Comparison of 'Sip Til Send' Regimens Prior to Elective Caesarean Delivery Using Bedside Gastric Ultrasound

This study is a prospective randomized single-blinded study. Randomisation to intervention which will be "water" group and "carbohydrate" group. Pregnant women cannot be blinded to the intervention, but the healthcare workers and the investigators will be blinded to the intervention.

This study will incorporate clinical practice protocols that are already in place at the Rotunda hospital. The enhanced recovery guidelines encourage consumption of carbohydrate drinks prior to arrival at hospital for surgery. This protocol was superseded by the introduction of 'Sip Til Send' with water with an aim to reduce fasting times after arrival at hospital, but adherence with both practices is variable.

The study intervention is the provision of water or a standard carbohydrate-rich drink which the participants may sip to comfort at a maximum rate of 1 cup (170ml) per hour whilst waiting in hospital for an elective CD planned under neuraxial anaesthesia. The water group represent the control or standard practice group as this is in line with current hospital policy. The carbohydrate group represent the interventional group and will utilise the same carbohydrate drinks available for enhanced recovery.

Eligible participants booked to undergo an elective CD will be recruited on the day of surgery by a member of the research team. Consideration will depend on the research team availability, expected fasting time of more than 1 hour and full adherence of European fasting guidelines at the time of study entry (6 hours for solids and 2 hours for liquids). Following recruitment, written consent is obtained and a 'fasting' gastric ultrasound will be performed in a standardised manner prior to randomisation. If a Perlas grade 2 antrum is encountered, this will be assumed to represent a full stomach (>1.5ml/kg) and the potential participant be removed from the study. To mitigate any further risk, they will be advised to fully fast, not be offered 'Sip Til Send' and the anaesthesiologist in charge of their clinical care will be informed. Any women in whom adequate views of the gastric antrum cannot be obtained in both positions will also be removed from the study. All other participants will then be randomized into the study.

Following group allocation, women will be provided with a weighed jug of water or carbohydrate drink, a 170ml cup and written instructions stating that they may drink continually to comfort up to 1 cup and hour and information on how to refill if required. Prior to their CD, any remaining drink will be weighed to calculate to volume consumed (assuming a liquid density of 1mg/ml) and participants will undergo a second gastric ultrasound scan immediately prior to surgery.

Normal clinical care will resume after this point with group allocation having no impact on care received. During surgery, a urine sample will be collected via the catheter bag following written consent and will be sent to the hospital laboratory to test for ketones. This result will also be available to the treating clinicians.

At around 24 hours after delivery (+/- 4 hours), women will be approached for a single follow-up visit where they will be asked to complete an obstetric-specific quality of recovery score (ObsQoR-10). Following discharge from hospital, medical notes will be interrogated for evidence of perioperative nausea, vomiting or aspiration and neonatal notes will also be interrogated for evidence of treated hypoglycaemia.

Gastric ultrasound is a safe non-invasive scan which will take about 10 minutes to complete. It involves placement of a curvilinear ultrasound probe on the upper abdomen whilst the participant is on their back and then their right-hand side. The head of the bed will be elevated to 45 degrees during the scan for comfort and to prevent aortocaval compression. A qualitative Perlas score is given based on whether clear liquid is seen in the antrum in each position. A Perlas 0 antrum has no fluid in either position, a Perlas 1 has clear fluid in the right-lateral position but not when semi-recumbent and a Perlas 2 score has identifiable clear fluid in both positions. Gastric antrum CSA will be calculated using horizontal and vertical calliper measurements inputted into a formula to calculate the area of an ellipse. These will also be used to estimate gastric volumes via the method below that has been validated in term pregnant women previously:

GV (mL) = 0.18 x right-lateral CSA (mm2) + 0.11 x semirecumbent CSA (mm2) - 62.4

Inclusion criteria

• Planned caesarean delivery under regional anaesthesia
• Adhered to national fasting guidance of 6 hours for food and 2 hours for clear fluids
• Eligible for Sip Til Send

Exclusion criteria

• Planned general anaesthesia
• Emergency or urgent caesarean delivery
• Not fasted at time of recruitment
• Unable to visualise stomach or Perlas 2 stomach identified at time of recruitment
• Obesity of BMI >40
• Previous upper GI or bariatric surgery
• Age <18 years
• Insulin dependent diabetes mellitus (type 1 or 2)
• Gestational diabetes