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Langenbecks Arch Surg
Langenbecks Arch Surg
Langenbeck's Archives of Surgery
1435-2443
1435-2451
Springer Berlin Heidelberg Berlin/Heidelberg

39254773
3468
10.1007/s00423-024-03468-9
Research
Effects of oral carbohydrate loading in patients scheduled for painless bidirectional endoscopy: a prospective randomized controlled trial
Guo Lan 1
Liu Pengfei 2
Jiang Xinyue 1
Shan Zhengru 1
Wang Rui 2
Wang Zhiping zhpsqxt@126.com

23
1 grid.417303.2 0000 0000 9927 0537 Xuzhou Medical University, Xuzhou, Jiangsu 221004 China
2 grid.413389.4 0000 0004 1758 1622 Department of Anesthesiology, The Affiliated Hospital of Xuzhou Medical University, Xuzhou, Jiangsu 221002 China
3 grid.417303.2 0000 0000 9927 0537 Jiangsu Province Key Laboratory of Anesthesiology, Xuzhou Medical University, Xuzhou, Jiangsu 221004 China
10 9 2024
10 9 2024
2024
409 1 2756 7 2024
2 9 2024
© The Author(s) 2024
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ Open Access This article is licensed under a Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License, which permits any non-commercial use, sharing, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if you modified the licensed material. You do not have permission under this licence to share adapted material derived from this article or parts of it. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by-nc-nd/4.0/.
Purpose

Traditional fasting causes considerable discomfort without added assurance of security, whereas oral carbohydrate beverage offers an alternative to improve medical experience. This study aims to explore the impact of different types and dosages of oral fluids loading before painless bidirectional endoscopy on the gastric emptying and wellbeing.

Methods

180 patients arranged for bidirectional endoscopy with intravenous anesthesia were randomized: patients in the control group (Group C) obeyed standard fasting; the 200 mL carbohydrate group (Group P1), 400 mL carbohydrate group (Group P2), 200 mL water group (Group W1) and 400 mL water group (Group W2) respectively consumed 200 mL or 400 mL corresponding clear liquids 2 h before the procedure. Gastric emptying metrics under ultrasound, subjective comfort indexes, periprocedural blood glucose and vital signs were contrasted among the groups.

Results

No significant differences were detected in the gastric emptying including CSA (cross-sectional area), GV (gastric volume), cGV (corrected gastric volume) and the three-point grading system among groups, and none had a cGV > 1.5 mL/kg before anesthesia. Participants in Group P2 experienced less preprocedural thirst and mouth dryness, so as the postprocedural thirst, mouth dryness and hunger. Periprocedural blood glucose and MAP had the similar trend in all groups. The occurrence of hypotension, bradycardia, hypoxia, and the required norepinephrine was comparable among the groups.

Conclusions

Oral beverage loading with 200 mL or 400 mL can be safely applicated 2 h before painless bidirectional endoscopy without increasing the gastric volume. 400 mL carbohydrate solution effectively relieves the discomfort and could serve as a consideration.

Trial registration

Registered in the Chinese Clinical Trial Registry on December 5, 2023 (ChiCTR2300078319).

Keywords

Blood glucose
Carbohydrate
Endoscopy
Gastric emptying
Ultrasonic
National Natural Science Foundation of China82270059 Natural Science Foundation of Jiangsu ProvinceBK20221222 China Primary Health Care FoundationYLGX-MZ-2022004 issue-copyright-statement© Springer-Verlag GmbH Germany, part of Springer Nature 2024
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pmcBackground

The practice of fasting after midnight on the day before anesthesia remains prevalent in China [1]. Extended fasting intensifies the discomfort such as hunger, thirst, nausea and anxiety, which may adversely affect the clinical outcomes [2–5]. Besides, prolonged fasting exacerbates the physiological stress reaction towards surgery, contributing to insulin resistance [6]. In this hyporesponsive state, nutrients cannot be efficiently utilized by peripheral tissues and hepatic glycogen output is inhibited, accelerating skeletal muscle catabolism [7].

The Enhanced Recovery After Surgery (ERAS) has evolved rapidly since its introduction, which applies evidence-based programs to minimize the physical burden and complications associated with surgeries [8]. Oral carbohydrate, as a vital component of ERAS, is of increasing interest among academics for their favorable impact on patient outcomes [9]. The latest guidelines for fasting suggest the preoperative consumption of clear liquids up to 2 h, with a preference for carbohydrate-containing beverages [10].

Over the latest three-decade span, digestive diseases remain prevalent and constitute a significant global health challenge [11]. As a crucial tool for diagnosing digestive tract diseases, there has been a dramatic surge in the scale of gastrointestinal endoscopy [12]. Patients prefer to receive gastroduodenoscopy and colonoscopy in one hospital visit, known as the same-visit bidirectional endoscopy [13]. For these outpatients who often lack of professional and timely care prior to hospitalization, the adverse effects of prolonged fasting were further aggravated due to the laxative use, a liquid diet, an indefinite examination period and the absence of intravenous fluid replacement. Oral carbohydrate has been confirmed safe and has shown to positively influence various clinical outcomes during elective surgeries [14]. Thus, it could be a possible method to alleviate physiological and psychological burden for patients prepared for digestive endoscopy.

This randomized controlled trial was executed to assess the effects of oral carbohydrate loading on gastric emptying, periprocedural wellbeing, blood glucose levels and hemodynamic changes in patients scheduled for elective painless bidirectional endoscopy. We hypothesized that routinely administering oral carbohydrates 2 h before anesthesia would be feasible in these subjects.

Methods

Participants

Patients eligible for the prospective randomized study were those aged between 18 and 65 years old, possessed a body mass index (BMI) within the range of 18 to 30 kg/m², classified as American Society of Anesthesiologists (ASA) physical status I-II and prepared for painless gastroduodenoscopy and colonoscopy during a single hospital visit (bidirectional endoscopy).

