Gastric Ultrasound in Diabetic and Non-Diabetic Pregnant Women

Overview

Perioperative aspiration is particularly concerning in pregnant women due to anatomical changes. To mitigate this risk, pre-anesthetic fasting is recommended, with varying guidelines. Gastric ultrasound can non-invasively assess stomach contents, and mathematical models help estimate stomach volumes using the gastric antral cross-sectional area (CSA). This study aims to compare CSA and estimated gastric volumes through ultrasound in fasting diabetic and non-diabetic pregnant women scheduled for cesarean section, as diabetes may affect stomach fullness. Additionally, it will investigate the relation between demographic and clinical variables and CSA values. This research can shed light on diabetes' influence on aspiration risk in pregnancy and evaluate fasting guidelines, underscoring the significance of gastric ultrasound.

Perioperative aspiration of stomach contents is rare but is a serious complication of anesthesia and is associated with high morbidity and mortality. In pregnant women, it is known that the risk of aspiration is high even after standard preoperative fasting, due to anatomical changes such as the displacement of the stomach by pressure from the uterus, the sliding of the lower segment of the esophagus into the thorax, the relaxation of the lower esophageal sphincter, and the smooth muscle relaxation induced by progesterone. In cases where regional anesthesia is contraindicated, various measures, including prokinetic and antacid medications, rapid-sequence anesthetic induction, and tracheal intubation, are used to reduce the risk and severity of pulmonary aspiration. However, the most commonly used measure is pre-anesthetic fasting in the patient. The European Society of Anaesthesiology (ESA) recommends fasting for ≥2 hours after clear liquids and 6 hours after light meals before elective surgery, including in pregnant patients. The American Society of Anesthesiologists (ASA), on the other hand, recommends longer fasting times in pregnant patients without specifying the duration. Aspiration risk in pregnant women is multifactorial. The type and volume of stomach contents, which are the main risk factors for aspiration, can be easily evaluated preoperatively with gastric ultrasonography. The presence of solids or thick liquids indicates a high risk of aspiration, independent of stomach volume. However, in the presence of clear liquid, the risk of aspiration is generally linked to the volume of liquid in the stomach. The clear stomach volume limits that increase the risk of aspiration are controversial. Some studies have shown that fasted patients generally have a gastric residual volume of up to 1.5 mL kg-1, and this value is used to determine the stomach at high risk for aspiration. Gastric ultrasound assessment is an easy method that can be applied non-invasively at the bedside for evaluating gastric contents before anesthesia induction in the obstetric population. By measuring the gastric antral cross-sectional area (CSA), it may be possible to identify patients at risk for pulmonary aspiration with an estimate of stomach volume. Studies have shown the presence of a good linear correlation between antral CSA and stomach volume, not only in non-pregnant individuals but also in pregnant individuals. Additionally, antral CSA measurement can indirectly differentiate small gastric volumes, consistent with initial gastric secretions, ≤1.5 mL kg-1, from larger volumes that may be associated with increased pulmonary aspiration risk. Perlas et al. have developed a simple mathematical model based on the patient's age and antral CSA value measured in the right lateral position to calculate the volume of stomach fluid in non-pregnant adults and children. Recently, two different mathematical models have been defined by Arzola et al.and Roukhomovsky et al. to estimate stomach volumes in pregnant patients. In this study, the investigators will use the mathematical formula developed by Roukhomovsky et al., as this model evaluates the presence of any stomach content, liquid or solid, rather than the volume of fluid swallowed as standard, with MR. Additionally, the model of Perlas et al., which is widely used in clinical practice and has been verified by studies, will be used. It is accepted that there is gastroparesis in 9.9% - 76% of diabetic patients. Garg et al. in their prospective case-control study including 103 non-pregnant patients found that diabetic patients had higher gastric antral CSA and gastric volumes than non-diabetic patients. Sharma et al. have also shown that fasting for more than 6-10 hours does not guarantee an empty stomach and patients with comorbid diseases such as diabetes mellitus (DM), obesity are prone to having risky stomach contents. In DM patients, a significant increase in CSA in both supine and right lateral decubitus positions was detected compared to non-DM patients. Additionally, in the same study, it was found that as BMI increased from 25 to 35, there was a steady increase in CSA in both supine and right lateral decubitus positions. However, these studies were conducted in non-pregnant patients and the investigators did not come across similar studies conducted with diabetic pregnant women in the literature. Recently, gastric ultrasound scanning before anesthesia in cases where the fasting state is unclear or unknown in the pregnant patient population, which is known to be more risky in terms of pulmonary aspiration, is recommended although not yet widespread in practical use. The effect of diabetes on stomach fullness is still controversial. There are many studies on gastric ultrasound evaluation in pregnant women, but the investigators have not come across a study comparing diabetic pregnant women with non-diabetics. This study was planned based on the idea that the presence of diabetes in pregnant women could further increase the risk of pulmonary aspiration. The primary aim of this research is to compare the antral cross-sectional area (CSA) with gastric ultrasound and estimated gastric volumes calculated with 2 mathematical models in fasting diabetic and non-diabetic term pregnant women who will be taken for cesarean section. The secondary aim is to determine the relationship between demographic and clinical variables and gastric antral CSA values in fasting term pregnant women. the investigators believe that our study will contribute to the literature with its originality and results. Additionally, the investigators believe that our study will provide insight into the effectiveness of fasting guidelines in these patient groups and the necessity of gastric ultrasound scanning."