Abstract
BACKGROUND
The factors that affect the implementation of preventive care for contrast-induced acute kidney injury (CIAKI) are unknown.
OBJECTIVE
To assess patient and provider factors associated with the use of preventive care for CIAKI.
DESIGN
Prospective cohort study.
PARTICIPANTS
Patients with kidney disease undergoing procedures with intravascular iodinated radiocontrast.
MEASUREMENTS
We recorded the use of preventive care defined as the administration of: (1) pre- and post-procedure isotonic intravenous (IV) fluid, (2) N-acetylcysteine, and (3) iso-osmolal radiocontrast. We surveyed patients’ providers to assess their knowledge, experience, and training on CIAKI and used multiple logistic regression to assess the independent associations of patient and provider factors with the use of these preventive interventions.
RESULTS
We enrolled 660 patients and 87 providers. Patient factors associated with use of IV fluid and N-acetylcysteine were higher baseline serum creatinine (OR 1.5 and 5.0, p < 0.05) and inpatient status (OR 3.0 and 6.3, p < 0.05), while higher baseline serum creatinine was associated with the use of iso-osmolal contrast (OR = 13.4, p < 0.01). The primary provider characteristics associated with the use of IV fluid and N-acetylcysteine were a greater degree of prior training on CIAKI (OR 1.9 and 2.8, p < 0.05) and higher number of prior patients with CIAKI (OR 2.7 and 2.6, p < 0.05).
CONCLUSIONS
Patient baseline kidney function and provider training and experience with CIAKI are independently associated with the use of preventive care. Efforts to increase and intensify the training providers receive on CIAKI may help decrease the incidence of this costly iatrogenic condition.
KEY WORDS: predictors, contrast-induced acute kidney injury, patients, providers, preventive care
INTRODUCTION
Contrast-induced acute kidney injury (CIAKI), commonly defined as an increase in serum creatinine (Scr) of ≥25% and/or 0.5 mg/dl has been associated with increased mortality and medical resource utilization. CIAKI is unique in that its risk factors are well known, it is universally iatrogenic, and its timing is highly predictable, which make it particularly amenable to preventive care.1–7 Over the past 2 decades, preventive interventions for CIAKI have been identified.8–11 Randomized clinical trials have demonstrated that isotonic intravenous (IV) fluid is effective and superior to hypotonic IV fluid for the prevention of CIAKI in high-risk patients.8,9,11 These observations resulted in clinical recommendations to administer isotonic IV fluid in high-risk patients.4,12,13 Clinical trials and meta-analyses have also found that the anti-oxidant N-acetylcysteine (NAC) decreases the risk of CIAKI.10,14–16 Although consensus on the effectiveness of NAC is lacking, some experts recommend its use in high-risk patients.4 Finally, while studies comparing iso- and low-osmolal contrast report conflicting findings, some studies have found iso-osmolal contrast to be less nephrotoxic, resulting in recommendations from some medical organizations to use iso-osmolal contrast for high-risk patients.17–23
Despite clinical studies and recommendations supporting the use of these measures, prior studies demonstrate that these preventive interventions are sub-optimally utilized.24,25 Factors contributing to the non-uniform implementation of these preventive strategies are not known. Increasing our understanding of the factors that impact translation of existing empiric knowledge and expert recommendations on the prevention of CIAKI into clinical practice is essential to improve the prevention of this iatrogenic condition. We hypothesized that patient factors associated with an increased risk for CIAKI, including higher baseline serum creatinine concentration and provider factors, including prior training on CIAKI, would be associated with the use of preventive care. We undertook this study to assess the patient and provider factors associated with the use of preventive care for CIAKI.
METHODS
Patient Population
We conducted a prospective, observational study of patients receiving intravascular iodinated radiocontrast at a VA Healthcare System between February 1, 2005 and July 31, 2006. All study procedures were approved by the local Institutional Review Board.
