Sarah J. Madison

Continuous Femoral Nerve Blocks: Varying Local Anesthetic Delivery Method (Bolus versus Basal) to Minimize Quadriceps Motor Block while Maintaining Sensory Block

Background: Whether the method of local anesthetic administration for continuous femoral nerve blocks—basal infusion versus repeated hourly bolus doses—influences block effects remains unknown. Methods: Bilateral femoral perineural catheters were inserted in volunteers (n = 11). Ropivacaine 0.1% was concurrently administered through both catheters: a 6-h continuous 5 ml/h basal infusion on one side and 6 hourly bolus doses on the contralateral side. The primary endpoint was the maximum voluntary isometric contraction (MVIC) of the quadriceps femoris muscle at hour 6. Secondary endpoints included quadriceps MVIC at other time points, hip adductor MVIC, and cutaneous sensation 2 cm medial to the distal quadriceps tendon in the 22 h after initiation of local anesthetic administration. Results: Quadriceps MVIC for limbs receiving 0.1% ropivacaine as a basal infusion declined by a mean (SD) of 84% (19) compared with 83% (24) for those receiving 0.1% ropivacaine as repeated bolus doses between baseline and hour 6 (paired t test P = 0.91). Intrasubject comparisons (left vs. right) also reflected a lack of difference: the mean basal-bolus difference in quadriceps MVIC at hour 6 was −1.1% (95% CI −22.0–19.8%). The similarity did not reach the a priori threshold for concluding equivalence, which was the 95% CI decreasing within ± 20%. There were similar minimal differences in the secondary endpoints during local anesthetic administration. Conclusions: This study did not find evidence to support the hypothesis that varying the method of local anesthetic administration—basal infusion versus repeated bolus doses—influences continuous femoral nerve block effects to a clinically significant degree.

Liposomal bupivacaine as a single-injection peripheral nerve block: a dose-response study.

BACKGROUND: Currently available local anesthetics approved for single-injection peripheral nerve blocks have a maximum duration of <24 hours. A liposomal bupivacaine formulation (EXPAREL®, Pacira Pharmaceuticals, Inc., San Diego, CA), releasing bupivacaine over 96 hours, recently gained Food and Drug Administration approval exclusively for wound infiltration but not peripheral nerve blocks. METHODS: Bilateral single-injection femoral nerve blocks were administered in healthy volunteers (n = 14). For each block, liposomal bupivacaine (0–80 mg) was mixed with normal saline to produce 30 mL of study fluid. Each subject received 2 different doses, 1 on each side, applied randomly in a double-masked fashion. The end points included the maximum voluntary isometric contraction (MVIC) of the quadriceps femoris muscle and tolerance to cutaneous electrical current in the femoral nerve distribution. Measurements were performed from baseline until quadriceps MVIC returned to 80% of baseline bilaterally. RESULTS: There were statistically significant dose responses in MVIC (0.09%/mg, SE = 0.03, 95% confidence interval [CI], 0.04–0.14, P = 0.002) and tolerance to cutaneous current (−0.03 mA/mg, SE = 0.01, 95% CI, −0.04 to −0.02, P < 0.001), however, in the opposite direction than expected (the higher the dose, the lower the observed effect). This inverse relationship is biologically implausible and most likely due to the limited sample size and the subjective nature of the measurement instruments. While peak effects occurred within 24 hours after block administration in 75% of cases (95% CI, 43%–93%), block duration usually lasted much longer: for bupivacaine doses >40 mg, tolerance to cutaneous current did not return to within 20% above baseline until after 24 hours in 100% of subjects (95% CI, 56%–100%). MVIC did not consistently return to within 20% of baseline until after 24 hours in 90% of subjects (95% CI, 54%–100%). Motor block duration was not correlated with bupivacaine dose (0.06 hour/mg, SE = 0.14, 95% CI, −0.27 to 0.39, P = 0.707). CONCLUSIONS: The results of this investigation suggest that deposition of a liposomal bupivacaine formulation adjacent to the femoral nerve results in a partial sensory and motor block of >24 hours for the highest doses examined. However, the high variability of block magnitude among subjects and inverse relationship of dose and response magnitude attests to the need for a phase 3 study with a far larger sample size, and that these results should be viewed as suggestive, requiring confirmation in a future trial.

