Alice M. Mitchell

Incidence of Contrast-Induced Nephropathy after Contrast-Enhanced Computed Tomography in the Outpatient Setting

BACKGROUND AND OBJECTIVES No prospective study has reported the incidence of contrast-induced nephropathy (CIN) or the associated morbidity and mortality after contrast-enhanced computed tomography (CECT) in the outpatient setting. DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS We enrolled and followed a prospective, consecutive cohort (June 2007 through January 2009) of patients who received intravenous contrast for CECT in the emergency department of a large, academic, tertiary care center. Outcomes measured were as follows (1) CIN: An increase in serum creatinine > or =0.5 mg/dl or > or =25% 2 to 7 d after contrast administration; (2) severe renal failure: An increase in serum creatinine to > or =3.0 mg/dl or the need for dialysis at 45 d; and (3) renal failure as a contributing cause of death (consensus of three independent physicians) at 45 d. RESULTS The incidence of CIN was 11% (70 of 633) among the 633 patients enrolled. Fifteen (2%) patients died within 45 d, including six deaths after study-defined CIN. Seven (1%) patients developed severe renal failure, six of whom had study-defined CIN. Of the six patients with CIN and severe renal failure, four died, and adjudicators determined that renal failure significantly contributed to all four deaths. Thus, CIN was associated with an increased risk for severe renal failure and death from renal failure. CONCLUSIONS CIN occurs in >10% of patients who undergo CECT in the outpatient setting and is associated with a significant risk for severe renal failure and death.

Prospective Study of the Incidence of Contrast-induced Nephropathy Among Patients Evaluated for Pulmonary Embolism by Contrast-enhanced Computed Tomography

OBJECTIVES Contrast-enhanced computed tomography (CECT) of the pulmonary arteries (CTPA) has become the mainstay to evaluate patients with suspected pulmonary embolism (PE) and is one of the most common CECT imaging studies performed in the emergency department (ED). While contrast-induced nephropathy (CIN) is a known complication, this risk is not well defined in the ED or other ambulatory setting. The aim of this study was to define the risk of CIN following CTPA. METHODS The authors enrolled and followed a prospective, consecutive cohort (June 2007 through January 2009) of patients who received intravenous (IV) contrast for CTPA in the ED of a large, academic tertiary care center. Study outcomes included 1) CIN defined as an increase in serum creatinine (sCr) of ≥ 0.5 mg/dL or ≥ 25%, 2 to 7 days following contrast administration; and 2) severe renal failure defined as an increase in sCr to ≥ 3.0 mg/dL or the need for dialysis within 45 days and/or renal failure as a contributing cause of death at 45 days, determined by the consensus of three independent physicians. RESULTS A total of 174 patients underwent CTPA, which demonstrated acute PE in 12 (7%, 95% confidence interval [CI] = 3% to 12%). Twenty-five patients developed CIN (14%, 95% CI = 10% to 20%) including one with acute PE. The development of CIN after CTPA significantly increased the risk of the composite outcome of severe renal failure or death from renal failure within 45 days (relative risk = 36, 95% CI = 3 to 384). No severe adverse outcomes were directly attributable to complications of venous thromboembolism (VTE) or its treatment. CONCLUSIONS   In this population, CIN was at least as common as the diagnosis of PE after CTPA; the development of CIN was associated with an increased risk of severe renal failure and death within the subsequent 45 days. Clinicians should consider the risk of CIN associated with CTPA and discuss this risk with patients.

