Patients undergoing laparoscopic gynaecologic procedures may suffer abdominal, incisional and shoulder-tip pain postoperatively . Release of inflammatory mediators, neuroendocrine stimulation, traumatic traction on nerves and tearing of blood vessels all result from the rapid distension of the peritoneum and play a role in the complex mechanism of pain after laparoscopy [2,3].
A number of different analgesic techniques such as treatment with non-steroidal anti-inflammatory drugs, wound injection of local anaesthetics, removal of insufflation gas and intraperitoneal local anaesthetic instillation have been attempted in order to improve postoperative analgesia after laparoscopic surgery . The analgesic effect of intraperitoneal local anaesthetics after laparoscopic surgery is controversial, and the reported results range from considerable pain reduction [5,6] to no significant influence on pain . The differences in results of the ‘intraperitoneal analgesia’ studies may be due to the type of surgery and the location, type and timing of local anaesthetic instillation . Single-dose application may be another reason for the failure of studies to show an analgesic effect.
In this study, we aimed to examine the impact of sequential injections of bupivacaine through a subphrenic catheter on postoperative abdominal pain, shoulder pain and analgesic consumption after gynaecological laparoscopy.
The Ethics Committee of our Hospital approved the study and all patients gave their written informed consent. Fifty-six American Society of Anesthesiologists (ASA) I-II patients scheduled for laparoscopic gynaecologic surgery were included in this prospective, randomized, placebo-controlled and double-blinded study with 28 patients in each group. Any patient with contraindications to meperidine, metamizole and bupivacaine or receiving analgesic medication on a regular basis was excluded. Patients were randomized according to a table of random numbers and the allocations kept in sealed envelopes. The gynaecologists and the nurses in the recovery room and on the ward were unaware of the treatment to which each patient had been randomized.
Anaesthesia was induced with 2.5 mg kg−1 propofol and 0.15 mg kg−1 cisatracurium to facilitate tracheal intubation followed by 1-1.5% end-tidal concentration of sevoflurane and 66% nitrous oxide (N2O) in oxygen. Heart rate (HR), non-invasive blood pressure (BP), peripheral oxygen saturation (SpO2) and end-tidal carbon dioxide (CO2), sevoflurane and N2O concentrations were monitored throughout the procedure.
Experienced gynaecologists performed all operations using a standard laparoscopic technique via three trocars. CO2 was insufflated to produce a pneumoperitoneum at 13 mmHg intra-abdominal pressure. At the end of the laparoscopic operation, the surgeon inserted an epidural catheter (B. Braun, Germany) into the peritoneal cavity through an 18-G Tuohy needle that was introduced through the abdominal wall 5-6 cm below the right costal margin in the mid-clavicular line. Thereafter, the tip of the epidural catheter was placed in the right subdiaphragmatic area with a forcep under laparoscopic control, and the pneumoperitoneum was ended. The proximal end of the catheter was secured with a bacterial filter. CO2 was evacuated carefully from the peritoneal cavity by manual compression of the abdomen with open trocars. The surgical wounds were not infiltrated with any local anaesthetics.
A 20 mL of bupivacaine 0.125% plus epinephrine 1: 200 000 or 20 mL of normal saline plus epinephrine 1: 200 000 were given through the subphrenic catheter before incision closure and at 4-hourly intervals for the first postoperative 20 h. A physician who did not participate in any phase of the study had prepared six syringes of blinded solutions for each patient in a sterile fashion. Pain scores, analgesic requirements, vital signs (arterial BP, HR, respiratory rate, SpO2 and body temperature) and side-effects were monitored before and after each bolus administration.