A randomized comparison of infraclavicular and supraclavicular continuous peripheral nerve blocks for postoperative analgesia.

Background: Although the efficacy of single-injection supraclavicular nerve blocks is well established, no controlled study of continuous supraclavicular blocks is available, and their relative risks and benefits remain unknown. In contrast, the analgesia provided by continuous infraclavicular nerve blocks has been validated in randomized controlled trials. We therefore compared supraclavicular with infraclavicular perineural local anesthetic infusion following distal upper-extremity surgery. Methods: Preoperatively, subjects were randomly assigned to receive a brachial plexus perineural catheter in either the infraclavicular or supraclavicular location using an ultrasound-guided nonstimulating catheter technique. Postoperatively, subjects were discharged home with a portable pump (400-mL reservoir) infusing 0.2% ropivacaine (basal rate of 8 mL/hr; 4-mL bolus dose; 30-min lockout interval). Subjects were followed up by telephone on an outpatient basis. The primary outcome was the average pain score on the day after surgery. Results: Sixty subjects were enrolled, with 31 and 29 randomized to receive an infraclavicular and supraclavicular catheter, respectively. All perineural catheters were successfully placed per protocol. Because of protocol violations and missing data, an intention-to-treat analysis was not used; rather, only subjects with catheters in situ and whom we were able to contact were included in the analyses. The day after surgery, subjects in the infraclavicular group reported average pain as median of 2.0 (10th-90th percentiles, 0.5-6.0) compared with 4.0 (10th-90th percentiles, 0.6-7.7) in the supraclavicular group (P = 0.025). Similarly, least pain scores (numeric rating scale) on postoperative day 1 were lower in the infraclavicular group compared with the supraclavicular group (0.5 [10th-90th percentiles, 0.0-3.5] vs 2.0 [10th-90th percentiles, 0.0-4.7], respectively; P = 0.040). Subjects in the infraclavicular group required less rescue oral analgesic (oxycodone, in milligrams) for breakthrough pain in the 18 to 24 hrs after surgery compared with the supraclavicular group (0.0 [10th-90th percentiles, 0.0-5.0] vs 5.0 [10th-90th percentiles, 0.0-15.0], respectively; P = 0.048). There were no statistically significant differences in other secondary outcomes. Conclusions: A local anesthetic infusion via an infraclavicular perineural catheter provides superior analgesia compared with a supraclavicular perineural catheter.

Continuous femoral versus posterior lumbar plexus nerve blocks for analgesia after hip arthroplasty: a randomized, controlled study.

