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Thứ Hai, 19 tháng 1, 2015

HEPATIC HEMODYNAMICS DURING VALSALVA MANEUVER




The Valsalva maneuver is a widely used physiologic technique for the non-invasive evaluation of heart murmurs and ventricular function [1-3]. The Valsalva maneuver consists of forceful expiration against a closed glottis, resulting in an increase in both intra-thoracic and intra-abdominal pressure, and activation of autonomic nervous function [4-6]. Although the hemodynamic changes during Valsalva maneuver have been well documented, these have been focused on cardiac chambers, aorta and systemic large veins [4,7-10]. Anatomically, venous return consists of systemic and hepatic venous return, and systemic venous return decreased markedly during the Valsalva maneuver [8,11]. However, it was not well defined that hemodynamic changes focused on the liver during Valsalva maneuver.
Clinically, the Valsalva maneuver is considered as main cause of defecation syncope and surgery Hepatic hemodynamics during Valsalva maneuver performed in a patient with functional suprahepatic inferior vana cava (IVC) obstruction during the Valsalva maneuver [12]. Collapsed IVC showed during the maneuver in normal healthy subjects using ultrasonography study, but IVC howed angular appearance and not collapsed during the maneuver in the venography study [10,11]. The change of IVC during the maneuver is ambiguous and hemodynamic contribution of hepatic vein and portal vein during the maneuver has not been studied in normal healthy subjects. Duplex Doppler ultrasonography of the liver provides important information about liver condition [11,13]. Hepatic vein flow depends on hepatic parenchymal compliance, thoracoabdominal pressure, and right atrial pressure. It is known that hepatic vein Doppler waveform is triphasic pattern which is composed of two anterograde flow peaks toward the heart and one retrograde flow peak toward the liver in healthy subjects [14]. Recently, volume flow measurement has been used for quantification of blood flow and it showed good correlation with magnetic resonance in quantification of cerebral blood flow [15-17]. Therefore, analysis of flow pattern and quantification of liver flow can be helpful to understand liver
condition under the Valsalva maneuver. Even the liver hemodynamic changes during the Valsalva maneuver in healthy volunteers have been studied in previous reports, its contribution to venous return is not focused enough [18,19]. We hypothesized that the hepatic circulation might be an important role to maintain venous return to the heart during Valsalva maneuver.

The aim of our study was to assess the hemodynamic change of liver including hepatic vein and portal vein during the Valsalva maneuver.





Thứ Tư, 14 tháng 1, 2015

B-mode ultrasound spots subclinical atherosclerosis

B-mode ultrasound spots subclinical atherosclerosis
By Erik L. Ridley, AuntMinnie staff writer
January 13, 2015 -- Thanks to advances in automation and improved imaging capabilities, B-mode ultrasound can be used to assess subclinical atherosclerotic disease and better identify those patients who would benefit from medical intervention prior to symptom onset, according to research published in Global Heart.

