Heidi H. Kimberly

Correlation of Optic Nerve Sheath Diameter with Direct Measurement of Intracranial Pressure

BACKGROUND Measurements of the optic nerve sheath diameter (ONSD) using bedside ultrasound (US) have been shown to correlate with clinical and radiologic signs and symptoms of increased intracranial pressure (ICP). OBJECTIVES Previous literature has identified 5 mm as the ONSD measurement above which patients exhibit either clinical or radiologic signs of elevated ICP. The goals of this study were to evaluate the association between ONSD and ICP and to validate the commonly used ONSD threshold of 5 mm using direct measurements of ICP as measured by ventriculostomy. METHODS A prospective blinded observational study was performed using a convenience sample of adult patients in both the emergency department (ED) and the neurologic intensive care unit (ICU) who had invasive intracranial monitors placed as part of their clinical care. Ocular USs were performed with a 10(-5) MHz linear probe. Emergency physicians (EPs) with previous ocular US experience performed ONSD measurements while blinded to the contemporaneous ICP reading obtained directly from invasive monitoring. The association between ONSD and ICP was assessed with the Spearman rank correlation coefficient, and a receiver operator characteristic (ROC) curve was created to determine the optimal ONSD cutoff to detect ICP > 20 cm H2O. RESULTS Thirty-eight ocular USs were performed on 15 individual patients. Spearman rank correlation coefficient of ONSD and ICP was 0.59 (p < 0.0005) demonstrating a significant positive correlation. An ROC curve was created to assess the ability of ONSD to distinguish an abnormal ICP greater than 20 cm H2O. The area under the ROC curve was 0.93 (95% confidence interval [CI] = 0.84 to 0.99). Based on inspection of the ROC curve, ONSD > 5 mm performed well to detect ICP > 20 cm H(2)O with a sensitivity of 88% (95% CI = 47% to 99%) and specificity of 93% (95% CI = 78% to 99%). CONCLUSIONS Using an ROC curve the authors systematically confirmed the commonly used threshold of ONSD > 5 mm to detect ICP > 20 cm H2O. This study directly correlates ventriculostomy measurements of ICP with US ONSD measurements and provides further support for the use of ONSD measurements as a noninvasive test for elevated ICP.

Focused Maternal Ultrasound by Midwives in Rural Zambia

Point-of-care ultrasound is being increasingly implemented in resource-poor settings in an ad hoc fashion. We developed a focused maternal ultrasound-training program for midwives in a rural health district in Zambia. Four hundred forty-one scans were recorded by 21 midwives during the 6-month study period. In 74 scans (17%), the ultrasound findings prompted a change in clinical decision-making. Eight of the midwives were evaluated with a 14-question observed structured clinical examination (OSCE) and demonstrated a slight overall improvement with mean scores at 2 and 6 months of 10.0/14 (71%) and 11.6/14 (83%), respectively. Our pilot project demonstrates that midwives in rural Zambia can be trained to perform basic obstetric ultrasound and that it impacts clinical decision-making. Ultrasound skills were retained over the study period. More data is necessary to determine whether the introduction of ultrasound ultimately improves outcomes of pregnant women in rural Zambia.

Using MRI of the optic nerve sheath to detect elevated intracranial pressure

The current gold standard for the diagnosis of elevated intracranial pressure (ICP) remains invasive monitoring. Given that invasive monitoring is not always available or clinically feasible, there is growing interest in non-invasive methods of assessing ICP using diagnostic modalities such as ultrasound or magnetic resonance imaging (MRI). Increased ICP is transmitted through the cerebrospinal fluid surrounding the optic nerve, causing distention of the optic nerve sheath diameter (ONSD). In this issue of Critical Care, Geeraerts and colleagues describe a non-invasive method of diagnosing elevated ICP using MRI to measure the ONSD. They report a positive correlation between measurements of the ONSD on MRI and invasive ICP measurements. If the findings of this study can be replicated in larger populations, this technique may be a useful non-invasive screening test for elevated ICP in select populations.