BACKGROUND:Hip arthroplasty frequently requires potent postoperative analgesia, often provided with an epidural or posterior lumbar plexus local anesthetic infusion. However, American Society of Regional Anesthesia guidelines now recommend against epidural and continuous posterior lumbar plexus blocks during administration of various perioperative anticoagulants often administered after hip arthroplasty. A continuous femoral nerve block is a possible analgesic alternative, but whether it provides comparable analgesia to a continuous posterior lumbar plexus block after hip arthroplasty remains unclear. We therefore tested the hypothesis that differing the catheter insertion site (femoral versus posterior lumbar plexus) after hip arthroplasty has no impact on postoperative analgesia. METHODS:Preoperatively, subjects undergoing hip arthroplasty were randomly assigned to receive either a femoral or a posterior lumbar plexus stimulating catheter inserted 5 to 15 cm or 0 to 1 cm past the needle tip, respectively. Postoperatively, patients received perineural ropivacaine, 0.2% (basal 6 mL/hr, bolus 4 mL, 30-minute lockout) for at least 2 days. The primary end point was the average daily pain scores as measured with a numeric rating scale (0–10) recorded in the 24-hour period beginning at 07:30 the morning after surgery, excluding twice-daily physical therapy sessions. Secondary end points included pain during physical therapy, ambulatory distance, and supplemental analgesic requirements during the same 24-hour period, as well as satisfaction with analgesia during hospitalization. RESULTS:The mean (SD) pain scores for subjects receiving a femoral infusion (n = 25) were 3.6 (1.8) versus 3.5 (1.8) for patients receiving a posterior lumbar plexus infusion (n = 22), resulting in a group difference of 0.1 (95% confidence interval −0.9 to 1.2; P = 0.78). Because the confidence interval was within a prespecified −1.6 to 1.6 range, we conclude that the effect of the 2 analgesic techniques on postoperative pain was equivalent. Similarly, we detected no differences between the 2 treatments with respect to the secondary end points, with one exception: subjects with a femoral catheter ambulated a median (10th–90th percentiles) 2 (0–17) m the morning after surgery, in comparison with 11 (0–31) m for subjects with a posterior lumbar plexus catheter (data nonparametric; P = 0.02). CONCLUSIONS:After hip arthroplasty, a continuous femoral nerve block is an acceptable analgesic alternative to a continuous posterior lumbar plexus block when using a stimulating perineural catheter. However, early ambulatory ability suffers with a femoral infusion.

The sciatic nerve and knee arthroplasty: to block, or not to block--that is the question.

T ricompartment (total) knee arthroplasty (TKA) consistently results in severe postoperative pain. Although providing a femoral nerve block dramatically improves analgesia, 80% to 90% of patients still experience pain requiring treatment with intravenous opioids in the immediate postoperative period.2,3 This pain is usually attributed to the sciatic and obturator nerves that contribute innervation to the knee joint, albeit less extensively than the femoral nerve. Although a lumbar epidural infusion will affect all 3 nerves, multiple investigations suggest that a continuous femoral nerve block offers similar analgesia with a more favorable adverse effect profile and is thus often cited as the ‘‘gold standard’’ following TKA. However, little consensus has emerged regarding the routine addition of a single-injection or continuous sciatic nerve block. This question is of great interest to health care providers considering the frequency that TKA is performed: more than 500,000 cases annually in the United States alone, with this number growing to 3.5 million in fewer than 20 years.

Discharge readiness after tricompartment knee arthroplasty: Adductor canal versus femoral continuous nerve blocks-a dual-center, randomized trial

Background:The authors conducted a randomized, controlled, parallel-arm, superiority study to test the hypothesis that a continuous adductor canal block decreases the time to attain four discharge criteria compared with a continuous femoral nerve block after tricompartment knee arthroplasty. Methods:Subjects undergoing tricompartment knee arthroplasty were randomized using computer-generated lists to either an adductor canal or femoral perineural catheter (3-day ropivacaine 0.2% infusion) in an unmasked manner. The primary outcome was the time to attain four criteria: (1) adequate analgesia; (2) intravenous opioids independence; (3) ability to stand, walk 3 m, return, and sit down; and (4) ambulate 30 m. Results:Subjects with an adductor canal catheter (n = 39) reached all four criteria in a median of 55 h (interquartile, 42 to 63 h) compared with 61 h (49 to 69 h) for those with a femoral catheter (n = 41; 95% CI, −13 to 1 h; P = 0.12). The percentage of subjects who reached the two mobilization criteria on postoperative days 1 and 2 were 72 and 95% for those with an adductor canal catheter (n = 39), but only 27 and 76% in subjects with a femoral catheter (n = 41; both P < 0.001). Differences in pain scores at rest and intravenous opioid requirements were minimal, but femoral infusion improved dynamic analgesia (P = 0.01 to 0.02). Conclusion:Compared with a continuous femoral nerve block, a continuous adductor canal block did not appreciably decrease the time to overall discharge readiness even though it did decrease the time until adequate mobilization, primarily because both groups experienced similar analgesia and intravenous opioid requirements that—in most cases—exceeded the time to mobilization.