For the study, a multi-institutional, multinational research team examined two cohorts from India with automated B-mode ultrasound and compared the results with those of two cohorts from North America. Automated ultrasound of the carotid and iliofemoral arteries could feasibly provide rapid screening for subclinical atherosclerotic disease in a range of settings, the researchers found.
They also concluded that adding B-mode examination of the iliofemoral arterial beds to carotid ultrasound screening identifies additional subjects who would benefit from prophylactic medical intervention for atherosclerotic cardiovascular disease (ASCVD)-related events.
"Surely, such a simple approach merits adoption on a wide scale as a modern approach to a modern scourge of rapidly rising ASCVD-related events worldwide," wrote the authors, led by Ram Bedi, PhD, of the University of Washington's department of bioengineering, and senior author Dr. Jagat Narula, PhD, from Icahn School of Medicine.
Asymptomatic subjects
Doppler-based ultrasound systems are commonly used to assess carotid stenosis in symptomatic patients to identify those who would benefit from surgical intervention. The researchers believed that recent image quality improvements and advances in automation could enable B-mode systems to be similarly used for assessing subclinical atherosclerosis in the asymptomatic population to determine subjects who would benefit from prophylactic medical intervention (Global Heart, December 2014, Vol. 9:4, pp. 367-378).
To test their theory, the researchers used B-mode ultrasound to calculate the prevalence of atherosclerotic disease in 941 asymptomatic volunteers (mean age, 44.27 ± 13.76 years) from two underserved communities in India where ASCVD risk factor information was unknown. While one community was from an urban city (Jaipur), the other community -- from the semiurban town of Sirsa -- consisted of devout followers of a local spiritual leader, and the subjects had undergone aggressive lifestyle changes.
The results were compared with reference data gathered from two primary care clinics in North America: one was in Toronto, and the other was in Richmond, TX. The 481 subjects in this part of the study had a mean age of 59.68 ± 11.95 years; most were office workers in mid- to high-income brackets and few engaged in regular physical activity, according to the researchers.
Automated bilateral B-mode ultrasound studies of the carotid and iliofemoral arteries were performed at two health camps in India, using a CardioHealth Station (Panasonic Healthcare) ultrasound system, by one of eight radiology residents. The residents did not have prior experience in vascular ultrasound but received two hours of training. Ultrasound exams were performed by trained vascular sonographers at the two North American clinics in the study.
While conventional 2D imaging was considered satisfactory for identifying focal lesions, 3D imaging data for the arterial segment of interest were acquired to automate the process of plaque identification and quantification. To present the clinical findings in an easy-to-understand manner, the researchers developed an index called the Fuster-Narula (FUN) score, which summarizes the intima-media volume for the scanned peripheral arteries.

The researchers found that 224 (24%) of the participants from India had plaque in at least one of the four arterial sites. Furthermore, 107 (11%) had plaque only in the carotid arteries, 70 (7%) had plaque in both the carotid and iliofemoral arteries, and 47 (5%) had plaque only in the iliofemoral arteries. The presence of plaque was associated with older age and the male gender, but not with systolic blood pressure, the group noted.

Thứ Bảy, 3 tháng 1, 2015

ULTRASOUND IMPLEMENTATION on LEARNING and TEACHING for the 1st Year of Medical Education




Discussion

We found that the introduction of a pilot ultrasound curriculum integrated with the physical diagnosis course at our institution did not worsen year 1 medical student physical examination skills and may be potentially beneficial when compared to historic controls. Students who had the ultrasound curriculum had better overall associated OSCE scores compared to students in the historic control group.
Students and faculty predominantly had positive responses to the course, and most agreed or strongly agreed that ultrasound has a valuable role in medical education. Faculty gave constructive feedback on how to improve ultrasound implementation. Other studies have shown that point-of-care ultrasound training can enhance ultrasound skills and specific physical examination skills such as abdominal and cardiac examinations.18,26 We believe that no previous study has shown that implementation of a point-of-care ultrasound curriculum in the year 1 medical student curriculum may have substantial benefits to the overall traditional physical examination.
Previous work has shown that ultrasound curricula for medical students and residents, during their respective training, can improve their ultrasound skills20,26–31 when compared to control groups without ultrasound training.6,32,33 It inherently makes sense that learners who are taught any skill should outperform learners who are naive to that skill. Specific physical examination skills have also been shown to improve with introduction of ultrasound training.
One study found that ultrasound improves year 1 medical students’ abdominal examination.17 However, only the abdominal examination was assessed in that study. Other studies have shown that medical students could more accurately diagnose cardiac diseases using ultrasound even when compared to a trained cardiologist using auscultation alone.32–34 Most of these studies used ultrasound defined end points; hence, the effect of ultrasound on traditional physical examination skills remained unknown.
By not using any ultrasound end points, our study was unique in demonstrating that year 1 medical students with point-of-care ultrasound training had improved overall traditional OSCE scores and a trend toward improved physical examination skills in almost all organ systems when compared to students with no point-of-care ultrasound training. This finding suggests that point-of-care ultrasound does not worsen the overall physical examination skills of year 1 medical students but may actually improve their physical examination skills. The concern that technology may impede critical thinking and tactile skills is a valid point.21–24,35 The purpose of point-of-care ultrasound must be differentiated from the use of CT, MRI, and comprehensive
ultrasound scans. In point-of-care ultrasound,the clinical sonographer is the actual practitioner with a focused question regarding the patient being treated. The goal of point-of-care ultrasound would be to confirm or refute a diagnosis as a result of the practitioner’s physical examination.36 Point-of-care ultrasound may actually promote critical thinking because the sonographer knows what condition is of concern before performing the ultrasound examination rather than haphazardly performing an ultrasound examination looking for incidental findings, as may occur with CT, MRI, and comprehensive ultrasound examinations.

