Posterior Popliteal Approach Research Articles

The Effects of Varying Local Anesthetic Concentration and Volume on Continuous Popliteal Sciatic Nerve Blocks: A Dual-Center, Randomized, Controlled Study

It remains unknown whether local anesthetic concentration, or simply total drug dose, is the primary determinant of continuous peripheral nerve block effects. We therefore tested the null hypothesis that providing different concentrations and rates of ropivacaine, but at equal total doses, produces comparable effects when used in a continuous sciatic nerve block in the popliteal fossa. Preoperatively, a perineural catheter was inserted adjacent to the sciatic nerve using a posterior popliteal approach in patients undergoing moderately painful orthopedic surgery at or distal to the ankle. Postoperatively, patients were randomly assigned to receive a perineural ropivacaine infusion of either 0.2% (basal 8 mL/h, bolus 4 mL) or 0.4% (basal 4 mL/h, bolus 2 mL) through the second postoperative day. Therefore, both groups received 16 mg of ropivacaine each hour with a possible addition of 8 mg every 30 min via a patient-controlled bolus dose. The primary end point was the incidence of an insensate limb, considered undesirable, during the 24-h period beginning the morning after surgery. Secondary end points included analgesia and patient satisfaction. Patients given 0.2% ropivacaine (n = 25) experienced an insensate limb with a mean (sd) of 1.8 (1.8) times, compared with 0.6 (1.1) times for subjects receiving 0.4% ropivacaine (n = 25; estimated difference = 1.2 episodes, 95% confidence interval, 0.3-2.0 episodes; P = 0.009). In contrast, analgesia and satisfaction were similar in each group. For continuous popliteal-sciatic nerve blocks, local anesthetic concentration and volume influence block characteristics. Insensate limbs were far more common with larger volumes of relatively dilute ropivacaine. During continuous sciatic nerve block in the popliteal fossa, a relatively concentrated solution in smaller volume thus appears preferable.

Traumatic Pseudoaneurysm of the Popliteal Artery After Blunt Trauma: Case Report and a Review of the Literature

Pseudoaneurysms of the popliteal artery following trauma are rare lesions. We present 3 cases of pseudoaneurysms of the popliteal artery (4, 20, and 45 years old respectively) with a delayed presentation, following blunt trauma, presenting over a 3-year period, and a short review of the relevant literature. A delayed pattern of presentation, over 2 years after blunt popliteal trauma, was observed in all patients. They presented with a painful pulsatile mass in the popliteal fossa, and their peripheral pulses were normal. Orthopedic and rheumatologic evaluation findings were negative. Diagnostic evaluation included triplex, arteriography, and computed tomography angiography. A posterior popliteal approach was used, and after aneurysmal excision, reversed great saphenous vein and lesser saphenous vein (1 patient) grafts were used. After 2 to 4 years of follow-up, all grafts remain patent and the patients have fully functional limbs. A literature search revealed 70 cases of pseudoaneurysms of the popliteal artery reported in civilian settings. These lesions should be repaired shortly because their complications (rupture, thromboembolic episodes) carry a high risk for limb dysfunction and amputation. Penetrating or blunt trauma is the main causative factor (62.5%), but iatrogenic trauma accounts for an increasing number of reports (37.5%). Strict follow-up of popliteal trauma is essential. A high level of suspicion and awareness can lead to early diagnosis and treatment of pseudoaneurysms of the popliteal artery and prevent the serious complications associated with these lesions.

Lateral or Posterior Popliteal Approach for Sciatic Nerve Block: Difference is Related to the Anatomy