We identified patients scheduled for computed tomography (CT) with IV radiocontrast or angiography (coronary or non-coronary) in advance of the procedure, recorded the Scr measured most proximate to and within 60 days of the procedure, and calculated patients’ baseline estimated glomerular filtration rate (eGFR) using the four-variable Modification of Diet in Renal Disease study equation.26 Patients scheduled to receive intravascular radiocontrast at our institution are recommended to have Scr measured within 60 days prior to the procedure. We only recruited patients at increased risk for CIAKI based on a pre-procedure eGFR value <60 ml/min/1.73 m2. We excluded individuals on maintenance dialysis and subjects unable to provide informed consent based on the need for mechanical ventilation. To enroll patients for whom there was sufficient time for providers to prescribe preventive care, we excluded patients undergoing emergent coronary angiography for ST-elevation myocardial infarction or emergent CT for the diagnosis of acute pulmonary embolism or ruptured aortic aneurysm. To limit the study to patients whose principal risk factor for acute kidney injury was radiocontrast, we excluded patients receiving IV vasopressor or inotropic medications, and hospitalized patients with systolic blood pressure less than 90 mmHg at the time of the procedure. For all eligible patients willing to participate, the study coordinator obtained informed consent in person.
Baseline Patient Data Collection
Using the electronic health record and a standard chart abstraction questionnaire, we recorded patients’ demographic characteristics, prescribed medications, and comorbid medical conditions. We tracked whether any IV fluids were administered prior to and following the procedure, including the type, rate, and duration of IV fluid; whether oral and/or IV NAC in any dose was prescribed; and the type and volume of contrast administered.
Provider Recruitment and Data Collection
Following each procedure, we identified the provider who ordered the CT or performed angiography and asked them to complete a written survey on CIAKI. We administered the survey to providers who ordered CT rather than the radiologist who performed the scan, as the ordering providers were responsible for prescribing preventive care. Conversely, for patients who underwent angiography, we surveyed the proceduralist, as they were most responsible for implementing preventive measures. The investigator-designed survey assessed providers’ demographic and professional background, understanding of the risk factors for CIAKI, knowledge of preventive care for CIAKI, and prior training and experience with patients with CIAKI (Appendix). For questions pertaining to knowledge of the risk factors and preventive interventions, providers were able to answer yes, no, or not sure. Providers were asked to report their prior training on CIAKI using a 4-point Likert scale ranging from “none” to “a lot.” Surveys were mailed to providers along with an informed consent form, and if not completed and returned within 2 months, remailed. Providers who cared for more than one study patient were asked to complete the survey only once, and data contained on that survey were linked to each of that provider’s patients.
Statistical Analyses
Our primary analyses focused on the associations of patient and provider factors with the use of: (1) pre- and post-procedure isotonic IV fluid (NaCl or NaHCO3), (2) NAC, and (3) iso-osmolal radiocontrast. We centered and scaled continuous patient variables including baseline Scr, blood urea nitrogen (BUN), and age to improve efficiency and report interpretable odds ratios. These variables were centered at values close to the mean or median and scaled by the approximate standard deviation. Baseline Scr was centered at 132.6 μmol/l (1.5 mg/dl) and scaled by 44.2 μmol/l (0.5 mg/dl), while baseline BUN was centered at 8.9 μmol/l (25 mg/dl) and scaled by 3.6 μmol/l (10 mg/dl). The assumption of linearity was tested for all linear predictors, including age, serum creatinine, BUN, and level of prior training on CIAKI. Univariate associations of patient factors with the use of preventive care were assessed using logistic regression with random intercepts for individual providers. Variables significant at the p ≤0.25 level in univariate analyses were included in multivariable models. We used random effects multiple logistic regression to analyze the independent association of patient factors with the use of these three preventive interventions, accounting for clustering of patients by individual providers with a random intercept for each provider. All 660 study patients were included in these analyses.
We used these same analysis methods to assess the univariate and multivariable associations of provider factors with the use of the three preventive measures. Due to significant collinearity of provider variables using a p ≤ 0.25 for inclusion in the multivariable model, we only included provider variables that were significant at the p ≤ 0.1 level in univariate analyses. Since provider age and years in practice were highly correlated, we only considered years in practice in these analyses. These analyses were restricted to the 362 patients that were linked to provider surveys.
We also conducted sensitivity analyses in which both patient and provider factors were analyzed in a single model. These analyses included a separate intercept for patients with completed provider surveys and utilized all 660 patients. All analyses were conducted using STATA version 10 (College Station, Tx) and SAS version 9.1 (Cary, NC). A p-value <0.05 represented statistical significance.
