Seeing Bradycardia: How Ultrasound Improves Medical Decision-Making.

There is a broad differential for new-onset cardiac dysrhythmia, and the rapid identification of the underlying cause of these cardiac emergencies can be lifesaving. Identifying wall motion abnormalities on point-of-care ultrasound (POCUS) is not a core echocardiography application for Emergency Medicine (EM) physicians. However, ruling in a regional wall motion abnormality can expedite patient-centered care and assist the busy EM physician in high-risk cases.

Point of Care Ultrasounds Obtained by Novice Physician Assistant Residents (POCUS ON PAR).

INTRODUCTION: The integration of Point of Care Ultrasound (POCUS) into the care of trauma patients, specifically the E-FAST, has improved the accuracy of initial diagnoses and improved time to surgical intervention in critically ill patients. Physician assistants (PAs) are critically important members of any military trauma resuscitation team and are often team leaders in a pre-hospital setting. They may receive training in ultrasound but there are little data to support their use or evaluate their effectiveness in using POCUS. We designed a study to evaluate the image quality of an E-FAST Exam performed by Emergency Medicine Physician Assistant (EMPA) Fellows and Emergency Medicine (EM) Interns following identical training. Our hypothesis is that image quality obtained by EMPAs will be non-inferior to those images obtained by EM Interns. MATERIALS AND METHODS: This is a prospective single-blinded study comparing the image quality of E-FAST exams performed by first year EM interns and first year EMPA fellows. All participants completed standard POCUS training prior to enrollment in the study. A total of 8 EMPAs and 8 EM first year residents completed 10 recorded E-FAST exams to be used as study images. Participants also viewed a 15-question slide show containing images of positive (6) and negative (9) E-FAST exams and recorded their interpretations. Images were reviewed by expert reviewers who were blinded to which images were collected by which group. An image quality score was recorded for each view as well as an overall image quality score. Image quality was rated on a 1 to 5 image quality scale. RESULTS: For overall image quality, the mean score for EMPAs was 3.6 ± 0.5 and for EM residents was 3.2 ± 0.5 with statistical significance favoring better image quality from the EMPAs. The time to completion for the EFAST exam for EMPAs was 4.8 ± 1.3 minutes and for interns it was 3.4 ± 1.4 minutes (P value = 0.02). There was no difference in image interpretation quiz scores between the groups (mean score 92% among interns and 95% among PAs). CONCLUSIONS: POCUS is an imaging modality which is very portable and relatively inexpensive which makes it ideal for military medicine. PAs are essential members of military trauma teams, and often run an initial trauma resuscitation. Being able to correctly identify patients who have free fluid early in the course of treatment allows for more correct evacuation criteria to ensure the sickest patients get to care the fastest. Although there are limited data to support POCUS use by non-physicians, our data support a growing body of evidence that it is not the profession or baseline medical education that determines an individual's ability to use and incorporate ultrasound into bedside and clinical practice. Our study shows that with training and experience PAs or other members of the military health care team can use the EFAST to better care for trauma patients.

Comparing the Sensitivity of a Low Frequency Versus a High Frequency Probe in the Detection of Pneumothorax in a Swine Model.

BACKGROUND: Correct diagnosis of pneumothorax in trauma patients is essential. Under-diagnosis can lead to development of life-threatening tension pneumothorax, but overdiagnosis leads to placement of unnecessary chest tubes with potential related morbidity and pain. It is unclear from previous work if there is a benefit to switching from the phased array (low frequency) probe to the linear (high frequency) probe. Is the improvement in image quality worth the time lost changing probes? METHODS: We compared the sensitivity and specificity of a low frequency and high frequency ultrasound probe for the detection of pneumothorax. Images were obtained using swine models and were interpreted by Emergency Medicine residents, attendings, and physician assistants. RESULTS: We found a specificity of 89% and sensitivity of 99% for the low frequency probe and specificity of 96% and sensitivity of 99% for the high frequency probe. There was a statistically different specificity between the two probes, suggesting that the linear probe may be the superior probe for confirming the presence of pneumothorax. CONCLUSION: We conclude switching to the linear probe for the thoracic portion of the Extended-Focused Assessment in Trauma will lead to more accurate diagnosis of pneumothorax and decreased false-positive exams.