To the Editor: March and colleagues (1) comparing single- and double-injection techniques for blockade of the sciatic nerve block via a posterior popliteal approach, concluded that double-nerve stimulation resulted in similar onset time and overall success rate when compared with that after single-nerve stimulation. In the double-injection group, they located both common peroneal and tibial nerve, whereas in the single-injection group they preferentially elicited foot inversion, interpreting this motor response to reflect needle proximity to both sciatic nerve trunks (2). Our group has extensive experience providing regional anesthesia for outpatients undergoing foot surgery (3). We recently showed that, when using a lateral popliteal sciatic nerve block, a single injection targeting the tibial nerve is more effective than a single injection targeting the peroneal nerve and is also as effective as a double injection of both branches of the sciatic nerve (4). We believe that results from March's work lend further support for our results, even when the different drugs and dosages used are taken into account. When a double-injection procedure is employed, the success rates after the lateral or posterior approaches are similar (respectively, 94% vs 87%) whereas a single-injection technique yields similar or even better results only if it is performed via a lateral approach and it is targeted at the tibial branch of the sciatic nerve (success rate: lateral 94% vs posterior 77%). Considering the anatomy of the sciatic nerve at the popliteal level (5), targeting the tibial nerve via a lateral popliteal approach will likely result in injecting local anesthetic within the adventitia that envelops both branches of the sciatic nerve (4). On the other hand, the same single injection technique performed via a posterior approach will not assure that local anesthetic is injected within the tibial and peroneal common perineural space. Stefano Palmisani Department of Anesthesiology and Intensive Care Medicine Sant'Andrea Hospital University of Rome La Sapienza [email protected] Paolo Ronconi, MD Foot Medical Hospital Roberto Alberto De Blasi, MD Roberto Arcioni, MD Department of Anesthesiology and Intensive Care Medicine Sant'Andrea Hospital University of Rome La Sapienza Rome, Italy

Lateral or Posterior Popliteal Approach for Sciatic Nerve Block: Difference is Related to the Anatomy

In Response: We thank Risch et al. (1) and Palmisani et al. (2) for their comments on our article. In response to Risch et al., we clearly state that nerve stimulation of the sciatic nerve was performed 10 cm from the popliteal skin crease, after the recommendations made in the study of Vloka et al. (3) in cadavers. As Vloka et al. show, injection at this point ensures placement of the needle in the vicinity of, or proximal to, the separation of the sciatic nerve. Although Borgeat et al. (4) have found a high level of clinical efficacy in using the apex of the popliteal fossa as the injection site, we believe that anatomic confirmation should be sought from cadavers that this point corresponds to the division of the sciatic nerve. Our study (5) which compared a single- versus a double-injection technique, must be based on a reference point validated by anatomical observation. The time between the two injections in the double stimulation group is not recorded but the total performance time, which is provided, is low. In practice, when the first injection is completed, the second injection is begun immediately. Although it is true that multiple nerve stimulation theoretically has a greater risk of injury, in practice this has not been demonstrated (6). Despite the comments by Palmisani et al. (2) we believe that the single-injection technique is as successful using a posterior approach as a lateral approach. For example, Borgeat et al. (4) use only the posterior approach, in their study of 500 patients, and had a 94% success rate. The difference in efficacy in single injection between the studies of Borgeat et al. (4), Arcioni et al. (7), and our own may well be explained by the difference in dose. While we used 25 mL of mepivacaine 1%, Arcioni et al. used 30 mL of ropivacaine 0.75% and Borgeat et al. used 40–50 mL of ropivacaine 0.5%. The tibial response, plantar flexion or inversion, should be considered as the motor response of choice when a single injection sciatic nerve block in the popliteal fossa is performed. This is supported by the most recent clinical studies (8) and through the magnetic resonances of two volunteers in the study of Arcioni et al. (7). We believe that, as our study shows, the use of a double injection of the sciatic nerve has advantages when working with low doses. Xavier March, MD Olga Pineda, MD Dolores Caramés, MD Antonio Villalonga, PhD Servei d'Anestèsia Reanimació i Terapèutica del Dolor Hospital Universitari de Girona Dr Joseph Trueta Girona, Spain [email protected]

Minimum effective anesthetic concentration (MEAC) for sciatic nerve block: subgluteus and popliteal approaches

