Subparaneural versus circumferential extraneural injection at the bifurcation level in ultrasound-guided popliteal sciatic nerve blocks: a prospective, randomized, double-blind study.

BACKGROUND: The ideal spread of local anesthetic for effective, rapid, and safe sciatic nerve block is debated. We hypothesized that subparaneural ultrasound-guided injection results in faster onset and has a better success rate than extraneural circumferential spread. METHODS: Patients undergoing elective tibial, foot, and ankle surgery with popliteal sciatic nerve blocks were prospectively enrolled. After randomization, the needle tip position was adjusted to ensure circumferential extraneural or subparaneural spread; 0.3 mL/kg of mepivacaine 10 mg/mL was injected. Post hoc video analysis was used to group the patients according to extraneural, subparaneural, and unintentional intraepineural spread. RESULTS: There were 26 (43.3%) patients in the subparaneural group and 22 (36.7%) in the extraneural group. Block onset time was shorter in the subparaneural group than in the extraneural group (11 [3-21] minutes; mean [95% confidence interval], 11 [8.97-13.02] minutes and 17 [6-30] minutes; mean [95% confidence interval] 18.37 [14.17-22.57] minutes, respectively; P = 0.002). The duration of sensory blockade increased (397 [178-505] minutes vs 265 [113-525] minutes; P = 0.04). The success rate of the block also increased. Unintentional intraepineural injection occurred in 8% of patients (3 patients in the subparaneural group and 1 patient in the extraneural group; NS). Block onset time was shorter than for the subparaneural and extraneural groups (6 [3-12] minutes, 12 [3-21] minutes, and 18 [6-30] minutes; P = 0.01). CONCLUSIONS: A subparaneural injection accelerated the onset time and increased the duration of tibial nerve sensory blockade compared with circumferential extraneural injection. With unintentional intraepineural spread, the onset time was significantly shorter than for the other groups.

A comparison of three techniques (local anesthetic deposited circumferential to vs. above vs. below the nerve) for ultrasound guided femoral nerve block.

BACKGROUND: Fractured neck of femur generally requires operative fixation and is a common cause of admission to hospital. The combination of femoral nerve block and spinal anesthesia is a common anesthetic technique used to facilitate the surgical procedure. The optimal disposition of local anesthetic (LA) relative the femoral nerve (FN) has not been defined. Our hypothesis was: that the deposition of LA relative to the FN influences the quality of analgesia for positioning of the patient for performance of spinal anesthesia. The primary outcome was verbal rating (VRS) pain scores 0-10 assessed immediately after positioning the patient to perform spinal anesthesia. METHODS: With Institutional ethical approval and having obtained written informed consent from each, 52 patients were studied. The study was registered with ClinicalTrials.gov (NCT01527812). Patients were randomly allocated to undergo to one of three groups namely: intention to deposit lidocaine 2% (15 ml) i. above (Group A), ii. below (Group B), iii. circumferential (Group C) to the FN. A blinded observer assessed i. the sensory nerve block (cold) in the areas of the terminal branches of the FN and ii. VRS pain scores on passive movement from block completion at 5 minutes intervals for 30 minutes. Immediately after positioning the patient for spinal anesthesia, VRS pain scores were recorded. RESULTS: Pain VRS scores during positioning were similar in the three groups [Above group/Below group/Circumferential group: 2(0-9)/0(0-10)/3(0-10), median(range), p:0.32]. The block was deemed to have failed in 20%, 47% and 12% in the Above group, Below group and Circumferential group respectively. The median number of needle passes was greater in the Circumferential group compared with the Above group (p:0.009). Patient satisfaction was greatest in the Circumferential group [mean satisfaction scores were 83.5(19.8)/88.1(20.5)/93.8(12.3), [mean(SD), p=0.04] in the Above, Below and Circumferential groups respectively. CONCLUSIONS: We conclude that there is no clinical advantage to attempting to deposit LA circumferential to the femoral nerve (relative to depositing LA either above or below the nerve), during femoral nerve block in this setting.

Where should the tip of the needle be located in ultrasound-guided peripheral nerve blocks?

