[Electrical nerve localization: non-linear relationship between intensity and pulse duration to stimulate a nerve]. / Neurostimulation: relation non linéaire entre intensité et durée pour stimuler un nerf.

OBJECTIVE: When performing a peripheral nerve block, the current allowing local anaesthetic injection is between 0.3 and 0.5 mA. It has never been assessed if such a threshold remains the same whatever be the pulse duration. The aim of this study was to determine the minimal current required to stimulate a nerve while different pulse durations were applied, and to evaluate the importance of the placement of the cutaneous electrode. STUDY DESIGN: Prospective study. PATIENTS AND METHODS: One hundred and twenty posterior popliteal sciatic (S), femoral (F), or median (M) nerve blocks performed with a nerve stimulator were included. The minimal current for a clearly visible motor response of the corresponding muscle was recorded with a pulse duration set at 50, 150 and 300 micros. The same procedure was repeated with the electrode sited on the controlateral side, before injection of local anaesthetic. RESULTS: The mean lowest charge of current required to stimulate a nerve was 24+/-8 nC at 50 micros. At 150 and 300 micros, it has to be increased by 175 % (42+/-14 nC) and 280 % (67+/-23 nC), respectively. No significant difference in the charge required was noted either among S, F, or M, or by changing the cutaneous electrode position. Adequate anaesthesia was noted in all cases. CONCLUSION: The relationship between intensity and pulse duration is not linear. Moreover, a low charge of current does not seem to be appropriate with pulse duration equal or superior to 300 micros. The location of the cutaneous electrode does not seem to be important.

Extended femoral nerve sheath block after total hip arthroplasty: continuous versus patient-controlled techniques.

We assessed the efficacy of patient-controlled analgesia (PCA) techniques for extended femoral nerve sheath block after total hip arthroplasty. Forty-five patients were divided into three groups of 15. Over 48 h, all patients received 0.125% bupivacaine with clonidine 1 microg/mL and sufentanil 0.1 microg/mL via a femoral nerve sheath catheter as a continuous infusion at 10 mL/h in Group 1, as PCA boluses only of 10 mL/h in Group 2, or as PCA boluses of 5 mL per 30 min in Group 3. Pain scores, sensory block, supplemental analgesia, bupivacaine consumption, side effects, and satisfaction scores were recorded. Pain scores at rest and supplemental analgesia were comparable in the three groups. At 48 h, pain relief on movement was significantly better in Group 3 than in Group 1 (P = 0.01). Bupivacaine consumption was significantly less in Groups 2 and 3 than in Group 1 (P < 0.001). Side effects were comparable in the three groups. Satisfaction scores were significantly higher in Group 3 than in the other groups (P < 0.01). We conclude that, to maintain extended femoral nerve sheath block after total hip arthroplasty, PCA techniques reduce the local anesthetic consumption without compromise in patient satisfaction or visual analog scale scores. Of the two PCA techniques tested, PCA boluses (5 mL per 30 min) of 0.125% bupivacaine with clonidine 1 microg/mL and sufentanil 0.1 microg/mL are associated with the smallest local anesthetic consumption and the most patient satisfaction.

Clinical application of ropivacaine for the upper extremity.

Ropivacaine, the S-(-)-enantiomer of N-(2,6-dimethylphenyl)-1-propyl-2-piperidinecarboxamide is a new long-acting local anesthetic. This review demonstrates that it is effective in brachial plexus anesthesia. It is at least as efficient as bupivacaine in terms of quality, duration of analgesia, anesthesia, and motor block. It could have some advantages over bupivacaine in terms of onset time of sensory and motor block, but this remains controversial. In single-shot brachial plexus block, it is equipotent to bupivacaine and has a similar pharmacokinetic profile. Its minimal effective concentration is 0.5%, and the benefit of increasing its concentration to 0.75 or 1% remains debatable. Its use during continuous brachial plexus block has been much less studied, and conflicting results involving efficacy during continuous interscalene block and inefficacy during continuous axillary block have been obtained. Further investigations are required to assess its efficacy during such block. Because of lower CNS and cardiac toxicity, ropivacaine is safer than bupivacaine. It would be thus the preferred local anesthetic for brachial plexus blockade when long-lasting anesthesia and analgesia is required.

