Steven L. Orebaugh

Ultrasound guidance with nerve stimulation reduces the time necessary for resident peripheral nerve blockade.

Background and Objectives: Educating residents in peripheral nerve blockade may impact the efficiency of a busy regional anesthesia service. Ultrasound guidance may affect the efficiency and effectiveness of nerve block. We examined the impact of ultrasound guidance on resident performance of peripheral nerve block in a regional anesthesia rotation. Methods: An existing de-identified database was used for retrospective analysis of resident performance of interscalene, axillary, femoral, and popliteal nerve blocks, by peripheral nerve stimulator guidance alone and by nerve stimulator aided by ultrasound. The primary variable examined was the time required to perform the block. Others variables included (1) number of needle insertions; (2) proportion of blocks in which there was a blood vessel puncture; and (3) block efficacy. Peripheral nerve-stimulator blocks were guided by surface anatomy and motor stimulation, refined to 0.2 to 0.5 mA of current before injection of local anesthetic, while ultrasound nerve stimulator blocks were confirmed using a current of 0.5 mA. Results: Ultrasound-aided blocks required less time to perform (median = 1.8 min) than nerve stimulator-guided blocks (median = 6.5 min, P < .001). More needle insertions were required for nerve localization in the nerve stimulator-guided blocks (median = 6) than in ultrasound-aided blocks (median = 2; P < .001). There were fewer blood vessel punctures with ultrasound-aided blocks (P = .03). Conclusions: During resident teaching, ultrasound-aided peripheral nerve-stimulated block required less time to perform than did nerve-stimulator-guided blocks. Fewer needle insertions were required to perform the ultrasound-guided blocks, and there were fewer blood vessel punctures when ultrasound was used.

Adverse outcomes associated with stimulator-based peripheral nerve blocks with versus without ultrasound visualization.

Background and Objectives: In this retrospective study, we queried our Quality Improvement database of anesthetic-related complications to evaluate the frequency of noncatheter peripheral nerve block-related adverse occurrences. We hypothesized that adverse complications of nerve blockade are less common when ultrasonography is used in conjunction with peripheral nerve stimulation to guide needle placement, when compared with the sole use of physical landmarks and nerve stimulation. Methods: We queried our departmental Quality Improvement electronic database for adverse outcomes associated with peripheral nerve blocks. Billing records were used to provide the denominator of the total number of blocks using both techniques of neurolocation. The types of blocks considered in this analysis were interscalene, axillary, femoral, sciatic, and popliteal sciatic blocks. The total numbers of complications of nerve blockade with each type of guidance were then compared, as were specific subsets of adverse effects. Results: There were 5436 consecutive peripheral noncatheter block cases (interscalene, axillary, femoral, sciatic, popliteal) during the 28-month period surveyed, with 3290 guided by landmark-nerve stimulation, and 2146 by ultrasound-nerve stimulation. Eight adverse outcomes occurred among patients having blocks guided by landmark-nerve stimulation technique, including 5 seizures and 3 nerve injuries. There were no such occurrences in the ultrasound-nerve stimulation group. When comparing the 4 brachial plexus block-related seizures that occurred with landmark guidance versus none with ultrasound guidance, the associated risk of seizures reached statistical significance (P = 0.044 by Fisher exact test). There was no difference between the 2 groups in the number of seizures occurring with lower extremity blocks, or in the frequency of neurologic injury. Conclusions: High-definition ultrasonography offers potential advantages in the administration of peripheral nerve blockade. The significant difference in major central nervous system local anesthetic toxicity observed in this study supports the use of ultrasound guidance in conjunction with peripheral nerve stimulation to provide brachial plexus peripheral nerve blockade in an academic, ambulatory anesthesia practice.

Adverse outcomes associated with nerve stimulator-guided and ultrasound-guided peripheral nerve blocks by supervised trainees: update of a single-site database.

