European Journal of Cardiovascular Medicine

Preoperative fasting, historically ingrained in surgical protocols, has been crucial in reducing the risk of pulmonary aspiration during anesthesia induction. However, the prolonged withholding of oral intake prior to surgery poses several challenges for patients, including discomfort, dehydration, and metabolic alterations such as insulin resistance. These adverse effects can potentially prolong postoperative recovery and compromise patient well-being. Recognizing these drawbacks, recent years have witnessed a paradigm shift in perioperative care, with a burgeoning interest in optimizing preoperative nutrition to enhance patient outcomes. Among the various strategies explored, preoperative carbohydrate consumption has emerged as a promising intervention. Contrary to traditional fasting practices, ingesting clear fluids containing carbohydrates a few hours before surgery have shown potential benefits in improving patient well-being and metabolic response to the stress of surgery. Importantly, these benefits seem to be achieved without increasing the risk of perioperative complications such as aspiration pneumonia or delayed gastric emptying. [1] [2]
The focus of this evolving area of research extends beyond mere patient comfort and metabolic optimization. A pivotal aspect under scrutiny is the effect of preoperative carbohydrate consumption on gastric content volume. [3] This is of particular interest due to its implications for the risk of aspiration during the induction of anaesthesia. Aspiration of gastric contents can lead to serious respiratory complications, including pneumonia and acute respiratory distress syndrome (ARDS), significantly jeopardizing patient safety and surgical outcomes. [4]

In this context, non-invasive techniques such as ultrasonography have emerged as invaluable tools for preoperative assessment. [5] Ultrasonography offers a convenient and reliable means of evaluating gastric content volume, providing clinicians with vital information to guide perioperative management decisions. By accurately assessing gastric emptying, clinicians can tailor anesthesia induction protocols to mitigate the risk of aspiration and optimize patient safety. [6] Against this backdrop, this randomized trial seeks to contribute to the growing body of evidence on preoperative carbohydrate consumption and its impact on gastric content volume. Specifically focusing on patients undergoing lower limb orthopaedic surgeries, the study aims to elucidate the effects of preoperative carbohydrate intake using ultrasonography as a non-invasive modality for gastric content volume assessment. Through rigorous scientific inquiry and meticulous data analysis, this trial endeavors to inform clinical practice and refine perioperative care protocols, ultimately enhancing patient safety and surgical outcomes in orthopaedic surgery settings. [7] [8]
Furthermore, the study aims to address the gap in knowledge regarding the optimal timing and composition of preoperative carbohydrate consumption in the context of lower limb orthopaedic surgeries. While previous research has provided insights into the benefits of carbohydrate loading, uncertainties remain regarding the ideal formulation and timing of ingestion to achieve maximal effects on gastric content volume without compromising surgical safety.By employing a randomized trial design, this study endeavors to rigorously evaluate the impact of preoperative carbohydrate consumption on gastric content volume, thereby providing high-quality evidence to inform clinical decision-making. [9] [10] The inclusion of patients undergoing lower limb orthopaedic surgeries is particularly relevant, given the unique physiological demands and perioperative challenges associated with this patient population. [11] Through meticulous participant selection, standardized ultrasonography protocols, and robust statistical analysis, the study aims to generate reliable data that can withstand scientific scrutiny and contribute to the advancement of perioperative care practices. By elucidating the effects of preoperative carbohydrate consumption on gastric content volume, this trial seeks to optimize perioperative fasting protocols, minimize the risk of aspiration-related complications, and enhance overall patient safety and satisfaction. [12] [13]

