The satisfaction score following percutaneous nephrolithotomy was high in the group PVB, indicating that PVB is sufficient to provide post-surgical analgesia after such a procedure. Up to six hours after surgery, the individuals who underwent PVB scored significantly better on VAS than those in whom this anaesthetic procedure was not undertaken. This superiority did not persist after the 6 hour post-surgical interval.
The results from this study are in line with other published research on using PVB in PCN. However, there are disparities in the other studies in terms of timing, optimal concentration of local anaesthetic and the level at which to inject. It is also unclear whether one or more infiltrations of local anaesthetic are needed [8,9,10,11,12].
Different techniques have been employed previously for PVB. A technique relying on loss of resistance has been described, which was in use before ultrasound guidance became available within operating theatres. Ak, K. et al. described injecting 0.5% levobupivacaine at the level of the tenth, eleventh and twelfth thoracic vertebrae. 4mL were infiltrated at each level as the surgery, conducted under general anaesthesia, ended. These researchers noted that pain at rest as assessed by VAS was significantly improved following PVB, for two hours post-surgery . The present study differed in how PVB was used. In the present study, the patient was conscious and sitting upright as 20mL bupivacaine 0.25% was infiltrated. We found pain relief lasted for 6 hours post-surgically. The difference in observed outcome compared to other studies may relate to the difference in injection volume and the prolonged action duration of bupivacaine compared to levobupivacaine.
Hatipoğlu et al. reported on performing PVB at levels T11, T12, L1 prior to surgery but with the patient under general anaesthesia and placed in a prone position. They employed 0.5% bupivacaine, injecting 5ml per level under ultrasound guidance. Thus the total volume of local anaesthetic was 15mL. These authors state that analgesia was mantained up to 24 hours post-surgery . Our findings reveal that the VAS-rated discomfort was significantly lower in group PVB than in group C until 12 hours post-surgery when the patient was moving, but not while at rest. We performed the procedure without patient sedation, with the patient sitting upright before the operation.
Patient positioning may affect the distribution of local anaesthetic from a single injection when the concentration is low. This may be the explanation for the difference of duration of analgesia.
Yayık et al. investigated analgesia procured through PVB vs peritubal infiltration. VAS dynamic and resting scores were significantly lower in the PVB group than the peritubal infiltration group or a control group at all time points following surgery up to 24 hours post-surgery. They performed the PVB procedure with the patient in the prone position. They employed 0.25% bupivacaine injected at levels T8-9, at the end of surgery . Our study used the same concentration and volume of bupivacaine, however PVB was undertaken prior to surgery.
A different study also employed PVB in percutaneous nephrolithotomy. A catheter was inserted into the paravertebral space at level T10 prior to commencing surgery. Catheter insertion was in awake patients, sitting upright. Ultrasonic guidance was not used. Twenty mL bupivacaine 0.5% was injected prior to surgery. Rescue analgesia was noted to be required first at 275 minutes post-surgery . The duration of analgesia achieved with this volume and concentration indicates that PVB involving a single injection is insufficient for complete analgesia postoperatively over the first 24 hours post-surgery. However, it does lead to a decreased need for systemic analgesic drugs. In our study, we used a lower concentration but the same volume of bupivacaine. For the first 4 hours post-surgery, VAS scores, both dynamic and resting, were significantly lower in group PVB than in the control group. Our results indicate that the duration of PVB is 6 hours using bupivacaine 0.25% in 20 mL total volume.
Baldea et al. report on a study in which PVB block was performed at the level of T10 by means of a single injection of 20mL 0.5% bupivacaine. The block was performed prior to surgery with the patient seated and under ultrasound guidance. The first dose of opioids for relief analgesia was given at 119.7 minutes post-surgically in the PVB group .
It is clear that PVB is efficacious in providing analgesia for percutaneous nephrolithotomy. Indeed, PVB, together with epidural anaesthesia, are considered Gold Standard procedures. Newer studies have focused on lengthening the duration of analgesia through the addition of adjuvant therapy, notably clonidine and dexmedetomidine [14,15].
