Laparoscopic surgeries are becoming more attractive because of an early recovery.1,2 However, postlaparoscopic shoulder and upper abdominal pain may cause more discomfort to the patient than the pain at the incision site.3–7 The incidence of shoulder pain varies from 35% to 80%.6,7 Residual carbon dioxide (CO2) after laparoscopic surgery is trapped between the liver and the diaphragm and subsequently induces phrenic nerve irritation, consequently leading to postlaparoscopic shoulder and upper abdominal pain.8–12 Many strategies have been attempted, such as the use of nonsteroidal anti-inflammatory drugs; however, the effect is limited, and there are no reliable methods available yet.13,14
The pulmonary recruitment maneuver can mechanically remove residual CO2 and reduce pain; nevertheless, the effects were only observed immediately after the operation and disappeared later.3,11 By contrast, the effect of intraperitoneal normal saline infusion, which washes out CO2 with a physiologic buffer system, maintains longer.3,15 Because the two interventions are mediated through different mechanisms and act in different phases, we hypothesized that combined pulmonary recruitment maneuver and intraperitoneal normal saline infusion may be ideal to reduce postlaparoscopic shoulder and upper abdominal pain. Therefore, we conducted this randomized controlled trial to estimate the effectiveness of combined pulmonary recruitment maneuver and intraperitoneal normal saline infusion on postlaparoscopic pain.
MATERIALS AND METHODS
The study was designed as a randomized, controlled, clinical trial. Participants were recruited at a tertiary medical center in Northern Taiwan from 1 May 2011 through 31 March 2012. Approval for the study was obtained from the local ethics committee, and informed consent was obtained from all patients (VGHIRB 2011-03-012 IA; NCT01433874; Institutional Review Board, Taipei Veterans General Hospital, Taipei, Taiwan). Based on our preliminary data of 24-hour and 48-hour pain scores in the previous study,3 we used 2.7±2.4 compared with 5.6±2.8 (mean±standard deviation [SD]) and 1.9±1.3 compared with 3.2±2.5 for the intervention group and control group, respectively, as the primary criterion in our power analysis (power=0.85 and α=0.05, equal sizes for both groups and a two-tailed test) to calculate a minimum sample size of 44 patients for each group. Assuming a 20% drop-out rate, the trial protocol specified a sample of 110 patients.
A total of 110 patients scheduled for elective laparoscopic surgeries were screened in this study. The patients selected for screening were all consecutive cases of one study surgeon (Y.J.C.) and who required laparoscopic surgery during the study period. The inclusion criteria were female gender, age 20–65 years, an American Society of Anesthesiologists physical status classification of I or II, and a willing to undergo laparoscopic surgeries for benign gynecologic lesions, including laparoscopically assisted vaginal hysterectomy, myomectomy, and cystectomy. Patients were excluded from randomization if their disease was malignant, or if they were unwilling to participate. Randomization was performed using a computerized balanced (1:1) method. Random numbers were computer-generated. The randomization code was inserted into numbered, sealed, and opaque envelopes. A single envelope was opened by the surgeon when the patient was hospitalized. Surgeons and anesthesiologists were not masked to intervention after assignment. The patients were anesthetized and the investigator who assessed the outcomes was not present in the operating room during the intervention. Therefore, the patient, postoperation care unit staff, and the investigator obtaining postoperative scores were blinded to group allocation. Finally, the data for 100 patients were analyzed (Fig. 1).
All operations were performed by two experienced surgeons (Y.J.C. and H.W.T.) during the study period. The postoperative assessment was performed by two independent investigators (T.F.H. and M.S.Y.). Dr. Hsu was in charge of the data. Dr. Tsai, Dr. Wang, and Dr. Chen wrote the paper, and the critical revision of the manuscript for important content intellectual content was finished by Dr. Wang. Dr. Chao was a coordinator of this project.