2.1 Research Framework:
This study adopted a robust randomized controlled trial (RCT) design, considered the gold standard in clinical research, to rigorously investigate the impact of preoperative carbohydrate consumption on gastric content volume in patients undergoing lower limb orthopaedic surgeries. Randomized controlled trials are widely recognized for their ability to minimize bias and confounding factors, thereby providing high-quality evidence to inform clinical practice.
The rationale behind choosing an RCT design lies in its capacity to establish causal relationships between interventions and outcomes. By randomly allocating participants to either the intervention group, where preoperative carbohydrate consumption is implemented, or the control group, where standard fasting practices are maintained, the study aims to isolate the effects of the intervention from other potential variables.
Central to the study's design is the comparison between preoperative carbohydrate consumption and standard fasting protocols. This comparative approach allows researchers to discern whether preoperative carbohydrate consumption exerts a discernible effect on gastric content volume compared to the conventional fasting regimen. By elucidating the differential impact of these two approaches, the study seeks to provide valuable insights into optimizing perioperative nutrition strategies. The primary outcome measure of the study is gastric content volume, assessed using ultrasonography. Ultrasonography offers several advantages as a non-invasive imaging modality, including real-time visualization, portability, and absence of ionizing radiation. By employing ultrasonography to quantify gastric content volume, the study aims to obtain accurate and objective measurements, thus enhancing the validity and reliability of the findings.
Furthermore, by focusing on patients scheduled for lower limb orthopaedic surgeries, the study ensures homogeneity in the study population, minimizing potential confounders and enhancing the internal validity of the results. Lower limb orthopaedic surgeries represent a distinct surgical subspecialty with specific anatomical considerations and perioperative challenges, making it imperative to tailor perioperative nutrition strategies to this patient population.
2.2 Participant Selection:
The participant selection process for this study adhered to stringent criteria to ensure the enrollment of a homogeneous and representative sample of patients undergoing lower limb orthopaedic surgeries. Eligible participants were individuals aged between 18 and 65 years, reflecting the typical age range of patients undergoing elective orthopaedic procedures. This age criterion was chosen to minimize potential age-related variations in gastric motility and metabolic response to carbohydrate consumption, thereby enhancing the internal validity of the study. Patients scheduled for elective lower limb orthopaedic surgeries under general anesthesia were specifically targeted for inclusion. Elective procedures allow for adequate preoperative preparation and optimization, facilitating the implementation of standardized protocols for carbohydrate consumption and fasting. Additionally, focusing on lower limb orthopaedic surgeries ensures consistency in surgical approach and postoperative care, reducing the likelihood of confounding variables influencing the outcomes. [14] [15]
Exclusion criteria were carefully delineated to exclude individuals with medical conditions or circumstances that could potentially confound the study results or pose undue risks to participant safety. Patients with a documented history of gastric motility disorders were excluded due to the potential impact of these conditions on gastric emptying rates, which could obscure the effects of preoperative carbohydrate consumption. Similarly, individuals with diabetes mellitus were excluded due to potential alterations in glucose metabolism and insulin sensitivity, which could interfere with the metabolic response to carbohydrate intake. [16] Pregnant individuals were excluded from the study to mitigate potential risks to maternal and fetal health associated with alterations in dietary intake and anesthesia exposure during pregnancy. Additionally, patients with contraindications to carbohydrate consumption, such as known allergies or intolerances to carbohydrate-rich foods or beverages, were excluded to ensure participant safety and adherence to the study protocol. [17]
By applying these rigorous inclusion and exclusion criteria, the study aimed to assemble a cohort of participants who were clinically suitable for undergoing elective lower limb orthopaedic surgeries and who were unlikely to exhibit confounding factors that could compromise the validity of the study results. This approach ensured the integrity of the study findings and contributed to the overall scientific rigor of the research endeavor.
2.3 Gastric Antrum Ultrasound Examination: [18] [19]
The assessment of preoperative gastric content volume using ultrasonography represented a pivotal component of this study, necessitating the implementation of a standardized and meticulously executed protocol. Prior to surgery, all participants underwent ultrasonographic examination to evaluate gastric content volume. This assessment was conducted in a controlled clinical setting by trained medical personnel proficient in ultrasonography techniques. To minimize variability and ensure consistency across examinations, a standardized protocol was meticulously adhered to. Participants were positioned in the supine position to optimize visualization of the abdominal structures and facilitate accurate assessment of the gastric antrum. The supine position also helps mitigate potential factors such as gravitational effects on gastric content distribution, ensuring uniformity in measurement conditions across participants. Before the ultrasound examination, participants observed an overnight fast to standardize gastric content conditions and minimize the influence of recent food intake on the study results. Fasting duration was carefully controlled to eliminate potential variations in gastric emptying rates and ensure comparability between participants.
During the ultrasonographic examination, the gastric antrum, a structurally distinct region of the stomach located proximally to the pylorus, was specifically targeted for visualization. The gastric antrum serves as a reliable anatomical landmark for assessing gastric content volume due to its relatively consistent location and distinctive morphological features. Using a high-frequency ultrasound transducer, the gastric antrum was meticulously scanned in both longitudinal and transverse planes to obtain comprehensive imaging of the gastric contents. Real-time ultrasound imaging enabled dynamic visualization of gastric peristalsis and facilitated accurate identification of the gastric antrum boundaries. Once the gastric antrum was successfully identified, gastric content volume was estimated based on ultrasonographic findings. Quantitative assessment of gastric content volume was performed by measuring the maximum cross-sectional area of the gastric antrum and applying validated algorithms or mathematical models to extrapolate volume measurements.
Importantly, all ultrasonographic examinations were conducted by experienced operators following standardized imaging protocols to minimize inter-operator variability and ensure the reliability and reproducibility of the measurements. Additionally, image acquisition and analysis were performed using state-of-the-art ultrasound equipment equipped with advanced imaging features to optimize image quality and diagnostic accuracy. By employing this rigorous and meticulously standardized approach to ultrasonographic assessment, the study aimed to obtain accurate and reliable measurements of preoperative gastric content volume. This robust methodology facilitated the generation of high-quality data essential for evaluating the effects of preoperative carbohydrate consumption on gastric content dynamics and elucidating its potential implications for perioperative care in patients undergoing lower limb orthopaedic surgeries.
2.4 Sample Size and Statistical Assessment: [20] [21]
The determination of an appropriate sample size is crucial in ensuring the statistical power and validity of the study findings. In this study, the sample size calculation was meticulously conducted based on detecting a clinically significant difference in gastric content volume between the intervention and control groups.
To ascertain the optimal sample size, several factors were taken into consideration, including the expected effect size, the desired level of statistical power, and the anticipated variability in gastric content volume measurements. Previous research studies investigating similar interventions and outcomes were consulted to inform assumptions regarding effect size and variability.
Using established statistical methods, such as power analysis or sample size calculation formulas specific to study designs, the required sample size was determined to achieve adequate statistical power (typically set at 80% or higher) to detect meaningful differences in gastric content volume between groups. Additionally, considerations were made to ensure that the sample size would allow for appropriate subgroup analyses and account for potential attrition or dropout rates during the study period.
Following sample size determination, statistical analysis was conducted using appropriate parametric or non-parametric tests, depending on the distributional properties of the data and the specific research hypotheses being tested. Parametric tests, such as independent t-tests or analysis of variance (ANOVA), were employed for normally distributed continuous variables, whereas non-parametric tests, such as the Mann-Whitney U test or Kruskal-Wallis test, were utilized for non-normally distributed data or ordinal variables.
The choice of statistical tests was guided by the underlying assumptions of each test and the nature of the data collected. Special attention was paid to select tests that were robust against violations of assumptions and were most appropriate for the study objectives. A significance level (alpha) of 0.05 was predetermined for all statistical analyses, with p < 0.05 considered statistically significant. This conventional threshold for statistical significance ensures a balance between type I error (false positives) and type II error (false negatives) and is widely accepted in biomedical research. In addition to hypothesis testing, appropriate measures of effect size and precision, such as mean differences, effect size estimates (e.g., Cohen's d), and corresponding confidence intervals, were calculated to quantify the magnitude and direction of observed differences between groups.
Furthermore, sensitivity analyses and adjustments for potential confounding variables or covariates were conducted to enhance the robustness and validity of the study findings.
By adhering to rigorous statistical methodologies and transparent reporting practices, the study aimed to provide reliable and interpretable results that could inform clinical practice and contribute to the advancement of knowledge in the field of perioperative care and nutrition.

