Since the first use in the field of surgical practice, laparoscopic surgery has revolutionized the surgery that is defined by the following advantages: low surgical trauma, short hospital stay, rapid recovery and good cosmetic appearance.(1) The main principle of laparoscopic surgery is the creation of pneumoperitoneum (inflation of carbon dioxide into the abdominal cavity) to provide adequate visualization and space for the surgeon to safely and effectively proceed with the surgery.(2) The normal intraabdominal pressure accepted as the standard for a good surgical condition is 12-15 mmHg. This standard pressure comes with drawbacks though.(3) Significant physiological changes have been demonstrated with elevated IAP such as reduction in cardiac output, decrease in pulmonary compliance, higher airway pressures, higher systemic vascular resistance, and impaired venous return.(4) Such patients who already have compromised cardiopulmonary reserve may be especially affected by these changes.(5) Also, higher insufflation pressures are correlated to higher postoperative pain levels, especially shoulder tip pain from irritation of the diaphragm and CO2 retention, and increased incidence of postoperative nausea and vomiting (PONV).(6, 7)To address these concerns, the idea of using low pressure pneumoperitoneum has been growing in popularity in recent years.(8) To reduce the negative physiological effects of pneumoperitoneum without compromising the feasibility and safety of surgery, low intra-abdominal pressure, usually defined as pressures below 10 mmHg, has been suggested.(9) In line with the philosophy of 'small is beautiful', the Enhanced Recovery After Surgery (ERAS) guidelines stress the need for a perioperative pathway tailored to the individual, but have not yet agreed upon a specific pressure target.(10) There is an increasing number of evidence that supports the benefits of low IAP strategies.(11) The results of these studies are encouraging, however, there is significant variation in clinical practice with regard to the use of low IAP strategies.(12) Some surgeons remain with standard pressures because they fear inadequate visualization, long operating times and/or compromised surgical results. Further research is needed regarding the applicability of low IAP in other surgeries and patient groups.(13) Hence the present study was designed to compare the effect of low intra-abdominal pressure (8-10 mmHg) with the effect of standard intra-abdominal pressure (12-15 mmHg) on the Peri-operative outcome of patients undergoing elective laparoscopic surgeries at Abbottabad International Medical College.