Individual patient data systematic review and meta-analysis of optic nerve sheath diameter ultrasonography for detecting raised intracranial pressure: protocol of the ONSD research group

BackgroundThe purpose of the optic nerve sheath diameter (ONSD) research group project is to establish an individual patient-level database from high quality studies of ONSD ultrasonography for the detection of raised intracranial pressure (ICP), and to perform a systematic review and an individual patient data meta-analysis (IPDMA), which will provide a cutoff value to help physicians making decisions and encourage further research. Previous meta-analyses were able to assess the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP but failed to determine a precise cutoff value. Thus, the ONSD research group was founded to synthesize data from several recent studies on the subject and to provide evidence on the diagnostic accuracy of ONSD ultrasonography in detecting raised ICP.MethodsThis IPDMA will be conducted in different phases. First, we will systematically search for eligible studies. To be eligible, studies must have compared ONSD ultrasonography to invasive intracranial devices, the current reference standard for diagnosing raised ICP. Subsequently, we will assess the quality of studies included based on the QUADAS-2 tool, and then collect and validate individual patient data. The objectives of the primary analyses will be to assess the diagnostic accuracy of ONSD ultrasonography and to determine a precise cutoff value for detecting raised ICP. Secondly, we will construct a logistic regression model to assess whether patient and study characteristics influence diagnostic accuracy.DiscussionWe believe that this IPD MA will provide the most reliable basis for the assessment of diagnostic accuracy of ONSD ultrasonography for detecting raised ICP and to provide a cutoff value. We also hope that the creation of the ONSD research group will encourage further study.Systematic review registrationPROSPERO registration number: CRD42012003072

Real-time resolution of sonographic B-lines in a patient with pulmonary edema on continuous positive airway pressure

Sonographic B-lines of the lungs have been shown to be able to differentiate between congestive heart failure and chronic obstructive pulmonary disease. Studies have shown that B-lines are often present on presentation and resolve during the course of a hospitalization. What is not known is how quickly B-lines resolve in response to treatment. We describe a case of a patient who presented with pulmonary edema and had diffuse B-lines seen on bedside thoracic ultrasound. She was treated with continuous positive airway pressure only and, a few hours later, had no sonographic Blines. B-lines seen on bedside thoracic ultrasound resolve in real time when pulmonary edema is treated with continuous positive airway pressure. Research to further quantify the use of B-lines in monitoring response to treatment is needed. Thoracic ultrasound has been shown to be a useful way of evaluating patients with dyspnea. Specifically, the presence of diffuse sonographic B-lines is associated with fluid overload states such as pulmonary edema. Although studies have shown that B-lines can aid in the diagnosis of this condition, none have looked at their rate of resolution with treatment. We describe an interesting case of a patient in pulmonary edema whose B-lines resolve in real time when treated with continuous positive airway pressure (CPAP) only. An 82-year-old woman presented to the emergency department (ED) with dyspnea for 4 hours. She had a history of atrial fibrillation, congestive heart failure (CHF), end-stage renal disease, hypertension, and coronary artery disease. She was sitting on her couch in her usual state of health watching TV when she suddenly became short of breath. She had a mild nonproductive cough but denied fever, chest pain, or leg pain. She had been compliant with her medications and with hemodialysis sessions. She had been using 2 to 3 pillows to sleep at night for a while. She reported some intermittent leg swelling, which improves after dialysis. 0735-6757/

Pilot Point-of-Care Ultrasound Curriculum at Harvard Medical School: Early Experience

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Point-of-care ultrasonography for the diagnosis of small bowel obstruction in the emergency department

Introduction Point-of-care ultrasound (POCUS) is expanding across all medical specialties. As the benefits of US technology are becoming apparent, efforts to integrate US into pre-clinical medical education are growing. Our objective was to describe our process of integrating POCUS as an educational tool into the medical school curriculum and how such efforts are perceived by students. Methods This was a pilot study to introduce ultrasonography into the Harvard Medical School curriculum to first- and second-year medical students. Didactic and hands-on sessions were introduced to first-year students during gross anatomy and to second-year students in the physical exam course. Student-perceived attitudes, understanding, and knowledge of US, and its applications to learning the physical exam, were measured by a post-assessment survey. Results All first-year anatomy students (n=176) participated in small group hands-on US sessions. In the second-year physical diagnosis course, 38 students participated in four sessions. All students (91%) agreed or strongly agreed that additional US teaching should be incorporated throughout the four-year medical school curriculum. Conclusion POCUS can effectively be integrated into the existing medical school curriculum by using didactic and small group hands-on sessions. Medical students perceived US training as valuable in understanding human anatomy and in learning physical exam skills. This innovative program demonstrates US as an additional learning modality. Future goals include expanding on this work to incorporate US education into all four years of medical school.

