Thomas Fichtner Bendtsen

Primary afferent input critical for maintaining spontaneous pain in peripheral neuropathy.

Summary The role of afferent sensory input in neuropathic pain was examined in 2 groups. Peripheral nerve blocks abolished spontaneous and evoked pain in all patients. Systemic lidocaine was more effective in pain due to polyneuropathy than nerve injury. Central sensitization does not act as an autonomous spontaneous pain‐generating mechanism. Peripheral sensory input is critical in maintaining pain after peripheral nerve damage. ABSTRACT Central sensitization after peripheral nerve injury may result in ectopic neuronal activity in the spinal cord dorsal horn, implying a potential autonomous pain‐generating mechanism. This study used peripheral nerve blockade and systemic lidocaine administration, with detailed somatosensory assessment, to determine the contribution of primary afferent input in maintaining peripheral neuropathic pain. Fourteen patients with neuropathic pain (7 with unilateral foot pain due to peripheral nerve injury and 7 with bilateral pain in the feet due to distal polyneuropathy) underwent comprehensive characterization of somatosensory function by quantitative sensory testing. Patients were then administered an ultrasound‐guided peripheral nerve block with lidocaine and intravenous lidocaine infusion in randomized order. The effect of these interventions on spontaneous pain intensity and on evoked cold, warm, pinprick, and brush responses was assessed at each session. All patients had sensory disturbances at baseline. The peripheral nerve block resulted in a complete abolition of ipsilateral pain within 10 min (median) in all patients, with lidocaine plasma concentrations being too low to account for a systemic effect of the drug. Intravenous lidocaine infusion reduced the spontaneous pain by 45.5% (±31.7%), and it reduced mechanical and thermal hypersensitivity in most patients who displayed such signs. However, the improvement in evoked hypersensitivity was not related to the effect of the drug on spontaneous pain intensity. This study demonstrated that regardless of the individual somatosensory phenotype and signs of central sensitization, primary afferent input is critical for maintaining neuropathic pain in peripheral nerve injury and distal polyneuropathy.

Ultrasound guidance improves a continuous popliteal sciatic nerve block when compared with nerve stimulation.

Background and Objectives: Continuous sciatic nerve blockade at the popliteal level effectively alleviates postoperative pain after major foot and ankle surgery. No randomized controlled trials have previously compared the success rate of continuous sciatic nerve sensory blockade between ultrasound and nerve stimulation guidance. In the current study, we tested the hypothesis that ultrasound-guided catheter placement improves the success rate of continuous sciatic nerve sensory blockade compared with catheter placement with nerve stimulation guidance. Methods: After research ethics committee approval and informed consent, 100 patients scheduled for elective major foot and ankle surgery were randomly allocated to popliteal catheter placement either with ultrasound or nerve stimulation guidance. The primary outcome was the success rate of sensory block the first 48 postoperative hours. Successful sensory blockade was defined as sensory loss in both the tibial and common peroneal nerve territories at 1, 6, 24, and 48 hrs postoperatively. Results: The ultrasound group had significantly higher success rate of sensory block compared with the nerve stimulation group (94% versus 79%, P = 0.03). Ultrasound compared with nerve stimulation guidance also entails reduced morphine consumption (median of 18 mg [range, 0-159 mg] versus 34 mg [range, 0-152 mg], respectively, P = 0.02), fewer needle passes (median of 1 [range, 1-6] versus 2 [range, 1-10], respectively, P = 0.0005), and greater patient satisfaction (median numeric rating scale 9 [range, 5-10] versus 8 [range, 3-10)] respectively, P = 0.0006) during catheter placement. Conclusion: Ultrasound guidance used for sciatic catheter placement improves the success rate of sensory block, number of needle passes, patient satisfaction during catheter placement, and morphine consumption compared with nerve stimulation guidance.

