Regional Anesthesia and Pain Medicine • Volume 39, Number 6, November-December 2014
José Raul Soberón, MD Clint E. Elliott, MD Kim S. Bland, MD Department of Anesthesiology Ochsner Clinic Foundation New Orleans, LA
Guy L. Weinberg, MD Department of Anesthesiology University of Illinois College of Medicine at Chicago Chicago, IL
The authors declare no conflict of interest. REFERENCES 1. Kleinman RE, Walker WA. Walker's Pediatric Gastrointestinal Disease: Physiology, Diagnosis, Management. Hamilton, Ontario, Canada: BC Decker, 2008. 2. Ellinas H, Frost EA. Mitochondrial disorders—a review of anesthetic considerations. Middle East J Anesthesiol. 2011;21:235–242. 3. Nouette-Gaulain K, Capdevila X, Rossignol R. Local anesthetic ‘in-situ’ toxicity during peripheral nerve blocks: update on mechanisms and prevention. Curr Opin Anaesthesiol. 2012;25:589–595. 4. Partownavid P, Umar S, Li J, Rahman S, Eghbali M. Fatty-acid oxidation and calcium homeostasis are involved in the rescue of bupivacaine-induced cardiotoxicity by lipid emulsion in rats. Crit Care Med. 2012;40: 2431–437.
A Modification of the Single-Penetration, Dual-Injection Technique for Combined Sciatic and Saphenous Nerve Blocks To the Editor: e read with great interest the recent article by Børglum et al1 promoting an ultrasound-guided, single-penetration, dual-injection (SPEDI) technique for combined sciatic and saphenous nerve blocks. Their evidence suggests this technique is equally effective and faster than saphenous and sciatic blocks performed independently. The SPEDI technique is performed in the proximal thigh at the level of the lesser trochanter under ultrasound visualization of both sciatic and femoral nerves. Practitioners experienced with ultrasoundguided blocks of the lower extremity will note that ultrasound identification of the sciatic nerve anteriorly in the proximal thigh is technically challenging. This is especially true in obese patients, and it is interesting to note that the average adult male body mass index in the United
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States is more than 4 points higher than in Denmark (where the SPEDI study was conducted).2 We agree when Dr Børglum and colleagues state the traditional “poplitealsciatic approach necessitates an elevation of the leg exposing the popliteal fossa or placement of the patient in the lateral or prone position,” which adds significant time to the procedure and may result in pain for the patient. However, we have used a modification of the described SPEDI technique that allows for improved ultrasound visualization of the sciatic nerve and avoids elevating the lower leg. This technique is also a “single-penetration, dual-injection” sciaticsaphenous block, but it is performed in the distal thigh via a medial approach. The patient’s knee is slightly bent and externally rotated, or “frog-legged,” allowing the ultrasound to be applied posteriorly to the popliteal fossa. The 2 branches of the sciatic nerve are identified at the level of the popliteal crease and traced proximally 4 to 8 cm until they join. At that point, a skin wheal is placed on the medial thigh allowing for in-plane needle visualization. After injectate is delivered around the sciatic nerve, the probe is then moved anteromedially, allowing visualization of the femoral artery. Using the same entry point, the needle is partially withdrawn and redirected anteriorly for saphenous nerve blockade.3 This approach offers the same advantages of efficiency while allowing for easy ultrasound-guided sciatic and saphenous nerve blocks. It also allows for avoidance of leg elevation required for the traditional lateral popliteal nerve block. We have used this modified technique on several patients successfully, but we acknowledge overall efficacy has yet to be proven. Stephen Harvey, MD John Corey, MD Kress Townley, MD Department of Anesthesiology Vanderbilt University Medical Center Nashville, TN [email protected]
The authors declares no conflict of interest. REFERENCES 1. Børglum J, Johansen K, Christensen MD, et al. Ultrasound-guided single-penetration dual-injection block for leg and foot surgery. Reg Anesth Pain Med. 2014;39:18–25. 2. WHO Global Infobase. Projected 2015 BMI values from WHO Info Database. Available at: apps.who.int/infobase/Indicators.aspx. Accessed July 3, 2014. 3. Krombach J, Gray AT. Sonography for saphenous nerve block near the adductor canal. Reg Anesth Pain Med. 2007;32:369–370.
