In recent years, VATS LOBECTOMY has been widely used and benefited many patients. Effective pain management after VATS LOBECTOMY is critical to reduce complications, quicken recovery and decrease the risk of development of chronic postoperative pain. To the best of our knowledge, the present study is the first to perform thoracoscopic-guided PVB combined with ropivacaine and DEX as a component of multimodal postoperative analgesia which demonstrated a successfully opioid-sparing effect as well as a reduced rescue analgetic consumption, significantly decreased postoperative pain intensity and increased quality of recovery scores on the early stage. In addition, it was also associated with a higher rate of appropriate sedation level and a lower incidence of postoperative PONV.
Although VAST has been regarded as the standard minimal invasive surgical procedure for lung resection since it was first introduced in 1992, previous study has reported that moderate to severe acute pain remains a crucial problem in patients who underwent VAST due to utility incision, pulmonary parenchymal damage, muscular damage, pleural inflammation and placement of chest tube, which can impair coughing, secretion clearing, forced vital capacity and forced expiratory volume resulting in possible respiratory insufficiency, bronchial obstruction and pulmonary infection[11, 12]. Although significantly lower incidence was observed, approximately 34% of patients suffer chronic pain from VATS procedures. Therefore, it is critical to take aggressive multimodal analgesic strategies to control acute pain in order to prevent these complications, reduce the likelihood of developing chronic pain and enhance recovery following VAST LOBECTOMY. Although the optimal analgesic strategy following VATS LOBECTOMY remains a controversial problem, regional analgesic will provide improved analgesia and reduced incidence of pulmonary complications in comparison to systemic analgesia with parenteral opioids[13].
Currently, TEA remains the gold standard for analgesia with highest degree of patients’ satisfactory following open thoracotomy, which provides superior analgesia to systemically administration of conventional pain killers causing systemic side effects such as nausea, vomiting, constipation and even kidney damage[14]. However, performance of TEA requires highly trained technique with the risk of accidental dural puncture, epidural haematoma, neurological injure and inadvertent total spinal anesthesia, as well as a failure rate of 14–30%. A TEA can also result in both vasodilatation and cardiac depression causing hypotension due to bilateral sympathetic nerve block or urinary retention due to suppression of urination reflex, which limited it’s use. In addition, it is not suitable for patients with anticoagulant or blood clotting disorders, cardiovascular dysfunction and previous spinal surgery[15]. Recently, reviews have demonstrated that paravertebral block is a promising alternative to epidural block for its convenience and safety. It provides an equivalent effect in terms of controlling acute pain, and reduces the risks of developing postoperative complications in comparison to TEA, specifically urinary retention and hypotension[16, 17]. The triangular thoracic paravertebral space is consisted of spinal nerves, intercostal nerves and sympathetic nerve chains after leaving the intervertebral foramen, injecting LA into this space can block the ipsilateral somatosensory and sympathetic nerves. Hence, respiratory and sympathetic function can be preserved on the contralateral side which is related to fewer pulmonary complications, less hypotension and urinary retention in comparison with thoracic epidural technique[18]. A Vogt et al conducted a double-blind, prospective, randomized trial to test the hypothesis that a single-injection thoracic PVB at the sixth thoracic vertebra produced clinically significantly lower pain scores than PCIA alone up to 48h after thoracoscopic surgery. They found that two dermatomes above and below the injected level were successfully blocked in most patients, which was consistent with the results of Cheema’s research showing that pain sensation after thoracoscopic surgery could be sufficiently blocked by spread of 10-15ml of LA into a mean sensory level of 2.2 segments above and 1.4 segments below the injected level[19, 20]. Besides lateral spread of LA into the intercostal space after single-injection, cephalic-caudal spread covering many thoracic dermatomes will also develop, because the paravertebral space is contiguous with the intercostal and epidural space[21]. A recent prospective randomized trial compared single-injection PVB, PVB catheter or TEA for postoperative analgesia following VATS, single-injection PVB was faster and equally as effective as PVB catheter, and it led to similar patient satisfaction as TEA. Therefore, they recommended single-injection PVB technique to be considered in patients not suitable candidates for TEA[22]. We also advocate that in contrast to single-injection PVB which has less technique challenges, continuous PVB through a catheter will unnecessarily expose patients to additional risks to pleural disruption during PVB catheterization. Furthermore, the catheter and device which are specifically used for PVB is still conflicting up to now. Several previous studies reported conventional or commercially available epidural catheter was indwelled in paravertebral space as the paravertebral catheter leading to a 29.5% incidence of pleural disruption[23]. Unfortunately, PVB catheter implantation was also contraindicated in patients as conduction of TEA. The failure rate was high for PVB catheter placement and management in clinical practice. Because the effect of continuous analgesia of PVB has been proved to be associated with the appropriate location of paravertebral catheter and the working diffusion of analgesic drugs among the paravertebral space which highly required established technology standard, well-trained practitioners and well-equipped facility[24, 25]. Rather than continuous PVB, previous study evaluated multiple-space technique at the fourth and seventh paravertebral space, in which the spread of LA was considered sufficient for the somatic and sympathetic pain control from the trauma resulting from VATS LOBECTOMY. They found that multiple-injection PVB contributed to effective pain relief and a significant reduction in opioid requirements[26]. Cowie et al compared the spread of contrast dye in single-injection PVB at thoracic 6–7 segment with 20ml contrast and multiple-injection PVB at thoracic 3–4, 7–8 segments with 10 ml of contrast in each, the result revealed that contrast dye spread more extensively across intercostal segments with 4.5 spaces (range, 2–10) covered with a single injection and 6 spaces (range, 2–8) covered with a dual-injection technique (P = 0.03). Therefore, multiple-injection technique at separate levels covered more thoracic dermatomes, which would contribute significantly to enhance the analgesic efficacy[27]. Consistent with previous studies, our results strongly favored for a significantly effective pain relief resulting in a significant reduction in intravenous sufentanil consumption after application of 2-space PBV injection upon completion of the VATS LOBECTOMY. In addition, the first analgesia time through PCIA in PVB group (70.14 ± 10.92) was significantly longer when compared with that in control group (40.19 ± 8.80). Compared with control group, the number of PCIA press (times) and rescue analgesia consumption for postoperative analgesia was significantly decreased in PVB group with p value equaling 0.034 and 0.006.