RESULTS
Patient Population
We screened 11,410 patients undergoing radiographic procedures, of whom 1,884 (17%) were scheduled to receive intravascular radiocontrast and had a baseline eGFR <60 ml/min/1.73m2. Of these, 258 did not show up for the procedure, 141 were unavailable for recruitment, and 254 did not receive intravascular contrast. Of the remaining 1,231 potentially eligible patients, 247 (20%) refused to participate, and 324 (26%) had one or more exclusion criteria, resulting in a study population of 660 patients (Fig. 1). Four hundred twenty-one patients (64%) underwent CT, 181 (27%) underwent coronary angiography, and 58 (9%) underwent non-coronary angiography (Table 1).
Figure 1.
Patient and provider recruitment.
Table 1.
Baseline Patient Characteristics*
| Demographics | (N = 660) |
|---|---|
| Mean age (years) † | 69 ± 10 |
| Male sex | 630 (95) |
| Race (white) | 594 (90) |
| Race (African-American) | 48 (7) |
| Inpatient | 188 (29) |
| Ambulatory | 451 (68) |
| Long-term care | 21 (3) |
| Comorbid conditions | |
| Diabetes mellitus | 300 (45) |
| Liver disease | 76 (12) |
| Congestive heart failure | 133 (20) |
| Peripheral vascular disease | 125 (19) |
| Cerebrovascular disease | 95 (14) |
| Procedure characteristics | |
| CT scan | 421 (64) |
| Coronary angiogram | 181 (27) |
| Non-coronary angiogram | 58 (9) |
| Low-osmolar contrast | 92 (14) |
| Iso-osmolar contrast | 568 (86) |
| Volume contrast (ml)‡ | 140 (100,150) |
| Baseline eGFR (ml/min/1.73m2)‡ | 52 (47, 56) |
| Prescribed medications | |
| Non-steroidal anti-inflammatory medications | 67 (10) |
| Loop diuretics | 175 (27) |
| ACEIs/ARBs§ | 306 (46) |
| Theophylline | 4 (0.6) |
| Calcium channel blockers | 173 (26) |
*Data are presented as n (%) unless otherwise specified
†Mean ± standard deviation
‡Median (interquartile range)
§ACEI = angiotensin converting enzyme inhibitor; ARB = angiotensin receptor blocker
Provider Population
Of the 243 eligible study providers, 87 (36%) completed the study survey. These 87 providers managed 362 study patients (55% of overall study population) (Fig. 1). The median age of providers was 36 years, 61 (70%) were white, and 38 (44%) were trainees (e.g., intern, resident, fellow). Fifty-four providers (62%) reported little to no prior training on CIAKI (Table 2). Providers with fewer than 6 years in practice were more likely to have cared for patients undergoing coronary angiography than CT scan (95% vs 33%) and for inpatients compared to outpatients (81% vs 41%).
Table 2.
Provider Characteristics*
| Demographics | N = 87 |
|---|---|
| Age ‡ | 36 (31, 49) |
| Male sex | 46 (53) |
| Race (white) | 61 (73) |
| Race (Asian) | 23 (27) |
| Professional characteristics | |
| Intern/resident | 16 (18) |
| Fellow | 22 (25) |
| Attending physician | 25 (29) |
| Nurse practitioner/physician assistant | 20 (23) |
| Internal medicine or specialty | 57 (66) |
| Years in practice† | 5 (0, 18) |
| Outpatient clinics per week | 2 (1, 4) |
| <2 weekly outpatient clinics | 39 (46) |
| 2–3 weekly outpatient clinics | 20 (24) |
| >3 weekly outpatient clinics | 25 (30) |
| Experience with CIAKI | |
| No. monthly studies ordered with contrast† | 10 (4,16) |
| No. prior patients with CIAKI† | 3 (0,10) |
| <6 prior patients with CIAKI | 54 (70) |
| 6–10 prior patients with CIAKI | 13 (17) |
| >10 prior patients with CIAKI | 10 (13) |
| Training on CIAKI | |
| None | 15 (17) |
| A little bit | 39 (45) |
| A moderate amount | 26 (30) |
| A lot | 7 (8) |
*Data presented as n (%) unless otherwise specified
†Median (interquartile range)
Use of Preventive Care
Overall, 157 patients (24%) received pre- and post-procedure isotonic IV fluid, 259 (39%) received NAC, 568 (86%) received iso-osmolal contrast, and 120 (18%) received all three interventions. Use of all three interventions was highest with coronary angiography (37% of patients) and lowest with CT (9% of patients) (Table 3). Among patients with diabetes mellitus, who were at highest risk for CIAKI, the use of IV fluid and NAC was higher with angiography than CT scan, while the frequency of use of iso-osmolal contrast was similar for both procedures (Fig. 2). The frequency of use of IV fluids in the present study, specifically for patients who underwent coronary angiography, was generally comparable to past estimates of the use of this preventive intervention.25
Table 3.
