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Ultrasound-guided interscalene block with 5 or 20ml ropivacaine 0.5% was successful
- Colin J.L. McCartney, Sheila Riazi and Nicole M. Carmichael (2 December 2008)
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Interscalene Block and Phrenic Nerve Palsy
- James A Stimpson, Joseph Carter and Nicholas M. Denny (16 November 2008)
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Do we really need large volumes for US guided nerve blocks?
- Santhanam Suresh (10 October 2008)
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Reply to Dr. Chin
- Colin JL McCartney (10 October 2008)
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Does the low-volume interscalene block attenuate the severity of diaphragmatic paresis?
- Ki Jinn Chin (23 September 2008)
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Colin J.L. McCartney, Associate Professor Department of Anaesthesia, Sunnybrook Health Sciences Centre and University of Toronto, ON, Canada, Sheila Riazi and Nicole M. Carmichael
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To the Editor, Dr. Stimpson and colleagues state that successful interscalene brachial plexus block (ISBPB) can be defined “as a block that provides adequate anaesthesia for surgery OR postoperative analgesia”1. In our study2 an ultrasound-guided interscalene block with either 5ml or 20ml ropivacaine 0.5% resulted in 90% (36/40) of patients having a pain score of 0 in recovery room 30 minutes after painful shoulder surgery (17 in the 5ml volume and 19 in the 20ml volume groups respectively). In addition the recovery room oral morphine equivalent consumption was low in both groups with only 4/20 patients requiring analgesics in the low volume group (median 0 mg, range 0-20mg) and 3/20 patients in the normal volume group (median 0 mg, range 0-20mg). We would therefore state by the above definition that our technique was successful in both groups of patients. Intra-operative fentanyl was usually administered during induction and in our study was on average >2h before completion of surgery. The explanation for the good analgesia in recovery room is therefore unlikely to be related to the relatively small doses (maximum 200mcg) of intra- operative fentanyl in either group. We agree that it is perplexing as to how patients in our study can have preserved sensory function in the surgical dermatomes whilst maintaining good analgesia. However this author has seen many patients who have had regional techniques where no obvious sensory block is detectable yet good analgesia exists. Patients actually prefer to minimise motor and sensory block whilst maintaining pain relief and this may explain the greater satisfaction in the 5ml volume group in our study. In summary we proposed that a low volume ultrasound-guided ISBPB could produce successful pain relief with a reduction in respiratory compromise compared to a standard volume block? We maintain that the hypothesis was confirmed. References: 1. Stimpson J, Carter J, Denny N. Interscalene Block and Phrenic Nerve Palsy. Br J Anaesth 2008; 16 November 2008. 2. Riazi S, Carmichael NM, Awad I, Holtby R, McCartney CJL. Effect of local anaesthetic volume (20 vs 5ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block. Br J Anaesth 2008; 101, 549-56. Conflict of Interest:None declared |
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James A Stimpson, SpR Anaesthetics Queen Elizabeth Hospital, Kings Lynn, Joseph Carter and Nicholas M. Denny
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Editor - Riazi et al can be congratulated on attempting to find a technique of interscalene blockade that minimises the degree of phrenic nerve involvement, thus making it useful to those patients with limited pulmonary reserve. [1] This would seem to be a holy grail of interscalene blockade. We work in a unit that conducts almost all of its shoulder surgery on awake patients under interscalene brachial plexus blockade, and would like to express some concerns about this paper and the conclusions drawn from it by the authors. The primary outcome measure for this paper as stated in the methods was diaphragmatic movement 30 minutes after interscalene brachial plexus block, comparing a low dose (5mls) versus normal dose LA (20mls) technique. A secondary outcome measure stated in the title of the study is efficacy of block, as assessed by motor and sensory block onset and duration, and verbal response scale for pain. Successful interscalene brachial plexus block for shoulder surgery can be defined as a block that provides adequate anaesthesia for surgery or post-operative analgesia. This requires loss of sensation in the C5, C6 and C7 dermatomes for cutaneous anaesthesia, the C6 dermatome representing the osteotome of the shoulder, and biceps, deltoid and triceps motor loss as representing density of block within appropriate areas of the brachial plexus; variations on this have been in used in recent studies of interscalene blockade.[2][3][4] This has also been represented by blockade of the radial and median nerves,[5][6] or by shoulder abduction.