Figure 1. Standard deviation – Age Age group 40–60 years: 61 patients; Age group 61–80 years:...

Figure 2. Renal function at discharge. Among the 93 patients with preserved renal function at admiss...

Table 1. Clinical variables according to the presence or absence of contrast-induced nephropathy

Figure 3. Impaired renal function (by sex and age group). Regarding sex distribution, 11% of patient...

Figure 4. Contrast volume in patients with CIN at discharge. A total of 55% of patients with CIN req...

Figure 5. Prevalence of risk factors in patients with CIN. Smoking (89%), hypertension (64%), and ex...

Figure 6. Proportion of patients with contrast-induced nephropathy according to nephroprotection. Se...

Introduction

Contrast-induced nephropathy (CIN) is defined as acute renal failure occurring between 48 and 72 hours after the endovenous administration of iodinated contrast, without any other identifiable cause. It is characterized by an absolute increase in serum creatinine greater than or equal to 0.5 mg/dL, or a relative increase greater than or equal to 25% compared with the patient’s baseline value4. This complication is associated with an increased risk of mortality, constituting a predictor of poor prognosis in both the short and long term1, 8, 10.

It is the third most frequent cause of kidney injury in patients undergoing emergency cardiac catheterization, with an in-hospital mortality risk 2 to 4 times higher than that of patients without it1, 2, 3, 11. In fact, patients who develop this complication have an in-hospital mortality rate of 22%, compared with 1.4% for those who do not4.

Risk factors for CIN are divided into those related to the patient (such as a glomerular filtration rate below 60 mL/min/1.73 m², heart failure, anemia, diabetes, hypertension, dyslipidemia, age over 75 years, sustained hypotension, concomitant use of nephrotoxic drugs, and liver disease) and those related to the procedure (all contrast agents have a cytotoxic effect). The risk increases proportionally to the volume of contrast administered: it has been shown that every additional 20 mL above 4 mL/kg doubles the risk of developing this complication. Therefore, the recommended maximum dose should not exceed 5 mL/kg, with an absolute limit of 300 mL3, 8, 9.

The determination of high-sensitivity troponin has proven useful for diagnosis and prognosis in patients with renal dysfunction, which allows for the adoption of strategies such as the use of non-ionic contrast agents at the lowest possible dose, avoidance of repeat procedures within 72 hours, and prevention of intravascular volume depletion1, 5, 6, 7, 12.

In Argentina, there is limited published information on the prevalence of CIN in the setting of emergency coronary studies, especially in state-funded hospitals in the interior of the country. This lack of local data hinders the development of prevention protocols tailored to our specific healthcare context, which is marked by heterogeneous resources, access to nephroprotection, and patient sociodemographic characteristics. Knowing how big is this problem in our setting makes it possible to bring to the forefront this frequent complication, improve prevention strategies, and provide useful evidence for future renal care policies in interventional cardiology.

The aim of this study was to determine the prevalence of CIN in patients undergoing emergency cardiac catheterization in an acute setting at Hospital Descentralizado Dr. Guillermo Rawson, assessing renal function at admission, 48 hours after the procedure, and at discharge, along with the dose of contrast used, patient risk factors, and nephroprotection measures applied.

Materials and methods

The study enrolled a total of 101 patients undergoing emergency cardiac catheterization at Hospital Público Descentralizado Dr. Guillermo Rawson (San Juan, Argentina) between June 1, 2021, and June 30, 2022. This was designed as a retrospective, observational, and descriptive study, with the aim of estimating the prevalence of contrast-induced nephropathy (CIN) in patients undergoing emergency catheterization.

Patients were selected using convenience sampling, choosing only those who had the complete clinical data required for the analysis. This strategy sought to ensure homogeneity and completeness of related variables, thereby favoring the internal validity of the study. Cases with incomplete or missing data in key variables were excluded.

The selection process was conducted in two stages: first, by identifying cases through digital medical records and a Microsoft Excel database; then, by analyzing the collected data. Sample size calculation was performed using Epi Info 7 software, considering a total population of 172 patients, a margin of error of 5%, and an expected frequency of 50%. Thus, a sample size of 84 patients was estimated for a confidence level of 80% and 154 patients for a confidence level of 99.99%.

Quantitative variables included age, weight, contrast dose administered, and serum creatinine levels. Qualitative variables were sex, hypertension, diabetes mellitus, dyslipidemia, smoking, anemia, pre-existing renal failure, exposure to nephrotoxic drugs, liver disease, type of vascular access (radial or femoral), and application of nephroprotection measures. Patients younger than 40 years or older than 80 years, those without documented renal function, and those without renal function follow-up during hospitalization were excluded from the analysis. Data were extracted from the hospital’s MHO and LABLINK medical record systems. A data collection spreadsheet was created in Microsoft Excel (version 2306). It included patient initials, age, sex, risk factors, use of nephrotoxic agents, type of vascular access, weight, serum creatinine levels with their corresponding clearance (at admission, at 48 hours, and at discharge), total administered contrast dose, and use of nephroprotection, which consisted of intravenous hydration with 0.9% saline solution, adjusted according to left ventricular ejection fraction. Creatinine clearance was calculated with the Cockcroft–Gault formula, using application Qx Calculate (version 2022), based on sex, age, weight, and serum creatinine. An iso-osmolar contrast medium (Ultravist 300®) was used.

The procedures were conducted by eight different operators. Variables were analyzed and reported as percentages, using formulas integrated into the Excel database. The study protocol was approved by the Research Ethics Committee of Hospital Dr. Guillermo Rawson. Data confidentiality was ensured pursuant to the Argentine Personal Data Protection Act (number 25,326), and the study followed the ethical principles of the Declaration of Helsinki and the ICH Good Clinical Practice guidelines. As this was a retrospective anonymized study, informed consent was not required.

