An Observational Study of the Pharmacokinetics of Surgeon-Performed Intercostal Nerve Blockade With Liposomal Bupivacaine for Posterior-Lateral Thoracotomy Analgesia.

BACKGROUND: Intercostal nerve blocks with liposomal bupivacaine are commonly used for thoracic surgery pain management. However, dose scheduling is difficult because the pharmacokinetics of a single-dose intercostal injection of liposomal bupivacaine has never been investigated. The primary aim of this study was to assess the median time to peak plasma concentration (Tmax) following a surgeon-administered, single-dose infiltration of 266 mg of liposomal bupivacaine as a posterior multilevel intercostal nerve block in patients undergoing posterolateral thoracotomy. METHODS: We chose a sample size of 15 adults for this prospective observational study. Intercostal injection of liposomal bupivacaine was considered time 0. Serum samples were taken at the following times: 5, 15, and 30 minutes, and 1, 2, 4, 8, 12, 24, 48, 72, and 96 hours. The presence of sensory blockade, rescue pain medication, and pain level were recorded after the patient was able to answer questions. RESULTS: Forty patients were screened, and 15 patients were enrolled in the study. Median (interquartile range [IQR]) Tmax was 24 (12) hours (confidence interval [CI], 19.5-28.5 hours) with a range of 15 minutes to 48 hours. The median (IQR) peak plasma concentration (Cmax) was 0.6 (0.3) µg/mL (CI, 00.45-0.74 µg/mL) in a range of 0.3-1.2. The serum bupivacaine concentration was undetectable (<0.2 µg/mL) at 96 hours in all patients. There was significant variability in reported pain scores and rescue opioid medication across the 15 patients. More than 50% of patients had return of normal chest wall sensation at 48 hours. All patients had resolution of nerve blockade at 96 hours. No patients developed local anesthetic toxicity. CONCLUSIONS: This study of the pharmacokinetics of liposomal bupivacaine following multilevel intercostal nerve blockade demonstrates significant variability and delay in systemic absorption of the drug. Peak serum concentration occurred at 48 hours or sooner in all patients. The serum bupivacaine concentration always remained well below the described toxicity threshold (2 µg/mL) during the 96-hour study period.

Comparison of expert and novice sonographers' performance in focused lung ultrasonography in dyspnea (FLUID) to diagnose patients with acute heart failure syndrome.

OBJECTIVES: The goal of this study was to examine the ability of emergency physicians who are not experts in emergency ultrasound (US) to perform lung ultrasonography and to identify B-lines. The hypothesis was that novice sonographers are able to perform lung US and identify B-lines after a brief intervention. In addition, the authors examined the diagnostic accuracy of B-lines in undifferentiated dyspneic patients for the diagnosis of acute heart failure syndrome (AHFS), using an eight-lung-zone technique as well as an abbreviated two-lung-zone technique. METHODS: This was a prospective, cross-sectional study of patients who presented to the emergency department (ED) with acute dyspnea from May 2009 to June 2010. Emergency medicine (EM) resident physicians, who received a 30-minute training course in thoracic US examinations, performed lung ultrasonography on patients presenting to the ED with undifferentiated dyspnea. They attempted to identify the presence or absence of sonographic B-lines in eight lung fields based on their bedside US examinations. An emergency US expert blinded to the diagnosis and patient presentation, as well as to the residents' interpretations of presence of B-lines, served as the criterion standard. A secondary outcome determined the accuracy of B-lines, using both an eight-lung-zone and a two-lung-zone technique, for predicting pulmonary edema from AHFS in patients presenting with undifferentiated dyspnea. Two expert reviewers who were blinded to the US results determined the clinical diagnosis of AHFS. RESULTS: A cohort of 66 EM resident physicians performed lung US on 380 patients with a range of 1 to 28 examinations, a mean of 5.8 examinations, and a median of three examinations performed per resident. Compared to expert interpretation, lung US to detect B-lines by inexperienced sonographers achieved the following test characteristics: sensitivity 85%, specificity 84%, positive likelihood ratio (+LR) 5.2, negative likelihood ratio (-LR) 0.2, positive predictive value (PPV) 64%, and negative predictive value (NPV) 94%. Regarding the secondary outcome, the final diagnosis was AHFS in 35% of patients (134 of 380). For novice sonographers, one positive lung zone (i.e., anything positive) had a sensitivity of 87%, a specificity of 49%, a +LR of 1.7, a -LR of 0.3, a PPV of 50%, and an NPV of 88% for predicting AHFS. When all eight lung zones were determined positive (i.e., totally positive) by novice sonographers, the sensitivity was 19%, specificity was 97%, +LR was 5.7, -LR was 0.8, PPV was 76%, and NPV was 68% for predicting AHFS. The areas under the curve for novice and expert sonographers were 0.77 (95% CI = 0.72 to 0.82) and 0.76 (95% CI = 0.71 to 0.82), respectively. CONCLUSIONS: Novice sonographers can identify sonographic B-lines with similar accuracy compared to an expert sonographer. Lung US has fair predictive value for pulmonary edema from acute heart failure in the hands of both novice and expert sonographers.

