Anesth Analg 2004;98:747-749
© 2004 International Anesthesia Research Society
doi: 10.1213/01.ANE.0000096186.89230.56
PAIN MEDICINE
Analgesia After Total Knee Arthroplasty: Is Continuous Sciatic Blockade Needed in Addition to Continuous Femoral Blockade?
Bruce Ben-David, MD,
Kevin Schmalenberger, MD, and
Jacques E. Chelly, MD,PhD, MBA
Department of Anesthesiology, University of Pittsburgh Medical Centers, Shadyside Hospital, Pittsburgh, Pennsylvania
Address correspondence and reprint requests to: Bruce Ben-David, MD, Department of Anesthesiology, Shadyside Hospital, 5230 Centre Avenue, Pittsburgh, PA 15232. Address email to bendavid{at}verizon.net
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Abstract
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Continuous femoral "3-in-1" nerve blocks are commonly used for analgesia after total knee arthroplasty (TKA). There are conflicting data as to whether additional sciatic blockade is needed. Our routine use of both continuous femoral (CFI) and sciatic (CSI) peripheral nerve blocks was changed because of concerns that sciatic blockade, and its motor consequences in particular, might obscure diagnosis of perioperative sciatic nerve injury. The revised protocol includes placing single-shot blocks and perineural catheters at both sites, but infusing local anesthetic postoperatively only in the CFI. CSI is reserved for patients having poorly controlled posterior knee or calf pain. A sample group of 12 patients treated with this protocol was followed. Ten of 12 patients required use of the CSI. Within 1 h of a 5–10 mL CSI bolus of 0.2% ropivacaine and beginning an infusion of the same drug at 5 mL/h, patients’ median pain by verbal analog scale decreased from 7.5 to 2.0 (mean scores from 7.3 to 2.4). It was possible to maintain this level of analgesia until the third postoperative day when catheters were discontinued. Our experience suggests that, in most patients, adequate analgesia after TKA cannot be achieved with CFI alone and that the addition of CSI renders a significant improvement in analgesia.
IMPLICATIONS: A child with neurofibromatosis, scoliosis, and a chest wall deformity presenting for spinal fusion developed severe hypotension while prone. This was due to compression of the heart by the sternum, not compression of the great vessels by neurofibromas. Sternal pressure in prone patients with chest wall deformities should be avoided. Unique management included the use of transesophageal echocardiography to determine the cause of the hypotension.
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Introduction
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Our acute pain service’s (APS) standard practice in providing postoperative analgesia after total knee arthroplasty (TKA) has for some time been the combined use of both continuous femoral (CFI) and continuous sciatic infusion (CSI) nerve blocks. In response to surgeons’ concerns regarding postoperative sciatic block (e.g., difficulty in diagnosing peroneal nerve injury or an evolving sciatic nerve injury from compartment syndrome), we modified our standard protocol in an attempt to limit the use of CSI. We report here the results of that change.
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Methods
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We followed a sample group of 12 consecutive patients, 50–75 yr old, presenting for primary TKA who were managed according to our revised APS standard protocol for TKA. Our IRB deemed this report did not require permission. In the preoperative holding area an IV infusion of lactated Ringer’s solution was started and monitoring was established with automated blood pressure and pulse oximetry. Patients received rofecoxib 50 mg PO with a "sip of water" and IV midazolam was titrated to achieve moderate sedation (total dose 1–5 mg).
With the patient in the supine position, the location of the femoral artery was marked on the skin. The inguinal area was prepped with antiseptic solution and sterilely draped. A femoral nerve block was placed by the inguinal paravascular approach using electrically insulated 5-cm introducer Tuohy needles (Contiplex®, B. Braun Medical, Bethlehem, PA or Prolong®, Life-Tech, Stafford, TX). Localization of the femoral nerve was defined by quadriceps twitch at < 0.5 mAmp using a stimulation of 0.1 ms at 2 Hz. After negative aspiration, 30 mL of ropivacaine 0.5% was injected through the Tuohy needle in 5-mL increments. This was followed by the placement of a 22-gauge catheter introduced in a cephalad direction through the needle and positioned to a depth 4–6 cm beyond the depth of the needle tip. The catheter was taped into position with Steri-strips, covered with an adhesive dressing, and labeled.
The patient was then turned into the lateral position and a subgluteal sciatic block placed as previously described (1) using a 10-cm insulated introducer Tuohy needle. Stimulation of either the common peroneal or tibial nerve was considered acceptable as long as stimulation was at <0.5 mAmp. To minimize postoperative sciatic motor block and to facilitate early sciatic nerve evaluation, a small dose and concentration of ropivacaine (0.2%, 20 mL) was injected. A catheter was positioned to a depth 4–6 cm beyond the depth of the needle tip. Blocks were not consistently assessed before taking the patient to the operating room.
Patients received either general or spinal anesthesia intraoperatively. In the postanesthesia care unit (PACU) femoral catheters were infused with 0.2% ropivacaine at 7 mL/h. Sciatic catheters were left in place but infusions were not begun. Nurses in the PACU were allowed to titrate IV morphine as needed. Also, beginning in the PACU patients had free access to patient-controlled analgesia (PCA) morphine (1 mg bolus/6 min lockout/20 mg 4 h lockout) until 6 AM the following morning at which time they received only daily scheduled rofecoxib and oxycodone tablets by mouth as needed for breakthrough pain. Nurses were instructed to contact the APS if the patient had unacceptable pain (visual analog scale [VAS] 
4 of 10).
