Interscalene block:

The interscalene  approach to the brachial plexus targets the roots of the brachial plexus as they emerge between the scalene anterior and scalene medius muscle. 
It is a useful block to do for providing anaesthesia and analgesia for the shoulder and upper arm. 

The important neurovascular structures in the neck are quite close to target nerves.
Both these factors combine to make this the block with highest reported publications of complications in the literature. 

Anatomy
To understand the anatomy related to this block let us first see how the brachial plexus is formed:

The roots of the brachial plexus emerge between the two scalene muscles (scalene anterior and scalene medius). 
In the interscalene groove they lie on top (stack) of each other .
In the supraclavicular region the roots form the trunks which lie posterior and superior to the subclavian artery as it passess over the first rib.

To quote Dr Denny 'The brachial plexus can be likened to a vertical meat “baguette” placed in the neck. The back of the “baguette” is the Scalenus medius muscle. The front is the Scalenus anterior muscle, with the roots and trunks of the plexus forming the “meat” or filling of the sandwich or “baguette”, in between the 2 muscles, which insert onto the first rib.  It is long up and down and narrow front to back and not very deep. In fact it is more like a filled baguette than a sandwich, which rests on the first rib'.


Locating the nerves:
Start scanning in the supraclavicular fossa. 
Position the probe posterior to the clavicle so that a cross sectional view of the subclavian artery is obtained. 
You will notice the first rib inferior to the artery. 
It will be seen as a white line with a very dark background.  This is because rib does not allow any ultrasound to pass through it but reflects all the ultrasound incident on it. 
The periosteum of the rib appears as a white hyperechoic line with darkness behind it as no ultrasound reaches it. 
You will also notice the pleura on either side of the rib, inferior to it. 
The pleura is seen as a shimmering white line (comet tail appearance). 
The trunks of the brachial plexus will be seen as bunch of grapes posterior and superior to the subclavian artery.




Once the above has been identified start scanning cephalad keeping nerves in the centre of picture. 
You will see that the nerves which are bunched up behind the subclavian artery in the supraclavicular fossa stack up on top of each other as the probe is moved cephalad. 
The scalene anterior and scalene medius muscle lie on each side of the nerves with sternocleidomastoid lying over the nerve roots. 





As the roots are traced cephalad they will be seen disappearing into the vertebra. 



The video below explains this further:


Other nerves in the neck that can be identified are Dorsal scapular nerve, phrenic nerve, suprascapular nerve, superficial cervical plexus, supraclavicular nerves and the greater auricular nerve. 
To see these nerves a high end machine with a high frequency linear transducer is needed. 
To successfully perform an interscalene block it is not necessary to visualise all these nerves.

Dorsal scapular nerve:
This nerve will be seen  crossing the substance of scalene medius muscle. 



The following video shows this nerve passing through the substance of scalene medius muscle. 
This video also shows the spinal accessory nerve.


During in plane approach to the roots of the brachial plexus as the needle passess through the scalene medius muscle there is a possibility of this nerve getting damaged. 

Suprascapular nerve:
In the neck the suprascapular nerve can be seen arising from the C5 root as it is traced towards the supraclavicular fossa. 
The following video shows the suprascapular nerve arising from C5.



Indications:
Surgery on shoulder, upper arm and lateral elbow.

Contraindications:
1. Patient refusal
2. Coagulopathy
3. Infection at the block site.
4. Respiratory compromise: Interscalene block has potential to cause blockade of the phrenic nerve (almost 90% of cases) thus leading to hemidiaphragmatic paresis. 
This is poorly tolerated in patients who have pre-existing respiratory compromise. 
In these patients interscalene block should be avoided and an alternative block should be used like doing suprascapular nerve block for pain relief.

Necessary Equipment:
1. Ultrasound machine with high frequency probe, probe cover and ultrasound gel
2. Insulated stimulating needle (I use 50 mm stimulating needle).
3. Local anaesthetic: I use 20 ml of 0.5% levobupivacaine if block is done for anaesthesia.  For postoperative analgesia 0.25% levobupivacaine is also sufficient
4. 2% chlorhexidine

Performing the block:
Keep the patient supine with 45 degrees head up. 
Position the arm as shown in the picture. 
Stand at the head end on the side of shoulder to be blocked and position the machine on the opposite side.
Start scanning in the supraclavicular fossa.  Identify the subclavian artery. 
Look posterosuperior to the artery for the trunks of the brachial plexus.  Trace the trunks cephalad till the nerve roots are seen stacked up on top of each other. 
I use 50 mm insulated needle connected to the nerve stimulator.  Nerve stimulator is set at 1mA, 2 Hz. 