[7] In our institution, confirmation of dermatomal anaesthesia and motor loss results in >90% success rate for a block suitable for awake shoulder surgery when conducted by a supervised trainee, and a subsequent zero opiate requirement for approximately 14-18 hours. Riazi et al elegantly describe their dermatomal and motor effects from interscalene blockade with the aid of column bar charts. These seem to show that of the 20 patients receiving ‘standard volume’ interscalene blocks at 30 minutes post-block, 7 patients had full C4 sensation, 7 had full C5 sensation, 13 had full C6 sensation and 18 had full C7 sensation. Of the same patients receiving ‘standard volume’, at 30 minutes post-block 11 had preserved deltoid movement, 13 had preserved biceps movement, and 12 had preserved triceps movement. This would suggest to us that at least one third of patients in the ‘standard volume’ group (and possibly up to two thirds of this group), did not have a successful interscalene brachial plexus block. As a recently published comparison, Kapral et al performed interscalene blockade with 20ml ropivacaine 7.5mg/ml using ultrasound guidance with a single failure, a success rate of 98.8%.[8] Within the low-volume group, it would appear that fewer patients had a successful interscalene brachial plexus block. Only 3 out of 20 patients achieved C5 sensory block, 2 C6 block, 0 C7 block, 4 deltoid motor block, 2 biceps motor block, and 2 triceps motor block at 30mins post-block. From our expectations and experience of a working interscalene block, a successful block may only have been achieved in 15% of patients. Given these results, it is perhaps no wonder that no attempt was made for awake shoulder surgery, or that during the surgery an average of 140.3ug fentanyl was used in the low volume group, and 107.5ug was used in the standard volume group, not including induction amounts. We would also make note of the standard deviation, implying that significantly larger amounts of intraoperative fentanyl was used for some patients. Nor is it surprising that recovery room morphine was required, or that in the post-operative 24 hours mean morphine equivalent requirement was 23.3mg in the low volume group and 26.5mg in the standard volume group. Again we note the high standard deviation; we presume that for some patients there was a significantly greater morphine requirement. Given this low incidence of successful interscalene block, we speculate that much of the phrenic nerve palsy may be related to spread of local anaesthetic within the fascial plane but not within the brachial plexus ‘sheath’, and that a low volume of non-interscalene local anaesthetic spreads less than a higher volume. Riazi et al conclude that their ‘study found that the use of a low volume ultrasound-guided interscalene brachial plexus block is associated with a lower incidence of phrenic nerve palsy and other block-related complications whilst maintaining effective analgesia compared with a standard-volume technique.’ Although the work of Riazi et al seems to be well constructed and the design of their phrenic nerve testing seems thorough and elegant, we feel that because of the high failure rate of the interscalene brachial plexus blocks in this study, any conclusions drawn about the incidence of phrenic nerve palsy after successful interscalene block are invalid. Riazi et al claim that their study demonstrates the potential benefit of low volume interscalene block for patients with limited pulmonary reserve. In our opinion and practice, these patients benefit from avoidance of general anaesthesia and opiate analgesia. Unfortunately, all patients in this study received both general anaesthesia and significant opiate analgesia, in conjunction with the risks of phrenic nerve palsy and pneumothorax of an interscalene brachial plexus block. Therefore we feel this claim is misleading. However, we strongly support research towards identification of a phrenic nerve sparing technique of interscalene blockade, and support the aims of this paper. J. Stimpson J. Carter N. Denny Kings Lynn, England References: 1 Riazi S, Carmichael N, Awad I, Holtby R, McCartney C. Effect of local anaesthetic volume (20 vs 5 ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block. Br J Anaesth 2008; 101: 549-56. 2 Casati A, Fanelli G, Cedrati V, Berti M, Aldegheri G, Torri G. Pulmonary function changes after interscalene brachial plexus anesthesia with 0.5% and 0.75% ropivacaine: A double-blinded comparison with 2% mepivacaine. Anesth Analg 1999; 88: 587-92 3 Hofman-Kiefer K, Eiser T, Chappell D, Leuschner S, Conzen P, Schwender D. Does patient-controlled continuous interscalene block improve early functional rehabilitation after open shoulder surgery? Anesth Analg 2008; 106: 991-996 4 Liguori G, Zayas V, YaDeau J et al. Nerve localization techniques for interscalene brachial plexus blockade: a prospective, randomized comparison of mechanical paresthesia versus electrical stimulation. Anesth Analg 2006; 103: 761-7 5 Borgeat A, Schappi B, Biasca N, Gerber C. Patient-controlled analgesia after major shoulder surgery: patient-controlled interscalene analgesia versus patient-controlled analgesia. Anesthesiology 1997; 87: 1343-7 6 Borgeat A, Ekatodramis G, Kalberer F, Benz C. Acute and nonacute complications associated with interscalene block and shoulder surgery. Anesthesiology 2001; 95: 875-80 7 Klein S, Grant S, Greengrass R et al. Interscalene brachial plexus block with a continuous catheter insertion system and a disposable infusion pump. Anesth Analg 2000; 91: 1473-8 8 Kapral S, Greher M, Huber G et al. Ultrasonographic guidance improves the success rate of interscalene brachial plexus blockade. Reg Anesth Pain Med 2008; 3: 253-8 Conflict of Interest:None declared |
