Pericapsular nerve group block: a 3D CT scan imaging study to determine the spread of injectate.

BACKGROUND: Current understanding of the mechanism of action of the pericapsular nerve group (PENG) block is primarily based on cadaver studies. We performed an imaging study in patients undergoing hip surgery to enhance the understanding of the analgesic mechanisms following a PENG block. MATERIALS AND METHODS: 10 patients scheduled for hip surgery received an ultrasound-guided PENG block with 18 mL of 0.5% ropivacaine mixed with 2 mL of a contrast agent. After completion of the block, a high-resolution CT scan was performed to obtain a three-dimensional reconstruction of the injectate's dispersion. RESULTS: The CT imaging revealed that injectate was mainly confined to the epimysium of the iliacus and the psoas muscle, with a minor spread to the hip capsule. Contrast dye was detected within the iliacus and/or the psoas muscle in all patients. No observed spread to either the subpectineal plane or the obturator foramen was detected. CONCLUSION: Our study suggests that the analgesic effect of the PENG block may be related to the block of the branches of the femoral nerve traveling within the iliopsoas muscle without a spread pattern commensurate with the block of the obturator nerve. TRIAL REGISTRATION NUMBER: ClinicalTrials.gov Registry (NCT06062134).

Anatomic barriers to paraspinal blocks: a cadaver case series

Abstract The paraspinal space is intriguing in nature. There are several needle tip placements described in compact anatomical spaces. This has led to an incertitude regarding the appropriate anatomic locations for needle tip positions. Through our cadaver models we try to resolve the issues surrounding needle tip positions clarifying anatomical spaces and barriers. Further we propose an anatomical classification based on our findings in cadaveric open dissections and cross and sagittal sections.

Ultrasound evaluation of a new surface reference line to describe sural nerve location and safe zones to consider in posterior leg approaches.

PURPOSE: Several authors have described methods to predict the sural nerve pathway with non-proportional numerical distances, but none have proposed a person-proportional, reproducible method with anatomical references. The aim of this research is to describe ultrasonographically the distance and crossing zone between a surface reference line and the position of the sural nerve. METHODS: Descriptive cross-sectional study, performed between January and April 2022 in patients requiring foot surgery who met inclusion criteria. The sural nerve course in the posterior leg was located and marked using ultrasound. Landmarks were drawn with a straight line from the medial femoral condyle to the tip of the fibula. Four equal zones were established in the leg by subdividing the distal half of the line. This way, areas based on simple anatomical proportions for each patient were studied. The distance between the marking and the ultrasound nerve position was measured in these 4 zones, creating intersection points and safety areas. Location and distances from the sural nerve to the proposed landmarks were assessed. RESULTS: One-hundred and four lower limbs, 52 left and 52 right, assessed in 52 patients were included. The shortest median distance of the nerve passage was 2.9 mm from Point 2. The sural nerve intersection was 60/104 (57.7%) in Zone B, 21/104 (20.1%) in Zone C and 19/104 (18.3%) in Zone A. Safety zones were established. Average 80.5% of coincidence in sural nerve localization was found in the distal half of the leg, in relation to the surface reference line when comparing both legs of each patient. CONCLUSIONS: This study proposes a simple, reproducible, non-invasive and, for the first time, person-proportional method, that describes the distance and location of the main areas of intersection of the sural nerve with points and zones (risk and safe zones) determined by a line guided by superficial anatomical landmarks. Its application when surgeons plan and perform posterior leg approaches will help to avoid iatrogenic nerve injuries. LEVEL OF EVIDENCE: IV.

Ultrasound-guided subparaneural popliteal sciatic nerve block: there is more to it than meets the eyes.

The popliteal sciatic nerve block is routinely used for anesthesia and analgesia during foot and ankle surgery. This article reviews our current understanding of the anatomy of the sciatic nerve and discusses how fascial tissue layers associated with the nerve may affect block outcomes . The anatomy of the sciatic nerve is more complex than previously described. The tibial and common peroneal nerves within the sciatic nerve trunk appear to be centrally separated by the Compton-Cruveilhier septum and encompassed by their own paraneural sheaths. This unique internal architecture of the sciatic nerve appears to promote proximal spread of local anesthetic to the internal aspect of the sciatic nerve trunk after a subparaneural injection at or below the divergence of the tibial and common peroneal nerves.