Postoperative pain at rest was assessed with a visual analogue scale (VAS) ranging from no pain (0 cm) to worst possible pain (10 cm). Induced pain was determined using a four-point scale: 0, no pain on coughing; 1, pain on coughing but not when breathing deeply; 2, pain when breathing deeply, but not at rest; 3, pain at rest. Postoperative nausea and vomiting (PONV) was assessed using the following scale: 0, no nausea or vomiting; 1, nausea; 2, vomiting or retching. A blinded investigator instructed all patients using these measures and obtained the scores after surgery. The arrival time into the recovery room was defined as ‘zero hours’ postoperatively. The severity of pain and PONV were recorded at 15-min intervals for the first hour and then at 2, 6, 12, 18 and 24 h after surgery.
A standard postoperative analgesic regimen was used in accordance with the severity of the patient's pain. If the VAS score was ≥4, the patients received 0.5-1 g intravenous (i.v.) metamizole. If the patients continued to have moderate to severe pain or on request, 0.5-1 mg kg−1 intramuscular (i.m.) meperidine (pethidine) was prescribed. Patients were given 8 mg i.v. ondansetron when the PONV score was either one or two. Total analgesic and antiemetic requirements were recorded during the first 24 h.
The catheter was removed after the last dose and the patients were discharged 4 h thereafter with 100 mg flurbiprofen tablets, as needed for pain relief at home. A questionnaire was given to all patients to continue recording average VAS scores, PONV (present/absent), shoulder-tip pain (present/absent), analgesic consumption daily at home throughout the first postoperative week after which they were asked to return the assessment sheets.
Sample size was determined by a power analysis of the study of pain after gynaecological laparoscopy, which utilized a VAS pain . We considered a 30% reduction in VAS pain scores to be clinically important. To reduce the risk of a beta error to 5% at a level of significance of α = 0.05, a treatment group size of 25 was required. We planned to recruit 56 patients, 28 into each group, in anticipation of the possible loss of some data. Results are expressed as mean (standard deviation (SD)) or median (range). Patient characteristics data were studied using t-test. Differences of pain intensity between the groups were calculated by two-way analysis of variance (ANOVA), whereas differences in the incidence of PONV and analgesic consumption were analysed with χ2-test and Fisher's exact test (for variables in which there was low frequency in at least one cell). A P <0.05 was considered statistically significant.
Fifty-one of 56 randomized patients completed the study. Three patients (one in the bupivacaine group and two in the saline group) were excluded from the study, as they did not return the questionnaire. Another two patients (one in each group) were excluded because each received metoclopramide instead of ondansetron. All patients were discharged after 24 h and none required readmission. There were no significant differences between groups for age [38 (6) yr vs. 34 (4) yr], weight [68 (6) kg vs. 65 (6) kg], duration of surgery [38 (8) min vs. 41 (9) min] or surgical indications [infertility (6 vs. 7), sterilization (10 vs. 10), pelvic pain (5 vs. 6) and endometriosis (4 vs. 3)]. No clinical signs of side-effect or toxicity related to the catheter, local anaesthetic or epinephrine were noted during or after the procedure. There was no difference between the vital signs of the groups.
The VAS pain scores at rest were comparable between the study groups at all times, except for the immediate postoperative value which was significantly higher in the saline group (P < 0.05) (Fig. 1). The number of patients who recorded a VAS ≤ 3 were significantly higher in the bupivacaine group compared to saline at the end of first postoperative hour [9 (35%) vs. 4 (16%), respectively] (P < 0.05). The induced pain intensity differed significantly between the saline group and the bupivacaine group [pain on coughing 2.1 (0.7) vs. 1.4 (0.5) respectively; P = 0.007] over the first postoperative hour, but not over the remaining time (Fig. 2). Spearman coefficients between VAS and induced pain scores were correlated at each time point in the two groups and ranged from 0.37 to 0.85 (P < 0.05).
There was no significant difference with regard to metamizole consumption between the groups (Table 1). The need for supplemental postoperative opioid was higher in the saline group compared to the bupivacaine group (P < 0.05) (Table 1). Since the patients experienced mild pain intensity in the ward, meperidine was consumed only over the first hour postoperatively. One patient in the saline group and two patients in the bupivacaine group did not require any supplementary analgesics.
