a mother with severe stenotic heart disease?
Fixed-output lesions tolerate sudden falls in preload and afterload poorly, and the return of blood after delivery can cause pulmonary oedema; blocks are titrated slowly.
Elsewhere in DurgiPedia
- The placenta and pregnancy hormones
- Gynecologic and obstetric history
- Labour and postpartum nursing: monitoring and warning signs
Connections
Educational content; it does not replace supervised training, your institution's protocols or the anaesthetist's or intensivist's decision. It contains no doses and no ventilator or infusion settings.
Sources: Cesarean Delivery (StatPearls (NCBI Bookshelf), 2024); Anesthesia for Labor, Delivery, and Cesarean Section in High-Risk Heart Disease (StatPearls (NCBI Bookshelf), 2026).
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Representative model, for educational purposes only.