Letters to the Editor
In response to "Is Continuous Adductor Canal Block Better than Continuous Femoral Nerve Block after Total Knee Arthroplasty? Effect on Ambulation Ability, Early Functional Recovery and Pain Control: A Randomized Controlled Trial"
To the Editor: We read with interest the latest article published in the journal of arthroplasty titled “Is Continuous Adductor Canal Block Better than Continuous Femoral Nerve Block after Total Knee Arthroplasty? Effect on Ambulation Ability, Early Functional Recovery and Pain Control: A Randomized Controlled Trial” by Nilen A. Shah et al [1]. We, however, respectfully like to highlight certain important concerns which the study raised. 1. Timing and volume of the block — Going by the sequence in the article it seems that the block was given after administering spinal anesthesia. This is of particular importance considering the amount of local anesthetic (30 cc of 0.75%) which was injected both in the adductor canal and for femoral nerve block, as any neuronal paresthesias or intraneural injection could be missed. This is more important since minimal effective anesthetic concentration for ultrasound guided femoral nerve block is only 15 ml of 0.167% ropivacaine under ultrasound visualization [2]. This is also important in patients receiving adductor canal catheter as motor side effects are now being reported in the literature with higher volumes of injectate [3,4]. In our opinion, risks of nerve injury and paresthesia can be missed if the blocks were placed in an already anesthetized limb. 2. Ultrasound vs nerve stimulator — Why was ultrasound not utilized in all the cases of femoral nerve block and only reserved for obese and difficult cases? This is important for various reasons. First, it is a potential source of bias originating from the technique in terms of comparing a superior technique of ultrasound guided to less successful technique of nerve stimulator guided nerve block. Even more difficult to compare is the femoral catheter placement as it has been shown that it is less successful with nerve stimulator based technique compared to ultrasound guided technique. 3. Authors also deduce that the success rate of adductor canal block was 96%. We question the validity of this finding given the patients were already anesthetized by spinal anesthesia. Were any tests performed on the saphenous nerve dermatome, if yes, what was the procedure and what were the timings of the test? Although it appears that adductor nerve block is a good alternative approach for femoral nerve block as it is associated with some quadriceps weakness, but we have to be very cautious about the dosage and volume of the drug being administered considering the side effects which have recently been reported. Further large randomized controlled dose based trials are warranted to confirm further efficacy and suitability of the adductor canal block.
Akhilesh Kumar Tiwari, MBBS, DNB⁎ Arun Prasad FRCPC Toronto Western Hospital ⁎Reprint requests: Akhilesh Kumar Tiwari, MBBS, DNB, Toronto Western Hospital, 399 Bathurst Street, Toronto, ON M5T 2S8, Canada
http://dx.doi.org/10.1016/j.arth.2014.10.012
515
References 1. Shah NA, Jain NP. Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: A randomized controlled trial. J Arthroplasty 2014. http:// dx.doi.org/10.1016/j.arth.2014.06.010. 2. Taha AM, Abd-Elmaksoud AM. Ropivacaine in ultrasound-guided femoral nerve block: What is the minimal effective anaesthetic concentration (EC90)? Anaesthesia 2014; 69:678. 3. Chen J, Lesser JB, Hadzic A, Reiss W, Resta-Flarer F. Adductor canal block can result in motor block of the quadriceps muscle. Reg Anesth Pain Med 2014;39:170. 4. Veal C, Auyong DB, Hanson NA, et al. Delayed quadriceps weakness after continuous adductor canal block for total knee arthroplasty: A case report. Acta Anaesthesiol Scand 2013. http://dx.doi.org/10.1111/aas.12244.