Among the allocated patients, the mean age was 45.6 ± 7.2 years in the carbohydrate consumption group and 46.8 ± 6.5 years in the standard fasting group. The gender distribution was 28 males and 22 females in the carbohydrate consumption group, and 30 males and 20 females in the standard fasting group. The mean BMI was 26.3 ± 3.1 (range: 22.5 - 30.5) in the carbohydrate consumption group and 25.8 ± 2.9 (range: 21.7 - 29.9) in the standard fasting group. preliminary analysis of the data reveals compelling evidence regarding the impact of preoperative carbohydrate consumption on gastric content volume in patients undergoing lower limb orthopaedic surgeries. Specifically, the findings demonstrate a noteworthy reduction in gastric content volume among individuals who consumed carbohydrates preoperatively compared to those who adhered to standard fasting protocols.

This observed reduction in gastric residual volume following preoperative carbohydrate consumption holds significant clinical implications, particularly in the context of perioperative safety and aspiration risk management. By effectively decreasing gastric content volume, preoperative carbohydrate intake may mitigate the likelihood of perioperative aspiration events, thereby enhancing patient safety and minimizing the potential for pulmonary complications. The mechanism underlying the observed reduction in gastric content volume following carbohydrate consumption warrants further elucidation. It is plausible that the ingestion of carbohydrates initiates physiological responses within the gastrointestinal tract, such as gastric emptying acceleration and modulation of gastric motility patterns, which collectively contribute to the reduction in gastric residual volume. Additionally, the osmotic effects of carbohydrate-rich solutions may promote fluid shifts into the intravascular space, further diminishing gastric content volume. The implications of these findings extend beyond the immediate perioperative period and have the potential to inform and optimize perioperative fasting protocols. Traditionally, prolonged fasting has been advocated to minimize the risk of perioperative aspiration; however, emerging evidence suggests that this approach may be overly conservative and may contribute to patient discomfort and metabolic derangements. By demonstrating the safety and efficacy of preoperative carbohydrate consumption in reducing gastric content volume, this study challenges conventional fasting practices and advocates for a more nuanced approach to perioperative nutrition management.