For precise pain evaluation, we used four ports as the standard procedure for all laparoscopic surgeries to minimize the effects secondary to the number of port wounds. One 12-mm port was inserted through the umbilicus, and the other 5-mm ports were inserted through the lateral lower abdominal wall and suprapubic area.16,17 Laparoscopy was performed using CO2 gas as the distention medium, which was introduced through a Veress needle placed intraumbilically. The intra-abdominal gas pressure and the total volume of gas delivered during the procedure were monitored. The gas pressure was set at 15 mm Hg during the procedure. The flow of CO2 did not exceed 2 L/min when creating the pneumoperitoneum.16,17
In the control group, we performed the routine method by applying gentle abdominal pressure and removing CO2 by passive exsufflation through the port site at the end of the surgery. In the intervention group, we filled the upper part of the abdominal cavity evenly and bilaterally with isotonic normal saline (15–20 mL/kg body weight) and left it in the abdominal cavity.3,15,18 Intraperitoneal normal saline infusion facilitates the dissipation of CO2 in the abdominal cavity as a physiologic buffer system.19 Then, the patients were placed in the Trendelenburg position (30 degrees), and the anesthesiologist performed five manual pulmonary inflations at a maximum pressure of 60 cm H2O.3,11 Pulmonary recruitment maneuver was performed mechanically using positive-pressure ventilation to inflate the lungs and lower the diaphragm, which can increase intraperitoneal pressure mechanically and remove residual CO2 from the peritoneal cavity.11 During these procedures, the surgeon had to fully open the port sleeve valve to allow the CO2 to escape the abdominal cavity. The patients were then placed back in the level position, the port was removed, and the abdominal incisions were closed.
Postoperative pain was controlled with meperidine hydrochloride intravenously as needed within 48 hours after operation. Nonsteroidal anti-inflammatory drugs were not used within 48 hours after operation. The postoperative hospital stay (in days), duration of surgery, estimated blood loss (in milliliters), and cumulative dosage of meperidine hydrochloride all were recorded.
The primary endpoint of this study was postlaparoscopic upper abdominal pain and shoulder pain as measured by a visual analogue scale (VAS), using a linear VAS with a slide.20,21 The VAS consisted of a nongraduated 10-cm line ranging from “no pain” to “pain as bad as it could be.” The patient was asked to indicate a score from 0 to 10 corresponding to the perceived pain. Visual analogue scale ratings were obtained 12, 24, and 48 hours postoperatively for each of the following three types of pain: upper abdominal pain; shoulder pain; and surgical pain (trocar wound and visceral pain). Secondary outcome measures included the occurrence of nausea or vomiting and abdominal distention. Abdominal distention was defined based on the symptoms of the patients or postoperative gastrointestinal dysfunction and prolonged ileus based on the clinical judgment of the attending physician.22 In addition, the total dose of postoperative meperidine usage was calculated for each woman during the postoperative 48 hours.
Statistical analysis was performed with SPSS 17.0.0. Descriptive statistics are presented as the mean±SD or numbers with percentages. Analysis by χ2 test or Fisher exact test was performed to evaluate discrete variables. For continuous variables, we used Student t test. The generalized linear model for repeated measures was used for between-group comparisons of the pain scale. A two-tailed P<.05 was considered significant.
From 1 May 2011 to 31 March 2012, a total of 110 patients were screened for eligibility, of whom 8 were excluded. Five refused to participate in the study, and three had grade III physical status by the American Society of Anesthesiology system. Therefore, 102 patients were randomized. Two patients were excluded from the analysis because they were converted to laparotomy. Thus, 100 patients (50 in the intervention group and 50 in the control group) were included in the final analysis (Fig. 1). The demographic and intraoperative data (duration of surgery and estimated blood loss), procedure of laparoscopic surgery, and postoperative hospital stay were similar for both groups (Table 1).
At 12, 24, and 48 hours, the incidence of laparoscopic-induced shoulder pain was lower in the intervention group (54%, 46%, and 30%, respectively) than in the control group (72%, 70%, and 50%, respectively; P=.008, P=.001, and P=.004, respectively). The number needed to treat for benefit to reduce shoulder pain incidence was 6 (95% confidence interval [CI] 4–21) at 12 hours, 5 (95% CI 3–10) at 24 hours, and 5 (95% CI 4–15) at 48 hours. The incidence of laparoscopic-induced upper abdominal pain also was lower in the intervention group (78%, 72%, and 58%, respectively) than in the control group (92%, 90%, and 70%, respectively) at 12, 24, and 48 hours postoperatively (P=.006, P=.001, and P=.077, respectively). The number needed to treat for benefit to reduce upper abdominal pain incidence was 8 (95% CI 5–24) at 12 hours and 6 (95% CI 4–14) at 24 hours.
Among women who reported shoulder and abdominal pain, the postlaparoscopic pain scores were significantly lower in the intervention compared with the control group at 12 and 24 hours postoperatively. The shoulder pain scores were lower in the intervention group than in the control group at 12 hours (mean±SD 2.90±2.93 compared with 4.50±3.41, respectively; P=.014), 24 hours (mean±SD 2.76±2.91 compared with 4.52±2.99, respectively; P=.004), and 48 hours (mean±SD 1.76±2.50 compared with 3.10±2.88, respectively; P=.015). The upper abdominal pain scores also were lower in the intervention group than in the control group at 12 hours (mean±SD 5.30±3.15 compared with 6.90±2.66, respectively; P=.008), 24 hours (mean±SD 4.64±2.95 compared with 5.90±1.80, respectively; P=.013), and 48 hours (mean±SD 2.78±2.34 compared with 3.66±2.44, respectively; P=.073). Further analysis of shoulder pain and upper abdominal pain with repeated measures confirmed the between-group effect of the intervention (generalized linear model for between-group comparisons, P=.001 and P=.002; time-by-intervention interactions, P=0.469 and P=0.319; Fig. 2).
