Ahtsham U. Niazi

The Sensitivity of Motor Response to Nerve Stimulation and Paresthesia for Nerve Localization As Evaluated by Ultrasound

Background and Objective: Seeking paresthesia and obtaining a motor response to an electrical stimulus are the two most common methods of nerve localization for the performance of peripheral-nerve blocks. However, these two endpoints do not always correlate, and the actual sensitivity and specificity of either method remains unknown. The objective of this study is to determine the sensitivity of paresthesia and motor response to electrical nerve stimulation as tools for nerve localization when a 22-gauge insulated needle is used for the performance of axillary-nerve block. Methods: After IRB approval and informed consent, 103 patients were enrolled. Real-time ultrasonography was used as the reference test. After needle-to-nerve contact was confirmed by ultrasonography, the patient was requested to report the presence of paresthesia, and a nerve stimulator was used to seek a motor response, with a stimulating current of 0.5 mA or less. Results: One patient was excluded from analysis because of protocol violation. Paresthesia was found to be 38.2% sensitive and motor response was 74.5% sensitive for detection of needle-to-nerve contact. Conclusion: The very different and relatively low sensitivity of either technique may explain, in part, the lack of correlation previously reported between the 2 endpoints.

Ultrasound-guided regional anesthesia performance in the early learning period: effect of simulation training.

Background and Objectives Success in performing ultrasound-guided peripheral nerve blockade (PNB) demands sound knowledge of sonoanatomy, good scanning techniques, and proper hand-eye coordination. The objectives of our study were to evaluate whether simulator training aids success of novice operators in ultrasound-guided PNB and to determine what number of procedures is required to attain proficiency. Methods Twenty Postgraduate Year 2 anesthesiology residents with no previous experience in ultrasound-guided PNB were randomly assigned into 2 groups. Both groups received conventional teaching comprising of 4 didactic lectures on PNBs with ultrasound guidance. Using a low-fidelity simulation model, 1 group further received an hourlong training session on needling and proper hand-eye coordination. Once the training was over, the residents started their rotation through our block room. Using a logbook, each resident recorded the number of successful and failed ultrasound-guided regional anesthesia blocks performed over a 3-week period. A successful block was defined as one that was effective for surgical anesthesia and performed within 15 mins, with only verbal guidance from a staff anesthesiologist. Cumulative summation charts were created to track progress using a predetermined acceptable failure rate of 30%. Results The conventional training group had 98 successful blocks, and the simulation group had 144 (51.3% vs 64%; P = 0.016). In the conventional training group, 4 of 10 residents achieved proficiency, and in the simulation training group, 8 of 10 residents achieved proficiency (80% vs 40%; P = 0.0849). Conclusions Simulation training improves success rate in ultrasound-guided performance of regional anesthesia.

The Nerves of the Adductor Canal and the Innervation of the Knee: An Anatomic Study.

Background and Objectives Adductor canal block contributes to analgesia after total knee arthroplasty. However, controversy exists regarding the target nerves and the ideal site of local anesthetic administration. The aim of this cadaveric study was to identify the trajectory of all nerves that course in the adductor canal from their origin to their termination and describe their relative contributions to the innervation of the knee joint. Methods After research ethics board approval, 20 cadaveric lower limbs were examined using standard dissection technique. Branches of both the femoral and obturator nerves were explored along the adductor canal and all branches followed to their termination. Results Both the saphenous nerve (SN) and the nerve to vastus medialis (NVM) were consistently identified, whereas branches of the anterior obturator nerve were inconsistently present. The NVM contributed significantly to the innervation of the knee capsule, through intramuscular, extramuscular, and deep genicular nerves. The SN had a relatively more modest contribution through superficial infrapatellar and posterior branches as well as contributing to the origin of the deep genicular nerves. Conclusions The results suggest that both the SN and NVM contribute to the innervation of the anteromedial knee joint and are therefore important targets of adductor canal block. Given the site of exit of both nerves in the distal third of the adductor canal, the midportion of the adductor canal is suggested as an optimal site of local anesthetic administration to block both target nerves while minimizing the possibility of proximal spread to the femoral triangle.

IV and Perineural Dexmedetomidine Similarly Prolong the Duration of Analgesia after Interscalene Brachial Plexus Block: A Randomized, Three-arm, Triple-masked, Placebo-controlled Trial.

