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Clinical research

The effect of active gas aspiration to reduce pain after laparoscopic sleeve gastrectomy for morbid obesity: a randomized controlled study

Hasan Erdem
Mehmet Gençtürk
Süleyman Çetinkünar
Abdullah Şişik
Selim Sözen

Istanbul Obesity Surgery (IOC), Kurtköy Ersoy Hospital, Istanbul, Turkey
Department of General Surgery, Adana City Training and Research Hospital, Adana, Turkey
Department of General Surgery, University of Health Sciences, Ümraniye Education and Research Hospital, Istanbul, Turkey
Sözen Surgery Clinic, Istanbul, Turkey
Arch Med Sci Civil Dis 2021; 6: e109–e116
Online publish date: 2021/09/20
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Laparoscopic sleeve gastrectomy (LSG) has been one of the most common procedures worldwide in bariatric surgery since 2014 [1–3]. During laparoscopic surgery, it is imperative to create a pneumoperitoneum in order to view the abdomen and work comfortably [4]. The most commonly used gas in laparoscopy is carbon dioxide (CO2) [5]. The reason for this is that CO2 is not flammable, it is colourless, and it has low cost [6]. However, visceral pain and shoulder pain after laparoscopic surgery are mostly caused by CO2 delivered to the abdominal cavity. Pneumoperitoneum forms as a result of CO2 insufflation; increased intraabdominal pressure leads to diaphragmatic irritation, stretching of the peritoneum, stretching of the diaphragmatic muscle fibres, and as a result, abdominal and shoulder pain develop in the patient [7–9]. Moreover, high levels of abdominal distension are associated with high levels of postoperative pain during the recovery period, delaying recovery-room discharge [10].
In this study, we tried to examine the factors affecting postoperative pain and the benefit of active gas aspiration after laparoscopic sleeve gastrectomy.

Material and methods

After approval of the institutional ethical committee (Adana City Training and Research Hospital, decision number 921, 17/06/2020), informed consent was taken from each patient who took part in the study. All patients were informed according to their individual education levels in terms of anaesthesia, surgical method, complications, and postoperative process. The randomized clinical trial was conducted between November 2019 and January 2020, and it included 150 patients with a body mass index (BMI) of 40 to 60 kg/m², 18 years of age or older, and scheduled for laparoscopic sleeve gastrectomy. Exclusion criteria were an American Society of Anesthesiologists score of 3 or 4, a history of drug dependence/abuse, history of opioid intake or chronic pain disorder, coagulopathy, infections, previous abdominal surgery, and cases with surgical complications. All patients were given a liquid diet before the operation. In addition, the night before the operation, all patients were administered low-molecular-weight heparin (Enoxaparine, Sanofi, Paris, France) subcutaneously for deep venous thrombosis prophylaxis and were dressed with pneumatic compression stockings. All patients underwent upper GIS endoscopy under sedation, to evaluate anatomical anomalies and gastric mucosal pathologies before surgery. All surgeries were completed laparoscopically. Patients were randomly assigned using the envelope method to either the active gas reduction group (Group 1) or the control group (Group 2) just before the operation. The anaesthesia technique was standardized in all patients.

Anaesthesia protocol

The patients were premedicated according to their ideal weight with demizolam (0.5–0.1 mg/kg). Following pre-oxygenation, anaesthesia was induced with fentanil (1.5 µg/kg), propofol (3 mg/kg), and rocuronium (0.5–0.8 mg/kg), and orotracheal intubation was performed 2 min later. Ventilation was provided with 50% oxygen/air. 5 cm/H2O positive end-expiratory pressure (PEEP) was opened in pressure control mode, ventilator parameters were adjusted so that end tidal CO2 was 35–45 mm Hg. Anaesthesia was maintained with remifentanyl (0.1–0.5 µg/kg/min) and sevofluarane (1–1.5%) as an infusion. Reversal of neuromuscular blockade was achieved using sugammadex (2–8 mg/kg) followed by tracheal extubation.