PURPOSE OF REVIEW: Data now exist describing the appropriate positioning of the needle tip and pattern of local anaesthetic spread after injection. The recent literature has been analysed in search of studies on the optimal procedure for common approaches centred on block efficacy, performance time, and safety. RECENT FINDINGS: Large peripheral nerves are surrounded by a gliding layer, the adventitia or paraneurium. Ultrasonically, a circumneural spread corresponds to adventitial extraneural injection. Nerve expansion with fascicular separation matches intraneural injection. Deliberate intraneural injection remains controversial, and is not advisable at the present time. For popliteal sciatic nerve blocks, positioning the needle in the common nerve sheath between the tibial and peroneal components and obtaining a circumneural spread surrounding both divisions predict rapid surgical anaesthesia. Using axillary and infraclavicular approaches, ultrasound-guided perivascular injection aiming at circumferential spread around the artery appears a valuable alternative to individual targeted nerve injections. For single injection interscalene block, an injection into the fascial sheath but far from the plexus proved to be as effective as an injection adjacent to the nerve structures. Fascial plane approaches are appealing alternatives for thin nerves that run between muscles and cannot be regularly visualized with the current resolution of ultrasound systems. SUMMARY: The ultrasound appearance of nerves and target injections are better understood. The specific distributions of local anaesthetic spread that predict success are significantly different from one anatomical site to another. It seems advisable to avoid intraneural injection.

Hemodynamic profile of target-controlled spinal anesthesia compared with 2 target-controlled general anesthesia techniques in elderly patients with cardiac comorbidities.

BACKGROUND AND OBJECTIVES: The impact of anesthesia techniques in patients experiencing hip fracture is controversial. This study compares the effects on blood pressure of 3 anesthesia techniques that are considered safe for the elderly. METHODS: Forty-five patients older than 75 years, with American Society of Anesthesiologists physical status III or IV, with cardiac comorbidities, and undergoing surgery for hip fracture, were randomized to receive continuous spinal anesthesia (CSA), propofol target-controlled infusion (TCI), or sevoflurane (SEVO). In CSA patients, a T10 metameric level target was achieved by titration of 2.5 mg of bupivacaine boluses. In patients on TCI and SEVO, a bispectral value target of around 50 guided the concentration of propofol or sevoflurane. Analgesia in the TCI and SEVO groups was provided with remifentanil. Hypotension was defined as a 30% decrease in mean arterial pressure and was treated with an intravenous bolus of ephedrine. RESULTS: The number of hypotension episodes was lower in the CSA group: 0 (range, 0-6) versus 11.5 (range, 1-25) in the TCI group and 10 (range, 1-23) in the SEVO group (P < 0.001). Both TCI and SEVO patients needed more ephedrine compared with CSA patients (30.5 [15.5], 26 [23], and 1.5 [2.5] mg, respectively, P < 0.001). The maximal decrease in mean arterial pressure was lower in the CSA group (26% [17%]) compared with that in the TCI group (47% [8%]) and the SEVO group (46% [12%]; P < 0.001). CONCLUSIONS: In elderly patients, spinal anesthesia using titrated doses of bupivacaine provided better blood pressure stability than propofol or sevoflurane anesthesia.

Femoral nerve blockade.

Femoral nerve blockade is the most widely performed lower limb block. Methods of femoral nerve blockade are briefly reviewed with particular reference to ultrasound guidance.

The ultrasound-guided transversus abdominis plane block for anterior iliac crest bone graft postoperative pain relief: a prospective descriptive study.