Defining adductor canal block.

used to guide an 18-gauge Tuohy needle into the T12/L1 interspace with minimal bony contact. Loss of resistance to saline was met at a depth of 4.5 cm, and a 20-gauge epidural catheter was threaded easily 4 cm into the epidu space. An 18-gauge 2-inch Crawford needle was used to tunnel the catheter subcutaneously. An anteroposterior and lateral epidurogram was performed with 2 mL of iohexol (Omnipaque 300; GE Healthcare, Cork, Ireland). The catheter position was confirmed at T12 with adequate midline vertical spread in a pattern consistent with posterior and anterior epidural spread (Fig. 1). The patient was returned to the supine position, and the epidural catheter was periodically bolused with 0.25% bupivacaine with 1:200,000 epinephrine intraoperatively to maintain analgesia. The operative procedurewas uneventful. The patient was extubated and later discharged to the ward. Postoperatively, the patient was placed on patient-controlled epidural analgesia with an epidural infusion containing 0.1% ropivacaine, 2 μg/mL fentanyl, and 0.5 μg/mL clonidine. The basal rate was set at 10 mL/h with 2 mL every 30minutes demand. Scheduled oral acetaminophen 650 mg every 6 hours was used as a pain adjunct. On postoperative day (POD) 2, the basal rate was increased to 12 mL/h, and analgesia was reported to be excellent. The epidural catheter was removed on POD 4 after successful transition to oral hydrocodone/ acetaminophen 7.5/500 every 4 hours. She was discharged on POD 4. Both patient and family reported superior analgesia and reduced hospital stay compared with earlier admissions for similar orthopedic operations. Successful placement of an epidural catheter can be a challenging task in children with OPPG given the relative fragility of bony structures and high incidence of preexisting vertebral column abnormalities. However, we suggest that an epidural catheter placed under meticulous fluoroscopic guidance to minimize damage to surrounding tissue may be an appropriate option for children with OPPG undergoing lowerextremity surgery. Indeed, epidural analgesia has been shown to provide postoperative analgesia superior to intravenous patientcontrolled analgesia and may also reduce hospital length of stay. Inadequately managed acute pain may possibly lead to chronic pain states, and this must be taken into consideration when planning anesthetics for patients with chronic painful diseases such as OPPG. Imaging modalities such as ultrasound and fluoroscopy continue to increase the safety of acute painmanagement techniques, and the option of regional anesthesia should be considered in all eligible patients to reduce the costs of inadequately treated perioperative pain.

The Optimal Analgesic Block for Total Knee Arthroplasty.

Abstract Peripheral nerve block for total knee arthroplasty is ideally motor sparing while providing effective postoperative analgesia. To achieve these goals, one must understand surgical dissection techniques, distribution of nociceptive generators, sensory innervation of the knee, and nerve topography in the thigh.

Dynamic needle tip positioning - ultrasound guidance for peripheral vascular access. A randomized, controlled and blinded study in phantoms performed by ultrasound novices.

PURPOSE The application of ultrasound-guidance for peripheral venous access is gaining popularity. It is possible to produce a short axis or a long axis sonographic view of the target vessel and apply an out-of-plane or in-plane needle tip approach. Our aim was to present the dynamic needle tip positioning technique and to estimate which approach is the most accurate for inserting the needle tip into the center of the target vessel. MATERIALS AND METHODS Fiftynine novices in ultrasound-guided peripheral vascular access participated. (A) a short axis view combined with an out-of-plane needle tip approach using dynamic needle tip positioning was compared to (B) a long axis view combined with an in-plane needle tip approach to a target vessel embedded in a gelatine phantom. RESULTS The success rate of method (A) was significantly higher than method (B) (97 % versus 81 %). The distance between the center of the target vessel and the final needle tip position was significantly shorter for method (A) compared to method (B). CONCLUSION The combined short axis and out-of-plane technique using dynamic needle tip positioning had a higher success rate and a shorter distance between the center of the target vessel and the needle tip compared to the combined long axis and in-plane technique.