Preoperative bedside ultrasound assessment of gastric volume and evaluation of predisposing factors for delayed gastric emptying: a case-control observational study.

Perioperative pulmonary aspiration of gastric content is a serious complication. Fasting guidelines try to ensure an empty stomach before intervention. Certain medications or pathologies may cause delayed gastric emptying. Bedside ultrasonography is a useful tool when gastric content status is unclear or in emergency situations where fasting is not feasible. The aim of this prospective case-control observational study was to assess differences in gastric fluid volume between fasted patients with or without predisposing factors for delayed gastric emptying. Patients were preoperatively scanned. Antral cross-sectional area was measured by two tracing methods and total gastric clear fluid volumes were calculated. Data was recorded from September 2018 to March 2019 in a university hospital setting in Barcelona, Spain. Fifty-three patients were enrolled, 23 with delayed gastric emptying predisposing factors (DGEF) and 30 without non-DGEF. Ultrasound-estimated gastric clear fluid volume was 35.21 ± 32.69 mL in the DGEF versus 53.50 ± 30.72 mL in the non-DGEF group (p = 0.08). Average volume per unit of weight was 0.61 ± 0.46 mL/kg. Only 1 patient in the DGEF group had a volume that posed a higher risk of aspiration (1.57 mL/kg). Perfect correlation (R = 0.91; p < 0.01) and concordance (0.91; 95% CI 0.83; 0.95) was found between tracing methods. Minimal gastric content was observed in scheduled surgery in spite of predisposing factors for delayed gastric emptying. Ultrasound clear gastric volume estimation was useful to assess preoperative bedside gastric content.

Comparison of the effectiveness of circumferential versus non-circumferential spread in median and ulnar nerve blocks. A double-blind randomized clinical trial.

BACKGROUND AND OBJECTIVES: Circumferential (C) spread of local anesthetic around the nerve is recommended for a successful nerve block. We tested the hypothesis that C spread produces a more complete block than non-circumferential (NC) spread. METHODS: We randomized 124 patients undergoing open carpal tunnel syndrome surgery to receive C or NC spread ultrasound-guided median and ulnar nerve blocks. The primary outcome was the proportion of patients who developed complete sensory block measured at 5, 15 and 30 min. The loss of cold sensation was graded as: 0 (complete block), 1 (incomplete block), or 2 (no block). Secondary outcomes included motor block, nerve swelling and adverse events. RESULTS: In group C, complete sensory block at 5 min was 2.4 (95% CI 1.0 to 5.7; p=0.04) times more frequent in the median nerve and 3.0 (95% CI 1.2 to 7.2; p=0.01) times more frequent in the ulnar nerve compared with group C. However, at 15 and 30 min, it was similar between groups. Complete motor block was more frequent in group C than in group NC for both the median nerve: 1.5 (95% CI 1.1 to 2.2; p<0.01) at 15 min, 1.1 (95% CI 1.0 to 1.2; p=0.02) at 30 min, and the ulnar nerve: 1.7 (95% CI 1.2 to 2.6; p<0.01) at 15 min, 1.2 (95% CI 1.0 to 1.4; p<0.01) at 30 min. The incidence of nerve swelling and adverse effects was similar between groups. CONCLUSIONS: C spread around the median and ulnar nerves at the level of the antecubital fossa generates more complete sensory and motor blocks compared with NC spread. TRIAL REGISTRATION NUMBER: EudraCT 2011-002608-34 and NCT01603680.

Upper trunk block for shoulder analgesia with potential phrenic nerve sparing: a preliminary anatomical report.