Study Design and Setting The present comparative clinical study was carried out in the Department of Surgery, Abbottabad International Medical College, for one year period from January 2023 to December 2023. The study was a prospective, randomized, controlled, parallel-group clinical trial to assess the effect of low intra-abdominal pressure versus standard intra-abdominal pressure on perioperative outcomes in patients undergoing elective laparoscopic surgery. Study Population 150 adult patients undergoing elective laparoscopy were enrolled in the study. The patients were randomized into two groups: low IAP group (n=75) who had pneumoperitoneum of 8 mmHg to 10 mmHg and standard IAP group (n=75) who had pneumoperitoneum of 12 mmHg to 15 mmHg. Inclusion Criteria Adult patients between the ages of 18–70, of both sexes. Elective procedures performed laparoscopically such as the cholecystectomy, appendectomy, inguinal herniorrhaphy, or diagnostic laparoscopy. The ASA physical status classification (I-III) is a measure of the physical status of a patient.ASA Physical Status classification (I-III): It is a measure of the physical status of a patient. Patients who gave informed consent in writing to participate in the study. Exclusion Criteria American Society of Anesthesiologists (ASA) status IV or higher Patients with severe cardiopulmonary disease which is incompatible with pneumoperitoneum Patients who are not able to have laparoscopic procedures. Pregnant women A history of prior abdominal surgery that would be a hindrance to laparoscopy Coagulopathy or bleeding disorders patients Patients who are on chronic anticoagulant therapy who might not be able to temporarily discontinue the medication. People who declined to give informed consent Ethical Considerations The Institutional Ethical Review Committee (IERC) of Abbottabad International Medical College (AIMC) provided approval before patient enrolment for this study. The study was performed in the compliance with the principles of the Declaration of Helsinki and Good Clinical Practice guidelines. All participants gave written informed consent after being informed in detail about the study procedures, potential risks and benefits. The surgical and anesthetic approach. Surgical/Anesthetic Protocol One of the aim of the present study was to ensure uniformities in surgical technique as all surgical procedures were to be done by experienced consultant surgeons with at least 5 years of experience in laparoscopy. All patients received the same anaesthetic procedure. Propofol 2 mg/kg was used to induce general anesthesia, and sevoflurane in a gas mixture of oxygen and air was used to maintain general anesthesia. Atracurium was used to induce neuromuscular blockade, and was monitored by train-of-four stimulation. Mechanical ventilation was adjusted to keep the $Pco_2$ and $Pco_2$ normal. The creation of pneumoperitoneum was either by insufflating carbon dioxide via Veress needle or open Hasson technique. The insufflator pressure was maintained at 8-10mmHg in the low IAP group and 12-15mmHg in the standard IAP group. Maintains pressure during procedure, adjusts as clinically indicated. All surgical durations, total insufflation time and intraoperative complications were carefully documented. Outcome Measures Primary Outcomes Postoperative Pain Assessment: Pain assessment was carried out with the Visual Analogue Scale (VAS) which is a 10-cm linear scale from 0 (no pain) to 10 (the worst pain that can be imagined). Trained and blinded-to-group nursing staff recorded pain scores at 6, 12 and 24 hours after surgery. Analgesic Requirements: Total dose of parenteral tramadol used in the first 24 hours after surgery was noted. Standardized rescue analgesia protocols were used in all patients. Secondary Outcomes Documentation of complications: Complications were recorded, and classified according to the Clavien–Dindo classification (I – any deviation from the normal postoperative course without the use of pharmacological treatment or surgical, endoscopic and radiological intervention; II – surgical or endoscopic or radiological treatment was required; III – death of the patient; IV – major organ failure or dysfunction not specifically related to surgery). Length of Hospital Stay: Days from surgery to discharge. Intraoperative Parameters: Operative duration, insufflation time, intraoperative complication rate, conversion to open surgery rate and estimated blood loss were recorded. Statistical Analysis Data was collected and analyzed in SPSS version 26.0 (IBM Corp., Armonk, NY, USA). Data of continuous variables were presented as mean ± SD, and analyzed using the independent samples t-test or Mann–Whitney U test. The categorical variables were presented in counts and percentages and compared using the chi-square test or Fisher's exact test. A p value of less than 0.05 was used as the cut-off for statistical significance.

This study included 75 patients in the low IAP group (8–10 mmHg) and 75 patients in the standard IAP group (12–15 mmHg). No patients were lost to follow-up and all patients finished the study protocol. Table 1 shows the baseline demographic and clinical features of both groups.

The two groups were well balanced at baseline, and there were no statistically significant differences between age, gender distribution, body mass index, ASA grade and type of surgical procedure (p>0.05, for all comparisons, respectively).

Table 1: Baseline Demographic and Clinical Characteristics

The intraoperative parameters are summarized in Table 2. The mean operative time was 58.4 ± 18.2 minutes for low IAP group and 56.9 ± 17.5 minutes for standard IAP group without any statistically significant difference (p = 0.605). Insufflation time, intraoperative complication rate, conversion to open surgery rate and estimated blood loss were also not statistically different between the groups. These results validate that low IAP did not adversely affect surgical procedure or risk of surgery.

Table 2: Intraoperative Parameters

The postoperative results are shown in Table 3. Patients with low IAP had significantly lower pain scores at all-time points measured. The low IAP group had an average VAS score of 3.2 ± 1.4 at 6 hours after surgery, while the standard IAP group had an average VAS score of 5.6 ± 1.8 (p<0.001). This difference persisted at 12 hours (2.5 ± 1.2 vs 4.8 ± 1.6, p<0.001) and 24 hours (1.8 ± 0.9 vs 3.5 ± 1.3, p<0.001). The dosage of tramadol was also significantly reduced in the low IAP group (42.5 ± 18.6 mg) when compared with the standard IAP group (78.4 ± 22.3 mg) (p<0.001). There were more postoperative complications in the standard IAP group (15 patients, 20.0%) than in the low IAP group (7 patients, 9.3%) (p=0.041). The mean hospital stay of the low IAP group (1.5 ± 0.5 days) was significantly shorter than the mean hospital stay of the standard IAP group (2.4 ± 0.8 days) (p < 0.001).

