Residency · Residency · Anesthesiology
Anesthesia for Cesarean Delivery: Spinal, Epidural, and General
Spinal Anesthesia for Cesarean Delivery
Standard Technique
Spinal anesthesia is the most common anesthetic for elective and semi-urgent cesarean delivery because it provides a rapid, reliable, dense surgical block. The patient is typically positioned sitting (preferred for landmark identification) or in the lateral position.
Drug Selection
Hyperbaric Bupivacaine
The standard dose is 10 to 12 mg of 0.75% bupivacaine in 8.25% dextrose. Higher doses of 12 to 15 mg provide longer duration but more hypotension, while lower doses of 7 to 9 mg combined with intrathecal opioids are appropriate for combined spinal-epidural techniques.
Intrathecal Opioids
Fentanyl 10 to 25 mcg improves block quality, reduces intraoperative visceral pain, and allows a lower bupivacaine dose. Morphine 0.1 to 0.2 mg provides 12 to 24 hours of postoperative analgesia and represents the gold standard for post-cesarean pain management. Its side effects include pruritus (60 to 80%), nausea (20 to 30%), and delayed respiratory depression (rare, approximately 0.1 to 0.4%). Respiratory rate should be monitored every 1 to 2 hours for 12 to 24 hours after intrathecal morphine.
Typical Recipe
A common combination is hyperbaric bupivacaine 12 mg plus fentanyl 15 mcg plus morphine 0.15 mg.
Block Height Assessment
The target is a T4 sensory level (nipple line) tested with ice or pinprick. A level below T4 risks intraoperative visceral pain during uterine manipulation and peritoneal traction, while a level above T2 risks respiratory compromise and hemodynamic instability.
<image>Illustration of spinal anesthesia setup for cesarean delivery showing the patient in sitting position with landmarks, a 25G pencil-point spinal needle at L3-L4, CSF flowing from the needle hub, and the standard drug mixture being drawn up (bupivacaine, fentanyl, morphine vials with syringes). An inset dermatome map shows the T4 target level for cesarean delivery with key landmarks (T4 = nipple, T10 = umbilicus, L1 = inguinal).</image>
Spinal-Induced Hypotension
Pathophysiology
Sympathectomy causes arterial vasodilation (decreased SVR) and venodilation (decreased preload), effects that are compounded by aortocaval compression from the gravid uterus. Without prophylaxis, the incidence reaches 60 to 80%. Spinal hypotension can cause maternal nausea and vomiting, dizziness, and decreased uteroplacental perfusion leading to fetal acidosis.
Prevention and Treatment
Vasopressor Prophylaxis (Current Standard)
A phenylephrine infusion started at 25 to 50 mcg/min immediately after spinal injection and titrated to maintain systolic blood pressure within 10 to 20% of baseline is the current standard approach. Norepinephrine infusion at 3 to 5 mcg/min is increasingly used and may better preserve cardiac output than phenylephrine. Bolus dosing with phenylephrine 50 to 100 mcg or norepinephrine 4 to 8 mcg can be given as needed.
Phenylephrine vs. Norepinephrine Debate
Phenylephrine, a pure alpha-1 agonist, is effective for SVR but may decrease cardiac output via reflex bradycardia. Norepinephrine, with both alpha-1 and beta-1 activity, maintains SVR with better cardiac output preservation. Multiple RCTs show both are effective, though norepinephrine may produce less bradycardia and better cardiac output. Either is superior to ephedrine, which causes more fetal acidosis via beta-mediated metabolic effects.
| Vasopressor | Receptor Activity | Bolus Dose | Infusion Dose | Effect on CO | Fetal Acidosis Risk |
|---|---|---|---|---|---|
| Phenylephrine | Alpha-1 | 50–100 mcg | 25–50 mcg/min | May decrease (reflex bradycardia) | Low |
| Norepinephrine | Alpha-1 + Beta-1 | 4–8 mcg | 3–5 mcg/min | Better preserved | Low |
| Ephedrine | Alpha + Beta (indirect) | 5–10 mg | Not recommended | Increased | Higher (beta-mediated) |
Fluid Management
Co-loading (rapid crystalloid infusion at the time of spinal) is more effective than pre-loading. Colloid co-loading may be superior to crystalloid but is rarely used. A standard co-load consists of 1 to 2 liters of crystalloid.