BACKGROUND AND OBJECTIVES: Ipsilateral phrenic nerve palsy (PNP) is an undesirable side of conventional approaches to interscalene brachial plexus blocks. The purpose of this study was to demonstrate whether or not the phrenic nerve can be spared by dye when injected at the division of the upper trunk of the brachial plexus. METHODS: Under ultrasound guidance, 5 mL of radiolabeled dye was injected between the anterior and posterior division of the upper trunk in two fresh, cryopreserved cadavers. CT scan analysis, cadaveric dissection, and cryosectioning were performed to examine the spread of the injectate. RESULTS: We found staining of the injectate over the entire upper trunk with its anterior and posterior divisions, the suprascapular nerve under the omohyoid muscle and the lateral pectoralis nerve, and the C5 and C6 roots. The middle trunk was partially stained. There was no evidence of dye staining of the lower trunk, anterior aspect of the anterior scalene muscle, or the phrenic nerve. CONCLUSIONS: Our study offers an anatomical basis for the possibility of providing shoulder analgesia and avoiding a PNP.

Gemelli-obturator complex in the deep gluteal space: an anatomic and dynamic study.

OBJECTIVE: To investigate the behavior of the sciatic nerve during hip rotation at subgluteal space. MATERIALS AND METHODS: Sonographic examination (high-resolution ultrasound machine at 5.0-14 MHZ) of the gemelli-obturator internus complex following two approaches: (1) a study on cadavers and (2) a study on healthy volunteers. The cadavers were examined in pronation, pelvis-fixed position by forcing internal and external rotations of the hip with the knee in 90° flexion. Healthy volunteers were examined during passive internal and external hip rotation (prone position; lumbar and pelvic regions fixed). Subjects with a history of major trauma, surgery or pathologies affecting the examined regions were excluded. RESULTS: The analysis included eight hemipelvis from six fresh cadavers and 31 healthy volunteers. The anatomical study revealed the presence of connective tissue attaching the sciatic nerve to the structures of the gemellus-obturator system at deep subgluteal space. The amplitude of the nerve curvature during rotating position was significantly greater than during resting position. During passive internal rotation, the sciatic nerve of both cadavers and healthy volunteers transformed from a straight structure to a curved structure tethered at two points as the tendon of the obturator internus contracted downwards. Conversely, external hip rotation caused the nerve to relax. CONCLUSION: Anatomically, the sciatic nerve is closely related to the gemelli-obturator internus complex. This relationship results in a reproducible dynamic behavior of the sciatic nerve during passive hip rotation, which may contribute to explain the pathological mechanisms of the obturator internal gemellus syndrome.

Bloqueo supraclavicular ecoguiado por abordaje perivascular medial. Descripción anatómica, técnica de bloqueo y cambios de perfusión regionales / Ultrasound guided supraclavicular perivascular block. Anatomical, technical medial approach description and changes in regional perfusion

Abstract Introduction: Supraclavicular block is usually performed using a lateral to medial approach, although a medial to lateral approach is also feasible. Block onset may be evaluated through the sympathetic effect associated with the sensitive and motor blockade. Objective: To describe the ultrasound-guided supraclavicular block using a medial approach, evaluating the sensitive, motor, and sympathetic block onset. Materials and methods: An ultrasound-guided supraclavicular block was performed in a fresh cadaver with 20 ml volume (2 ml of iodine and 1 ml of methylene blue). A CT scan was performed and sagittal sections were obtained. The clinical phase included 10 patients undergoing a medial approach block; the onset of the block was evaluated based on a motor, sensory and sympathetic assessment (measuring flow changes in the humeral artery, the palmar temperature, and the perfusion index). Results: Adequate distribution of the contrast medium was observed in the cadaver, with complete spread through the brachial plexus, both in terms of the CT-reconstruction as in the anatomical cross sections. A significant change in all the sympathetic block parameters was observed 5 min after the bock: temperature (32.5 ± 1.8 °C to 33.4 ± 1.7 °C; p = 0.047), humeral arterial flow (105 ± 70ml/min to192 ± 97ml/min; p = 0.007), and thumb perfusion index (5 ± 3 to 10 ± 3%; p=0.002). The block was effective and uneventful in all patients. Conclusions: This supraclavicular approach achieves a homogeneous distribution throughout the brachial plexus, with high anesthetic efficacy. Regional changes secondary to the sympathetic block occur early after the block.

