RESULTS
A total of 170 patients were included in the study (98 men, 57.6%). The median age was 73 (range, 18–95) years. All patients had infections caused by extremely drug-resistant gram-negative bacterial infections. The causative bacteria were Acinetobacter baumannii (78.2%),Klebsiella pneumonia (15.9%), and Pseudomonas aeruginosa(5.9%). One hundred eight (78.2%) patients had lower respiratory tract infection, 48 (28.2%) had blood stream infection, 8 (4.7%) had surgical site infection, and 6 (3.5%) had urinary tract infection.
Nephrotoxicity was detected in 106 (62.4%) patients. According to the RIFLE classification, 18 (10.6%) patients were evaluated in the ‘risk’ group, 36 (21.2%) patients in the ‘injury’ group, and 52 (30.6%) patients in the ‘failure’ group. Sixty-four patients had no risk factors for the development of nephrotoxicity. Five (4.7%) of the patients who developed nephrotoxicity required hemodialysis. Nephrotoxicity classification of elderly and young patients according to the RIFLE score is shown in Figure 1.
The median (minimum-maximum) age of the patients who developed nephrotoxicity was 75 (19-95) and 50% were male. The duration of hospitalization before COL therapy was similar in patients with and without nephrotoxicity (p=0.109). The prevalence of chronic obstructive pulmonary disease (COPD) was significantly higher in the nephrotoxicity group (p=0.02), but there was no significant difference between the two groups in terms of other comorbid diseases. Initial serum urea and creatinine levels were significantly higher in the nephrotoxicity group (p<0.001). APACHE II score, vasopressor agent use, concomitant nephrotoxic agent use, 28-day mortality, and overall mortality rates were also higher in the nephrotoxicity group (p<0.05). The demographic, clinical, and laboratory characteristics of patients based on nephrotoxicity are given in Table 1.
In multivariable logistic regression analysis, advanced age (odds ratio [OR]=1.043; 95% confidence interval [CI]: 1.018-1.068; p=0.001) and initial serum creatinine level (OR=23.122; 95% CI: 3.123-171.217; p=0.002) were found to be independent risk factors associated with nephrotoxicity (Table 2).
Nephrotoxicity was observed in 88 of the patients aged ≥ 65 years. When the patients in the geriatric age group were compared based on nephrotoxicity, the initial serum urea and creatinine values, immunosuppression, concomitant nephrotoxic agent use, and overall mortality rates were found to be statistically higher in patients with nephrotoxicity (p<0.05) (Table 3). In the same patient group, initial serum creatinine level (OR=22.489; 95% CI: 2.835-178.426; p=0.003) and concomitant nephrotoxic agent use (OR=2.516; 95% CI: 1.275-4.963; p=0.008) were identified as independent risk factors associated with nephrotoxicity (Table 4).
Comparison between younger and older patients who developed nephrotoxicity showed that the older group had significantly higher APACHE II score, vasopressor agent use, and 14-day, 28-day, and overall mortality rates (p<0.05) (Table 5). There was no significance between the two groups in terms of initial and end-treatment serum urea and creatinine levels, concomitant nephrotoxic agent use, and hemodialysis need.
31.8% (n=54) of the cases were in young (age 18-64 years) and 68.2% (n=116) were in geriatric group (age ≥ 65 years). When the geriatric and younger patients were compared in terms of comorbid diseases, the incidence of COPD and cardiac diseases were significantly higher in the geriatric group (p<0.05). When nephrotoxicity rates were compared between the younger and geriatric groups, the rate was significantly higher in the geriatric group (p<0.001). Also, initial serum urea and creatinine, end-treatment urea and creatinine concentrations, APACHE II score, the rate of vasopressor agent use, 14-day, 28-day, and overall mortality rates were found significantly higher in the geriatric group (p<0.05) (Table 6).