Emergency Clinician–Performed Compression Ultrasonography for Deep Venous Thrombosis of the Lower Extremity

STUDY OBJECTIVE Emergency clinician-performed ultrasonography holds promise as a rapid and accurate method to diagnose and exclude deep venous thrombosis. However, the diagnostic accuracy of emergency clinician-performed ultrasonography performed by a heterogenous group of clinicians remains undefined. METHODS Prospective, single-center study conducted at an urban, academic emergency department (ED). Clinician participants included ED faculty, supervised residents, and midlevel providers who completed a training course for above-calf, 3-point-compression, venous ultrasonography. Patient participants had suspected leg deep venous thrombosis and greater than or equal to 1 predefined sign or symptom. Before any imaging, clinicians classified patients as low (<15%), moderate (15% to 40%), or high (>40%) pretest probability of deep venous thrombosis, followed by emergency clinician-performed ultrasonography. A whole-leg reference venous ultrasonography was then performed and interpreted separately in the radiology department. Patients were followed for 30 days. The criterion standard for deep venous thrombosis(+), required thrombosis of any leg vein on a reference ultrasonograph and clinical plan to treat. RESULTS We enrolled 183 patients, and 27 (15%) had deep venous thrombosis(+). The sensitivity and specificity emergency clinician-performed ultrasonography was 70% (95% confidence interval [CI] 60% to 80%) and 89% (95% CI 83% to 94%), respectively, with overall diagnostic accuracy of 85% (95% CI 79% to 90%). The posterior probability of deep venous thrombosis(+) among the 88 low-risk patients with a negative emergency clinician-performed ultrasonographic result was 1 of 88, or 1.1% (95% CI 0% to 6%), and the posterior probability of deep venous thrombosis(+) among 14 high-risk patients with a positive emergency clinician-performed ultrasonographic result was 11 of 14, or 79% (95% CI 49% to 95%). CONCLUSION The overall diagnostic accuracy of single-visit emergency clinician-performed ultrasonography performed by a heterogeneous group of ED clinicians is intermediate but may be improved by pretest probability assessment.

Immediate Complications of Intravenous Contrast for Computed Tomography Imaging in the Outpatient Setting Are Rare

OBJECTIVES Despite increasing attention to the long-term risks of radiation exposure and contrast-induced nephropathy (CIN), institutional guidelines and patient consent procedures for contrast-enhanced computed tomography (CECT) imaging in the emergency department (ED) setting have focused primarily on more immediate complications, directly attributable to the administration of intravenous (IV) iodinated contrast administration. Thus, this study sought to define the risk of these immediate complications with the overall aim of improving institutional guidelines and patient consent procedures. METHODS This was a prospective, consecutive cohort study of patients undergoing CECT of any body region in the ED, for complications occurring within 1 week of contrast administration, using predefined implicit definitions. Severe complications were defined as any of the following requiring medical or surgical intervention: bronchospasm with acute respiratory failure, airway obstruction, anaphylactoid shock, or acute pulmonary edema. The development of compartment syndrome, lactic acidosis, or pulmonary edema within 1 week of contrast administration was also considered a severe complication. RESULTS Of 633 patients, only five (0.8%, 95% confidence interval [CI] = 0.3% to 1.8%) reported any immediate complications, all of which were classified as minor. No patient developed a reaction meeting the study definition of a severe complication. CONCLUSIONS The frequency of severe, immediate complications from CECT imaging that includes IV contrast is less than 1%, and the frequency of mild complications is less than 2%. The authors conclude that CECT is associated with a very low rate of severe immediate complications.

Tandem Measurement of D‐dimer and Myeloperoxidase or C‐reactive Protein to Effectively Screen for Pulmonary Embolism in the Emergency Department

OBJECTIVES The hypothesis was that the tandem measurement of D-dimer and myeloperoxidase (MPO) or C-reactive protein (CRP) could significantly decrease unnecessary pulmonary vascular imaging in emergency department (ED) patients evaluated for pulmonary embolism (PE) compared to D-dimer alone. METHODS The authors measured the sequential combinations of D-dimer and MPO and D-dimer and CRP in a prospective sample of ED patients evaluated for PE at two centers. Patients were followed for 90 days for venous thromboembolism (VTE, either PE or deep venous thrombosis [DVT]), which required the consensus of two of three blinded physician reviewers. RESULTS The authors enrolled 304 patients, 22 with VTE (7%; 95% confidence interval [CI] = 5% to 10%). The sensitivity and specificity of a D-dimer alone (cutoff > or = 500 ng/mL) were 100% (95% CI = 85% to 100%) and 59% (95% CI = 53% to 65%), respectively, and was followed by pulmonary vascular imaging negative for PE in 38% (115/304; 95% CI = 32% to 44%). The combination of either a negative D-dimer, or MPO < 22 mg/dL, had a sensitivity of 100% and specificity of 73% (95% CI = 67% to 78%). Thus, tandem measurement of D-dimer and MPO would have decreased the frequency of subsequent negative pulmonary vascular imaging from 38% to 25% (95% CI of the difference of -13% = -5% to -20%). The combination of CRP and D-dimer would not have significantly improved the rate of negative imaging. CONCLUSIONS The tandem measurement of D-dimer and MPO would have significantly decreased negative pulmonary vascular imaging compared with D-dimer alone and should be validated prospectively.

