African American race, obesity, and blood product transfusion are risk factors for acute kidney injury in critically ill trauma patients

Abstract

Purpose

Acute kidney injury (AKI) is a common source of morbidity after trauma. We sought to determine novel risk factors for AKI, by Acute Kidney Injury Network (AKIN) criteria, in critically ill trauma patients.

Materials and Methods

A prospective cohort of 400 patients admitted to the intensive care unit of a level 1 trauma center was followed for the development of AKI over 5 days.

Results

Acute kidney injury developed in 147 (36.8%) of 400 patients. In multivariable regression analysis, independent risk factors for AKI included African American race (odds ratio [OR], 1.86; 95% confidence interval [CI], 1.08-3.18; P = .024), body mass index of 30 kg/m² or greater (OR, 4.72 versus normal body mass index; 95% CI, 2.59-8.61; P < .001), diabetes mellitus (OR, 3.26; 95% CI, 1.30-8.20; P = .012), abdominal Abbreviated Injury Scale score of 4 or more (OR, 3.78; 95% CI, 1.79-7.96; P < .001), and unmatched packed red blood cells administered during resuscitation (OR, 1.13 per unit; 95% CI, 1.04-1.23; P = .004). Acute Kidney Injury Network stages 1, 2, and 3 were associated with hospital mortality rates of 9.8%, 13.7%, and 30.4%, respectively, compared with 3.8% for those without AKI (P < .001).

Conclusions

Acute kidney injury in critically ill trauma patients is associated with substantial mortality. The findings of African American race, obesity, and blood product administration as independent risk factors for AKI deserve further study to elucidate underlying mechanisms.

Introduction

Injury results in over 170 000 deaths annually in the United States and is the leading cause of death among those 1 to 44 years old [1]. Acute kidney injury (AKI) is common and is associated with substantial mortality in critically ill populations in general [2] and in severely injured patients in particular [3], [4], [5]. Risk factors for AKI in trauma, however, have been incompletely studied.

Most prior studies of trauma-associated AKI used nonconsensus definitions of AKI [6], [7], [8], [9]. The establishment of the Risk, Injury, Failure, Loss, End-stage (RIFLE) criteria, and their subsequent modification by the Acute Kidney Injury Network (AKIN) provides a consensus definition for use in epidemiologic studies of AKI [10], [11]. This definition has been used in a variety of populations to identify risk factors in an effort to enhance both pathophysiologic understanding and stratification of risk for AKI [2], [12].

Our primary goal in this study was to identify novel risk factors for AKI in trauma patients, including both blunt and penetrating injury mechanisms, and doing so using all components of the AKI consensus criteria (creatinine, urine output, and need for renal replacement therapy). We used a cohort of prospectively enrolled critically ill trauma patients with detailed baseline data, followed for the first 5 days after intensive care unit (ICU) admission. Because the AKIN modifications of RIFLE have not been used to define AKI in prior trauma studies, we further sought to determine the association of AKIN-defined AKI and stage with mortality after severe injury.