Background:Perineural and IV dexmedetomidine have each been suggested to prolong the duration of analgesia when administered in conjunction with peripheral nerve blocks. In the first randomized, triple-masked, placebo-controlled trial to date, the authors aimed to define and compare the efficacy of perineural and IV dexmedetomidine in prolonging the analgesic duration of single-injection interscalene brachial plexus block (ISB) for outpatient shoulder surgery. Methods:Ninety-nine patients were randomized to receive ISB using 15 ml ropivacaine, 0.5%, with 0.5 &mgr;g/kg dexmedetomidine administered perineurally (DexP group), intravenously (DexIV group), or none (control group). The authors sequentially tested the joint hypothesis that dexmedetomidine prolongs the duration of analgesia and reduces the 24-h cumulative postoperative morphine consumption. Motor blockade, pain severity, hemodynamic variations, opioid-related side effects, postoperative neurologic symptoms, and patient satisfaction were also evaluated. Results:Ninety-nine patients were analyzed. The duration of analgesia was 10.9 h (10.0 to 11.8 h) and 9.8 h (9.0 to 10.6 h) for the DexP and DexIV groups, respectively, compared with 6.7 h (5.6 to 7.8) for the control group (P < 0.001). Dexmedetomidine also reduced the 24-h cumulative morphine consumption to 63.9 mg (58.8 to 69.0 mg) and 66.2 mg (60.6 to 71.8 mg) for the DexP and DexIV groups, respectively, compared with 81.9 mg (75.0 to 88.9 mg) for the control group (P < 0.001). DexIV was noninferior to DexP for these outcomes. Both dexmedetomidine routes reduced the pain and opioid consumption up to 8 h postoperatively and did not prolong the duration of motor blockade. Conclusion:Both perineural and IV dexmedetomidine can effectively prolong the ISB analgesic duration and reduce the opioid consumption without prolonging motor blockade.

Real‐time ultrasound‐guided spinal anesthesia using the SonixGPS ultrasound guidance system: a feasibility study

Real‐time ultrasound‐guided neuraxial blockade remains a largely experimental technique. SonixGPS® is a new needle tracking system that displays needle tip position on the ultrasound screen. We investigated if this novel technology might aid performance of real‐time ultrasound‐guided spinal anesthesia.

Methods to ease placement of stimulating catheters during in-plane ultrasound-guided femoral nerve block.

Many clinicians use a subcutaneous tunnel (with or without a skin bridge) to anchor catheters used in peripheral nerve blocks. Different techniques exist for the subcutaneous tunneling of peripheral nerve catheters for short-term use in postoperative pain control. Among the possible hazards of tunneling are needlesticks to the clinician and also shearing of the catheter by the needle as it approaches the catheter. One way to decrease the previously mentioned hazards is by the use of the block needle’s sheath. The sheaths are open-ended, and many are transparent. Placing an open end of the sheath at the spot where the distal end of the needle will exit the tunnel gives the user a hard point to exert pressure against, while shielding the catheter from the needle tip (Fig. 1). This also gives the user Blonger fingers,[ placing them out of the immediate area of the needle tip. This results in no to minimal skin trauma while using something that is already in the kit. There is less need to collect a sharp instrument to nick the skin at the end of the tunnel. It is hoped that needlesticks and catheter shearing are decreased when this method is used.

Point-of-care ultrasound defines gastric content and changes the anesthetic management of elective surgical patients who have not followed fasting instructions: a prospective case series