BACKGROUND: Acute postoperative pain and nerve injuries frequently lead to neuropathic chronic pain after anterior iliac crest (AIC) bone graft. This prospective study evaluated postoperative pain relief after preoperative ultrasound-guided transversus abdominis plane (TAP) block for orthopedic surgery with an AIC bone harvest and the prevalence of pain chronicization at 18 months after surgery. METHODS: Thirty-three consecutive patients scheduled for major orthopedic surgery with an AIC harvest for autologous bone graft were studied. Preoperative TAP blocks were performed under in-plane needle ultrasound guidance, anterior to the midaxillary line (15 mL ropivacaine 0.33%). The extent of sensory blockade was evaluated at 20 mins with cold and light-touch tests. Pain at the iliac crest graft site was assessed at rest by visual analog scale (VAS) scores in the postanesthetic care unit, and at 1, 6, 12, 24, and 48 hrs after surgery. Time for first request of morphine and total morphine consumption were recorded. Eighteen months after surgery, each patient was interviewed by phone about the importance and localization of pain chronicization. RESULTS: Median VAS score was 0 (range, 0-7) at all periods of assessment. At 20 mins, 62.5% of the patients reported complete anesthesia, and 34% hypoesthesia. The sensory blockade extent ranged from T9 (T7-T11) to L1 (T11-L2) in median (range) values. At 18 months, 80% of patients did not complain about pain or discomfort at the iliac crest site; 20% reported pain chronicization at the iliac crest site (VAS scores 2-4). Five patients (26%) complained about numbness at the iliac crest area. CONCLUSIONS: Ultrasound-guided TAP block is an appropriate technique for postoperative analgesia after AIC bone harvest in orthopedic surgery.

Ultrasound-guided evaluation of the local anesthetic spread parameters required for a rapid surgical popliteal sciatic nerve block.

BACKGROUND: The ideal spread of local anesthetic (LA) solution around the sciatic nerve during a popliteal block remains unclear. We tested the hypothesis that a circumferential spread of LA and/or intraneural injection could lead to rapid surgical block. METHODS: Patients (n = 100) scheduled for foot or ankle surgery underwent popliteal sciatic nerve block using nerve stimulation according to Borgeat's technique and injection of ropivacaine (0.5 mL/kg). Sensory and motor blockades were assessed on the tibial nerve (TN) and common peroneal nerve (CPN) at 5, 15, and 30 mins after completion of the block and in the recovery room. A successful block was defined as a complete sensory block in TN and CPN. Changes in cross-sectional and longitudinal surfaces and diameters and the characteristics of LA spread around the nerve were noted using ultrasound. A suspected intraneural injection was defined as a 15% increase in the surface area or anteroposterior diameter of the nerve. Patients were followed up on days 1 and 7 after surgery. RESULTS: Successful block was noted in 57% of patients at 30 mins and in 88% of patients in the recovery room. A circumferential spread of LA occurred in 47% of patients and 53% had noncircumferential spread. Complete sensory block was significantly higher in the group that had a circumferential spread (73% vs 43%, P = 0.035) only at 30 mins. In the postoperative care unit, there was no difference among the groups. Separated circumferential spreads around TN and CPN were noted in 12% of patients. All of these patients had a complete sensory and motor blockade at 15 mins. Concerning intraneural injection, only the change in the anteroposterior diameter on a 6-cm length of nerve was associated with a higher success and faster onset block at 5 (P = 0.008), 15 (P = 0.02), and 30 (P = 0.05) mins. There were no clinically detectable nerve injuries at follow-up. CONCLUSION: For popliteal sciatic nerve block, circumferential spread of LA, and separation of the nerve into its 2 components are associated with rapid surgical block.

Age-dependent bupivacaine-induced muscle toxicity during continuous peripheral nerve block in rats.

BACKGROUND: Regional blocks improve postoperative analgesia and postoperative rehabilitation in children and adult patients. Continuous peripheral nerve blocks have been proposed as safe and effective techniques for postoperative pain relief and chronic pain therapy, particularly in small children. Few clinical reports have described myotoxicity induced by bupivacaine in these young patients, in contrast with a larger number of observations in adults. Here, the authors addressed this issue by a comparative evaluation of bupivacaine-induced myotoxicity in young versus adult rats. METHODS: Femoral nerve block catheters were inserted in male Wistar rats. Young (3-week-old) and adult (12-week-old) rats were randomly assigned to received seven injections (1 ml/kg) of 0.25% bupivacaine (n = 6 per experiment) or isotonic saline (n = 6 per experiment) at 8-h intervals. Rats were killed 8 h after the last injection. Psoas muscle adjacent to the femoral nerve was quickly dissected. Oxygen consumption rates were measured in saponin-skinned fibers, mitochondrial adenosine triphosphate synthesis rates were determined by bioluminescence, and citrate synthase activity was determined by spectrophotometry. Muscle ultrastructural damage was also examined and scored as normal, focal disruption, moderate disruption, or extreme disruption of the sarcomeres. RESULTS: Bupivacaine caused a reduction of mitochondrial adenosine triphosphate synthesis rate, a decrease of citrate synthase activity, and muscle ultrastructural damages. Young rats treated with bupivacaine showed more severe alterations of mitochondrial bioenergetics and muscle ultrastructure. CONCLUSIONS: These findings demonstrate that bupivacaine-induced myotoxicity can be explained by mitochondrial bioenergetics alterations, which are more severe in young rats.

