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Kidney Week

Abstract: SA-PO163

Preoperative Low Urine Specific Gravity Levels Predict AKI After Cardiac Surgery

Session Information

Category: Acute Kidney Injury

  • 102 AKI: Clinical, Outcomes, and Trials

Authors

  • Jo, Wonji, Yonsei University College of Medicine, Seoul, Korea (the Republic of)
  • Ko, Byounghwi, Yonsei University College of Medicine, Seoul, Korea (the Republic of)
  • Jung, Chan-Young, Yonsei University College of Medicine, Seoul, Korea (the Republic of)
  • Joo, Youngu su, Yonsei University College of Medicine, Seoul, Korea (the Republic of)
  • Lee, Sangmi, Yonsei University College of Medicine, Seoul, Korea (the Republic of)
  • Kang, Shinchan, Yonsei University College of Medicine, Seoul, Korea (the Republic of)
  • Park, Jung Tak, Yonsei University College of Medicine, Seoul, Korea (the Republic of)
Background

Acute kidney injury (AKI) is a common and serious complication following cardiac surgery. However, strategies that could effectively stratify AKI risk before cardiac surgery are scarce. Recent investigations identified urinary osmolality to be associated with non-glomerular kidney damage in patients who are at higher risk for CKD progression. Patients with underlying kidney damage, although clinically insignificant, may be prone to cardiac surgery associated AKI. Hypothesizing that urine specific gravity (SG) could reflect kidney damage, the clinical implication of preoperative urine specific gravity on AKI occurrence after cardiac surgery was investigated in subjects with normal kidney function.

Methods

A total of 4135 patients who underwent coronary artery bypass or valve surgery at Yonsei University Health System from were enrolled. Patients whose eGFR was lower than 60mL/min/1.73m2 were excluded. Fasting urinary specific gravity was measured from the morning first void a day before the surgery. The patients were divided into tertiles based on urine specific gravity. The primary outcome was the incidence of AKI within 48hours of cardiac surgery. AKI was defined according to Acute Kidney Injury Network criteria.

Results

The mean age of the patients was 60 years and 60% were male. Diabetes consisted of 25.6% of the patients and 54.5% were hypertensive. The mean eGFR and urine SG was 98.8mL/min/1.73m2 and 1.020, respectively. AKI developed in 1,089 (26.3%) patients. The incidence of AKI was highest in the lowest urine SG tertile group (410, 29.0%) and lowest in the highest tertile group (304, 23.5%) (P < 0.001). Multivariable logistic regression analysis revealed that being included in the lowest preoperative urine SG tertile group was significantly related with higher post cardiac surgery AKI incidence risk (odd ratio (OR), 1.33; CI, 1.12-1.57; P =0.001). This association was significant even after adjustments were made for confounding factors.

Conclusion

Low urine SG was associated with increased risk of cardiac surgery associated AKI in patient with normal renal function. Evaluating preoperative urine SG may be useful in stratifying post cardiac surgery AKI risk.