Increased Plasma Osmolar Gap Is Predictive of Contrast-Induced Acute Kidney Injury

Abstract

Contrast-induced acute kidney injury (CIAKI) is a common complication after percutaneous coronary artery intervention (PCI). It is urgent to find a novel, easily measurable and accurate predictor for the early detection of CIAKI. Hyperosmolarity and large amounts of contrast media are risk factors for CIAKI. However, there is no study on plasma osmolar gap as a predictor of CIAKI. We enrolled 89 patients undergoing elective PCI and tested changes of serum sodium, osmolar gap, and renal function at 0, 6, 12 and 24 hours. Plasma osmolar gap was calculated using the following formula: measured plasma osmolarity -[2(Na) + serum urea nitrogen/2.8 + glucose/18]. CIAKI was defined as follows: increase in serum creatinine of ≥ 50%, increase in serum creatinine of ≥ 0.3 mg/dL, or decrease in estimated glomerular filtration rate of ≥ 25% within 24 hours after PCI. The incidence of CIAKI was 13.5% (12/89 patients). The CIAKI group had higher plasma osmolar gaps 6 hours after PCI. The adjusted hazard ratio of the plasma osmolar gap from hour 6 (1-mOsm/L increments) to the development of CIAKI was 1.12 (95% confidence interval [CI], 1.01-1.26; P = 0.041). Sensitivity and specificity of 7 mOsm/L or higher plasma osmolar gap at hour 6 were 70.0% and 76.6%, respectively (area under the ROC curve = 0.77 [95% CI, 0.65-0.89]). Increased plasma osmolar gap may precede the development of CIAKI in patients undergoing PCI. In conclusion, plasma osmolar gap may be a useful predictor for the development of CIAKI.

Comment on “Association of Serum Osmolarity With Contrast-Induced Nephropathy in Patients With ST-Segment Elevation Myocardial Infarction”

“…Recently, Kim et al determined a relationship between CIN and osmolar gap. 2 The findings of these 2 studies support each other. However, we have some concerns about the methodology used in the Yildiz et al's study.…”

“…The osmolar gap is obtained by subtracting the osmolarity value calculated from the osmolality measured by an osmometer. 2 Increased ethanol, methanol, and some molecules in plasma may cause an elevated osmolar gap. 3 Osmolarity calculated by the formula often does not provide a directly measured osmolarity value.…”

“…3 Osmolarity calculated by the formula often does not provide a directly measured osmolarity value. 2,3 It is doubtful whether their patients consumed alcohol within 24 hours. Also, hyperlipidemia, hyperglycemia, and hypoproteinemia may result in low Na measurement, leading to calculate false low osmolarity.…”

A Simple Nomogram to Predict Contrast-Induced Acute Kidney Injury in Patients with Congestive Heart Failure Undergoing Coronary Angiography

“…However, many previous studies had limited the diagnosis time frame of CI-AKI to 48 hours, or even 24 hours [9,25]. In the study conducted by Kim et al, CI-AKI was defined as an increase in SCr of ≥50% or 0.3 mg/dL, or a decrease in eGFR of ≥25% within 24 hours after PCI [25]. e present simple nomogram was constructed based on age, AMI, IABP, and CKD, which are common risk factors associated with CI-AKI, as reported by numerous previous studies [12,26,27] 3) were identified as independent risk factors for CI-AKI [28].…”

A simple nomogram to predict contrast-induced acute kidney injury in patients with congestive heart failure undergoing coronary angiography

“…Moreover, we noticed that some patients were missing SCr data on day 3, which may lead to the underestimation of the incidence of CI-AKI. However, many previous studies had limited the diagnosis time frame of CI-AKI to 48 hours, or even 24 hours [9,25]. In the study conducted by Kim et al, CI-AKI was defined as an increase in SCr of ≥50% or 0.3 mg/dL, or a decrease in eGFR of ≥25% within 24 hours after PCI [25].…”