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Santhanam Suresh, Pediatric Anesthesiologist Children's Memorial Hospital, Northwestern University, Chicago, IL
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I would like to commend Dr Riazi and colleagues on this attempt to reduce the volume of local anesthesia as well as measure the pulmonary functions. My practice is primarily limited to pediatric anesthesia. General anesthesia is the norm and this reduction of volume is something that we have routinely been practicing for the last two years using ultrasonography. The postoperative pain control has been comparable to the larger volumes we had used prior to the introduction of ultrasonography in our practice. This sets the stage for more rigorous testing and potential reduction of doses particularly in children where the margin of safety is small. The added advantage of maintaining adequate pulmonary function could allow this block to be used in patients with compromised function. Future studies using similar paradigms may lead to the realization that ultrasound guidance could indeed be the gold standard for regional anesthesia. Conflict of Interest:None declared |
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Colin JL McCartney, Associate Professor Department of Anesthesia, University of Toronto
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To the editor: Dr. Chin makes a valid point and we thank him for his letter in response to our study1. The author comments that our conclusions may not be justified because even the low volume (5ml) group had a 45% risk of phrenic palsy. Our results would then be meaningless if the magnitude of decrease in spirometry values were the same in all patients who developed phrenic palsy. The following table displays the characteristics of group I (all low volume), group Ia (low volume, no palsy), group Ib (low volume, palsy) and group II (high volume, all of whom developed phrenic palsy). Differences between group Ib (low volume, palsy) and group II (high volume) have been compared using t-tests. Significance is assumed at p<0.05. View Image Reassuringly it appears that even patients who get phrenic nerve palsy in the low volume group have significantly better preservation of lung function than the high volume group (see figure). This adds further weight to our conclusion that low volume (5ml) ultrasound-guided interscalene block provides equivalent analgesia but causes significantly less respiratory compromise compared to high (20ml) volume block. Figure legend: Comparison of reduction (%) in vital capacity between patients who received a high volume (20ml) and low volume (5ml) ultrasound -guided interscalene block with further subdivision of the low volume group into those who developed and those that did not develop diaphragmatic palsy as assessed by ultrasound. Median and interquartile range displayed. ‡Significant difference between the high volume and low volume, palsy groups (p=0.01). Reference: 1. Riazi S, Carmichael N, Awad I, Holtby RM, McCartney CJL. Effect of local anaesthetic volume (20 vs 5 ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block. Br J Anaesth 2008; 101; 549-56. C.J.L. McCartney, N.M. Carmichael, S. Riazi, I.T. Awad, Department of Anaesthesia, Sunnybrook Health Sciences Centre University of Toronto, ON, Canada Acknowledgement: The authors would like to thank Dr. Gordon Drummond, University of Edinburgh, for advice regarding spirometry data in relation to diaphragmatic palsy. Conflict of Interest:None declared |
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Ki Jinn Chin Department of Anesthesia,Toronto Western Hospital, Toronto, Ontario, Canada
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We commend Riazi et al (1) on their important study demonstrating that the analgesic effect of an interscalene brachial plexus block (ISBPB) may be achieved with an extremely low volume (5 ml) of local anesthetic, whilst simultaneously reducing the incidence of phrenic nerve palsy (from 100% to 45%). There were also significantly smaller reductions in mean spirometry values in the low-volume group. It is not clear however, if the low-volume technique achieved this by attenuating the severity of diaphragmatic paresis in patients that did develop phrenic nerve palsy (9/20); or whether this result was due primarily to normal or near-normal spirometry values in those patients who did not develop a palsy. It would be helpful if the authors reported the spirometric data separately in these 2 subgroups of patients who received the low-volume block. Without this information, the authors’ conclusion that a low-volume technique “may allow patients at higher risk of postoperative respiratory complications to undergo ISBPB” may not be justified. References 1. Riazi S, Carmichael N, Awad I, Holtby RM, McCartney CJL. Effect of local anaesthetic volume (20 vs 5 ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block. Br J Anaesth 2008; 101; 549-56. Conflict of Interest:None declared |
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