Background We previously published a retrospective review of complications related to peripheral nerve blocks performed by supervised trainees, from our quality assurance and billing data, guided by either ultrasound, with nerve stimulator confirmation, or landmark-based nerve stimulator techniques. This report updates our results, for the period from May 2008 through December 2011, representing ongoing transition to near-complete combined ultrasound/nerve stimulator guidance in a block-oriented, outpatient orthopedic anesthesia practice. Methods We queried our deidentified departmental quality improvement electronic database for adverse outcomes associated with peripheral nerve blocks. Billing records were also deidentified and used to provide the denominator of total number of blocks using each technique of neurolocation. The types of blocks considered in this analysis were interscalene, axillary, femoral, sciatic, and popliteal-sciatic blocks. Nerve block complications based on each type of guidance were then compared for the entire recent 30-month time period, as well as for the 6-year period of this report. Results There were 9062 blocks performed by ultrasound/nerve stimulator, and 5436 by nerve stimulator alone over the entire 72-month period. Nerve injuries lasting longer than 1 year were rare, but similar in frequency with both nerve guidance techniques. The incidence of local anesthetic systemic toxicity was found to be higher with landmark–nerve stimulator technique than with use of ultrasound-guided nerve blocks (6/5436 vs 0/9069, P = 0.0061). Conclusions We report a large series of combined ultrasound/nerve stimulator nerve blocks by supervised trainees without major local anesthetic systemic toxicity. While lacking the compelling evidence of randomized controlled trials, this observational database nonetheless allows increased confidence in the safety of using combined ultrasound/nerve stimulator in the setting of anesthesiologists-in-training.

Future considerations for pharmacologic adjuvants in single-injection peripheral nerve blocks for patients with diabetes mellitus.

Abstract As the epidemics of obesity and diabetes expand, there are more patients with these disorders requiring elective surgery. For surgery on the extremities, peripheral nerve blocks have become a highly favorable anesthetic option when compared with general anesthesia. Peripheral blocks reduce respiratory and cardiac stresses, while potentially mitigating untreated peripheral pain that can foster physiologic conditions that increase risks for general health complications. However, local anesthetics are generally accepted to be a rare but possible cause of nerve damage, and there are no evidence-based recommendations for dosing local anesthetic nerve blocks in patients with diabetes. This is important because anesthesiologists do not want to potentially accelerate peripheral nerve dysfunction in diabetic patients at risk. This translational vignette (i) examines laboratory models of diabetes, (ii) summarizes the pharmacology of perineural adjuvants (epinephrine, clonidine, buprenorphine, midazolam, tramadol, and dexamethasone), and (iii) identifies areas that warrant further research to determine viability of monotherapy or combination therapy for peripheral nerve analgesia in diabetic patients. Conceivably, future translational research regarding peripheral nerve blocks in diabetic patients may logically include study of nontoxic injectable analgesic adjuvants, in combination, to provide desired analgesia, while possibly avoiding peripheral nerve toxicity that diabetic animal models have exhibited when exposed to traditional local anesthetics.

Subepineurial injection in ultrasound-guided interscalene needle tip placement.

Introduction: The neural elements of the brachial plexus between the anterior and middle scalene muscles are readily visible by ultrasound. However, the epineurium of these nerve structures is difficult to discern on ultrasound imaging because of the proximity of the scalene muscles to the nerve elements, and this may lead to unintentional subepineurial injection (SEI). To evaluate whether typical needle tip placement under ultrasound guidance results in SEI, as opposed to extraneural injection, we undertook this cadaver study. Materials and Methods: Six nonpreserved cadavers served as subjects for 10 injections. After imaging revealed the hypoechoic fascicles of the brachial plexus at the interscalene level, the tip of a 22-gauge, 5-cm short-bevel needle was inserted into a position adjacent to one of the fascicles by ultrasound guidance. At this point, 0.1 to 0.2 mL of india ink solution was injected. The brachial plexus at this level was then dissected and removed. The nerve elements discolored by the ink were removed, fixed, and stained for histologic analysis and were then examined for evidence of subepineurial ink deposition. Four nerve segments, which were unaffected by the injected ink, served as controls. These were subjected to topical india ink application for a 60-min period and were then washed, fixed, and stained for histologic analysis. Results: In all 10 interscalene sites, ultrasonography revealed multiple hypoechoic nodules that could be traced proximally to the spine, as in live subjects. On gross analysis after dissection, the superficial nerve elements of the brachial plexus appeared to be stained by the ink. On histologic examination, 5 of 10 nerve specimens revealed ink within the epineurium (subepineurial), whereas in the other 5, it had not penetrated this barrier. The india ink did not penetrate the perineurium in any of the specimens. Among control specimens, none had evidence of subepineurial ink. Conclusions: In a cadaver model of needle tip placement for ultrasound-guided interscalene block, we found that SEI occurred more frequently than expected.

