Letters to the Editor
Regional Anesthesia and Pain Medicine • Volume 40, Number 4, July-August 2015
Thomas Fichtner Bendtsen, MD, PhD Department of Anesthesia Aarhus University Hospital Aarhus, Denmark
Bernhard Moriggl, MD, PhD Department of Anatomy Histology and Embryology Medical University of Innsbruck Innsbruck, Austria
Vincent Chan, MD Department of Anesthesia Toronto Western Hospital University of Toronto Toronto, Ontario, Canada
Jens Børglum, MD, PhD Department of Anesthesia Copenhagen University Hospital Roskilde Roskilde, Denmark
The authors declare no conflict of interest.
REFERENCES 1. Cowlishaw P, Kotze P.Adductor canal block—or subsartorial canal block? Reg Anesth Pain Med. 2015;40:175–176. 2. Standring S. Gray’s Anatomy—The Anatomical Basis of Clinical Practice. 40th ed. Edinburgh, Scotland: Elsevier Churchill Livingstone; 2008. 3. Thiel W. Photographischer Atlas der Praktischen Anatomie. Berlin, Germany: Springer; 1996.
FIGURE 1. At different levels from the anterior superior iliac spine (ASIS) at A1 to the base of the patella at H1, the figure displays anatomical cross sections (A2–H2) in a cadaveric lower limb. A2 is a cross section of the ASIS. B2 intersects the iliopectineal fossa and the upper border of the greater trochanter. C2 is at the apex of the iliopectineal fossa. D2 corresponds to the midpoint between the ASIS and the base of the patella (the green line in D1 connects the ASIS and the base of the patella). E2 intersects the apex of the femoral triangle where the saphenous nerve and the femoral vessels exit the femoral triangle and enter the adductor canal. F2 is at the midpoint of the adductor canal. G2 is at the top of the adductor hiatus, which is the distal end of the adductor canal. H2 is at the base of the patella. In all sections, arteries are red, veins are blue, nerves are yellow, sartorius muscle is red, and the adductor longus muscle is purple. The iliopsoas muscle is green in cross sections A2–B2, the adductor magnus muscle is greenish-blue and only colored in cross sections E2–F2, the pectineus muscle is also greenish-blue and only colored in cross section B2, vastoadductor membrane is white in cross sections E–G, patella is green in cross section H2. The part of the adductor longus underneath the sartorius muscle is indicated by orange in E1. Modified excerpt from VH Dissector with permission from Touch of Life Technologies Inc (www.toltech.net). Built on real anatomy from the National Library of Medicine’s Visible Human Project.
they observed dye spread distal to the top of the adductor hiatus in only 1 cadaver,1 which suggests inadequate spread to fill the adductor canal in a high proportion of the cases. Ultrasound-guided injection into the true adductor canalwas described by Manickam et al.6 However, ultrasound-guided subsartorial blockade of the saphenous nerve can be achieved at any level from the apex of the iliopectineal fossa—inside the femoral triangle—to the distal end of the adductor canal. For a large volume saphenous nerve
392
block, local anesthetic injection in the femoral triangle may also block some of the femoral nerve branches to the vastus medialis muscle (Fig. 1D2), and injection in the true adductor canal may block the posterior branch of the obturator nerve if this branch passes through the adductor hiatus into the popliteal fossa.7 However, ultrasound guidance to block the saphenous nerve subsartorially and to block the obturator nerve in the subinguinal region with small volumes of local anesthetic is probably the most effective approach to block both nerves.
4. Tubbs RS, Loukas M, Shoja MM, Apaydin N, Oakes WJ, Salter EG. Anatomy and potential clinical significance of the vastoadductor membrane. Surg Radiol Anat. 2007;29: 569–573. 5. Gray H. Anatomy—Descriptive and Surgical. 17th ed. Philadelphia, PA: Lea and Febiger; 1908. 6. Manickam B, Perlas A, Duggan E, Brull R, Chan VW, Ramlogan R. Feasibility and efficacy of ultrasound-guided block of the saphenous nerve in the adductor canal. Reg Anesth Pain Med. 2009;34:578–580. 7. Kumka M. Critical sites of entrapment of the posterior division of the obturator nerve: anatomical considerations. J Can Chiropr Assoc. 2010;54:33–42.