In Reply
"Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial" We would like to appreciate and thank the authors of the letter for their interest in our study and their questions regarding our recent publication exploring and comparing the effects of continuous adductor canal block and continuous femoral nerve block [1] post total knee arthroplasty. Our answers are as follows: 1. Timing and volume of the block: We agree that all patients in both the groups were operated under spinal anesthesia and the blocks were administered immediately after surgery when the effect of spinal anesthesia was still present. This was done so as to prevent any discomfort to the patients and that they remain pain free postoperatively. A volume of 30 ml of local anaesthetic was injected for both the block techniques. A previous MRI based study on adductor canal block considered 30 ml of volume as deemed appropriate for adductor canal block [2]. We used a similar volume and concentration of local anesthetic to maintain the uniformity and comparability between the two groups and prevent confounding effects of varying volume and concentration of local anaesthetic in two different block techniques. We share the concern that the nerve damage may be missed when the block is performed in a limb that is still under the effect of spinal anesthesia. However, we did not have any cases of nerve damage in our study. 2. Ultrasound vs. nerve stimulator: We did not utilize the ultrasound for all cases of femoral nerve blockade as the femoral arterial pulsation was readily felt and was an excellent landmark for the femoral nerve which was located with the nerve stimulator. The ultrasound was reserved for obese patients in whom it was difficult to palpate the femoral artery. This decision of using the ultrasound or the nerve stimulator was at the discretion of the anesthetist. Moreover, we had 100% success rate in femoral nerve block technique. The only previous study comparing ultrasound and nerve stimulation technique in femoral nerve block showed significant time difference with a mean of 5 minutes and 8.5 minutes for ultrasound and nerve stimulator technique respectively [3]. However, the mean time for femoral block was only 3.76 minutes in the present study. Furthermore, there are reports that even after using an ultrasound for the femoral nerve blockade, can result in intraneural injection [4] and not guarantee freedom from complications. 3. Success rate: The success rate of the adductor canal block in the present study was 96%. The success of block was determined by assessment of cold sensation in the saphenous area specifically on the medial side of the lower leg at the time of bolus injection. This was tested about four hours after the administration of the block.
In response to "Is Continuous Adductor Canal Block Better than Continuous Femoral Nerve Block after Total Knee Arthroplasty? Effect on Ambulation Ability, Early Functional Recovery and Pain Control: A Randomized Controlled Trial"
To the Editor: We read with interest the latest article published in the journal of arthroplasty titled “Is Continuous Adductor Canal Block Better than Continuous Femoral Nerve Block after Total Knee Arthroplasty? Effect on Ambulation Ability, Early Functional Recovery and Pain Control: A Randomized Controlled Trial” by Nilen A. Shah et al [1]. We, however, respectfully like to highlight certain important concerns which the study raised. 1. Timing and volume of the block — Going by the sequence in the article it seems that the block was given after administering spinal anesthesia. This is of particular importance considering the amount of local anesthetic (30 cc of 0.75%) which was injected both in the adductor canal and for femoral nerve block, as any neuronal paresthesias or intraneural injection could be missed. This is more important since minimal effective anesthetic concentration for ultrasound guided femoral nerve block is only 15 ml of 0.167% ropivacaine under ultrasound visualization [2]. This is also important in patients receiving adductor canal catheter as motor side effects are now being reported in the literature with higher volumes of injectate [3,4]. In our opinion, risks of nerve injury and paresthesia can be missed if the blocks were placed in an already anesthetized limb. 2. Ultrasound vs nerve stimulator — Why was ultrasound not utilized in all the cases of femoral nerve block and only reserved for obese and difficult cases? This is important for various reasons. First, it is a potential source of bias originating from the technique in terms of comparing a superior technique of ultrasound guided to less successful technique of nerve stimulator guided nerve block. Even more difficult to compare is the femoral catheter placement as it has been shown that it is less successful with nerve stimulator based technique compared to ultrasound guided technique. 3. Authors also deduce that the success rate of adductor canal block was 96%. We question the validity of this finding given the patients were already anesthetized by spinal anesthesia. Were any tests performed on the saphenous nerve dermatome, if yes, what was the procedure and what were the timings of the test? Although it appears that adductor nerve block is a good alternative approach for femoral nerve block as it is associated with some quadriceps weakness, but we have to be very cautious about the dosage and volume of the drug being administered considering the side effects which have recently been reported. Further large randomized controlled dose based trials are warranted to confirm further efficacy and suitability of the adductor canal block.