Treatment of postmastectomy pain with ambulatory continuous paravertebral nerve blocks: a randomized, triple-masked, placebo-controlled study.

Background We aimed to determine with this randomized, triple-masked, placebo-controlled study if benefits are afforded by adding a multiple-day, ambulatory, continuous ropivacaine paravertebral nerve block to a single-injection ropivacaine paravertebral block after mastectomy. Methods Preoperatively, 60 subjects undergoing unilateral (n = 24) or bilateral (n = 36) mastectomy received either unilateral or bilateral paravertebral perineural catheter(s), respectively, inserted between the third and fourth thoracic transverse process(es). All subjects received an initial bolus of ropivacaine 0.5% (15 mL) via the catheter(s). Subjects were randomized to receive either perineural ropivacaine 0.4% or normal saline using portable infusion pump(s) [5 mL/h basal; 300 mL reservoir(s)]. Subjects remained hospitalized for at least 1 night and were subsequently discharged home where the catheter(s) were removed on postoperative day (POD) 3. Subjects were contacted by telephone on PODs 1, 4, 8, and 28. The primary end point was average pain (scale, 0–10) queried on POD 1. Results Average pain queried on POD 1 for subjects receiving perineural ropivacaine (n = 30) was a median (interquartile) of 2 (0–3), compared with 4 (1–5) for subjects receiving saline (n = 30; 95% confidence interval difference in medians, −4.0 to −0.3; P = 0.021]. During this same period, subjects receiving ropivacaine experienced a lower severity of breakthrough pain (5 [3–6] vs 7 [5–8]; P = 0.046) as well. As a result, subjects receiving perineural ropivacaine experienced less pain-induced physical and emotional dysfunction, as measured with the Brief Pain Inventory (lower score = less dysfunction): 14 (4–37) versus 57 (8–67) for subjects receiving perineural saline (P = 0.012). For the subscale that measures the degree of interference of pain on 7 domains, such as general activity and relationships, subjects receiving perineural saline reported a median score 10 times higher (more dysfunction) than those receiving ropivacaine (3 [0–24] vs 33 [0–44]; P = 0.035). In contrast, after infusion discontinuation, there were no statistically significant differences detected between treatment groups. Conclusions After mastectomy, adding a multiple-day, ambulatory, continuous ropivacaine infusion to a single-injection ropivacaine paravertebral nerve block results in improved analgesia and less functional deficit during the infusion. However, no benefits were identified after infusion discontinuation.

A randomized, triple-masked, active-controlled investigation of the relative effects of dose, concentration, and infusion rate for continuous popliteal-sciatic nerve blocks in volunteers

BACKGROUND It remains unknown whether local anaesthetic dose is the only factor influencing continuous popliteal-sciatic nerve block effects, or whether concentration, volume, or both exert an influence as well. METHODS Bilateral sciatic catheters were inserted in volunteers (n=24). Catheters were randomly assigned to ropivacaine of either 0.1% (8 ml h(-1)) or 0.4% (2 ml h(-1)) for 6 h. The primary endpoint was the tolerance to transcutaneous electrical stimulation within the tibial nerve distribution at hour 6. Secondary endpoints included current tolerance at other time points and plantar flexion maximum voluntary isometric contraction (22 h total). RESULTS At hour 6, tolerance to cutaneous stimulation for limbs receiving 0.1% ropivacaine was [mean (standard deviation)] 27.0 (20.2) vs26.9 (20.4) mA for limbs receiving 0.4% [estimated mean difference 0.2 mA; 90% confidence interval (CI) -8.2 to 8.5; P=0.02 and 0.03 for lower and upper boundaries, respectively]. Because the 90% CI fell within the prespecified tolerance ±10 mA, we conclude that the effect of the two concentration/volume combinations were equivalent. Similar negative findings were found for the secondary outcomes. CONCLUSIONS For continuous popliteal-sciatic nerve blocks, we found no evidence that local anaesthetic concentration and volume influence block characteristics, suggesting that local anaesthetic dose (mass) is the primary determinant of perineural infusion effects in this anatomic location. These findings suggest that for ambulatory perineural local anaesthetic infusion-for which there is usually a finite local anaesthetic reservoir-decreasing the basal rate while increasing the local anaesthetic concentration may allow for increased infusion duration without compromising postoperative analgesia. CLINICAL TRIAL REGISTRATION NCT01898689.