Regional anaesthesia for orthopaedic surgery.

Recently, there has been considerable interest in regional anaesthetic techniques, particularly in peripheral nerve blockade, for orthopaedic limb surgery. Many traditional nerve-block techniques have been significantly modified to improve their role in both in-patient and out-patient surgery. The introduction of long-acting local anaesthetic with a better safety profile as well as better equipment for continuous nerve blockade has further increased the use of such techniques in the provision of postoperative analgesia. The recent developments described in this review are likely to result in wider use of these techniques in years to come.

Extended "three-in-one" block after total knee arthroplasty: continuous versus patient-controlled techniques.

UNLABELLED: This prospective, randomized, double-blinded study assessed the efficacy of patient-controlled analgesia (PCA) techniques for extended "3-in-1" block after total knee arthroplasty. A total of 45 patients were divided into three groups of 15. Over 48 h, all patients received 0.125% bupivacaine with 1 microg/mL clonidine via a femoral nerve sheath catheter in the following manner: as a continuous infusion at 10 mL/h in Group 1; as a continuous infusion at 5 mL/h plus PCA boluses (2.5 mL/30 min) in Group 2; or as PCA boluses only (10 mL/60 min) in Group 3. Pain scores, sensory block, supplemental analgesia, bupivacaine consumption, side effects, and satisfaction scores were recorded. Pain scores and supplemental analgesia were comparable in the three groups. Bupivacaine consumption was significantly less in Groups 2 and 3 than in Group 1 (P < 0.01), and in Group 3 than in Group 2 (P < 0.01). Side effects and satisfaction were comparable in the three groups. We conclude that extended "3-in-1" block provides efficient pain relief after total knee arthroplasty and that, compared with a continuous infusion, PCA techniques reduce the local anesthetic consumption without compromise in patient satisfaction or visual analog scale scores. Of the two PCA techniques tested, PCA boluses (10-mL lockout; time, 60 min) of 0.125% bupivacaine with 1 microg/mL clonidine was associated with the smallest local anesthetic consumption, and is, therefore, the recommended extended "3-in-1" block technique. IMPLICATIONS: We demonstrated that, after total knee arthroplasty, an extended "3-in-1" block consisting of patient-controlled analgesia boluses (10 mL/60 min) of 0.125% bupivacaine with 1 microg/mL clonidine provides efficient postoperative analgesia and significantly minimizes local anesthetic consumption.

Interscalene brachial plexus analgesia after open shoulder surgery: continuous versus patient-controlled infusion.

UNLABELLED: In this prospective, randomized, double-blinded study, we assessed the efficacy of patient-controlled analgesia (PCA) for continuous interscalene analgesia after open shoulder surgery. Sixty patients were divided into three groups of 20. During a 48-h period, they received, via an interscalene catheter, a continuous infusion of 0.125% bupivacaine with sufentanil 0.1 microg/mL and clonidine 1 microg/mL at 10 mL /h in Group 1; a continuous infusion of the same solution at 5 mL/h plus PCA boluses (2.5 mL/30 min) in Group 2; and only PCA boluses (5 mL/30 min) of the same solution in Group 3. Pain scores, sensory block, supplemental analgesia, bupivacaine consumption, side effects, and satisfaction scores were recorded. At 24 and 48 h, sensory block was more frequent and pain control was significantly better in Groups 1 and 2 than in Group 3 (P < 0.001). In Group 3, larger doses of paracetamol were required. Bupivacaine consumption was significantly less in Groups 2 and 3 than in Group 1 (P < 0.001). Satisfaction was significantly higher in Groups 1 and 2 than in Group 3 (P < 0.01). Side effects were comparable in the three groups. We conclude that continuous interscalene analgesia requires a background infusion after open shoulder surgery. Because it reduces the local anesthetic consumption and allows the patients to rapidly reinforce the block shortly before physiotherapy, a basal infusion rate of 5 mL/h combined with PCA boluses (2.5 mL/ 30 min) is the recommended technique. IMPLICATIONS: In this study, we demonstrated that continuous interscalene analgesia requires a background infusion to provide efficient pain relief after open shoulder surgery. A basal infusion of 5 mL/h combined with patient-controlled analgesia boluses (2.5 mL/30 min) seems to be the most appropriate technique.