Reply to Dr Bendtsen Accepted for publication: April 23, 2015. To the Editor: e thank Dr Bendtsen and colleagues for their thorough description of the femoral triangle and adductor canal.1 This correlates well with our understanding of the anatomy of the anterior thigh. We do not disagree that the vastoadductor membrane forms the roof of the adductor canal
W
© 2015 American Society of Regional Anesthesia and Pain Medicine
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
Regional Anesthesia and Pain Medicine • Volume 40, Number 4, July-August 2015
or that the adductor canal is a continuation of the femoral triangle. The important point that we,2 Tubbs et al,3 and Dr Bendtsen et al make is that “The vastoadductor membrane effectively creates a subcompartment within the subsartorial canal.”3 The vastoadductor membrane separates the subsartorial plexus from the saphenous nerve contained in the “adductor canal proper” as stated in Dr Bendtsen’s aforementioned correspondence. Hence, there is a subsartorial space (or canal, if we may) containing a neural plexus that needs to be considered when providing lower limb analgesia/anesthesia. The other point we made2 is that the commencement and length of the adductor canal are highly variable. Tubbs’ dissection study reported a range of 20 to 32 cm for the former (from the anterior superior iliac spine to the proximal border of the vastoadductor membrane) and 5.5 to 15 cm for the latter.2 Thus, it is highly probable that many clinicians are injecting superior to the adductor canal when performing an adductor canal block. As our letter states, we insert our catheter in to the femoral triangle using an easily definable sonoanatomical end point. Injection of dye at this point results in minimal spread superiorly and consistent spread inferiorly, posterior to the sartorius. These results are consistent with the anatomical dye study of Ishiguro et al.4 We routinely insert femoral nerve catheters at this position for patients undergoing knee replacement surgery. In our experience, a continuous catheter infusion of 5 to 10 mL of 0.2% ropivacaine produces reliable analgesia of the knee, with preservation of quadriceps strength. Patients routinely walk within 24 hours of surgery. To reiterate, we believe that it is important to achieve subsartorial spread of local anesthetic anterior and posterior of the vastoadductor membrane to provide excellent analgesia for knee arthroplasty surgery. We suggested the term “subsartorial canal block” to encompass the subsartorial space and not just the “adductor canal proper.” However, we accept that there remains some ambiguity of terminology. Phillip Cowlishaw, MBChB Mater Hospitals, Stanley St, Brisbane Queensland, Australia
Pierre Kotze, MBChB Mater Hospitals, Brisbane Queensland, Australia
The authors declare no conflict of interest. REFERENCES 1. Bendtsen TF, Moriggl B, Chan V, Børglum J. Basic topography of the saphenous nerve in the
femoral triangle and the adductor canal. Reg Anesth Pain Med. 2015;40:391–392. 2. Cowlishaw P, Kotze P. Adductor canal block—or subsartorial canal block? Reg Anesth Pain Med. 2015;40:175–176. 3. Tubbs RS, Loukas M, Shoja MM, Apaydin N, Oakes WJ, Salter EG. Anatomy and potential clinical significance of the vastoadductor membrane. Surgical and radiologic anatomy. Surg Radiol Anat. 2007;29:569–573. 4. Ishiguro S, Yokochi A, Yoshioka K, et al. Technical communication: anatomy and clinical implications of ultrasound-guided selective femoral nerve block. Anesth Anal. 2012;115:1467–1470.
Perineural Versus Systemic Dexamethasone Questions Remain Unanswered Accepted for publication: April 10, 2015. To the Editor: e read with interest the recent article by Abdallah et al1 comparing intravenous and perineural dexamethasone. The study found that perineural and intravenous dexamethasone similarly prolong the analgesic duration of bupivacaine supraclavicular brachial plexus blocks. We applaud the authors’ effort to answer this important clinical question. However, as noted by the authors, the chosen dose of dexamethasone 8 mg IV may be sufficient to mask the true site of action. A meta-analysis by De Oliveira et al2 in 2011 found systemic doses of dexamethasone greater than 0.1 mg/kg provide significant analgesia and reduced opioid consumption postoperatively. This study1 as well as others3 comparing intravenous to perineural dexamethasone have all examined high doses of dexamethasone that are likely close to 0.1 mg/kg. Conversely, a recent randomized, placebo-controlled trial of 39 patients receiving interscalene nerve blocks with ropivacaine 0.75% (20 mL) randomized patients to block alone, block with intravenous dexamethasone, or block with perineural dexamethasone.4 They found that a 4-mg dose of perineural dexamethasone prolonged analgesia longer than intravenous dexamethasone. Furthermore, block alone was not significantly different than block with intravenous dexamethasone. The minimum dose of intravenous dexamethasone sufficient to prolong the duration of peripheral blockade remains unknown. Recent evidence suggests, however, that the perineural dose of dexamethasone sufficient to prolong the duration of peripheral blockade is less than what was