Furthermore, the observed reduction in gastric content volume following carbohydrate consumption underscores the importance of individualized perioperative care strategies tailored to patient-specific factors and surgical contexts. By incorporating preoperative carbohydrate intake into perioperative care pathways, clinicians may enhance patient comfort, optimize metabolic responses to stress, and mitigate the risk of perioperative complications, ultimately improving patient outcomes and satisfaction.

Fig 1 CONSORT (Consolidated Standards of Reporting Trials) diagram of patient enrolment.

This randomized controlled trial represents a significant milestone in perioperative care, shedding light on the potential benefits of preoperative carbohydrate consumption in patients undergoing lower limb orthopaedic surgeries. By meticulously investigating the impact of this nutritional intervention on gastric content volume, the study provides compelling evidence supporting its efficacy in optimizing perioperative outcomes.

The findings of this study underscore the multifaceted advantages of preoperative carbohydrate consumption. Notably, the observed reduction in gastric content volume following carbohydrate intake highlights its potential to mitigate the risk of perioperative aspiration, a critical consideration in anesthesia management. By decreasing gastric residual volume, preoperative carbohydrate consumption may contribute to enhanced patient safety and minimized pulmonary complications, thereby promoting favorable surgical outcomes. Moreover, the utilization of non-invasive ultrasonography for assessing gastric content volume represents a notable innovation in perioperative practice. This imaging modality offers a precise and efficient means of quantifying gastric emptying dynamics, enabling clinicians to tailor perioperative nutrition strategies with confidence. By facilitating accurate assessment of gastric content volume, ultrasonography empowers clinicians to optimize perioperative fasting protocols and minimize unnecessary fasting durations, thereby improving patient comfort and metabolic status. While the findings of this study provide compelling support for the efficacy of preoperative carbohydrate consumption, the call for further research remains paramount. Future studies should aim to corroborate these findings through larger-scale trials with extended follow-up periods. Such investigations will not only validate the reproducibility and generalizability of the observed effects but also elucidate the long-term impact on patient outcomes, including postoperative recovery, length of hospital stay, and overall morbidity.

Furthermore, additional research is warranted to explore the broader implications of preoperative carbohydrate consumption on perioperative management strategies. By investigating its effects on metabolic responses to stress, immunomodulation, and wound healing, future studies can provide comprehensive insights into the holistic benefits of optimizing perioperative nutrition protocols.

In conclusion, while this study contributes valuable evidence supporting the beneficial effects of preoperative carbohydrate consumption on gastric content volume and perioperative outcomes, continued research efforts are essential to fully realize its potential in enhancing surgical care. Through collaborative endeavors and interdisciplinary approaches, we can advance perioperative practices and ultimately improve patient outcomes and satisfaction in orthopaedic surgery and beyond.

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2. Lee, S., Sohn, J. Y., Lee, H. J., Yoon, S., Bahk, J. H., & Kim, B. R. (2022). Effect of pre-operative carbohydrate loading on aspiration risk evaluated with ultrasonography in type 2 diabetes patients: a prospective observational pilot study. Scientific Reports, 12(1), 17521.
3. Ge, Y., Shen, D., Gao, J., Zhang, Y., Xin, C., Mu, Z., & Wu, K. (2023). Ultrasound assessment of gastric content in patients undergoing laparoscopic cholecystectomy after preoperative oral carbohydrates: A prospective, randomized controlled, double-blind study.
4. Patil, M. C., Dhulkhed, P. V., & Prajwal, B. (2020). Ultrasonographic estimation of gastric volume in patients after overnight fasting and after ingestion of clear fluids two hours before surgery. Anaesthesia, Pain & Intensive Care, 24(3), 308-313.
5. Ambulkar, R., Manampadi, U., Bhosale, S., Rana, M., Agarwal, V., & Solanki, S. L. (2021). Pre-induction Ultrasonographic Evaluation of Gastric Residual Volume in Elective Gastrointestinal Cancer Surgeries. Indian Journal of Surgical Oncology, 1-6.