The needle is introduced in-plane so that the entire needle is visualised as it approches the roots.
I aim to have the ultimate position of the needle between the C5 and C6 nerve root. 
At this point either a biceps or a deltoid twitch is observed. 
The current is then reduced till threshold current between 0.3-0.5 mA is achieved and local anaesthetic is injected as shown in the animation below.
I combine ultrasound with nerve stimulation but my colleagues do the block only using ultrasound.
There is no evidence to suggest that combining the techniques improves safety. 
If the needle position is ideal even if the threshold current is high I inject local anaesthetic and observe it's spread.


The following video shows an interscalene block being done.  This video is by 'Nerve Imaging Group' and can also be seen on RA-UK website.





Useful References:

Classified according to

1.Approach used to perform Interscalene block
2.Needle Angle
3.Nerve identification
4.Local anaesthetic used
5.Adjuvants
6.Volume of local anaesthetic
7.Catheter

Approach
Classic Winnie
Winnie AP. Interscalene brachial plexus block. Anesthesia and analgesia 1970; 49 (3): 455-466.

Pippa technique (posterior approach)
Pippa P, Cominelli E, Marinelli C, Aito S. Brachial plexus block using the posterior approach. Eur J Anaesthesiol 1990;7:411–20

Meier technique
Meier G, Bauereis C, Heinrich C. Interscalene brachial plexus catheter for anesthesia and postoperative pain therapy. Experience with a modified technique. Der Anaesthesist 1997; 46: 715–9. (often quoted but unable to locate a copy in English hence used reference below)

Peripheral Regional Anesthesia: An Atlas of Anatomy and Techniques. Gisela Meier, Johannes Buettner. Thieme Medical Publishers. Aug 2007

Lateral modified
Borgeat A, Ekatodramis G: Anaesthesia for shoulder surgery. Best Pract Res Clin Anaesthesiol 2002; 16:211–25

Borgeat A, Dullenkopf A, Ekatodramis G, Nagy L. Evaluation of the lateral modified approach for continuous interscalene block after shoulder surgery. Anesthesiology 2003; 99: 436–42.

Paravertebral approach
Boezaart AP, Koorn R, Rosenquist RW. Paravertebral approach to the brachial plexus: an anatomic improvement in technique. Reg Anesth Pain Med 2003;28:241–

Posterolateral approach
Nguyen HC, Fath E, Wirtz S and Bey T. Transscalene Brachial Plexus Block: A New Posterolateral Approach for Brachial Plexus Block. Anesth Analg 2007;105:872–5

Needle angle
Sardesai A, Patel R, Denny NM, et al. Interscalene brachial plexus block: can the risk of entering the spinal canal be reduced? A study of needle angles in volunteers undergoing magnetic resonance imaging Anesthesiology 2006; 105: 9–13.
K. E. Russon, M. J. Herrick, B. Moriggl, H. J. Messner, A. Dixon, W. Harrop-Griffiths and N. M. Denny. Interscalene brachial plexus block: assessment of the needle angle needed to enter the spinal canal. Anaesthesia, 2009, 64, pages 43–45

Nerve identification
Prelocation
Urmey WF, Grossi P. Percutaneous electrode guidance: a non-invasive technique for prelocation of peripheral nerves to facilitate peripheral plexus or nerve block. Reg Anaesth Pain Med 2002; 27: 261–7

Nerve stimulator  

Baracco E, Verardo T, Scardino M, Geddo E. Brachial plexus block via the interscalene route. The value of a nerve stimulator. Apropos of 38 cases. Cahiers d’Anesthesiologie 1992; 40: 437–9

Liguori GA, Zayas VM, YaDeau JT, Kahn RL, Paroli L, Buschiazzo V, Wu A. Nerve localization techniques for interscalene brachial plexus blockade: a prospective, randomized comparison of mechanical paresthesia versus electrical stimulation. Anesth Analg 2006;103:761–7

Ultrasound

Perlas A, Niazi A, McCartney C, Chan V, Xu D, Abbas S. The sensitivity of motor response to nerve stimulation and paresthesia for nerve localization as evaluated by ultrasound. Reg Anesth Pain Med 2006; 31: 445 – 50

Sinh SK, Abrams JH, Weller RS. Ultrasound-guided interscalene needle placement produces successful anesthesia regardless of motor stimulation above or below 0.5 mA. Anesthesia Analgesia 2007; 105: 848–52.