Effects of intermittent femoral nerve injections of bupivacaine, levobupivacaine, and ropivacaine on mitochondrial energy metabolism and intracellular calcium homeostasis in rat psoas muscle.

BACKGROUND: Long-acting local anesthetics cause muscle damage. Moreover, long-acting local anesthetics act as uncoupler of oxidative phosphorylation in isolated mitochondria and enhance sarcoplasmic reticulum Ca(2+) release. The aim of the study was to evaluate effects of perineural injections of local anesthetics on mitochondrial energetic metabolism and intracellular calcium homeostasis in vivo. METHODS: Femoral nerve block catheters were inserted in adult male Wistar rats. Rats were randomized and received seven injections (1 ml/kg) of bupivacaine, levobupivacaine, ropivacaine, or isotonic saline at 8-h intervals. Rats were killed 8 h after the last injection. Psoas muscle was quickly dissected from next to the femoral nerve. Local anesthetic concentrations in muscle were determined. Oxidative capacity was measured in saponin-skinned fibers. Oxygen consumption rates were measured, and mitochondrial adenosine triphosphate synthesis rate was determined. Enzymatic activities of mitochondrial respiratory chain complexes were evaluated. Local calcium release events (calcium sparks) were analyzed as well as sarcoplasmic reticulum calcium content in saponin-skinned fibers. RESULTS: Eight hours after the last injection, psoas muscle concentration of local anesthetics was less than 0.3 microg/g tissue. Adenosine triphosphate synthesis and adenosine triphosphate-to-oxygen ratio were significantly decreased in the muscle of rats treated with local anesthetics. A global decrease (around 50%) in all of the enzyme activities of the respiratory chain was observed. Levobupivacaine increased the amplitude and frequency of the calcium sparks, whereas lower sarcoplasmic reticulum calcium content was shown. CONCLUSION: Bupivacaine, levobupivacaine, and ropivacaine injected via femoral nerve block catheters induce a deleterious effect in mitochondrial energy, whereas only levobupivacaine disturbs calcium homeostasis.

Postoperative analgesia after total-hip arthroplasty: Comparison of intravenous patient-controlled analgesia with morphine and single injection of femoral nerve or psoas compartment block. a prospective, randomized, double-blind study.

BACKGROUND: The authors compared the analgesic effects and quality of rehabilitation of three analgesic techniques after total-hip arthroplasty in a double-blind, randomized trial. METHODS: Forty-five patients were assigned to 1 of 3 groups, patient-controlled analgesia with morphine (PCA), femoral nerve block (FNB), or psoas compartment block (PCB). At the end of the procedure performed under general anesthesia, nerve blocks using 2 mg/kg of 0.375% bupivacaine and 2 microg/kg of clonidine were performed in the FNB (n = 16) and PCB (n = 15) groups. In the recovery room, all 3 groups received initial intravenous morphine titration if their pain score was higher than 30 on a 100-mm visual analog scale (VAS), and then a PCA device was initiated. Morphine consumption was the primary end point to assess postoperative analgesia. RESULTS: After extubation (H0), morphine titration was higher in the PCA group (P <.05). During the first 4 postoperative hours (H0 to H4), morphine consumption per hour and VAS pain score were lower in the PCB group (P <.05). After H4, there was no difference in morphine consumption and VAS among groups, either at rest or during mobilization. After H4, morphine consumption remained lower than 0.5 mg/h, and VAS remained lower than 30 mm in the 3 groups. In 4 patients of the PCB group, an epidural diffusion was noted. Hip mobility and length of stay in the rehabilitation center were not different among the groups. CONCLUSIONS: PCA is an efficient and safe analgesia technique. FNB and PCB should not be used routinely after total-hip arthroplasty.

