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ƒ Editorials Sleeping Beauty or Big Bad Wolf? I s thoracic paravertebral block (TPVB) a neglected and underutilized technique, or is it too risky and unreliable to offer to our patients? At least 1 previous author has called it a “Sleeping Beauty” 1 and another called for its “revivifica- tion.” 2 In 1979, Eason and Wyatt 3 quoted from the then-current literature that “Thoracic paravertebral block is now of more interest to historians than to practical anaesthetists,” 4 while calling for its reappraisal. 3 To many, especially in the United States, it had in fact become a “Big Bad Wolf.” The main obstacles to its general and wide acceptance are probably linked to 3 facts: (1) a lack of absolute indications for this block, (2) the relative familiarity of practitioners with thoracic epidural block, and (3) the omnipresent fear of pneumothorax and subarachnoid injection. The more injections required to achieve satisfactory spread of the block, the larger the chance of pneumothorax and dural puncture. 1 Yet, when searching the literature, one is struck by the absence of reports of pneumothorax or subarachnoid block after TPVB. This situation may exist be- cause relatively few TPVBs, compared with other peripheral nerve blocks, have been performed since its reappraisal by Eason and Wyatt. 3 Another possibility is that mainly experts in the field perform this scary block, which has few good indications. A further possibility is that the cases of pneumothorax and subarach- noid block have simply not been reported, although this circumstance should have been reflected in reports on closed claims and other medicolegal cases, which it is not. The best explanation is that intrapleural injection, which may or may not be a frequent event during TPVB, does not necessarily equate to pneu- mothorax, and that most practitioners do not use sharp, thin needles that can easily penetrate the dura or visceral pleura. Pneumothorax should theoretically be less likely if blunt and large-bore Tuohy needles are used, as is usually the case. Pneumothorax will only occur if the visceral pleura is penetrated. Furthermore, the many excellent techniques and approaches described make penetration of the visceral pleura very unlikely, and the introduction of nerve stimulator–assisted technique by Lang 5 and Naja et al. 6 makes this possibility even more remote. Many anesthesiologists, however, fear that the more levels that are injected, the higher the risk of pneumothorax or dural puncture, and they correctly ask whether it is necessary to inject on multiple levels. 1 A typical question is whether the “blind” multiple-level placement of this block without the aid of a nerve stimulator is not simply a way of getting at least 1 or 2 of the multiple injections into the right space. The occasional intrapleural injection would most probably be without consequence, as long as the needle does not penetrate the lung. Similarly, the occasional injection outside the paravertebral space would have no effect. All that is needed is for at least 1 or more injections to be in the correct location. Would not a single needle or catheter correctly placed into the paravertebral space be sufficient instead? Naja and coworkers 7 attempted to answer this question by placing 4 needles on one side and 1, 2, or 3 injections on the opposite side and then evaluating the spread of local anesthetic agent clinically and radiologically. In this issue of Regional Anesthesia and Pain Medicine, Naja et al. 7 report on 368 safe paravertebral injections in 69 patients. Their investigation assessed early dermatomal distribution of block and also sought radiologic evidence of drug Accepted for publication February 7, 2006. doi:10.1016/j.rapm.2006.02.002 See Naja et al. page 196 Regional Anesthesia and Pain Medicine, Vol 31, No 3 (May–June), 2006: pp 189 –191 189

Sleeping Beauty or Big Bad Wolf?

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Page 1: Sleeping Beauty or Big Bad Wolf?

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Editorials

leeping Beauty or Big Bad Wolf?

s thoracic paravertebral block (TPVB) a neglected and underutilized technique,or is it too risky and unreliable to offer to our patients? At least 1 previous

uthor has called it a “Sleeping Beauty”1 and another called for its “revivifica-ion.”2 In 1979, Eason and Wyatt3 quoted from the then-current literature thatThoracic paravertebral block is now of more interest to historians than toractical anaesthetists,”4 while calling for its reappraisal.3 To many, especially inhe United States, it had in fact become a “Big Bad Wolf.” The main obstacles tots general and wide acceptance are probably linked to 3 facts: (1) a lack ofbsolute indications for this block, (2) the relative familiarity of practitioners withhoracic epidural block, and (3) the omnipresent fear of pneumothorax andubarachnoid injection. The more injections required to achieve satisfactorypread of the block, the larger the chance of pneumothorax and dural puncture.1

