Introduction: Acute kidney injury (AKI) is a common problem in hospitalized patients, requiring extensive treatment and carries a high mortality rate. This study was designed to assess the epidemiology of AKI, and risk factors and outcome of patients with severe AKI in a tertiary care university hospital in Iceland.

Material and methods: All adult patients with measured serum creatinine (SCr) in Landspitali University Hospital from January 2008 to December 2011, who had a measured baseline SCr in the preceeding six months, were included. Patients were categorized according to the RIFLE-criteria into risk (stage 1), injury (stage 2) and failure (stage 3) groups based on their highest SCr, using the lowest SCr in the previous six months as baseline.

Results: A total of 17,693 individuals (out of 74,960) had a baseline SCr and their data were used for analysis. AKI occured in 3,686 (21%) with 12%, 5% and 4% of stage 1, 2 and 3, respectively. There were more females in stage 1 and stage 2 and more males in stage 3 (p< 0.001). Contributing causes for AKI in patients with stage 3 AKI were surgery (22%), circulatory shock (23%), sepsis (14%), cardiovascular insult (32%), respiratory failure (27%), bleeding (10%), trauma (7%) and AKI associated drugs (61%). Dialysis was required in 11% and in 0.7% for longer than 30 days but none > 90 days. One year survival was 52%.

Conclusions: Acute kidney injury is common in Iceland and the prognosis of those with severe AKI is dismal. Majority of those patients were taking drugs that increase risk of AKI, providing a target for preventive measures.

Figures and tables:

Figure 1 - Flowchart showing the number of patients with creatinine measurements, how many had a measured baseline and their distribution into stage 1 (risk), stage 2 (injury) and stage 3 (failure) groups. AKI: Acute kidney injury. LUH: Landspitali – The National University Hospital of Iceland. 

Figure 2 - Kaplan-Meier plot demonstrating the survival of patients with acute kidney injury in the stage 3 (failure) group of the RIFLE classification. One year survival was 52%.

Table I. RIFLE classification criteria for acute kidney injury.
Category		Criteria
R	Stage 1	Baseline x 1,5 or UO <0.5mL/kg/hour for 6 hours
I	Stage 2	Baseline x 2 or UO <0.5mL/kg/hour for 12 hours
F	Stage 3	Baseline x 3 or UO <0.3mL/kg/hour for 24 hours
L		Renal replacement therapy> 4 weeks
E		Renal replacement therapy> 90 days

The RIFLE classification is based on three categories and two outcomes. R=risk (stage 1), I=injury (stage 2), F=failure (stage 3), L=loss, E=end stage. Baseline refers to baseline creatinine value, UO= urinary output

 

Table II. Patient data.
	Non-AKI	Risk Stage 1	Injury Stage 2	Failure Stage 3
Number (%)	14.017 (79.2)	2.077 (11.7)	840 (4.7)	769 (4.3)
Age (years)	56.6±19.5	67.2±18.3	70.3±15.0	69.2±15.5
Female (%)	54.6	54.3	53.1	41.5

AKI= Acute kidney injury. Age is median± standard deviation.

 

Table III.  Comparison of admitted patients and outpatients with stage 3 acute kidney injury
	Admitted (n=613)	Outpatients (n=80)	p-value
Age (years)	69.3±15.4	65.8±16.4	<0.001*
Female (%)	41.6	42.5	0.953
Baseline creatinine (mmól/L)	84 (20-1787)	188 (25-943)	0.002*
Hypertension	199 (32.5%)	31 (38.8%)	0.261
Ischemic heart disease	203 (33.1%)	19 (23.8%)	0.091
Chronic kidney disease	119 (19.4%)	29 (36.3%)	0.001*
Diabetes	105 (17.1%)	12 (15.0%)	0.633
COPD	83 (13.5%)	7 (8.8%)	0.231
Chronic liver failure	16 (2.6%)	3 (3.8%)	0.557

COPD= Chronic obstructive pulmonary disease, Diabetes= diabetes mellitus type I and II. Age is median ± standard deviation. Baseline refers to median (range) baseline serum creatinine value. *Statistically significant.

 

Table IV. Causes and risk factors of acute kidney injury in patients with stage 3 (n=693).
Risk factor	n	(%)
Surgery	150	(22)
Shock	162	(23)
Sepsis	99	(14)
Cardiovascular insult	222	(32)
Bleeding	72	(10)
Respiratory failure	188	(27)
Trauma	48	(7)
Medication	424	(61)
·         NSAID	292	(42)
·         Contrast	15	(2)
·         ACEi/ARB	204	(29)
·         Narcotics	13	(2)
·         Overdose	18	(3)

The frequency of use of medications that increase the risk of acute kidney injury. NSAID = non-steroidal anti-inflammatory drug, ACEi= angiotensin-converting-enzyme inhibitor,ARB=angiotensin receptor blocker.

 

Key words: Acute kidney injury, survival, RIFLE criteria, risk factors, comorbid diseases.

Correspondence: Gísli H. Sigurðsson, gislihs@landspitali.is

Long ThE1, Sigurdsson MI2, Indridason OS3, Sigvaldason K2, Sigurdsson GH1,2

¹Faculty of Medicine, University of Iceland, ²Department of Anesthesia and Intensive Care, ³Division of Nephrology, Landspítali - The National University Hospital of Iceland, Reykjavík.