Comparison of continuous 3-in-1 and fascia Iliaca compartment blocks for postoperative analgesia: feasibility, catheter migration, distribution of sensory block, and analgesic efficacy.

BACKGROUND AND OBJECTIVES: Efficacy and technical aspects of continuous 3-in-1 and fascia iliaca compartment blocks were compared. METHODS: Forty-four patients scheduled for cruciate ligament repair or femur surgery were randomly divided into 2 groups. After surgery with the patient anesthetized, catheters were placed for continuous 3-in-1 blocks by means of a nerve stimulator (group 1). In group 2, the catheter was inserted for continuous fascia iliaca compartment block without the use of a nerve stimulator. In both groups, a 5-mg/kg bolus of 0.5% ropivacaine was administered followed by continuous infusion of 0.1 mL/kg/h of 0.2% ropivacaine for 48 hours. In the postoperative period, all the patients received parenteral propacetamol (6 g daily) and ketoprofen (200 mg daily) and 0.1 mg/kg of subcutaneous morphine as rescue analgesia if the visual analog scale (VAS) pain values were greater than 30 mm. We evaluated the technical difficulties relative to catheter placement, the location of the catheter, the analgesic efficacy, and the distribution of the sensory block at 1 hour, 24 hours, and 48 hours. RESULTS: Catheter placement was faster in group 2, and the absence of nerve stimulation decreased material costs (P <.05). No significant difference was observed between groups concerning location of the catheter tip under the fascia iliaca. In both groups, the distribution of the sensory block and its course were similar except for those of the obturator nerve (more sensory blocks in group 1, P <.05). No significant difference was noted between the groups regarding median VAS pain values and consumption of morphine during the 48-hour period. No major side effect was observed. CONCLUSIONS: The authors conclude that a catheter for continuous lumbar plexus block can be placed more quickly and at lesser cost using the fascia iliaca technique than the perivascular technique with equivalent postoperative analgesic efficacy.

Continuous three-in-one block for postoperative pain after lower limb orthopedic surgery: where do the catheters go?

UNLABELLED: Continuous three-in-one block is widely used for postoperative analgesia after proximal lower limb surgery, but location of the catheter has not been well addressed in the literature. We prospectively studied, in 100 patients, the characteristics of catheter threading under the iliac fascia and the correlations between catheter tip location and effective sensory and motor blockade of the three principal nerves of the lumbar plexus. Postoperatively, in conscious patients, 16 to 20 cm of a catheter was placed in the fascial sheath after femoral nerve location with a nerve stimulator. Contrast media (3 mL Iopamidol 390) was injected, and the catheter tip was located by means of an anteroposterior pelvic radiograph. An equal-volume mixture of 0.5% bupivacaine/2% lidocaine with epinephrine (30 mL) was injected through the catheter. Patient and catheter-insertion characteristics were noted. Thirty minutes after injection, sensory blockade was evaluated in the cutaneous territories of the lateral femoral cutaneous, femoral, and obturator nerves, along with motor blockade of the last two nerves. Pain scores at 30 min were also recorded. Seven block failures were noted. The tip of the catheter reached the lumbar plexus (Group 1) in 23% of the patients and lay deep to the medial (Group 2) or lateral (Group 3) part of the fascia iliaca in 33% and 37% of the patients, respectively. Demographic data and catheter threading characteristics were comparable among the groups. A three-in-one block was noted in 91% of Group 1 patients, but in only 52% and 27% of Group 2 and 3 patients, respectively (P < 0.05). Comparing Group 2 and 3 patients, sensory block was achieved in respectively 100% and 94% for the femoral nerve, 52% and 94% for the lateral femoral cutaneous nerve (P < 0.05), and 82% and 27% for the obturator nerve (P < 0.05). Visual analog scale pain scores on movement were significantly lower in Group 1 patients (P < 0.05). We conclude that during a continuous three-in-one block, the threaded catheter rarely reached the lumbar plexus. The quality of sensory and motor blockade and initial pain relief depend on the location of the catheter tip under the fascia iliaca. IMPLICATIONS: The course of a continuous three-in-one block catheter is unpredictable. Only 23% of the catheters lie near the lumbar plexus. The success of sensory and motor blocks, as well as postoperative analgesia, depend on the position of the catheter under the fascia iliaca.