Left Uterine Displacement
Left uterine displacement through 15 to 30 degrees of left lateral tilt or manual displacement of the uterus is mandatory in all supine positioning after 20 weeks of gestation.
Epidural Anesthesia for Cesarean Delivery
Indications
The most common scenario is conversion of an existing labor epidural to surgical anesthesia. Epidural anesthesia is also appropriate for patients with significant cardiac disease in whom a slow, titratable onset is desired, and for anticipated prolonged surgery where additional dosing may be needed.
Top-Up of Existing Labor Epidural
Options include 2% lidocaine with epinephrine and bicarbonate at 15 to 20 mL in 5 mL increments, or 3% 2-chloroprocaine at 15 to 20 mL (fastest onset, 5 to 10 minutes). Fentanyl 50 to 100 mcg improves block quality, and epidural morphine 2 to 3 mg at the end of the case provides postoperative analgesia.
De Novo Surgical Epidural
A de novo epidural uses 2% lidocaine with 1:200,000 epinephrine at a total of 15 to 25 mL with incremental dosing. Onset is slower than spinal (15 to 20 minutes) but the technique is titratable. There is less hypotension than with spinal anesthesia due to the gradual sympathectomy, and the catheter allows re-dosing for prolonged procedures.
General Anesthesia for Cesarean Delivery
Indications
General anesthesia is indicated when regional anesthesia has failed or is contraindicated, for Category 1 emergencies with no existing epidural, for maternal hemorrhage with hemodynamic instability, for patient refusal of regional anesthesia, and for specific surgical situations such as placenta accreta with anticipated massive hemorrhage.
Rapid-Sequence Induction (RSI)
Pre-Induction
Steps include left uterine displacement, pre-oxygenation with 100% oxygen for 3 minutes (or 8 vital capacity breaths), aspiration prophylaxis with sodium citrate 30 mL orally, IV ranitidine/famotidine, and metoclopramide, and preparation for a difficult airway with a video laryngoscope available and supraglottic airway backup.
Induction
Propofol at 2 to 2.5 mg/kg (or thiopental 4 to 5 mg/kg if available; etomidate if hemodynamically unstable) is followed by succinylcholine at 1 to 1.5 mg/kg (rocuronium 1.2 mg/kg with sugammadex backup is an alternative). Cricoid pressure is applied, and no opioid is given before delivery to avoid neonatal respiratory depression.
Maintenance Pre-Delivery
Anesthesia is maintained with 1 to 1.5 MAC of volatile agent (sevoflurane or desflurane) in 50% oxygen/50% nitrous oxide (or 100% oxygen), with no opioids until the cord is clamped. The goal is adequate maternal anesthesia while minimizing neonatal drug exposure. Volatile agents cause dose-dependent uterine relaxation, and concentrations above 1.5 MAC increase bleeding risk.
After Cord Clamping
After cord clamping, the volatile agent is reduced to 0.5 to 0.7 MAC. An opioid (fentanyl 100 to 200 mcg) and midazolam (1 to 2 mg) are added for amnesia. An oxytocin infusion is started, and nitrous oxide may be added if not already in use to reduce volatile agent requirements.