Exclusion criteria included individuals with serious brain, heart, lung, liver, kidney or metabolic diseases; a previous history of gastrointestinal surgery; poorly managed hypertension, or with hypotension defined as < 90/60 mmHg; diabetes with unstable blood glucose or related complications; women who were pregnant, lactating, or menstruating; patients who took medicine affecting gastric emptying. In addition, individuals suspected of gastroesophageal reflux disease, achalasia, severe eating or drinking disorders and hearing deterioration were also excluded.

Intervention

Group assignments were sequentially revealed by opening sealed envelopes, each containing a computer-generated code for block randomization. While making arrangements for their endoscopy, patients qualified for inclusion were distributed to the distinct groups by a specialized nurse: the control group (Group C), the 200 mL carbohydrate group (Group P1), the 400 mL carbohydrate group (Group P2), the 200 mL water group (Group W1) and the 400 mL water group (Group W2). Meanwhile, participants received their corresponding liquid and consumption instructions to ensure their compliance with the study protocol. All patients were required to follow the standard fasting protocol in our hospital, which included ceasing food intake from 20:00 on the eve of the examination and refraining from all drinks on the day of the scheduled check-up. The intervention groups additionally consumed a predetermined volume of either carbohydrate beverage or pure water 2 h prior to their appointment within 10 min.

The carbohydrate solution (Outfast, 200 mL/bottle, Yichang Human well FSMP CO., LTD., Yichang, China) in this study, per 100 mL, provides 213 kJ energy and contains 12.5 g carbohydrates, 50 mg sodium, 66.7 mg potassium, 63.0 mg phosphorus, 65 mg chloride, 6 mg calcium, and 1 mg magnesium, with an osmolarity of 290 mOsm/kg.

Neither the patients nor the nurses responsible for distributing the beverages were blinded regarding group allocations, whereas the other investigators including operators, anesthesiologists and statistical analysts remained unaware. The examinations were performed by a consistent team of gastroenterologists, and all patients received standardized care.

Data collection

The principal outcome was the gastric emptying via ultrasonography. Secondary outcomes included wellbeing quantified using Visual Analog Scale (VAS) scores: thirst, mouth dryness, hunger, nausea, vomiting, abdominal distention, abdominalgia and belching. Additionally, blood glucose, vital signs and the occurrence of aspiration events were also involved.

During the pre-anesthetic evaluation, an anesthesiologist not involved in other research tasks obtained informed consent and recorded the participants’ basic information. On the day of the scheduled examination, the reception nurse reconfirmed and documented the patients’ fasting status. All patients were administered intravenous anesthesia comprising etomidate 4–6 mg, ciprofol 0.4 mg/kg, and remifentanil 0.2 µg/kg for induction, with ciprofol 0.8 mg/kg/h and remifentanil 0.02 µg/kg/min employed for maintenance.

Upon entering the room, an experienced anesthetist utilized an ultrasound device to acquire cross-sectional images of the gastric antrum in the supine and right lateral decubitus (RLD) positions at peristaltic intervals. A 2–5 MHz convex array probe was employed to scan the upper abdomen vertically from right to left in the sagittal plane. Ultrasonography was captured among the hepatic left lobe, the superior mesenteric artery and the abdominal aorta.

The contents of the gastric antrum were scanned in both positions and evaluated using a semi-quantitative three-point grading system: a grade 0 antrum is vacant in both positions; a grade 1 antrum merely has visible clear fluid in the RLD; a grade 2 antrum contains fluid in both positions [15]. The cranial-caudal (CC) and antero-posterior (AP) diameters of the gastric antrum were measured in the RLD. The equation below was used to estimate the cross-sectional area (CSA): CSA = (π × AP × CC) / 4. A previously validated model was applied to quantify the gastric volume (GV): GV = 27 + 14.6×CSA (cm2) − 1.28 × age (years) [16]. cGV was calculated by dividing GV by weight.

Patient wellbeing was evaluated using the VAS scores before induction and after recovery in the post-anesthesia care unit (PACU). The scale employed comprises a horizontal line of 10 cm, with “very comfortable” marked at 0 and “extremely uncomfortable” marked at 10. When researchers inquire about the relevant indicators, the patients were required to mark their subjective experience on the scale, with the score being the length from 0 to the marked point.

The blood glucose meter (Yuyue 590, manufactured by Jiangsu Yuyue Medical Equipment Co., Ltd.) was utilized to measure blood glucose at three time points: upon entering the examination room (T0), the time to withdraw the colonoscope (T5) and after recovery in the PACU (T7). The occurrence of hypoglycemia and hyperglycemia were documented throughout the peri-examination period.

The mean arterial pressure (MAP), pulse oxygen saturation (SpO2), and heart rate (HR) were documented at the specific time points: upon entering the room(T0), immediately after anesthesia induction(T1), beginning to insert the gastroscope (T2), the time to regress the gastroscope (T3), immediately after inserting the colonoscope (T4), the time to withdraw the colonoscope (T5) and upon leaving the examination room (T6). Desaturation was defined as SpO2 falling below 90% for 10 s or longer, prompting increased inhaled oxygen flow or necessary airway intervention. MAP less than 60 mmHg or decreasing greater than 20% from baseline was considered to be a state of hypotension, and an intravenous dose of 3 mg ephedrine or 40 µg isoprenaline was administrated when lasted for more than 1 min.

Data analysis

Referring to the clinical study of preoperative oral carbohydrate drink before ambulatory surgery, a threshold of 0.2 mL/kg for the corrected gastric volume (cGV) was set to demonstrate the non-inferiority of gastric emptying [1]. 30 cases were needed per group with a predicted standard deviation of 0.27 mL/kg and established α = 0.025, β = 0.2. Considering the influence of 20% drop-out rate, we required a minimum of 190 participants.