Use of Preventive Interventions for CIAKI by Procedure Type*
| Interventions | Overall (N = 660) | CT scan (N = 421) | Coronary angiogram (N = 181) | Non-coronary angiogram (N = 58) | P-value† |
|---|---|---|---|---|---|
| Isotonic IV fluid | 157 (24) | 57 (14) | 82 (45) | 18 (31) | <0.001 |
| N-acetylcysteine | 259 (39) | 73 (17) | 152 (84) | 34 (59) | <0.001 |
| Iso-osmolal contrast | 568 (86) | 362 (86) | 151 (83) | 58 (100) | 0.08 |
| All three interventions | 120 (18) | 37 (9) | 67 (37) | 16 (28) | <0.001 |
*Data denote n (%) of patients
†P-values based on Fisher’s exact test
Figure 2.
Use of preventive care by procedure type in patients with diabetes mellitus.
Associations of Patient Characteristics with the Use of Preventive Care
The only patient factor independently associated with the use of each of the three preventive interventions was baseline Scr (Table 4). Each 44.2 μmol/l (0.5 mg/dl) increment in baseline Scr above 132.6 μmol/l (1.5 mg/dl) was associated with a greater odds of using isotonic IV fluid (OR = 1.5, 95% CI 1.1–2.1), NAC (OR = 5.0, 95% CI = 2.5–10.1), and iso-osmolal contrast (OR = 13.4, 95% CI 5.1–35.2). Inpatient status at the time of the procedure and the performance of coronary angiography (versus CT) were independently associated with the use of IV fluid and NAC. The performance of non-coronary angiography was independently associated with the use of NAC.
Table 4.
Associations of Patient Factors with Use of Preventive Interventions
| Factor | Association with IV fluid use | Association with NAC use | Association with iso-osmolal contrast use | |||
|---|---|---|---|---|---|---|
| Unadjusted OR | Adjusted OR | Unadjusted OR | Adjusted OR | Unadjusted OR | Adjusted OR | |
| Demographic/clinical factors | ||||||
| Age | 0.8 (0.6–1.0) | 0.9 (0.7–1.1) | 0.9 (0.7–1.1) | – | 0.9 (0.7–1.1) | – |
| Race (African-American) | 1.5 (0.6–3.4) | – | 3.8 (1.4–10.7) | 1.3 (0.5–3.3) | 4.5 (1.0–19.7) | 1.8 (0.4–8.4) |
| Race (other/unknown) | 1.4 (0.4–5.7) | – | 0.4 (0.1–2.2) | 0.6 (0.1–2.5) | 0.8 (0.2–3.1) | 0.6 (0.1–2.3) |
| Race (white)* | 1.0 | – | 1.0 | 1.0 | 1.0 | 1.0 |
| Inpatient status | 3.1 (1.9–5.0) | 3.0 (1.8–4.9) | 6.5 (3.5–12.3) | 6.3 (3.7–10.9) | 0.7 (0.4–1.1) | – |
| Long-term care | 0.9 (0.2–3.9) | 1.7 (0.4–7.3) | 0.4 (0.1–2.5) | 0.8 (0.2–4.0) | 0.9 (0.2–3.5) | – |
| Outpatient status* | 1.0 | – | 1.0 | 1.0 | 1.0 | – |
| Laboratory variables | ||||||
| Serum creatinine † | 1.8 (1.3–2.4) | 1.5 (1.1–2.1) | 6.1 (3.1–11.9) | 5.0 (2.5–10.1) | 15.9 (6.4–39.5) | 13.4 (5.1–35.2) |
| Blood urea nitrogen ‡ | 1.4 (1.2–1.7) | 1.0 (0.8–1.3) | 1.7 (1.3–2.1) | 1.0 (0.7–1.3) | 1.6 (1.2–2.2) | 1.1 (0.8–1.5) |
| Clinical conditions | ||||||
| Diabetes mellitus | 1.6 (1.0–2.5) | 1.3 (0.8–2.1) | 1.6 (1.0–2.6) | 1.1 (0.7–1.8) | 0.9 (0.6–1.5) | – |
| Congestive heart failure | 1.4 (0.8–2.5) | 0.8 (0.5–1.5) | 2.0 (1.1–3.6) | 1.0 (0.5–1.8) | 1.1 (0.6–2.0) | – |
| Peripheral vascular disease | 1.3 (0.7–2.4) | – | 2.3 (1.2–4.3) | 1.5 (0.8–2.7) | 1.4 (0.7–2.7) | – |
| Procedural factors | ||||||
| Coronary angio | 7.5 (3.6–15.5) | 6.3 (3.2–12.5) | 35.8 (17.7–72.6) | 38.5 (19.8–74.8) | 0.9 (0.5–1.5) | 0.7 (0.4–1.3) |
| Non-coronary angio | 5.4 (2.1–14.2) | 2.3 (0.9–6.3) | 10.6 (4.7–24.1) | 3.5 (1.5–8.4) | 2.9 (0.8–10.3) | 1.5 (0.4–5.5) |
| CT* | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 | 1.0 |
