José Aguirre

Update on local anesthetics.

Purpose of review Local anesthetics are not only used as drugs to block the sodium channel to provide analgesia and antiarrhythmic action. The purpose of this review is to highlight the new indications and limitations of this class of drugs. Recent findings Recent research has focused on the use of intravenous local anesthetics to improve bowel function after surgery or trauma, to protect the central nervous system, to find new clues about local anesthetic effects in chronic neuropathic pain, and to investigate the long-term effect of anesthesia/analgesia provided by local anesthetics on cancer recurrence. Recent facts dealing with myotoxicity and chondrotoxicity are presented. Summary There is growing evidence that local anesthetics have a broad spectrum of indications in addition to analgesia and antiarrhythmic effect. Most of them are still insufficiently known and investigated. These new indications will no doubt be intensively studied in the coming years.

The Role of Continuous Peripheral Nerve Blocks

A continuous peripheral nerve block (cPNB) is provided in the hospital and ambulatory setting. The most common use of CPNBs is in the peri- and postoperative period but different indications have been described like the treatment of chronic pain such as cancer-induced pain, complex regional pain syndrome or phantom limb pain. The documented benefits strongly depend on the analgesia quality and include decreasing baseline/dynamic pain, reducing additional analgesic requirements, decrease of postoperative joint inflammation and inflammatory markers, sleep disturbances and opioid-related side effects, increase of patient satisfaction and ambulation/functioning improvement, an accelerated resumption of passive joint range-of-motion, reducing time until discharge readiness, decrease in blood loss/blood transfusions, potential reduction of the incidence of postsurgical chronic pain and reduction of costs. Evidence deriving from randomized controlled trials suggests that in some situations there are also prolonged benefits of regional anesthesia after catheter removal in addition to the immediate postoperative effects. Unfortunately, there are only few data demonstrating benefits after catheter removal and the evidence of medium- or long-term improvements in health-related quality of life measures is still lacking. This review will give an overview of the advantages and adverse effects of cPNBs.

Regional anaesthesia and cancer metastases: the implication of local anaesthetics

Clinical and basic science studies have demonstrated the anti‐inflammatory properties of local anaesthetics. Recent studies have begun to unravel molecular pathways linking inflammation and cancer. Regional anaesthesia is associated in some retrospective clinical studies with reduced risk of metastasis and increased long‐term survival. The potential beneficial effects of regional anaesthesia have been attributed mainly to the inhibition of the neuroendocrine stress response to surgery and to the reduction in the requirements of volatile anaesthetics and opioids. Because cancer is linked to inflammation and local anaesthetics have anti‐inflammatory effects, these agents may participate in reducing the risk of metastasis, but their mechanism of action is unknown. We demonstrated in vitro that amide local anaesthetics attenuate tumour cell migration as well as signalling pathways enhancing tumour growth and metastasis. This has provided the first evidence of a molecular mechanism by which regional anaesthesia might inhibit or reduce cancer metastases.

Continuous Epicapsular Ropivacaine 0.3% Infusion After Minimally Invasive Hip Arthroplasty: A Prospective, Randomized, Double-Blinded, Placebo-Controlled Study Comparing Continuous Wound Infusion with Morphine Patient-Controlled Analgesia

