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Saudi Journal of Kidney Diseases and Transplantation
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Table of Contents   
ORIGINAL ARTICLE  
Year : 2011  |  Volume : 22  |  Issue : 3  |  Page : 464-470
Acute kidney injury in intensive care unit: Incidence, risk factors and mortality rate


1 Department of Nephrology, Hormozgan University of Medical Sciences and Health Services, Hormozgan, Iran
2 Department of Internal Medicine, Hormozgan University of Medical Sciences and Health Services, Hormozgan, Iran
3 Department of Internal Medicine, Iran University of Medical Sciences and Health Services, Tehran, Iran
4 Medical Sciences/University of Tehran, Tehran, Iran

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Date of Web Publication7-May-2011
 

   Abstract 

Acute kidney injury (AKI) is a risk factor for increased mortality in critically ill patients. To assess the incidence, risk factors and outcome of patients who develop AKI in the intensive care units (ICUs), we retrospectively studied 235 patients admitted to the ICU of Shahid Mohamadi Hospital, Hormozgan, Iran, and compared those who developed AKI and those who did not. There were 31.1% of patients who developed AKI during ICU admission. There was a significant difference in the mean age, serum sodium (Na), potassium (K), urea, blood urea nitrogen (BUN) and creatinine (Cr) levels and also platelets, on admission, between patients with and without AKI. Acute physiology and chronic health evaluation (APACHE) II score on admission was significantly higher in AKI patients and Glasgow coma scale (GCS) was significantly lower. The mortality of AKI patients (72.6%) was significantly higher than non-AKI patients (25.91%). The number of underlying diseases and GCS and APACHE II score on admission were significantly different between the expired and survived patients. We conclude that age, first serum K level and APACHE II score on admission time were powerful independent predictors of developing AKI in ICU patients. The GCS on admission and the presence of two or more underlying diseases accurately predict the mortality in AKI positive ICU patients.

How to cite this article:
Samimagham HR, Kheirkhah S, Haghighi A, Najmi Z. Acute kidney injury in intensive care unit: Incidence, risk factors and mortality rate. Saudi J Kidney Dis Transpl 2011;22:464-70

How to cite this URL:
Samimagham HR, Kheirkhah S, Haghighi A, Najmi Z. Acute kidney injury in intensive care unit: Incidence, risk factors and mortality rate. Saudi J Kidney Dis Transpl [serial online] 2011 [cited 2019 Aug 21];22:464-70. Available from: http://www.sjkdt.org/text.asp?2011/22/3/464/80481

   Introduction Top


Acute kidney injury (AKI) is a complex disorder that occurs in a variety of settings, with clinical manifestations ranging from a minimal elevation in serum creatinine to anuric renal failure. [1]

AKI is a common complication in patients admitted to the intensive care unit (ICU) and numerous causes are responsible for its development. [2] Moreover, it occurs as a part of a multiple organ dysfunction syndrome or as a separate event.

The AKI incidence in ICU patients varies widely from 3 to 30%, [3],[4],[5] with mortality ranging from 36 to 90%, [4],[5],[6] depending on the type of ICU, study population, the period during which the study is conducted, and the criteria used to define AKI.

The relative importance of factors contributing to AKI varies according to the underlying pathology and patients' characteristics. Several risk factors involved in the genesis of AKI have been analyzed in the medical literature, including obstetric bleeding and digestive hemorrhage, sepsis, shock, infections, use of contrast, and drug toxicity. [3],[6]

There have been many studies about the epidemiology and risk factors of AKI in critically ill patients in the different regions of the world. [3],[7],[8],[9] However, little data on the risk factors for development of AKI in critically ill patients are available in our country.

The aim of the present study was to assess the incidence, risk factors, and outcome of patients who develop AKI in our ICU.


   Materials and Methods Top


The medical records of 263 patients admitted in the ICU of Shahid Mohamadi Hospital, Hormozgan, Iran, between May 2005 and May 2006, were reviewed retrospectively. Ethics committee of the Medical Faculty of Bandarabbas University of Medical Sciences reviewed and approved the study protocol. Patients with incomplete data, history of renal transplantation and chronic renal failure were excluded.

We evaluated the demographic data, duration of admission, causes for ICU admission, underlying diseases (pre-existing chronic disease, co-morbid conditions and organ failures developed during ICU stay), history of trauma and surgery, Glasgow coma scale (GCS) on admission, and acute physiology and chronic health evaluation (APACHE) II score on admission with their respective death risk [10] as well as laboratory data on admission. The laboratory investigations included white blood cell (WBC), hemoglobin (Hb), platelet (Plt), blood urea nitrogen (BUN), serum creatinine (Cr), and electrolytes.