Surgical technique

All LSG procedures were performed by the same surgeon; the operations were performed in the Lloyd Davies position, and a 38-F bougie was standard. The gastrectomy removed approximately 80% of the stomach, with a remnant stomach capacity of < 100 ml, and none of the cases required conversion to open surgery. All operations followed the same procedural guidelines. Briefly, the operation was started by placing 5 trocars traditionally. The gastrocolic omentum was divided, starting 4 cm proximal to the pylorus up to the angle of His. Dissection was performed up to the left crus of the hiatus, and all attachments were released to completely mobilize the fundus. The gastric pouch was created by using a linear stapler, with 2 sequential 4.8/60 mm green load firings for the antrum, followed by 3 sequential 4.8/60 mm purple cartridges for the remaining gastric corpus and fundus. The resected stomach was extracted through the 15 mm port-site [11]. After the bleeding control, a Jackson Pratt drain was placed in the lobby. The intra-abdominal gas pressure was set at a level of 17 mm Hg and monitored during the operation. After completion of the operative procedures and before the patients were placed in the supine position. CO2 insufflation ended. In patients with active gas aspiration (Group 1), the liver, subdiaphragmatic areas on the spleen, lower pelvic area, and Douglas pouch were aspirated with direct camera vision before the valves of the trocars were opened and removed. Aspiration was performed with a flexible feeding cannula that was inserted through the most lateral Accessory port. Then, the valves of all trocars were opened and the trocars were removed. In the control group (Group 2), after the CO2 insufflation was terminated, the trocars were removed after the gas was evacuated by opening the valves of the trocars. All patients were given a single use of antibiotic prophylaxis (ceftriaxone, 1000 mg) intravenously, and diclofenac sodium (75 mg) was administered to all patients postoperatively. Mobilization and respiratory physiotherapy were started 4 h after the operation. A liquid diet was started following flatus discharge from the anus in the postoperative period. The patients who tolerated oral intake and had no morbidity development were discharged from the hospital on the third postoperative day. The demographic data, body mass index, educational status, operation time, insufflated CO2 volume during the operation, hospitalization period, and intraabdominal pressure were recorded. Postoperative shoulder and abdominal pain assessment was performed using an 11-point numerical pain intensity scale (NPIS), in which a rating of 0 indicated “no pain” and a rating of 10 indicated the “worst imaginable pain”. Following surgery, pain assessments were measured by the patients’ bed at the end of the 1st h, the 24th h, and the 3rd day.

Statistical analysis

All statistical analyses in the study were done using SPSS 25.0 software (IBM SPSS, Chicago, IL, USA). Descriptive data are given as numbers and percentages. In terms of categorical variables, comparisons between groups were made using Pearson’s 2 test and Fisher’s exact test. Whether continuous variables were suitable for normal distribution was confirmed by the Kolmogorov-Smirnov test. The differences between the groups in terms of continuous variables were made with Student’s t-test. The relationship between continuous variables was examined by correlation analysis. The results were evaluated within the 95% confidence interval, and p < 0.05 values were considered significant.


A total of 150 patients who were treated for obesity in our clinic were included in the study. The patients with coagulopathy and bleeding (1), infections (1), previous abdominal surgery (1), a history of drug dependence/abuse (1), or a history of opioid intake or chronic pain disorder (1) were excluded from the study. Finally, 143 patients (33 men and 110 women) were included in the statistical analysis. The mean age was 35 years (range: 19–64 years). Group 1 included 69 patients, and Group 2 included 74 patients. Both groups had similar demographic characteristics (Table I). NPIS scores at the 24th h were significantly lower in Group 1 (p < 0.001) (Table II). However, there were no significant differences in terms of the NPIS scores after the 1st h and the 3rd day. No differences were found in the operation time (p > 0.05) (Table I). When evaluated in terms of gender, education level, smoking, and BMI, there was no difference in terms of gender and BMI between Group 1 and Group 2 patients. The rate of smoking in Group 1 patients was lower than in Group 2 patients. The difference is statistically significant (p < 0.001) (Table III). The educational level was found to be lower in the passive group (p = 0.023). In Group 2 the pain score observed in the 1st h was lower in patients with a body mass index greater than 40 (p = 0.046) (Table IV). In Group 1 no difference was found between pain scores according to body mass index (Tables IV, V). When Group 1 patients were evaluated in terms of smoking, educational level, and BMI pain scores, there was no difference between the groups. We observed that age and operative time are independent factors associated with postoperative analgesic requirements. According to the correlation analysis of age and operation time in Group 1 (Table VI, VII) and Group 2, the duration of operation and the NPIS scores at the 24th h were found to be correlated in Group 1. There were no complications; hence, all patients were discharged from the hospital on the 4th postoperative day.


