Learning Objectives: After reading this article, the physician should be better able to:
1. Describe the clinical findings, including the measurement of pulsus paradoxus, to confirm or exclude the diagnosis of cardiac tamponade in patients with known or suspected pericardial effusion.
2. Explain the importance of screening at-risk patients for renal dysfunction prior to IV contrast administration and using IV fluids to reduce the incidence of contrast-induced nephropathy.
3. Summarize how emergency department point-of-care limited ultrasound is associated with more rapid care and lower costs in patients with chest and abdominal trauma.
Release Date: November 2009
Article from the 2009 LLSA Reading List
Does This Patient With a Pericardial Effusion Have Cardiac Tamponade?
Roy CL, et al
Cardiac tamponade is a true life-threatening emergency that fortunately is uncommon in the emergency department. Treatment with pericardiocentesis can be lifesaving, but the procedure is one that must be done with great caution, usually by a cardiologist. Emergency physicians must make the diagnosis early so expert help can be summoned before the patient deteriorates. The authors of this paper searched MEDLINE for clinical variables to the final diagnosis of cardiac tamponade, and then synthesized the data from those articles to characterize if those variables predicted tamponade.
Among patients with a cardiac tamponade diagnosis confirmed by echocardiography or invasive pressure measurement, five clinical findings were present in more than half: cardiomegaly on chest x-ray (89%), dyspnea (88%), pulsus paradoxus >10 mm Hg (82%), tachycardia (77%), and elevated jugular venous pressure (76%).
Given the sensitivity of these findings, the lack of all five in a patient with a pericardial effusion makes diagnosing tamponade highly unlikely. Of note, classic findings such as hypotension and muffled heart sounds (two of the components of Beck's triad), or EKG changes such as electrical alternans or low-QRS-voltage, were found in only a minority of patients, limiting their usefulness as screening tools.
The clinical test most effective in diagnosing tamponade is elevated pulsus paradoxus, an exaggeration of the drop in systolic blood pressure during inspiration, implying impairment of left-sided chamber filling. This can be measured at the bedside with a manual blood pressure cuff, a very slow rate of cuff deflation, and careful auscultation of Korotkoff sounds with attention to the respiratory cycle. In one study, an elevated pulsus paradoxus (>10 mm Hg) with pericardial effusion conferred roughly three times the risk of tamponade (+LR 3.3). Pericardial tamponade with a normal pulsus paradoxus (<10 mm Hg) is very unlikely (–LR 0.03).
Patients with suspected cardiac tamponade should be asked about dyspnea, evaluated for tachycardia or elevated jugular venous pressure (JVP), and have a chest x-ray and EKG performed. If available, a bedside ultrasound may confirm the presence of an effusion. In patients with a known or suspected effusion, pulsus paradoxus should be measured. Patients with elevated pulsus paradoxus or any signs of hemodynamic collapse should have immediate echocardiography and possibly pericardiocentesis.
Article from the 2008 LLSA Reading List
Preventing Nephropathy Induced by Contrast Medium
Barrett BJ, et al
N Engl J Med
The use of iodinated contrast material is increasing throughout the health care system, particularly in hospitals and emergency departments. Emergency physicians routinely order CT scans and CT angiograms requiring IV contrast, and also occasionally refer patients for emergent angiography performed by a cardiologist or radiologist. The incidence of diabetes, hypertension, and chronic kidney disease are also increasing, and a substantial portion of patients are unaware of their disease. The intersection of these two trends is a heightened risk of contrast-induced nephropathy, already the third most common cause of renal failure in hospitalized patients. The authors of this review summarize the risk factors and possible prophylactic therapies for nephropathy induced by contrast.
Risk factors for contrast-induced nephropathy include age over 75, diabetes mellitus, hypertension, heart failure, cirrhosis, volume depletion, NSAID use, and pre-existing renal disease. The route (intra-arterial vs. intravenous) and dose of contrast administration help determine the risk of nephropathy. Overall, up to 15 percent of patients receiving injected contrast have a 25 percent or greater increase in creatinine levels, with up to one percent overall requiring dialysis at least once. In the highest risk group of patients, 12 percent undergo dialysis as a result of contrast-induced nephropathy.
The authors recommend that patients who have any of these risk factors or who are to receive intra-arterial contrast should have measurement of serum creatinine and estimation of glomerular filtration rate (GFR) done prior to contrast administration. In patients whose GFR is estimated to be less than 50 ml/min/1.73 m2, alternative diagnostic strategies or lower doses of contrast should be employed if possible. If the use of injected contrast is unavoidable in such patients, tell the patient of the risk and take steps to attempt prophylaxis against nephropathy.
