Biomedical subjects
Brian D Sites
Publications and source records attributed to Brian D Sites.
An abnormal clinical course of an ultrasound-guided supraclavicular brachial plexus block using 0.375% bupivacaine.
We report on the case of a reappearance of a supraclavicular nerve block after the apparent initiation of its resolution in a 21-year-old athlete undergoing repair of a valgus impaction syndrome of his right elbow. The patient's anesthetic management consisted of a supraclavicular nerve block and general anesthesia. The patient was discharged home with an apparent resolving nerve block. He returned to the hospital urgently when, at 7 hours after blockade, he lost all motor-sensory function in his arm. His workup ultimately yielded negative results, and the block resolved at 23 hours. In addition to documenting an abnormal course of a supraclavicular block, this case report questions the appropriateness of placing long-acting nerve blocks in outpatients.
Use of a nerve stimulator does not improve the efficacy of ultrasound-guided supraclavicular nerve blocks.
OBJECTIVE: To evaluate the efficacy of nerve stimulation as an adjunct to ultrasound-guided supraclavicular nerve blocks. DESIGN: Prospective database review. SETTING: Tertiary-care medical center. MEASUREMENTS: The records of 94 consecutive adult patients requiring surgery below the elbow and consenting to receive regional anesthesia were studied. The focus of this study was on supraclavicular nerve block using ultrasound guidance for nerve identification and needle localization. A nerve stimulator with a motor response lower than 0.5 mA was used for confirmation of findings. An ultrasound image was considered adequate if two trunks of the brachial plexus were visualized and if the needle was completely seen on the long axis. A successful block was defined as one that sufficed as the sole anesthetic without conversion to general anesthesia. Motor and sensory examination findings on the upper extremity were also evaluated. RESULTS: 74 patients had an adequate ultrasound image. Of the 64 patients with a positive motor response, 88% had a successful block, as compared with 90% of the 10 patients without a motor response (relative risk, 1.09; 95% confidence interval, 0.79-1.51; P = 0.52). Neither multivariate correction for baseline characteristics nor inclusion of the 20 patients with inadequate ultrasound images changed the results. CONCLUSION: For adequately imaged ultrasound-guided supraclavicular nerve blocks, a positive motor response to nerve stimulation does not increase the success rate of the block. In addition, the high false-negative rate suggests that these blocks are usually effective, even in the absence of a motor response. Nerve stimulation as an adjunct to ultrasound guidance may have a limited role.
Ultrasound guidance in peripheral regional anesthesia: philosophy, evidence-based medicine, and techniques.
PURPOSE OF REVIEW: This article introduces the use of ultrasound to facilitate peripheral regional anesthesia. RECENT FINDINGS: Regional anesthesia, despite its well known clinical benefits, has not gained the popularity of general anesthesia. This is secondary to multiple shortcomings including a defined failure rate, lack of simplicity, and the potential for patient discomfort or injury. Many of the negative aspects of regional anesthesia evolve from the reality that current nerve-localization techniques are unreliable. Given the great variation in human anatomy it is not surprising that even the most veteran clinician can be challenged by techniques that demand anatomical assumptions. The recent use of ultrasound imaging for nerve localization is an innovative application of an old technology which addresses many of the shortcomings of current techniques. Specifically, ultrasound imaging allows the operator to see neural structures, guide the needle under real-time visualization, navigate away from sensitive anatomy, and monitor the spread of local anesthetic. SUMMARY: Ultrasound technology represents an ideal mechanism by which the regional anesthesiologist can attain the safety, speed, and efficacy of general anesthesia. Ultimately, it is the correct peri-neural spread of local anesthetic around a nerve that provides safe, effective, and efficient anesthetic conditions.
A single injection ultrasound-assisted femoral nerve block provides side effect-sparing analgesia when compared with intrathecal morphine in patients undergoing total knee arthroplasty.
Postoperative pain after total knee arthroplasty (TKA) is severe, and achieving adequate analgesia remains a clinical challenge. We tested the hypothesis that, in patients having unilateral TKA under intrathecal (IT) anesthesia, the addition of a femoral nerve block would provide superior analgesia when compared with IT morphine and demonstrate fewer adverse side effects. In a single-blinded and controlled trial, 41 ASA I-III patients undergoing unilateral TKA were randomized into 2 groups. Both groups received 15 mg of IT hyperbaric bupivacaine for the surgical anesthetic. Group ITM received 250 microg of IT morphine and group FNB received an ultrasound-assisted femoral nerve block with 40 mL of 0.5% ropivacaine, 5 microg/mL of epinephrine, and 75 microg of clonidine. At 1, 2, 4, 6, 12, and 24 h postoperatively, we measured visual analog scales for pain, cumulative IV morphine consumption, hemodynamics, and side effects. There were no statistically significant differences in morphine consumption, pain at rest, or pain with movement. However, group FNB had fewer perioperative side effects including nausea, vomiting, and pruritus (P < 0.05 for each event). This corresponded to a decrease in patient satisfaction in group ITM, in which 20% of the patients rated their experience as "unsatisfactory" (P < 0.05). We conclude that, in comparison with IT morphine, a single injection femoral nerve block provides equivalent analgesia but with a significant reduction in side effects for patients having TKA under bupivacaine intrathecal anesthesia.