W
© 2015 American Society of Regional Anesthesia and Pain Medicine
Letters to the Editor
previously thought. A recent study published by Liu et al5 compared the duration of supraclavicular block with bupivacaine 0.25% alone, to bupivacaine plus dexamethasone dosages of 1, 2, and 4 mg. The study demonstrated that low-dose perineural dexamethasone, 1 to 2 mg, similarly prolonged the duration of bupivacaine supraclavicular brachial plexus block as compared with 4 mg. In this study, dexamethasone prolonged the duration of bupivacaine 0.25% for supraclavicular block by greater than 10 hours. These data are more consistent with a locally mediated effect as opposed to a systemically mediated effect. Additionally, laboratory data from Williams et al6 have indicated that lower doses of perineural dexamethasone combined with ropivacaine have a neurotoxicity profile comparable to ropivacaine alone. It is possible, if not likely, that studies supporting a systemically mediated mechanism of action have incorporated dosages adequate to exert both systemic and local effects. Additional studies incorporating lower dosages of dexamethasone may more accurately reflect the site of action whereby dexamethasone prolongs the duration of peripheral nerve blockade. Eric D. Bolin, MD Sylvia Wilson, MD Department of Anesthesia and Perioperative Medicine Medical University of South Carolina Charleston, SC
The authors declare no conflict of interest. REFERENCES 1. Abdallah FW, Johnson J, Chan V, et al. Intravenous dexamethasone and perineural dexamethasone similarly prolong the duration of analgesia after supraclavicular brachial plexus block: a randomized, triple-arm, double-blind, placebo-controlled trial. Reg Anesth Pain Med. 2015;40:125–132. 2. De Oliveira GS Jr, Almeida MD, Benzon HT, McCarthy RJ. Perioperative single dose systemic dexamethasone for postoperative pain: a meta-analysis of randomized controlled trials. Anesthesiology. 2011;115: 575–588. 3. Desmet M, Braems H, Reynvoet M, et al. I.V. and perineural dexamethasone are equivalent in increasing the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder surgery: a prospective, randomized, placebo-controlled study. Br J Anaesth. 2013; 111:445–452. 4. Kawanishi R, Yamamoto K, Tobetto Y, et al. Perineural but not systemic low-dose dexamethasone prolongs the duration of interscalene block with ropivacaine: a
393
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
Regional Anesthesia and Pain Medicine • Volume 40, Number 4, July-August 2015
Thomas Fichtner Bendtsen, MD, PhD Department of Anesthesia Aarhus University Hospital Aarhus, Denmark
Bernhard Moriggl, MD, PhD Department of Anatomy Histology and Embryology Medical University of Innsbruck Innsbruck, Austria
Vincent Chan, MD Department of Anesthesia Toronto Western Hospital University of Toronto Toronto, Ontario, Canada
Jens Børglum, MD, PhD Department of Anesthesia Copenhagen University Hospital Roskilde Roskilde, Denmark
The authors declare no conflict of interest.
REFERENCES 1. Cowlishaw P, Kotze P.Adductor canal block—or subsartorial canal block? Reg Anesth Pain Med. 2015;40:175–176. 2. Standring S. Gray’s Anatomy—The Anatomical Basis of Clinical Practice. 40th ed. Edinburgh, Scotland: Elsevier Churchill Livingstone; 2008. 3. Thiel W. Photographischer Atlas der Praktischen Anatomie. Berlin, Germany: Springer; 1996.
FIGURE 1. At different levels from the anterior superior iliac spine (ASIS) at A1 to the base of the patella at H1, the figure displays anatomical cross sections (A2–H2) in a cadaveric lower limb. A2 is a cross section of the ASIS. B2 intersects the iliopectineal fossa and the upper border of the greater trochanter. C2 is at the apex of the iliopectineal fossa. D2 corresponds to the midpoint between the ASIS and the base of the patella (the green line in D1 connects the ASIS and the base of the patella). E2 intersects the apex of the femoral triangle where the saphenous nerve and the femoral vessels exit the femoral triangle and enter the adductor canal. F2 is at the midpoint of the adductor canal. G2 is at the top of the adductor hiatus, which is the distal end of the adductor canal. H2 is at the base of the patella. In all sections, arteries are red, veins are blue, nerves are yellow, sartorius muscle is red, and the adductor longus muscle is purple. The iliopsoas muscle is green in cross sections A2–B2, the adductor magnus muscle is greenish-blue and only colored in cross sections E2–F2, the pectineus muscle is also greenish-blue and only colored in cross section B2, vastoadductor membrane is white in cross sections E–G, patella is green in cross section H2. The part of the adductor longus underneath the sartorius muscle is indicated by orange in E1. Modified excerpt from VH Dissector with permission from Touch of Life Technologies Inc (www.toltech.net). Built on real anatomy from the National Library of Medicine’s Visible Human Project.
