Socio-demographic Characteristics
After reviewing 628 ICU patient records, 582(92.68%) records were included in the final analysis, as 38 records were excluded due to incompleteness and 8 records due to lost. The mean age of the participants’ at the time of follow-up was 43±16 years. Above one-fourth of participant age was under 40-50 age category. In this study, more than half of (52.23%) participants were male. Regarding to residency more than half of (55.15%) participants were from rural (Table 1).
Base line Clinical and Laboratory related Characteristics
Out of the total 582 patients, more than one fifth of participants were admitted to the ICU with the main diagnosis of cardiovascular disease (20.45%), and about 111 (19.07%) participants were admitted with the diagnosis of acute respiratory distress syndrome (ARDS). During the study follow-up period, more than three-fourths of patients were admitted to the ICU with a platelet level greater than 150,000/mm3 (84.36%). About sixty-nine (11.86%) ICU patients admitted to the ICU had sepsis at follow-up time. Regarding serum creatinine level, the majority of study participants (93.47%) had a serum creatinine level of 1.2 mg/dl during a follow-up period. On the other hand, participants were admitted with the diseases such as diabetes mellitus (12.89%), congestive heart failure (5.67%), chronic liver disease (1.37%), stroke (2.58%), and hypertension (18.07%).
During the study follow-up period, the majority of 566 (97.25%) of the study participants had urine output greater than 400 ml/day. In the study, participants on the Glasgow coma scale 135 (23.20%), 220 (23.20%), and 227 (39.00%) were classified as severe, moderate, and mild, respectively (Table 2).
Intervention related characteristics
Among the total 582 ICU patients, more than half of patients were on mechanical ventilators 339(58.25%), and more than one fourth of the participants 159(27.37 %) used non-steroidal anti-inflammatory drugs (NSAIDs). About seventy-seven (13.25%) participants were on vasopressors, whereas, 90(15.49%) were ever on diuretics (Table 3).
Incidence of AKI among ICU patients
The incidence rate of AKI in the cohort during the 3965 person days of observation (PDO) was 19.67 per 1000 (95% CI: 15.76–24.56) person-days of follow-up, with a median survival time of 17 days (IQR = 11–35). In this study, the cumulative incidence rate of AKI among patients admitted to the ICU during the follow-up period was 13.4% (95% CI: 10.86, 16.43), as the minimum and, maximum follow-up times of 3 and 48 days, respectively. Among 78 (13.4%) AKI patients, 61 (78.21%) were stage I AKI, 10 (12.82%) stage II, and 7 (8.97%) stage III AKI patients. Five hundred four (86.6%) patients were censored until the end of the study period.
Overall Kaplan- Meier survival function
The overall Kaplan-Meier estimate showed that the probability of survival of patients was relatively high in the first weeks of admission, which comparatively decreased as follow-up time increased. As a result, the overall survival probability after admission to the ICU was 24.30% (95% CI: 6.63, 47.83) at 3965 days of follow-up. The estimated survival probability was 99.14% (95% CI: 97.95, 99.64) in the first three days of follow-up time, 97.94% (96.30, 98.85) in the fourth days of follow-up time, 95.50% (95% CI: 93.15, 97.06) in the fifth days of follow-up time, 77.11% (95% CI: 70.77, 82.26) in the next 10 days, and 57.31% (95% CI: 45.25, 67.65) in the next 15 days, and so on. The overall median survival time of patients admitted to the ICU in the study was 17 days (IQR: 11-35). At the end of 48 days of hospital stay, the overall survival probability of patients was 24.30% (95% CI: 6.63, 47.83) with a standard error of 0.11. As shown in the figure below, the Kaplan-Meier survival curve decreases stepwise during the ICU stay, and there is no occurrence of AKI after 35 days of follow-up (Fig.1).
Kaplan Meier-Curve and log-rank test
Based on Kaplan Meier curve with long-rank test the Kaplan-Maier survival function for congestive heart failure had a median survival time of 10 days and 17 days without congestive heart failure (CHF). As a result, the incidence rate for CHF patients was 48 per 1000 person days of observation and 17 per 1000 person days of observation for counterparts. The difference of the group was significant at P-value of <0.001(Fig.2).