Fig. 1 Flowchart of the participants included in the analysis

The statistical analysis was conducted with SPSS 27.0 (SPSS, Inc., Chicago, IL.). Quantitative data with a normal distribution are presented as mean ± standard deviation and were analyzed by one-way ANOVA. Described as the median and interquartile range, the non-normally distributed quantitative variables were compared among groups with the Kruskal-Wallis H test. For categorical data, which are expressed as case (%), the chi-squared test or Fisher’s exact test was applicated for analysis. Repeated measurement data were analyzed using analysis of variance of repeated measurement data for inter-group comparison, time-point comparison and inter-group trend analysis. Multiple comparisons were conducted using either Tukey or Bonferroni, and P < 0.05 was considered statistically significant.

Results

From December 2023 to April 2024, 194 individuals out of 201 were eligible and 180 patients finally completed the study and were analyzed. The study flow is displayed below (Fig. 1).

Table 1 Baseline characteristics of the participants

	Group C	Group P1	Group P2	Group W1	Group W2	
Sex (Male)	18(50.0%)	23(63.9%)	21(58.3%)	15(41.7%)	18(50.0%)	
Age (year)	46.64 ± 11.27	46.42 ± 10.42	45.39 ± 11.62	47.06 ± 9.84	48.17 ± 10.53	
Height (cm)	166.00 ± 8.04	165.42 ± 6.80	167.83 ± 7.01	165.17 ± 8.55	165.94 ± 6.92	
Weight (kg)	66.44 ± 9.75	65.36 ± 7.05	66.53 ± 9.05	65.69 ± 9.27	63.33 ± 7.81	
BMI (kg/m²)	24.08 ± 2.92	23.88 ± 2.12	23.58 ± 2.68	23.99 ± 2.01	22.97 ± 2.19	
Fasting time for solids (h)	20.89 ± 3.02	20.47 ± 2.42	20.40 ± 2.30	21.14 ± 2.05	19.86 ± 2.26	
ASA classification (I)	26(72.2%)	27(75.0%)	25(69.4%)	25(69.4%)	26(72.2%)	
Examination history	11(30.6%)	10(27.8%)	11(30.6%)	9(25.0%)	9(25.0%)	
Comorbidity						
Hypertension	9(25.0%)	8(22.2%)	9(25.0%)	10(27.8%)	9(25.0%)	
Diabetes	1(2.8%)	0(0%)	1(2.8%)	1(2.8%)	2(5.6%)	
Etomidate (mg)	6(2)	6(2)	6(2)	6(2)	6(2)	
Ciprofol (mg)	42.96 ± 9.80	41.78 ± 8.98	43.56 ± 8.17	41.63 ± 9.67	44.07 ± 9.16	
Remifentanil (µg)	34.37 ± 7.83	33.43 ± 7.18	35.26 ± 6.16	33.42 ± 7.58	35.26 ± 7.35	
Infusion volume (mL)	100(250)	100(138)	100(150)	150(238)	100(188)	
Values are mean ± standard deviation, median (interquartile range), or number (%)

BMI, body mass index; ASA, American Society of Anesthesiologists; Group C, the control group; Group P1, the 200 mL carbohydrate group; Group P2, the 400 mL carbohydrate group; Group W1, the 200 mL water group; Group W2, the 400 mL water group

Table 1 shows the sex, age, height, weight, BMI, fasting time for solids, ASA classification, bidirectional endoscopy examination history, comorbidity, anesthetic dosage and infusion volume of sodium chloride among the groups. The actual fasting time for liquids is as follows (h): 18.14±4.49, 2.63±0.38, 2.70±0.34, 2.71±0.48, 2.68±0.41.

No evidence of delayed gastric emptying

Table 2 Ultrasonography assessment of gastric emptying

	Group C	Group P1	Group P2	Group W1	Group W2	P value	
CSA (cm²)	5.20 ± 1.21	5.50 ± 1.32	5.84 ± 1.80	5.37 ± 1.26	5.71 ± 1.30	0.300	
GV (mL)	43.20 ± 14.53	47.90 ± 14.44	54.21 ± 24.17	45.21 ± 17.58	48.68 ± 20.54	0.191	
cGV (mL/kg)	0.66 ± 0.24	0.74 ± 0.24	0.81 ± 0.33	0.70 ± 0.28	0.78 ± 0.32	0.160	
Grade (0/1)	25/11	20/16	18/18	23/13	19/17	0.422	
Values are mean ± standard deviation or number

CSA, cross-sectional area; GV, gastric volume; cGV, corrected gastric volume, Grade, the three-point grading system

Table 3 VAS scores for the subjective well-being

	Group C	Group P1	Group P2	Group W1	Group W2	P Value		
     Before induction	
Thirst	2 (3) ###	2 (2) #	0 (2)	2 (3) ##	1 (3) *	0.004		
Mouth dryness	3 (3)	2 (2)	1 (4) **	2 (3)	1 (3) **	0.017		
Hunger	4 (3)	2 (2)	2 (4)	3 (3)	2 (3)	0.075		
Nausea	0 (2)	0 (1)	0 (1)	0 (1)	0 (1)	0.708		
Vomiting	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0.241		
Abdominal distention	0 (1)	0 (0)	0 (1)	0 (1)	0 (1)	0.878		
Abdominalgia	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0.976		
Belching	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0.993		
     After recovery	
Thirst	2 (2)	2 (2) #	1 (2) **	2 (2)	2 (3) **	0.012		
Mouth dryness	3 (3)	2 (2)	2 (1) **	2 (3) *	2 (3) *	0.035		
Hunger	4 (3) #	2 (3)	1 (4)	3 (3) ##	3 (3)	0.026		
Nausea	0 (1)	0 (1)	0 (1)	0 (1)	0 (1)	0.998		
Vomiting	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0.372		
Abdominal distention	0 (2)	0 (0)	0 (1)	0 (1)	0 (1)	0.802		
Abdominalgia	0 (1)	0 (1)	0 (1)	0 (1)	0 (1)	0.768		
Belching	0 (0)	0 (0)	0 (0)	0 (0)	0 (0)	0.799		
Values are median (interquartile range). The Kruskal-Wallis H test was used for overall comparison, and when P < 0.05, the Tukey method was adopted for further pairwise comparisons among the groups

*P<0.05, **P<0.01, ***P<0.001 compared with Group C; #P<0.05, ##P<0.01, ###P<0.001 compared with Group P2

The quantitative and semi-quantitative results of the gastric content based on ultrasound evaluation are summarized in Table 2. Despite an increased tendency for residual gastric fluid with the volume of fluid consumed, no significant differences in CSA, GV and cGV were found among the groups, nor in the three-point grading system. None had a cGV exceeding 1.5 ml/kg and no incidence of gastric content regurgitation was recorded during anesthesia.