Akhilesh Kumar Tiwari, MBBS, DNB⁎ Arun Prasad FRCPC Toronto Western Hospital ⁎Reprint requests: Akhilesh Kumar Tiwari, MBBS, DNB, Toronto Western Hospital, 399 Bathurst Street, Toronto, ON M5T 2S8, Canada
http://dx.doi.org/10.1016/j.arth.2014.10.012
515
References 1. Shah NA, Jain NP. Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: A randomized controlled trial. J Arthroplasty 2014. http:// dx.doi.org/10.1016/j.arth.2014.06.010. 2. Taha AM, Abd-Elmaksoud AM. Ropivacaine in ultrasound-guided femoral nerve block: What is the minimal effective anaesthetic concentration (EC90)? Anaesthesia 2014; 69:678. 3. Chen J, Lesser JB, Hadzic A, Reiss W, Resta-Flarer F. Adductor canal block can result in motor block of the quadriceps muscle. Reg Anesth Pain Med 2014;39:170. 4. Veal C, Auyong DB, Hanson NA, et al. Delayed quadriceps weakness after continuous adductor canal block for total knee arthroplasty: A case report. Acta Anaesthesiol Scand 2013. http://dx.doi.org/10.1111/aas.12244.
In Reply
"Is continuous adductor canal block better than continuous femoral nerve block after total knee arthroplasty? Effect on ambulation ability, early functional recovery and pain control: a randomized controlled trial" We would like to appreciate and thank the authors of the letter for their interest in our study and their questions regarding our recent publication exploring and comparing the effects of continuous adductor canal block and continuous femoral nerve block [1] post total knee arthroplasty. Our answers are as follows: 1. Timing and volume of the block: We agree that all patients in both the groups were operated under spinal anesthesia and the blocks were administered immediately after surgery when the effect of spinal anesthesia was still present. This was done so as to prevent any discomfort to the patients and that they remain pain free postoperatively. A volume of 30 ml of local anaesthetic was injected for both the block techniques. A previous MRI based study on adductor canal block considered 30 ml of volume as deemed appropriate for adductor canal block [2]. We used a similar volume and concentration of local anesthetic to maintain the uniformity and comparability between the two groups and prevent confounding effects of varying volume and concentration of local anaesthetic in two different block techniques. We share the concern that the nerve damage may be missed when the block is performed in a limb that is still under the effect of spinal anesthesia. However, we did not have any cases of nerve damage in our study. 2. Ultrasound vs. nerve stimulator: We did not utilize the ultrasound for all cases of femoral nerve blockade as the femoral arterial pulsation was readily felt and was an excellent landmark for the femoral nerve which was located with the nerve stimulator. The ultrasound was reserved for obese patients in whom it was difficult to palpate the femoral artery. This decision of using the ultrasound or the nerve stimulator was at the discretion of the anesthetist. Moreover, we had 100% success rate in femoral nerve block technique. The only previous study comparing ultrasound and nerve stimulation technique in femoral nerve block showed significant time difference with a mean of 5 minutes and 8.5 minutes for ultrasound and nerve stimulator technique respectively [3]. However, the mean time for femoral block was only 3.76 minutes in the present study. Furthermore, there are reports that even after using an ultrasound for the femoral nerve blockade, can result in intraneural injection [4] and not guarantee freedom from complications. 3. Success rate: The success rate of the adductor canal block in the present study was 96%. The success of block was determined by assessment of cold sensation in the saphenous area specifically on the medial side of the lower leg at the time of bolus injection. This was tested about four hours after the administration of the block.