The patients were classified into two groups: those who developed AKI at any time during their ICU stay and those who did not. AKI was defined as increment of serum creatinine >0.3 mg/dL or 50% from baseline within 48 hours or urine output <0.5 mL/kg/hour for >6 hours despite fluid resuscitation when applicable. [11]


   Statistical Analysis Top


Statistical analysis was performed using SAS 9.1 database. The quantitative variables were reported as means ± SD and the qualitative variables as percentage. The Chi-square test and Student's "t" test were used in the univariate analysis of the risk factors and the comparison of the subgroups. The Mantel-Haenszel Chi-square test for trend was also used. The adjusted odds ratio with 95% confidence intervals (CIs) was calculated as an estimate of the relative risks when a statistically significant difference was found between the compared frequencies. All the variables with a P value <0.15 in the univariate analysis were selected for multivariate analysis. The logistic regression forward method was used for multivariate analysis of the risk factors, and the results were tabulated as odds ratio (OR) and confidence interval. The level of significance was set at P < 0.05.


   Results Top


Of the 265 patients screened, analysis was performed on the data of 235 patients who had complete history, clinical findings, and lab data.

The age of the participants ranged from 5 to 106 years (mean 39.5 ± 21.2); 177 (75.3%) were males and 58 (24.7%) were females. The means of age of the male and female patients were 39.1 ± 21.0 and 40.9 ± 22.0 years, respectively. The demographic features of the study patients are shown in [Table 1].
Table 1: Demographic features of the study population.

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There were 73 (31.06%) patients who developed AKI during the admission time; 52 (71.2%) of them were males. On the basis of univariate analysis, there was a significant difference in the mean age between the patients with and without AKI (P = 0.01). There was no difference in the development of AKI among post-traumatic (122) and non-traumatic (111) cases; AKI developed in 27.9% of the traumatic versus 24.4% of the non-traumatic cases (P = 0.26). There was also a significant trend toward an increasing number of AKI cases in the older age group (P = 0.03). The patients who developed AKI had a significantly higher Na, K, urea, BUN, and Cr, but significantly lower Plt on admission time (P < 0.05) [Table 2].
Table 2: Univariate analysis of the risk factors for development of AKI in ICU.

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The mean ICU stay of AKI patients was longer than that of the non-AKI patients (10.6 ± 9.69 days vs. 7.80 ± 6.67 days, P = 0.02). The APACHE II score on admission to the ICU was significantly higher in the AKI patients (23.9 ± 8.18 vs. 14.8 ± 6.82, P = 0.00), and the GCS was significantly lower (P = 0.00). In addition to the leading cause of admission to the ICU, 147 (58.1%) patients had one or more underling diseases including pre-existing chronic disease (neoplasm, hypertension, diabetes mellitus, obstructive and restrictive lung diseases, cardiovascular diseases, connective tissue disorders and neurologic disorders). The complications that developed during the ICU stay included sepsis, myocardial infarction, seizure, fat emboli, plural effusion, pulmonary edema. We observed a significant trend toward an increased number of AKI cases with the increased number of the underlying diseases (P = 0.01).

The multivariable-adjusted odds ratios in a stepwise logistic regression model were 3.8 for age (CI 95% = 1.7-8.4, P = 0.00), 1.7 for first K + level (CI 95% = 1.1-2.7, P = 0.00), and 1.1 for APACHE II score (CI 95% = 1.1- 1.2, P = 0.00) [Table 3].
Table 3: Odds ratio of independent risk factors of AKI development, multivariate analysis.

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During the ICU stay, 95 out of 235 (40.1%) patients expired. The mortality of the AKI patients (n = 53, 72.6%) was significantly higher than non-AKI patients (n = 42, 25.9%). According to the univariate analysis, the number of underlying diseases, the GCS and APACHE II score on admission to the ICU were significantly higher in the expired patients; the first Plt levels were significantly lower in this group (P < 0.05) [Table 4],[Table 5].
Table 4: Univariate analysis of the risk factors of mortality in the AKI ICU patients.

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Table 5: Odds ratio of independent risk factors of mortality, multivariate analysis.

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Multivariable-adjusted odds ratios in stepwise logistic regression model was 0.5 for the GCS (CI 95% = 0.3-0.7, P = 0.00) and 9.3 for the number of underlying diseases (CI 95% = 1.2- 67.7, P = 0.01). So, the GCS on admission to the ICU and the presence of two or more underlying diseases were considered as independent risk factors of mortality in the AKI patients admitted to the ICU.