© 2014 American Society of Regional Anesthesia and Pain Medicine
Letters to the Editor
Alcohol Swabs as “Cold Test” in a Measure of Temperature Sensation in the Skin Accepted for publication: August 18, 2014. To the Editor: e read with interest a recent article by Choquet et al,1 which described alternate approaches to ensuring adequate local anesthetic spread for ultrasound-guided popliteal sciatic nerve block. One of the methods used by the authors to assess sensory block was a loss of cold sensation in the tibial and common peroneal nerve distributions; however, the method of testing cold sensation was not given. Because afferent nerve fibers that conduct impulses for pain and temperature belong to the same group of Aδ fibers,2 loss of sensation to cold is commonly used in regional anesthesia as a surrogate for loss of pain sensation. The “cold test” can be performed with ice,3 a cold gel bag,4 and alcohol.5 Compared with other block assessment methods (eg, pinprick), it has minimal risk of trauma to the skin. Nevertheless, none of the coldtest methods has been shown to be superior to the others, and cold testing remains unstandardized and largely influenced by personal preference.6 We therefore conducted a study comparing the evaporative cooling effect of an alcohol swab with a swab that felt similar to the touch but was actually cold. After approval by the institutional Health Research Ethics Board and written consent, 40 healthy staff volunteers were recruited. The volunteers were swabbed with a regular alcohol swab (70% isopropyl alcohol; Canada Supply Inc, Mississauga, Ontario, Canada) at room temperature and a frozen swab. To prepare the frozen swabs, alcohol swabs were dried, wet with 4 drops of water, and frozen at −70°C for at least 12 hours. The swabs were applied simultaneously and randomly to one of the volunteers’ forearms on a hairless area. Volunteers were blinded to the properties of the swabs and were asked to determine if each swab felt “cold” or “not cold.” Most volunteers perceived the alcohol swab (n = 36/40) and frozen swab (n = 37/40) as cold (Fig. 1). A Fisher exact test demonstrated no statistically significant difference in perceived cold sensation between the 2 swabs (P = 1.00). Our results suggest that room-temperature alcohol swabs are a reasonable equivalent form of testing cold sensation. A limitation of this study was that the temperature generated from the evaporative effect of the alcohol was not measured because the cooling effect above the skin would be difficult to quantify. Also, the temperature of the frozen swabs (−9.5°C) was colder than ice (∼0°C), the typical cold stimulus used in
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Copyright © 2014 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
José Raul Soberón, MD Clint E. Elliott, MD Kim S. Bland, MD Department of Anesthesiology Ochsner Clinic Foundation New Orleans, LA
Guy L. Weinberg, MD Department of Anesthesiology University of Illinois College of Medicine at Chicago Chicago, IL
The authors declare no conflict of interest. REFERENCES 1. Kleinman RE, Walker WA. Walker's Pediatric Gastrointestinal Disease: Physiology, Diagnosis, Management. Hamilton, Ontario, Canada: BC Decker, 2008. 2. Ellinas H, Frost EA. Mitochondrial disorders—a review of anesthetic considerations. Middle East J Anesthesiol. 2011;21:235–242. 3. Nouette-Gaulain K, Capdevila X, Rossignol R. Local anesthetic ‘in-situ’ toxicity during peripheral nerve blocks: update on mechanisms and prevention. Curr Opin Anaesthesiol. 2012;25:589–595. 4. Partownavid P, Umar S, Li J, Rahman S, Eghbali M. Fatty-acid oxidation and calcium homeostasis are involved in the rescue of bupivacaine-induced cardiotoxicity by lipid emulsion in rats. Crit Care Med. 2012;40: 2431–437.