Redefining the adductor canal block.

FIGURE 1. The photographs show a cadaver limb from a man (A) and a woman (B). The distance from the base of patella (red) to the anterior superior iliac spine (blue) is 50 cm in the male limb and 44 cm in the female limb. The midpoint (cyan) is 25 cm proximal to the base of the patella in the male and 22 cm in the female limb. The midpoint is approximately 9 cm from the upper margin (magenta) of the AC in themale and 7.5 cm in the female limb. The distance from the lower border of the greater trochanter (green) to the base of patella (red) is 32 cm in the male and 29 cm in the female limb, and the midpoint (yellow) is at the level of the AC. We want to thank Jæger and colleagues for responding to our concerns about the so-called adductor canal block (ACB). However, some important issues require further clarification. Jæger et al state that the anatomical basis of the ACB has academic interest but limited clinical relevance. Because we agree with Alon Winnie that “regional anesthesia is simply an excercise of applied anatomy,”we believe that it is highly relevant to discuss and understand the anatomical basis of ACB. The needle insertion point for the ACB as defined by Jæger et al—and in past publications by the same research group—is the midpoint between the anterior superior iliac spine and the base of the patella. Jæger et al insist that this point is per definition within the adductor canal

The Shamrock lumbar plexus block: A dose-finding study

BACKGROUND The Shamrock technique is a new method for ultrasound-guided lumbar plexus blockade. Data on the optimal local anaesthetic dose are not available. OBJECTIVE The objective of this study is to estimate the effective dose of ropivacaine 0.5% for a Shamrock lumbar plexus block. DESIGN A prospective dose-finding study using Dixons up-and-down sequential method. SETTING University Hospital Orthopaedic Anaesthesia Unit. INTERVENTION Shamrock lumbar plexus block performance and block assessment were scheduled preoperatively. Ropivacaine 0.5% was titrated with the Dixon and Massey up-and-down method using a stepwise change of 5 ml in each consecutive patient. Combined blocks of the femoral, the lateral femoral cutaneous and the obturator nerve were prerequisite for a successful lumbar plexus block. PATIENTS Thirty patients scheduled for lower limb orthopaedic surgery completed the study. MAIN OUTCOME MEASURES The minimum effective anaesthetic volume of ropivacaine 0.5% (ED50) to achieve a successful Shamrock lumbar plexus block in 50% of the patients. Further analysis of the data was performed with a logistic regression model to calculate ED95 and to estimate the effective doses for a sensory lumbar plexus block not requiring a motor block of the femoral nerve. RESULTS The Dixon and Massay estimate of the ED50 was 20.4 [95% confidence interval (95% CI) 13.9 to 30.0] ml ropivacaine 0.5%. The logistic regression estimate of the ED95 was 36.0 (95% CI 19.7 to 52.2) ml ropivacaine 0.5%. For a sensory lumbar plexus block, the ED50 was 17.1 (95% CI 12.3 to 21.9) ml and the ED95 was 25.8 (95% CI 18.6 to 33.1) ml. CONCLUSION A volume of 20.4 ml ropivacaine 0.5% provided a successful Shamrock lumbar plexus block in 50% of the patients. A volume of 36.0 ml would be successful in 95% of the patients. TRIAL REGISTRATION ClinicalTrials.gov identifier NCT01956617.

The Analgesic Effect of Obturator Nerve Block Added to a Femoral Triangle Block After Total Knee Arthroplasty: A Randomized Controlled Trial.

