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ARDMS September 16, 2011

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ARDMS September 16, 2011

مُساهمة من طرف د.عوض محمد الخضر في الأحد سبتمبر 18, 2011 3:51 am

Beside Ultrasound (US) May Clear Up Undifferentiated Hypotension Picture

Performing bedside ultrasound on emergency department (ED) patients with undifferentiated hypotension can reduce diagnostic uncertainty and have a clinically significant impact on more than half of cases, according to research from George Washington University (GWU) Medical Center.

In addition, the prospective study also found that bedside ultrasound could have a dramatic impact on the management of a small number of patients.

"A hypotension protocol is an optimal use of point-of-care ED ultrasound that exemplifies 'right time, right place,' " said Dr. Hamid Shokoohi of the GWU Department of Emergency Medicine.

Undifferentiated hypotension is a critical ED presentation, and patient management is directed toward narrowing the differential diagnosis. With early goal-directed therapy considered essential for an optimal outcome, bedside ultrasound has been proposed as a means to rapidly stratify competing diagnoses, according to Shokoohi.

Shokoohi presented his research findings during a presentation at the American Institute of Ultrasound in Medicine (AIUM) annual meeting earlier this year.

Aiming to validate previous studies exploring the use of ultrasound on ED patients with undifferentiated hypotension, the study team set out to assess a bedside ultrasound protocol on management, examining its impact on improvement in diagnostic certainty, its ability to identify definitive and unexpected findings, and the concordance between ultrasound findings and final diagnosis.

The GWU researchers prospectively evaluated a convenience sample of 72 patients at GWU Medical Center with undifferentiated hypotension. All patients were more than 18 years old and had systolic blood pressure less than 90 mm Hg and no known source of hypotension.

Emergency medicine attending physicians were surveyed after an initial clinical evaluation of the patient, and goal-directed ultrasound was then performed using a M-Turbo compact-ultrasound scan by credentialed emergency sonologists not directly involved with patient care.

A standard ultrasound protocol for hypotension was employed, including a cardiac study (encompassing ejection fraction estimation, right ventricular [RV] dilation, and the presence or absence of pericardial effusion and tamponade), inferior vena cava (IVC) diameter measurement, a FAST (focused assessment with sonography for trauma) exam, an aorta scan (to check for abdominal aortic aneurysm), and a thoracic study (to detect pneumothorax).

After receiving the ultrasound results, the emergency medicine attending who evaluated the patient was surveyed again. The pre- and post-test questionnaire given to the attendings included a certainty matrix for estimated diagnostic certainty in six categories of hypotension etiologies: sepsis, cardiogenic, pericardial effusion, pulmonary embolism, hypovolemia/bleeding, and other. Certainty range choices included 0% to 25%, 25% to 50%, 50% to 75%, and 75% to 100%.

Physicians were also asked questions on how ultrasound affected management parameters, the need for further testing, the need for consultations in the ED, and how ultrasound changed the disposition of the patient in the ED.

The researchers have focused their initial data analysis on the main outcome of measuring the impact of the ultrasound protocol on the attending's diagnostic certainty. Using a tool to quantify diagnostic uncertainty derived from Shannon Information Theory, this method quantifies uncertainty by creating a summation score of diagnosis, with each diagnosis in the differential treated as a "bit" of information, Shokoohi said.

Changes in the summation scores were noted before and after the ultrasound protocol. Decreased uncertainty was interpreted as enhanced decision-making in diagnosis and treatment.

Bedside ultrasound reduced diagnostic uncertainty (as measured by the summation scores) from a mean of 1.77 to 1.51 (95% confidence interval [CI]: -0.13 to -0.38). The difference was statistically significant.

In 37 (51%) of 72 patients, ultrasound had a clinically significant impact, as determined by two or more quartile changes in physicians' perception of likelihood of diagnosis following ultrasound. Ultrasound also led to a significant increase in the absolute proportion of patients with a definitive diagnosis, climbing from 5.6% to 16.7% [95% CI: 1.0% to 21.2%].

In other findings, Shokoohi reported that ultrasound found abnormal IVC diameter in 46% of patients, abnormal ejection fraction in 36%, RV dilation in 14%, peritoneal and pleural free fluid in 13%, pericardial effusion in 8%, tamponade in 1.4%, and abdominal aortic aneurysm in 1.4%. No pneumothorax cases were found.