Orebaugh SL, Williams BA, Kentor ML. Ultrasound guidance with nerve stimulation reduces the time necessary for resident peripheral nerve blockade. Regional Anesthesia and Pain Medicine 2007; 32: 448–54.

Kapral S, Greher M, Huber G, et al. Ultrasonographic guidance improves the success rate of interscalene brachial plexus blockade. Regional Anesthesia and Pain Medicine 2008; 33: 253-258

Liu SS, Zayas VM, Gordon MA, C. Beathe JC, Maalouf DB, Paroli L, Liguori GA, Ortiz J, Buschiazzo V, Ngeow J, Shetty T, Ya Deau YT. A Prospective, Randomized, Controlled Trial Comparing Ultrasound Versus Nerve Stimulator Guidance for Interscalene Block for Ambulatory Shoulder Surgery for Postoperative Neurological Symptoms. Anesth Analg 2009;109:265–71

Spence BC, Beach ML, Gallagher JD and Sites BD. Ultrasound-guided interscalene blocks: understanding where to inject the local anaesthetic. Anaesthesia, 2011, 66, pages 509–514

McNaught A, Shastri U, Carmichael N, Awad IT, Columb M, Cheung J, Holtby RM and McCartney CJL. Ultrasound reduces the minimum effective local anaesthetic volume compared with peripheral nerve stimulation for interscalene block. British Journal of Anaesthesia 2011; 106 (1): 124–30

Local anaesthetic

Al-Kaisy AA, Chan VWS, Perlas A. Respiratory effects of low-dose bupivacaine interscalene block. Br J Anaesth 1999; 82: 217 – 220 Borgeat A, Kalberer F, Jacob H, Ruetsch YA, Gerber C. Patient-controlled interscalene analgesia with ropivacaine 0.2% versus bupivacaine 0.15% after major open shoulder surgery: the effects on hand motor function. Anesthesia and Analgesia 2001; 92: 218–23.

Borghi B, Facchini F, Agnoletti V, A.Adduci, A.Lambertini, E.Marini, P.Gallerani, V.Sassoli, M.Luppi and A Casati. Pain relief and motor function during continuous interscalene analgesia after open shoulder surgery: a prospective, randomized, double-blind comparison between levobupivacaine 0.25%, and ropivacaine 0.25% or 0.4%. European Jourrnal of Anaesthesiology 2006; 23: 1005–9.

Adjuvants  
Dexamethasone
Effect of dexamethasone on the duration of interscalene nerve blocks with ropivacaine or bupivacaine. K. C. Cummings III, D. E. Napierkowski, I. Parra-Sanchez, A. Kurz, J. E. Dalton, J. J. Brems and D. I. Sessler British Journal of Anaesthesia 2011; 107 (3): 446–53

Clonidine

Culebras X, Van Gessel E, Hoffmeyer P, Gamulin Z. Clonidine combined with a long acting local anaesthetic does not prolong postoperative analgesia after brachial plexus block but does induce hemodynamic changes. Anesth Analg 2001; 92: 199–204.

Marco Nadig, Georgios Ekatodramis, and Alain Borgeat. What to Do with Clonidine with Long-Acting Local Anesthetic in Brachial Plexus Block? Anesth Analg July 2002 95:254

Opioid
Flory N, Van-Gessel E, Donald F, et al. Does the addition of morphine to brachial plexus block improve analgesia after shoulder surgery? Br J Anaesth 1995;75:23–6.

Volume of local anesthetic

Al-Kaisy A, McGuire G, Chan VW, Bruin G, Peng P, Miniaci A and Perlas A. Analgesic effect of interscalene block using low-dose bupivacaine for outpatient arthroscopic shoulder surgery. Regional Anesthesia and Pain Medicine 1998; 23: 469–73.

S. Riazi, N. Carmichael, I. Awad, R. M. Holtby and C. J. L. McCartney. Effect of local anaesthetic volume (20 vs 5 ml) on the efficacy and respiratory consequences of ultrasound-guided interscalene brachial plexus block. British Journal of Anaesthesia 2008; 101 (4): 549–56

Stimpson J, Carter J, Denny N. Interscalene Block and Phrenic Nerve Palsy. Br J Anaesth 2008; 16 November 2008.