Yet, when searching the literature, one is struck by the absence of reports ofneumothorax or subarachnoid block after TPVB. This situation may exist be-ause relatively few TPVBs, compared with other peripheral nerve blocks, haveeen performed since its reappraisal by Eason and Wyatt.3 Another possibility ishat mainly experts in the field perform this scary block, which has few goodndications. A further possibility is that the cases of pneumothorax and subarach-oid block have simply not been reported, although this circumstance shouldave been reflected in reports on closed claims and other medicolegal cases,hich it is not. The best explanation is that intrapleural injection, which may oray not be a frequent event during TPVB, does not necessarily equate to pneu-othorax, and that most practitioners do not use sharp, thin needles that can

asily penetrate the dura or visceral pleura. Pneumothorax should theoreticallye less likely if blunt and large-bore Tuohy needles are used, as is usually the case.neumothorax will only occur if the visceral pleura is penetrated. Furthermore,he many excellent techniques and approaches described make penetration of theisceral pleura very unlikely, and the introduction of nerve stimulator–assistedechnique by Lang5 and Naja et al.6 makes this possibility even more remote.

Many anesthesiologists, however, fear that the more levels that are injected, theigher the risk of pneumothorax or dural puncture, and they correctly askhether it is necessary to inject on multiple levels.1 A typical question is whether

he “blind” multiple-level placement of this block without the aid of a nervetimulator is not simply a way of getting at least 1 or 2 of the multiple injectionsnto the right space. The occasional intrapleural injection would most probably beithout consequence, as long as the needle does not penetrate the lung. Similarly,

he occasional injection outside the paravertebral space would have no effect. Allhat is needed is for at least 1 or more injections to be in the correct location.

ould not a single needle or catheter correctly placed into the paravertebral spacee sufficient instead? Naja and coworkers7 attempted to answer this question bylacing 4 needles on one side and 1, 2, or 3 injections on the opposite side andhen evaluating the spread of local anesthetic agent clinically and radiologically.

In this issue of Regional Anesthesia and Pain Medicine, Naja et al.7 report on 368afe paravertebral injections in 69 patients. Their investigation assessed earlyermatomal distribution of block and also sought radiologic evidence of drug

Accepted for publication February 7, 2006. See Naja et al. page 196

doi:10.1016/j.rapm.2006.02.002

Regional Anesthesia and Pain Medicine, Vol 31, No 3 (May–June), 2006: pp 189–191 189

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190 Regional Anesthesia and Pain Medicine Vol. 31 No. 3 May–June 2006

pread. The results were assessed for anatomic correlation. Their main finding washat, within the constraints of their methodology, multiple paravertebral injec-ions (4 levels and 4 injections) gave more reliable distribution of nerve block thanid 1, 2, or 3 injections.However, potential methodological variations might have given different re-

ults. The clinical assessment of the nerve block was “within 10 minutes.” In aimilar study on paravertebral spread, Cheema et al.8 demonstrated that bupiva-aine requires approximately 40 minutes to achieve 95% of maximal block. Theumulative frequency of the number of blocked dermatomes in the study byheema et al.8 was only 10% to 15% after 10 minutes. Naja et al.,7 unfortunately,lso only refer to “local anesthetic agent” without stating which agent they used,nd this makes their clinical assessment at 10 minutes impossible to interpret. Thishort period might very well favor the multiple-injection technique. Also ofnterest is whether the study sides of 1, 2, or 3 injections were performed beforer after the 4-injection side and whether that order was randomized. These factorsould have made a significant difference in the assessment time and outcome ofblocked side, because, presumably, the 10 minutes was measured from the endf the total bilateral block as time zero. The time taken to perform the blocks onhe other side may have substantially influenced the results on the first sidenjected. For example, if the 4-injection control side was done first, the time takeno do the other side may have given the first side a significantly longer setup andpread time, which would have influenced the data considerably.

The authors used a distance of 2.5 to 3 cm from the midline for injection. Thisistance differs from that used by other anesthesiologist,9 of 2 to 2.5 cm from theidline. As the paravertebral space is small, 1-cm difference may influence theature of spread of the drug. With sufficient lateral needle placement, the blockould conceivably act more like an intercostal block, with more lateral spread andess longitudinal spread. A more medial injection, on the other hand, may favorepiduralization” of effects.An often-feared complication is subarachnoid injection. Although not formally

tudied in this context, most anesthesiologists realize that the nerve roots at thearavertebral level are covered with a sleeve of dura of varying length and thathis sleeve contains very little or no cerebrospinal fluid to warn of subarachnoideedle placement. Subarachnoid injection of large volumes of local anestheticgent can have devastating results. This dural sleeve essentially makes any para-ertebral block (cervical, thoracic, lumbar, and sacral) a block outside of the durar extradural or epidural. (Interestingly, a retrobulbar block is also essentially anpidural block, because it is injected just outside the dura surrounding the opticerve.) The same rules should, therefore, apply for any paravertebral block as forpidural block. Most anesthesiologists would use needles specifically designed noto penetrate the dura for paravertebral block. Naja and coworkers7 used annsulated 22-gauge needle (StimuPlex; B Braun AG, Melsungen, Germany) forheir TPVBs, but most anesthesiologists may feel safer using a Tuohy needle—fors personally, the larger the bore the better.Anesthesiologists have been using 16-gauge, 17-gauge, and 18-gauge needles