they observed dye spread distal to the top of the adductor hiatus in only 1 cadaver,1 which suggests inadequate spread to fill the adductor canal in a high proportion of the cases. Ultrasound-guided injection into the true adductor canalwas described by Manickam et al.6 However, ultrasound-guided subsartorial blockade of the saphenous nerve can be achieved at any level from the apex of the iliopectineal fossa—inside the femoral triangle—to the distal end of the adductor canal. For a large volume saphenous nerve
392
block, local anesthetic injection in the femoral triangle may also block some of the femoral nerve branches to the vastus medialis muscle (Fig. 1D2), and injection in the true adductor canal may block the posterior branch of the obturator nerve if this branch passes through the adductor hiatus into the popliteal fossa.7 However, ultrasound guidance to block the saphenous nerve subsartorially and to block the obturator nerve in the subinguinal region with small volumes of local anesthetic is probably the most effective approach to block both nerves.
4. Tubbs RS, Loukas M, Shoja MM, Apaydin N, Oakes WJ, Salter EG. Anatomy and potential clinical significance of the vastoadductor membrane. Surg Radiol Anat. 2007;29: 569–573. 5. Gray H. Anatomy—Descriptive and Surgical. 17th ed. Philadelphia, PA: Lea and Febiger; 1908. 6. Manickam B, Perlas A, Duggan E, Brull R, Chan VW, Ramlogan R. Feasibility and efficacy of ultrasound-guided block of the saphenous nerve in the adductor canal. Reg Anesth Pain Med. 2009;34:578–580. 7. Kumka M. Critical sites of entrapment of the posterior division of the obturator nerve: anatomical considerations. J Can Chiropr Assoc. 2010;54:33–42.
Reply to Dr Bendtsen Accepted for publication: April 23, 2015. To the Editor: e thank Dr Bendtsen and colleagues for their thorough description of the femoral triangle and adductor canal.1 This correlates well with our understanding of the anatomy of the anterior thigh. We do not disagree that the vastoadductor membrane forms the roof of the adductor canal
W
© 2015 American Society of Regional Anesthesia and Pain Medicine
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
Regional Anesthesia and Pain Medicine • Volume 40, Number 4, July-August 2015
or that the adductor canal is a continuation of the femoral triangle. The important point that we,2 Tubbs et al,3 and Dr Bendtsen et al make is that “The vastoadductor membrane effectively creates a subcompartment within the subsartorial canal.”3 The vastoadductor membrane separates the subsartorial plexus from the saphenous nerve contained in the “adductor canal proper” as stated in Dr Bendtsen’s aforementioned correspondence. Hence, there is a subsartorial space (or canal, if we may) containing a neural plexus that needs to be considered when providing lower limb analgesia/anesthesia. The other point we made2 is that the commencement and length of the adductor canal are highly variable. Tubbs’ dissection study reported a range of 20 to 32 cm for the former (from the anterior superior iliac spine to the proximal border of the vastoadductor membrane) and 5.5 to 15 cm for the latter.2 Thus, it is highly probable that many clinicians are injecting superior to the adductor canal when performing an adductor canal block. As our letter states, we insert our catheter in to the femoral triangle using an easily definable sonoanatomical end point. Injection of dye at this point results in minimal spread superiorly and consistent spread inferiorly, posterior to the sartorius. These results are consistent with the anatomical dye study of Ishiguro et al.4 We routinely insert femoral nerve catheters at this position for patients undergoing knee replacement surgery. In our experience, a continuous catheter infusion of 5 to 10 mL of 0.2% ropivacaine produces reliable analgesia of the knee, with preservation of quadriceps strength. Patients routinely walk within 24 hours of surgery. To reiterate, we believe that it is important to achieve subsartorial spread of local anesthetic anterior and posterior of the vastoadductor membrane to provide excellent analgesia for knee arthroplasty surgery. We suggested the term “subsartorial canal block” to encompass the subsartorial space and not just the “adductor canal proper.” However, we accept that there remains some ambiguity of terminology. Phillip Cowlishaw, MBChB Mater Hospitals, Stanley St, Brisbane Queensland, Australia
Pierre Kotze, MBChB Mater Hospitals, Brisbane Queensland, Australia
The authors declare no conflict of interest. REFERENCES 1. Bendtsen TF, Moriggl B, Chan V, Børglum J. Basic topography of the saphenous nerve in the
femoral triangle and the adductor canal. Reg Anesth Pain Med. 2015;40:391–392. 2. Cowlishaw P, Kotze P. Adductor canal block—or subsartorial canal block? Reg Anesth Pain Med. 2015;40:175–176. 3. Tubbs RS, Loukas M, Shoja MM, Apaydin N, Oakes WJ, Salter EG. Anatomy and potential clinical significance of the vastoadductor membrane. Surgical and radiologic anatomy. Surg Radiol Anat. 2007;29:569–573. 4. Ishiguro S, Yokochi A, Yoshioka K, et al. Technical communication: anatomy and clinical implications of ultrasound-guided selective femoral nerve block. Anesth Anal. 2012;115:1467–1470.