BACKGROUND: In this study, we investigated the impact of a continuous wound infusion with ropivacaine 0.3% on pain and morphine consumption after minimally invasive hip arthroplasty. METHODS: Seventy-six consecutive patients scheduled for elective minimally invasive hip replacement using spinal anesthesia were prospectively included in this double-blind study. Epicapsular placement of a 15-cm fenestrated catheter was performed by the surgeon. Patients were randomized to receive either 20 mL ropivacaine 0.3% (R-group) or 20 mL NaCl 0.9% (P-group) applied into the wound as a bolus before wound closure. A continuous infusion of either ropivacaine 0.3% or placebo was then infused at 8 mL/h for 48 hours after surgery with an elastomeric pump. Morphine IV-patient-controlled analgesia was offered to all patients. Morphine consumption, pain at rest and with motion, and total and unbound ropivacaine plasma concentration were recorded during the 48-hour study period. Postoperative follow-up was performed at 3 months. RESULTS: Demographic and surgical data were similar in both groups. Mean morphine consumption was significantly lower in the R-group than in the P-group during the first 48 postoperative hours: 45.4 ± 9.5 vs 69.7 ± 9.6 (P < 0.0001). There was a mean reduction of 14.4 mg for the first 24 postoperative hours (95% confidence interval [CI] 12.6 to 16.1) and 20.8 mg for the next 24 hours (95% CI 19.1 to 22.4). Pain scores at rest and with motion were lower in the R-group (P < 0.0001). Mean patient satisfaction increased 22.7% from baseline (CI 95% 15.9 to 29.6) in the R-group. Total and unbound ropivacaine plasma concentrations were below toxic levels in the R-group. The free ropivacaine concentration was 0.14 and 0.11 &mgr;gmol/L at T24 and T48, respectively, in the R-group. At 3 months postoperatively, hip pain and analgesic consumption were similar, but a significant reduction in wound discomfort to touch (31.2; 95% CI 27.7 to 34.7) and pressure (24; 95% CI 20.1 to 27.9) was observed in the R-group (P < 0.0001). CONCLUSIONS: Continuous epicapsular wound infusion with ropivacaine 0.3% after minimally invasive hip replacement is an efficient technique for reducing morphine consumption and improving the quality of postoperative analgesia. The beneficial effects of this technique are still present 3 months after surgery.

Continuous interscalene analgesia with ropivacaine 0.2% versus ropivacaine 0.3% after open rotator cuff repair: the effects on postoperative analgesia and motor function.

BACKGROUND: Interscalene analgesia is a recognized technique for the management of postoperative pain after major shoulder surgery. The most effective local anesthetic concentration in this setting is still controversial. In this study, we compared the analgesia and side effects of a continuous infusion of ropivacaine 0.2% and 0.3% administered through an interscalene catheter for the first 48 hours after surgery. METHODS: Eighty consecutive patients scheduled for elective open rotator cuff repair were randomized into 2 groups to receive a continuous infusion of either ropivacaine 0.2% or ropivacaine 0.3% for 48 hours at a rate of 14 mL/h through an interscalene catheter after a preoperative bolus of 40 mL ropivacaine 0.5% in all patients. Pain score (visual analog scale 0–100), intensity of motor block, quality of sleep during the first postoperative night, morphine consumption, side effects, and patient satisfaction were assessed by an anesthesiologist masked to treatment group. RESULTS: Total morphine consumption was significantly reduced in group 0.3% (12 vs 30 mg). Quality of sleep was significantly better in group 0.3% (4% vs 27% of awakening during the first postoperative night). Handgrip strength, visual analog scale scores, and side effects were similar in both groups. CONCLUSION: The use of ropivacaine 0.3% through an interscalene catheter for the first 48 hours after open rotator cuff repair provided a significant reduction of morphine consumption and a better sleep quality for the first postoperative night without increasing the intensity of motor block or side effects.

Case scenario: compartment syndrome of the forearm in patient with an infraclavicular catheter: breakthrough pain as indicator.

1198 May 2013 A compartment syndrome (ACS) represents a limb-threatening condition. Delaying diagnosis and therapy may lead to irreversible neuromuscular ischemic damages with subsequent functional deficits.1 Diagnosis is primarily clinical and characterized by a pain level that quality exceeds the clinical situation. Diagnosis is assessed by invasive pressure monitoring within the suspected compartment. Once ACS has been confirmed it represents a surgical emergency with definitive treatment requiring immediate fasciotomy to relieve the pressure within the affected compartment. Irreversible tissue damage can occur within 4–6 h after the onset of symptoms. However, nerves are already seriously damaged after 2 h of increased compartment pressure.1,2 Concerns about masking pain as cardinal symptom and therefore leading to a delay in diagnosis and therapy have been raised in connection with regional anesthesia.3,4 Moreover, several case reports and case series have blamed different types of regional anesthesia4–11 and even the use of opioid patient-controlled analgesia12 for delaying diagnosis of ACS. Therefore, the use of regional anesthesia for trauma and orthopedic surgery remains controversial.4,6,13 A case involving continuous regional anesthesia of the upper extremity and the development of an ACS is presented.