Kamble et al. compared PVB for PCNL using either 0.5% Bupivacaine alone or 0.5% Bupivacaine plus 1μg/kg of clonidine: PVB was performed prior to surgery in awake patients in the sitting position. Clonidine was shown to have an adjunctive role with bupivacaine, providing a higher quality paravertebral block and prolonging analgesia to a significant extent post-surgically. The dosage employed took account of patient weight: 15ml in patients with a weight below 60kg and 18ml in patients with a weight exceeding 60kg . Our study, did not address whether adjuvant pharmacological agents affect the duration of analgesia, although it did establish that a single injection of 0.25 % bupivacaine in 20 mL volume produced an analgesic effect lasting eight hours after surgery ended.
Another study examined the use of PVB in video-assisted thoracic surgery (VATS). In that study, two treatments were compared: ropivacaine 0.5% in a volume of 30mL with adjuvant dexmedetomidine 50 microgram or ropivacaine 0.5% in 30mL alone. The level of injection was between T3 and T5. Two injections were given in the lateral decubitus position. The treatment was post-surgical but before the patient recovered consciousness. Adjuvant dexmedetomidine lengthened the duration of analgesia obtainable with bupivacaine alone. The pain score at rest (assessed using VAS) did not differ significantly at any point postoperatively, with the exception of 4 hours post-surgery. In the adjuvant therapy group, the maximum VAS pain scores for the 24 hour post-operative period while resting or when coughing were lower than those seen in the group receiving ropivacaine alone. This result attained statistical significance . It seems that further research is needed to determine the optimal dose of local anaesthetics with or without adjuvant and to clarify the ideal timing to perform PVB, i.e. before surgery or post-surgically.
Our study showed that patient satisfaction was higher in the PVB group than group C. If PVB is performed in awake patients, a single injection may be preferable to multiple injections. Research on cadavers demonstrated that the spread of infiltrated anaesthetic was no different, whether injection occurred singly or at two levels. This study also employed ultrasonic guidance . Additionally, some research has evaluated single injection vs multiple injection in PVB to the thorax. The trial participants underwent VATS, after which they had PVB using nerve stimulators to guide the injection. In terms of efficacy, the single puncture technique was potentially superior to multiple puncture, since the patients were more satisfied, the procedure took less time and there was a lower risk of developing complications .
Whilst PVB has become the de facto Gold Standard in chest surgery, this has yet to be acknowledged in the literature on the subject . A number of studies have demonstrated the safety and efficacy of PVB to provide analgesia perioperatively in procedures affecting the kidney [19,20].
The reports published so far about the occurrence of complications mention a risk of inadvertent epidural or intrathecal injection in approaching 1% of cases. Ultrasound was not used for guidance where this occurred. Total spinal anaesthesia has occurred on some occasions . Total spinal anaesthesia has even occurred once when ultrasonic guidance was in use, but this case was approached with an out-of-plane technique . This study followed a retrospective design to assess the degree of complications associated with single-puncture, transverse, in-plane PVB with ultrasonic guidance. All participants underwent mastectomy. Some 1,427 PVBs were performed on the thorax, with no more than 6 complications occurring. Amongst other complications, bradycardia leading to symptoms with hypotension (n = 3), one vasovagal attack (n = 1), and a potentially toxic reaction to the local anaesthetic (n = 2). Neither inadvertent rupture of the pleura nor a pneumothorax leading to symptoms occurred .
Both in this study and in the authors' routine practice, the authors have a preference for the in-plane anaesthetic technique. Complications of the technique, including bleeding or technical issues, did not occur.
This study suffers from certain limitations. For example, we were unable to assess precisely the tramadol dosage needed, since patient-controlled analgesia, which would give a clear picture, was not used. In addition, the area of block achieved was not precisely delineated by performing a sensory neurological examination.