   Discussion Top


The analysis of our study patients demonstrated that the age of the patients, the first K + level, and the APACHE II score on admission to the ICU were independent risk factors for development of AKI. Low GCS on admission and having one or more underlying diseases were independent risk factors for increased mortality risk in AKI patients.

The incidence of AKI in our ICU was higher than that reported in other similar studies. [6],[3] It may be explained by the difference in populations and risk factors such as age, cause of ICU admission and underlying diseases, or by the non-uniform criteria used for definition of AKI in different studies. The criteria adopted in our study were based on a rather wide definition with high sensitivity in order to detect as large a number of patients as possible. The AKI in critically ill patients results in high mortality rates. [3],[12] The risk factors for the development of AKI in the ICU patients include age and underlying diseases. [3],[13] Consistently, our data demonstrated a significant trend toward an increased number of AKI cases with an increased number of underlying diseases and older age. AKI more frequently developed in patients of age 30-60 years. However, the underlying diseases were not independent risk factors for the development of AKI.

In comparison with other studies, [12],[14],[15] the mean APACHE II score and its respective death risk during the first 24 hours was an independent risk factor in our study.

As demonstrated previously, [3],[12] the rate of AKI development was the same in either sex. Duration of ICU stay for the AKI patients was relatively lower compared with that reported in some studies [16] but was the same as that reported in some others. [17],[18] Although ICU stay was significantly higher in the AKI patients, this variable did not remain significant in our stepwise logistic model.

Low GCS on admission results in a high incidence of AKI in the ICU patients. It was also reported previously, [19] especially in GCS <8. The GCS did not also remain significant in our stepwise logistic model. It could be as a result of its strong correlation with APACHE II score, detected as an independent risk factor.

Few studies have assessed the impact of surgical complications on incidence of AKI in spite of their potential as risk factors. [20],[21],[22] However, we could not show such associations.

Laboratory findings have not been previously investigated enough as risk factors of AKI. Although it did not remain significant in the multivariate analysis, the small difference in the levels of BUN and Cr on admission to ICU was highly significant. Hypotension or hypovolemia could have contributed. This fact may have clinical implications since a patient admitted to the ICU with slightly elevated BUN and Cr levels must be considered and treated as a patient at risk to develop AKI. The highly significant difference in Cr levels of these two groups was also reported previously. [12] The only laboratory variable that remained significant in the multivariate analysis was the plasma K + levels, which was reported previously as an independent predictor of AKI severity in the ICU patients. [12] However, as the other electrolyte disorders, the high plasma K + levels may be a consequence of an already developed renal failure.

In our study, the mortality rate was three times higher in those with AKI than in those without AKI. The 77.6% ICU mortality rate of the AKI patients in our study was higher than that quoted in the literature. [23],[24]

There is a wide range of mortality rates reported from 36 to 90% [4],[5],[6] and this could be secondary to a wide variation in the patients' characteristics and practice patterns across the health centers. The factors mostly associated with the mortality in the AKI patients included the number of underlying diseases and GCS and APACHE II score on admission. The first two were independent risk factors.

In conclusion, older age, the first K + le-vels and the APACHE II score on admission to the ICU were powerful independent predictors for development of AKI in the ICU patients. Furthermore, the GCS on admission and the presence of two or more underlying diseases accurately predicted mortality in the AKI patients.


   Acknowledgments Top


The authors would like to thank Farzan Institute for Research and Technology for their technical assistance.

 
   References Top

1.Mehta RL, Kellum JA, Shah SV, et al. Acute Kidney Injury Network. Acute Kidney Injury Network: report of an initiative to improve outcomes in acute kidney injury. Crit Care 2007;11(2):R31.  Back to cited text no. 1
    
2.Klahr S, Miller SB. Acute oliguria. N Engl J Med 1998;338 (10):671-5.  Back to cited text no. 2
    
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4.Hoste EA, Lameire NH, Vanholder RC, et al. Acute renal failure in patients with sepsis in a surgical ICU: predictive factors, incidence, co-morbidity, and outcome. J Am Soc Nephrol 2003;14(4):1022-30.  Back to cited text no. 4
    
5.Bernieh B, Al Hakim M, Boobes Y, et al. Outcome and predictive factors of acute renal failure in the intensive care unit. 1: Transplant Proc 2004; 36 (6):1784-7.  Back to cited text no. 5
    
6.Guerin C, Girard R, Selli JM, et al. Initial versus delayed acute renal failure in the intensive care unit. A multicenter prospective epidemiological study. Rhone-Alpes Area Study Group on Acute Renal Failure. Am J Respir Crit Care Med 2000;161(3 Pt 1):872-9.  Back to cited text no. 6
    