Resumen Introducción: El bloqueo supraclavicular habitualmente se realiza mediante abordaje lateral a medial, si bien puede realizarse de medial a lateral y su instauración puede evaluarse por el efecto simpático asociado al bloqueo sensitivo y motor. Objetivo: Describir el bloqueo supraclavicular ecoguiado por abordaje medial evaluando la instauración del bloqueo sensitivo, motor y simpático. Materiales y métodos: Se realizó el bloqueo supraclavicular ecoguiado en cadáver fresco con 20ml de volumen (con 2ml de yodo y 1ml de azul de metileno). Se realizó una tomografía computarizada y posteriormente cortes anatómicos sagitales. En la fase clínica se incluyeron 10 pacientes a quienes se les realizó el bloqueo y posteriormente se evaluó la instauración del bloqueo con valoración sensitiva, motora y simpática (cambios en flujo arterial humeral, temperatura palmar y el índice de perfusión). Resultados: En el cadáver se evidenció una adecuada distribución del medio de contraste bañando la totalidad del plexo braquial, tanto en la reconstrucción tomográfica como en los cortes seccionales anatómicos. Alos 5 min del bloqueo se observó un cambio significativo de todos los parámetros de bloqueo simpático: temperatura (32,5 ± 1,8 a 33,4 ± 1,7 。C; p = 0,047), flujo arterial humeral (105 ± 70 a 192 ± 97ml/min; p = 0,007) e índice de perfusión del pulgar (5 ± 3 a 10 ± 3%; p = 0,002). El bloqueo fue efectivo en todos los pacientes y sin complicaciones. Conclusiones: El abordaje supraclavicular propuesto logra una correcta distribución en el plexo braquial con elevada eficacia anestésica. Los cambios regionales secundarios al bloqueo simpático son precoces tras el bloqueo.

Ultrasound-Guided Costoclavicular Brachial Plexus Block: Sonoanatomy, Technique, and Block Dynamics.

BACKGROUND AND OBJECTIVES: This study aimed to describe in detail the relevant sonoanatomy, technique, and block dynamics of an ultrasound-guided costoclavicular brachial plexus block (BPB). METHODS: Thirty patients scheduled for hand or forearm surgery under a BPB underwent transverse ultrasound imaging of the medial infraclavicular fossa to identify the cords of the brachial plexus at the costoclavicular space (CCS). An ultrasound-guided BPB was then performed at the CCS with 20 mL of 0.5% ropivacaine. Sensory-motor blockade of the ipsilateral median, radial, ulnar, and musculocutaneous nerves were assessed at regular intervals for 30 minutes after the injection. Successful block was defined as being able to complete surgery under the BPB. RESULTS: The CCS was visualized as a well-defined intermuscular space lying deep and posterior to the mid-point of the clavicle. The cords of the brachial plexus were clustered together lateral to the axillary artery within the CCS. The costoclavicular BPB was successfully performed in all patients, and the median onset time for sensory and motor blockade of all the 4 nerves was 5 [5-15] and 5 [5-10] minutes, respectively. Complete sensory blockade of all the 4 nerves was achieved in 30 [20-30] minutes, and the BPB was successful in 29 (97%) of 30 patients. There were no complications directly related to the technique or the local anesthetic injection. CONCLUSIONS: This report describes a novel technique of infraclavicular BPB at the costoclavicular space that produces rapid onset of BPB. Future research should compare the safety and efficacy of this new technique with the traditional lateral sagittal infraclavicular BPB.

Permanent upper trunk plexopathy after interscalene brachial plexus block.