Better experience in thirst, mouth dryness and hunger

Before induction, Group P2 reported significantly less thirst compared to Group C (P < 0.001), Group P1 (P = 0.011) and Group W1 (P = 0.008), with Group W2 also showing a reduced thirst versus Group C (P = 0.017). The degree of mouth dryness was reduced in Group P2 (P = 0.002) and Group W2 (P = 0.005) in comparison with Group C. After recovery in the PACU, the discomfort associated with thirst was alleviated in Group P2 (P = 0.002) and Group W2 (P = 0.009) while compared to Group C, with Group P2 exhibiting a better experience than Group P1 (P = 0.023). Regarding mouth dryness, Group C had significantly higher scores than Group P2 (P = 0.002), Group W1 (P = 0.049) and Group W2 (P = 0.044). Patients in Group P2 also experienced less hunger than those in Group C (P = 0.013) and Group W1 (P = 0.002) (Table 3).

Fig. 2 Periprocedural blood glucose. **P < 0.01 compared with T5; ***P < 0.001 compared with T7. T0, upon entering the room; T5, the time to withdraw the colonoscope; T7, after recovery in the PACU

Fig. 3 MAP during the peri-examination. *P < 0.05 compared with any other time point; #P < 0.05 compared with T4 and T5; ##P < 0.05 compared with T5. T0, upon entering the room; T1, immediately after anesthesia induction; T2, beginning to insert the gastroscope; T3, the time to regress the gastroscope; T4, immediately after inserting the colonoscope; T5, the time to withdraw the colonoscope, T6, upon leaving the examination room

Comparable periprocedural blood glucose variation

The analysis of between-subjects effects revealed no statistically differences in blood glucose levels among the groups. However, the within-subjects effects analysis illustrated a gradual increase over time: there was a significant rise from T0 to T5 (P = 0.002) and T5 to T7 (P < 0.001), with T7 showing a notable elevated level versus T0 (P < 0.001) (Fig. 2). No interaction effect was found between groups and different time points. Besides, the incidence of periprocedural glucose outside the range of 3.9 to 6.1 mmol/L was comparable, and none was < 2.8 mmol/L.

Analogous fluctuations in vital parameters

As demonstrated in Fig. 3, the hemodynamic changes among the groups were consistent. MAP gradually decreased at T0, T1, and T2, with significant differences noted compared to other time points (P < 0.05). The MAP at T3 was higher than that at T4 (P = 0.013) and T5 (P = 0.010), while at T6, the level increased above T5 (P = 0.009). No differences were found in the incidence of hypotension, bradycardia, hypoxia or the dose of norepinephrine consumed during sedation.

Discussion

Researches have demonstrated that it is safe to provide patients with carbohydrate-containing beverages before surgical procedures, with positive effects on certain clinical outcomes [17–21]. However, it has not been widely integrated into the routine clinical practice in China due to the deeply ingrained belief in fasting [22] and the dogma would not be thoroughly revised until credible data from vast clinical studies were available [23]. We designed the study to figure out the influences of pre-endoscopy carbohydrate loading on patients undergoing bidirectional endoscopy in China. The findings of our research indicate that patients who consumed 200 mL or 400 mL carbohydrate beverage 2 h prior to the procedure exhibited similar gastric emptying to those who took pure water or fasted overnight. Additionally, these patients reported a decreased discomfort.

Carbohydrate solutions are more frequently offered to patients in the operating theatre undergoing anesthesia than to those outside the theatre, such as patients scheduled for digestive endoscopy. However, it is crucial to extend oral carbohydrate research to cover these patients due to their unique circumstances and the potential risks. It must be primarily pointed out that our hospital generally schedules bidirectional endoscopy in the afternoon. Despite this, these patients followed the same fasting strategies as those underwent gastroscopy in morning. That is why, in our study, the fasting time for solids was over 20 h, and the no-drinking period was over 18 h in control group. Bowel preparation is a critical step for clear visualization but can inevitably cause internal environmental disturbances and physiological stress [24]. Some patients, driven by excessive concern for inadequate intestinal preparation, may arbitrarily prolong their fasting periods, worsening the adverse effects of traditional fasting protocols. Moreover, most patients undergoing digestive endoscopy are outpatients who do not have access to intravenous fluid and energy supplements. The absence of immediate medical care before hospitalization necessitates the development of safer and more comfortable pre-procedure conditions.

We offered a carbohydrate beverage particularly developed for fasting patients. The participants all responded that the product was acceptable. Ultrasonography as a real-time and non-invasive technique was utilized for its well intra and inter-rater reliability [25]. Perlas et al. systematically expounded the technology of ultrasound to quantitatively and qualitatively assess gastric contents, and recommended the RLD position for its enhanced sensitivity, given that the residual fluid tend to pool in the antrum due to gravity [15, 16, 26]. Align with previous studies [2, 27], we found that individuals adhering to the traditional fasting guidelines did not have a completely empty stomach before anesthesia induction. Patients with carbohydrate loading exhibited residual GV similar to those who took only water or fasted. It is generally accepted that cGV exceeding 1.5 mL/kg poses an aspiration risk during anesthesia induction [28]. In our study, no participants in either group were identified as a risk stomach. These findings indicate that ingesting up to 400mL of the oral carbohydrate beverage as well as pure water 2 h before bidirectional endoscopy does not elevate the risk during anesthesia.

