Brian C. Spence

Characterizing novice behavior associated with learning ultrasound-guided peripheral regional anesthesia.

Background and Objectives: Ultrasound-guided regional anesthesia is a rapidly growing field. There exists little information regarding the competencies involved with such a practice. The objective of this exploratory study was to characterize the behavior of novices as they undertook the challenges of learning a new technique. In addition to assessing for both committed errors and accuracy, we aimed to identify previously unrecognized quality-compromising behaviors that could help structure effective training interventions. Methods: By using detailed video analyses, the performances of 6 anesthesia residents were evaluated while on a dedicated 1-month rotation in ultrasound-guided regional anesthesia. From these video reviews, we assessed accuracy, errors committed, performance times, and searched for previously unrecognized quality-compromising behaviors. Results: A total of 520 nerve blocks were videotaped and reviewed. All residents performed at least 66 nerve blocks, with an overall success rate of 93.6% and 4 complications. Both speed and accuracy improved throughout the rotation. There were a total of 398 errors committed, with the 2 most common errors consisting of the failure to visualize the needle before advancement and unintentional probe movement. Five quality-compromising patterns of behavior were identified: (1) failure to recognize the maldistribution of local anesthesia, (2) failure to recognize an intramuscular location of the needle tip before injection, (3) fatigue, (4) failure to correctly correlate the sidedness of the patient with the sidedness of the ultrasound image, and (5) poor choice of needle-insertion site and angle with respect to the probe preventing accurate needle visualization. Conclusions: Based on the analysis of the committed errors and the identification of quality-compromising behaviors, we are able to recommend important targets for learning in future training and simulation programs.

Ultrasound guidance improves the success rate of a perivascular axillary plexus block.

Background:  Traditional approaches to performing brachial plexus blocks via the axillary approach have varying success rates. The main objective of this study was to evaluate if a specific technique of ultrasound guidance could improve the success of axillary blocks in comparison to a two injection transarterial technique.

Artifacts and pitfall errors associated with ultrasound-guided regional anesthesia. Part II: a pictorial approach to understanding and avoidance.

t o l he use of real-time ultrasound guidance in regional anesthesia is growing in popularity. Parmount to the successful and safe use of ultrasound s the appreciation and accurate interpretation of ommon ultrasound-generated artifacts. An artifact s any perceived distortion, error, or addition caused y the instrument of observation (signal procesor).1 Imaging artifacts can be considered display henomena, and, therefore, can potentially compliate the planned procedure. There are 4 generic ategories of imaging artifacts:2 (1) Acoustic: error n presentation of ultrasound information; (2) Antomic: error in interpretation (often called “pitfall” rror); (3) Optical illusion: error in perception; and 4) Other: electrical noise. This article builds on the fundamental principles f ultrasound physics that are discussed in Part I of his article.3 The objective of this article is to decribe and illustrate many of the acoustic and anaomic artifacts commonly encountered by the reional anesthesiologist. In the process, we will offer nderlying physical explanations and describe pracical tips on how to negotiate these often misleading henomena.

Artifacts and pitfall errors associated with ultrasound-guided regional anesthesia. Part I: understanding the basic principles of ultrasound physics and machine operations.

w 1 c b p m t t t c a r s ltrasound guidance in regional anesthesia has grown in popularity over the past 5 years. Its ttractiveness stems from the unprecedented ability o visualize the target nerve, approaching needle, nd the real-time spread of local anesthetic.1 As ltrasound experience grows within the regional nesthesia community, the limitations and chalenges begin to declare themselves. Chief among hese limitations are ultrasound-generated artifacts. ecognition of such optical events combined with n appreciation of the mechanisms involved suports a high quality ultrasound-guided regional ansthesia practice. The objective of this article (Part I) s to describe the physical properties of ultrasound ost relevant to the regional anesthesiologist so hat clinical sonographic imaging can be optimized nd common ultrasound-generated artifacts (disussed in more detail in Part II2) can be recognized.

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.