Data presented as odds ratio (OR) and 95% confidence interval
*Referent category
– Not included in model as p > 0.25 in univariate analyses
†OR represents increased odds of use of preventive intervention for each 44.2 μmol/l (0.5 mg/dl) increase in baseline Scr above 132.6 μmol/l (1.5 mg/dl)
‡OR represents increased odds of use of preventive intervention for each 3.6 μmol/l (10 mg/dl) increase in baseline BUN above 8.9 μmol/l (25 mg/dl)
Associations of Provider Factors with the Use of Preventive Care
A greater degree of prior training on CIAKI was independently associated with the use of isotonic IV fluid (OR = 1.9, 95% CI 1.1–3.2) and with the use of NAC (OR = 2.8, 95% CI 1.7–4.5) (Table 5). Providers who had cared for ten or more patients with CIAKI were more likely to use isotonic IV fluid (OR = 2.7, 95% CI 1.1–6.5) and NAC (OR = 2.6, 95% CI 1.1–6.2). Providers who had practiced less than 6 years (including trainees) were more likely to administer IV fluids (OR = 11.4, 95% CI 3.0–43.5) and prescribe NAC (OR = 4.4, 95% CI 1.8–10.7). Providers with fewer than two weekly outpatient clinics were more likely to prescribe NAC.
Table 5.
Associations of Provider Factors with Use of Preventive Interventions
| Factor | Association with IV fluid use | Association with NAC use | ||
|---|---|---|---|---|
| Knowledge of CIAKI† | Unadjusted OR | Adjusted OR | Unadjusted OR | Adjusted OR |
| CKD as strongest risk | 0.3 (0.1–1.1) | 0.6 (0.2–1.3) | 0.5 (0.2–1.9) | – |
| Isotonic saline | 3.4 (0.9–12.3) | 1.1 (0.3–3.8) | 5.8 (1.4–23.6) | 1.2 (0.5–3.3) |
| Isotonic bicarbonate | 3.2 (1.1–9.3) | 1.1 (0.4–2.7) | 6.2 (1.8–20.8) | 1.8 (0.8–3.7) |
| Demographics | ||||
| Non-internal medicine | 0.3 (0.1–1.0) | 1.2 (0.4–3.9) | 0.3 (0.1–1.2) | 0.7 (0.3–1.6) |
| Female sex | 0.2 (0.1–0.5) | 0.7 (0.2–1.9) | 0.5 (0.1–1.6) | – |
| Weekly clinic sessions | ||||
| ≥4* | 1.0 | 1.0 | 1.0 | 1.0 |
| <2 | 21.0 (3.1–141.5) | 2.8 (0.6–14.1) | 128.3 (18.6–883.9) | 19.6 (4.1–92.4) |
| 2–3 | 8.6 (1.1–69.0) | 3.2 (0.6–17.3) | 15.9 (2.1–121.0) | 3.8 (0.7–19.6) |
| Years in practice | ||||
| ≥6* | 1.0 | 1.0 | 1.0 | 1.0 |
| <6 | 17.6 (6.5–47.6) | 11.4 (3.0–43.5) | 16.1 (5.3–49.0) | 4.4 (1.8–10.7) |
| Training and experience with CIAKI | ||||
| Level of prior training‡ | 1.8 (0.9–3.4) | 1.9 (1.1–3.2) | 3.6 (1.6–7.9) | 2.8 (1.7–4.5) |
| <10 patients with CIAKI* | 1.0 | 1.0 | 1.0 | 1.0 |
| ≥10 patients with CIAKI | 6.2 (1.5–26.5) | 2.7 (1.1–6.5) | 18.3 (3.1–107.7) | 2.6 (1.1–6.2) |
Data presented as odds ratio (OR) and 95% confidence interval
*Referent category
– Not included in model as p > 0.1 in univariate analyses
†Denotes provider response of “yes” to knowledge of chronic kidney disease (CKD) as strongest risk factor for CIAKI and efficacy of isotonic saline and isotonic bicarbonate for prevention of CIAKI
‡Denotes increase in odds of use of preventive intervention with each additional degree of training based on 4-point Likert scale (1 = none to 4 = a lot)