While ultrasound did not have a clinically significant impact in 49% of patients, Shokoohi noted that in a small number of cases, ultrasound yielded dramatic changes in diagnosis and management.

"In this minority of cases, you find the diagnosis [with ultrasound] that none of us can afford to miss," Shokoohi said.

View the article online.

Article written by staff at auntminnie.com, and adapted for the purposes of this newsletter.

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New Infant Urinary Tract Infection (UTI) Guideline Includes Ultrasound

Updated guidelines from the American Academy of Pediatrics (AAP) recommend urinalysis and culture when a urinary tract infection (UTI) is suspected or when antibiotic treatment will be started empirically in children 2-24 months.

Changes from the previous guidelines in 1999 include one specific to the first UTI: the new guidelines recommend renal and bladder ultrasound with no voiding cystourethrogram (VCUG) unless the ultrasound is suggestive of anatomic abnormalities, and follow-up but no antimicrobial prophylaxis.

Urine culture should show the presence of at least 50,000 colony-forming units (CFUs) per mL of a single uropathogen to confirm clinical suspicion arising from pyuria, positive nitrates, or bacteriuria.
Whenever possible, the urine specimen should be obtained by catheterization or suprapubic aspiration, as bag-collected specimens are unreliable. Preliminary diagnosis by bag-collected specimens should be confirmed by one of the other methods, members of an AAP committee on UTIs recommended.

Follow-up without urinalysis is sufficient for patients with a clinically low risk for UTI, as discussed in a clinical practice guideline published online in Pediatrics.

"This clinical practice guideline is not intended to be a sole source of guidance for the treatment of febrile infants with UTIs," Kenneth B. Roberts, MD, of the University of North Carolina in Chapel Hill, and coauthors of the guideline wrote in a summation.

"Rather, it is intended to assist clinicians in decision-making. It is not intended to replace clinical judgment or to establish an exclusive protocol for the care of all children with this condition."

Limited to children ages 2 to 24 months with a first UTI, the guideline comprises seven "action statements" that address the entire process of diagnosis and management of the condition. The first statement recommends urinalysis for an infant with fever of unknown origin and for whom immediate antimicrobial therapy is considered.

The second statement outlines two possible courses of action, depending on clinical impression. If a physician considers an infant at low risk for UTI, follow-up without testing is appropriate. The 1999 guideline did not include an option for follow-up without urinalysis and culture.

Urinalysis should be pursued if an infant has high-risk characteristics, such as female sex (odds ratio 2.27 versus boys) or male sex and uncircumcised (OR 4 to 20 times that of circumcised infants). The presence of another obvious source of infection reduces the risk of UTI by 50%.

The third statement outlines recommendations for obtaining urine specimens and performing urinalysis and culture to confirm a clinical diagnosis.

The recommendation regarding therapy has two parts. The first notes that oral and parental antibiotics are equally efficacious. The choice of a specific drug depends on local antimicrobial sensitivity patterns. Secondly, treatment should continue for seven to 14 days.

Febrile infants with laboratory-confirmed UTIs should have renal and bladder ultrasound to determine whether the patient has anatomic abnormalities, although the committee acknowledges that the diagnostic yield is low. However, ultrasonography can provide a baseline for assessing renal growth in an infant.

The 1999 guideline recommended imaging only when children did not respond within two days to antimicrobial therapy.

The committee recommends against routine VCUG after a first febrile UTI. VCUG is indicated when ultrasound reveals scarring, hydronephrosis, or other abnormalities that suggest high-grade vesicoureteral reflux or an obstruction.

VCUG also is warranted for evaluation of recurrent UTI.

Finally, the UTI committee members recommend that clinicians advise parents or guardians to seek medical evaluation of children within 48 hours if febrile illness persists or recurs. Prompt action is essential for early detection and treatment of recurrent infection.

View the article online.
Article written by staff at medpagetoday.com and adapted for the purposes of this newsletter.

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Guide Describes Ultrasound Use in Emergencies for Brain Disorders

The discovery that low-intensity, pulsed ultrasound can be used to noninvasively stimulate intact brain circuits holds promise for engineering rapid-response medical devices. The team that made that discovery, led by William "Jamie" Tyler, an assistant professor with the Virginia Tech Carilion Research Institute, has now produced an in-depth article detailing this approach, which may one day lead to first-line therapies in combating life-threatening epileptic seizures.