Regional anesthesia meets ultrasound: a specialty in transition

Despite its well‐known benefits, regional anesthesia has not attained the stature, simplicity, and safety of general anesthesia. Many of the challenges and clinical failures of regional anesthetic techniques can be attributed to fact that neurovascular anatomy is highly variable. Furthermore, current nerve localization techniques provide little or no information regarding the anatomical spread local anesthesia. Recently, ultrasound technology has been utilized by anesthesiologists in an attempt to minimize many of the drawbacks of traditional nerve block techniques. This review article will update the reader on the current status of ultrasound‐guided regional anesthesia, provide an evidence‐based context, and supply key facts regarding ultrasound physics. In the process, we will also highlight several possible limitations of ultrasound techniques including learning curve issues, costs, and artifact generation.

On the edge of the ultrasound screen: Regional anesthesiologists diagnosing nonneural pathology.

c c t a p o a a t ( u W r o fi u a s a i d D t i t t o ltrasound technology in one form or another is used by almost every specialty of medicine. mong anesthesiologists, ultrasound has been acepted for transesophageal echocardiography (TEE) nd for facilitation of central venous access. Reently, ultrasound has gained popularity for neural maging in regional anesthesia. As these regional nesthetic applications of ultrasound evolve and roaden, legitimate questions will arise regarding he training, credentialing, and legal implications or the anesthesiologist interested in adopting this echnology. Since August 2002, a review of our regional ansthesia database revealed that 8 cases of unexected pathology were diagnosed by ultrasound in ,027 ultrasound-guided nerve blocks (Table 1). he maintenance of this prospective database is pproved by the Committee for the Protection of uman Subjects (CPHS) at Dartmouth Medical chool. The CPHS does not require individual aproval for the publication of case reports. This artile highlights 3 patients in whom the ultrasound iagnosis resulted in both therapeutic and aneshetic management changes. These cases provide a oundation for a discussion of the scope of practice f the anesthesiologist who performs neural and onneural imaging. Specifically, should the anes-

CRITICAL CARE ISSUES FOR THE NEPHROLOGIST: Perioperative Fluid Management: Current Consensus and Controversies

The scientific knowledge base that supports clinical decisions about perioperative fluid management continues to evolve. However, despite these advancements in the understanding of the physiology of fluid replacement, the definition of ‘‘optimal’’ perioperative fluid management remains a matter of clinical judgment. With an appreciation of the many factors, both sensible and insensible, that contribute to changes in blood and extracellular fluid volume during surgery, clinicians have tried to create reproducible and generally applicable formulas for replacement of fluid during surgery. These formulas have been challenged recently by the introduction of new tools for monitoring cardiopulmonary function, by the implementation of monitor‐guided protocols for fluid management, and, more recently, by clinical data suggesting that fluid restriction may improve surgical outcomes in some clinical settings. The relative ease of pre‐identified fluid replacement protocols is being slowly replaced by data‐guided interventions that take into account a variety of factors. Clinicians are therefore required to tailor their fluid replacement strategies based on preoperative patient characteristics, the type of surgery and even the type of anesthetic that is utilized. Some of the benefits of this new approach range from relatively ‘‘minor’’ outcomes such as diminished nausea after surgery to preventing postoperative complications such as wound breakdown and cardiopulmonary failure.

Mass in the left main coronary artery after aortic valve replacement.