Case Scenario: Neurologic Complication after Continuous Interscalene Block

A 33-YR-OLD woman, American Society of Anesthesiologists risk classification I, was referred for surgical treatment of left shoulder instability. Her medical history was unremarkable, but she had undergone two previous shoulder surgeries: anterior stabilization of left shoulder 3 yr ago followed by a posterior Bankart stabilization 2 yr later because of recurrent luxation and pain. At examination, she still complained about pain in her left shoulder, and movement was severely limited. A left Bankart operation and capsulotomy were scheduled. A preoperative interscalene catheter was placed according to the modified lateral approach. The interscalene brachial plexus was identified using a nerve stimulator (Stimuplex® HNS II, B. Braun Melsungen AG, Melsungen, Germany) connected to the proximal end of the metal inner part of a short beveled needle. A contraction of the deltoid muscle was observed with a current output of 0.35 mA, with an impulse duration of 0.1 ms. The insertion of the perineural catheter was performed using the cannula-over-needle technique with a plastic cannula (Polymedic®, Polyplex N-50 T, 20 gauge external diameter, te me na, Bondy, France). The catheter was introduced distally between the anterior and middle scalene muscle up to 3 cm. A bolus of 30 ml ropivacaine (0.5%) was administered, and the procedure was uneventful. No pain, dysesthesias, or paresthesias occurred at any time. Fifteen minutes later, a complete sensorimotor block of the left arm was observed. Then, general anesthesia with targetcontrolled infusion (TCI Diprifusor, SIMS Graseby Ltd., Watford, Herts, United Kingdom) of propofol and remifentanil was administered. The patient was positioned in the beach chair for surgery. The procedure lasted 3 h 30 min and was described by the surgeon as difficult. Postoperative analgesia was performed with patient-controlled interscalene analgesia using ropivacaine (0.2%) and was started 4 h after the end of the surgery. The pump settings were basal rate of 5 ml/h with supplementary boli of 4 ml for every 20 min. The patient was pain free, and the patient-controlled interscalene analgesia was stopped after 54 h. Even after 36 h of termination of patient-controlled interscalene analgesia, no motor or sensory recovery was observed. An ultrasonography of the brachial plexus was performed to exclude a hematoma and revealed no irregular finding. A complete neurologic examination including neurophysiologic recordings on the following day (72 h after surgery) demonstrated a motor and sensory incomplete lesion of nerve fibers originating from the upper brachial plexus (involving the following muscles: deltoid M0/5, biceps M0/5, and triceps M3/5). Motor nerve conduction studies (figs. 1 and 2) and somatosensory-evoked potentials (SSEPs) of the median and ulnar nerves that originate from the lower brachial plexus revealed normal recordings. Electromyography at the initial examination did not show signs of denervation (fibrillation or positive waves) but resulted in complete paralysis (no retrievable voluntary electromyography activity). The later finding at this early stage after injury can be in line with a neurapraxia (conduction failure) or axonotmesis (structural neural damage). Eventually, 1 month later, at the first follow-up, electromyographies showed signs of denervation most severe within the deltoid and biceps muscles, disclosing objective signs of neural damage (fig. 3) congruent to the clinical condition in which no motor improvement was observed. Six months later, although no clinical improvement occurred, a surgical exploration was performed that revealed no pathologic findings. At this time, a perioperative stimulation of the trunks of the brachial plexus elicited reliable responses for the three trunks. In repeated electromyographic recordings during a period of 2 yr, increasing signs of motor recovery could be observed, although the patient still demonstrated severe proximal muscle weakness that could not be * Professor and Chief-of-Staff, † Consultant, Department of Anesthesiology, ‡ Professor and Chairman, Spinal Cord Injury Center, University of Zurich, Balgrist University Hospital, Zurich, Switzerland.

Ultrasound guidance and success rates of axillary brachial plexus block - I

This study warrants comment due to the low success rates reported after axillary brachial plexus block, despite the authors’ internation-ally recognized experience with these techniques. The study compared regional anesthesia of the upper limb using an ultrasound-guided (US) approach (the most expensive technique) or a combined nerve stimulator (NS) ultrasound-guided (USNS) approach (the most sophisticated technique) to NS alone. The authors reported 30-min post-block success rates of 62.9%, 80.7% and 82.8% for NS, USNS and US techniques, respectively. These success rates are considerably lower than those reported after brachial plexus block using a transarterial technique, which is no longer recom-mended. Stan et al.