Table 3: Postoperative Outcomes

The postoperative results are shown in Table 3. Patients with low IAP had significantly lower pain scores at all-time points measured. The low IAP group had an average VAS score of 3.2 ± 1.4 at 6 hours after surgery, while the standard IAP group had an average VAS score of 5.6 ± 1.8 (p<0.001). This difference persisted at 12 hours (2.5 ± 1.2 vs 4.8 ± 1.6, p<0.001) and 24 hours (1.8 ± 0.9 vs 3.5 ± 1.3, p<0.001). The dosage of tramadol was also significantly reduced in the low IAP group (42.5 ± 18.6 mg) when compared with the standard IAP group (78.4 ± 22.3 mg) (p<0.001). There were more postoperative complications in the standard IAP group (15 patients, 20.0%) than in the low IAP group (7 patients, 9.3%) (p=0.041). The mean hospital stay of the low IAP group (1.5 ± 0.5 days) was significantly shorter than the mean hospital stay of the standard IAP group (2.4 ± 0.8 days) (p < 0.001).

Table 4: Distribution of Postoperative Complications (Clavien–Dindo Classification)

As indicated in Table 4, the Clavien–Dindo classification shows the distribution of postoperative complications. Most of the complications were Grade I and Grade II – wound infections, urinary retention and postoperative nausea, which required antiemetic therapy. Two of the patients treated in the standard IAP group had Grade III complications, which required interventional drainage of intra-abdominal collections. No complications of Grade IV and V were observed in both groups. No difference in overall complication rates was seen by grade between the low and high IAP groups.

The results of this comparative study show that, during the laparoscopic procedure, if the use of low intra-abdominal pressure (8–10 mmHg) is compared with standard pressure (12–15 mmHg), the use of low pressure is associated with significantly improved postoperative outcomes without compromising the safety and feasibility of the procedure during the operation. The results are consistent with and confirm the increasing evidence for the use of low IAP strategies in the standard use of laparoscopy. The most important result of this study was that the low IAP group had significantly lower scores of pain at all-time points after surgery. The mean VAS score at 6 hours after surgery was 3.2 in the low IAP group versus 5.6 in the standard IAP group, which was more than 40% less.(14) This difference was clinically and statistically significant at 12 and 24 hours. The decrease in postoperative pain may be related with the following mechanisms. Reduced insufflation pressures lead to less stretching of the lining of the peritoneum and irritation to the diaphragm, both of which play a major role in postoperative pain, especially in the area of the shoulder tip.(15) Also, lower pressures could decrease the amount of abdominal cavity residual carbon dioxide that is known to irritate the diaphragm and cause referred pain.(16) The results of these studies agree with a meta-analysis of randomized trials, which reported a mean difference of −0.68 in pain scores in favor of low IAP, and a clinical trial that compared 8 mmHg and 12 mmHg pneumoperitoneum, which showed significantly less postoperative pain with low IAP.(17) The difference in the first 24 hours between the two groups for the analgesic requirement (42.5 mg for the low IAP group versus 78.4 mg for the high IAP group) is a clinically significant difference. Pain medications used will be minimized which helps to reduce opioid side effects like nausea, vomiting and respiratory depression as well as helps improve the patient's mobilization and recovery.(18) This finding is similar to a prospective cohort study of laparoscopic colorectal surgery where lower IAP was associated with less analgesic use (p ≤ 0.028). This also has an economic impact of the reduced need for postoperative analgesia, which may result in cost savings for the health system as there is less reliance on the health system for medication administration and a reduced cost for the post-operative analgesic in the pharmacy. Low IAP group had significantly lower complication rate of 9.3% vs 20.0% in standard IAP group (p=0.041). Most complications (Clavien–Dindo Grade I and II) were minor such as wound infection, urinary retention, and postoperative nausea.(19) This diminished complication rate can be explained by a number of factors. Hemodynamic stability and pulmonary mechanics are preserved better with lower IAP, so there is a possibility to decrease the incidence of cardiovascular and respiratory complications in the postoperative period.(4) Also, better postoperative pain control could allow for earlier mobilization, which would help to limit postoperative thromboembolic complications and aid in gastrointestinal recovery.(20) The length of hospital stay was significantly less in the low IAP group (1.5 ± 0.5 days) than in the standard IAP group (2.4 ± 0.8 days) (p<0.001). The finding holds significant implications for patient care and health care resource utilization. A shorter stay results in lower health care costs, more beds available, and better patient satisfaction. The shortened hospital stay is probably a combination of decreased pain and fewer complications, as well as less need for pain medication, resulting in earlier discharge. (21) The results are similar to the Meta analysis mean change of −0.29 days in hospital stay when using low IAP.(22) Importantly, low IAP did not adversely affect the safety or surgical outcomes during surgery. The duration of the operation, duration of insufflation, occurrence of intraoperative complications, conversion to open surgery and estimated blood loss were similar for the two groups.(23) This discovery potentially answers a surgeons' worry that lower insufflations pressures would lead to poorer surgical visualization, longer operative time or higher technical difficulty.(24) There was no significant difference between these parameters indicates that low IAP can provide adequate visualization and working space with good surgical conditions, if the surgical expertise is adequate and a neuromuscular blockade is utilized to optimize surgical conditions.(25) Comparing low IAP to high IAP in the field of laparoscopic colorectal surgery also revealed that low IAP is a safe and feasible strategy and non-inferior to standard IAP.(26) The effects of pneumoperitoneum on the physiology help explain the beneficial effects of low IAP. Significant changes in the cardiovascular and respiratory physiology have been reported after the use of standard-pressure pneumoperitoneum (12–15 mmHg).(27,28) Low pressure pneumoperitoneum (about 10 mmHg) has been found to be beneficial in reducing the negative effects on pulmonary mechanics, maintaining hemodynamic stability and aiding in a better postoperative recovery.(29, 30) All these physiological effects lead to better clinical results that translate into decreased postoperative pain, faster recovery and decreased postoperative complications. The results of this study have several clinical implications. First, they present convincing evidence for the routine application of low IAP in elective laparoscopic surgery, especially without contraindications. Second, they conclude that the use of individualized pressure management, adjusting the IAP to the patient's features, surgery needs and the surgeon's experience, could make outcomes even better. Third, the benefits of low IAP are in keeping with the principles of Enhanced Recovery after Surgery (ERAS) protocols that focus on reducing stresses of surgery, optimizing pain management, and promoting early recovery. Low IAP strategies for incorporation into ERAS pathways are logical and evidence-based and can lead to better perioperative care.