Postoperative analgesia after total hip arthroplasty: i.v. PCA with morphine, patient-controlled epidural analgesia, or continuous "3-in-1" block?: a prospective evaluation by our acute pain service in more than 1,300 patients.

STUDY OBJECTIVE: To assess the most appropriate postoperative analgesic technique after hip surgery. DESIGN: Prospective, nonrandomized study. SETTING: University hospital. PATIENTS: 1,338 ASA physical status I, II, and III patients scheduled for elective unilateral total hip arthroplasty (THA). INTERVENTIONS: During the first 48 postoperative hours, pain relief was provided by intravenous (i.v.) patient-controlled analgesia (PCA) with morphine (Group 1), continuous "3-in-1" block (Group 2), or patient-controlled epidural analgesia (PCEA) (Group 3). MEASUREMENTS AND MAIN RESULTS: During a 7.5-year period, pain scores, supplemental analgesia, satisfaction score, technical problems, and side effects were collected by our acute pain service. Postoperative pain relief was comparable in the three groups. More paracetamol was required in Group 2 (1.0 +/- 1.2 g/48 h) and Group 3 (0.9 +/- 1.3 g/48 h) than in Group 1 (0.5 +/- 1.1 g/48 h) (p < 0.01). However, only 8% of patients in Group 2 and 12% of patients in Group 3 needed an opioid. A higher incidence of technical problems was noted in Group 3 (23.4%) than in Group 1 (2.3%) or Group 2 (5.5%) (p < 0.001). A lower incidence of side effects was observed in Group 2 (23.5%) when compared with Group 1 (58.8%) and Group 3 (71.9%) (p < 0.001). Satisfaction score was significantly higher in Group 2 than in the other two groups [80 +/- 16 vs. 87 +/- 14 vs. 81 +/- 14 in Groups 1, 2, and 3 respectively (p = 0.003)]. CONCLUSION: After THA, i.v. PCA with morphine, continuous "3-in-1" block, and PCEA provided comparable pain relief. Because it induces the fewest technical problems and side effects, continuous "3-in-1" block is the preferred technique.

Effects of intravenous patient-controlled analgesia with morphine, continuous epidural analgesia, and continuous three-in-one block on postoperative pain and knee rehabilitation after unilateral total knee arthroplasty.

UNLABELLED: In this study, we assessed the influence of three analgesic techniques on postoperative knee rehabilitation after total knee arthroplasty (TKA). Forty-five patients scheduled for elective TKA under general anesthesia were randomly divided into three groups. Postoperative analgesia was provided with i.v. patient-controlled analgesia (PCA) with morphine in Group A, continuous 3-in-1 block in Group B, and epidural analgesia in Group C. Immediately after surgery, the three groups started identical physical therapy regimens. Pain scores, supplemental analgesia, side effects, degree of maximal knee flexion, day of first walk, and duration of hospital stay were recorded. Patients in Groups B and C reported significantly lower pain scores than those in Group A. Supplemental analgesia was comparable in the three groups. Compared with Groups A and C, a significantly lower incidence of side effects was noted in Group B. Significantly better knee flexion (until 6 wk after surgery), faster ambulation, and shorter hospital stay were noted in Groups B and C. However, these benefits did not affect outcome at 3 mo. We conclude that, after TKA, continuous 3-in-1 block and epidural analgesia provide better pain relief and faster knee rehabilitation than i.v. PCA with morphine. Because it induces fewer side effects, continuous 3-in-1 block should be considered the technique of choice. IMPLICATIONS: In this study, we determined that, after total knee arthroplasty, loco-regional analgesic techniques (epidural analgesia or continuous 3-in-1 block) provide better pain relief and faster postoperative knee rehabilitation than i.v. patient-controlled analgesia with morphine. Because it causes fewer side effects than epidural analgesia, continuous 3-in-1 block is the technique of choice.

