RA for breast surgery
Breast cancer remains the most common cancer in women. 1, 2 Fortunately, due to improvements in early diagnosis and treatment (including breast conserving surgery), breast cancer survival continues to improve. However, several prospective trials have demonstrated that chronic postsurgical pain occurs in up to 40% of women undergoing this surgery. 3, 4 A recently published Cochrane meta-analysis confirmed the effectiveness of regional anaesthesia techniques for the prevention of chronic postsurgical pain for a variety of surgical procedures. This association has been hypothesised as being due to improved acute pain management and/or reduced central sensitization and opioid induced hyperalgesia. 5 Becuse LA placed within the paravertebral space can provide the dermatomal blockade appropriate for breast surgery, paravertebral nerve block is well suited to this surgery for reducing both acute and chronic postsurgical pain.
Efficacy of paravertebral block for breast surgery
For the traditional landmark based technique, block success rates for both lumbar and thoracic blocks have been reported to be over 90%. Two published meta-analyses have focussed on paravertebral blocks in the setting of breast surgery, and reported significantly lower postoperative pain scores for paravertebral block alone compared to general anaesthesia (GA) alone: < 2 h postop: -2.5 U (NRS, 0-10); 6, 7 < 24 h: -1.7 U; 6, 7 < 48 h: -1.8 U 6). Results were similar for paravertebral block combined with GA vs. GA alone. 6 Additionally, paravertebral block for breast surgery (as the sole anaesthetic technique or in combination with GA) reduces opioid requirements, and consequently lowers the postoperative nausea and vomiting risk. 6, 7 A recently published large retrospective analysis demonstrated that the addition of paravertebral block to GA for reconstructive mastectomy reduced length of hospital stay. 8 A recent randomised trial has also demonstrated that paravertebral block improves analgesia following simple breast augmentation. 18 In that study, the authors randomized 40 women undergoing bilateral breast augmentation to intraoperative wound site local infiltration, or preoperative bilateral paravertebral block. Surgery was conducted under propofol sedation without airway instrumentation. Paravertebral block was by a single T4 level injection of 20 mL ropivacaine 0.75%. The infiltration group received the same volume (20 mL x 2) of ropivacaine (presumably 0.75%). For the paravertebral group, propofol requirement was lower, intraoperative cooperation was better, PACU opioid use was lower, and average pain was reduced for the first 3 postoperative days.
Paravertebral block safety in breast surgery
The most commonly reported paravertebral block adverse events are vascular puncture (6.8%), hypotension (4%), epidural or intrathecal spread (1%), pleural puncture (0.8%) and pneumothorax (0.5%). 9 However, in the setting of breast surgery where patients are typically younger with better surface anatomy, the frequency of these adverse events is reported to be lower: temporary Horner´s syndrome occurs relatively commonly but one meta analysis revealed only one case of pneumothorax and one vascular puncture. 6 Another systemic review reported the most common adverse event as hypotension/bradycardia (n=11), presumably related to epidural LA spread. 7 These low complication rates confirm the safety of the technique for breast surgery; the ultrasound-guided technique could be expected to afford even greater safety. 10
Despite a growing body of evidence for paravertebral block, the optimal local anaesthetic dose (with or without LA additive) for breast surgery remains unknown. Most published reports have used 3-4 ml of ropivacaine or bupivacaine 0.375-0.5% per thoracic segment blocked. Furthermore, whether the optimal technique involves a single injection block, a multi injection (multi-level) block or a continuous technique also remains unknown. Subgroup analysis of one published meta-analysis demonstrated that multiple injections are more efficient than a single injection, but acknowledged that the multi injection technique might be associated with an increased risk of needle puncture related complications. 6
As mentioned above, paravertebral blocks provide effective pain control following breast surgery and three randomised trials have confirmed the assumption that this translates into a reduced risk of chronic postsurgical pain. 11-13 However, more trials focusing on this issue are needed.
Another emerging issue is the suggestion that paravertebral block reduces breast cancer recurrence risk. Exadaktylos and colleagues demonstrated in a retrospective analysis of 129 patients undergoing mastectomy and axillary clearance under either paravertebral block with GA or GA only, that paravertebral block was associated with a reduced rate of tumour recurrence and more frequent metastasis-free survival. 14 This might be explained by paravertebral block reducing cytokine alteration, which might be necessary in providing perioperative cancer immunity. 15 Additionally, the same authors showed that paravertebral block with propofol sedation inhibited the proliferation of oestrogen receptor-negative breast cancer cells to a greater extent than GA alone. 16 Currently, at least one large multicenter randomised controlled trial is investigating the risk of breast cancer recurrence following paravertebral block (and sedation) compared to GA alone, 17 and will go a long way in clarifying this important issue.
Thoracic wall blocks ("PECS" block)
Because of the previously described complications, many practitioners are not comfortable performing paravertebral block. In addition, paravertebral block will not provide complete sensory block to the anterior chest wall, as the chest is supplied not only from the thoracic spinal nerves, but also the brachial plexus via the medial and lateral pectoral nerves. Thoracic wall blocks ("PECS" block) have been recently described as an alternative peripheral nerve block to paravertebral block for providing both surgical anesthesia and postoperative analgesia for breast surgery. All rely on LA placement between the thoracic wall muscles. Thoracic wall blocks are to the chest what the TAP (transversus abdominis plane) block is to the abdomen. Like the TAP block, their introduction has been facilitated by the widespread availability of portable ultrasound. However, despite theoretical and anatomical arguments supporting their use for this surgery, at present, supportive clinical data is lacking.
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11. Kairaluoma PM, Bachmann MS, Rosenberg PH, Pere PJ. Preincisional paravertebral block reduces the prevalence of chronic pain after breast surgery. Anesth Analg 2006;103(3): 703-708.
12. ohom G, Abdalla H, O'Brien J, Szarvas S, Larney V, Buckley E, Butler M, Shorten GD. The associations between severity of early postoperative pain, chronic postsurgical pain and plasma concentration of stable nitric oxide products after breast surgery. Anesth Analg 2006;103(4): 995-1000.
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16. Deegan CA, Murray D, Doran P, Ecimovic P, Moriarty DC, Buggy DJ. Effect of anaesthetic technique on oestrogen receptor-negative breast cancer cell function in vitro. Br J Anaesth 2009;103(5): 685-690.
17. Sessler DI, Ben-Eliyahu S, Mascha EJ, Parat MO, Buggy DJ. Can regional analgesia reduce the risk of recurrence after breast cancer? methodology of a multicenter randomized trial. Contemporary Clinical Trials 2008;29(4): 517-526.
18. Gardiner S, Rudkin G, Cooter R, Field J, Bond M. Paravertebral blockade for day-case breast augmentation: a randomized clinical trial. Anesth Analg. 2012 Nov;115(5):1053-9.