Difficult airway management in the emergency department

Most airway management in the emergency department is straightforward and readily accomplished by the emergency physician. The exact incidence of difficult intubations is difficult to discern from available evidence, but these are probably more frequent in the Emergency Department than in the operating room, given the urgent nature of the procedure and the lack of preparation of the patient population. A variety of adjuncts for airway management are available to assist in both intubation and ventilation. The utility of these adjuncts is detailed in this review, with emphasis on techniques most useful to the emergency physician.

Succinylcholine: Adverse effects and alternatives in emergency medicine

Succinylcholine has long been the favored neuromuscular blocking agent for emergent airway management because of its rapid onset, dependable effect, and short duration. However, it has a plethora of undesirable side effects, ranging from the inconsequential to the catastrophic. When patients requiring tracheal intubation present with potential contraindications to succinylcholine use, the emergency physician will need to substitute a rapid-onset nondepolarizing neuromuscular blocking agent, such as rocuronium or mivacurium. An understanding of the pharmacology of these agents is essential.

Brachial plexus root injection in a human cadaver model: Injectate distribution and effects on the neuraxis

Background The potential for injection into the brachial plexus root at cervical levels must be considered during interscalene block or chronic pain interventions in the neck, but this phenomenon has not been well studied. In this investigation, we performed injections into the brachial plexus roots of unembalmed cadavers, with real-time ultrasound guidance, to evaluate the proximal and distal spread of the injected fluids, the potential of the injectate to reach the neuraxis, and whether the injectate could migrate into the actual substance of the spinal cord itself. Methods A solution of particulate dye mixed with local anesthetic was injected into 8 brachial plexus roots at a lower cervical level, in unembalmed cadaver specimens, utilizing an automated pump and pressure monitor. Two injections were made adjacent to nerve roots as controls. The specimens were then dissected, and gross and microscopic analysis utilized to determine the distribution of the dye and the structures affected. Results The mean peak pressure achieved during plexus root injections was 48.9 psi. After injections into the plexus root, dye was evident within the neural tissue at the level of injection and spread primarily distally in the plexus. In 1 of 8 injections into the brachial plexus root, the dye in the injectate spread proximally into the spinal canal, but in none of the injections was the spinal cord affected by the dye. Conclusions Injection directly into the neural tissue of a brachial plexus root in a cadaver model produced high pressures suggestive of intrafascicular injection and widespread flow of the injectate through the distal brachial plexus. However, proximal movement of the dye-containing injectate was more restricted, with only 1 of the injections leading to epidural spread and no apparent effects on the spinal cord.

Outcomes of shoulder surgery in the sitting position with interscalene nerve block: a single-center series.

Background Several case reports have raised serious concerns about the safety of shoulder surgery in the beach-chair position, related to global cerebral hypoperfusion. We summarize our experiences with 15,014 cases of shoulder arthroscopy over an 11-year period. Our primary aim was to evaluate the incidence of intraoperative or immediate postoperative neurologic events and secondarily to relate other perioperative complications. Methods We searched our online deidentified departmental quality improvement and patient safety database for adverse outcomes associated with arthroscopic shoulder surgery performed in the beach-chair position for the 11-year period between April 2001 and November 2011, as well as our hospital-system database and a statewide database. This was compared with the total number of such cases, available from our department billing database. Results The total rate of adverse events was 0.37%. Neurologic abnormalities suggestive of acute cerebral ischemia or hemorrhage did not occur in the immediate perioperative period. One new neurologic deficit was reported, secondary to ischemic stroke, which occurred 24 hours after the surgery. The most frequent complications detected were unplanned return to care (0.067%), local anesthetic systemic toxicity (0.053%), and airway compromise requiring unplanned intubation (0.033%). Complications were infrequent and did not vary in incidence over the course of the study. Conclusions This retrospective study suggests that intraoperative or immediate postoperative stroke is rare when surgery is conducted in beach-chair position in conjunction with regional anesthesia, propofol sedation, and spontaneous respiration via natural airway.

Interscalene block using ultrasound guidance: impact of experience on resident performance.

Background: We evaluated the weekly progress of anesthesiology residents performing an interscalene block with ultrasound guidance (UG) for block success rates and for the specific time intervals: (i) time to image the brachial plexus and (ii) time from insertion of the block needle until motor stimulation occurred. Our primary objective was to characterize the influence of experience over the course of the regional anesthesia rotation on the performance of a UG interscalene block by anesthesiology residents.