N-Acetylcysteine Plus Intravenous Fluids Versus Intravenous Fluids Alone to Prevent Contrast-Induced Nephropathy in Emergency Computed Tomography

STUDY OBJECTIVE We test the hypothesis that N-acetylcysteine plus normal saline solution is more effective than normal saline solution alone in the prevention of contrast-induced nephropathy. METHODS The design was a randomized, double blind, 2-center, placebo-controlled interventional trial. Inclusion criteria were patients undergoing chest, abdominal, or pelvic computed tomography (CT) scan with intravenous contrast, older than 18 years, and at least one contrast-induced nephropathy risk factor. Exclusion criteria were end-stage renal disease, pregnancy, N-acetylcysteine allergy, or clinical instability. Intervention for the treatment group was N-acetylcysteine 3 g in 500 mL normal saline solution as an intravenous bolus and then 200 mg/hour (67 mL/hour) for up to 24 hours; and for the placebo group was 500 mL normal saline solution and then 67 mL/hour for up to 24 hours. The primary outcome was contrast-induced nephropathy, defined as an increase in creatinine level of 25% or 0.5 mg/dL, measured 48 to 72 hours after CT. RESULTS The data safety and monitoring board terminated the study early for futility. Of 399 patients enrolled, 357 (89%) completed follow-up and were included. The N-acetylcysteine plus saline solution group contrast-induced nephropathy rate was 14 of 185 (7.6%) versus 12 of 172 (7.0%) in the normal saline solution only group (absolute risk difference 0.6%; 95% confidence interval -4.8% to 6.0%). The contrast-induced nephropathy rate in patients receiving less than 1 L intravenous fluids in the emergency department (ED) was 19 of 147 (12.9%) versus 7 of 210 (3.3%) for greater than 1 L intravenous fluids (difference 9.6%; 95% confidence interval 3.7% to 15.5%), a 69% risk reduction (odds ratio 0.41; 95% confidence interval 0.21 to 0.80) per liter of intravenous fluids. CONCLUSION We did not find evidence of a benefit for N-acetylcysteine administration to our ED patients undergoing contrast-enhanced CT. However, we did find a significant association between volume of intravenous fluids administered and reduction in contrast-induced nephropathy.

Poisoning in Older Adults: A 5-Year Experience of US Poison Control Centers

BACKGROUND Poisoning in older adults has received relatively little attention. OBJECTIVE To describe poison exposures in older adults reported to US poison centers and identify substances that pose a unique risk to this population. METHODS: A retrospective review of human exposures for patients aged 60 years reported to the American Association of Poison Control Centers Toxic Exposure Surveillance System from 1993 to 1997 was performed. Frequencies and cross-tabulations were used to describe the data. Hazard factor analysis was conducted to identify medications that pose risk in this population. Statistical analysis included χ2 and Fishers exact test for hazard factors. RESULTS A total of 298 713 poison exposure cases were reported to US poison centers involving individuals aged 60 years between 1993 and 1997. The proportion of cases in this age group also steadily increased from 2.5% of all cases in 1993 to 3.4% of all cases in 1997. The mean age of the patients was 64.7 years, and 34.1% were males. Hazard factor analysis was conducted on unintentional exposures and adverse reactions to pharmaceutical agents to determine medications that posed increased risk to older adults. The substance categories that had the highest hazard factor were radiopharmaceuticals, asthma therapies, anticoagulants, anesthetics, and antidepressants. CONCLUSIONS Therapeutic errors and adverse reactions to medications are common reasons for major effects and fatal outcomes among older adults reported to poison centers. Understanding poisoning issues specific to this population may help direct future outreach education efforts.