The incidence and intensity of surgical wound pain did not differ between groups at 12, 24, and 48 hours. Analgesic requirements and case numbers and percentages of postoperative nausea or vomiting or abdominal distention also were not significantly different. Therefore, the intervention we performed might not make patients uncomfortable. There were no cardiovascular or pulmonary complications in either group (Table 2).
Postlaparoscopic shoulder and upper abdominal pain is an important issue.1,2 We conducted this randomized controlled study and reported a practical intervention that could reduce both the incidence and intensity of shoulder and upper abdominal pain after laparoscopic surgery.
The advantage of this combination is that each method not only works through different mechanisms but also acts at different phases. The pulmonary recruitment maneuver can remove residual CO2 from the peritoneal cavity and result in less intra-abdominal acidosis and consequent phrenic nerve and peritoneal irritation.11 Phelps et al11 reported that it could reduce positional pain from 63% to 31%. Our previous study also had similar results that were observed immediately after surgery at 12 and 24 hours but disappeared at 48 hours.3 Therefore, the pulmonary recruitment maneuver works effectively but is short-acting. Comparatively, the effect of intraperitoneal normal saline infusion is long-lasting until the warmed normal saline is absorbed.18,23 Our previous study revealed that at 48 hours postoperatively, the effect of intraperitoneal normal saline infusion was still persistent and led to significantly reduced upper abdominal pain and shoulder pain.3 Intraperitoneal normal saline infusion offers a physiologic buffer system: CO2 dissolves in water, is absorbed into the intravascular space, is transferred to the lung, and is converted back into CO2 to be expelled.19
One may question whether the combined intervention is safe. Coughing and sneezing can increase the intrapulmonary pressure to 80–130 cm H2O, which is relatively higher than our pulmonary recruitment maneuver, with a maximum pressure of 60 cm H2O.24,25 Thus, the risk for a pneumothorax seems low. In addition, the extra fluid used in intraperitoneal normal saline infusion can be absorbed by the peritoneum at a rate of 30–60 mL/h.26,27 In our study, we did not observe any cardiovascular or pulmonary adverse effects. However, the average patient in this study would have received 800–1,200 mL normal saline, and we would recommend caution in certain populations, such as patients with cardiac disease who might have adverse effects from overload of fluid. Other situations after intraperitoneal normal saline infusion for laparoscopic surgery, such as subcutaneous fluid accumulation (for example, vulvar edema) or leakage of saline from port sites might occur.28,29 In our study, these situations did not happen, partly because we used pulmonary recruitment maneuver, which could push out the excess fluid in the peritoneal cavity.
The combined intervention significantly lowered shoulder and upper abdominal pain scores and incidence. The number needed to treat in the combined intervention further indicated that this strategy might be an effective method to decrease shoulder pain and upper abdominal pain after laparoscopic surgery, although there was no difference in the use of analgesic requirements between the two groups. It was possible that analgesics could not reduce postlaparoscopic pain induced by CO2 retention,13,14 and the immediate postoperative wound pain could not be relieved by this combined intervention. Of course, further research is warranted.
Strong points of this study include the prospective and randomized design, and all patients were examined in the same hospital. Compared with the study by Esmat et al23 of low-pressure pneumoperitoneum, our study was performed with standard-pressure pneumoperitoneum. Moreover, we performed elective surgeries, not outpatient surgeries, compared with the pervious study by Phelps et al.11 In addition, postlaparoscopic pain evaluation could be more precise and accurate because these patients remained hospitalized for 48 hours postoperatively.
Our study has certain limitations. First, different surgical types and the length of surgery might interfere with pain evaluation, although there was no difference in the surgical types between groups. Second, we have focused on only benign gynecologic diseases; however, other procedures, such as laparoscopic cholecystectomy, need validation. Third, two patients were excluded from the analysis because they required laparotomy. The data for these two patients were not available, so these patients were not included in an intent-to-treat analysis.
In conclusion, our study provides a clinical result using the combined pulmonary recruitment maneuver and intraperitoneal normal saline infusion to reduce postlaparoscopic shoulder and upper abdominal pain significantly. This combined intervention is effective, inexpensive, and easily implemented in daily clinical practice.
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