Abstract
Introduction
Shoulder pain is one of the most common complications after laparoscopy. Previous studies have found a number of methods to reduce shoulder pain after laparoscopic surgery, but these methods have not been targeted to specific populations. The purpose of this study was to identify people who are more likely to develop shoulder pain.
Material and methods
A total of 203 patients underwent laparoscopy for benign gynecological diseases between July 2020 and February 2021. Patients were divided into two groups according to the Chinese overweight standard, body mass index less than 24 kg/m2 group and 24 kg/m2 or more group. The baseline characteristics and intraoperative data between the two groups were compared. The intensity of the shoulder pain was quantified using a visual analog scale (VAS).
Results
The incidence and the VAS scores of shoulder pain were significantly higher in the less than 24 kg/m2 group (63.64% vs 38.03%, p < 0.001 in incidence; median 5 (interquartile range [IQR] 3–7) vs 3 (IQR 2–5), p < 0.001 in VAS scores), and the chance of shoulder pain within 24 hours after laparoscopy was higher in the less than 24 kg/m2 group (89.29% vs 66.67%, p = 0.013). In univariate and multivariate logistic regression analysis, BMI less than 24 kg/m2 was an independent risk factor of shoulder pain after laparoscopic surgery (p = 0.001, p = 0.031, respectively). Shoulder pain scores were inversely correlated with BMI (r = −0.300, p = 0.001).
Conclusions
Patients with low body mass index are more likely to develop shoulder pain after laparoscopy, with earlier onset and higher pain scores.
Keywords: body mass index, laparoscopy, post‐laparoscopic shoulder pain, shoulder pain, strategy, visual analog scale
Patients with low BMI are more likely to develop shoulder pain after laparoscopy, with earlier onset and higher pain scores.
Abbreviations
- BMI
body mass index
- VAS
visual analog scale
- ASA
American Society of Anesthesiologists
Key message.
Patients with low body mass index are more likely to develop shoulder pain after laparoscopy, with earlier onset and higher pain scores.
1. INTRODUCTION
Laparoscopic surgery is widely used in gynecological disease diagnosis and treatment because of the advantages of less trauma, fewer postoperative complications, quicker recovery of daily activities, and shorter hospital stays. However, laparoscopic surgery can also induce postoperative shoulder pain, vascular injury, intestinal injury, urinary tract injury, air embolism, and other related complications. Among these complications, post‐laparoscopic shoulder pain is one of the most common complications of laparoscopic surgery, with an incidence rate of 34.1%–82.4%. 1 , 2
Many previous studies have confirmed that there are many strategies to reduce the incidence of shoulder pain after laparoscopic surgery, such as using analgesics, 3 lowering intraoperative CO2 pressure, 4 special position, 5 , 6 pulmonary recruitment maneuver, 7 , 8 reducing residual CO2 in the abdominal cavity by pressing the abdomen or abdominal drainage. 1 , 9 , 10 However, these strategies for reducing shoulder pain after laparoscopic surgery are not individualized to a specific population, and this may result in patients who do not develop shoulder pain being exposed to these interventions without any benefits. For example, low pneumoperitoneal pressure in obese patients who are less prone to postoperative shoulder pain may result in poor intraoperative visualization or postoperative indwelling of unnecessary abdominal drainage that increases the chance of infection. Therefore, identification of the group who are most likely to develop shoulder pain after laparoscopy, and use of individualized methods to reduce shoulder pain could maximize the benefits and minimize the harm.
Few studies have reported the relation between body mass index (BMI) and shoulder pain after laparoscopic surgery. 11 Therefore, it is of clinical importance to identify the relation between BMI and shoulder pain after laparoscopic surgery for benign gynecological diseases, and to identify the patient group most likely to experience postoperative shoulder pain.
2. MATERIAL AND METHODS
2.1. Study design
This is a retrospective cohort study conducted by a university‐affiliated hospital.
2.2. Participants
2.2.1. Inclusion criteria
Patients underwent laparoscopic surgery for benign gynecological diseases in the Department of Gynecology, People's Hospital of Shapingba District, Chongqing, China, from July 2020 to February 2021. Patients with malignant gynecological diseases or shoulder diseases or a history of these, those transited to laparotomy, and those refusing to provide any data were excluded from the study.
