Study population
A comprehensive review of three hundred ninety-two participants who experienced LSG or laparoscopic distal gastrectomy (LDG) at the general surgery department of Chinese PLA General Hospital was retrospectively analyzed between January 2012 and June 2020. This included 100% of the primary LSG procedure within our single center. The study was approved by the ethical review committee of Chinese PLA General Hospital (S2021-247-02). As the study was retrospective, all patients signed a written informed consent for data analysis. It is not necessary to obtain formal consent due to the retrospective nature of the study. Our study inclusion criteria included: (1) body mass index (BMI) > 35 kg/m2, or BMI 27.5–34.9 kg/m2 with type 2 diabetes with poor glycemic control after lifestyle changes and medication, or with two or more other metabolic diseases; (2) gastric cancer was based on pathological diagnosis of the primary lesion, and with Billroth I reconstruction; (3) the patient with gastric cancer had performed gastric resection with negative margins and modified D2 lymphadenectomy; (4) vital organs such as the heart and lungs that could tolerate laparoscopic surgery; and (5) complete clinical and follow-up data. Exclusion criteria were as follows: (1) patients with severe preoperative hepatic or renal insufficiency, cardiopulmonary insufficiency, or other serious illnesses who could not receive standard treatment; and (2) patients with a previous history of psychiatric or gastrointestinal surgery.
After surgery, patients are transported to the recovery room for assessment of vital signs (temperature, heart rate, blood pressure, and oxygen saturation) and then transported to the general ward. In the ward, patients had a PONV score for nausea and vomiting. The PONV score was determined according to WHO criteria. Class I: no nausea or vomiting; Class II: mild nausea, abdominal discomfort, but no vomiting; Class III: significant vomiting, but no vomiting of stomach contents; Class IV: severe vomiting, with vomiting of stomach juices and other contents that are difficult to control without medication. Postoperative subjects who experienced nausea or vomiting received antiemetic medicines, including intravenous ondansetron 4 mg, or metoclopramide 10 mg, granisetron 0.1 mg, or tropisetron 0.5 mg, according to the physician’s decision taking into account the severity of PONV. Patients with postoperative pain were given tramadol 10 mg intramuscular (i.m.), parecoxib 40 mg (i.v.), flurbiprofen 50 mg (i.v.), and morphine 5 mg or 10 mg (i.m.), depending on the severity of the pain. Experienced and certified bariatric surgeons from the same surgical team performed all operations.
Patients are encouraged to walk around and drink water the day after surgery to speed up recovery rather than having a nasogastric tube routinely placed. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). Data was collected via a secure web based form housed at the Chinese PLA General Hospital and was provided to the primary investigators compliant database.
Inflammatory measures
Blood samples were collected within 72 h before surgery and 24 h after surgery. The NLR was calculated by dividing the absolute count of neutrophils by that of lymphocytes.
Anesthesia
Anesthesia was managed following a standardized clinical protocol. Anesthesia was induced with isoproterenol, remifentanil, sufentanil, succinylcholine, or atracurium, and the patient was then intubated. Anesthesia was maintained with infusions of propofol, remifentanil, and oxygen. Dexamethasone and ondansetron were routinely administered during the final stage of the operation according to PONV prophylaxis guidelines1. Isoflurane and volatile anesthetic gases were not used in the process.
Outcome measurements
Nausea is an upset in the stomach that can lead to vomiting. It is usually a prodromal vomiting symptom but may also occur alone, mainly characterized by apparent discomfort in the upper abdomen. Retching was defined as the attempt to bring up stomach contents through the mouth without actually doing so. Vomiting refers to the spillage of food or sputum from the stomach and out of the mouth11. The risk factors for postoperative nausea are almost identical to those for vomiting. Therefore, this study did not consider events of nausea or vomiting as separate outcomes. Both vomiting and retching were considered emetic events. This study focuses on the first 48 h after surgery.
Statistical analysis
Continuous variables were defined as the mean ± standard deviation or median (interquartile range); categorical variables were expressed as percentages. For continuous variables, the Kolmogorov‒Smirnov test was applied to test the normality of distribution, t test, or the Mann‒Whitney U test; a one-way ANOVA model was used to compare. For categorical variables, the chi-square test was used. The Spearman rank test was used to test correlations. A Receiver operating characteristic (ROC) curve analysis was performed to verify the diagnostic accuracy of the NLR level in the presence and severity of PONV. Multivariate and ordinal logistic regression analysis was used to assess the independent predictors and severity of PONV, respectively. A propensity score matching (PSM) was done using a multivariable logistic regression model based on: age, sex, body mass index, smoking, hospital stay, type 2 diabetes mellitus (T2DM), gastroesophageal reflux disease (GERD), PONV history, motion history, neutrophil-to-lymphocyte (NLR), monocyte-to-lymphocyte (MLR), laparoscopic sleeve gastrectomy (LSG), laparoscopic distal gastrectomy (LDG), patient-controlled intravenous analgesia (PCIA), opioid, amidoamine, and ondansetron. Pairs of 392 patients were derived using 1:1 greedy nearest neighbor matching within a PS score of 0.2. After propensity score matching (PSM)12, the balance of measured variables between groups was analyzed using a paired t test for continuous measures and the McNemar test for categorical variables. Statistical analyses were performed using SPSS 26.0. Statistical significance was defined as a 2-tailed p < 0.05.
Ethics approval and consent to participate
The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved. The study was conducted in accordance with the Declaration of Helsinki (as revised in 2013). The study was approved by the ethical review committee of Chinese PLA General Hospital (S2021-247-02).