VAS scores are widely used for measuring the intensity of pain. For this trial, they were utilized to assess targeted subjective comfort [29]. Before total knee arthroplasty, patients who ingested carbohydrates reported lower VAS scores for hunger, pain and anxiety [4]. In our study, a 400 mL of carbohydrate consumption was associated with reduced feeling of thirst, mouth dryness and hunger. A comparable alleviation in thirst and mouth dryness was reported with the consumption of 400 ml of water. Carbohydrates may stimulate the hypothalamic satiety center and promote leptin secretion that suppress appetite, which explained the effectiveness in relieving hunger compared to pure water. We also observed that the scores for nausea, vomiting, abdominal distention, abdominalgia and belching were comparable between groups, which may be attributed to the low baseline score. 400 mL oral carbohydrate is more recommended for patients with severe subjective discomfort before examination based on the findings that 200 mL carbohydrate loading has merely a minimal impact maybe for the inadequate amount of clear liquid.

It should be noted that the results of the study are based on the clinical practice in our hospital, as the fasting period is significantly longer than the recommended [30] and in other clinical centers [31, 32]. Although our interventions have demonstrated an advantage in terms of comfort, the intake of 400 mL carbohydrate solution did not improve patient comfort or satisfaction in minor surgery scheduled for the first session in the morning [22]. Therefore, a protracted period of fasting may be a significant contributory factor in the observed discrepancies. It is noteworthy that the findings are subject to the potential factor of bowel preparation as well. Overall, excessive fasting remains a common occurrence in clinical practice. If this standard were to be condensed to a 2 h timeframe and proven to be safe, it would at least represent a more favorable approach for patient compliance. Further studies are needed to determine the broad applicability of the results in a variety of clinical settings.

T. Yatabe et al. systemically demonstrated that it was convenient to improve insulin sensitivity and prevent perioperative hypothermia by consuming carbohydrate beverages [33]. During the elective craniotomy, patients who received preoperative oral carbohydrate supplementation exhibited superior glucose stability compared to those who adhered to a strict fasting protocol [34]. However, we were unable to reach a statistically significant conclusion about the periprocedural blood glucose levels among groups, potentially due to the variability in individual insulin secretory capabilities and the less pronounced stress response associated with digestive endoscopy compared to other surgical procedures.

Patients with poor managed diabetes and obesity were excluded due to concerns regarding their compromised metabolic status. The combined effect of traditional fasting, bowel preparation and carbohydrate loading may result in increased fluctuations in blood glucose levels for this group of patients. Furthermore, there is a case report of a patient with inadequately managed diabetes who developed postoperative gastric paralysis subsequent to preoperative carbohydrate loading [35]. Consequently, the findings of this study may not be applicable to patients with the aforementioned conditions.

After anesthesia induction, MAP showed a declining trend and gradually stabilized after the gastroscope was withdrawn. The blood pressure at the onset of the colonoscope was lower compared to the time of gastroscope removal, due to the interval period awaiting the sterilized colonoscope and the ongoing administration of medication. Once the colonoscope reached the ileocecal valve, the drug infusion was halted, resulting in an increase in the blood pressure as exiting the procedure room. No other significant differences in vital signs owing to oral rehydration were detected. Consequently, we cannot draw the conclusion that carbohydrates mitigate circulatory fluctuations. This may be attributed to the limited impact of carbohydrate load itself, which is insufficient to make up for the dehydration caused by laxatives and abstinence from fluid intake. After all, the intravascular half-life of crystalloid solutions is approximately 30 min. Hence, it is not surprising that oral carbohydrate solutions did not demonstrate a reduction in the need for vasoactive medications as well.

Several limitations exist in the study. First, the patients were not blinded to their allocation. Participants could easily discern whether they had received the intervention and the volume of the drink, as it was not feasible to mask this information. Additionally, it was challenging to ensure that the taste of the water and the carbohydrate solution were indistinguishable. Second, the unpredictable nature of clinical scheduling led to a longer interval between the intervention and anesthesia induction than initially anticipated 2 h, but this discrepancy aligns our results more closely with the real-world practice. Third, as it is difficult for outpatients to obtain blood samples, we were confined to assess electrolytes, insulin levels and inflammatory markers during the peri-examination period. Fourth, the restricted number of subjects limits the scope of the findings, and the single-center study restricts the broad applicability of the conclusions. Further researches are required in the form of multi-center, large-sample studies in order to validate our findings and investigate potential long-term outcomes.

Conclusions

In summary, both 200 mL and 400 mL doses of oral carbohydrate beverage can be safely administrated 2 h before elective painless bidirectional endoscopy, without a significant increase in gastric residual volume. Moreover, the 400mL volume more effectively enhances the subjective experience, and carbohydrate beverage rather than pure water better alleviates hunger.

Acknowledgements

The authors acknowledge the professionals who offered help.

Author contributions

L Guo contributed to data curation, formal analysis, investigation, writing — original draft. PF Liu contributed to data curation, formal analysis, validation, writing — review and editing. XY Jiang contributed to investigation, writing — original draft. ZR Shan contributed to formal analysis, software. R Wang contributed to conceptualization, project administration. ZP Wang contributed to methodology, funding acquisition, project administration, writing — review and editing. All authors read and approved the final manuscript.

Funding

This work was supported by the National Natural Science Foundation of China (82270059); the Jiangsu Natural Science Foundation (BK20221222); and the Jiangsu Provincial Medical Innovation Center (CXZX202211).

Data availability

The data that support the findings of this study are available from the corresponding author upon reasonable request.