PurposePulmonary aspiration of gastric contents is a major cause of anesthesia morbidity and mortality. Point-of-care gastric ultrasound provides information regarding the type and volume of gastric content. The hypothesis of this prospective cohort study was that the addition of point-of-care gastric ultrasound to standard patient assessment results in changes in anesthetic management in at least 30% of elective surgical patients who do not follow fasting instructions.MethodsFollowing Research Ethics Board approval and informed consent, elective surgical patients who did not follow fasting instructions were included in this prospective study. Documentation included the type of food ingested, the timing of the ingestion relative to the planned surgical time, and the treating anesthesiologist’s management plan based on history alone. Next, an independent anesthesiologist not involved in the medical decision-making performed a focused gastric ultrasound examination. The results of the ultrasound exam were documented in a standardized fashion and made available to the attending anesthesiologist who then confirmed or revised the initial management plan. The treating anesthesiologist’s actual (post-test) patient management was documented in a standardized fashion and compared with the initial (pre-test) management plan.ResultsThirty-eight patients were included in this case series. Following point-of-care gastric ultrasound, there was a change in either the timing of anesthesia or the anesthetic technique (or both) in 27 patients (71%), with a net change towards a lower incidence of surgical delays.ConclusionsThis prospective case series suggests that a standardized point-of care gastric ultrasound examination informs anesthesiologists’ perceived level of aspiration risk and leads to changes in anesthetic management in a significant proportion of elective patients who did not follow fasting instructions.RésuméObjectifL’inhalation pulmonaire du contenu gastrique est une cause majeure de morbidité et de mortalité liées à l’anesthésie. L’échographie gastrique au chevet offre des informations concernant le type et le volume du contenu gastrique. L’hypothèse de cette étude de cohorte prospective était de montrer qu’en ajoutant une échographie gastrique au chevet à l’évaluation normale des patients, on modifiait la prise en charge anesthésique d’au moins 30 % des patients de chirurgie non urgente n’ayant pas respecté les consignes de jeûne.MéthodeAprès avoir obtenu l’approbation du Comité d’éthique de la recherche et le consentement écrit des patients, des patients devant subir une chirurgie non urgente qui n’avaient pas suivi les consignes de jeûne ont été inclus dans cette étude prospective. Les renseignements colligés comprenaient le type de nourriture ingéré, le moment d’ingestion par rapport à l’heure prévue de la chirurgie, et le plan de prise en charge de l’anesthésiologiste traitant élaboré en fonction du dossier médical seul. Ensuite, un anesthésiologiste indépendant qui n’était pas impliqué dans la prise de décision médicale a réalisé un examen d’échographie gastrique ciblé. Les résultats de l’examen échographique ont été documentés de façon standardisée et mis à disposition de l’anesthésiologiste en charge, qui a par la suite confirmé ou révisé son plan de prise en charge initial. La prise en charge définitive de l’anesthésiologiste traitant (après le test) a été documentée de façon standardisée et comparée au plan de prise en charge initial (avant le test).RésultatsTrente-huit patients ont été inclus dans cette série de cas. Après l’échographie gastrique au chevet, on a observé des changements dans le moment de l’anesthésie ou dans la technique anesthésique (ou les deux) chez 27 patients (71 %), avec un changement net vers une incidence plus faible de délais chirurgicaux.ConclusionCette série de cas prospective suggère qu’un examen échographique standardisé du contenu gastrique au chevet du patient permet à l’anesthésiologiste de mieux évaluer le risque d’inhalation, et entraîne des modifications importantes dans la prise en charge anesthésique des patients de chirurgie non urgente qui n’ont pas respecté les consignes de jeûne.

Novice performance of ultrasound-guided needling skills: effect of a needle guidance system.

Background and Objectives Ultrasound-guided needle placement is a widely used technical skill that can be challenging to learn. The SonixGPS is a novel ultrasound needle-tracking system that has the potential to improve performance over traditional ultrasound systems. The objective of our study was to determine if the use of the SonixGPS ultrasound system improves performance of novice practitioners in ultrasound-guided needle placement compared with conventional ultrasound in the out-of-plane approach on a simulation model. Methods Twenty-six medical students without previous ultrasound experience were randomized into 2 groups. Each group performed 30 simulated ultrasound nerve blocks on a porcine meat tissue simulation (phantom) model. Both groups used the SonixGPS ultrasound; however, the study group had the needle-tracking system activated, whereas the control group did not. The participants were assessed for success rate, technical aspects of block performance, and certain behaviors that could compromise the quality of the block. Learning curves were developed to assess competence. Results The needle guidance group reached competence more often. This group had fewer attempts and quality-compromising behaviors than did those using conventional ultrasound. Conclusions Use of the SonixGPS ultrasound needle guidance system improves the performance of technical needling skills of novice trainees in an ex vivo model. The place of this technology in the wider education of ultrasound-guided regional anesthesia remains to be established.

A valid and reliable assessment tool for remote simulation-based ultrasound-guided regional anesthesia.

Background and Objectives The purpose of this study was to establish construct and concurrent validity and interrater reliability of an assessment tool for ultrasound-guided regional anesthesia (UGRA) performance on a high-fidelity simulation model. Methods Twenty participants were evaluated using a Checklist and Global Rating Scale designed for assessing any UGRA block. The participants performed an ultrasound-guided supraclavicular brachial plexus block on both a patient and a simulator. Evaluations were completed in-person by an expert and remotely by a blinded expert using video recordings. Using previous number of blocks performed as an indication of expertise, participants were divided into Novice (n = 8) and Experienced (n = 12) groups. Construct validity was assessed through the tool’s reliable on-site and remote discrimination of Novice and Experienced anesthetists. Concurrent validity was established by comparisons of patient versus simulator scoring. Finally, interrater reliability was determined by comparing the scores of on-site and off-site evaluators. Results The Global Rating Scale was able to differentiate Novice from Experienced anesthetists both by on-site and remote assessment on a patient and simulation model. The Checklist was unable to discern the 2 groups on a simulation model remotely and was marginally significant with on-site scoring. Conclusions This is the first study to demonstrate the validity and reliability of a Global Rating Scale assessment tool for use in UGRA simulation training. Although the checklist may require further refinement, the Global Rating Scale can be used for remote and on-site assessment of UGRA skills.