Ultrasound curriculum implementation into medical schools has been shown to be feasible.1–7,37 However,many of these institutions have ample point-of-care ultrasound faculty experts and considerable industry support for numerous ultrasound machines. We piloted a curriculum with minimal resources, using only 4 ultrasound machines, 1 point-of-care ultrasound expert, and 8 ultrasound-naïve faculty to train a group of 163 year 1 medical students. We found that it was feasible to implement this curriculum through faculty development and student peer teaching. Another concern is the addition of time for ultrasound training into medical students’ already demanding schedules.
Incorporating ultrasound directly into the required physical diagnosis course obviated the need to add more time to the overall students’ curriculum. Furthermore, having open ultrasound lab sessions allowed students to practice their physical examination and ultrasound skills on their own. Given the limited availability of point-of-care ultrasound experts an institution may have, we believe that most schools will need to use ultrasound-naive faculty members for ultrasound curriculum implementation. The feedback from the faculty members in this study raises many important points when implementing an ultrasound curriculum.
Dedicated faculty development must be performed on a longitudinal basis, so faculty will feel comfortable with the basic ultrasound skills. Some faculty members may have years of clinical experience but might not see the direct benefits of point-of-care ultrasound if they do not use it in their own clinical practice. However, with more residencies requiring ultrasound competency for residency completion,8–11 medical students with comprehensive ultrasound training may have a considerable advantage when they enter residency training. Previous studies have shown that medical students and residents already have a strong interest in ultrasound and believe it is important to their medical training.4,38,39 The importance of this emerging technology should also be emphasized to all faculty involved with ultrasound teaching.40,41
We realize that integration of ultrasound is difficult because each school has a unique curriculum that has been in place for many years. An additional problem with ultrasound is that it can be a substantial financial burden to administrators and requires added student time and faculty commitment. Another concern may be that most schools may not have an ultrasound expert to adequately implement a curriculum.We found that a curriculum can be feasibly developed with minimal resources. Students in our study strongly agreed that peer teaching was useful for learning point-of-care ultrasound. Peer teaching has also been used successfully at other institutions.42-44 Further research needs to be done on the barriers to ultrasound implementation in medical schools and how implementation can be facilitated with limited resources.
There were several limitations to our study. The control group was a historic control, and the students from both groups may have been inherently different, which could have caused the difference in OSCE scores. There were no notable curriculum or faculty changes between the 2 years, except for the point-of-care ultrasound implementation.
Twenty-five student data points were missing from the historic controls, which may have affected the mean pre-ultrasound group scores. This study could have been improved if the groups were randomized, but we thought that all students would benefit from the ultrasound curriculum. There is no current recommended standardized curriculum, and the ultrasound curriculum we implemented may have had different results if we had more intense ultrasound training for students and faculty. The effect of ultrasound training on medical student proficiency in the clinical setting needs further investigation.

We conclude that implementing an ultrasound curriculum into a physical diagnosis course is feasible with limited resources and may increase the physical examination skills of year 1 medical students. Overall, students and faculty had a positive response to the ultrasound curriculum. Despite the controversy that introducing ultrasound may decrease time for learning traditional physical examination skills and may cause reliance on such technology, our study found that by using ultrasound synergistically to learn the physical examination, there seems to be an overall benefit to the introduction of ultrasound into medical education.

Dinh et al—Ultrasound Effects on Physical Examination in Medical Education, J UltrasoundMed 2015; 34:43–50.