Status epilepticus is a condition in which the brain is in a state of persistent seizure and which, if not halted, can lead to Sudden Unexplained Death in Epilepsy (SUDEP). But, as the recent article by Tyler and 8 shows, ultrasonic neuromodulation does not necessarily need to be focused to attenuate epileptic seizures, meaning that it can be quickly applied in neurocritical care situations.

"Imagine a device like an automatic external defibrillator except for the brain," said first author Yusuf Tufail, who is now a postdoctoral associate at the Salk Institute for Biological Sciences.

Published in the September issue of Nature Protocols, the article, "Ultrasonic Neuromodulation by Brain Stimulation with Transcranial Ultrasound," provides a guide for the further development and clinical application of ultrasonic neuromodulation. The authors - Yusuf Tufail, Anna Yoshihiro, and Monica M. Li of Arizona State University's School of Life Sciences; Sandipan Pati of Barrow Neurological Institute at St. Joseph's Hospital and Medical Center in Phoenix, Ariz.; and corresponding author Tyler - also published their earlier research into the feasibility of this approach in Neuron.

Ultrasound is an acoustic wave occurring at frequencies exceeding the range of human hearing. Uses range from food processing to communication and include medical imaging. Tyler and his research group have spent several years developing noninvasive methods for brain stimulation employing low-intensity, low-frequency (LILFU) ultrasound. "Much of our time had been spent on understanding the biological effects of LILFU on intact brain circuits and how to control neural activity using LILFU," Tyler said.

The team has observed that the mechanical bioeffects of ultrasound are indeed capable of stimulating neuronal activity, meaning that ultrasound could join other therapies for neurological disorders - namely, implanted electrodes, such as those used in deep-brain stimulation, and external magnetic stimulators used for transcranial magnetic stimulation to treat disorders such as Parkinson's disease, major depression, and dystonia. The major advantage of using ultrasound for brain stimulation is that it can confer spatial resolution at millimeter precision while being focused through the skull to deep-brain regions without the need for invasive brain surgery, Tyler said.

"We have also shown that ultrasound can be used to stimulate synaptic transmission between groups of neurons within the brain in a manner similar to conventional implanted stimulating electrodes without generating significant heating of the brain tissue," said Tyler.

"Further studies are required to fully elucidate the many potential mechanisms underlying the ability of ultrasound to stimulate neuronal activity in the intact brain," the article stated. However, while using ultrasound for brain stimulation represents a powerful new tool for clinical neuroscience, there are potential concerns, since high-intensity ultrasound is also capable of destroying biological tissues, the researchers wrote.

The article reports that ultrasound has been used for many hours across many weeks, "stimulating cellular circuits in the living brain without producing damage in mice as assessed with cellular, histological, ultrastructural, and behavioral methods." The researchers added a note of caution: "Additional investigations across animal species and dosage levels are required, however, before the safety can be fully ascertained."

Moving this technology forward will require scientists, engineers, and physicians spanning many disciplines. The impetus for the Nature Protocols article is to disseminate basic methods for conducting ultrasonic neuromodulation. "There is a major need for increased open communication among engineers designing ultrasound-based medical devices, neuroscientists studying the core biological effects of ultrasound, and clinicians implementing ultrasound for therapeutic interventions," said Tyler.

The Nature Protocols article poses specific questions needing to be addressed, such as how ultrasound affects neurons on a molecular and cellular level, how to correct for impedance mismatches between skin and skull interfaces, and the need for characterizing safety across different exposure times, applications, and disease states.

The research reported in the article provides the provocative demonstration that ultrasonic neuromodulation is capable of attenuating seizure activity during pharmacologically induced status epilepticus in rodents. "While other research groups have reported that focused ultrasound can modulate seizure activity in the brain, the approaches used in those earlier studies require timely preparations and the implementation of MRI to focus the ultrasound in an approach known as magnetic resonance-guided focused ultrasound," said Tyler. "Our findings show that clinicians may not need to take such complicated, costly, and time-consuming approaches to treating patients in critical situations."

_________________
اللهم أجعل خير عمري آخره،وخير أعمالي خواتمها،وخيرأيامي يوم ألقاك
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د.عوض محمد الخضر
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