The Hypoechoic Triangle: A New Sonographic Landmark for Rectus Sheath Block.

Rectus sheath blocks can provide analgesia for upper abdominal midline incisions. These blocks can be placed on patients who are anticoagulated, supine, and under general anesthesia. However, block success rates remain low, presumably because of the difficulty of placing local anesthetic between the correct fascial layers. Here we characterize a hypoechoic triangle with sonography, an anatomic space between adjacent rectus abdominis segments that can be accessed for easier needle tip and catheter placement. This approach could reduce reliance on hydrodissection to correctly identify the potential space and instead improve block efficacy by offering providers a discrete target for local anesthesia.

Post-surgical inflammatory neuropathy after anterior cruciate ligament repair: a case report.

BACKGROUND: Unanticipated symptoms of peripheral nerve damage following surgery are distressing to both the patient and their clinical team, including surgeons, anesthesiologists, and neurologists. The causes that are commonly considered for perioperative neuropathy can include surgical trauma, positioning-related injury, or injury related to a regional anesthetic technique. However, these cases often do not have a clear etiology and can occur without any apparent periprocedural anomalies. Postoperative inflammatory neuropathy is a more recently described, and potentially underrecognized cause of perioperative neuropathy which may improve with corticosteroid therapy. Therefore, it is an important etiology to consider early in the evaluation of perioperative neuropathy. CASE PRESENTATION: An otherwise healthy patient presented for left anterior cruciate ligament reconstruction. He underwent femoral and sciatic ultrasound-guided single-injection peripheral nerve blocks preoperatively, followed by a general anesthetic for the surgical procedure. He developed postoperative neuropathy in the sciatic distribution with both sensory and motor deficits. The patient received multi-disciplinary consultations, including neurology and pain management, and a broad differential diagnosis was considered. Based on neurological evaluation and imaging studies, a final diagnosis of post-surgical inflammatory neuropathy was made. The patient's course improved with conservative management, but immunosuppressive treatment may have been considered for a more severe or worsening clinical course. CONCLUSIONS: There are limited publications describing postoperative inflammatory neuropathy, and this case serves to illustrate a potentially under-recognized and multifactorial cause of postoperative neuropathy. Perioperative neuropathies are a complication that surgeons and anesthesiologists strive to avoid; however, prevention and treatment of this condition have been elusive. Increased reporting and investigation of postoperative inflammatory neuropathy as one cause for this complication will help to further our understanding of this potentially devastating complication.

Overcoming Obstacles: The Legacy of Fidel Pagés, Founder of the Epidural, 100 Years After His Passing.

Fidel Pagés, a Spanish surgeon, tragically died in 1923 at the age of 37, just 2 years after his publication "Anestesia Metamérica," the first description of human thoracolumbar epidural anesthesia. In the intervening 100 years, epidural anesthesia has faced countless obstacles, starting with the dissemination of his initial report, which was not widely read nor appreciated at the time. However, the merits of the technique have fueled innovations to meet these challenges over the years. Even today, while epidural anesthesia is widely embraced, particularly in obstetric and chronic pain medicine, the pressures of the operating room for efficiency and a low tolerance for failure, pose modern-day challenges. Here, we revisit Pagés' original report and highlight the key innovations that have allowed for the evolution of this essential anesthesia technique.

Baclofen Pump Replacement in a Patient With End-Stage Amyotrophic Lateral Sclerosis: A Case Report Demonstrating Transversus Abdominis Plane Block as the Sole Anesthetic.

A patient with end-stage amyotrophic lateral sclerosis (ALS) presented for Baclofen pump replacement. She underwent a left transversus abdominis plane block to anesthetize the left lower quadrant of the abdomen. No sedatives or analgesics were administered, and the procedure was successfully completed without complication. It is prudent to consider anesthetic plans that avoid complications associated with general or neuraxial anesthesia in patients with ALS. This case report demonstrates successful placement of a transversus abdominis plane block in a patient with ALS and offers a safe anesthetic technique that can be performed in other high-risk patients.

Ultrasound Detection of Arteria Comitans: A Novel Technique to Locate the Sciatic Nerve.

In the gluteal and thigh region, the arteria comitans accompanies the sciatic nerve for a short distance, then penetrates the nerve and runs to the lower part of the thigh. There is no study that recognizes this artery as a guide to the location of the sciatic nerve. In this report, we describe a series of 6 knee arthroplasty patients in whom ultrasound-guided sciatic nerve block was successfully performed using color Doppler and pulsed wave Doppler to visualize the arteria comitans as a guide to the location of the sciatic nerve. We have found that detecting the arteria comitans as a landmark is novel and may offer an additional tool with the existing methods for sciatic nerve block.

Structural characterisation of polycrystalline colloidal monolayers in the presence of aspherical impurities.