Background and Objectives Total knee arthroplasty (TKA) is associated with severe pain, and effective analgesia is essential for the quality of postoperative care and ambulation. The analgesic effects of adding an obturator nerve block (ONB) to a femoral triangle block (FTB) after TKA have not been tested previously. We hypothesized that combined ONB and FTB will reduce opioid consumption and pain compared with those of a single FTB or local infiltration analgesia (LIA). Methods Seventy-eight patients were randomized to combined ONB and FTB, single FTB, or LIA after primary unilateral TKA. The primary outcome was morphine consumption during the first 24 postoperative hours. Secondary outcomes included morphine consumption during the first 48 postoperative hours, pain at rest and passive knee flexion, nausea and vomiting, cumulated ambulation score, and Timed Up and Go test. Results Seventy-five patients were included in the analysis. The total intravenous morphine consumption during the first 24 postoperative hours was 2 mg (interquartile range [IQR], 0–15) in the combined ONB and FTB group, 20 mg (IQR, 10–26) in the FTB group (P = 0.0007), and 17 mg (IQR, 10–36) in the LIA group (P = 0.002). The combined ONB and FTB group displayed reduced pain, nausea, and vomiting compared with the other groups. The ambulation tests showed no statistically significant differences between the groups. Conclusions Addition of ONB to FTB significantly reduced opioid consumption and pain after TKA compared with a single FTB or LIA, without impaired ambulation.

Basic Topography of the Saphenous Nerve in the Femoral Triangle and the Adductor Canal.

remarks develop into a binding regulatory interpretation. To illustrate, anesthesiologists who perform nerve blocks with ultrasound guidance routinely have both hands occupied: one hand holds the needle and the other hand holds the ultrasound probe. During the procedure, the anesthesiologist needs a “third hand” to depress the plunger of the syringe containing the injectate once the needle is in an appropriate position. Often, a registered nurse (RN) serves as this “third hand”; in such scenarios, the medication could not reach the targeted nerves without the RN’s assistance. Even still, Eddinger’s proposition that the RN who depresses the plunger of the syringe is, in fact, the practitioner who “administers” anesthesia belittles the other more sophisticated efforts inherent in a nerve block procedure. It seems that Eddinger has reduced the “administration” of anesthesia to 1 single task, thereby neglecting the myriad of steps required to perform RA safely and effectively. More specifically, the anesthesiologist uses a substantial degree of medical judgment when determining patient and procedure appropriateness. For instance, such determinations involve assessing the consequences of comorbidities, conducting intraprocedure interpretation of ultrasound images, weighing the postoperative/ postprocedure anatomic and physiologic consequences of nerve block performance, andmeasuring the relative risk of performing the block procedure relative to the intended benefits. Of course, this list of considerations is not exhaustive; rather, it serves to illustrate why a complex process should not be defined merely by one of its components. Eddinger’s remarks were recently critiqued from a legal perspective. Whereas emergency department RAmay differ from that of an anesthesiology department, Eddinger’s remarks may have a similar ripple effect onmedicolegal proceedings, malpractice exposure, scope of practice and licensure concerns, and reimbursement in other provider settings. Although Eddinger’s remarks do not currently carry the force of law, it is possible that his remarks could gain binding fruition in the future. Policy makers should solicit additional insight and professional input when clarifying ambiguous regulatory requirements considering the practical consequences of these regulatory requirements.

A randomised controlled trial of bilateral dual transversus abdominis plane blockade for laparoscopic appendicectomy

We investigated the effects of pre‐operative ultrasound‐guided bilateral dual transversus abdominis plane blocks on pain when sitting up and pain at rest after laparoscopic appendicectomy. We allocated 28 participants to injection with 60 ml ropivacaine 0.375% and 28 participants to 60 ml isotonic saline. The median (IQR [range]) cumulative pain scores during the first 12 postoperative hours were less after ropivacaine than saline (maximum 120): on sitting, 34 (19‐46 [0‐59]) vs 50 (30‐59 [0‐97]), respectively, p = 0.009; and at rest, 25 (10‐33 [0‐49]) vs 31 (24‐43 [0‐72]), respectively, p = 0.035. There were no differences in morphine consumption, nausea, vomiting, time in recovery or time to walk.