We tested the hypothesis that using a subgluteus approach to the sciatic nerve requires a lower concentration of mepivacaine to obtain complete anesthesia as compared with the popliteal approach.With midazolam premedication (0.05 mg kg(-1) iv), 48 patients undergoing hallux valgus repair were randomly allocated to receive a sciatic nerve block using either a posterior popliteal (group Popliteal, n = 24) or subgluteus (group Subgluteus, n = 24) approach with 30 mL of local anesthetic injected after elicitation of plantar flexion of the foot with a current <or= 0.5 mA. A 20G catheter was inserted for 2-4 cm to supplement the block if required. The concentration of the injected solution was varied for consecutive patients using the up-and-down staircase method according to the response of the previous patient (initial concentration: 1%; up-and-down steps: 0.1%). Successful nerve block was defined as complete loss of pinprick sensation in both tibial and common peroneal nerve distributions with concomitant inability to perform plantar or dorsal flexion of the foot 30 min after injection.The minimum effective anesthetic concentration of mepivacaine resulting in complete block of the sciatic nerve in 50% of cases (ED(50)) was 0.95% +/- 0.014% (95% confidence intervals [CI(95)]: 0.77%-1.12%) in group Subgluteus and 1.53% +/- 0.453% (CI(95): 0.96%-2.00%) in group Popliteal (P = 0.026). The ED(95) for adequate nerve block calculated with probit transformation and logistic regression analysis was 1.12% (CI(95): 0.71%-1.99%) in group Subgluteus and 1.98% (CI(95): 1.39%-2.31%) in group Popliteal.A subgluteus approach to the sciatic nerve facilitates a reduction of the minimum effective concentration of local anesthetic required to produce an effective surgical block within 30 min after the injection as compared with the posterior popliteal approach.

Perineural Infusion of Local Anesthetics:“More to the Review”

Dr. Boezaart’s review article titled “Perineural Infusion of Local Anesthetics”1represents a commendable attempt to educate the reader on a complex and evolving topic. In reading this article, we were surprised by the author’s use of a study performed in volunteers to support the claim that the use of a stimulating catheter was associated with “around” 100% success compared with 65–85% for a nonstimulating technique. Studies conducted in patients certainly did not support this concept.2It is unfortunate that Dr. Boezaart did not acknowledge the value of continuous lumbar plexus blocks for hip primary replacement3and acetabular fracture,4especially when considering that some surgeons include the inguinal crease in their hip preparation, making impossible the preoperative placement of a femoral perineural catheter. Also, the recommended use of a posterior popliteal approach to the sciatic nerve for knee surgery or other procedures requiring a thigh tourniquet also deserves discussions. This practice has the potential for increasing the anesthesiologist’s liability in the case of nerve injury. Therefore, the choice of the sciatic approach should facilitate the differentiation between the nerve block, the tourniquet, and/or surgery itself. When the site of the block is very close to the tourniquet or surgical field, electromyographic and conduction nerve studies cannot allow such a differentiation, and by default, the anesthesiologists is usually blamed. In our practice, we favor the use of approaches away from the tourniquet and the site of the surgery.5The problem of continuous nerve blocks and anticoagulation is undoubtedly an important issue for regional anesthesiologists. In his article, the author referred to recommendations made by the American Society of Regional Anesthesiologists, but after going to the American Society of Regional Anesthesiologists Web site, we could not verify the source of these recommendations. Moreover, the authors of this letter have several thousand patient experiences with the combination of continuous lumbar plexus and thromboprophylaxis using various anticoagulants (aspirin, warfarin, low-molecular-weight heparin, and fondaparinux). As long as these anticoagulants are administered for the prevention of deep vein thrombosis and pulmonary embolism and not for their treatment, we found no reason to take any precaution when placing or removing the lumbar plexus catheter.6For total knee arthroplasty,5,7we also would like to stress the value of a continuous sciatic nerve block for postoperative analgesia. In our experience, 80% of patients undergoing total knee replacement report sciatic pain.7Finally, although the author recommended the use of 0.2% ropivacaine for perineural infusion, he also recommend the use of 0.5% bupivacaine for the initial injection. Bupivacaine is recognized to be more toxic than ropivacaine.8Therefore, it is surprising that the author would continue to recommend its use for the initial bolus injection. Certainly, in our practice, we have eliminated the use of bupivacaine.*University of Pittsburgh Medical Center, UPMC Presbyterian-Shadyside Hospital, Pittsburgh, Pennsylvania. chelje@anes.upmc.edu

The Posterior Approach to the Sciatic Nerve in the Popliteal Fossa: A Comparison of Single- Versus Double-Injection Technique

