What are the guidelines for using inhalational anesthesia in a pregnant patient?

Inhalational Anesthesia in Pregnancy

Primary Recommendation

Neuraxial (spinal or epidural) anesthesia should be strongly preferred over general anesthesia with inhalational agents for pregnant patients undergoing cesarean delivery or other surgical procedures, as general anesthesia carries significantly higher risks of pulmonary aspiration, difficult intubation, and inferior postoperative analgesia. 1, 2

When General Anesthesia with Inhalational Agents is Required

Indications for General Anesthesia

General anesthesia may be necessary in specific circumstances:

• Extreme emergency requiring immediate fetal extraction 1
• Severe maternal SARS-CoV-2 infection with hemostasis abnormalities contraindicating neuraxial techniques 1
• Major respiratory distress contraindicating neuraxial anesthesia 1
• Predicted difficult airway where awake intubation is preferred 3, 2

Safety Profile of Inhalational Agents

The American College of Obstetricians and Gynecologists explicitly states there is no human evidence for adverse effects of anesthetics or sedatives on the developing fetal brain and no evidence of teratogenic effects at any gestational age. 2

• Modern volatile anesthetics (sevoflurane, isoflurane) have not demonstrated teratogenic effects in humans when used at standard doses 4
• Animal studies suggest potential neurotoxic effects via GABA and NMDA pathways, but no human data have corroborated these findings 2, 5, 6
• A case series of 11 children with antenatal exposure to general anesthesia showed no developmental or physical abnormalities at 1-8 year follow-up 2

Critical Maternal Safety Concerns

General anesthesia in pregnant women is associated with higher risks of pulmonary aspiration and difficult intubation compared with the general population, making airway management the primary safety concern. 1, 2

• Pregnancy causes airway edema, friability, hypersecretion, and smaller upper airway diameter 2
• Failed intubation is a major cause of maternal morbidity and mortality in obstetric anesthesia 2
• Rapid desaturation occurs during apnea due to decreased functional residual capacity and increased oxygen consumption 2

Preoperative Planning and Assessment

Airway Evaluation

• Document Mallampati grade, neck movement, mouth opening, thyromental distance, and jaw protrusion to predict potential difficulties 3, 4
• Women with anticipated airway difficulties should be identified during antenatal care and referred for specific anesthetic and obstetric management planning 3
• If significant airway difficulties are predicted, awake tracheal intubation should be considered rather than rapid sequence induction 3, 2

Aspiration Prophylaxis

• Administer H2-receptor antagonist intravenously if not already given 3, 4
• Give sodium citrate 30 mL immediately before induction 3, 4
• Women at high risk for preterm delivery should follow restrictive oral intake guidelines - clear fluids only, no solid food 3
• H2-receptor antagonists should be administered every 6 hours during labor for women at high risk of requiring general anesthesia 3

Intraoperative Management

Anesthetic Technique

• Rapid sequence induction remains the standard technique when general anesthesia is required for cesarean delivery 3
• Use "ramped" positioning to optimize laryngoscopic view in pregnant patients 3
• Have difficult airway equipment immediately available, including video laryngoscopes and supraglottic airway devices 3
• Front-of-neck access equipment should be prepared in case of "can't intubate, can't oxygenate" scenario 3

Agent Selection

• Sevoflurane is preferred due to its non-irritant properties and rapid emergence characteristics 4
• Although inhaled anesthetics transfer to the fetus, they do not reliably diminish fetal autonomic stress responses 2
• High doses can cause fetal cardiovascular depression and adverse hemodynamic effects 2
• Limit surgical duration to 90-120 minutes when possible to reduce anesthetic exposure 2

Monitoring and Positioning

• Maintain end-tidal CO2 between 30-35 mmHg to avoid maternal hypocapnia or hypercapnia, which can compromise uteroplacental blood flow 4
• Use left lateral tilt (or right lateral tilt if it improves surgical exposure) after 20 weeks gestation to prevent aortocaval compression 2, 4
• Maternal hypotension can cause reduced placental blood flow and fetal hypoxia before maternal deterioration becomes apparent 2
• Continuous monitoring should include ECG, non-invasive blood pressure, pulse oximetry, capnography, and temperature 4

Extubation

• Extubation should be performed in the operating theatre with a limited number of people present 1
• Only extubate when the patient is fully awake, responsive to commands, maintaining oxygen saturation, and generating adequate tidal volumes 4
• Maintain high vigilance for regurgitation and aspiration during emergence 4

Specific Considerations for Labor Analgesia

Inhaled Nitrous Oxide

The use of inhaled nitrous oxide should be avoided in labor analgesia, particularly during the COVID-19 pandemic, because of the potential aerosolization risk and limited analgesic efficacy. 1

• Flurane derivatives offer better pain relief than nitrous oxide in first stage of labor (lower pain intensity scores and higher pain relief scores) 7
• Nitrous oxide results in more side effects including nausea, vomiting, dizziness, and drowsiness compared with placebo or no treatment 7

Common Pitfalls to Avoid

• Never underestimate airway difficulty in pregnant patients - pregnancy-related physiological changes significantly increase intubation difficulty 2
• Avoid supine positioning after 20 weeks of gestation to prevent aortocaval compression 2
• Do not delay anesthesia consultation until an emergency arises - early planning and multidisciplinary collaboration are essential 3, 2, 4
• Failure to recognize the need for specialized equipment and personnel for difficult airway management can lead to adverse outcomes 3
• Maternal hypoxia and hypotension from oversedation can decrease placental blood flow and cause fetal hypoxia, distress, and possible demise 2

Postoperative Analgesia

• Post-cesarean section analgesia is of better quality after neuraxial anesthesia than after general anesthesia 1
• For women with SARS-CoV-2 infection, avoid postoperative use of NSAIDs 1
• Extended thromboprophylaxis indications should be considered for pregnant and postpartum women, including after vaginal delivery 1