<image>Step-by-step rapid-sequence induction protocol for obstetric general anesthesia displayed as a timeline. Steps include: pre-oxygenation with tight-fitting mask, aspiration prophylaxis, left uterine displacement, equipment check (video laryngoscope ready), induction (propofol and succinylcholine doses), cricoid pressure application, intubation confirmation with capnography, maintenance with volatile agent and O2/N2O, cord clamp notification, dose adjustments post-delivery (reduce volatile, add opioid), and emergence plan. Key timing annotations show the induction-to-delivery interval target of less than 10 minutes.</image>
Awareness Risk
Obstetric GA carries the highest incidence of awareness among all surgical populations because light anesthesia is maintained to protect the fetus (low volatile agent, no opioid pre-delivery). The volatile agent should not be reduced below 0.7 MAC pre-delivery, as this does not meaningfully improve neonatal outcomes while substantially increasing awareness risk. Processed EEG monitoring (BIS) is recommended by some experts. Awareness under obstetric GA can cause significant PTSD.
Neonatal Considerations
Drug Transfer
All IV and inhalational agents cross the placenta. The uterine incision-to-delivery (U-D) interval should be kept under 3 minutes, and the induction-to-delivery (I-D) interval beyond 10 minutes may increase neonatal drug exposure. Short intervals are associated with better neonatal outcomes, and a neonatal resuscitation team should be present for all GA cesarean deliveries.
Apgar Scores
Regional anesthesia is generally associated with higher 1-minute Apgar scores than GA, though 5-minute Apgar scores are usually equivalent. Neonates delivered under GA may require more stimulation and resuscitation initially.
Perimortem Cesarean Delivery
Indications
Perimortem cesarean delivery is indicated in maternal cardiac arrest at 23 weeks of gestation or greater (or when the fundal height is at or above the umbilicus). CPR should be initiated immediately, with cesarean delivery called for within 1 minute. The goal is delivery within 4 to 5 minutes of cardiac arrest onset.
Rationale
This procedure relieves aortocaval compression, improving venous return and CPR effectiveness. It may be life-saving for both mother and fetus and should be performed at the site of arrest -- the patient should not be transported to the operating room.
Key Points
No anesthesia is required because the mother is in cardiac arrest. Skin preparation and surgical draping should not delay the procedure. CPR continues throughout the cesarean delivery. After delivery, uterotonics are administered, surgical hemostasis is achieved, and maternal resuscitation continues.
Clinical Pearls
Phenylephrine or norepinephrine infusion started immediately after spinal injection is the current standard for preventing spinal hypotension; ephedrine is second-line due to fetal acidosis. Intrathecal morphine 0.1-0.2 mg is the gold standard for post-cesarean analgesia, providing 12-24 hours of pain relief; ensure appropriate respiratory monitoring. For emergency epidural top-up, 3% chloroprocaine is the fastest option; always have it stocked on labor and delivery. During GA for cesarean delivery, do NOT reduce volatile agent below 0.7 MAC pre-delivery; awareness risk is already elevated and reducing anesthetic depth further does not meaningfully improve neonatal outcomes. Perimortem cesarean delivery should be initiated within 1 minute of maternal cardiac arrest and completed by 5 minutes; it is a resuscitative intervention for the mother as much as for the fetus. If succinylcholine is contraindicated, rocuronium 1.2 mg/kg with sugammadex available for reversal is the standard RSI alternative in obstetrics.
References
- Ngan Kee WD, Lee SWY, Ng FF, et al. Randomized double-blinded comparison of norepinephrine and phenylephrine for maintenance of blood pressure during spinal anesthesia for cesarean delivery. Anesthesiology. 2015;122(4):736-745.
- Kinsella SM, Carvalho B, Dyer RA, et al. International consensus statement on the management of hypotension with vasopressors during caesarean section under spinal anaesthesia. Anaesthesia. 2018;73(1):71-92.
- Balki M, Bhide A. Anesthesia for cesarean delivery. In: Chesnut DH, ed. Chestnut's Obstetric Anesthesia. 6th ed. Elsevier; 2020.
- Lipman SS, Daniels KI, Carvalho B, et al. Defining best practice in maternal cardiac arrest: a consensus statement. Anesthesia & Analgesia. 2014;118(5):1003-1016.
- Pandit JJ, Andrade J, Bogod DG, et al. 5th National Audit Project (NAP5) on accidental awareness during general anaesthesia. British Journal of Anaesthesia. 2014;113(4):549-559.