2.3. Surgery and perioperative management
All operations were performed by the same surgical team. The intraoperative pneumoperitoneal pressure was 12 mm Hg, and the flow rate was 3 L/min. At the end of the operation, abdominal compression was used to discharge residual CO2 in the abdominal cavity, and abdominal drainage was unnecessary. All patients underwent postoperative pulmonary recruitment maneuvers. Perioperative management according to the Recovery and Surgical Optimization Protocol for Minimally Invasive Gynecologic Surgery: An AAGL White Paper. 12 When patients presented with shoulder pain, oral non‐steroidal anti‐inflammatory drugs were used first, and if these were ineffective, intravenous pain medications such as intra‐opioids were administered.
2.4. Data collection
The patients’ baseline characteristics and intraoperative data were extracted from the electronic medical record system, and the postoperative information was obtained by the same investigator asking the patients. The collected data included: age, height, weight, partner, parity, American Society of Anesthesiologists classification, type of surgery, operative time, operative blood loss, postoperative shoulder pain, when shoulder pain started and disappeared, shoulder pain scores, oral or intravenous pain medication, and length of hospital stay. Shoulder pain data for all patients were collected 72 hours after surgery. The visual analog scale (VAS: 0–10 points, ranging from “no pain” to “pain as bad as it could be”) was used to quantify the shoulder pain.
2.5. Statistical analyses
SPSS version 26.0 was used for analysis. Continuous variables were analyzed by a two‐sample t test or Mann–Whitney U test, and categorical variables were analyzed by a chi‐squared test or Fisher exact test. Univariate and multivariate logistic regression analyses were used to detect the independent risk factors for shoulder pain among age, BMI, parity, education, operative time, operative blood loss, and length of hospital stay. Data were shown as mean ± standard deviation, median (interquartile range [IQR]), or the number of patients (%). A value of p less than 0.05 was considered statistically significant.
2.6. Ethics statement
The trial was approved by the Ethics Committee of the People's Hospital of Shapingba District, Chongqing, China on April 26, 2022 (Institutional Review Board reference no. KY202204). We obtained informed consent from patients to use their personal information and clinical data upon admission.
3. RESULTS
A total of 203 patients with BMI ranging from 15.42 to 36.05 kg/m2 were included. According to the Chinese definition of overweight, patients were divided into a less than 24 kg/m2 group and a 24 kg/m2 or more group. The former comprised 132 patients and the latter 71 patients. The number of patients with a partner was not statistically different, nor was the American Society of Anesthesiologists' Classification between the two groups (p = 0.615, p = 0.643). Patients in the less than 24 kg/m2 group were younger, more educated, had fewer births, shorter operative times, lower levels of operative blood loss, and shorter length of hospital stay (p < 0.001, p < 0.001, p < 0.001, p < 0.001, p = 0.001, p < 0.001). No patients had prolonged hospital stays or readmissions for shoulder pain. Table 1 presents the baseline characteristics and intraoperative data of the two groups.
TABLE 1.
Baseline characteristics and intraoperative data of the two groups
| BMI <24 kg/m2 (n = 132) | BMI ≥24 kg/m2 (n = 71) | p value | |
|---|---|---|---|
| Age (years), median (IQR) | 34 (26–42) | 47 (41–52) | <0.001 |
| Partner | |||
| No | 12 (9.09%) | 5 (7.04%) | 0.615 |
| Yes | 120 (90.91%) | 66 (92.96%) | |
| Parity (births) | |||
| 0 | 39 (29.55%) | 6 (8.45%) | <0.001 |
| 1 | 61 (46.21%) | 27 (38.03%) | |
| ≥2 | 32 (24.24%) | 38 (53.52%) | |
| Education | |||
| Low | 13 (9.85%) | 27 (38.03%) | <0.001 |
| Moderate | 69 (52.27%) | 38 (53.52%) | |
| High | 50 (37.88%) | 6 (8.45%) | |
| ASA Classification | |||
| 1–2 | 125 (94.70%) | 69 (97.18%) | 0.643 |
| 3–4 | 7 (5.30%) | 2 (2.82%) | |
| Operative time (min) | 76 (51–107) | 128 (81–164) | <0.001 |
| Operative blood loss (mL) | 10 (10–50) | 30 (20–50) | 0.001 |
| Length of hospital stay (days) | 5 (4–7) | 7 (6–9) | <0.001 |
Note: Partner: Having a boyfriend or a husband is defined as having a partner.