Overall, patients whose providers had two to three weekly outpatient clinics and ten or fewer prior patients with CIAKI were more likely to receive iso-osmolal contrast. However, we recognized during the course of the study that decisions on the type of contrast for patients undergoing CT were made by radiology personnel and not the provider who had ordered the scan and completed our study survey. Therefore, we repeated the analyses of the association of provider factors with the use of iso-osmolal contrast among the 144 patients who had undergone angiography and to whom provider data could be linked. In these analyses, providers who had ordered five or fewer monthly studies with contrast were more likely to use iso-osmolal contrast (OR = 10.3, 95% CI 1.2–84.5), as were providers from non-internal medicine disciplines (OR = 6.9, 95% CI 1.4–33.9). However, non-internal medicine providers and those ordering fewer studies were more likely to be linked with non-coronary angiograms, for which iso-osmolal contrast was used uniformly.
In sensitivity analyses in which patient and provider variables that were independently associated with the use of preventive care in individual models were combined, there was no impact on patient factors and only a mildly attenuating effect of provider training on the use of isotonic IV fluids. There were no differences in the use of the three preventive interventions between patients whose providers completed the survey and those whose provider did not.
DISCUSSION
In this prospective observational study, lower baseline kidney function and inpatient status were the primary patient factors associated with the use of preventive care for CIAKI, while a greater degree of prior training on CIAKI, a higher number of prior patients with this condition, and fewer years in practice were the principal provider factors associated with use of preventive care. These novel findings should help shape future efforts to train providers on how to most effectively prevent this iatrogenic condition.
It is not surprising that preventive care was more common among hospitalized patients independent of serum creatinine, as outpatient radiology and angiography suites may not be equipped or staffed to deliver therapies such as IV fluid on a routine basis. Our observation that higher baseline Scr was the only patient factor associated with the use of each of the three preventive interventions likely reflects widespread recognition that underlying kidney disease is the principal risk factor for CIAKI. However, heart failure, which increases risk for CIAKI, and diabetes mellitus, which significantly amplifies risk among patients with chronic kidney disease, were not associated with greater use of preventive care.3,27 Efforts to educate providers about CIAKI should not only emphasize the importance of chronic kidney disease, but should raise awareness of the importance of heart failure and diabetes mellitus in determining patients’ level of risk.
We found that providers’ prior level of training on and experience with CIAKI were the primary factors associated with the use of isotonic IV fluid and NAC. However, well over half of providers surveyed reported receiving little to no prior training on this condition. The successful translation of empiric knowledge and implementation of clinical recommendations on the prevention of CIAKI appear to be highly dependent on the provision of adequate education and training. Although we did not assess the form of training our providers had received, future efforts should seek to delineate the most effective means of disseminating information on CIAKI to clinicians and promote educational programs to broaden the number of providers who receive training on this subject.