Single-dose caudal anaesthesia for two infants undergoing diagnostic brain magnetic resonance imaging: high risk and nonhigh risk.
We present a case report of two infants given a bupivacaine caudal anaesthetic as a means of achieving sedation for a diagnostic brain magnetic resonance imaging (MRI). Patient 1 was born at 27 weeks of gestation and presented to our hospital at 39 weeks postconception with a history of bronchopulmonary dysplasia and apnoea/bradycardia spells. He was undergoing a brain MRI for the work up of persistent apnoea and craniofacial abnormalities. Patient 2 was a term infant at 42 weeks postconception undergoing a MRI for the work up of a seizure disorder. Both infants fell asleep shortly after placement of the caudal blocks and the studies were completed successfully without complications. Utilizing this technique, we avoided dealing with a potentially difficult airway (patient 1), exacerbating postoperative apnoea and the negative implications of intravenous sedation during a study where there is limited access to the patient's airway.
Intrathecal clonidine added to a bupivacaine-morphine spinal anesthetic improves postoperative analgesia for total knee arthroplasty.
UNLABELLED: Postoperative pain after total knee arthroplasty (TKA) is severe and can complicate early physical therapy. We tested the hypothesis that intrathecal clonidine would improve postoperative analgesia for TKA using a hyperbaric bupivacaine spinal anesthetic. In a double-blinded, placebo-controlled protocol, 81 ASA physical status I-III patients undergoing either a single or bilateral TKA were randomized into 4 groups with the following 2-mL solutions added to 15 mg of hyperbaric bupivacaine: 1) sterile saline, 2) morphine (250 microg), 3) morphine (250 microg) with clonidine (25 microg), and 4) morphine (250 microg) with clonidine (75 microg). At 1, 2, 4, 6, 12, and 24 h postoperatively, we measured visual analog scales (VAS), cumulative IV morphine consumption, hemodynamics, nausea, ancillary drugs, and side effects. Our primary comparison was between the clonidine with morphine groups versus the morphine group. We found that the combined administration of intrathecal clonidine and morphine decreased 24 h IV morphine consumption by 13 mg (P = 0.028) when compared with intrathecal morphine alone. This corresponded to a decrease in the VAS score of 1.3 cm at 24 h postoperatively (P = 0.047). Adverse side effects were similar among all groups with the exception of more relative hypotension in the clonidine groups through postoperative hour 6. We conclude that the coadministration of intrathecal clonidine and morphine decreases the 24-h IV morphine consumption and improves the 24-h VAS score when compared with intrathecal morphine alone. IMPLICATIONS: In this prospective, randomized, double-blinded, and placebo-controlled trial, we identify an effective postoperative analgesic approach in total knee replacement surgery. Intrathecal morphine (250 microg) combined with clonidine (25 or 75 microg) provided superior analgesia compared with intrathecal morphine alone.
The use of magnetic resonance imaging to evaluate the accuracy of a handheld ultrasound machine in localizing the sciatic nerve in the popliteal fossa.
BACKGROUND AND OBJECTIVE: Ultrasound has become an increasingly popular modality in facilitating the performance of peripheral nerve blocks. There is a paucity of data describing techniques of ultrasound-guided sciatic nerve blocks. By using magnetic resonance imaging (MRI) as a gold standard, the objective of this study was to describe the ability of a handheld ultrasound machine to accurately locate the sciatic nerve. METHODS: Ten patients were prospectively enrolled and placed in the prone position. By using a 4- to 7-MHz ultrasound transducer, the sciatic nerve was visualized in short axis between 5 to 10 cm above the popliteal crease. The distance from the skin to the nerve was measured by ultrasound, and a MRI lucent marker was placed at this site. This process was repeated in one additional location. The patient was then placed supine in the MRI scanner and short-axis T1-weighted images were obtained. On the MRI image, we recreated the 2 lines extending down from the markers using the distances previously measured by ultrasound. The point of intersection of these 2 lines represents the ultrasound-determined location of the sciatic nerve, which was then compared with the midpoint of the nerve complex on MRI. RESULTS: The sciatic nerve was easily visualized by ultrasound in all 10 patients. MRI showed the division of the sciatic nerve in 9 out of 10 patients. Ultrasound was able to confirm this division in 7 patients. The mean distance between the MRI and ultrasound midpoint location of the sciatic nerve was 2.9 +/- 1.3 mm. CONCLUSIONS: The data presented here suggest that the specific ultrasound machine evaluated in this study can accurately localize the sciatic nerve in the popliteal fossa.
