To the Editor:
I read with great interest the article by Farag et al.1 Undoubtedly, the authors tried to address a very important concern related to the use of peripheral nerve blocks as a part of comprehensive acute perioperative pain management. However, it seems that they failed to recognize the specificity of the patient population they studied. Functional recovery is the main determinant for patients undergoing total knee replacement. The goal of perioperative pain management in patients undergoing total knee replacement is not to minimize pain at rest, it is to minimize pain during physical therapy while optimizing quadriceps function and minimizing the postoperative risk of falls. Effective pain control during physical therapy has been established to facilitate functional recovery,2 and excessive postoperative quadriceps weakness has been shown to be a significant cause of falls.3 Unfortunately, none of these endpoints were considered in the article by Farag et al.. The authors should recognize that the ability to recover motor function after surgery and the absence of a fall represents an important determinant of the patient length of stay in the hospital, which is estimated to cost thousands of dollars4 versus tens of dollars as studied by Farag et al. In my institution, most patients start active physical therapy on the day of surgery and are discharged on postoperative day 2. Optimizing functional recovery hours after surgery is essential because if the patients cannot participate actively in physical therapy, their length of stay increases and with it the overall cost of the surgery.
I was also surprised by the authors’ choice of 0.1% ropivacaine at 8 ml/h because even 4 ml/h of ropivacaine 0.1% has been well established to lead to significant motor blockade.5 In my experience, 3 ml/h or less of ropivacaine 0.1% or bupivacaine 0.0625% seems to be optimal to preserve motor function postoperatively in most patients undergoing total knee replacement.
If the interest is on cost, consideration should be given to the cost of the local anesthetic solution when choosing a continuous block technique. In my institution, we switched from ropivacaine 0.1% to bupivacaine 0.0625% and saved $30 per bag. These cost savings are substantial for my institution, as we use more than 35,000 bags annually.
In the discussion, the authors raised another important point, for example, the time required to perform a continuous block using each technique. These data were missing from the article and would be most interesting, especially as it relates to the use of ultrasound alone versus ultrasound combined with a stimulating needle. In my experience, the difference in the time required for each technique should be insignificant, especially in the hands of an experienced regional anesthesiologist.
In conclusion, anesthesiologists should recognize the specific surgical requirement when comparing different approaches. In patients undergoing total knee replacement, optimizing pain during physical therapy, functional recovery, and minimizing the risk of falls should represent the primary concern.
The author declares no competing interests.