Infraclavicular block

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Introduction: SS ultrasound guided infraclavicular block is as effective as any other approach to brachial plexus bock for wrist and hand surgery, but is arguably the most simple and efficient. Experienced practitioners can perform ultrasound guided infraclavicular block in 2-3 mins, and relies on just advancing the needle through the fascia cephaloposterior to the axillary artery, and  depositing 30-35 mL of LA. Brachial plexus imaging is not an absolute requirement for successful brachial plexus block, therefore the technique is rarely limited by suboptimal patient ultrasonography e.g. obesity. Provided the needle remains lateral, pleural puncture is almost impossible and thus precise needle tip visualisation is not essential in avoiding pneumothorax. Infraclavicular block is also particularly suited to the supine position with the anesthesiologist in their usual position at the head of the bed/operating table. Relative contraindications to infraclavicular block are rare for elective surgery; the most common in our experience being a pacemaker in the path of the needle passage. Finally, compared to brachial plexus blocks above the clavicle, brachial plexus blocks below the clavicle result in lower peak local anesthetic plasma levels.  The chest wall also facilitates perineural catheter fixation (cf. the axilla).


Skill level: Simple.


Procedure time: 2-5 mins (2 mins for experienced practitioners)


Common indications: All surgical procedures involving the elbow/forearm/wrist and hand. For "major" procedures (e.g elbow reconstruction/replacement, radial/ulnar osteotomy, wrist fusion/replacement) consider infraclavicular catheter placement.


Sedation: e.g. midazolam 2 mg + alfentanil 250-500 mcg


Anatomy: Infraclavicular block is performed at the cord level of the brachial plexus located immediately around the 3rd part of the axillary artery (Fig. 1). The medial, lateral and posterior cord nomenclature refers to the cord positions relative to the axillary artery, however MRI studies have demonstrated the cords to be most commonly located between 3 and 11 o'clock on the clockface – typically posterior and cephalad to the artery. The axillary vein is typically caudad to the artery. Whilst the brachial plexus cords can be imaged in many patients, their visualisation is not necessary for infraclavicular block success. LA is simply deposited immediately posterior to the axillary artery. Placing the needle tip posterior to the artery requires penetration of a fascial layer located cephaloposterior to the artery. Pectoralis major and minor lie superficial to the artery, while the scapula is llocated posterior to the artery. Medially are the ribs and pleura. 


brachial plexus

Fig. 1. Brachial plexus anatomy relevant to infraclavicular block. The cords are most commonly located both posterior and cephalad of the 3rd part of the axillary artery (occassionally the lateral cord is located on the caudal/anterior surface of the artery). Note that pleural puncture is exceedingly unlikely if the needle is kept lateral (or superficial if medially placed). 


Surface landmarks: mark out clavicle.


Needle: 6-8 cm 18G Tuohy needle (depending on patient weight: usually 8 cm; < 70 kg, 6 cm may be long enough). Prepare a single or multi-orifice catheter if necessary (see "perineural catheter technique").

 

Setup

1. Curvilinear low frequency (5-8 MHz) probe e.g. Sonosite C11. A linear probe can be used, but it can be problematic achieving good skin-probe contact within the concave deltopectoral groove, and needle access between the probe and clavicle.

2. 6-8 cm Tuohy needle.

3. 30 mL LA filled syringe


Procedure (Video 1, 2)

1. Place a pillow under the shoulder blades to reduce the concavity of the deltopectoral groove (the depression just caudad to the clavicle and medial to the coracoid processs of the scapula). This facilitates probe/needle access to the area. Ask patient to turn the head to the contralateral side.

2. Place the probe just medial to the coracoid process but as far caudad in the deltopectoral groove as possible and aim to visualise the axillary artery. Tilt the probe in a medial-lateral direction and slide medially-laterally-medially to obtain the best image of the axillary artery. Brachial plexus cord visualisation may be possible, but is not necessary. Probe orientation is sagittal  but angled towards the elbow. Picture in one's mind the probable direction of the plexus (Fig. 1) as probe orientation should be directly perpendicular to this direction. The cords are hyperechoic in relation to the surrounding tissue, although their visualisation is not necessary to achieve a high success rate as it is essentially a perivascular technique.

3. Needle entry point is just caudad of the clavicle angled 45-60 degrees to the skin and as far cephalad of the probe as possible (increasing the distance from probe to skin puncture site will improve needle tip/shaft visualisation by promoting a needle orientation more perpendicular to the US beam) (Fig. 2).


needle-probe orientation for ultrasound guided infraclavicular block

Fig. 2. Infraclavicular block: probe placement in/medial to the deltopectoral groove. Needle entry point is as cephalad as possible (just caudad to clavicle).

 

4. First infiltrate the skin, subcutaneous fat, pectoralis major and minor muscle under US guidance using an in-plane needle-probe alignment along the intended needle tract with a 22-25G hypodermic needle and 5 mL lidocaine 1%.

5. Nerve stimulation is not necessary for the SS infraclavicular technique (it relies on just penetrating the fascia cephaloposterior to the axillary artery and observation of LA spread posterior to the artery), but nerve stimulation can be useful for the continuous technique to confirm needle-cord proximity. Set to 0.8-1 mA, pulse width 0.1 ms and 2 Hz and aim to briefly elicit any distal (wrist/hand) motor response.

6. With a 30 ml LA filled syringe attached directly to the Tuohy needle, advance the needle through the pectoralis major and minor and then past the cephalad side of the artery (Fig. 3).

 

Ultrasound guided infraclavicular block

Fig. 3. Infraclavicular block: third part of the axillary artery ("A") and associated structures. Superficial to artery is pectoralis major and minor. Blue arrow=needle shaft with tip adjacent probable medial cord. Red arrow=fascial layer cehaloposterior to artery, which must be penetrated before LA deposition.