Interestingly, providers with fewer outpatient clinics and those who had been practicing for fewer years were more likely to administer preventive care. Assuming that providers with fewer years in practice were trainees who spend a disproportionate amount of time in the hospital setting and that providers with fewer outpatient clinics provide more inpatient care, these findings suggest that hospital-based providers may be more likely to implement preventive care for CIAKI. Although providers with fewer years in practice were more likely to have cared for inpatients and those undergoing coronary angiography, in whom the use of preventive care may be easier to deliver, determining the extent to which the proportion of time spent caring for inpatients is associated with the provision of preventive care for CIAKI is highly relevant given the trend in medicine towards dividing the care of patients between hospitalists and outpatient providers. Studies in other patient populations, including those with pneumonia and heart failure, demonstrate that hospitalists are more likely than community providers to deliver evidence-based care to inpatients.28,29 While we did not categorize providers according to the hospitalist model, our findings suggest hospital-based clinicians may be more likely to implement preventive care for CIAKI.
The strongest predictor of the use of iso-osmolal contrast was patients’ baseline serum creatinine level, while provider factors had little impact on the choice of contrast agent. These findings, when considered in light of the overwhelming use of iso-osmolal contrast in our study population, suggest that many providers perceive a lower risk for CIAKI with iso-osmolal compared to low-osmolal contrast. Studies on the comparative nephrotoxicity of iso- and low-osmolal contrast have reported conflicting findings, with some studies reporting less risk with iso-osmolal Iodixanol compared to low-osmolal Iohexol (GE Healthcare, Princeton, NJ), which is the low-osmolal contrast agent used at our institution. Future research will need to more clearly delineate the factors that affect providers’ choice of contrast agent and how those decisions impact patient outcomes.
This study has certain limitations. First, we did not assess system-level factors that could have influenced the use of preventive care (standard protocols for IV fluids or NAC, assessment of post-procedure Scr). However, at the time of this study, there were no standard protocols for the prevention of CIAKI at our institution. Nonetheless, this was a single-center study, and our findings may not be generalizable to the broader medical community or be applicable to medical institutions with protocols in place for the prevention of CIAKI. Second, our study survey was not validated prior to use, and we cannot be certain that the data collected accurately reflected provider’s true knowledge or experience. Third, more than half of providers did not return the study survey, which may have biased our assessment of the association of provider factors with the use of preventive care. However, adjusting our analyses for survey completion did not alter our findings. Fourth, our analyses were predicated on the idea that NAC and iso-osmolal contrast (compared to low osmolal contrast) are effective preventive interventions. However, there continues to be some clinical equipoise on the efficacy of these two interventions that could have affected our assessment of the associations of provider characteristics with the use of these measures. Finally, our observation that providers with fewer years in practice, which included trainees, were more likely to use preventive care may be confounded by the structure of care at our institution, in which trainees work under the supervision of an attending physician. Patients treated by trainees may have been more likely to receive preventive care because they had multiple providers involved in their care.
In conclusion, patient factors, including baseline kidney function and inpatient status, as well as provider characteristics including level of training and prior experience with CIAKI, are associated with the use of preventive care for CIAKI. Informing clinicians of empiric data and expert recommendations on the prevention of CIAKI should be a primary focus of efforts seeking to reduce the incidence and adverse outcomes of this iatrogenic condition.
Acknowledgements
This study and Dr. Weisbord were supported by a VA Health Services Research and Development Career Development Award (RCD 03–176) and a VA Stars and Stripes Competitive Pilot Project Fund award. Dr. Fine was supported in part by a mid-career development award (K24 AI001769) from the National Institute of Allergy and Infectious Diseases. All of the listed authors contributed to this work.
Conflict of Interest Dr. Weisbord has served as a consultant to and previously served as an investigator on a multi-site study of GE Healthcare. None of the other authors have any potential conflicts of interest.
Appendix: Provider Survey
Instructions: Below is a list of questions about you and your knowledge of radiocontrast nephropathy. Please check the appropriate box when appropriate and answer other questions to the best of your ability.
References
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