The study was a prospective observational research project conducted from October 2023 to June 2024 at the Department of Anaesthesiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Pimpri, Pune, Maharashtra, India. Approval from the Institutional Ethics Committee was obtained prior to the commencement of the study (Reference Number: I.E.S.C./103/202; Research Protocol Number: IESC/FP/66/2023).

Inclusion and Exclusion criteria: The study included American Society of Anaesthesiologists (ASA) grade I or II patients aged 18 years or older who were undergoing surgeries under spinal anaesthesia, provided they were haemodynamically stable with normal routine investigations and had given written informed consent. Patients were excluded if they were unwilling to participate, had contraindications for spinal anaesthesia, had ASA grade III or above physical status, were under 18 years of age, required emergency procedures, or had psychiatric, neurological, neuromuscular, or cardiovascular conditions, or impaired hepatic or renal function.

Sample size calculation: Open Epi was used to calculate the sample size. Considering the mean fasting durations as 9.5±2.1 hours in the AM group and 12.7±4.4 hours in the PM group for liquids according to Yeniay O et al., the study required a sample size of 19 in each group with 95% confidence and 80% power [10]. For statistical convenience, 35 patients were included in each group.

Total of 70 patients undergoing elective surgeries under spinal anaesthesia were selected based on the previously outlined inclusion and exclusion criteria. Each patient underwent a preanaesthetic evaluation, relevant laboratory investigations and provided informed written consent. The patients were divided into two groups of 35 each:

The study recorded the time elapsed since the last intake of oral fluids and food until the operation. Each patient received preoperative hydration with 10 mL/kg of intravenous fluids and the volumes were meticulously documented. An intravenous line was established using a 20 G cannula. Standard monitoring equipment, including Electrocardiogram (ECG), non invasive blood pressure, SpO₂ and a temperature probe, was employed to continuously assess the patient. Baseline parameters, including HR, MAP, SpO₂, body temperature and random blood glucose, were recorded. Measurements of MAP, HR and SpO₂ were taken at predetermined intervals: preoperatively and at the zeroth, 2^nd, 5^th, 15^th and 30^th minutes following the administration of spinal anaesthesia. Body temperature was specifically recorded immediately prior to spinal anaesthesia. Spinal anaesthesia was administered under strict aseptic conditions, with continuous monitoring of the aforementioned parameters throughout the surgical procedure and postoperative period. Postoperative data on the incidence of nausea and vomiting, as well as Random Blood Sugar (RBS) levels, were systematically recorded.

The tables were generated for both the AM group (Group A) and the PM group (Group B), summarising parameters such as HR, MAP, SpO₂, body temperature, RBS levels and the incidence of postoperative nausea and vomiting. Data analysis was conducted using Statistical Package for Social Sciences (SPSS) version 20.0. Continuous and discrete variables were described using mean±Standard Deviation (SD) and medians, while categorical variables were reported as numbers and percentages. Categorical data were analysed using Pearson’s Chi-squared test or Fisher’s-exact Test, with p-values <0.05 considered statistically significant.

The study compared demographic and clinical parameters between group A and group B, as shown in [Table/Fig-1]. No significant differences were observed in age (p-value=0.2102), gender distribution (p-value=0.632), weight (p-value=0.288), height (p-value=0.343), BMI (p-value=0.631), or ASA physical status (p-value=0.631). However, a significant difference was found in the preoperative fasting duration, with group B fasting longer than group A (14.2±2.1 hours vs. 9.8±1.5 hours, p<0.001).

Both groups showed a gradual decrease in Mean Arterial Pressure (MAP) and Heart Rate (HR) from the preoperative period to 30 minutes after the administration of spinal anaesthesia. This was an expected physiological response to spinal anaesthesia, which caused sympathetic blockade and a decrease in blood pressure and HR. SpO₂ remained stable and within normal ranges throughout the procedure for both groups, indicating adequate oxygenation. The haemodynamic parameters, including MAP, HR, SpO₂, body temperature and RBS levels, at various time points during the surgical procedure are presented in [Table/Fig-2]. At 15 and 30 minutes, there were statistically significant differences in heart rate when comparing group A with group B, with p-values of 0.0135 and 0.008, respectively.

Notably, group B (PM group) had significantly higher preoperative and postoperative RBS levels compared to group A (AM group), with preoperative RBS levels of 102.3±18.7 mg/dL vs. 89.2±12.5 mg/dL (p<0.001) and postoperative RBS levels of 118.5±22.8 mg/dL vs. 92.7±15.2 mg/dL (p<0.001), as shown in [Table/Fig-3]. Although group B also showed a higher incidence of nausea and vomiting (31.4% vs. 14.3%, p-value=0.087), hypoglycaemia (5.7% vs. 2.9%, p-value=0.555) and hypotension (31.4% vs. 17.1%, p-value=0.163), these differences were not statistically significant, as demonstrated in [Table/Fig-3].

