Serum creatinine role in predicting outcome after cardiac surgery beyond acute kidney injury

Table 1 Definition and classification for acute kidney injury

	Serum creatinine/GFR criteria	Urine output criteria
RIFLE classification
Definition	SCr rise ≥ 1.5 times baseline or GFR decrease > 25% within 7 d
Staging	R (Risk) SCr rise up to 2 times baseline or GFR decrease > 25%	< 0.5 mL/kg per hour for ≥ 6 h
	I (Injury) SCr rise up to 3 times baseline or GFR decrease > 50%	< 0.5 mL/kg per hour for ≥ 12 h
	F (Failure) SCr rise 3 times baseline or more or GFR decrease > 75% or absolute SCr ≥ 4 mg/dL with acute rise ≥ 0.5 mg/dL	< 0.5 mL/kg per hour for ≥ 24 h or anuria ≥ 12 h
	L (Loss) persistent AKI > 4 wk, need for RRT
	E (ESRD) persistent loss > 3 mo, need for dialysis
AKIN classification
Definition	SCr rise ≥ 1.5 times baseline or ≥ 0.3 mg/dL within 48 h
Staging	1 SCr rise up to 2 times baseline or ≥ 0.3 mg/dL	< 0.5 mL/kg per hour for ≥ 6 h
	2 SCr rise up to 3 times baseline	< 0.5 mL/kg per hour for ≥ 12 h
	3 SCr rise 3 times baseline or more or absolute SCr ≥ 4 mg/dL with acute rise ≥ 0.5 mg/dL or need for RRT	< 0.3 mL/kg per hour for ≥ 24 h or anuria ≥ 12 h
KDIGO classification
Definition	SCr rise ≥ 1.5 times baseline within seven days or ≥ 0.3 mg/dL within 48 h or oliguria
Staging	1 SCr rise up to 2 times baseline or ≥ 0.3 mg/dL
	2 SCr rise up to 3 times baseline
	3 SCr rise 3 times baseline or more or absolute SCr ≥ 4 mg/dL with acute rise ≥ 0.5 mg/dL or need for RRT

GFR: Glomerular filtration rate; AKIN: Acute Kidney Injury Network; KDIGO: Kidney Disease: Improving Global Outcomes; RIFLE: An acronym for Risk of renal failure, Injury to the kidney, Failure of kidney function, Loss of kidney function and End-stage renal failure; SCr: Serum creatinine; AKI: Acute kidney injury; RRT: Renal replacement therapy.

Table 2 Risk factors for acute kidney injury

Preoperative	Intraoperative
Patient related	Patient related
Renal dysfunction/high SCr1	Low venous compliance
Advanced age	Low systemic vascular resistance
Female gender	Autoregulatory systems disturbances
NYHA FC IVReduced LVEF or CHF	Low output syndrome(pressor/IABP need)
Left main CAD	Type of surgery
Diabetes mellitus	Valvular
Poor glycemic control	Re do surgery
Peripheral vascular disease	Emergency
COPD
Coexisting liver disease
Preoperative IABP
Pulmonary rales
Genetic predisposition
Modifiable	Procedure related3
Extremes of SBP2	On-pump cardiac surgery
Sepsis2	Nonpulsatile flow on CPB
Medications (NSAID, ARB)	Hypothermic CPB
Contrast dye	Deep hypothermic circulatory arrest
	Duration of CPB (> 100-120 min)
	Perfusion pressure
	Hemodilution during CPB
	Blood transfusion
	Hemolysis
	Embolism

¹Risk factors with higher level of evidence are in bold;

²both patient related and modifiable;

³and also modifiable. NYHA FC IV: New York Heart Association Function class IV; LVEF: Left ventricle ejection fraction; CHF: Congestive heart failure; CAD: Coronary artery disease; COPD: Chronic obstructive pulmonary disease; IABP: Intra-aortic balloon pump; SBP: Systolic blood pressure; NSAID: Nonsteroidal anti-inflammatory drug; ARB: Angiotensin receptor blockers; CPB: Cardiopulmonary bypass; SCr: Serum creatinine.

Table 3 Potential preventive measures and pharmacological interventions in acute kidney injury

Preventive measures

Avoidance of nephrotoxic drugs

Angiotensin-converting enzyme inhibitors

Angiotensin receptor blockers

Hydration

Glycemic control

Maintenance of renal perfusion

Goal directed therapy

Ischemic preconditioning

Prevention of CI-AKI

Hydration

N-acetyl cysteine

Bicarbonate

Timing of surgery

Pharmacological interventions

Fenoldopam

Nesiritide

Sodium bicarbonate

Mannitol

Atrial natriuretic peptide

Brain-type natriuretic peptide

Early postoperative renal replacement therapy

Continuous renal replacement therapy

Ultrafiltration

CI-AKI: Contrast induced acute kidney injury.