Ultrasound at the Role 1: An Analysis of After-Action Reviews from the Prehospital Trauma Registry.

BACKGROUND: Ultrasound is a portable and adaptable imaging modality used widely in the care of trauma patients. The initial exam, known as the "Focused Assessment in Trauma (FAST) exam focused on the evaluation for hemoperitoneum and hemopericardium. In recent years, the exam has expanded to include evaluate for thoracic pathology, including pneumothorax, and is now known as the "Extended Focused Assessment in Trauma" (E-FAST) exam. METHODS: We reviewed after-action reviews (AAR) from the Joint Trauma System Prehospital Trauma Registry from 2013-2014 in which the use of an ultrasound exam was noted. Given the largely unstructured nature of the AARs, we selected relevant information from the free text available. RESULTS: Our initial dataset contained 705 casualties, of which we identified 45 cases containing the key words with AAR data for review: 39 cases involved the use of the FAST exam, three explicitly described the use of pulmonary ultrasound and they were categorized as E-FAST exams, two cases described the use of point of care echo to evaluate for cardiac standstill, and two cases described the use of ultrasound to evaluate for vascular injury. Of those with vital signs documented, 25% (11) reported at least one episode of tachycardia (≥120/min) and 16% (7) with at least one episode of systolic hypotension (less than 90mmHg). Of the 45 cases reviewed, six were recorded as equivocal, which we interpreted to indicate more training in either performance or interpretation of the exam was needed. CONCLUSIONS: Our findings suggest that training in both the FAST exam and E-FAST has the potential to improve patient care for military trauma patients. A performance improvement system would enable real-time confirmation of findings and feedback for training and quality improvement.

Role of heat shock protein 90 and endothelial nitric oxide synthase during early anesthetic and ischemic preconditioning.

BACKGROUND: Nitric oxide is known to be essential for early anesthetic preconditioning (APC) and ischemic preconditioning (IPC) of myocardium. Heat shock protein 90 (Hsp90) regulates endothelial nitric oxide synthase (eNOS) activity. In this study, the authors tested the hypothesis that Hsp90-eNOS interactions modulate APC and IPC. METHODS: Myocardial infarct size was measured in rabbits after coronary occlusion and reperfusion in the absence or presence of preconditioning within 30 min of isoflurane (APC) or 5 min of coronary artery occlusion (IPC), and with or without pretreatment with geldanamycin or radicicol, two chemically distinct Hsp90 inhibitors, or N-nitro-L-arginine methyl ester, a nonspecific nitric oxide synthase NOS inhibitor. Isoflurane-dependent nitric oxide production was measured (ozone chemiluminescence) in human coronary artery endothelial cells or mouse cardiomyocytes, in the absence or presence of Hsp90 inhibitors or N-nitro-L-arginine methyl ester. Interactions between Hsp90 and eNOS, and eNOS activation, were assessed with immunoprecipitation, immunoblotting, and confocal microscopy. RESULTS: APC and IPC decreased infarct size (by 50% and 59%, respectively), and this action was abolished by Hsp90 inhibitors. N-nitro-L-arginine methyl ester blocked APC but not IPC. Isoflurane increased nitric oxide production in human coronary artery endothelial cells concomitantly with an increase in Hsp90-eNOS interaction (immunoprecipitation, immunoblotting, and immunohistochemistry). Pretreatment with Hsp90 inhibitors abolished isoflurane-dependent nitric oxide production and decreased Hsp90-eNOS interactions. Isoflurane did not increase nitric oxide production in mouse cardiomyocytes, and eNOS was below the level of detection. CONCLUSION: The results indicate that Hsp90 plays a critical role in mediating APC and IPC through protein-protein interactions, and suggest that endothelial cells are important contributors to nitric oxide-mediated signaling during APC.