Likewise, patients diagnosed with sepsis had a lower median survival time (9 days) compared to those who had not been diagnosed with sepsis, who had a median survival time of 35 days. According to our study, the incidence rate for patients diagnosed with sepsis was 63 per 1000 days of observation, and the incidence rate for patients without a sepsis diagnosis was 14 per 1000 days of observation. This survival time difference was statistically significant with a p-value of <0.001 (Fig.3).
Similarly, Patients following treatment with vasopressors had a low survival probability, with a median survival time of 9 days, and the comparative group had a median survival time of 21 days. In addition, the incidence rate for patients with treatment with vasopressors was 64 per 1000 days of observation and 13.1 per 1000 days of observation for patients without treatment with vasopressors. The difference was statistically significant at a p-value of<0.001 (Fig.4).
Study subjects who were followed with diabetes mellitus had a low survival probability with a median survival time of 11 days compared to patients who had no diabetes mellitus and a median survival times of 21 days. Also, the incidence rate for diabetic patients was 49 per 1000 days of observation and 15 per 1000 days of observation for the counterparts. The difference was statistically significant at a p-value of<0.001 (Fig.5).
The median survival time of patients who had thrombocytopenia (PLT <150,000/mm3) had a low survival probability, with a median survival time of 11 days, compared to those patients with PLT greater than 150,000/mm3. The incidence rate was 43 per 1000 days of observation and 16 per 1000 days of observation for the counterpart. The difference was significant at a p-value of<0.00 (Fig.6).
According to our study, patients diagnosed with Anemia had a median survival time of 12 days, and without anemia, the median survival time was 18 days. Our study reveals that the incidence rate for anemic patients was 54.2 per 1000 days of observation and 17 per 1000 days of observation for counterparts. The difference was statistically significant at a p-value of<0.001 (Fig.7).
Predictors of AKI among ICU patients
Initially, all variables had been entered into the bivariate Cox proportional hazard regression model. Based on this model, the Glasgow coma scale, hypertension, hypotension, congestive heart failure, pulse rate, residence, urine output, serum creatinine, low level of platelets (thrombocytopenia), length of stay, sepsis, diabetes mellitus, anemia, major abdominal surgery, Non-steroidal anti-inflammatory drugs, vasopressors, and gentamicin were candidates for multivariable analysis with a p-value of<0.2. However, in multivariable Cox regression analysis, sepsis, congestive heart failure, diabetes mellitus, thrombocytopenia, anemia, and vasopressors were statistically significant predictors of acute kidney injury among critically ill patients with p-values< 0.05.
According to this study, the hazards of participants with sepsis were 2.02 times more likely to develop AKI as compared to those who had no sepsis (AHR=2.02; 95% CI: 1.06, 3.85). Furthermore, the hazard of developing AKI among the participants who had diabetes mellitus was 2.46 times higher than their comparatives (AHR=2.46; 95% CI: 1.44, 4.22). The hazard of AKI among the participants who had Anemia was 3.28 times higher than that among those with no anemia (AHR=3.28; 95% CI: 1.77, 6.09). The hazard of developing AKI among the participants who had congestive heart failure was 3.11 times higher than among those who had no congestive heart failure (AHR=3.11; 95% CI: 1.57, 6.16). The hazard of developing AKI was 2.18 times higher among the participants who had thrombocytopenia as compared to those who had no thrombocytopenia (AHR=2.18; 95% CI: 1.20, 3.96). Lastly, those participants who were treated with vasopressors during the follow-up period were found to be at 2.57 times higher hazard of developing AKI compared to those who were not treated with vasopressors (AHR=2.57; 95% CI: 1.35, 4.90)(Table 4).
Model Fitness Test
The data in the Cox proportional hazard regression model's overall model fitness is shown in the image below. Residuals have a standard censored exponential distribution with hazard ratio. The hazard function follows 45˚, which is near the baseline hazard when we compare the line with the reference (cox Snell residual), showing that the model was well fitted. As a result, the Cox-Snell residuals test reveals that the model was well fitted. It was feasible to draw the conclusion that the final model fit the data well based on the residual test (Fig.8).