Identification of Sonographic B-lines with Linear Transducer Predicts Elevated B-Type Natriuretic Peptide Level.

OBJECTIVE: This study sought to correlate the presence of pleural-based B-lines seen by emergency department ultrasound performed with the linear transducer with B-type natriuretic peptide (BNP) level in patients with suspected congestive heart failure. METHODS: The study was a prospective convenience sample on adult patients in an academic, urban emergency department with over 100,000 annual patient visits. Adult patients with a BNP level ordered by the treating physician were prospectively enrolled by one of four physicians, blinded to the BNP level. The enrolling physicians included an emergency ultrasound director, two emergency ultrasound fellows, and a senior emergency medicine resident. Bedside ultrasound was performed using a 3-12 MHz linear broadband transducer in four lung fields. The serum BNP level was correlated with bilateral B-lines, defined as three or more comet-tail artifacts arising from the pleural line extending to the far field without a decrease in intensity on the right and left thorax. RESULTS: Sixty three patients were consented and enrolled during a four-month period. Fifteen patients had the presence of bilateral B-lines. The median BNP in patients with bilateral B-lines was 1560 pg/mL (95% confidence interval (CI) 1141-3706 pg/mL), compared with 538 pg/mL (95% confidence interval 310-1917 pg/mL) in patients without B-lines. The distributions in the two groups differed significantly (p=0.0006). Based on the threshold level of BNP 500 pg/mL, the sensitivity of finding bilateral B-lines on ultrasound was 33.3% (95% CI: 0.19-0.50), and the specificity was 91.7% (95% CI: 0.73-0.99). In addition, bilateral B-lines were absent in all patients with a BNP<100 pg/mL. CONCLUSION: The presence of bilateral B-lines identified with the linear probe is associated with significantly higher BNP levels than patients without B-lines. In our patient population, the presence of B-lines was specific but not sensitive for BNP>500. Further research may show that it can be applied to quickly assess patients with undifferentiated dyspnea.

Comparison of Metallic Foreign-Body Removal between Dynamic Ultrasound and Static Radiography in a Pigs' Feet Model.

INTRODUCTION: We compared the immediate cosmetic outcome of metallic foreign-body removal by emergency medicine (EM) residents with ultrasound guidance and conventional radiography. METHODS: This single-blinded, randomized, crossover study evaluated the ability of EM residents to remove metallic pins embedded in pigs' feet. Before the experiment, we embedded 1.5-cm metallic pins into numbered pigs' feet. We randomly assigned 14 EM residents to use either ultrasound or radiography to help remove the foreign body. Residents had minimal ultrasound experience. After a brief lecture, we provided residents with a scalpel, laceration kit, a bedside portable ultrasound machine, nipple markers, paper clips, a dedicated radiograph technician, and radiograph machine 20 feet away. After removal, 3 board-certified emergency physicians, who were blinded to the study group, evaluated the soft-tissue model by using a standardized form. They recorded incision length and cosmetic appearance on the Visual Analog Scale. RESULTS: In total, 28 foreign bodies were removed. No significant difference in the time of removal (P = 0.12), cosmetic appearance (P = 0.96), or incision length (P = 0.76) was found. CONCLUSION: This study showed no difference between bedside ultrasound and radiography in assisting EM residents with metallic foreign-body removal from soft tissue. No significant difference was found in removal time or cosmetic outcome when comparing ultrasound with radiography.