According to the previous literature, the effect of single-injection PVB with long-acting LA was expected to last 9 to 38 h with an average of 23 h after VATS LOBECTOMY[28]. A randomized, controlled clinical trial performed two-shot PVB with 20 ml of 0.375% ropivacaine at the thoracic interspace T4-5 and T7-8 combined with general anesthesia (GA), pain scores at rest at 4 h and 24 h, on cough at 4 h were lower in PVB/GA group in comparison with GA group (p < 0.05). But there was no difference in pain scores at rest at 48 h and on cough at 24 h and 48 h[29]. In order to prolong analgesia of PVB, the concentration of ropivacaine was increased to 0.5%. Additionally, there has been a large body of researches confirming that the combination of dexmedetomidine (DEX) as an adjuvant with LA can enhance and prolong nerve block and reduced the need for rescue analgesics without adverse neurological effects[30, 31]. Theoretically, as a novel α-2 adrenergic receptor agonist, has a dose-dependent sedative, anxiolytic and analgesic effect with minimum hemodynamics depression by inhibiting substance P release in the nociceptive pathway and activating the α-2 receptor in blue spot. Recently, a prospective, randomized, controlled study was conducted to evaluate ropivacaine with/without DEX in patients undergoing VATS LOBECTOMY. Compared with ropivacaine only, the addition of DEX to LA for multilevel thoracic PVB significantly reduced postoperative pain scores both at rest and during coughing starting from 4 h until 48 h after VATS LOBECTOMY[32]. As we expected, the VAS score of PVB group at rest and during exercising at all time points within the first 48 h after VATS LOBECTOMY was significantly lower than that of control group, which illustrated the effect of multiple-injection PVB using ropivacaine combined with DEX persisted at least 48 h. In addition, proportion of patients who reported appropriate sedation was also significantly higher in PVB group than that in control group at 2, 12, 24 and 48 h following VATS. Patients in PVB group also reported a better QoR-4o scores with a significantly better physical comfort scale and less pain than those in control group. The incidence of POVN in PVB group was significantly lower than that in the control group, which might be due to less consumption of sufentanil in PVB group. All the above-mentioned results in the present study supported the evidence that patients would benefit from improved postoperative analgesia with less systemic opioid consumption to obtain rapid recovery from surgery and avoid the corresponding complications[33].
As is well known, thoracic PVB under ultrasound (US) guidance is a recent technique providing several advantages in comparison with conventional thoracic PVB utilizing surface landmarks including enhanced reliability, direct visualization of needle puncture in real-time image. However, the methods of identification of PVB by US guidance, some rare but serious complications associated with this technique such as pneumothorax, inadvertent vessel puncture or injection is still the major issue. In addition, US-guided technique is an advance maneuver which highly depends on experience of the operator[34]. Therefore, whether there is a simpler, faster and less traumatic approach can guide the performance of thoracic PVB to meet the need of effective postoperative analgesia after VAST LOBECTOMY. Considering the fully and magnifying expose of the thoracic paravertebral structures under thoracoscopy after lung atrophy, it was easy to quickly complete multiple-injection PVB via the intrathoracic approach under thoracoscopic direct vision by the surgeon before closing the chest. In the present study, the transmural pleura was chosen to advance the needle vertically at a depth of 0.5 cm to avoid the risk of nerve root damage and inadvertent spinal damage.
There were some limitations in the present study: Firstly, follow-up was only conducted within 48 h after VATS, longer observation should be performed in a well-designed randomized trial in the future. Secondly, VAS scores which was adopted to evaluate postoperative pain intensity was highly subjective. Thirdly, although multiple-injection PVBs under guidance needed less technique challenges, experience was still a dominant factor in such approach, therefore, more researches were required with adjusted experience and learning curve in future.
As an important component of MMA, the analgesic regimen combining LA and DEX through the thoracoscopic-guided PVB provided an excellent level of postoperative pain management with reduced systemic opioid-related complications. It benefitted the early resumption of activity and physical function recovery. Thoracoscopy assisted positioning of the thoracic PVB is simple and effective with direct visualization of correct delivery of injectate, which might represent a valuable analgesic strategy for VATS procedure.