The lower intra-abdominal pressure (8–10 mmHg) during laparoscopic surgery has been shown to result in lower post-operative pain in terms of lower Visual Analogue Scale scores 6, 12 and 24 hours after surgery compared to higher pressure (12–15 mmHg). Laparoscopic surgery patients with low IAPs need a lot less postoperative analgesic, hence there is a lesser chance of experiencing side effects of opioids and also recovery is quick. Low IAP is correlated with significant reduction of complications after surgery, especially mild ones (Clavien-Dindo Grade I & II).The use of low IAPs can reduce the length of hospital stays without increasing intraoperative risks of complications, which was demonstrated by similar operative duration, insufflation time and incidence of intraoperative complications between low and standard pressure groups. Laparoscopic surgery with low intra-abdominal pressure is safe, effective and evidence based and should be adopted as a routine procedure in clinical setting, especially in Enhanced Recovery after Surgery.

Limitations

Finally, the study has several limitations, such as the single-center design, which may decrease the generalizability of results, and the variability of the laparoscopic procedures performed, which may result in outcome variability. The number of patients included (150) is sufficient for the primary outcomes but not enough to detect differences in rare complications. The Visual Analogue Scale is purely subjective and can be affected by patient factors in pain assessment. It is unknown whether low IAP affects long-term outcomes of chronic pain, incisional hernia, and quality of life. Furthermore, the parameters of the respiratory system and hemodynamic stability were not specifically assessed, and surgeon blinding might have resulted in performance bias, which was minimized by using standardized procedures.

Recommendations

The aim of low intra-abdominal pressure (8-10 mmHg) during elective laparoscopic surgery is to minimize postoperative pain, complications and recovery time, without compromising safety. IAP should be tailored to patient, surgical needs and surgeon skill level. In addition to multimodal analgesia and early mobilization, the use of low pressure techniques should be added to the ERAS protocol. Surgical training needs to focus on low pressure techniques and be accompanied with suitable neuromuscular blockade. Additional multicenter trials are required to determine the optimal pressures, long-term results, and patient-specific guidelines. Hospitals must establish protocols and regularly audit them to see that they are implemented, enhanced and used to ensure the safety of their patients.