7. Penetrate the fascia just cephaloposterior to the axillary artery (always associated with a "pop" when using an 18G Tuohy needle – but this requires a short, sharp deliberate needle movement once the needle tip is against the fascia).

8. Once through the fascia, reposition needle tip (injecting a few mL of LA if necessary to facilitate needle tip approximation) until the needle tip is just underneath (posterior to) the axillary artery.

9. Inject 30 mL LA aiming to observe injectate spread immediately under (posterior) to the axillary artery.

For infraclavicular catheter placement:

10.Once appropriate needle tip position has been confirmed just posterior to the artery, drop the probe, and stabilise this needle position by transferring the hand previously holding the probe to the needle hub. Disconnect syringe and advance the catheter with the catheter advancing piece sited within needle hub. Advance catheter 5 cm beyond needle tip.

11. Withdraw needle over the catheter. Infraclavicular catheters do not carry the same risk (e.g. as interscalene catheters) of dislocation; therefore, stabilisation of catheter prior to fixation by pressing catheter against the skin with a finger at the skin entry point is generally not necessary.

12. Withdraw infraclavicular catheter to 1.5 cm beyond original needle tip position (the proximal orifice of a triple orifice catheter is 1.4 cm proximal to the catheter tip) e.g. needle depth 6 cm, then fix at 7.5 cm. Be very careful during the last cm of catheter withdrawal as the catheter can have a tendancy to spontaneously dislocate at this point.

13. Carefully apply medical cyanoacrylate (e.g. dermabond) to the skin entry site (aids secural and minimises LA leakage).

14. Apply tincture of benzoin or "Skin-Prep" to 2 cm radius of skin around catheter puncture site (improves Lockit-skin adhesion).

15. Apply Lockit catheter fixation device

16. Dress infraclavicular catheter after surgery as described in catheter fixation.


Local anesthetic regimen: 30 mL LA via catheter e.g 20 mL ropivacaine 0.75% + 10 mL lidocaine 2%.


Specific Complications

1. Pheumothorax. Very unlikely if the needle is maintained lateral (outer half of clavicle), or if relatively medial, kept appropritely superficial (not more than 1 cm deep to the posterior aspect of axillary artery).

2. Intraneural injection. Exceedingly unlikely when using an 18G Tuohy needle.


Clinical PEARLS

 1. Needle shaft/tip visualisation can be difficult using the in-plane infraclavicular approach because being a deep block, and using the common approach of puncturing the skin caudad to the clavicle, the needle assumes an orientation that is not perpendicular to the US beam (i.e. more parallel to the US beam). It is therefore often poorly visualised. "Jiggling" the needle back and forth and injecting 1 mL aliquots of injectate can assist needle tip approximation. Also consider using an echogenic Tuohy needle (e.g. Pajunk echogenic Tuohy needle).

 2. For infraclavicular catheter placement:

a) Consider using concomitant neurostimulation and/or the out-of-plane technique using a similar probe position but a needle puncture site medial to probe and directed towards the axilla. We are currently evaluating this approach as our experience for other perineural catheter approaches generally supports the out-of-plane approach with a needle orientation in the direction of the target neural structure (see "perineural catheter technique"). With this approach, pneumothorax is exceedingly unlikely as the needle is orientated away from the pleura (Video 3). Take care to avoid puncturing a superficial vessel, as needle advancement is initially remote from the area directly in front of (deep to) the ultrasound beam (i.e. "blind"). An alternative technique combining the stated theoretical advanges of both the in-plane and out-of-plane techniques is to rotate the probe around its long axis (the axis of the probe cord) just before the oval transverse image of the artery disappears (clockwise rotation for the right side; anticlockwise rotation for the left side). The probe beam will thus be orientated more in-line with the plexus direction into the axillary tunnel. Needle advancement can therefore be kept in-plane, while the needle will also be orientated more or less in the direction of the plexus.    

b) Follow the general recommendations under perinerual catheter technique.

c) In our experience, an infraclavicular 2 mL/hr background infusion with PRN hourly 5 mL boluses of ropivacaine 0.2% (e.g. PainBuster elastomeric pump) provides potent analgesia, but often excessive motor block. When early active mobilisation is to be used, we usually clamp the infusion off and advise the patient to activate the infusion if their pain score (0-10) exceeds 2-3.

3. Infraclavicular block sonography demonstrates the phenomenom of acoustic enhancement deep to an anechoic structure. A hyperechoic area is often seen posterior to the artery, which may be interpreted as the posterior cord, when in fact it usually represents artefact. 

 

 

 Videos


Video 1. Infraclavicular block. Note: 1. US machine as close to the patient as possible, 2. Pillow under shoulder blades, 3. Short, sharp needle movement to penetrate the fascia cephaloposterior to the axillary artery.



 

Video 2. Infraclavicular block (ultrasound). The steep needle angle makes needle shaft/tip visualisation challenging: observe tissue displacement with needle advancement. Note LA expanding the space posterior to the artery ("double bubble sign": one bubble=the artery, one bubble=LA)



 

Video 3. Out-of-plane infraclavicular catheter placement. The approach has similarities to "oblique" out-of-plane femoral catheter placement: needle tip access to the posterior aspect of the artery is facilitated by approaching the artery "obliquely" (in this case from cephalad). Once the needle is walked down to the appropriate depth, it is then "angled" under the artery. This approach has the advantage that the catheter is orientated in the direction of the plexus; thus, catheter threading distance is less important, and the area of catheter in proximity to the plexus is theoretically increased.