Interpretation
Ghezzi et al. 19 and Grube et al. 20also failed to show effectiveness of preemptive trocar-site analgesia in reducing postoperative pain. Arden et al. 21 reported that intraperitoneal instillation of bupivacaine at the end of laparoscopic hysterectomy did not reduce postoperative pain, nor did it affect the utilization of opioid analgesics.
Nevertheless, a few studies reported beneficial effect for the aforementioned interventions. Ravndal et al. 3reported that preemptive local anesthetics injected into the trocar sites reduced postoperative pain at ambulation 5 hours after surgery. Chou et al. 4showed that the combination of preoperative and postoperative intraperitoneal Bupivacaine reduced pain at 2 and 4 hours postoperatively.
A few systematic reviews have also addressed the role of different interventions for reducing postoperative pain. Ong et al.22 found no beneficial effect of preemptive local anesthetic wound infiltration on postoperative pain; however, this intervention was shown to reduce postoperative analgesic consumption. Marks et al 5 found that analgesia instilled intraperitoneally significantly decreased pain during a 6-hour interval after laparoscopy. Long et al. 10 studied the evidence regarding the practice of preemptive analgesia in various forms. They reported modest effect of incisional infiltrations and stated that conclusions drawn by previous studies are conflicting. In addition, they found that intraperitoneal analgesia given upon completion of surgery is likely beneficial.
Our findings, namely the lack of effectiveness for both incisional site and intraperitoneal analgesia administration, could have a number of explanations. First, it is possible that the analgesic dosage we used is insufficient. The maximal dosage of Bupivacaine allowed for local analgesia in adults is 175mg, since it is associated with the highest risk of cardiovascular toxicity among the various local anesthetics available 23. Because we combined two modalities of analgesia (subcutaneous and intraperitoneal), we chose the lowest dose that had been shown to be efficient for each modality24. Therefore, it is possible that due to safety concerns we failed to reach the threshold for adequate postoperative pain relief. Secondly, most patients in our study underwent minor surgeries, such as diagnostic laparoscopies and salpingectomies. It is possible that if we included only major surgeries (such as hysterectomies and myomectomies), higher levels of pain would have been reported and statistically significant differences in primary and/ or secondary outcomes would have been obtained. Nevertheless, it is important to mention that 5mg (20ml of 0.25%) Bupivacaine instilled subcutaneously was reported to be effective in reducing postoperative pain even in diagnostic laparoscopies 17. It is also possible that the immediate postoperative pain relief, was a confounding factor since it lowered the level of postoperative pain. However, as all the medications administered at recovery room have an elimination half-life (T1/2) of up to six hours, together with the fact that no difference in MME was detected between the groups, it is safe to assume that the immediate postoperative pain relief did not affect the primary outcome. Lastly, our patients possibly reported only low to medium postoperative pain because they were merely asked to move from prone to sitting position, rather than engage in more strenuous activities, such as walking in the ward.