POSITIVE FAST WITHOUT HEMOPERITONEUM DUE TO FLUID RESUSCITATION IN BLUNT TRAUMA

Small bowel obstruction (SBO) is a common cause of acute abdominal pain presenting to the emergency department (ED). Although the literature is limited, point-of-care ultrasonography (POCUS) has been found to have superior diagnostic accuracy for SBO compared to plain radiography; however, it is rarely used in North America for this. We present the case of a middle-aged man who presented with abdominal pain where POCUS by the emergency physician early in the hospital course expedited the diagnosis of SBO and led to earlier surgical consultation. The application of POCUS for SBO is easily learned and applied in the ED. POCUS for SBO may obviate the need for plain radiography and expedite patient care.

Point-of-Care Ultrasonography in a Domestic Mass Casualty Incident: The Boston Marathon Experience

BACKGROUND The focused assessment with sonography in trauma (FAST) examination is an important screening tool in the evaluation of blunt trauma patients. OBJECTIVES To describe a case of a hemodynamically unstable polytrauma patient with positive FAST due to fluid resuscitation after blunt trauma. CASE REPORT We describe a case of a hemodynamically unstable polytrauma patient who underwent massive volume resuscitation prior to transfer from a community hospital to a trauma center. On arrival at the receiving institution, the FAST examination was positive for free intraperitoneal fluid, but no hemoperitoneum or significant intra-abdominal injuries were found during laparotomy. In this case, it is postulated that transudative intraperitoneal fluid secondary to massive volume resuscitation resulted in a positive FAST examination. CONCLUSION This case highlights potential issues specific to resuscitated trauma patients with prolonged transport times. Further study is likely needed to assess what changes, if any, should be made in algorithms to address the effect of prior resuscitative efforts on the test characteristics of the FAST examination.

Personalized peer-comparison feedback and its effect on emergency medicine resident ultrasound scan numbers

Background: The role of Point-of-Care (POC) ultrasonography in domestic Mass Casualty Incidents (MCI) has not been well established. On April 15th, 2013, two improvised explosive devices were detonated near the finish line of the Boston Marathon injuring 264 patients and killing 3. These patients were rapidly stabilized and transported to Boston area hospitals. Objectives: To examine the role of POC ultrasonography during the Emergency Department response to a large-scale domestic MCI, and to identify successful processes as well as barriers to care delivery in order to best prepare for future events. Methods: An online survey containing multiple-choice and open-response questions was distributed to Emergency Medicine housestaff, physician assistants, fellows and attending physicians in the Boston area Emergency Departments who cared for patients during the Boston Marathon MCI. Results: There were 50 respondents from 6 hospitals who were directly involved with patient care. 23 respondents (46%) performed POC ultrasounds during the MCI, but only 8 of these respondents (35%) documented findings in the usual fashion by saving images including patients medical record numbers. Many respondents altered documentation patterns due to lack of patient information/registration data and to time constraints. Focused assessment with sonography in trauma (FAST) exams were reported as the most useful application (96%), followed by lung sliding (36%), and soft tissue/foreign body exams (18%). Respondents noted that POC ultrasound provided clinical information sooner then plain films and computed tomography (CT) scans, as these traditional imaging resources were significantly overwhelmed. Many described the value of POC ultrasound in resource allocation and triage once acute intra-abdominal and thoracic injuries had been excluded. Respondents reported being hindered by too few ultrasound systems or systems with long boot-up times and/or lack of battery power. Conclusions: Though limited by our retrospective survey-based methodology, our findings indicate that POC ultrasound was utilized in the hospital-based response to a large-scale domestic MCI. POC ultrasound was especially useful given delays in traditional imaging. Our findings highlight the difficulties with normal documentation patterns during such events, and suggest that specific planning for POC ultrasound should be incorporated into future MCI preparedness.