Perineural Versus Systemic Dexamethasone Questions Remain Unanswered Accepted for publication: April 10, 2015. To the Editor: e read with interest the recent article by Abdallah et al1 comparing intravenous and perineural dexamethasone. The study found that perineural and intravenous dexamethasone similarly prolong the analgesic duration of bupivacaine supraclavicular brachial plexus blocks. We applaud the authors’ effort to answer this important clinical question. However, as noted by the authors, the chosen dose of dexamethasone 8 mg IV may be sufficient to mask the true site of action. A meta-analysis by De Oliveira et al2 in 2011 found systemic doses of dexamethasone greater than 0.1 mg/kg provide significant analgesia and reduced opioid consumption postoperatively. This study1 as well as others3 comparing intravenous to perineural dexamethasone have all examined high doses of dexamethasone that are likely close to 0.1 mg/kg. Conversely, a recent randomized, placebo-controlled trial of 39 patients receiving interscalene nerve blocks with ropivacaine 0.75% (20 mL) randomized patients to block alone, block with intravenous dexamethasone, or block with perineural dexamethasone.4 They found that a 4-mg dose of perineural dexamethasone prolonged analgesia longer than intravenous dexamethasone. Furthermore, block alone was not significantly different than block with intravenous dexamethasone. The minimum dose of intravenous dexamethasone sufficient to prolong the duration of peripheral blockade remains unknown. Recent evidence suggests, however, that the perineural dose of dexamethasone sufficient to prolong the duration of peripheral blockade is less than what was
W
© 2015 American Society of Regional Anesthesia and Pain Medicine
Letters to the Editor
previously thought. A recent study published by Liu et al5 compared the duration of supraclavicular block with bupivacaine 0.25% alone, to bupivacaine plus dexamethasone dosages of 1, 2, and 4 mg. The study demonstrated that low-dose perineural dexamethasone, 1 to 2 mg, similarly prolonged the duration of bupivacaine supraclavicular brachial plexus block as compared with 4 mg. In this study, dexamethasone prolonged the duration of bupivacaine 0.25% for supraclavicular block by greater than 10 hours. These data are more consistent with a locally mediated effect as opposed to a systemically mediated effect. Additionally, laboratory data from Williams et al6 have indicated that lower doses of perineural dexamethasone combined with ropivacaine have a neurotoxicity profile comparable to ropivacaine alone. It is possible, if not likely, that studies supporting a systemically mediated mechanism of action have incorporated dosages adequate to exert both systemic and local effects. Additional studies incorporating lower dosages of dexamethasone may more accurately reflect the site of action whereby dexamethasone prolongs the duration of peripheral nerve blockade. Eric D. Bolin, MD Sylvia Wilson, MD Department of Anesthesia and Perioperative Medicine Medical University of South Carolina Charleston, SC
The authors declare no conflict of interest. REFERENCES 1. Abdallah FW, Johnson J, Chan V, et al. Intravenous dexamethasone and perineural dexamethasone similarly prolong the duration of analgesia after supraclavicular brachial plexus block: a randomized, triple-arm, double-blind, placebo-controlled trial. Reg Anesth Pain Med. 2015;40:125–132. 2. De Oliveira GS Jr, Almeida MD, Benzon HT, McCarthy RJ. Perioperative single dose systemic dexamethasone for postoperative pain: a meta-analysis of randomized controlled trials. Anesthesiology. 2011;115: 575–588. 3. Desmet M, Braems H, Reynvoet M, et al. I.V. and perineural dexamethasone are equivalent in increasing the analgesic duration of a single-shot interscalene block with ropivacaine for shoulder surgery: a prospective, randomized, placebo-controlled study. Br J Anaesth. 2013; 111:445–452. 4. Kawanishi R, Yamamoto K, Tobetto Y, et al. Perineural but not systemic low-dose dexamethasone prolongs the duration of interscalene block with ropivacaine: a
393
Copyright © 2015 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