Declarations

Ethics approval and consent to participate

This study was approved by the Ethics committee of the Affiliated Hospital of Xuzhou Medical University (XYFY2022-KL400-01). Informed written consent was attained from all the participants.

Competing interests

The authors declare no competing interests.

Publisher’s note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
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References

1. Zhang Z, Wang R, Duan B et al (2020) Effects of a preoperative carbohydrate-rich drink before ambulatory surgery: a randomized controlled, double-blinded study. Med Sci Monit 26. 10.12659/MSM.922837
2. Ajuzieogu O Amucheazi A Nwagha U Effect of routine preoperative fasting on residual gastric volume and acid in patients undergoing myomectomy Niger J Clin Pract 2016 19 816 10.4103/1119-3077.180049 27811457
Ajuzieogu O, Amucheazi A, Nwagha U et al (2016) Effect of routine preoperative fasting on residual gastric volume and acid in patients undergoing myomectomy. Niger J Clin Pract 19:816. 10.4103/1119-3077.18004927811457 10.4103/1119-3077.180049
3. Wang Y Tu Y Liu Z Effects of preoperative oral carbohydrate on cirrhotic patients under endoscopic therapy with anesthesia: a Randomized Controlled Trial Biomed Res Int 2021 2021 1 8 10.1155/2021/1405271 35465048
Wang Y, Tu Y, Liu Z et al (2021) Effects of preoperative oral carbohydrate on cirrhotic patients under endoscopic therapy with anesthesia: a Randomized Controlled Trial. Biomed Res Int 2021:1–8. 10.1155/2021/140527135465048 10.1155/2021/1405271
4. He Y Tang X Ning N Effects of preoperative oral Electrolyte-Carbohydrate Nutrition supplement on postoperative outcomes in Elderly patients receiving total knee arthroplasty: a prospective Randomized Controlled Trial Orthop Surg 2022 14 2535 2544 10.1111/os.13424 36040184
He Y, Tang X, Ning N et al (2022) Effects of preoperative oral electrolyte-carbohydrate nutrition supplement on postoperative outcomes in elderly patients receiving total knee arthroplasty: a prospective randomized controlled trial. Orthop Surg 14:2535–2544. 10.1111/os.1342436040184 10.1111/os.13424
5. Wang X Zhuang J Cheng J Effect of preoperative oral carbohydrates on insulin resistance in patients undergoing laparoscopic cholecystectomy: a randomized controlled trial Langenbecks Arch Surg 2024 409 77 10.1007/s00423-024-03268-1 38411704
Wang X, Zhuang J, Cheng J et al (2024) Effect of preoperative oral carbohydrates on insulin resistance in patients undergoing laparoscopic cholecystectomy: a randomized controlled trial. Langenbecks Arch Surg 409:77. 10.1007/s00423-024-03268-138411704 10.1007/s00423-024-03268-1
6. Wang ZG Wang Q Wang WJ Qin HL Randomized clinical trial to compare the effects of preoperative oral carbohydrate versus placebo on insulin resistance after colorectal surgery Br J Surg 2010 97 317 327 10.1002/bjs.6963 20101593
Wang ZG, Wang Q, Wang WJ, Qin HL (2010) Randomized clinical trial to compare the effects of preoperative oral carbohydrate versus placebo on insulin resistance after colorectal surgery. Br J Surg 97:317–327. 10.1002/bjs.696320101593 10.1002/bjs.6963
7. Chen X Li K Yang K Effects of preoperative oral single-dose and double-dose carbohydrates on insulin resistance in patients undergoing gastrectomy:a prospective randomized controlled trial Clin Nutr 2021 40 1596 1603 10.1016/j.clnu.2021.03.002 33752148
Chen X, Li K, Yang K et al (2021) Effects of preoperative oral single-dose and double-dose carbohydrates on insulin resistance in patients undergoing gastrectomy:a prospective randomized controlled trial. Clin Nutr 40:1596–1603. 10.1016/j.clnu.2021.03.00233752148 10.1016/j.clnu.2021.03.002
8. Ljungqvist O Scott M Fearon KC Enhanced recovery after surgery: a review JAMA Surg 2017 152 292 10.1001/jamasurg.2016.4952 28097305
Ljungqvist O, Scott M, Fearon KC (2017) Enhanced recovery after surgery: a review. JAMA Surg 152:292. 10.1001/jamasurg.2016.495228097305 10.1001/jamasurg.2016.4952
9. Gustafsson UO Scott MJ Hubner M Guidelines for Perioperative Care in Elective colorectal surgery: enhanced recovery after surgery (ERAS®) Society recommendations: 2018 World J Surg 2019 43 659 695 10.1007/s00268-018-4844-y 30426190
Gustafsson UO, Scott MJ, Hubner M et al (2019) Guidelines for Perioperative Care in Elective colorectal surgery: enhanced recovery after surgery (ERAS®) Society recommendations: 2018. World J Surg 43:659–695. 10.1007/s00268-018-4844-y30426190 10.1007/s00268-018-4844-y
10. Joshi GP Abdelmalak BB Weigel WA 2023 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting: carbohydrate-containing clear liquids with or without protein, chewing gum, and Pediatric Fasting Duration-A Modular Update of the 2017 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting Anesthesiology 2023 138 132 151 10.1097/ALN.0000000000004381 36629465
Joshi GP, Abdelmalak BB, Weigel WA et al (2023) 2023 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting: carbohydrate-containing clear liquids with or without protein, chewing gum, and Pediatric Fasting Duration-A Modular Update of the 2017 American Society of Anesthesiologists Practice Guidelines for Preoperative Fasting. Anesthesiology 138:132–151. 10.1097/ALN.000000000000438136629465 10.1097/ALN.0000000000004381
