All Roads Do Not Lead to Rome
Borgeat, Alain M.D.
REGIONAL anesthesia has evolved in recent years from a technique into an art, practiced by some pioneering anesthesiologists. As with any art form, regional anesthesia has obtained a level of complexity not seen before. Until recently, regional anesthesia was used by a select group, using sophisticated wording and techniques that prohibited its widespread implementation. However, with the development of more reliable equipment and introduction of more effective local anesthetics, as well as improved techniques, this time is over. Any society starts with a theocracy and finishes in a democracy, as stated by Victor Hugo 150 yr ago. The democratization of regional anesthesia needs well-defined guidelines to ensure its safe, effective practice. As the number of anesthesiologists performing regional blocks increases, so may the number of serious complications. In this issue of Anesthesiology, Sardesai et al.1
makes a substantial contribution in regard to improving the safety of regional anesthesia.
The authors investigate the challenging question of whether the technical approach chosen to perform an interscalene block could influence the possibility of entering the spinal canal. The different angles necessary to gain access to the intervertebral foramen of the sixth cervical vertebra between the high and the classic lateral modified approach and the Winnie technique were compared in 10 healthy volunteers undergoing magnetic resonance imaging of their necks. The results of this investigation demonstrated that the Winnie approach had a shorter skin–intervertebral foramen distance and the smallest discrepancy angle. The latter finding is compelling because the smaller the discrepancy angle is, the easier it is to penetrate into the spinal canal through the intervertebral foramen. That is, the approach vector (direction of the needle) and the exit vector (angle at which the nerves are exiting the intervertebral foramen) have a higher degree of alignment with the Winnie technique.
William Halsted performed the first brachial plexus block in 1885. The technique involved surgical exposure of the brachial plexus with direct application of cocaine.2
The first recorded interscalene plexus block was most likely performed by July Etienne in 1925.2
He inserted a needle at the level of the cricothyroid membrane halfway between the lateral border of the sternocleidomastoid and the anterior border of the trapezius muscle to block the plexus.
The next improvement was made by Winnie.3
He was the first to recommend placing the needle within the interscalene groove after manual identification. The direction of the needle was perpendicular to the skin in every plane, pointing in a direction that is mostly medial, but slightly posterior and slightly caudad. The interscalene catheter is nowadays the accepted standard for perioperative and postoperative pain therapy after shoulder surgery. It offers better pain control, fewer side effects, earlier mobilization, and higher patient satisfaction.4–6
However, the use of the Winnie approach does not offer the best conditions for the placement of a catheter, because the direction of the needle is perpendicular to the trunks. Therefore, new approaches making its placement easier have been developed.7,8
Interestingly, changing the direction in a more caudad direction—within the tridimensional plane of the interscalene groove—was initially driven more to help catheter placement than to increase the safety of the technique.
Severe complications have been reported after interscalene block, including spinal9,10
or epidural anesthesia11,12
and even permanent loss of cervical cord function.13
Sardesai et al.1
provides substantial new information to have a better understanding of the occurrence of these complications. Although it seems obvious that directing the needle medially during performance of an interscalene block carries some risk, Sardesai et al.1
were able to demonstrate that the angle of approach for performing an interscalene block using the Winnie technique almost matches the angle made by the exiting nerve and neural foramen. These findings are clinically relevant because they clearly show that this technique has the greatest degree of alignment, making epidural, spinal, and intramedullary local anesthetic application a likely occurrence. It also enhances the risks of drug administration into the extraforaminal space. It is known that the neural sheath may extend to the paravertebral space. From there, the local anesthetic may diffuse from the paravertebral gutter through the intervertebral foramina to the epidural space and then reach the cerebrospinal fluid.14
This mechanism may explain some of the complications occurring with the Winnie approach.
Another important aspect of the investigation by Sardesai et al.1
is the demonstration that the shortest skin–intervertebral foramen was found with the Winnie technique. “Regionalists” already surmised this issue, because one recommendation is not to use a needle longer than 2.5 cm. This may be a safe precaution, but certainly not a panacea. The needle may be too short in patients with a thick neck or a generous fat layer. For the latter, it is often quite hazardous to try to anticipate the depth at which to expect to encounter the trunks. Moreover, the use of a short needle in this context will not be a definitive precaution to avoid drug administration within the extraforaminal space.