Intravenous administration of tenoxicam 40 mg for post-operative analgesia: a double-blind, placebo-controlled multicentre study.

The analgesic efficacy of tenoxicam, a newer injectable non-steroidal anti-inflammatory drug, for post-operative analgesia after abdominal or orthopaedic surgery in ASA Grade I/II patients is reported. Two hundred and fifty-six patients received a single dose of tenoxicam 40 mg intravenous (i.v.) at the end of surgery and this was repeated 24 h later. These patients were compared, with respect to pain or adverse events, with 258 patients that received placebo. All patients were monitored for the next 72 h. Overall, tenoxicam provided reliable analgesia with comparable pain scores at rest, moving and coughing. The cumulative rescue PCA-morphine consumption was always lower in the tenoxicam treated patients and was most marked at 4 and 24 h after the second injection of tenoxicam. This effect was more pronounced after abdominal surgery. The intravenous administration of tenoxicam was associated with a low incidence of adverse events and a high tolerability.

Continuous popliteal sciatic nerve block: an original technique to provide postoperative analgesia after foot surgery.

Our study describes an original technique of continuous popliteal sciatic nerve block (CPSB) (Group A, 60 patients) and compares its analgesic efficacy after foot surgery with intramuscular (IM) opioids (Group B, 15 patients) and intravenous patient-controlled analgesia (IV PCA) with morphine (Group C, 45 patients). CPSB was performed using Singelyn's landmarks. The sciatic nerve was localized with a short-beveled needle connected to a peripheral nerve stimulator. A 20-gauge catheter was placed at the same depth as the needle with a Seldinger technique. Thirty milliliters of 1% mepivacaine with epinephrine 1/200,000 was injected and followed by a continuous infusion of 0.125% bupivacaine with sufentanil 0.1 microgram/mL and clonidine 1 microgram/mL at 7 mL/h for 48 h. Postoperative analgesia (intravenous [IV] propacetamol [PRO] and/or IM piritramide [DIPI]) was standardized. Postoperative pain score (PPS), supplemental analgesia, and side effects were noted. CPSB was easy to perform in 55 patients (92%). In Group A, highest and mean PPS were significantly lower, and the mean dose of PRO was reduced by 62% and 36% when compared with Group B and C, respectively. Only 8% of patients required postoperative opioid in Group A compared with 91% and 100% in Groups B and C, respectively. No immediate or delayed complications other than postoperative technical problems (kinked or broken catheter 25%) were noted in Group A. In conclusion, CPSB is easy to perform, safe, and a more efficient technique than parenteral opioid for providing postoperative analgesia after foot surgery.

A minimum dose of clonidine added to mepivacaine prolongs the duration of anesthesia and analgesia after axillary brachial plexus block.

This study assessed the minimum dose of clonidine required to prolong the duration of both anesthesia and analgesia after axillary brachial plexus blockade. Eighty patients scheduled for elective hand surgery were divided into eight groups in a randomized, double-blind fashion. An axillary brachial plexus block was performed with 40 mL 1% mepivacaine plus 1:200,000 epinephrine. The control group received no clonidine. In the other groups, increasing doses of clonidine (0.1, 0.2, 0.3, 0.4, 0.5, 1, and 1.5 micrograms/kg) were added to the local anesthetic solution. Onset time, duration of anesthesia and analgesia, postoperative pain score, intake of analgesics, and adverse effects were recorded. The eight groups were comparable in terms of onset time, postoperative pain score, and analgesic requirement. The minimum dose of clonidine required to significantly prolong the duration of analgesia and anesthesia was, respectively, 0.1 and 0.5 microgram/kg. No side effects (sedation, drowsiness, bradycardia, arterial hypotension) were reported. We conclude that the dose of clonidine required to prolong significantly the duration of both anesthesia and analgesia after axillary brachial plexus blockade is 0.5 microgram/kg and that, at this dose, clonidine may be used without important reported side effects even in outpatients.