Interscalene brachial plexus block (IBPB) has been widely used in shoulder surgical procedures. The incidence of postoperative neural injury has been estimated to be as high as 3 %. We report a long-term neurologic deficit after a nerve stimulator assisted brachial plexus block. A 55 year-old male, with right shoulder impingement syndrome was scheduled for elective surgery. The patient was given an oral dose of 10 mg of diazepam prior to the nerve stimulator assisted brachial plexus block. The patient immediately complained, as soon as the needle was placed in the interscalene area, of a sharp pain in his right arm and he was sedated further. Twenty-four hours later, the patient complained of severe shoulder and arm pain that required an increased dose of analgesics. Severe peri-scapular atrophy developed over the following days. Electromyography studies revealed an upper trunk plexus injury with severe denervation of the supraspinatus, infraspinatus and deltoid muscles together with a moderate denervation of the biceps brachii muscle. Chest X-rays showed a diaphragmatic palsy which was not present post operatively. Pulmonary function tests were also affected. Phrenic nerve paralysis was still present 18 months after the block as was dysfunction of the brachial plexus resulting in an inability to perform flexion, abduction and external rotation of the right shoulder. Severe brachial plexopathy was probably due to a local anesthetic having been administrated through the perineurium and into the nerve fascicles. Severe brachial plexopathy is an uncommon but catastrophic complication of IBPB. We propose a clinical algorithm using ultrasound guidance during nerve blocks as a safer technique of regional anesthesia.

Ultrasound-guided ankle block for forefoot surgery: the contribution of the saphenous nerve.

BACKGROUND: Ankle blocks typically include the block of 5 nerves, the 4 branches that trace their origin back to the sciatic nerve plus the saphenous nerve (SaN). The sensory area of the SaN in the foot is variable. Based on our clinical experience, we decided to study the sensory distribution of the SaN in the foot and determine whether the block of this nerve is necessary as a component of an ultrasound-guided ankle block for bunion surgery. METHODS: One hundred patients scheduled for bunion surgery under ankle block were prospectively studied. We performed ultrasound-guided individual blocks of the tibial, deep peroneal, superficial peroneal, and sural nerves. After obtaining complete sensory block of these nerves, we mapped the SaN sensory territory as such area without anesthesia on the medial side of the foot. RESULTS: Every nerve block was successful within 10 minutes of injection. The saphenous territory extended into the foot to 57 ± 13 mm distal to the medial malleolus. This distal margin was 22 ± 11 mm proximal to the first tarsometatarsal joint. The proximal end of the surgical incision was located 1 cm distal to the first tarsometatarsal joint. In only 3 patients (3%), the area of SaN innervation reached the proximal end of the planned incision. CONCLUSIONS: Ultrasound-guided ankle block is a highly effective technique for bunion surgery. The sensory territory of the SaN in the foot seems to extend only to the midfoot. According to our sample, 97% of the patients undergoing bunion surgery under an ankle block would not benefit from having a SaN block.

Ultrasound-guided popliteal sciatic block with a single injection at the sciatic division results in faster block onset than the classical nerve stimulator technique.

BACKGROUND: For successful, fast-onset sciatic popliteal block (SPB), either a single injection above the division of the sciatic nerve, or 2 injections to block the tibial nerve (TN) and common peroneal nerve (CPN) separately have been recommended. In this study, we compared the traditional nerve stimulator (NS)-guided SPB above the division of the sciatic nerve with the ultrasound (US)-guided block with single injection of local anesthetic (LA) between the TN and CPN at the level of their division. We hypothesized that US-SPB with a single injection between TN and CPN would result in faster block onset than a single-injection NS-SPB. METHODS: Fifty-two patients were randomized to receive either an NS-SPB or a US-SPB. For both blocks, a single injection of 20 mL mepivacaine 1.5% was given using an automated injection pump while controlling for injection force. For NS-SPB, a TN response below 0.5 mA was sought 7 cm above the popliteal fossa crease (and proximal to the divergence of the TN and peroneal nerves). For US-SPB, the injection was made after a US-guided needle was inserted between the TN and CPN at the level of their separation. Motor response was not actively sought but registered if present. The location and spread of LA were evaluated by US in both groups. Onset of motor and sensory blocks was serially assessed in 5-minute intervals in the TN and CPN divisions and compared between the groups. RESULTS: All patients in both groups had successful block at 30 minutes after the injection, defined as sensory block to allow surgery without supplementation. A higher proportion of patients in the US-SPB group had a complete sensory (80% vs 4%, P < 0.001) and motor block (60% vs 8%, P < 0.001), defined as anesthesia and paralysis in all nerve territories, at 15 minutes after injection. US signs of intraepineural injection were present in 19 patients (73%) in the NS-SPB group and 25 patients (100%) in the US-SPB group (P < 0.001). CONCLUSIONS: A single injection of LA in US-SPB with needle insertion at the separation of the TN and CPN results in a similar success rate at 30 minutes; however, more patients in the US-SPB group than in the NS-SPB group had complete block at 15 minutes.