7.Cole L, Bellomo R, Silvester W, et al. A prospective, multicenter study of the epidemiology, management, and outcome of severe acute renal failure in a "closed" ICU system. Am J Respir Crit Care Med 2000;162 (1):191-6.  Back to cited text no. 7
    
8.Fiaccadori E, Maggiore U, Lombardi M, et al. Predicting patient outcome from acute renal failure comparing three general severity of illness scoring systems. Kidney Int 2000; 58(1): 283-92.  Back to cited text no. 8
    
9.Silvester W, Bellomo R, Cole L. Epidemiology, management, and outcome of severe acute renal failure of critical illness in Australia. Crit Care Med 2001; 29(10):1910-5.  Back to cited text no. 9
    
10.Knaus WA, Draper EA, Wagner DP, et al. APACHE II: a severity of disease classification system. Crit Care Med 1985;13(10):818-29.  Back to cited text no. 10
    
11.Barrantes F, Tian J, Vazquez R, Amoateng-Adjepong Y, Manthous CA. Acute kidney injury criteria predict outcomes of critically ill patients. Crit Care Med 2005; 36 (5):1397-403.  Back to cited text no. 11
    
12.Mataloun SE, Machado FR, Senna AP, et al. Incidence, risk factors and prognostic factors of acute renal failure in patients admitted to an intensive care unit. Braz J Med Biol Res 2006; 39 (10):1339-47.  Back to cited text no. 12
    
13.Mangano CM, Diamondstone LS, Ramsay JG, et al. Renal dysfunction after myocardial revascularization: risk factors, adverse outcomes, and hospital resource utilization. The Multi-center Study of Perioperative Ischemia Research Group. Ann Intern Med 1998;128 (3):194-203.  Back to cited text no. 13
    
14.Abosaif NY, Tolba YA, Heap M, et al. The outcome of acute renal failure in the intensive care unit according to RIFLE: model application, sensitivity, and predictability. Am J Kidney Dis 2005; 46 (6):1038-48.  Back to cited text no. 14
    
15.Ho KM, Dobb GJ, Knuiman M, et al. A comparison of admission and worst 24-hour Acute Physiology and Chronic Health Evaluation II scores in predicting hospital mortality: a retrospective cohort study. Crit Care 2006;10 (1):R4.  Back to cited text no. 15
    
16.Hegarty J, Middleton RJ, Krebs M, et al. Severe acute renal failure in adults: place of care, incidence and outcomes. QJM 2005;98(9):661-6.  Back to cited text no. 16
    
17.Fischer MJ, Brimhall BB, Lezotte DC, et al. Uncomplicated acute renal failure and hospital resource utilization: a retrospective multicenter analysis. Am J Kidney Dis 2005;46(6):1049-57.  Back to cited text no. 17
    
18.Mehta RL, Pascual MT, Soroko S, et al. Program to Improve Care in Acute Renal Disease. Spectrum of acute renal failure in the intensive care unit: the PICARD experience. Kidney Int 2004;66(4):1613-21.  Back to cited text no. 18
    
19.Miraoui W, Mebazaa M, Frikha N, et al. Isolated acute renal failure is not associated to an increase in mortality of patients in intensive care units. Tunis Med 2004;82(11):996-1000.  Back to cited text no. 19
    
20.Sanchez EQ, Gonwa TA, Levy MF, et al. Pre-operative and perioperative predictors of the need for renal replacement therapy after orthotopic liver transplantation. Transplantation 2004;78(7):1048-54.  Back to cited text no. 20
    
21.Regner KR, Connolly HM, Schaff HV, et al. Acute renal failure after cardiac surgery for carcinoid heart disease: incidence, risk factors, and prognosis. Am J Kidney Dis 2005;45(5): 826-32.  Back to cited text no. 21
    
22.Bove T, Calabrò MG, Landoni G, et al. The incidence and risk of acute renal failure after cardiac surgery. J Cardiothorac Vasc Anesth 2004;18(4):442-5.  Back to cited text no. 22
    
23.Lombardi R, Zampedri L, Rodriguez I, et al. Prognosis in acute renal failure of septic origin: a multivariate analysis. Ren Fail 1998;20(5): 725-32.  Back to cited text no. 23
    
24.Vivino G, Antonelli M, Moro ML, et al. Risk factors for acute renal failure in trauma patients. Intensive Care Med 1998;24(8):808-14.  Back to cited text no. 24
    

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Correspondence Address:
Hamid Reza Samimagham
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Iran
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