A Modification of the Single-Penetration, Dual-Injection Technique for Combined Sciatic and Saphenous Nerve Blocks To the Editor: e read with great interest the recent article by Børglum et al1 promoting an ultrasound-guided, single-penetration, dual-injection (SPEDI) technique for combined sciatic and saphenous nerve blocks. Their evidence suggests this technique is equally effective and faster than saphenous and sciatic blocks performed independently. The SPEDI technique is performed in the proximal thigh at the level of the lesser trochanter under ultrasound visualization of both sciatic and femoral nerves. Practitioners experienced with ultrasoundguided blocks of the lower extremity will note that ultrasound identification of the sciatic nerve anteriorly in the proximal thigh is technically challenging. This is especially true in obese patients, and it is interesting to note that the average adult male body mass index in the United
W
States is more than 4 points higher than in Denmark (where the SPEDI study was conducted).2 We agree when Dr Børglum and colleagues state the traditional “poplitealsciatic approach necessitates an elevation of the leg exposing the popliteal fossa or placement of the patient in the lateral or prone position,” which adds significant time to the procedure and may result in pain for the patient. However, we have used a modification of the described SPEDI technique that allows for improved ultrasound visualization of the sciatic nerve and avoids elevating the lower leg. This technique is also a “single-penetration, dual-injection” sciaticsaphenous block, but it is performed in the distal thigh via a medial approach. The patient’s knee is slightly bent and externally rotated, or “frog-legged,” allowing the ultrasound to be applied posteriorly to the popliteal fossa. The 2 branches of the sciatic nerve are identified at the level of the popliteal crease and traced proximally 4 to 8 cm until they join. At that point, a skin wheal is placed on the medial thigh allowing for in-plane needle visualization. After injectate is delivered around the sciatic nerve, the probe is then moved anteromedially, allowing visualization of the femoral artery. Using the same entry point, the needle is partially withdrawn and redirected anteriorly for saphenous nerve blockade.3 This approach offers the same advantages of efficiency while allowing for easy ultrasound-guided sciatic and saphenous nerve blocks. It also allows for avoidance of leg elevation required for the traditional lateral popliteal nerve block. We have used this modified technique on several patients successfully, but we acknowledge overall efficacy has yet to be proven. Stephen Harvey, MD John Corey, MD Kress Townley, MD Department of Anesthesiology Vanderbilt University Medical Center Nashville, TN [email protected]
The authors declares no conflict of interest. REFERENCES 1. Børglum J, Johansen K, Christensen MD, et al. Ultrasound-guided single-penetration dual-injection block for leg and foot surgery. Reg Anesth Pain Med. 2014;39:18–25. 2. WHO Global Infobase. Projected 2015 BMI values from WHO Info Database. Available at: apps.who.int/infobase/Indicators.aspx. Accessed July 3, 2014. 3. Krombach J, Gray AT. Sonography for saphenous nerve block near the adductor canal. Reg Anesth Pain Med. 2007;32:369–370.
© 2014 American Society of Regional Anesthesia and Pain Medicine
Letters to the Editor
Alcohol Swabs as “Cold Test” in a Measure of Temperature Sensation in the Skin Accepted for publication: August 18, 2014. To the Editor: e read with interest a recent article by Choquet et al,1 which described alternate approaches to ensuring adequate local anesthetic spread for ultrasound-guided popliteal sciatic nerve block. One of the methods used by the authors to assess sensory block was a loss of cold sensation in the tibial and common peroneal nerve distributions; however, the method of testing cold sensation was not given. Because afferent nerve fibers that conduct impulses for pain and temperature belong to the same group of Aδ fibers,2 loss of sensation to cold is commonly used in regional anesthesia as a surrogate for loss of pain sensation. The “cold test” can be performed with ice,3 a cold gel bag,4 and alcohol.5 Compared with other block assessment methods (eg, pinprick), it has minimal risk of trauma to the skin. Nevertheless, none of the coldtest methods has been shown to be superior to the others, and cold testing remains unstandardized and largely influenced by personal preference.6 We therefore conducted a study comparing the evaporative cooling effect of an alcohol swab with a swab that felt similar to the touch but was actually cold. After approval by the institutional Health Research Ethics Board and written consent, 40 healthy staff volunteers were recruited. The volunteers were swabbed with a regular alcohol swab (70% isopropyl alcohol; Canada Supply Inc, Mississauga, Ontario, Canada) at room temperature and a frozen swab. To prepare the frozen swabs, alcohol swabs were dried, wet with 4 drops of water, and frozen at −70°C for at least 12 hours. The swabs were applied simultaneously and randomly to one of the volunteers’ forearms on a hairless area. Volunteers were blinded to the properties of the swabs and were asked to determine if each swab felt “cold” or “not cold.” Most volunteers perceived the alcohol swab (n = 36/40) and frozen swab (n = 37/40) as cold (Fig. 1). A Fisher exact test demonstrated no statistically significant difference in perceived cold sensation between the 2 swabs (P = 1.00). Our results suggest that room-temperature alcohol swabs are a reasonable equivalent form of testing cold sensation. A limitation of this study was that the temperature generated from the evaporative effect of the alcohol was not measured because the cooling effect above the skin would be difficult to quantify. Also, the temperature of the frozen swabs (−9.5°C) was colder than ice (∼0°C), the typical cold stimulus used in
W
561
Copyright © 2014 American Society of Regional Anesthesia and Pain Medicine. Unauthorized reproduction of this article is prohibited.