No clinical or electrophysiologic evidence of nerve injury after intraneural injection during sciatic popliteal block.

BACKGROUND: Intraneural injection during nerve-stimulator-guided sciatic block at the popliteal fossa may be a common occurrence. Although intraneural injections have not resulted in clinically detectable neurologic injury in small studies in human subjects, intraneural injections result in postinjection inflammation in animal models. This study used clinical, imaging, and electrophysiologic measures to evaluate the occurrence of any subclinical neurologic injury in patients with intraneural injection during sciatic popliteal block. METHODS: Twenty patients undergoing popliteal block were enrolled; 17 patients completed the study protocol. After tibial nerve response was achieved by nerve stimulation (0.3-0.5 mA; 2 Hz; 0.1 ms), 20 ml mixture of mepivacaine (1.25%) and radiopaque contrast (2 ml) were injected. Location and spread of the injectant were assessed by ultrasound measurements of the sciatic nerve area before and after injection, and by computed tomography. In addition to clinical neurologic evaluations, serial electrophysiologic studies (nerve conduction and late response studies using predefined criteria) were performed at baseline and at 1 week and 3 weeks after the block for signs of subclinical neurologic dysfunction. RESULTS: Sixteen injections (94%, 95% CI: 71-100%) met criteria for an intraneural injection. Postinjection nerve area on ultrasound increased by 45% (95% CI: 29-58%), P < 0.001. Computed tomography demonstrated fascicular separation in 70% (95% CI: 44-90%), air within the nerve in 29% (95% CI: 10-56%), contrast along bifurcations in 65% (95% CI: 38-86%), and concentric contrast layers in 100% (95% CI: 84-100%). Neither clinical nor electrophysiologic studies detected neurologic dysfunction indicating injury to the nerve. CONCLUSIONS: Nerve-stimulator-guided sciatic block at the popliteal fossa often results in intraneural injection that may not lead to clinical or electrophysiologic nerve injury.

Intraneural injection with low-current stimulation during popliteal sciatic nerve block.

BACKGROUND: Prevention of an intraneural injection of a local anesthetic during peripheral nerve blockade is considered important to avoid neurologic injury. However, the needle-nerve relationship during low-current electrical nerve localization is not well understood. METHODS: We postulated that intraneural needletip location is common during low-current stimulation popliteal sciatic nerve blockade. Twenty-four consecutive ASA class I-III patients scheduled for foot or ankle surgery under popliteal sciatic nerve block using a combined ultrasound and nerve stimulator-guided technique were prospectively studied. The end point for needle advancement was predetermined to be either an elicited motor response between 0.2 and 0.5 mA (100 mus/2 Hz) or an apparent intraneural location of the needletip as seen on ultrasound, whichever came first. The injection occurred at either end points provided the injection pressure was <20 psi. The injection was considered intraneural when injectate resulted in both the swelling and compartmentalization of the nerve within the epineurium. RESULTS: Elicited motor response could be obtained only upon entry of the needle into the intraneural space in 20 patients (83.3%). In the remaining four patients (16.7%), a motor response with a stimulating current of 1.5 mA could not be obtained even after the needle entry into the intraneural space. An injection in the intraneural space occurred in all patients who had motor-evoked response at current 0.2-0.4 mA. All 24 blocks resulted in adequate anesthesia for foot surgery. No patient developed postoperative neurologic dysfunction. CONCLUSION: The absence of motor response to nerve stimulation during popliteal sciatic nerve block does not exclude intraneural needle placement and may lead to additional unnecessary attempts at nerve localization. Additionally, low-current stimulation was associated with a high frequency of intraneural needle placement.