Renes SH, Rettig HC, Gielen MJ, Wilder-Smith OH, van Geffen GJ. Ultrasound-guided low-dose interscalene brachial plexus block reduces the incidence of hemidiaphragmatic paresis. Reg Anesth Pain Med 2009; 34: 498 – 502


Catheter
Tuominen M, Pitkanen M, Rosenberg PH. Postoperative pain relief and bupivacaine plasma levels during continuous interscalene brachial plexus block. Acta Anaesthesiologica Scandinavica 1987; 31: 276–8.

Posterior approach
Boezaart AP, de Beer JF, du Toit C, van Rooyen K. A new technique of continuous interscalene nerve block. Canadian Journal of Anaesthesia 1999; 46: 275–81. (also describes benefit of using nerve stimulator)

Modified lateral approach for catheter insertion
Alain Borgeat, M.D., Alexander Dullenkopf, M.D., Georgios Ekatodramis, M.D., Ladislav Nagy, M.D. Evaluation of the Lateral Modified Approach for Continuous Interscalene Block after Shoulder Surgery. Anesthesiology 2003; 99:436 – 42

Tuohy needle
N. M. Denny, N. Barber and D. J. Sildown. Evaluation of an insulated Tuohy needle system for the placement of interscalene brachial plexus catheters Anaesthesia, 2003, 58, pages 554–557

Ultrasound guided catheter placement
Fredrickson MJ. The sensitivity of motor response to needle nerve stimulation during ultrasound guided interscalene catheter placement. Regional Anesthesia and Pain Medicine 2008; 33: 291–6.

Fredrickson MJ, Ball CM, Dalgleish AJ. A prospective randomized comparison of ultrasound guidance versus neurostimulation for interscalene catheter placement. Regional Anesthesia and Pain Medicine 2009; 34: 590–4.

Fredrickson MJ, Ball CM, Dalgleish AJ, Stewart AW, Short TG. A prospective randomized comparison of ultrasound and neurostimulation as needle end points for interscalene catheter placement. Anesthesia and Analgesia 2009; 108: 1695–700.

Ilfeld BM, Fredrickson MJ, Mariano ER. Ultrasound-guided perineural catheter insertion: three approaches, but few illuminating data. Regional Anesthesia and Pain Medicine 2010; 35: 565

Catheter and ambulation

Klein SM, Grant SA, Greengrass RA, et al. Interscalene brachial plexus block with a continuous catheter insertion system and a disposable infusion pump. Anesthesia and Analgesia 2000; 91: 1473–8.

Ilfeld BM, Morey TE, Wright TW, Chidgey LK, Enneking FK. Continuous interscalene brachial plexus block for postoperative pain control at home: a randomized, double-blinded, placebo- controlled study. Anesth Analg 2003; 96: 1089–95

Sardesai AM, Chakrabarti AJ, Denny NM. Lower lobe collapse during continuous interscalene brachial plexus local anesthesia at home. Regional Anesthesia and Pain Medicine 2004; 29: 65–8.

Ilfeld BM, Vandenborne K, Duncan PW, Sessler DI, Enneking KF, Shuster JJ, Theriaque DW, Chmielewski TL, Spadoni EH, Wright TW. Ambulatory continuous interscalene nerve blocks decrease the time to discharge readiness after total shoulder arthroplasty: a randomized, triple-masked, placebo-controlled study. Anesthesiology 2006; 105: 999–1007.  

Fredrickson MJ, Ball CM, Dalgleish AJ. Successful continuous interscalene analgesia for ambulatory shoulder surgery in a private practice setting. Regional Anesthesia and Pain Medicine 2008; 33: 122–8.  

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? Anesthesia and Analgesia 2008; 106: 991–6  

Patient controlled Interscalene analgesia vs PCA 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.

Borgeat A, Tewes E, Biasca N, Gerber C. Patient controlled Interscalene analgesia with ropivicaine after major shoulder surgery: PCIA vs PCA. BJA 1998; 81: 603.

Continuous infusion versus patient controlled Singelyn FJ, Seguy S, Gouverneur JM. Interscalene brachial plexus analgesia after open shoulder surgery: continuous versus patient-controlled infusion. Anesthesia and Analgesia 1999; 89: 1216–20.     .