Renal cancer is the disease with the highest mortality rate caused by the cancer of the urinary and reproductive system. Just in 2020, 431288 new cases of renal cancer were found in the world, with its incidence rate ranking 14th in malignant tumors, 9th and 14th in male and female malignant tumors respectively, and showing an increasing trend year by year [21]. Surgical resection is the main method for treating renal tumors. With advantages such as three-dimensional high-definition visual field, tremor filtering function, and flexible instrument operability, robot-assisted surgery systems have overcome the shortcomings of traditional laparoscopic techniques, and are increasingly being used in urological surgery for nephrectomy [22, 23]. However, robot-assisted laparoscopic nephrectomy generally combines somatic pain caused by surgical incisions, inflammatory pain caused by noxious stimuli, and visceral pain caused by chemical and mechanical stimulation [4, 24]. The mechanism of pain is complex, and perioperative pain control is extremely important.
The main purpose of our study was to observe whether thoracolumbar paravertebral block can reduce the amount of intraoperative remifentanil used and postoperative oxycodone used in patients undergoing robot-assisted laparoscopic nephrectomy, and to improve the postoperative analgesic effect. This study is different from previous studies in that it is the first time to observe the effect of thoracolumbar paravertebral block combined with general anesthesia on intraoperative and postoperative analgesia in patients undergoing robot-assisted laparoscopic nephrectomy. Thoracolumbar paravertebral block was selected based on the innervation of the kidney and surgical incision location, and related operations were performed under ultrasound guidance. Based on past experiences and researches, local anesthetic injection doses were set to ensure effectiveness while avoiding complications [14, 17, 18]. The termination of the psoas major muscle at the T12 vertebral body resulted in a lack of communication between the thoracic paravertebral space and the lumbar paravertebral space. Simply injecting local anesthetics into the thoracic paravertebral space may not block the T12 and lumbar paravertebral nerves. Therefore, in order to achieve a complete analgesic effect, we selected T9 and L1 to establish paravertebral block, based on the anatomical structure, studies and application results in previous.
In our study, the amount of remifentanil used in the TL-PVB group was 42.39% lower than that in the NO-PVB group during surgery (Fig. 4), the amount of oxycodone used 24 hours after surgery was 36.91% lower (Fig. 4), and the amount of oxycodone used 48 hours after surgery was 19.94% lower (Fig. 4), which indicated that thoracolumbar paravertebral block can significantly reduce the amount of opioids used during and after robot-assisted laparoscopic nephrectomy. The research results of Copik et al. showed that patients receiving thoracic paravertebral block combined with general anesthesia during open nephrectomy had a 39% reduction in the need for intravenous oxycodone within 48 hours after surgery compared to patients receiving simple general anesthesia, with reduced postoperative pain and adverse opioid events, and it was coincident with our study [25]. Compared to this study, the difference in the reduction rate of oxycodone may be related to different paravertebral block schemes, surgical methods, and population differences.
Thoracic paravertebral block has a unilateral epidural effect and does not affect the contralateral sympathetic nerve, which provides more stable hemodynamics [7–9]. In addition, Tang et al. compared the application of thoracic paravertebral block combined with general anesthesia and simple general anesthesia in patients undergoing laparoscopic radical nephrectomy [10]. The results showed that patients receiving thoracic paravertebral block combined with general anesthesia had lower heart rate and blood pressure, lower VAS during rest and movement 48 hours after surgery, and fewer adverse reactions such as nausea and emesis than patients undergoing simple general anesthesia. Similarly, in our study, the HR and MAP of patients in TL-PVB group were lower than those in NO-PVB group at the beginning of surgery, at the time when artificial pneumoperitoneum started, at the end of surgery, and at the time of leaving the operating room (Fig. 5), indicating that thoracolumbar paravertebral block combined with general anesthesia can reduce the hemodynamic effects of surgical stimulation.
In a similar study, Baik et al. demonstrated that thoracic paravertebral block can reduce postoperative fentanyl use and VAS at various time points 24 hours after surgery in patients undergoing open nephrectomy, and thereby improve postoperative analgesia [26]. By comparing the postoperative analgesic effects, it was found that patients in TL-PVB group had an average prolongation of 355.08 min in their first postoperative analgesic need compared to patients in NO-PVB group in our study (Fig. 6), and their VAS during rest and movement at various time points after surgery was significantly reduced (Fig. 7), which further demonstrated that thoracolumbar paravertebral block can reduce the amount of opioids and improve the postoperative analgesic effect. The above results of our study indicated that thoracolumbar paravertebral block can reduce the amount of opioids used during and after surgery, decrease the hemodynamic effects of surgical stimulation, and provide better analgesic effects.
Previous studies have shown that over 80% of patients had moderate to severe postoperative pain, and up to 70% of patients still had significant pain even after discharge [27]. Poorly controlled pain could lead to slowly postoperative recovery, wound infection, increased risk of cardiovascular complications, and delayed discharge [28, 29]. Perioperative weak opioid therapy can not only reduce postoperative adverse reactions and complications, but also have positive significance for tumor prognosis [27, 30]. In our study, it was confirmed that thoracolumbar paravertebral block combined with general anesthesia can reduce the amount of opioids used during and after surgery, and improve the postoperative analgesic effect. At the same time, it was observed that the postoperative anesthesia awaken time, the time to leave the operating room, the time to anal exhaust, the first time to get out of bed, and the length of postoperative hospital stay were shorter than those of simple general anesthesia, indicating that thoracolumbar paravertebral block can accelerate the postoperative recovery of patients.
In this study, there were no adverse reactions and complications related to the procedure in TL-PVB group, confirming the safety of ultrasound-guided thoracolumbar paravertebral block. It also reduced postoperative opioid related adverse reactions, which may be related to less use of opioids.
Some limitations can be found in our study. Firstly, the NO-PVB group has not been subjected to saline control and has not been compared with other blocking methods, hence it can only demonstrate that the effect is superior to that of patients under simple general anesthesia. Secondly, this study is a single center study, lacking of multicenter large sample studies. Finally, the long-term recovery effect of the patients was not observed. These limitations can be consummated by further research in the future.