A 35-year-old woman with a history of gastroesophageal reflux disease (GERD) is scheduled for emergency cesarean section under spinal anesthesia. She consumed a light meal 3 hours ago. Which investigation is most appropriate to assess her aspiration risk and guide the decision on fasting adequacy before anesthesia?

## Investigation for Aspiration Risk Assessment **Key Point:** Abdominal ultrasound measurement of gastric antral diameter is the gold-standard non-invasive investigation to assess gastric volume and aspiration risk in the perioperative period. ### Gastric Ultrasound in Preoperative Fasting Assessment **High-Yield:** Point-of-care ultrasound (POCUS) of the gastric antrum has become the standard investigation for real-time assessment of gastric contents and volume in emergency surgery, particularly when fasting status is uncertain. #### Ultrasound Criteria for Aspiration Risk | Antral Diameter | Risk Category | Interpretation | |---|---|---| | <1.5 cm (fasting) | Low | Empty stomach, safe for anesthesia | | 1.5–2.5 cm | Intermediate | Borderline; consider delay or RSI | | >2.5 cm | High | Full stomach; high aspiration risk | | Fluid visible in antrum | High | Definite gastric content; RSI mandatory | ### Why Gastric Ultrasound? 1. **Non-invasive & Real-time** - No radiation exposure (safe in pregnancy) - Immediate assessment at bedside - Can be repeated if needed 2. **Accurate Volume Estimation** - Correlates with gastric volume measured at endoscopy - Sensitivity ~90% for detecting gastric content - Guides RSI (rapid sequence intubation) decision 3. **Specific to GERD Patients** - GERD increases aspiration risk even after standard fasting - Ultrasound detects retained gastric fluid despite fasting - Helps decide between spinal vs. general anesthesia **Clinical Pearl:** In emergency cesarean section with uncertain fasting, gastric ultrasound can safely defer surgery if stomach is empty (antral diameter <1.5 cm), avoiding unnecessary RSI and its maternal/fetal risks. ### Fasting Guidelines for Emergency Surgery - **Standard fasting:** 6 hours (solids), 2 hours (clear fluids) - **Light meal (this case):** 3 hours consumed → borderline; ultrasound assessment recommended - **GERD patients:** Higher baseline aspiration risk; ultrasound particularly valuable **Mnemonic for Aspiration Risk Factors:** **GERD FAST** - **G**astroesophageal reflux - **E**mergency surgery - **R**ecent food intake - **D**iabetes (delayed gastric emptying) - **F**atty/full meal - **A**cute abdomen - **S**mall stature - **T**raumа / obesity ### Why Not the Others? - **Upper GI endoscopy:** Invasive, time-consuming, not suitable for emergency assessment; carries aspiration risk itself. - **Serum gastrin + pH:** Gastrin levels reflect acid secretion state (not volume); pH measurement is not standardized for preoperative use. - **Nasogastric pH monitoring:** Invasive, uncomfortable, does not quantify volume; not standard practice for preoperative assessment.