Impurities in crystalline materials introduce disorder into an otherwise ordered structure due to the formation of lattice defects and grain boundaries. The properties of the resulting polycrystal can differ remarkably from those of the ideal single crystal. Here we investigate a quasi-two-dimensional system of colloidal spheres containing a small fraction of aspherical impurities and characterise the resulting polycrystalline monolayer. We find that, in the vicinity of an impurity, the underlying hexagonal lattice is deformed due to a preference for five-fold co-ordinated particles adjacent to impurities. This results in a reduction in local hexagonal ordering around an impurity. Increasing the concentration of impurities leads to an increase in the number of these defects and consequently a reduction in system-wide hexagonal ordering and a corresponding increase in entropy as measured from the distribution of Voronoi cell areas. Furthermore, through both considering orientational correlations and directly identifying crystalline domains we observe a decrease in the average polycrystalline grain size on increasing the concentration of impurities. Our data show that, for the concentrations considered, local structural modifications due to the presence of impurities are independent of their concentration, while structure on longer lengthscales (i.e. the size of polycrystalline grains) is determined by the impurity concentration.

The pattern of tibial nerve excursion with active ankle dorsiflexion is different in older people with diabetes mellitus.

BACKGROUND: The peripheral nervous system has an inherent capability to tolerate the gliding (excursion), stretching (increased strain), and compression associated with limb motions necessary for functional activities. The biomechanical properties during joint movements are well studied but the influence of other factors such as limb pre-positioning, age and the effects of diabetes mellitus are not well established for the lower extremity. The purposes of this pilot study were to compare the impact of two different hip positions on lower extremity nerve biomechanics during an active ankle dorsiflexion motion in healthy individuals and to determine whether nerve biomechanics are altered in older individuals with diabetes mellitus. METHODS: Ultrasound imaging was used to quantify longitudinal motion of the tibial nerve and transverse plane motion of the tibial and common fibular nerves in the popliteal fossa during active ankle movements. FINDINGS: In healthy individuals, ankle dorsiflexion created mean tibial nerve movement of 2.18 mm distally, 1.36 mm medially and 3.98 mm superficially. When the hip was in a flexed position there was a mean three-fold reduction in distal movement. In people with diabetes mellitus there was significantly less distal movement of the tibial nerve in the neutral hip position and less superficial movement of the nerve in both hip positions compared to healthy individuals. INTERPRETATION: We have documented reductions in tibial nerve excursion due to limb pre-positioning thought to pre-load the nervous system using a non-invasive methodology. Thus, lower limb pre-positioning impacts nerve biomechanics during ankle motions common in functional activities. Additionally, our findings indicate that nerve biomechanics have the potential to be altered in older individuals with diabetes mellitus compared to younger healthy individuals.

Mechanosensitivity during lower extremity neurodynamic testing is diminished in individuals with Type 2 Diabetes Mellitus and peripheral neuropathy: a cross sectional study.

BACKGROUND: Type 2 Diabetes Mellitus (T2DM) and diabetic symmetrical polyneuropathy (DSP) impact multiple modalities of sensation including light touch, temperature, position sense and vibration perception. No study to date has examined the mechanosensitivity of peripheral nerves during limb movement in this population. The objective was to determine the unique effects T2DM and DSP have on nerve mechanosensitivity in the lower extremity. METHODS: This cross-sectional study included 43 people with T2DM. Straight leg raise neurodynamic tests were performed with ankle plantar flexion (PF/SLR) and dorsiflexion (DF/SLR). Hip flexion range of motion (ROM), lower extremity muscle activity and symptom profile, intensity and location were measured at rest, first onset of symptoms (P1) and maximally tolerated symptoms (P2). RESULTS: The addition of ankle dorsiflexion during SLR testing reduced the hip flexion ROM by 4.3° ± 6.5° at P1 and by 5.4° ± 4.9° at P2. Individuals in the T2DM group with signs of severe DSP (n = 9) had no difference in hip flexion ROM between PF/SLR and DF/SLR at P1 (1.4° ± 4.2°; paired t-test p = 0.34) or P2 (0.9° ± 2.5°; paired t-test p = 0.31). Movement induced muscle activity was absent during SLR with the exception of the tibialis anterior during DF/SLR testing. Increases in symptom intensity during SLR testing were similar for both PF/SLR and DF/SLR. The addition of ankle dorsiflexion induced more frequent posterior leg symptoms when taken to P2. CONCLUSIONS: Consistent with previous recommendations in the literature, P1 is an appropriate test end point for SLR neurodynamic testing in people with T2DM. However, our findings suggest that people with T2DM and severe DSP have limited responses to SLR neurodynamic testing, and thus may be at risk for harm from nerve overstretch and the information gathered will be of limited clinical value.

Functional deficits after intraneural injection during interscalene block.

OBJECTIVE: We present an occurrence of a severe but transient neurologic complication after intraneural injection during an ultrasound-guided interscalene block. CASE REPORT: A 36-year-old man underwent ultrasound-guided interscalene nerve blockade before shoulder incision and drainage. On postoperative day 1, he exhibited new-onset arm weakness with dysesthesias. Intraneural injection was recognized based on a retrospective review of the recorded ultrasound imaging. The symptoms persisted for more than 2 weeks and completely resolved by 6 weeks. CONCLUSIONS: Our report suggests that intraneural injection during ultrasound-guided interscalene block carries a risk of neurologic complications.

Mechanosensitivity of the lower extremity nervous system during straight-leg raise neurodynamic testing in healthy individuals.