Frequent pediatric emergency department use in infancy and early childhood.

ObjectiveTo define the threshold and population factors associated with pediatric emergency department (PED) use above the norm during the first 36 months of life. MethodsWe conducted a cross-sectional study of children born between 2003 and 2006, treated in a single PED within the first 36 months of life. Exclusion criteria included out-of-county residence or history of abuse or neglect. The primary outcome, frequent PED use, was defined by the 90th percentile for PED visits per patient. Multivariate analysis was used to identify factors associated with frequent PED use. ResultsA total of 41,912 visits occurred for 16,664 patients during the study. Pediatric ED use skewed heavily toward less than 2 visits per patient (median, 2; range, 1–39; interquartile range, 2). The threshold for frequent PED use was 5 or more visits per patient and occurred for 14% (95% confidence interval [95% CI], 13%–15%) of patients. Most visits were coded with low acuity International Classifications of Diseases, 9th Revision, Clinical Modification codes. The following factors were strongly associated with frequent PED use: lack of primary care physician (odds ratio [OR], 6.03; 95% CI, 5.39%–6.80%; P < 0.0001), nonprivate insurance (OR, 3.64; 95% CI, 2.99%–4.46%; P<0.0001), and history of inpatient admission (OR, 3.09; 95% CI, 1.66%–2.24%; P < 0.0001). Leaving without being seen, black race, Hispanic ethnicity, and residence in a poverty-associated zip code were also significantly associated, but less strongly predictive of, frequent PED use. ConclusionsThe threshold for frequent PED use was more than 5 visits per patient within the first 36 months of life. Further study is needed to better define this population and develop targeted interventions to ensure care provision occurs in the ideal setting.

Diagnostic accuracy of Computer-Assisted Database-Derived pretest probability assessment for acute coronary syndrome

Study objectives: We determine the diagnostic accuracy of a noninvasive clinical screening instrument for the detection of acute coronary syndrome (ACS) in emergency department (ED) patients. The screening instrument is composed of clinical data input into a computer to estimate the probability of ACS. Methods: We aim to enroll 1,000 patients with complete data who were observed in an ED chest pain evaluation unit at Carolinas Medical Center, Duke University, and the University of California–Davis, and prospectively collect data to determine the pretest probability (PTP) of ACS for each patient using 3 methods of PTP assessment: (1) a computer-assisted, database-derived method; (2) the acute cardiac ischemia time-insensitive predictive instrument (ACI-TIPI) method; and (3) physician estimate to the nearest 1%. This information will be used to compare which method of PTP assessment categorizes the highest percentage of patients as being very low risk for ACS (ie, PTP Results: We completed enrollment on August 1, 2004, and follow-up and adjudication of outcomes continues. We enrolled a total of 1,154 patients and expect to obtain valid follow-up in 85% of subjects. Complete pretest probability are data available for 723 patients. Only 12 (1.6%) patients with a positive outcome were identified. The mean (median) pretest probability estimates by the 3 methods were 5.2% (4.0%) for physician estimate, 6.4% (4.3%) for attribute matching, and 13.6% (9.9%) for ACI-TIPI. The percentage of all patients estimated to have a pretest probability of ACS of less than 2% was 19% (95% confidence interval [CI] 16% to 22%) for clinicians, 34% (95% CI 31% to 38%) for attribute-matching, and 9% (95% CI 7% to 12%) for ACI-TIPI. No patient with a pretest probability of less than 2% estimated by any of the 3 methods developed ACS. Conclusion: At interim analysis, the rate of positive outcomes for ACS was unexpectedly low in this sample of patients evaluated in ED chest pain units. Attribute matching categorized significantly more patients as having a very low pretest probability compared with clinician estimate or ACI-TIPI.