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| Frequently Asked Questions |
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| Category #6 - Blocks below the clavicle (SCB) |
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What corrections do you make with the needle and catheter when performing an infraclavicular block?
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Corrections, or redirections, are an essential component of successful peripheral nerve block placement. In fact, it is in cases when redirections are needed that a strictly landmark-based approach would result in block failure. The important point about redirecting a needle or catheter is to understand the relationship between the elicited and desired motor response, and to understand the changes necessary to achieve the desired response. In the case of an infraclavicular block, knowledge of the relationship of the brachial plexus cords is essential. Since the cords are named after their relationship to the 2nd portion of the axillary artery, we know that the posterior cord will be further posterior to the lateral cord, and will redirect in that manner if a lateral cord response is found while a posterior cord response is desired (see Reg Anesth Pain Med 2004; 29: 125 - 9).
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Which infraclavicular landmark do you find most reliable?
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We tend to use as many of the landmarks as is possible. Oftentimes, we will compare our peri-coracoid landmarks, our VIP landmarks, and a line from the interscalene groove to the deltopectoral groove. These landmarks all will typically result in a confluence of lines that outline the expected path of the brachial plexus. Doppler identification of the artery is also most useful for orientation. We have recently begun using a superior approach to the cords, in which we pass our needle directly over the clavicle at a point where the indentation just medial to the coracoid process sits (see "Anesthesia and Orthopaedic Surgery", Ed A P Boezaart, Chapter 24). This approach may offer the advantage of less patient discomfort due to the avoidance of penetrating the pectoral muscles, a more direct route to the posterior cord with less risk of axillary artery puncture, and a less acute angle to the plexus that might make catheter placement easier to accomplish. We are investigating this approach.
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What cord do you preferentially block when doing an infraclavicular block?
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The location and type of surgery dictates what cord we preferentially block. If the proposed surgery falls in the distribution of a particular cord, we block that cord first, or place a catheter on it. For single injection blocks, it is our practice to locate all three cords, or at least two of the three cords, inject on the cord that is most important for the surgery, then seek out the remaining cords and block them. We also have very good success when we block a combination of the posterior cord and one of the anterior cords (medial or lateral). (see Reg Anesth Pain Med 2004; 29: 125 - 9)
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How do you test your infraclavicular block?
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A method that we have been using with good success, for all blocks, utilizes a neuromuscular block nerve stimulator. We place the conducting pads in the nerve distribution of the proposed surgery. Next, we turn the current down to 0. While depressing the 50 Hz tetany switch in short bursts, we SLOWLY increase the current. This becomes uncomfortable for most patients at about 3-5 mA. If patients are not uncomfortable with a current of 15 mA, they will most probably tolerate a surgical stimulus. We have found this test to be helpful in gauging if the appropriate "soak-time" has elapsed, as well as relieving patient anxiety for a planned awake surgery. Often when the patient does not respond to cold or pin-prick testing, does the patient respond violently to surgical incision.
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What do you think of a transarterial approach to the infraclavicular block?
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If you are lucky the block may work, but I can almost guarantee you a failure if you don't have the appropriate muscle twitches. We don't want to rely on luck. These cords each lie in it's own fascia sheath. We don't try to get blood; if we do we regard it as a complication and then go to a different approach, i.e. supraclavicular or axillary. My advice to you is to forget that you ever heard about any trans-arterial techniques. Leave these for the amateurs.
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Can an infraclavicular block be used for gleno-humeral joint surgery? If yes, what are the concerns with the phrenic nerve? Please tell me a bit about the nerve supply of the shoulder joint.
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Of course infraclavicular block would be fine if combined with superficial cervical plexus block for the GH joint, since the axillary nerve supplies it. But if it involves the rotator cuff and subacromial and AC joints, you need to get the suprascapular nerve as well, which supplies the posterior parts of the rotator cuff, the subacromial joint and the AC joint. The articular branch of the lateral pectoral nerve, which comes off the lateral cord supplies the anterior parts of these joints, but remember that the medial pectoral nerve, which comes off the medial cord, has a connection to the lateral pectoral nerve. So ALL THREE the cords have to be blocked if the infraclavicular block is used for GH joint surgery (posterior goes to axillary, lateral to LPN and medial to MPN). Then the suprascapular nerve has to be blocked where it comes through the suprascapular notch - and the superficial cervical plexus for good measure. Then if you are totally confused - do a GA, but if the lungs are so screwed up that you don't want to do an interscalene, you probably don't want to do a GA as well.
Remember COPD is not really a problem with phrenic nerve paresis. The diaphragms are flat in any case due to the hyperinflation in COAD of the lungs so they don't really contribute to breathing. Granted it does not make the patient any better off to block their phrenics, but it likewise does not really harm them. Restrictive disease is, of course totally another story.
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