Safety and effectiveness of bilateral continuous sciatic nerve block for bilateral orthopaedic foot surgery: a cohort study.

BACKGROUND Severe postoperative pain is a major problem after unilateral and bilateral foot surgery. Continuous regional anaesthesia is often used for unilateral surgery. However, for bilateral surgery, the incidence of complications of continuous bilateral compared with unilateral regional anaesthesia is unknown. OBJECTIVES To assess the incidence of catheter-related complications of bilateral compared with unilateral continuous regional anaesthesia. DESIGN A prospective observational study. SETTING Bellinzona Regional Hospital, a tertiary teaching hospital. PATIENTS Patients (n = 130) scheduled for elective bilateral or unilateral hallux valgus repair treated with continuous popliteal sciatic nerve block using a continuous infusion of ropivacaine 0.15% at 5 ml h−1 for each popliteal catheter by elastomeric pumps. INTERVENTIONS The incidence of catheter-related complications, effectiveness, pain levels at rest and with motion, patient satisfaction for the first three postoperative days and the incidence of ambulatory visits or readmissions after discharge were measured. A follow-up for neurological or other complications related to regional anaesthesia was performed 6 to 8 weeks after surgery. MAIN OUTCOME MEASURE The incidence of catheter-related complications comparing bilateral with unilateral continuous sciatic popliteal nerve block. RESULTS There were no differences in the incidence of catheter-related complications between the groups. Pain scores at rest and with motion were comparable between the groups. All patients were fit for discharge home 3 days after surgery. Patient satisfaction was similar between the groups. There were no unplanned ambulatory visits or readmissions due to complications in either group. No complications related to regional anaesthesia were reported during the follow-up. CONCLUSION The complication rate, effectiveness and patient satisfaction of bilateral continuous popliteal sciatic nerve block was comparable with unilateral continuous sciatic popliteal nerve block. The follow-up showed that bilateral continuous sciatic popliteal nerve block does not increase the complication rate. However, an outpatient-based study should confirm these data prior to introduction in the ambulatory setting.

Severe Brachial Plexopathy after an Ultrasound-guided Single-injection Nerve Block for Total Shoulder Arthroplasty in a Patient with Multiple Sclerosis: What Is the Likely Cause of This Complication?

To the Editor:—We read with interest the case report published by Koff et al. and the editorial by Hebl. How can Dr. Hebl discuss the role that the use of an ultrasound may have played in this case? Ultrasound allows us to visualize the nerves and the spread of local anesthetic. From the authors’ description, it is clear that except for the use of 0.5% bupivacaine, the technique used to perform the interscalene block could not have led to such a catastrophic outcome. The injection of local anesthetic was not intraneural, because the authors reported that “the local anesthetic was noted to surround C5–C6” and that intraneural injections have been demonstrated to produce swelling of the nerve. In addition, how would a 22-gauge blunt needle, even in the hands of a resident under the supervision of an attending, be able to damage the three trunks? What was really surprising about the case report and the editorial is that none of the authors questioned the use of 30 ml bupivacaine, 0.5%. Bupivacaine neurotoxicity is well established. Because general anesthesia was the main anesthetic technique, why did the author choose to perform an anesthetic (0.5% bupivacaine) and not an analgesic block (0.25% bupivacaine)? More importantly, why was bupivacaine chosen rather than a less toxic drug such as ropivacaine? In the presence of a theoretical increase in the possibility of nerve injury, would it be logical to choose the local anesthetic and the concentration with the least potential for neurotoxicity? There is no doubt that considerations should be given to the role played by multiple sclerosis (MS) in the postsurgical complication. Before arguments can be presented to contraindicate the use of peripheral nerve block in the patient with MS, could we at least also consider the possibility that MS might increase the surgical risk of a nerve injury, especially when considering that shoulder surgery is associated with a risk of permanent nerve injury much more frequently than peripheral nerve block? In conclusion, from the data presented, it is impossible to determine whether the complication presented was directly related to the surgery or was the result of an MS-related increase in the surgical risk or an MS-related increase in the local anesthetic toxicity. What is certain is that the use of ultrasound had nothing to do with the outcome.