The study compared the AM group (surgery scheduled between 8:00 AM and 12:00 PM) with the PM group (surgery scheduled after 12:00 PM or delayed) to evaluate preoperative fasting duration, intraoperative haemodynamic parameters, blood glucose levels and postoperative outcomes. This assessment aimed to understand the effects of fasting duration on outcomes related to spinal anaesthesia. Despite similar baseline demographic characteristics, group B, which experienced longer fasting due to later surgeries, showed higher RBS levels both preoperatively and postoperatively compared to group A. This suggests that extended fasting may impact glucose metabolism. Although group B also had a higher incidence of nausea, vomiting and hypotension, these differences were not statistically significant. Overall, the findings highlight that prolonged fasting could influence glucose levels and potentially increase postoperative complications, although not all effects reached statistical significance.

The “Practice Guidelines for Preoperative Fasting and the Use of Pharmacologic Agents to Reduce the Risk of Pulmonary Aspiration: An Updated Report” provides specific fasting recommendations: two hours for clear liquids, four hours for breast milk, six hours for infant formula and non human milk, six hours for a light meal and longer fasting times (e.g., 8 or more hours) for fried foods, fatty foods, or meat [2]. The data in this study indicate that the mean fasting duration was 9.8±1.5 hours for the AM group and 14.2±2.1 hours for the PM group, with the PM group experiencing a significantly longer fasting period. Similarly, Yeniay O et al., reported mean fasting durations of 12±2.8 hours for solids and 9.5±2.1 hours for liquids in the AM group and 15.5±3.4 hours for solids and 12.7±4.4 hours for liquids in the PM group, respectively, which aligns with the findings of this study [10].

Ljungqvist O suggested that undergoing surgery in a carbohydrate-fed state, rather than a fasted state, offers clinical benefits, particularly in reducing postoperative insulin resistance through preoperative carbohydrate loading [4]. The role of preoperative carbohydrate treatments, as discussed by Smith MD et al., is integral to Enhanced Recovery After Surgery (ERAS) or fast track surgery protocols, demonstrating a reduction in the length of hospital stay [8].

One of the notable findings was the higher preoperative RBS levels observed in the PM group (102.3±18.7 mg/dL) compared to the AM group (89.2±12.5 mg/dL). This difference could be attributed to the prolonged fasting state in the PM group, which is consistent with previous studies reporting an increase in blood glucose levels after prolonged fasting periods [4,11]. The elevated blood glucose levels in the PM group may result from increased gluconeogenesis and decreased insulin sensitivity, which are physiological responses to fasting [5].

The observed gradual decrease in MAP and HR from the preoperative period to 30 minutes after the administration of spinal anaesthesia in both groups is an expected physiological response to spinal anaesthesia [6]. However, it is noteworthy that the PM group exhibited slightly higher MAP and HR values at most time points compared to the AM group, with statistically significant differences in HR in groups A and B at 15 and 30 minutes. In comparison to the study by Yeniay O et al., the PM group demonstrated a slightly lower MAP and HR that was statistically significant two minutes after the administration of spinal anaesthesia [10]. Although hypotension was noted in a total of six patients in the AM group and 11 patients in the PM group, this difference was not statistically significant.

Interestingly, the present study also revealed a higher incidence of postoperative nausea and vomiting in the PM group (31.4%) compared to the AM group (14.3%). This finding aligns with a study by Svanfeldt M et al., which reported a higher risk of postoperative nausea and vomiting in patients who experienced prolonged fasting before surgery [12]. The authors suggested that prolonged fasting might contribute to dehydration and electrolyte imbalances, which could predispose patients to nausea and vomiting [12]. Marsman M et al., also suggested that patients who followed a liberal preoperative fluid fasting policy showed a clinically significant reduction in fasting duration, postoperative thirst and a decreased incidence of postoperative nausea and vomiting [13].

The findings of the present study are further supported by a systematic review by Awad S and Lobo DN, which highlighted the potential adverse effects of prolonged fasting on postoperative outcomes, including insulin resistance, hyperglycaemia and an increased risk of nausea and vomiting [3]. They emphasised the importance of implementing strategies to minimise the duration of preoperative fasting, such as carbohydrate loading or allowing clear fluids up to two hours before surgery. The findings listed above highlight the need for careful consideration of preoperative fasting guidelines and the potential benefits of implementing strategies to minimise prolonged fasting periods, such as carbohydrate loading or allowing clear fluids closer to surgery [8,9].

It is important to note that the present study had certain limitations, including the lack of randomisation in group allocation. Additionally, potential confounding factors, such as the amount of spinal anaesthesia drug administered and co-morbidities that could have influenced the observed outcomes, were not assessed.

In conclusion, the present study adds to the growing body of evidence suggesting that unexpected prolonged fasting before elective surgery under spinal anaesthesia may have adverse effects on intraoperative and postoperative parameters, including higher blood glucose levels and an increased risk of postoperative nausea and vomiting. Timely recognition and appropriate management of prolonged fasting periods could contribute to enhancing patient safety and improving postoperative recovery.