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Is PECS superior to PVB? Methodological flaws with study
ESRA Academy. Greengrass R. Mar 7, 2017; 170348
Roy Greengrass
Roy Greengrass
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In the abstract the authors state that the PEC II block was introduced to provide surgical anaesthesia and postoperative analgesia for breast surgery. Although PEC I and II blocks are useful for analgesia for some breast procedures, there is little evidence that they can provide primary anaesthesia for modified radical mastectomy.
Paravertebral block is an evidence-based procedure, which can provide primary anaesthesia for breast surgery procedures including modified radical mastectomy (1). In order that paravertebral block can provide primary anaesthesia or adequate analgesia, it is essential that multilevel paravertebral block be performed. Single injection paravertebral block has no evidence basis for primary anaesthesia since it is impossible to predictably block all roots in the surgical field using single injection techniques (2–4). By utilising a single injection PVB technique in this paper, the authors compared an unpredictable block with a different block for breast anaesthesia and analgesia.
In the introduction they state that: ‘Patients having mastectomy under PVB complain of axillary and upper limb pain because the medial and lateral pectoral nerves as well as the long thoracic and thoraco dorsal nerves are not blocked’. The latissimus dorsi, pectoralis and serratus muscles are not involved with primary mastectomy unless breast reconstruction is also performed.
In the methods for performance of PVB the authors describe a single level T3 block using a large volume (25 mL) of 0.5% ropivacaine. This technique has been reported in many articles to produce an unpredictable block, as well as presenting possible complications of significant epidural spread and local anaesthetic toxicity.
The authors described a successful block as ‘providing decreased sensation relative to dermatomes on the contralateral side’. Decreased sensation was not described further in the context of normal sensation versus hypalgesia or versus anaesthesia. Various states of decreased sensation do not imply adequacy for primary anaesthesia or analgesia.
All patients received general anaesthesia comprising of nitrous oxide and isoflurane, which creates nausea and vomiting and possibly (isoflurane) causes immunosuppression relating to metastatic spread of cancer (4). Combining regional blocks with general anaesthesia also leads to greater costs. Current norms of practice include regional plus propofol anaesthesia (5).
The primary outcome measured (duration of analgesia) was 3 hours with PVB versus 5 hours with PEC blocks which again confirmed inadequate analgesic methods as PVB have been reported to provide from 8 up to 24 hours of analgesia depending on the concentration of local anaesthetic used. The ‘significant difference’ of 2 mg of morphine used in 24 hours is clinically irrelevant, even for inadequate analgesic methods.
The VAS scores reported soon after surgery (4 versus 2) confirmed inadequate block.
In the discussion the authors report that PEC block with general anaesthesia does provide postoperative analgesia, which is true; however, it is unusual for PEC blocks to provide primary anaesthesia as discussed previously. There is no evidence that block of the latissimus and other muscles is essential for performance of breast surgeries not involving reconstruction, as stated previously.
The authors cite previous comparisons of unpredictable blocks (single injection at T4, etc) to support their data.
They also present and try to rationalise patient position, etc, to explain the spread of PVB; however, the evidence basis for multisegmental technique is not discussed.
The authors reflect on the possible impact of PEC blocks on chronic post-mastectomy pain. Evidence reporting less chronic pain (6) and less metastatic spread (7) after PVB unfortunately used only an unpredictable single injection technique. One can speculate that a multisegmental anaesthetic block may have provided a much greater benefit.
Single injection PVB is unpredictable and is thus almost always inadequate for anaesthesia/analgesia involving more than a few dermatomal segments. To continue to study and report this flawed methodology in comparison to other truncal techniques is unfortunate.

1. Weltz CR, Greengrass RA, Lyerly HK. Ambulatory surgical management of breast carcinoma using paravertebral block. Ann Surg 1995; 222(1): 19–26.
2. Naja ZM, El-Rajab M, Al-Tannir MA, et al. Thoracic paravertebral block: influence of the number of injections. Reg Anesth Pain Med 2006; 31(3): 196–201.
3. Marhofer D, Marhofer P, Kettner SC, et al. Magnetic resonance imaging analysis of the spread of local anesthetic solution after ultrasound-guided lateral thoracic paravertebral blockade: a volunteer study. Anesthesiology 2013; 118(5): 1106–12.
4. Benzonana LL, Perry NJ, Watts HR, et al. Isoflurane, a commonly used volatile anesthetic, enhances renal cancer growth and malignant potential via the hypoxia-inducible factor cellular signaling pathway in vitro. Anesthesiology 2013; 119(3): 593-605.
5. Looney M, Doran P, Buggy DJ. Effect of anesthetic technique on serum vascular endothelial growth factor C and transforming growth factor beta in women undergoing anesthesia and surgery for breast cancer. Anesthesiology 2010; 113(5): 1118–25.
6. Kairaluoma PM, Bachmann MS, Rosenberg PH, et al. Preincisional paravertebral block reduces the prevalence of chronic pain after breast surgery. Anesth Analg 2006; 103(3): 703–8.
7. Karmakar MK, Samy W, Li JW, et al. Thoracic paravertebral block and its effects on chronic pain and health-related quality of life after modified radical mastectomy. Reg Anesth Pain Med 2014; 39(4): 289–98.

BACKGROUND:

Pectoral nerve (PecS) block is a recently introduced technique for providing surgical anaesthesia and postoperative analgesia during breast surgery. The present study was planned to compare the efficacy and safety of ultrasound-guided PecS II block with thoracic paravertebral block (TPVB) for postoperative analgesia after modified radical mastectomy.

METHODS:

Forty adult female patients undergoing radical mastectomy were randomly allocated into two groups. Group 1 patients received a TPVB with ropivacaine 0.5%, 25 ml, whereas Group 2 patents received a PecS II block using same volume of ropivacaine 0.5% before induction of anaesthesia. Patient-controlled morphine analgesia was used for postoperative pain relief.

RESULTS:

The duration of analgesia was significantly prolonged in patients receiving the PecS II block compared with TPVB [mean (sd), 294.5 (52.76) vs 197.5 (31.35) min in the PecS II and TPVB group, respectively; P<0.0001]. The 24 h morphine consumption was also less in the PecS II block group [mean (sd), 3.90 (0.79) vs 5.30 (0.98) mg in PecS II and TPVB group, respectively; P<0.0001]. Postoperative pain scores were lower in the PecS II group compared with the TVPB group in the initial 2 h after surgery [median (IQR), 2 (2-2.5) vs 4 (3-4) in the Pecs II and TPVB group, respectively; P<0.0001]. Seventeen patients in the PecS II block group had T2 dermatomal spread compared with four patients in the TPVB group (P<0.001). No block-related complication was recorded.

CONCLUSIONS:

We found that the PecS II block provided superior postoperative analgesia than the TPVB in patients undergoing modified radical mastectomy without causing any adverse effect.

 

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