An 88-year-old man with a medical history significant for hypertension and hyperlipidemia presented for primary aortic valve replacement (AVR) for worsening symptoms of shortness of breath with exertion. The patient was brought to the operating room where, after a standard anesthetic induction was performed, a TEE probe was placed along with a pulmonary artery (PA) catheter for monitoring. The precardiopulmonary bypass TEE examination revealed severe thickening and fusion of all 3 leaflets of the aortic valve with a peak instantaneous gradient of 51 mm Hg and a mean gradient of 35 mm Hg. The left ventricular ejection fraction was mildly reduced with anterolateral wall hypokinesis and an overall ejection fraction of 45%. Examination of the aorta revealed atheromatous plaque of 5 mm in the ascending, arch, and descending aorta. There were no other major valvular abnormalities. After institution of cardiopulmonary bypass, the native aortic valve was excised and a 25-mm Magna Ease Pericardial prosthetic valve (Edwards Lifesciences, LLC, Irvine, CA) was inserted without incident. During the de-airing process, a small echogenic object was noticed entering and retracting from the orifice of the left main coronary artery (Fig. 1) (Video 1, see Supplemental Digital Content 1, http://links.lww.com/AA/A216; see Appendix for video legend) without causing complete obstruction of the coronary circulation by color flow Doppler. There were no associated wall motion abnormalities. After discussion of these findings with the surgeon, the decision was made to rearrest the heart and reexplore the aorta. Upon reopening the aorta, a piece of free suture material approximately 1 cm in length was discovered at the orifice of the left main coronary artery and was removed. Subsequently, the patient was weaned from cardiopulmonary bypass without incident. A postcardiopulmonary bypass TEE examination revealed no object in the orifice of the left main coronary artery. Color flow Doppler assessment revealed a normal functioning bioprosthetic valve without aortic insufficiency or perivalvular leak. Continuous wave Doppler demonstrated a peak instantaneous gradient of 12 mm Hg and a mean gradient of 5 mm Hg across the prosthetic valve. The patient’s recovery was without incident and he was discharged home on the sixth postoperative day. Coronary artery occlusion is a documented complication of AVR and can be classified into 1 of 3 primary etiologies: coronary dissection, acute coronary lumen obstruction, or delayed coronary lumen stenosis. Coronary artery dissection can occur after AVR, aortic dissection, trauma to the chest, or even spontaneously in young healthy adults. Angiography is still considered the “gold standard” for coronary artery imaging; however, TEE is useful in diagnosis both in terms of imaging the proximal coronary anatomy and any associated wall motion abnormalities in the affected coronary distribution. A midesophageal (ME) short-axis view of the aortic valve is used to image both the left and right coronary ostia, whereas an ME long-axis view is used to visualize the right coronary ostium. A dissection flap sometimes can be imaged in the ostia of the affected coronary artery when a dissection is present. The intima of the aorta can also be sheared during valve replacement with a flap being present after the procedure. In this instance, the echogenicity of the intimal lesion will be similar to the surrounding tissue. Acute coronary lumen obstruction is usually embolic in nature. Embolic sources that have been described are foreign bodies, air, thrombus, and surgical sealant. These emboli most likely would not be seen directly on TEE examination. A new wall motion abnormality could suggest their presence. Delayed proximal coronary artery stenosis is a welldescribed complication of coronary ostia cannulation. Intimal thickening may be appreciated on TEE; however, coronary angiography remains the preferred method of diagnosis. Ultrasound artifacts are common after an AVR because the prosthetic valve can disrupt the typical echocardiographic images. The strongly reflective prosthetic material attenuates ultrasound distally causing dropout shadows from the sewing ring, struts, or any metallic component making interrogation of structures distal to the prosthetic difficult. These artifacts tend to be more prominent with mechanical prosthetic valves compared with bioprosthetic valves because echocardiographic windows may be present through the central “tissue” regions of the bioprosthetic valves. An in situ PA catheter can form reverberation artifacts and side-lobe artifacts into adjacent structures. The reverberation artifact would be distal to the PA catheter whereas the aortic valve is proximal in the ME short-axis view. A side-lobe artifact can originate from the prosthetic valve, the ascending aorta, or the PA catheter. It would present as an object at a constant radial distance from the transducer, it may be of different echogenicity compared with the surrounding tissue, and would traverse structures without regard to physical boundaries. These key attributes are used to differentiate an artifact from an intimal flap. The intimal flap would have a similar echogenic signature, because the surrounding tissue and the flap would not cross physical boundaries as an artifact potentially would. An intimal flap could also be of varying distance From the Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, Dartmouth Medical School, Lebanon, New Hampshire.

The Afferent Limb of Rapid Response Systems: Continuous Monitoring on General Care Units

The prevention of adverse events continues to be the focus of patient safety work. Although rapid response systems have improved the efferent limb of the patients rescue, the detection of the patients deterioration (the afferent limb) has not been solved. This article provides an overview of the complex issues surrounding patient surveillance by addressing the principal considerations of continuous monitoring as they relate to implementation, choice of sensors and physiologic variables, notification, and alarm balancing, as well as future research opportunities.