The learning curve associated with a simulated ultrasound-guided interventional task by inexperienced anesthesia residents.
BACKGROUND AND OBJECTIVE: Ultrasound has become an increasingly popular modality in facilitating the performance of peripheral nerve blocks. There exists no literature that examines the learning curve of the ultrasound novice. In this prospective series, we evaluated the learning curve of inexperienced anesthesia residents in performing a simulated ultrasound-guided interventional procedure. In doing so, we hoped to identify reproducible patterns of human errors, which could potentially aid in the prevention of real-life iatrogenic injuries. METHODS: Ten subjects were prospectively enrolled. After a brief introduction to the ultrasound system, the subjects were asked to perform 6 sequential trials of a simulated breast cyst aspiration. For the first 3 trials, each subject attempted to place a 22-gauge b-bevel needle into any aspect of an olive buried inside the turkey breast. After completion of these 3 trials, the subjects were asked to place the needle into the exact midpoint of the olive wall closest to the transducer. Trials were videotaped and analyzed for task performance in terms of speed and accuracy. RESULTS: All subjects successfully completed the 6 interventional trials. The mean time to perform the task was reduced by 38% and 48%, respectively, for the second and third trials. A composite score of accuracy showed an improvement of 36% and 59%, respectively, for the second and third trials. The most common committed error, which occurred in 7 of 10 subjects, was the failure to accurately image the needle while advancing. This resulted in excessive depth of penetration and inadvertent transfixation of the olive in 5 of these subjects. CONCLUSIONS: Anesthesiology residents, with little or no ultrasound experience, can rapidly learn and improve their speed and accuracy in performing a simulated interventional ultrasound procedure. A concerning novice pattern was identified where the subjects advanced the needle even though it was not appropriately visualized in the ultrasound beam. This resulted in needle placement error, which could cause iatrogenic injury in the clinical setting.
Ultrasound-guided musculocutaneous nerve block: a description of a novel technique.
BACKGROUND AND OBJECTIVE: Localizing the musculocutaneous nerve for neural blockade is crucial to providing surgical anesthesia for the distal forearm. We present a novel approach for localizing and anesthetizing the musculocutaneous nerve. CASE REPORTS: Ten patients underwent successful ultrasound-guided musculocutaneous nerve blocks. In this technique, either a 10-MHz or a 12-MHz linear probe was placed at the junction of the pectoralis major muscle and the biceps muscle such that the axillary artery was visualized in cross section. The probe was moved towards the biceps muscle until the musculocutaneous nerve was visualized lying between the coracobrachialis and biceps muscles. A 22-gauge, 50-mm b-bevel needle was inserted under direct vision until the needle was adjacent to the nerve. Local anesthetic was then injected, which generated surgical anesthetic conditions in all patients. CONCLUSION: Ultrasound can facilitate the localization and local anesthetic block of the musculocutaneous nerve.
On the edge of the ultrasound screen: Regional anesthesiologists diagnosing nonneural pathology.
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Ultrasound-guided popliteal block demonstrates an atypical motor response to nerve stimulation in 2 patients with diabetes mellitus.
BACKGROUND AND OBJECTIVES: Nerve stimulation is a useful technique to identify peripheral nerves before blockade. We report 2 cases of the failure of nerve stimulation to accurately localize the sciatic nerve in patients with diabetes mellitus undergoing outpatient foot procedures. We also introduce a novel approach to performing a popliteal fossa block using ultrasound guidance. CASE REPORT: Ultrasound-guided popliteal fossa blocks were performed in 2 patients with diabetes mellitus. Both patients failed to develop an appropriate motor response or paresthesia to nerve stimulation. The needle positions were confirmed by ultrasound guidance and injections of local anesthesia were made uneventfully. Appropriate surgical anesthesia was established and the procedures were performed uneventfully. CONCLUSION: Ultrasound facilitated the accurate localization of the sciatic nerve in 2 patients with diabetes mellitus. Neither patient had a paresthesia or muscle twitch below 2.4 mA. There is theoretical concern that patients with underlying neuropathy, such as patients with diabetes mellitus, may have an altered response to either motor or sensory stimulation.