This investigation has some weaknesses. Detractors will still criticize the current study because of its small sample size, because the body mass index was not taken into account, and because the experimental conditions do not match the clinical reality. The latter point is certainly true with the new approaches,7,8
but is not far from the clinical reality when using the Winnie technique. This further highlights the potential danger associated with the classic Winnie technique.
What about the interscalene catheter? The results of this investigation let us fear that inadvertent catheterization of the epidural or spinal space can (too) easily occur. The catheter will go toward the direction of the needle. Sardesai et al.1
showed that the use of the Winnie technique gives the catheter good conditions to go through the intervertebral foramen.
Another issue is to consider whether the new approaches (direction of the needle more caudad) will create new complications, such as pneumothorax. It is still too premature to give a definitive response, but initial studies of interscalene single-shot and catheter have reported only one case of pneumothorax occurring in a patient with Marfan syndrome.7,15,16
Should the Winnie technique be avoided for interscalene block? When considering the results of Sardesai et al.1
and the safety of regional anesthesia, the answer is yes. First, alternatives do exist, because approaches that likely have a wider margin of safety have been described. Second, usual precautions, like the use of a short needle for performing this block, are not sufficient for all patients. Last, the safety margin is very small, an important issue for nonexperienced anesthetists. What about experienced anesthesiologists? Compared with nonexperienced colleagues, competent anesthetists have good tires to drive on an unsalted icy road, but the road is nevertheless still icy. It is therefore still recommended for all drivers to use the salted icy road! Primum non nocere.
Alain Borgeat, M.D.
Department of Anesthesiology, Orthopedic University Hospital Balgrist, Zurich, Switzerland. firstname.lastname@example.org
1. Sardesai AM, Patel R, Denny NM, Menon DK, Dixon AK, Herrick MJ, Harrop-Griffiths AW: 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
2. Winnie AP: Plexus anesthesia, Perivascular Techniques of Brachial Plexus Block. Philadelphia, WB Saunders, 1983
3. Winnie AP: Interscalene brachial plexus block. Anesth Analg 1970; 49:455–66
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5. Borgeat A, Tewes E, Biasca N, Gerber C: Patient-controlled interscalene analgesia with ropivacaine after major shoulder surgery: PCIA versus PCA. Br J Anaesth 1998; 81:603–5
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8. Borgeat A, Ekatodramis G: Anaesthesia for shoulder surgery. Best Pract Res Clin Anaesthesiol 2002; 16:211–25
9. Dutton RP, Eckhardt WF 3rd, Sunder N: Total spinal anesthesia after interscalene blockade of the brachial plexus. Anesthesiology 1994; 80:939–41
10. Passannante AN: Spinal anesthesia and permanent neurologic deficit after interscalene block. Anesth Analg 1996; 82:873–4
11. Kumar A, Battit GE, Froese AB, Long MC: Bilateral cervical and thoracic epidural blockade complicating interscalene brachial plexus block: Report of two cases. Anesthesiology 1971; 35:650–2
12. Mahoudeau G, Gaertner E, Launoy A, Ocquidant P, Loewenthal A: Interscalenic block: Accidental catheterization of the epidural space [in French]. Ann Fr Anesth Reanim 1995; 14:438–41
13. Benumof JL: Permanent loss of cervical spinal cord function associated with interscalene block performed under general anesthesia. Anesthesiology 2000; 93:1541–4
14. Purcell-Jones G, Pither CE, Justins DM: Paravertebral somatic nerve block: A clinical, radiographic, and computed tomographic study in chronic pain patients. Anesth Analg 1989; 68:32–9
15. Borgeat A, Ekatodramis G, Kalberer F, Benz C: Acute and nonacute complications associated with interscalene block and shoulder surgery: A prospective study. Anesthesiology 2001; 95:875–80
16. 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
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