Of the 12 patients, 10 developed significant postoperative pain despite the morphine administered by the PACU nurse and the PCA. In all 10 cases CSI was initiated before discontinuation of the PCA. In all cases except one, the pain was clearly localized to the posterior knee or calf. In all 10 of the patients the sciatic catheter was injected with a 5–10 mL bolus of ropivacaine 0.2% and an infusion of the same solution was begun at a rate of 5 mL/h. Within the ensuing hour all of the 10 patients, including the one patient with anterior pain, reported clinically significant reductions in their pain. In these ten patients median pain scores using a VAS from 0 to 10 decreased from 7.5 to 2. Mean scores changed from 7.3 to 2.4.
All infusions were continued until the morning of the third postoperative day, at which time the catheters were removed. Catheter removal was not conditional to coagulation status. In two of the patients, weakness of plantar and/or dorsiflexion of the foot required temporary cessation of the infusion. In both patients motor function recovered over the next several hours and the infusion was reinstated at a slower rate. Until the time of catheter removal patients’ levels of analgesia remained comparable or better than those achieved after beginning the CSI. All patients were able to cooperate well with physical therapy. There were no complications observed from the peripheral nerve blocks or continuous infusions.
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Discussion
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Our protocol change to limit the use of CSI after TKA has been revealing. In this group of 12 patients, we found that 10 of 12 (83%) did get substantially improved analgesia from CSI beyond that achieved with CFI and a single-shot sciatic block. In those 10 patients pain scores were reduced on average to one-third of their initial intensity by reinstating sciatic blockade using the CSI. Once CSI was begun in these patients it was also possible to maintain the high level of postoperative analgesia. Our experience suggests that a single-shot sciatic nerve block added to CFI is usually not sufficient to provide and maintain satisfactory postoperative analgesia after TKA and that a CSI of local anesthetic is usually necessary.
The sensory innervation of the knee derives from the sciatic nerve as well as from the obturator, femoral, and lateral femoral cutaneous nerves. Though the literature has supported the use of lumbar plexus or "3-in-1" femoral nerve blocks for analgesia after TKA, there are conflicting data as to whether additional sciatic blockade is necessary. Allen et al. (2) compared analgesia after TKA with femoral or sciatic-femoral nerve blocks and found no benefit to the added sciatic block. Reports of satisfactory analgesia with femoral block alone (3,4) are countered by studies that found it to be inadequate (5–8). Weber et al. (7) reported that 67% of patients who had had a preoperative femoral block required the addition of a sciatic block postoperatively. Our experience also indicates the relative inadequacy of femoral "3-in-1" block by itself.
In our patients the analgesia that was initially effective with combined femoral and sciatic blocks became ineffective in 83% of patients only to become effective again with reinstatement of the sciatic block added to the CFI. Whereas Chelly et al. (9) and Eledjam et al. (10) reported excellent analgesia from the combination of CFI with only a single sciatic nerve block, our current experience suggests that not only is sciatic blockade usually important for successful analgesia after TKA but also that CSI is typically needed to maintain the level of analgesia provided by the initial block. A prospective, randomized, placebo controlled study is required to further establish this indication for CSI.
Critical to interpreting the results of both future and past studies on peripheral nerve blockade analgesia are the many details of the particular protocol. In particular, the use of adjunctive analgesics may have a profound effect on the need for and analgesic benefit of a particular intervention such as CSI. A protocol, such as ours, that shifts the emphasis away from a reliance on opiates may bias the findings in support of a need for CSI. Greater use of opiates in our protocol may have significantly altered our conclusions. Furthermore, there remain concerns as to both the incidence and nature of risks from CSI (e.g., unrecognized compartment syndrome) and how these might be mitigated (e.g., use of smaller concentration local anesthetic). Likewise, the efficacy and clinical benefits of CSI, as well as cost implications, need to be further defined and compared with other alternatives. Again, further prospective study is needed to address these questions.
Although our patients’ pain scores were low, it is notable that not a single patient was entirely free of pain even with combined CFI and CSI. The probable explanation for this is the inability of the femoral "3-in-1" block to reliably anesthetize all components of the lumbar plexus, in particular the obturator nerve (11–13). McNamee et al. (14) added an obturator nerve block to femoral and sciatic blocks in patients undergoing TKA and found a significant increase in the time until first request for analgesia and a significant reduction in postoperative morphine requirements. However, given the low pain scores we have seen with combined CFI and CSI, it is uncertain what the clinical impact would be of more complete blockade of the lumbar plexus.
Our APS protocol for TKA remains as described in this report and ongoing audit continues to show roughly an 85% rate of use of the CSI after TKA. We perform both femoral and sciatic blocks preoperatively and place the corresponding perineural catheters. The CFI is systematically started in the PACU and the sciatic catheter is connected but the infusion not commenced unless the patient complains of pain in the "sciatic territory" (posterior aspect of the knee or calf). Pain experienced in the anterior knee in the presence of a demonstrable femoral block that fails to respond to further femoral catheter bolus of local anesthetic may on occasion, as seen in one case here, respond to CSI. Although we have not been able to eliminate the CSI, given our analgesic approach and its focus on limiting opiate consumption, we remain cognizant of the surgeons’ concerns. It is therefore important to stress the need for constant vigilance as to developing motor blockade in either the tibial (plantar flexion) or common peroneal (dorsiflexion) distribution that would require at least temporary cessation of CSI. We acknowledge that as our analgesic techniques develop their success will be measured not only by analgesic response, but also by how well they incorporate and respect the goals and concerns of our surgical colleagues.
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Acknowledgments
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We thank Lois Pizzi, RN, pain management coordinator, Shadyside Hospital and Patricia Telesz RN, acute pain nurse, Shadyside Hospital.
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References
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Accepted for publication August 26, 2003.
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Abstract
Introduction
