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In their review of postoperative analgesia for shoulder surgery, Fredrickson et al. have focused on continuous interscalene techniques as the desired standard [1]. I have previously questioned the evidence surrounding this supposition [2]. Shoulder surgery is not always associated with severe pain and I would suggest that a perineural catheter infusion is not always required. Case selection has always been part of the art.

I am concerned that the authors suggested that alignment of the needle during interscalene block makes needle trauma almost impossible. The needle in any type of interscalene block is neither aligned with the nerve roots nor with the brachial plexus (Fig. 4) [3]. Fredrickson et al. did not demonstrate a difference in needle trauma rates from other published series [4] and I think that this contradicts their review. Alignment of the needle may lessen trauma to the nerve, but there is no published objective evidence for that hypothesis.

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Figure 4.  Coronal MRI of the brachial plexus in the supraclavicular fossa. Angle A–B: range of angles for emergence of nerve roots. Angle C–D: range of angles for insertion of interscalene block.

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Early reports regarding perineural infusions suggested lack of efficacy [5], and anecdotally leakage at catheter skin entry site was a problem. The subsequent success of boluses combined with low infusion rates may be due to the dynamics of spread along tissue planes to create a successful block, combined with less leakage dislodging the dressing and the catheter.

Refilling of elastomeric infusion devices is against manufacturers’ recommendations. Given that flow rate from these devices is not linear at the beginning or end of the infusion, I would suggest that it is unwise to risk inaccurate device performance characteristics on a second or even a third refilling.

The authors suggested that the axillary/suprascapular block combination is the preferred option for the respiratory cripple, given that the phrenic nerve is avoided, but this is a single-shot technique that may initially provide adequate analgesia for a situation with potentially significant ongoing analgesic requirements beyond the duration of the block. They may also have mentioned the small risk of pneumothorax from suprascapular nerve block.

The authors also noted a significant incidence of breathlessness (likely to reflect phrenic paresis) in healthy patients using continuous interscalene block. I wonder if the authors have any comment regarding the problem of breathlessness during continuous interscalene block.

No external funding and no competing interest declared. Previously posted at the Anaesthesia Correspondence website: http://www.anaesthesiacorrespondence.com.

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