Acute Kidney Injury
Table 3: Candidate Variables Previously Associated with an Increased or Decreased Risk of Acute Kidney Injury Following Cardiac Catheterisation in a Multivariate Analysis
Demographics Age6,11,19,21,33,37,44,45,50 Race2
Gender12,38,39
Past medical history Anaemia11,21,51
Chronic kidney disease11,21,33,37,38,43–45
Congestive heart failure6,11,19–21 Diabetes2,6,11,12,19–21,33,37,38,43–45,51 Dyslipidaemia2
Hypertension20,38,51
Peripheral vascular disease2,6,20,43 Prior stroke2
↓Left ventricular ejection fraction12,20,44,45,51 Hypoalbuminaemia11 Mitral regurgitation33
Procedural Contrast type12,43,51,84
Contrast volume2,6,11,20,21,37,39,45,50,51 Shock/hypotension*21
Time to reperfusion ≥6 hours50 Arterial entry site repair2
Use of furosemide39
Vessel lesion location6,37 Pulmonary oedema2 Procedural success37 Neurological event2
Risk factors that are ascertainable or occur only during the cardiac catheterisation are represented in the ‘Procedural’ section.
*Shock/hypotension can occur during clinical presentation before or during the procedure. ↓ = abnormaly low.
Patient Demographics
While patient demographic characteristics are not modifiable, they are significant risk factors for the development of post-procedural AKI and can inform the need for pre-procedural prophylaxis. The most pronounced of these is advancing age. Some risk assessments are cut-offs, typically between 70 and 80 years of age, while others calculate risk per decade.21,33,37
Significant variation in the odds ratios
for age is partially explained by the heterogeneity in the coding of advanced age and the populations studied. In addition, age is one of the variables most likely to be confounded by unmeasured risk factors, which are more prevalent with advancing age.
Another emerging demographic consideration is gender. Female patients have been shown to be at elevated risk of development of post-procedural AKI among a number of studies.12,19,38
and 19.8 versus 13.6 % (p=0.004),39 respectively.
The dose response nephrotoxicity of contrast has been widely studied, but is difficult to assess from a risk magnitude perspective because of the numerous agents used, as well as a large number of binary and continuous variable definitions used in studies.2,6,11,20,21,37,39,45,50,51
In studies that
retained gender as a multivariable risk factor, the unadjusted AKI incidence rate differences between females and males were 23.6 versus 17.4 % (p<0.0001)38
Chronic Kidney Disease
Pre-existing CKD is the single strongest AKI risk factor for patients undergoing cardiac catheterisation and is defined as an estimated GFR <60 ml/min/1.73 m2, measured by the modification of diet in renal disease (MDRD) equation.20,21
has steadily increased during recent years, which has lead to an increased number of these patients undergoing cardiac catheterisation.40
post-procedural AKI.41,42 118
About 10 % of patients with CKD will experience Almost all observational cohort studies have
The volume of radiocontrast dye can be reduced by avoiding an left ventriculogram (LV-gram) study during the procedure and rationing the dye through the use of automated contrast injectors.
The number of patients with CKD
Because of the strong association with the outcome, administration of contrast dye has been particularly problematic for pre-procedural risk prediction and risk adjustment. While the type can be chosen prior to the procedure, the volume is unknown pre-procedurally and difficult to estimate because the patient’s coronary anatomy is unknown. In order to limit exposure and better estimate patient risk from contrast administration prior to the procedure, Cigarroa and colleagues proposed a maximum acceptable contrast dose (MACD) to calculate a tailored safe dose of contrast based on the pre-procedure serum creatinine (or eGFR) and body weight (kg).52
Subsequent studies have
confirmed that exceeding the calculated MACD resulted in significantly increased risk of AKI.53,54
For pre-procedural risk assessment and EUROPEAN NEPHROLOGY Clinical Presentation Shock/hypotension*6,11,21,43,51
Creatinine/glomerular filtration rate6,12,19–21,37,44,45,51 C-reactive protein82
Acute myocardial infarction6,33,50 Urgency status19,20
Intra-aortic balloon pump use11,20,21,37,50,51,83 Volume depletion11 Pulmonary oedema51 Unstable angina2
Hydration protocol45
Recent prior procedure44 Hypertension45
noted significant associations between CKD and the development of post-procedural AKI.11,21,33,37,38,43–45
However, keep in mind that
approximately two-thirds of patients developing AKI present to cardiac catheterisation with normal or near-normal renal function (eGFR >60 ml/min/1.73 m2).
Diabetes
Diabetes is consistently associated with post-procedural AKI and risk-adjusted odds ratios (ORs) range from 1.5 to 3.5 across heterogeneous cohorts and outcomes.19,21
Most of the analyses
have defined this as the simple presence or absence of the disease state, which is not modifiable. However, serum glucose concentrations are modifiable and a recent study demonstrated that hyperglycaemic patients without known diabetes experienced elevated risk of post-procedural AKI when their pre-procedural serum glucose levels were above 110 mg/dl.46
The risk was most
pronounced for levels above 200 mg/dl (OR 2.14, 95 % 1.46–3.14). While patients with known diabetes did not experience the same risk escalation with increasing glucose, hyperglycaemia occurs in over 40 % of acute myocardial infarction patients, half of whom do not have known diabetes, so this represents a potentially significant risk factor for a substantial number of patients.47,48
It is not yet known
whether interventions to lower hyperglycaemia are protective. Procedural Factors
Procedural factors that are predictive of AKI include acuity, acute myocardial infarction, hypotension or shock, intra-aortic balloon pump use, type and volume of radiocontrast dye. While the above listed factors are predominately non-modifiable and can be used to assess the risk of the patient in developing post-procedure AKI, the type and volume of radiocontrast dye can be modified.
Radiocontrast Dye
Radiocontrast dyes are believed to be nephrotoxic through acute vasoconstriction and reduced renal perfusion, resulting in localised hypoxia and tubular cytotoxicity.49
Both the type of contrast and
the volume administrated have been shown to be associated with post-procedural AKI.
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