Low education includes illiteracy and primary education.
Moderate education includes middle school, high school and technical secondary school education.
High education includes a college degree, a bachelor's degree or above.
Abbreviations: ASA, American Society of Anesthesiologists; BMI, body mass index; IQR, interquartile range.
About 84 (63.64%) patients in the less than 24 kg/m2 group had shoulder pain after surgery, while 27 (38.03%) patients in the 24 kg/m2 or more group had shoulder pain after surgery (p < 0.001). The relative risk was 1.673 (Table 2).
TABLE 2.
Number of patients with shoulder pain after laparoscopy
| Shoulder pain | BMI <24 kg/m2, n (%) | BMI ≥24 kg/m2, n (%) | p value |
|---|---|---|---|
| Yes | 84 (63.64%) | 27 (38.03%) | |
| No | 48 (36.36%) | 44 (61.97%) | |
| Total | 132 | 71 | <0.001 |
Univariate and multivariate logistic regression analysis showed that having a BMI less than 24 kg/m2 was an independent risk factor for shoulder pain after laparoscopic surgery (univariate odds ratio 2.85 [95% CI 1.57–5.18], p = 0.001; multivariate odds ratio 2.16 [95% CI 1.07–4.26], p = 0.031) (Table 3).
TABLE 3.
Univariate and multivariate logistic regression analysis for shoulder pain
| Variables | Univariate, p | Univariate, OR | Multivariate, p | Multivariate OR |
|---|---|---|---|---|
| Age (years) | 0.002 | 0.96 (0.94–0.99) | 0.176 | 0.98 (0.94–1.01) |
| BMI | ||||
| ≥24 kg/m2 | 1 | 1 | ||
| <24 kg/m2 | 0.001 | 2.85 (1.57–5.18) | 0.031 | 2.16 (1.07–4.26) |
| Parity (births) | 0.150 | 0.79 (0.57–1.09) | 0.362 | 1.22 (0.80–1.85) |
| Education | ||||
| Low | 1 | 1 | ||
| Moderate | 0.154 | 1.71 (0.82–3.58) | 0.412 | 0.64 (0.22–1.87) |
| High | 0.008 | 3.17 (1.36–7.38) | 0.359 | 0.71 (0.34–1.48) |
| Operative time (min) | 0.039 | 1.00 (0.99–1.00) | 0.911 | 1.00 (0.99–1.01) |
| Operative blood loss (mL) | 0.512 | 1.00 (1.00–1.00) | 0.869 | 1.00 (1.00–1.00) |
| Length of hospital stay (days) | 0.016 | 0.86 (0.77–0.97) | 0.774 | 0.98 (0.83–1.14) |
Abbreviations: BMI, body mass index; OR, odds ratio.
A total of 111 patients developed shoulder pain after surgery, 84 patients in the less than 24 kg/m2 group and 27 patients in the 24 kg/m2 or more group. Shoulder pain occurred in 75 (89.29%) patients in the less than 24 kg/m2 group within 24 hours after surgery, compared with 18 (66.67%) in the 24 kg/m2 or more group (p = 0.013).The postoperative shoulder pain scores were higher in the less than 24 kg/m2 group than the 24 kg/m2 or more group (median 5 [IQR 3–7] vs 3 [IQR 2–5], p < 0.001). The less than 24 kg/m2 group seemed to be more likely to need pain medication (27.38% vs 11.11%, p = 0.082). Unfortunately, there were no statistically significant differences in shoulder pain relief after 72 hours between the two groups (33.33% vs 22.22%, p = 0.276; Table 4).
TABLE 4.
Pain after laparoscopy
| BMI <24 kg/m2 (n = 84) | BMI ≥24 kg/m2 (n = 27) | p value | |
|---|---|---|---|
| Pain appearance within 24 h, n (%) | 75 (89.29%) | 18 (66.67%) | 0.013 |
| Pain scores, median (IQR) | 5 (3–7) | 3 (2–5) | <0.001 |
| Pain medication, n (%) | 23 (27.38%) | 3 (11.11%) | 0.082 |
| Pain relief after 72 h, n (%) | 28 (33.33%) | 6 (22.22%) | 0.276 |
Abbreviations: BMI, body mass index; IQR, interquartile range.
