Review Note
Last Update: 03/02/2025 10:02 AM
Current Deck: ACG Part 2::Obstetrics
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Commit #292864
SS_OB 1.17 Describe the role of aspiration prophylaxis in pregnant women undergoing surgery
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Commit #292864Physiological changes of pregnancy place the mother at increased risk of aspiration due to:
- Decreased gastric motility
- Reduced effectiveness of lower oesophageal sphincter
- Increased intra-abdominal pressure
Rapid sequence induction with aspiration prophylaxis should be considered in any trimester if the patient is experiencing nausea, vomiting, pain, infection, and gastro-oesophageal reflux; has a history of hiatus hernia; or has a full stomach
The risk of aspiration is low when gastric emptying is normal and patients are appropriately fasted, however factors predisposing to aspiration (particularly obstetrics) include emergency surgery, difficult/failed intubation, light anaesthesia and GORD.
Failed intubation is much higher in obstetrics (1 in 250) due to airway oedema, breast enlargement, obesity, and high rate of emergency surgery, after hours with junior staff.
In 30-43% of obstetric patients the fasting gastric volume is >25mL and pH <2.5,
To minimize risk of aspiration obstetric patients should:
- Adhere to fasting guidelines when elective / not emergency (6 hours for food, 2 hours clear fluids)
- H2 receptor antagonists e.g. ranitidine 150mg Q6hrly pre-op – efficacious in reducing gastric acidity and volume by blocking H2 receptors on oxyntic cells and thus reduce acid production, if given orally will result in gastric pH >2.5 within 1 hour and for duration of 8 hours. Note that cimetidine reduces the rate of clearance of certain drugs (lignocaine) by binding CytP450
- Sodium citrate – 30mls of 0.3M solution – 30mls will neutralize 255mL of HCl with a pH of 1.0 but has a very limited duration of action (will keep pH >3.0 for ~30 minutes)
- Metoclopramide 10mg IV pre-operatively, will assist by increasing gastric emptying
- Don’t use particulate antacids as because if they are aspirated they cause pulmonary shunting & hypoxemia to a similar degree as acid aspiration
As per Auckland guideline updated 2023
For Pregnant patients in Labour
Omeprazole 20mg PO should be given to patients high risk of operative intervention
If proceeding for operative delivery/trial of forceps/ERPOC/perineal tear repairs/EUA
- No omeprazole in last 24hrs, consider 40mg IV (onset 1 hour) if adequate time
- If GA, sodium citrate 30ml on arrival to OT
Sodium citrate - onset immediate, short duration as per gastric emptying
IV omeprazole - 45-60mins onset
Gold coast part 2 notes