11. Wang Y, Huang Y, Chase RC et al (2023) Global burden of digestive diseases: a systematic analysis of the global burden of diseases study, 1990–2019. Gastroenterology. 10.1053/j.gastro.2023.05.050
12. Xin L Gao Y Cheng Z Utilization and quality assessment of digestive endoscopy in China: results from 5-year consecutive nationwide surveys Chin Med J (Engl) 2022 135 2003 2010 10.1097/CM9.0000000000002366 36070457
Xin L, Gao Y, Cheng Z et al (2022) Utilization and quality assessment of digestive endoscopy in China: results from 5-year consecutive nationwide surveys. Chin Med J (Engl) 135:2003–2010. 10.1097/CM9.000000000000236636070457 10.1097/CM9.0000000000002366
13. Song N Yang Y Zheng Z Effect of Esketamine added to Propofol Sedation on Desaturation and Hypotension in Bidirectional Endoscopy: a Randomized Clinical Trial JAMA Netw Open 2023 6 e2347886 10.1001/jamanetworkopen.2023.47886 38117498
Song N, Yang Y, Zheng Z et al (2023) Effect of esketamine added to propofol sedation on desaturation and hypotension in bidirectional endoscopy: a randomized clinical trial. JAMA Netw Open 6:e2347886. 10.1001/jamanetworkopen.2023.4788638117498 10.1001/jamanetworkopen.2023.47886
14. Amer MA Smith MD Herbison GP Network meta-analysis of the effect of preoperative carbohydrate loading on recovery after elective surgery Br J Surg 2017 104 187 197 10.1002/bjs.10408 28000931
Amer MA, Smith MD, Herbison GP et al (2017) Network meta-analysis of the effect of preoperative carbohydrate loading on recovery after elective surgery. Br J Surg 104:187–197. 10.1002/bjs.1040828000931 10.1002/bjs.10408
15. Perlas A Davis L Khan M Gastric Sonography in the Fasted Surgical patient: a prospective descriptive study AA 2011 113 93 97 10.1213/ANE.0b013e31821b98c0
Perlas A, Davis L, Khan M et al (2011) Gastric sonography in the fasted surgical patient: a prospective descriptive study. AA 113:93–97. 10.1213/ANE.0b013e31821b98c010.1213/ANE.0b013e31821b98c0
16. Perlas A, Mitsakakis N, Hanbidge A (2009) Ultrasound assessment of gastric content and volume. Anesthesiology 111
17. Rajan S Rahman A Kumar L Preoperative oral carbohydrate loading: effects on intraoperative blood glucose levels, post-operative nausea and vomiting, and intensive care unit stay J Anaesthesiol Clin Pharmacol 2021 37 622 10.4103/joacp.JOACP_382_19 35340955
Rajan S, Rahman A, Kumar L (2021) Preoperative oral carbohydrate loading: effects on intraoperative blood glucose levels, post-operative nausea and vomiting, and intensive care unit stay. J Anaesthesiol Clin Pharmacol 37:622. 10.4103/joacp.JOACP_382_1935340955 10.4103/joacp.JOACP_382_19
18. He Y Liu C Han Y The impact of oral carbohydrate-rich supplement taken two hours before caesarean delivery on maternal and neonatal perioperative outcomes -- a randomized clinical trial BMC Pregnancy Childbirth 2021 21 682 10.1186/s12884-021-04155-z 34620123
He Y, Liu C, Han Y et al (2021) The impact of oral carbohydrate-rich supplement taken two hours before caesarean delivery on maternal and neonatal perioperative outcomes -- a randomized clinical trial. BMC Pregnancy Childbirth 21:682. 10.1186/s12884-021-04155-z34620123 10.1186/s12884-021-04155-z
19. Suh S Hetzel E Alter-Troilo K The influence of preoperative carbohydrate loading on postoperative outcomes in bariatric surgery patients: a randomized, controlled trial Surg Obes Relat Dis 2021 17 1480 1488 10.1016/j.soard.2021.04.014 34016554
Suh S, Hetzel E, Alter-Troilo K et al (2021) The influence of preoperative carbohydrate loading on postoperative outcomes in bariatric surgery patients: a randomized, controlled trial. Surg Obes Relat Dis 17:1480–1488. 10.1016/j.soard.2021.04.01434016554 10.1016/j.soard.2021.04.014
20. Zhang T Xiong X Qin P Jin J The effect of preoperative oral carbohydrate on the incidence of complications in PACU after General Anesthesia: a prospective cohort study J PeriAnesthesia Nurs 2023 38 83 87 10.1016/j.jopan.2022.05.072
Zhang T, Xiong X, Qin P, Jin J (2023) The effect of preoperative oral carbohydrate on the incidence of complications in PACU after general anesthesia: a prospective cohort study. J PeriAnesthesia Nurs 38:83–87. 10.1016/j.jopan.2022.05.07210.1016/j.jopan.2022.05.072
21. Rizvanović N Nesek Adam V Kalajdžija M Effects of preoperative oral carbohydrate loading on Neutrophil/Lymphocyte ratio and postoperative complications following colorectal Cancer surgery: a randomized controlled study Eur Surg Res Europaische Chirurgische Forschung Recherches Chirurgicales Europeennes 2023 64 278 285 10.1159/000530124 36940663
Rizvanović N, Nesek Adam V, Kalajdžija M et al (2023) Effects of preoperative oral carbohydrate loading on Neutrophil/Lymphocyte ratio and postoperative complications following colorectal Cancer surgery: a randomized controlled study. Eur Surg Res Europaische Chirurgische Forschung Recherches Chirurgicales Europeennes 64:278–285. 10.1159/00053012436940663 10.1159/000530124
22. Doo AR Hwang H Ki M-J Effects of preoperative oral carbohydrate administration on patient well-being and satisfaction in thyroid surgery KJA 2018 71 394 400 10.4097/kja.d.18.27143