STUDY DESIGN: Cross-sectional, observational study. OBJECTIVES: To explore how ankle position affects lower extremity neurodynamic testing. BACKGROUND: Upper extremity limb movements that increase neural loading create a protective muscle action of the upper trapezius, resulting in shoulder girdle elevation during neurodynamic testing. A similar mechanism has been suggested in the lower extremities. METHODS: Twenty healthy subjects without low back pain participated in this study. Hip flexion angle and surface electromyographic measures were taken and compared at the onset of symptoms (P1) and at the point of maximally tolerated symptoms (P2) during straight-leg raise tests performed with ankle dorsiflexion (DF-SLR) and plantar flexion (PF-SLR). RESULTS: Hip flexion was reduced during DF-SLR by a mean +/- SD of 5.5 degrees +/- 6.6 degrees at P1 (P = .001) and 10.1 degrees +/- 9.7 degrees at P2 (P<.001), compared to PF-SLR. DF-SLR induced distal muscle activation and broader proximal muscle contractions at P1 compared to PF-SLR. CONCLUSION: These findings support the hypothesis that addition of ankle dorsiflexion during straight-leg raise testing induces earlier distal muscle activation and reduces hip flexion motion. The straight-leg test, performed to the onset of symptoms (P1) and with sensitizing maneuvers, allows for identification of meaningful differences in test outcomes and is an appropriate end point for lower extremity neurodynamic testing.

An ultrasound study of the phrenic nerve in the posterior cervical triangle: implications for the interscalene brachial plexus block.

BACKGROUND AND OBJECTIVES: Concomitant phrenic nerve block frequently occurs after brachial plexus block procedures in the neck and can result in substantial morbidity. In this study we sought to establish the anatomic basis using ultrasound imaging. METHODS: We scanned the neck region of 23 volunteers with high resolution ultrasonography and identified the phrenic nerve in 93.5% of scans. RESULTS: The phrenic nerve was monofascicular with a mean diameter of 0.76 mm. The phrenic nerve position was nearly indistinguishable from the C5 ventral ramus at the level of the cricoid cartilage (mean distance 1.8 mm). Separation between the phrenic nerve and the brachial plexus increased substantially at more caudal levels in the neck. Phrenic nerve identification was confirmed by percutaneous injection of methylene blue followed by open dissection in a cadaver. Furthermore its identity was confirmed by ultrasound-guided transcutaneous nerve stimulation. CONCLUSIONS: This descriptive study found that the phrenic nerve and brachial plexus are within 2 mm of each other at the cricoid cartilage level, with additional 3 mm separation for every cm more caudal in the neck. Clinical trials with imaging guidance are needed to establish whether brachial plexus selective blocks can be consistently achieved above the clavicle.

Sonographic imaging of the obturator nerve for regional block.

BACKGROUND AND OBJECTIVES: Today, there is a growing appreciation of the importance of the obturator nerve in clinical anesthesia. The aim of this study is to describe the ultrasound appearance of the obturator nerve for potential utility in guiding these nerve blocks. METHODS: We scanned left and right inguinal regions of 20 volunteers lateral and distal to the pubic tubercle (PT) and assessed visibility, size and shape, and depth from the skin of common obturator nerves and their associated divisions. In addition to the volunteer study, we retrospectively reviewed a clinical series of obturator nerve blocks performed with ultrasound guidance and nerve stimulation. RESULTS: The obturator nerve can be sonographically visualized by scanning along the known course of the nerve; the anterior division characteristically converges toward the posterior division along the lateral border of the adductor brevis muscle to form the common obturator nerve more proximally. In the set of 20 volunteers, 25% (10/40) of common, 85% (34/40) of anterior, and 87.5% (35/40) of posterior obturator nerves were sonographically identified. The common obturator nerve was visualized 1.3 +/- 1.5 cm distal and 2.3 +/- 1.2 cm lateral to the PT. Divisions were visualized 2.1 +/- 2.0 cm distal and 2.1 +/- 1.2 cm lateral to the PT. The nerves (common, anterior, and posterior) averaged 2.7 +/- 1.2 mm, 1.4 +/- 0.6 mm, and 1.7 +/- 0.6 mm in anterior-posterior dimension and 9.0 +/- 4.3 mm, 9.6 +/- 3.9 mm, and 10.9 +/- 4.1 mm in medial-lateral dimension and were 25.9 +/- 7.6 mm, 15.5 +/- 3.9 mm, and 29.3 +/- 7.9 mm below the skin surface. The common obturator nerve and its anterior and posterior divisions are all relatively flat nerves with average anterior-posterior/medial-lateral dimension ratios of 0.32, 0.18, and 0.18, respectively. In the clinical series, nerve identification was confirmed with nerve stimulation (n = 6 block procedures, mean threshold stimulating current for evoked adductor contraction = 0.70 +/- 0.14 mA). CONCLUSIONS: The obturator nerve and its divisions are the flattest peripheral nerves yet described with ultrasound imaging. Knowledge of the obturator nerve's ultrasound appearance facilitates localization of this nerve for regional block and may increase success of such procedures.