Multiple strategies for preventing contrast-induced nephropathy in patients with underlying kidney disease (GFR <50 ml/min.) have been proposed and studied. The authors discuss the most commonly employed and well-studied.
Intravenous fluids, infused for 24 hours peri-procedurally, have been shown to be superior to oral fluids alone or oral fluids with one bolus of IV fluid. The recommended regimen is 1 mL of normal saline per kilogram of body weight per hour for 24 hours, starting at least two hours prior to the procedure if possible.
N-acetylcysteine (NAC) has been studied extensively, with conflicting results. The authors do not recommend its routine use for patients at risk of contrast-induced nephropathy, but early trials showed a substantial prophylactic benefit so this agent has been used in clinical practice for several years. The dosage typically used is 600 mg by mouth every 12 hours for four doses, with the first dose administered up to 12 hours prior to the procedure.
Other approaches to prophylaxis such as diuretics, vasodilators, antioxidants, and prophylactic hemofiltration or hemodialysis have been studied, but do not have adequate evidence to support their use at this time.
As most of the prophylactic strategies described require pre-treatment, the primary strategy for the emergency physician in preventing contrast-induced nephropathy is in screening for underlying kidney disease and avoiding or reducing contrast use in susceptible patients. If the use of injectable contrast is unavoidable in a patient with an estimated GFR <50 ml/min, the lowest dose of low-osmolality contrast should be used, and the patient should receive IV normal saline at 1 ml/kg/hour as soon as possible. Patients should receive IV fluid for 24 hours and creatinine measurements for 48 hours in the hospital. The use of N-acetylcysteine is unlikely to be of benefit in this situation.
Article from the 2008 LLSA Reading List
Randomized Controlled Clinical Trial of Point-of-Care, Limited Ultrasonography for Trauma in the Emergency Department: The First Sonography Outcomes Assessment Program Trial
Melniker LA, et al
Ann Emerg Med
Traumatic injury accounts for more than 38 million U.S. ED visits each year, with five million cases involving significant trauma to the torso. Chest and abdominal trauma results in more than 500,000 operations and 50,000 deaths per year. Its predilection for the young makes it the leading cause of death in those under 45 and results in $100 billion lost annually to society. A major advance in the ED assessment of torso trauma has been the use of ultrasound to perform focused assessment with sonography for trauma (FAST) exams to screen for significant injury. In this randomized, nonblinded, dual-center trial, the authors describe the benefit of FAST exams for patients with torso trauma.
Over six months, 527 patients with torso trauma were evaluated at the two Level I trauma centers participating in the study. After excluding those requiring immediate operations and those who could not give or refused consent, 444 were randomized to receive either usual care or usual care with point-of-care, limited ultrasonography (PLUS). In the PLUS group, the clinician certified for sonography performed a FAST exam during the initial ED evaluation of the patient, using the usual technique of visualizing the pericardial space, right upper quadrant, left upper quadrant, and pelvis. Results were immediately available to those involved in the patient's care; no blinding took place. Patients were followed throughout hospitalization and assessed for several key outcome measures.
Overall, 80 percent of enrolled patients were admitted to the hospital, with 29 percent requiring one or more operations. Injury severity scores, revised trauma scores, and spectrum of injuries were similar across the two groups. No patients underwent nontherapeutic laparotomy, and no patients in the PLUS group with negative FAST exams ended up requiring operative care. Use of CT scanning was markedly curtailed in the PLUS group, with only 53 percent undergoing CT versus 85 percent of control group. In the subset of patients who went to the operating room, only 25 percent of PLUS patients underwent CT versus 78 percent in the control group.
Not surprisingly, operative patients in the PLUS group were transferred to the operating room much faster, averaging only 57 minutes versus 166 minutes for the control group. Admission rate was similar across the two groups, but admitted patients in the PLUS group stayed fewer days on average, 6.2 versus 10.2. Admissions for operative patients in the PLUS group were shorter on average (10.7 versus 15.1 days), had a lower overall complication rate (21% versus 38%), and resulted in lower average total charges ($28,400 versus $47,600 per patient).