We compared single-injection and double-injection of the sciatic nerve with nerve stimulation in the posterior popliteal approach using mepivacaine 1% in a prospective, randomized and single-blind study to evaluate effectiveness, delay of onset, and complications in patients undergoing foot and ankle surgery. In the single-injection group (Group S, n = 30), 25 mL of mepivacaine 1% was administered after eliciting foot inversion or plantar flexion. In the double-injection group (Group D, n = 30), 12.5 mL of the solution was injected after eversion or dorsiflexion and 12.5 mL after plantar flexion of the foot. Mean differences (SD) between the two groups from onset time to complete sensory block were not significant (21.9 [14.2] min vs 22.1 [13.8] min) except for the superficial peroneal nerve block (18 [13] min vs 11.4 [7.5] min, Group S and D, respectively; P < 0.05) and, in Group D, between the superficial peroneal and tibial nerve blocks (11.4 [7.5] min vs 22.3 [11.3] min, respectively; P < 0.05). Complete analgesia was achieved in 77% of Group S patients and in 87% of Group D (P = 0.22). Complete analgesia of the deep peroneal nerve was achieved in 80% and 97% in Group S and D, respectively; P < 0.05. There were more paresthesias during block procedure in Group D (17% vs 40%) (P < 0.05). We conclude that double-nerve stimulation of the sciatic nerve gives similar complete onset times and overall success rate to single-nerve stimulation and more paresthesias during block performance.

A Prospective, Randomized Comparison Between the Popliteal and Subgluteal Approaches for Continuous Sciatic Nerve Block with Stimulating Catheters

In this prospective, blinded study, we randomized 56 patients undergoing hallux valgus repair to receive continuous sciatic nerve block using a subgluteal (n = 28) or a posterior popliteal approach (n = 28) with a perineural stimulating catheter. Postoperatively, the stimulating catheter was connected to a patient-controlled analgesia pump with 0.0625% levobupivacaine (basal infusion rate of 3 mL/h, patient-controlled bolus dose of 3 mL, and lockout time of 20 min). Both approaches provided similar postoperative analgesia; however, local anesthetic consumption was larger in the popliteal group (4.9 +/- 1.4 mL/h) compared with the subgluteal group (3.8 +/- 1.1 mL/h; P < 0.05). We conclude continuous postoperative analgesia using stimulating catheters was effective at both injection sites; however, a subgluteal approach reduced the overall amount of local anesthetic.

Aneurisma de artéria poplítea com rotura e formação de pseudo-aneurisma

Paciente relatava história aguda de dor e edema em membro inferior direito há 5 dias, e a semiologia caracterizava pulsos poplíteos amplos e perfusão distal satisfatória. Exames laboratoriais mostraram insuficiência renal, e o exame de ultra-som duplex evidenciou um aneurisma de artéria poplítea à direita roto, com formação de pseudo-aneurisma e um aneurisma de artéria poplítea à esquerda. O paciente foi submetido à exploração cirúrgica por via de acesso posterior, sendo evidenciado pseudo-aneurisma secundário a aneurisma de artéria poplítea roto e realizada endoaneurismorrafia com interposição de veia. A evolução pós-operatória foi boa. A ruptura de um aneurisma de artéria poplítea é uma complicação rara, e apenas um relato de formação espontânea de pseudo-aneurisma foi encontrado na literatura.

Does the Sciatic Nerve Approach Influence Thigh Tourniquet Tolerance During Below-Knee Surgery?

In this prospective, randomized, blinded study we assessed thigh tourniquet tolerance when a Labat's or a posterior popliteal approach of the sciatic nerve was used for below-knee surgery. One-hundred-twenty patients were divided into two groups of 60. A posterior popliteal (Group 1) or a Labat's (Group 2) sciatic nerve block was performed with 25 mL 1% mepivacaine + epinephrine 1:200,000. In both groups, a femoral nerve block was achieved. Patient comfort during block performance, sensory block, success rate, and thigh tourniquet tolerance were recorded. Performance of the block was significantly more comfortable in Group 1 than in Group 2 (P < 0.01). Completeness of the block at t(30 min.) and success rate were comparable in both groups. Thigh tourniquet pain increased with time in both groups. No statistically significant difference was observed between groups. We conclude that despite a complete sensory blockade of the posterior femoral cutaneous nerve in 91% of the patients, Labat's approach of the sciatic nerve provides no better thigh tourniquet tolerance than the popliteal approach. The popliteal approach is as efficient but more comfortable for the patient and is the preferred technique for below-knee surgery.

Continuous plexus and peripheral nerve blocks for postoperative analgesia.

Continuous plexus and peripheral nerve blocks for postoperative analgesia.