Nausea was experienced by nine patients in the saline group (two with vomiting), and three in the bupivacaine group (without vomiting) immediately postoperatively (P < 0.05). The incidence of PONV was low and comparable between the groups throughout the rest of the study (Fig. 3). Ondansetron consumption was the same (Table 1).
There were no overall inter-group differences in VAS scores (Fig. 1), PONV scores or incidence of shoulder pain at the end of the first postoperative week. No patient rated her shoulder-tip pain or PONV as ‘severe’. The majority of patients reported shoulder-tip pain on the second postoperative day (52% vs. 61% in saline and bupivacaine groups, respectively) (Fig. 4). The number of patients consuming supplementary flurbiprofen was higher in the saline group (n = 24) compared with bupivacaine group (n = 14) (P < 0.05) (Table 1).
The main finding of the present study was that bupivacaine 0.125% administered intraperitoneally for 20 h was ineffective in reducing pain at rest and offered little additional benefit on induced pain, which was limited only over the first postoperative hour. On the other hand, a higher proportion of patients receiving subphrenic bupivacaine consumed less meperidine and flurbiprofen. There was no obvious adverse effect associated with this technique.
Free fluid in the right supramesocolic compartment should be able to reach the pelvic cavity via the right paracolic gutter . In this study, though the bupivacaine was instilled quite distant from the operative region, it may be expected to flow toward the supravesical, retrovesical (Pouch of Douglas) and paravesical compartments of the pelvis. The practice of intraperitoneal bupivacaine instillation through a subphrenic catheter has developed from the expectation of a decrease in both diaphragmatic and pelvic irritation.
Postoperative shoulder-tip pain is one of the most common causes of delayed discharge after day case laparoscopy and tends to persist beyond 24 h . Post-laparoscopic scapular pain is related to diaphragmatic stretching as well as to irritation by CO2, especially with the surface area of gas in contact with the diaphragm . Additionally, local anaesthetics infiltrated into the sub-diaphragmatic area may reduce the intensity of scapular pain [6,10]. In the present study, patients indicated shoulder-tip pain of a low intensity in both groups. Consequently, it can be speculated that the reduction in diaphragmatic irritation due to sequential fluid instillation may be related to the replacement of the residual gas rather than a local anaesthetic effect.
The failure of our method to provide significant differences in pain scores at rest between the groups could be attributed to a number of factors. First, the concentration of bupivacaine used in this study may be inadequate for a clinically relevant analgesic effect as the drug is disseminated over a large area. Intraperitoneal administration of bupivacaine, ranging from 62.5 to 125 mg, in a single dose has not caused systemic toxicity [12,13]. However, the administration of a single dose of bupivacaine higher than 125 mg intraperitoneally was not advised in the study by Raetzell and colleagues . In the present study, we applied a relatively low dose with adjuvant epinephrine for 20 h and observed no side-effects associated with toxicity. Secondly, it might be possible to detect a difference in pain scores if the patients were presented for major laparoscopic procedures. Gynaeco-logical laparoscopy causes only limited trauma to the abdominal wall. Gupta and colleagues  placed a catheter in the gall bladder bed after laparoscopic cholecystectomy and found a reasonable reduction in early postoperative pain with intermittent ropivacaine injections. This type of ‘intraperitoneal analgesia’ was found to be efficient in reducing visceral pain but not shoulder-tip pain or opioid consumption .
A limitation of the present study is the fact that a reliable and efficient intermittent dose of bupivacaine given intraperitoneally is still unknown and requires an indwelling catheter with increased cost though single-dose administration of an intraperitoneal local anaesthetic is simple and does not require hospitalization.
In conclusion, although the sequential administration of bupivacaine 0.125% intraperitoneally may offer a reduction both in induced pain in the early postoperative period with lack of long standing benefit and analgesic consumption, the subphrenic catheter technique is considered ineffective for treatment of abdominal and shoulder-tip pain after gynaecological laparoscopy.
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