The authors acknowledged several limitations to this study, including a small sample size, high exclusion/ refusal rate, and questions about whether the results could be generalized. Most importantly, the lack of blinding may have significantly influenced the care of patients, given the involvement of the trauma teams in the performance and interpretation of the FAST exams. The results still strongly favor FAST in this patient population, and larger multicenter studies are indicated to confirm the clinical utility and ability to generalize this technology to trauma centers nationwide. This study supports the use of the FAST exam in the ED for patients with abdominal and chest trauma.
Luis M. Lovato, MD, an Associate Clinical Professor at the David Geffen School of Medicine at UCLA, the Director of Critical Care in the Department of Emergency Medicine at Olive View-UCLA Medical Center, and the Medical Editor of www.emcme.com, serves as the medical editor of this column.
About the LLSA
As part of its continuous certification program, the American Board of Emergency Medicine has developed the Lifelong Learning and Self-Assessment (LLSA) program to promote continuous education of diplomates. Each year, beginning in 2004, 16 to 20 articles are chosen based on the Emergency Medicine Model. A list of these articles can be found on the ABEM web site, www.abem.org.
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Strategies for Preventing Contrast-Induced Nephropathy in Patients with Underlying Kidney Disease
▪ IV fluids infused peri-procedurally: 1 mL of normal saline per kilogram of body weight per hour for 24 hours.
▪ N-acetylcysteine prophylactically: 600 mg by mouth every 12 hours for four doses, first dose up to 12 hours before procedure.
▪ No evidence to support use of diuretics, vasodilators, antioxidants, or prophylactic hemofiltration or hemodialysis.
Source: N Engl J Med 2006;354(4):379.
Formula Predicts Admissions
Researchers have developed a method to predict emergency hospital admissions for individuals 40 and older, according to a report in the July 14 Archives of Internal Medicine.
Peter T. Donnan, PhD, of the University of Dundee in Scotland, and colleagues studied 90,522 residents of Tayside, Scotland, where each individual who visited a general practitioner was assigned a 10-digit identifier. Participants entered the study between 1996 and 2004, and had at least three years of data available on hospital use and drug prescribing. They were followed for at least one year.
The researchers found 7.5 percent of the participants experienced an emergency hospital admission within one year of enrolling in the study. Those hospitalized tended to be older and male; live in an area with high social deprivation; have received more respiratory medications; have been prescribed analgesics, antibacterials, nitrates, and diuretics; and have had previous emergency admissions.
They concluded the model they've developed, which expresses the probability of emergency admission as a percentage, can assist clinicians on an individual patient basis but also physicians, insurers, and policymakers on a collective level.
Electronic Devices Don't Harm Heart
Ten seconds of exposure to an electronic control device (ECD) such as a TASER had no effect on the human heart, according to an August 10 online report in Academic Emergency Medicine.
Researchers from Hennepin County Medical Center in Minneapolis, led by Jeffrey D. Ho, MD, conducted a prospective, nonblinded study on 34 human volunteers to test for the occurrence of tachyarrhythmias when subjected to ECD application. Subjects underwent limited cardiography before, during, and after a 10-second TASER-X26 application. Heart rate and the presence of sinus rhythm also were determined.
They found no adverse events among the subjects. The mean heart rate prior to ECD application was 108.7 beats per minute; during application, 120.1 beats per minute; one minute after application, 94.1 beats per minute. Sinus rhythm was clearly demonstrated in 21 subjects during ECD exposure, but was not clearly demonstrated in 12 subjects due to movement artifact.
Previous swine research has supported the hypothesis that ECDs can cause dangerous cardiac rhythms, but Dr. Ho and colleagues concluded that a 10-second ECD exposure in an ideal cardiac axis application does not elicit concerning tachyarrhythmias in humans.
EPs Launch Emergency Service
Tom Scaletta, MD, and Mark Reiter, MD, MBA, recently announced the launch of Emergency Excellence (EmEx), which will recognize emergency departments delivering superior care.
EmEx will award the Emergency Medicine Center of Excellence designation to EDs that meet over one hundred Key Performance Indicators, each linked to seven pillars of excellence: safety, satisfaction, space, staff, support, systems, and solvency.
The impetus for creating EmEx was the 2006 Institute of Medicine report “Hospital-Based Emergency Care: At the Breaking Point,” which challenged emergency medicine leaders to establish evidence-based performance measures, explained Dr. Scaletta, EmEx's president and a past president of the American Academy of Emergency Medicine.
Dr. Reiter, the EmEx chief executive officer, stated that the goal of EmEx is to deliver the information and tools that hospitals need to achieve excellence in emergency care.
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