Results

In this study, researchers analyzed a total population of 172 patients admitted to the Department of Cardiology and the Department of Hemodynamics to undergo cardiac catheterization (CC) in a setting of acute coronary syndrome (ACS) between June 1, 2021, and June 30, 2022. Table 1 shows the baseline characteristics according to the presence or absence of contrast-induced nephropathy (CIN) after emergency cardiac catheterization.

The sample consisted of 101 patients who presented with ACS and underwent CC, following the inclusion and exclusion criteria mentioned above.

Epidemiology

As regards to epidemiology, 81% of the patients (n=82) were men and 19% (n=19) were women.

Regarding age, 60% of the patients (n=61) were in the 40–60-year age group, and 40% (n= 40) were between 61 and 80 years of age, with a mean age of 58.3 years and a standard deviation of 8.3 (Figure 1).

Renal function

With regard to hospital admission, 92% of the patients (n=93) had normal renal function and 8% (n=8) had impaired renal function.

Among the 93 patients admitted with preserved renal function, 47% (n=44) developed contrast-induced nephropathy (CIN), whereas 53% (n=49) maintained preserved renal function at discharge (Figure 2).

Of the patients with CIN at discharge, 89% (n=39) were men and 11% (n=5) were women. Regarding age groups, among the 93 patients, 66% (n=29) were between 40 and 60 years of age, while 34% (n=15) were in the 61–80-year age group (Figure 3).

Contrast dose

Considering the administered contrast dose, among the 44 patients who developed contrast-induced nephropathy (CIN) at discharge, 55% (n=24) had been injected with 200 mL or more of iodinated contrast during coronary angiography, whereas 45% (n=20) had received less than 200 mL of it (Figure 4).

Risk factors

The risk factors associated with CIN in the 44 patients were hypertension (64%), diabetes mellitus (25%), dyslipidemia (30%), smoking (89%), anemia (16%), obesity (34%), nephrotoxic drugs (41%), and liver disease (2%) (Figure 5).

Nephroprotection

Finally, among the 44 patients with CIN at discharge, 70% (n=31) did not receive nephroprotection, whereas 30% (n=13) were prescribed hydration according to their ejection fraction as a nephroprotective measure (Figure 6).

Discussion

In general, 92% of the patients had preserved renal function at admission, while 47% showed deteriorating renal function at hospital discharge. It should be noted that only 30% of the patients who developed renal failure received nephroprotection measures, which was attributed to difficulties in administering fluid therapy, mainly due to ventricular dysfunction, reduced ejection fraction, low cardiac output, use of nephrotoxic drugs such as diuretics, ACE inhibitors or ARBs, anticoagulants, and lack of time for nephroprotection before the procedure.

These findings contrast with those reported in previous studies conducted in Argentina and Latin America, where the prevalence of contrast-induced nephropathy (CIN) ranges between 26% and 30%, suggesting a higher incidence in our study group, possibly related to the clinical characteristics of these patients and limitations in the implementation of preventive strategies.

Regarding the demographic profile, CIN predominantly affected men (88%), in agreement with the literature. However, there was a higher prevalence in the 40–61-year age group (63%), as opposed to what has been described in previous studies: a higher incidence in patients older than 75 years. Among modifiable risk factors, smoking (90%) and hypertension (65%) were the most frequent. While hypertension is consistent with previous reports, the incidence of smoking was higher than in earlier studies, in which dyslipidemia was usually more prevalent.

An exploratory multivariate analysis using logistic regression was performed, including variables that were significantly associated with CIN in the univariate analysis (p< 0.1). The use of nephrotoxic drugs (odds ratio [OR]: 5.18; 95% confidence interval [95% CI]: 1.61–16.7; p=0.006) and smoking (OR: 2.25; 95% CI: 1.00–5.05; p=0.050) were significantly associated with a higher risk of developing CIN. In contrast, the administration of nephroprotection measures had a significant protective effect (OR: 0.31; 95% CI: 0.13-0.76; p=0.010). Dyslipidemia and anemia also showed a trend toward association, although without reaching statistical significance.

Finally, it should be noted that 51% of the patients who developed CIN received over 200 mL of iodinated contrast during the procedure, in some cases exceeding the maximum recommended dose of 4 mL/kg, but without surpassing 300 mL, the absolute limit suggested by the literature. In all cases, the amount administered was clinically justified by procedural complexity and patient’s condition.

Conclusion

In this study regarding cardiac catheterization in acute coronary syndromes, contrast-induced nephropathy (CIN) was a frequent complication, which is associated with worse clinical outcomes. Nearly half of the patients developed renal deterioration despite having preserved renal function at admission. Smoking, anemia, and the use of nephrotoxic drugs were associated with a higher risk, while nephroprotection was insufficiently applied. Preventive strategies and prospective studies are required to confirm these findings.

Summary of key points

• Establish the use of nephroprotection protocols, evaluating which are the most effective (for example, adequate hydration and the administration of nephroprotective agents).

• Implement strategies to reduce the contrast dose used during the procedure while maintaining diagnostic quality.

• Ensure rigorous monitoring of renal function in the days following contrast administration to promptly detect any deterioration.

• Promote ongoing research on contrast-induced nephropathy and the collection of data to identify trends and areas for improvement.

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Prevalence and factors associated with contrast-induced nephropathy in patients with acute coronary syndrome undergoing emergency coronary angiography in a public hospital in San Juan

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