Ondine's curse: anesthesia for laparoscopic implantation of a diaphragm pacing stimulation system.

PurposeCentral alveolar hypoventilation syndrome (CAHS) is a rare disease characterized by the loss of autonomic control of breathing. This condition causes hypoventilation and obstruction during sleep. Throughout their lives, these patients require ventilatory assistance by means of positive pressure ventilation to their lungs via mask, tracheotomy, or other means, such as phrenic nerve pacers. The diaphragm pacing stimulation system (DPSS) is a new treatment where electrodes are implanted into the diaphragm and cause contraction on stimulation. The DPSS has been used successfully in tetraplegic patients and patients suffering from amyotrophic lateral sclerosis (ALS). It has been shown to improve quality of life and to extend survival in patients with advanced respiratory muscle weakness. In our case, we describe the perioperative management of an adult patient with acquired CAHS who presented for laparoscopic DPSS insertion.Clinical featuresOur patient was a 50-yr-old female who developed CAHS at age thirteen after contracting encephalitis. Since the onset of her disease, she had been managed with positive pressure ventilation to her lungs via mask. Due to her longstanding disease, she presented with pulmonary hypertension and cor pulmonale and was scheduled for laparoscopic DPSS implantation. Our anesthetic technique included a total intravenous technique with remifentanil and propofol, and her trachea was intubated without the use of muscle relaxants. The pacemakers were switched on when the patient emerged from anesthesia, which provided her with ventilatory support and allowed us to extubate her trachea.ConclusionWe present the successful anesthetic management of an adult patient with CAHS undergoing laparoscopic DPSS insertion.RésuméObjectifLe syndrome d’hypoventilation alvéolaire centrale congénitale (HVACC) est une maladie rare qui se caractérise par la perte du contrôle autonome de la respiration. Cette affecte provoque de l’hypoventilation et une obstruction pendant le sommeil. Tout au long de leur vie, les patients atteints de ce syndrome nécessitent une assistance ventilatoire qui s’effectue en fournissant une ventilation en pression positive à leurs poumons via un masque, une trachéotomie, ou d’autres moyens, tels que les stimulateurs phréniques. Le stimulateur phrénique intradiaphragmatique est un nouveau traitement qui consiste à implanter des électrodes dans le diaphragme, lesquels provoquent une contraction lorsqu’elles sont stimulées. Le stimulateur phrénique intradiaphragmatique a été utilisé avec succès chez des patients tétraplégiques et des patients atteints de sclérose latérale amyotrophique (SLA). Il a été démontré que ce dispositif améliorait la qualité de vie et prolongeait la survie chez les patients atteints d’une faiblesse avancée des muscles respiratoires. Dans le cas présenté ici, nous décrivons la prise en charge périopératoire d’une patiente adulte atteinte d’une HVACC acquise qui s’est présentée pour l’insertion par laparoscopie d’un stimulateur phrénique intradiaphragmatique.Éléments cliniquesNotre patiente était une femme âgée de 50 ans qui a manifesté une HVACC à l’âge de treize ans après avoir contracté une encéphalite. Depuis l’apparition de sa maladie, elle a été prise en charge par ventilation en pression positive de ses poumons via un masque. En raison de sa maladie prolongée, elle s’est présentée avec une hypertension pulmonaire et un cœur pulmonaire; une chirurgie d’implantation par laparoscopie d’un stimulateur phrénique intradiaphragmatique a été prévue. Notre technique anesthésique consistait en une technique intraveineuse totale à l’aide de rémifentanil et de propofol, et l’intubation de la trachée a eu lieu sans curare. Les stimulateurs ont été enclenchés lorsque la patiente s’est réveillée de l’anesthésie, ce qui lui a procuré un soutien ventilatoire et nous a permis d’extuber sa trachée.ConclusionNous présentons la prise en charge anesthésique réussie d’une patiente adulte atteinte de HVACC subissant une insertion de stimulateur phrénique intradiaphragmatique par laparoscopie.