Anesth Analg 2008; 107:726-727
© 2008 International Anesthesia Research Society
doi: 10.1213/ane.0b013e31817b67c1
LETTER TO THE EDITOR
Section Editor:
Lawrence Saidmanm
Continuous Interscalene Block for Open Shoulder Surgery
Klaus F. Hofmann-Kiefer, MD,
Tim Eiser, MD,
Daniel Chappell, MD,
Stephan Leuschner, MD,
Peter Conzen, MD, and
Dierk Schwender, MD
Clinic for Anesthesiology; University of Munich; Munich, Germany; klaus.hofmann-kiefer{at}med.uni-muenchen.de
In Response:
We disagree with McFarlane et al.1 concerning the quality of the interscalene blocks and the process of randomization and blinding.
General anesthesia was performed in both of the study groups and 0.002 mg/kg fentanyl was used to facilitate tracheal intubation. The mean total dose of fentanyl (0.26 ± 0.11 mg PCISB group) includes this intubation dose (mean 0.15 ± 0.06 mg in the PCISB group) and therefore is neither "curiously large" nor a reason to question the quality of the blocks.
The rate of catheter removals is frequently mentioned in investigations dealing with the interscalene technique and occurred only in 4 cases (=11%). This rate is not low, but clearly within the range of other investigations.2,3 Five (working) catheters had to be removed because of adverse effects of the block, in the majority of the cases because of dyspnea. Because hemidiaphragmatic paresis occurs in nearly 100% of patients receiving an interscalene block4,5 and causes relevant changes in pulmonary function, we not believe this incidence of "dyspneic patients" to be unexpectedly high in a study population with an average age of nearly 60 yr. We agree with Macfarlane and Brull that the integration of the "intention to treat principle" in the data analysis might have been advantageous in some aspects. However, as stated in the article,6 the patient’s characteristics of the withdrawn subjects did not differ significantly from patients who completed the study and therefore an influence on the study results is unlikely.
The investigation was blinded concerning our primary endpoint (Constant Scores). This is clearly stated in the methods section. In terms of pain assessment (secondary endpoint), blinding would have required the placing of placebo interscalene catheters. When balancing the risk of possible complications6 caused by those placebo catheters against the reliability of our results, placebo techniques did not seem appropriate. In addition, to our knowledge, placebo catheters have not been placed in any studies comparing patient controlled anesthesia and interscalene block in terms of pain management. Finally, we agree that further investigation is required to confirm whether PCISB can provide long-term benefit in shoulder surgery, but it did not improve early functional rehabilitation in the current study.
REFERENCES
- Macfarlane AJR, Brull R. Continuous interscalene block for open shoulder surgery. Anesth Analg 2008;107:726[Free Full Text]
- Koh DL, Lim BH. Postoperative continuous interscalene brachial plexus blockade for hand surgery. Ann Acad Med Singapore 1995;24:3–7[Medline]
- Delaunay L, Souron V, Lafosse L, Marret E, Toussaint B. Analgesia after arthroscopic rotator cuff repair: subacromial versus interscalene continuous infusion of ropivacaine. Reg Anesth Pain Med 2005;30:117–22[Web of Science][Medline]
- Urmey WF, Talts KH, Sharrock NE. One hundred percent incidence of hemidiaphragmatic paresis associated with interscalene brachial plexus anesthesia as diagnosed by ultrasonography. Anesth Analg 1991;72:498–503[Abstract/Free Full Text]
- Urmey WF, McDonald M. Hemidiaphragmatic paresis during interscalene brachial plexus block: effects on pulmonary function and chest wall mechanics. Anesth Analg 1992;74:352–7[Abstract/Free Full Text]
- Hofmann-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;106:991–6[Abstract/Free Full Text]
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