Doo AR, Hwang H, Ki M-J et al (2018) Effects of preoperative oral carbohydrate administration on patient well-being and satisfaction in thyroid surgery. KJA 71:394–400. 10.4097/kja.d.18.2714310.4097/kja.d.18.27143
23. Maltby JR Fasting from midnight–the history behind the dogma Best Pract Res Clin Anaesthesiol 2006 20 363 378 10.1016/j.bpa.2006.02.001 17080690
Maltby JR (2006) Fasting from midnight–the history behind the dogma. Best Pract Res Clin Anaesthesiol 20:363–378. 10.1016/j.bpa.2006.02.00117080690 10.1016/j.bpa.2006.02.001
24. Reumkens A van der Zander Q Winkens B Electrolyte disturbances after bowel preparation for colonoscopy: systematic review and meta-analysis Digest Endosc 2022 34 913 926 10.1111/den.14237
Reumkens A, van der Zander Q, Winkens B et al (2022) Electrolyte disturbances after bowel preparation for colonoscopy: systematic review and meta-analysis. Digest Endosc 34:913–926. 10.1111/den.1423710.1111/den.14237
25. Ruiz Ávila HA Espinosa Almanza CJ Fuentes Barreiro CY Inter-observer and intra-observer variability in ultrasound assessment of gastric content and volume in critically ill patients receiving enteral nutrition Ultrasound J 2023 15 14 10.1186/s13089-023-00312-x 36934375
Ruiz Ávila HA, Espinosa Almanza CJ, Fuentes Barreiro CY (2023) Inter-observer and intra-observer variability in ultrasound assessment of gastric content and volume in critically ill patients receiving enteral nutrition. Ultrasound J 15:14. 10.1186/s13089-023-00312-x36934375 10.1186/s13089-023-00312-x
26. Perlas A Mitsakakis N Liu L Validation of a mathematical model for ultrasound assessment of gastric volume by gastroscopic examination Anesth Analg 2013 116 357 363 10.1213/ANE.0b013e318274fc19 23302981
Perlas A, Mitsakakis N, Liu L et al (2013) Validation of a mathematical model for ultrasound assessment of gastric volume by gastroscopic examination. Anesth Analg 116:357–363. 10.1213/ANE.0b013e318274fc1923302981 10.1213/ANE.0b013e318274fc19
27. Cho E-A Huh J Lee SH Gastric Ultrasound assessing gastric emptying of Preoperative Carbohydrate drinks: a Randomized Controlled Noninferiority Study AA 2021 133 690 697 10.1213/ANE.0000000000005411
Cho E-A, Huh J, Lee SH et al (2021) Gastric Ultrasound assessing gastric emptying of preoperative carbohydrate drinks: a randomized controlled noninferiority study. AA 133:690–697. 10.1213/ANE.000000000000541110.1213/ANE.0000000000005411
28. Perlas A Van de Putte P Van Houwe P Chan VWS I-AIM framework for point-of-care gastric ultrasound Br J Anaesth 2016 116 7 11 10.1093/bja/aev113 25951832
Perlas A, Van de Putte P, Van Houwe P, Chan VWS (2016) I-AIM framework for point-of-care gastric ultrasound. Br J Anaesth 116:7–11. 10.1093/bja/aev11325951832 10.1093/bja/aev113
29. B G, S G, P E, et al (2015) Patient comfort during positron emission tomography/magnetic resonance and positron emission tomography/computed tomography examinations: subjective assessments with visual analog scales. Invest Radiol 50:. 10.1097/RLI.0000000000000177
30. (2017) Practice guidelines for Preoperative Fasting and the Use of Pharmacologic agents to reduce the risk of pulmonary aspiration: application to healthy patients undergoing elective procedures: an updated report by the American Society of Anesthesiologists Task Force on Preoperative Fasting and the Use of Pharmacologic agents to reduce the risk of pulmonary Aspiration*. Anesthesiology 126:376–393. 10.1097/ALN.0000000000001452
31. Greenfield SM Webster GJ Brar AS Assessment of residual gastric volume and thirst in patients who drink before gastroscopy Gut 1996 39 360 362 10.1136/gut.39.3.360 8949637
Greenfield SM, Webster GJ, Brar AS et al (1996) Assessment of residual gastric volume and thirst in patients who drink before gastroscopy. Gut 39:360–362. 10.1136/gut.39.3.3608949637 10.1136/gut.39.3.360
32. Li J, Liu Y, Lin H et al (2021) Feasibility study of shortening the no drinking time before gastroscopy to two hours. Dig Med Res 4. 10.21037/dmr-20-64
33. Yatabe T Tamura T Yokoyama M Effect of preoperative carbohydrate loading on the management of blood glucose and body temperature J Anesth 2014 28 148 151 10.1007/s00540-013-1740-3 24232414
Yatabe T, Tamura T, Yokoyama M (2014) Effect of preoperative carbohydrate loading on the management of blood glucose and body temperature. J Anesth 28:148–151. 10.1007/s00540-013-1740-324232414 10.1007/s00540-013-1740-3
34. Liu B Wang Y Liu S A randomized controlled study of preoperative oral carbohydrate loading versus fasting in patients undergoing elective craniotomy Clin Nutr 2019 38 2106 2112 10.1016/j.clnu.2018.11.008 30497695
Liu B, Wang Y, Liu S et al (2019) A randomized controlled study of preoperative oral carbohydrate loading versus fasting in patients undergoing elective craniotomy. Clin Nutr 38:2106–2112. 10.1016/j.clnu.2018.11.00830497695 10.1016/j.clnu.2018.11.008
35. How JA Siedel JH Shafer A Post-operative gastroparesis following carbohydrate loading in a diabetic patient Gynecologic Oncol Rep 2021 36 100714 10.1016/j.gore.2021.100714
How JA, Siedel JH, Shafer A (2021) Post-operative gastroparesis following carbohydrate loading in a diabetic patient. Gynecologic Oncol Rep 36:100714. 10.1016/j.gore.2021.10071410.1016/j.gore.2021.100714