or many years in this anatomic area of the body when performing epidurallocks. Thus, use of these needles for paravertebral blocks should not be feared.hen selecting a needle for a paravertebral block (cervical, thoracic, lumbar, or

acral), anesthesiologists should ask themselves whether they would use the sameeedle for an epidural block. If the answer is no, they should probably also not use

t for paravertebral blocks for exactly the same reasons. Test dosing similar to thatustomarily used during epidural block should probably also be considered.Finally, many practitioners would criticize the use of bilateral TPVB instead of

horacic epidural block or other simpler blocks for surgical indications such asentral hernia. This criticism is fair, and we feel that performance of bilateral

PVB is seldom (if ever) justifiable, given the large volume of local anesthetic
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Thoracic Paravertebral Block • Boezaart and Raw 191

gent needed, the inherent, albeit small, danger of lung puncture or unrecognizedubarachnoid injection, and the 8 (4 � 4) versus 1 injection needed for thoracicpidural block. This block is ideally indicated for the treatment of intraoperativend postoperative pain associated with major unilateral breast or thoracic surgery andbdominal surgery in which the “renal” approach or subcostal incisions are used. Weo not feel it is indicated for surgery such as cholecystectomy and ventral hernia.uch simpler yet still effective alternatives exist for these conditions.We can reasonably conclude from the study by Naja et al.7 that multiple-level

aravertebral injections probably achieve faster and better block. Whether thisesult is important in cases in which general anesthesia is scheduled anyway isuestionable. The attraction of single injections is the fact they can be used foratheter placements and postsurgical maintenance of the paravertebral block fornalgesia. Furthermore, most anesthesiologists would instinctively feel that fewernjections present a lower risk of needle-associated complications.

In summary, Sleeping Beauty seems to have been given a magic kiss and maye waking up, and the Big Bad Wolf, although it threatened another fairy-taleharacter, seems to have finally been defeated. Thoracic paravertebral block is aafe and effective block, and, like any other block, given good and hard indica-ions, should be part of the repertoire of regional anesthesiologists. Even if nervetimulator–assisted and other good techniques are used, multiple-level injectionay be required if the block is used as sole anesthetic, but single-injection may be

ufficient for intraoperative and postoperative pain management. However, aody of experience exists in which single paravertebral injections were useduccessfully as sole anesthetic. This observation, and the belief among manynesthesiologists and surgeons that patients “do much better” with regionalnesthesia than with general anesthesia for major breast surgery, for example,equires further formal research. The excellent study by Naja and colleagues7 willo doubt inspire further research to validate their results and to increase ournderstanding of thoracic paravertebral blocks.

André P. Boezaart, M.D., Ph.D.Robert M. Raw, M.D.

Regional Anesthesia Study Center of Iowa (RASCI)Department of Anesthesia

University of IowaIowa City, IA

References

. Lönnqvist P-A. Entering the paravertebral space age again (editorial). Acta AnaesthesiolScand 2001;45:1-3.

. Renck H. Time for revivification of paravertebral block? Acta Anaesthesiol Scand 1995;39:1003-1004.

. Eason MJ, Wyatt R. Paravertebral thoracic block—a reappraisal. Anaesthesia 1979;34:638-642.

. Atkinson RS, Rushman GB. A Synopsis of Anaesthesia. 8th ed. Bristol, UK: Wright; 1977.

. Lang SA. The use of a nerve stimulator for thoracic paravertebral block (letter). Anes-thesiology 2002;97:521.

. Naja MZ, Zaide MF, Lönnqvist P-A. Nerve stimulator guided paravertebral blockade vs.general anesthesia for breast surgery: A prospective randomize trial. Eur J Anaesth2003;20:897-903.

. Naja ZM, El-Rajab M, Al-Tannir A, Zaide FM, Tayara K, Younes F, Lönnqvist P-A.Thoracic paravertebral blockade: Influence of the number of injections. Reg Anesth PainMed 2006;31:196-201.

. Cheema S, Richardson J, McGurgan P. Factors affecting the spread of bupivacaine in theadult thoracic paravertebral space. Anaesthesia 2003;58:684-711.

. Boezaart AP, Rosenquist RW. Paravertebral blocks. In: Brown DL, ed. Atlas of Regional

Anesthesia. 3rd ed. Philadelphia, PA: Elsevier Saunders; 2006: 271-275.