Pain following a minimally invasive procedure is an important problem for the patient. Pain after minimally invasive surgery (MIS) affects quality of life and causes delayed discharge or late return to normal activities [12]. Pain after MIS can be divided into incisional pain, shoulder-type pain (STP), and/or upper abdominal pain. After laparoscopic surgery, upper abdominal pain and shoulder pain may be temporary or last for about 3 days [13]. Abdominal trauma caused by the entry of trocars into the abdominal wall causes somatic pain, and intraabdominal interventions cause visceral origin pain. Other factors associated with pain are temperature and type of insufflated gas, intra-abdominal pH, presence of intraabdominal residual gas, abdominal distension, and irritation of the peritoneum [8, 14]. In addition, the conversion of CO2 in the abdomen to carbonic acid on peritoneal surfaces causes pain [15–17]. In a study, 62% of patients had shoulder pain at the 12th h after laparoscopic surgery; this rate decreased to 9% on the 10th postoperative day, and the frequency of pain decreased as the gas pressure given for pneumoperitoneum decreased. It was found that the frequency of pain was significantly higher at the postoperative 12th, 24th, and 48th h for surgical operations longer than 45 min [18]. In our study, despite the 17 mm Hg gas pressure given, the mean operation time in both groups was 38 min. In a prospective randomized study on laparoscopic surgery and pain, it was observed that the pain scores peaked at 12–24 h postoperatively. It was reported that the pain was frequent and severe after the mobilization of the patient [19]. This has been linked to the fact that mobilization increases traction on the peritoneal reflections of the heavy viscera, which then lose suction support for their weight owing to the creation of peritoneal spaces by carbon dioxide [20]. In our study, the fact that the pain did not differ on the day of surgery (day 0) may have resulted in a similar perception of the severity of the pain because the effect of anaesthesia was not fully exceeded in both groups, and strong analgesia was used. On the other hand, it may have been more difficult to tolerate pain because the effect of anaesthesia on the first day after surgery, which is the day when the severity of pain is perceived, had passed. However, in Group 1, pain scores at the the 24th h were better than in the control group. Again, on the 3rd day, the decrease in the severity of post-operative pain may have caused the pain to be perceived at the same severity in both groups.
Although nicotine has an analgesic effect, the incidence and severity of chronic pain is higher in smokers than in non-smokers. In smokers, acute pain is more intense in the postoperative period [21]. It has been observed that smoking increases the perception of pain and that more postoperative opioid use is needed regardless of the amount of smoking. Weingarten et al. reported that although current tobacco smokers used more opioid analgesics in the first 48 h after surgery than non-smokers, tobacco use alone was not associated with the need for postoperative opioid after age and gender adjustment [22]. In our study, when the groups were evaluated within themselves, the effect of smoking on postoperative pain was not observed alone (Tables IV, V).
We observed that age and operative time were independent factors associated with postoperative analgesic requirements. Another independent factor associated with the postoperative analgesic requirement was the amount of intraoperative remifentanil. The findings of the study showed that prolonged surgery might cause increased use of remifentanil and that this might cause opioid tolerance or opioid-induced hyperalgesia [23, 24]. According to our findings the pain level and duration of surgery were associated with active gas aspiration patients (Table VI).
In the literature, the effect of BMI on postoperative pain is controversial. High body mass index is associated with postoperative complications and postoperative pain [25]. However, high BMI levels did not appear to be associated with increased postoperative pain in patients undergoing laparoscopic gastric bypass [26]. In our study, no effect of BMI on pain scores was observed in the actively aspirated group. In the control group, it was adversely effective, inconsistent with the literature on pain at the 1st h. We attribute this to the strong analgesia given immediately after surgery.
The results of studies evaluating the relationship between educational status and postoperative pain are different. Just as there are studies that say it has no correlation [27, 28], there are also those stating that a lower education level is associated with a higher incidence of painful conditions [29]. In our study, conversely, in the control group, more pain was found in the trained patients at the 1st h.
In the literature, there are studies indicating that active aspiration decreases the residual CO2 volume and decreases the frequency of pain and shoulder pain in the postoperative period after abdominal operations with minimally invasive surgery [30, 31]. In our study, pain scores at the 24th h were significantly lower in the group with active gas discharge than in the control group. Nursal et al. [32] studied the effects of a subdiaphragmatic gas drain, which is expected to decrease the residual gas volume on postoperative pain, nausea, and vomiting after laparoscopic cholecystectomy (LC) in a prospective randomized study; they observed that the subdiaphragmatic drain effectively reduced the incidence and amount of subdiaphragmatic gas bubbles. However, they stated that the subdiaphragmatic drain used in gas discharge only provided minor benefits for postoperative pain, nausea, and vomiting after laparoscopic cholecystectomy, and this effect was probably clinically insignificant [32]. In our study, although drains were used in both groups, we observed that there was no benefit regarding pain in the postoperative period. In fact, in some of our patients, the drain itself was a source of pain.
Many studies have been conducted to decrease the level of pain after laparoscopic sleeve gastrectomy. In recent years, different methods such as transversus abdominis plane block have been tried to reduce pain after sleeve gastrectomy [33, 34]. Transversus abdominis block (TAB) is a relatively new regional anaesthetic technique in which the cutaneous branches of the L1-3 nerve roots, the T7-12 intercostal nerves, and the ilioinguinal and iliohypogastric nerves are blocked between the internal oblique and tranvsersus abdominis muscles [35]. The procedure is usually done by experienced anaesthesiologists using 18–22-gauge needles. Despite its successful results, the amount of local anaesthesia to be applied in obese patients is still controversial [36, 37]. In all these studies, attempts to control patients’ pain involved invasive techniques and medical methods. Each working group argues that their methods are successful in reducing the level of postoperative pain. However, the advantage of our method over all these methods is that it is a simple and fast method to apply during surgery.
In conclusion, although the volume aspirated in our study was not calculated and some of our results differed from the literature, we found that the pain at the postoperative 24th h was significantly lower in the aspirated patient group. The active aspiration technique reduced the volume of residual CO2 in the intraperitoneal cavity at the end of laparoscopic sleeve gastrectomy. This technique was effective in decreasing the level of abdominal distension and pain experienced postoperatively. Active aspiration of the remaining gas just before the removal of the trocars is a simple procedure, and we recommend it because it reduces pain and contributes to a more comfortable hospital stay.

Conflict of interest

The authors declare no conflict of interest.
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