Single-injection thoracic paravertebral block and postoperative analgesia after mastectomy: A retrospective cohort study

BACKGROUND The treatment of postoperative pain after mastectomy is an area of increasing interest, as this treatment option is now considered a standard of care for those affected by breast cancer. Thoracic paravertebral nerve block (tPVB) using local anesthetics administered before mastectomy can theoretically provide postoperative analgesia, thereby facilitating a more comfortable and shorter hospitalization. METHODS In this retrospective cohort study, we aimed to determine the duration and degree to which tPVB provides postoperative analgesia in patients who underwent either unilateral or bilateral mastectomy (n = 182). We retrospectively examined the numeric rating scale (NRS) for pain scores recorded by nursing staff throughout individual patient hospitalizations, looking specifically at the following time points: arrival from the postanesthesia care unit to the surgical wards, noon on postoperative day 1 (POD1), and discharge. We also examined the number of days until patients were discharged from the hospital. RESULTS Our results revealed a statistically significant decrease in NRS in pain scores for patients who had received a tPVB (n = 92) on arrival from the postanesthesia care unit to the surgical wards (mean NRS decrease of 1.9 points; 99% confidence interval [CI], -3.0 to -0.8; P < .001) but did not show statistically significant decreases in NRS for pain scores for patients at noon on POD1 (mean NRS decrease of 0.3 points at noon on POD1, P = .43) or at discharge (mean NRS decrease of 0.1 point at discharge, P = .65). Moreover, use of tPVB did not have an impact on time until discharge (average decrease of 0.5 hours; 95% CI, -6 to +5 hours, P = .87). CONCLUSIONS Single-injection tPVB appears to provide meaningful postoperative analgesia in the immediate postoperative period after mastectomy but not after the first day of surgery.

Continuous Transversus Abdominis Plane (TAP) Blocks for Postoperative Pain Control after Hernia Surgery: A Randomized, Triple-Masked, Placebo-Controlled Study

BACKGROUND Single-injection transversus abdominis plane (TAP) block provides postoperative analgesia and decreases supplemental analgesic requirements. However, there is currently no evidence from randomized, controlled studies investigating the possible benefits of continuous TAP blocks. Therefore, the aim of this randomized, triple-masked, placebo-controlled study was to determine if benefits are afforded by adding a multiple-day, ambulatory, continuous ropivacaine TAP block to a single-injection block following hernia surgery. METHODS Preoperatively, subjects undergoing unilateral inguinal (N=19) or peri-umbilical (N=1) hernia surgery received unilateral or bilateral TAP perineural catheter(s), respectively. All received a ropivacaine 0.5% (20 mL) bolus via the catheter(s). Subjects were randomized to either postoperative perineural ropivacaine 0.2% or normal saline using portable infusion pump(s). Subjects were discharged home where the catheter(s) were removed the evening of postoperative day (POD) 2. Subjects were contacted on POD 0-3. The primary endpoint was average pain with movement (scale: 0-10) queried on POD 1. RESULTS Twenty subjects of a target 30 were enrolled due to the primary surgeons unanticipated departure from the institution. Average pain queried on POD 1 for subjects receiving ropivacaine (N=10) was a mean (standard deviation) of 3.0 (2.6) vs 2.8 (2.7) for subjects receiving saline (N=10; 95% confidence interval difference in means -2.9 to 3.4; P=0.86). There were no statistically significant differences detected between treatment groups in any secondary endpoint. CONCLUSIONS The results of this study do not support adding an ambulatory, continuous ropivacaine infusion to a single-injection ropivacaine TAP block for hernia surgery. However, the present investigation was underpowered, and further study is warranted.