Intravenous clonidine does not promote hypoxemia or platelet aggregation in man.

This study was designed to evaluate hypoxemia and platelet aggregation in man following intravenous administration of clonidine. With Institutional approval and following informed consent, 20 patients (ASA I-II) without spontaneous or drug-induced coagulation disorder undergoing elective total hip replacement were studied. They were randomly divided into two groups. Group A (n = 10) received an IV loading dose of 4 micrograms/kg of clonidine in 30 minutes followed by an infusion of 1 microgram/kg/h till the end of the procedure. Group B (n = 10) received saline. Platelet aggregation was assessed before infusion and at the end of both the loading dose and the infusion. PaO2 was measured before anesthesia (FIO2 = 0.21), before femoral cementation (FIO2 = 0.40), 2 min. after prosthesis implantation (FIO2 = 1), before the end of the procedure (FIO2 = 0.40) and in the recovery room (spontaneous breathing with FIO2 = 0.21). Plasma clonidine levels were assessed at the end of both the loading dose and the infusion. At any time considered, no statistical differences were noted between the groups for platelet aggregation and PaO2. We conclude that intravenous clonidine does not clinically promote platelet aggregation nor hypoxemia in man.

Adding clonidine to mepivacaine prolongs the duration of anesthesia and analgesia after axillary brachial plexus block.

BACKGROUND AND OBJECTIVES: This study evaluates the effects of clonidine added to mepivacaine on the duration of anesthesia and analgesia after axillary brachial plexus block. METHODS: Thirty patients scheduled for elective hand surgery were divided into three equal groups in a randomized, double-blinded fashion. An axillary perivascular brachial plexus block was performed with 40 ml 1% mepivacaine plus 1:200,000 epinephrine in the three groups. Group B also received 150 micrograms clonidine subcutaneously and Group C had the same dose of clonidine mixed with the local anesthetic and injected into the plexus sheath. The following variables were recorded: onset time, duration of anesthesia, duration of analgesia, postoperative pain score, intake of analgesics, and adverse effects. RESULTS: The three groups were comparable in terms of age, sex, weight, height, onset time of anesthesia, postoperative pain score, and analgesic requirement. The duration of anesthesia and analgesia was comparable in Groups A and B, but both variables were significantly increased in Group C: the duration of anesthesia and analgesia were prolonged, respectively, by 37 +/- 6% and 103 +/- 16% when compared to Group A and by 32 +/- 7% and 89 +/- 15% when compared to Group B. No side effects were reported. CONCLUSIONS: One hundred fifty micrograms clonidine added to mepivacaine for brachial plexus block prolongs the duration of anesthesia and analgesia. Our results suggest that this effect of clonidine is local rather than systemic.

Popliteal sciatic nerve block aided by a nerve stimulator: a reliable technique for foot and ankle surgery.

The reliability of popliteal sciatic nerve blocks was prospectively assessed in 625 blocks performed in 507 patients. The sciatic nerve was approached at the apex of the popliteal fossa, in the midline, with an insulated needle connected to a peripheral nerve stimulator partially designed by one of the authors. When needed, an inguinal paravascular femoral nerve block was also performed. The drugs used were 1% mepivacaine or 0.5% bupivacaine with or without 1:200,000 epinephrine. The sciatic and femoral nerves were blocked with 30 ml and 10 ml of local anesthetic, respectively. The block was sufficient to provide surgical anesthesia in 92%; supplemental analgesia was necessary in 5% and general anesthesia was required in 3% of the cases. Discomfort associated with the block procedure was found to be minimal by 89% of the patients, moderate by 9% and severe by 2%. Overall satisfaction with perioperative analgesia was evaluated by 466 patients: 444 (95%) were completely satisfied, 20 (4%) expressed moderate reservations and two (1%) expressed major reservations. The authors conclude that the technique is a safe and reliable alternative to more common forms of anesthesia for surgery below the knee. They attribute the great success rate to a high popliteal approach, the use of insulated needles, a discriminating mode of nerve stimulation and the systematic search for optimal response to needle stimulation.