We also found a weak, significant, inverse relation between shoulder pain scores and BMI (r = ‐0.300, p = 0.001; Figure 1).
FIGURE 1.
Associations of shoulder pain scores and body mass index (BMI).
4. DISCUSSION
Our study found that post‐laparoscopic shoulder pain was more common in patients with low BMI, and these patients had earlier onset and higher pain scores after surgery. Univariate and multivariate logistic regression analysis showed that BMI less than 24 kg/m2 was an independent risk factor for shoulder pain after laparoscopic surgery. Shoulder pain scores were significantly, weakly, inversely correlated with BMI. Patients whose BMI was less than 24 kg/m2 seemed to be more likely to require pain medication.
Li et al reported that thin patients had a higher incidence of shoulder pain after laparoscopic infertility surgery, 11 which is consistent with our findings. However, our study evaluated all patients with benign gynecological diseases, and the results reflected risk factors for shoulder pain after laparoscopic surgery more accurately. Thin patients have a large space in the upper abdomen, and gas is likely to remain here after laparoscopic surgery, whereas obese patients have a tiny upper abdominal area covered by the omentum. The stretching of CO2 gas can irritate the diaphragm, causing shoulder pain. 13
Many previous trials have found that there are many ways to reduce the occurrence of shoulder pain after laparoscopic surgery, such as perioperative use of anesthetics, 14 , 15 pulmonary recruitment maneuver, 8 , 16 intraoperative use of low pneumoperitoneal pressure, 17 , 18 and postoperative intraperitoneal drainage. 1 , 9 These interventions did not stratify the population and this may result in patients who would not experience shoulder pain being exposed to these interventions without benefit or even with possible harm. For example, nausea, vomiting, and urinary retention caused by the routine use of analgesics after surgery or unnecessary drainage tubes indwelling in the pelvis increasing the chance of pelvic infection. We found that patients with low BMI were more likely to develop shoulder pain after laparoscopic surgery and had higher pain scores, so we believe that strategies to reduce shoulder pain would be more appropriate for patients with low BMI.
We also found that patients with BMI less than 24 kg/m2 were younger, had lower parities, and were more educated, maybe with the rapid development of China's economy in the past 30 years, young people have more opportunities for education and lower willingness to bear children. Our study also found that patients with BMI less than 24 kg/m2 had shorter operative times, lower levels of operative blood loss and shorter length of hospital stay, mainly because patients with a BMI less than 24 kg/m2 had more adnexal surgeries, patients with BMI of 24 kg/m2 or more were more likely to undergo uterine surgery, the proportion of uterine surgery between the two groups was 19.7% vs 49.3%, p < 0.001 (data not shown in tables). We did not find any association between operative time and postoperative shoulder pain. In contrast, patients with BMI of 24 kg/m2 or more had longer operative times and were less likely to develop shoulder pain, which may be related to the fact that less gas is likely to remain in the upper abdomen covered by omentum.
This study is the first to describe the relation between BMI and shoulder pain after laparoscopic surgery for benign gynecological diseases. The disadvantage of this study is that it is a retrospective study with a small sample size, and a prospective study with a larger sample size is hoped to confirm the results further.
5. CONCLUSION
Patients with low BMI are more likely to develop shoulder pain after laparoscopy, with earlier onset and higher pain scores. If future studies confirm the results of the present study, doctors could selectively apply many measures to relieve shoulder pain after laparoscopic surgery in patients with low BMI.
AUTHOR CONTRIBUTIONS
YJ and QL designed the study. YQ and YW collected the data. YJ and SL performed the statistical analysis. YJ, QL, and YC drafted the paper. All authors interpreted the data, critically revised the article, and approved the final version.
CONFLICT OF INTEREST
The authors have stated explicitly that there are no conflicts of interest in connection with this article.
ACKNOWLEDGMENT
We would like to thank all the staff at the Department of Gynecology, People's Hospital of Shapingba District, Chongqing, for their efforts in data collection and manuscript preparation.
Jiang Y, Wu Y, Lu S, Que Y, Chi Y, Liu Q. Patients with low body mass index are more likely to develop shoulder pain after laparoscopy. Acta Obstet Gynecol Scand. 2023;102:99‐104. doi: 10.1111/aogs.14477
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