Acute renal failure (ARF) corresponds to a sudden reduction in the kidneys’ ability to purify uremic toxins and regulate the body’s electrolyte balance. It is manifested by a rise in plasma urea and creatinine concentrations and/or a reduction in urine volume [1] . The incidence of ARF in the ICU reported in the literature varies according to the definitions chosen [2] . More than 50% of patients hospitalized in intensive care develop AKI, and more than 10% of them require extrarenal renal replacement therapy (ERT) during their hospitalization [1] [2] . KDIGO’s three-stage definition correlates the intensity of AKI with ICU mortality [3] [4] . This classification necessitates close monitoring of plasma creatinine and diuresis, and therefore better diagnosis. In the ICU, ARF is most often multifactorial, secondary to hypovolemia and sepsis inducing renal hypoperfusion and acute tubular necrosis [5] [6] . Prevention is essentially based on identifying patients at risk, avoiding nephrotoxic factors and maintaining renal perfusion by controlling patients’ blood volume and renal perfusion pressure [7] . In Chad, a developing country where the health system is under construction, with only 5 nephrologists for around 18 million inhabitants, epidemiological data on ARF in the ICU are non-existent. The aim of our study was to determine the prevalence of ARF in polyvalent intensive care units.

This was a cross-sectional, descriptive and analytical study conducted over a period of eight (08) months (July 1 to December 31, 2021) in the intensive care unit of the Centre Hospitalier Universitaire la référence nationale (CHU RN) in N’Djamena (Chad). Patients were recruited consecutively. Patients aged 18 and over with ARF on admission or during hospitalization in the intensive care unit were included. Data were collected from patient records using a pre-established questionnaire including clinical, para-clinical, therapeutic and evolutionary variables.

ARF was defined according to the KDIGO 2021 criteria ( Table 1 ).

Anuria is defined by diuresis < 100 ml in 12 hours, oliguria by diuresis < 0.3 ml/kg/h, diuresis is preserved when it is ≥0.5 ml/kg/h [8] . Multi-visceral failure syndrome was defined by the TRAN score ( Table 2 ).

Data were collected and analyzed using Excel 2010 and SPSS version 18.0 (Statistique Package for Social Sciences 18.0). Results were given in terms of frequency and percentage for qualitative variables, and by calculating means with their standard deviation for quantitative variables. Analytical studies were carried out using cross-tabulations. Means with standard deviations and percentages were compared using the Student’s t-test and the Chi-square test, according to their conditions of applicability, with a significance threshold if “p” < 0.05.

Ethical Considerations: we obtained research authorization from the administration of the Centre Hospitalier et Universitaire; the informed consent of the patients or their parents; and the data were kept strictly confidential.

During the study period, we identified 206 patients admitted to the general intensive care unit at RN University Hospital, 52 of whom had presented with ARF, giving a prevalence of 25.2%. The mean age was 47 ± 17.1 years [19 - 86 years]. The 19 - 39 age group followed by the 40 - 59 age group accounted for 38.5% and 36.5% respectively, with a sex ratio of 1.5. The departments from which patients came were the reception and emergency department (67.3%), nephrology (19.2%), internal medicine (15.4%) and surgery (3.8%). Terrain was dominated by hypertension (28.8%), diabetes (23.1%) and chronic renal failure (11.5%). The main reason for admission to intensive care was altered consciousness (42.3%), followed by sepsis (26.9%) and hemodynamic instability (17.3%). Community-acquired ARF accounted for 92.3% and hospital-acquired ARF for 7.7%. Functional signs were dominated by oligoanuria at 84.6% and impaired consciousness at 78.8%, with a mean Glasgow score of 9.2 ± 2.7 [5] - [15] ( Table 3 ).

Mean creatinemia was 125.2 mg/L [28.6 - 588.3 mg/L], mean blood urea 2.3 g/L [0.7 - 6.0 g/L]. KDIGO stage 3 ARF accounted for 53.9% of cases ( Figure 1 ). The blood count revealed anemia in 65.4% of patients, with a mean hemoglobin of 9.6 g/dl [3.4 - 16.6 g/dl]. Mean CRP was 99.4 mg/l [0.55 - 530 mg/l]. Ultrasound was normal in 23.1% (n = 12), and showed dilatation of the excretory tract on a single kidney in one patient (1.9%), and stigmata of chronicity in three patients (5.8%).

ARF was functional in 28.4% of patients, obstructive in 3.8% and organic in 67.8%. ARF related to a septic mechanism was found in 44.2% of cases ( Figure 2 ), with a statistically significant correlation (p = 0.030) between the causes and the KDIGO stage of ARF. Sixty-nine percent (69.2%) of patients had at least one multivisceral failure associated with ARF. Hematological failure predominated (42.3%), followed by cardiac (19.2%) and respiratory (19.2%) failure. Management of ARF patients was based on rehydration (82.7%), antibiotic therapy (53.8%), transfusion (42.3%), and obstruction removal in two patients (3.8%). Five patients (9.6%) required extrarenal purification.

Progression was marked by complete recovery of renal function in 15.4% (n = 8) of patients. Four patients progressed to chronic renal failure. Forty patients (76.9%) died. Most deaths were related to multivisceral failure syndrome and the KDIGO stage of AKI, with statistical significance (p = 0.036). The average length of stay of patients in intensive care was 4.4 days [1 - 48 days/dl].

The incidence of ARF in the ICU varies according to the type of admission and diagnostic criteria. In our study, the frequency of ARF in the ICU was 25.2%. In Morocco, it was 13.4% [9] . In Europe, the incidence is 30% [8] . These results confirm the findings of the literature, according to which the incidence of ARF in intensive care varies between 3% and 30% [10] [11] . In our series, males accounted for 55.8%, with a mean age of 47 ± 17.1 years [19 - 86 years]. In Morocco, Kerzaz R et al. reported an average age of 44.69 years (±19.70 years) [12] . In the West, it occurs between 60 and 80 years of age, with maximum frequency in the population aged over 75 [13] .

The main reason for admission to intensive care was altered consciousness (42.3%), and the majority of patients (84.6%) presented with oligoanuria, with disturbed consciousness found in 78.8% of patients. Kerzaz R et al., in Morocco, reported oligoanuria and disturbed consciousness in 92% and 60% of their series respectively [12] . This may be attributable to uraemic encephalopathy, but may also be part of multivisceral failure, probably linked to a pre-existing chronic pathology [14] . In our series, risk factors accounted for 57.7% of cases, including hypertension (28.8%), diabetes (23.1%) and CKD (11.5%). In Mali, 61.60% of patients were exposed to one or more risk factors [15] , whereas in Burkina Faso, Coulibaly G et al. found 35.8% of cases [16] .

AKI was community-acquired in 92.3% of cases, and of organic origin in 67.8% of patients. The same finding has been reported by Brivet FG and Guerin C et al., where AKI is most often seen on admission [10] [17] . Several mechanisms could explain the occurrence of AKI in the hospital setting, such as volume depletion, arterial hypotension, sepsis, use of vasopressors, exposure to nephrotoxic “substances”, and also the additive interaction of multiple risk factors and associated conditions [18] . Sepsis is by far the most frequent mechanism of ARF in the intensive care setting, with incidence ranging from 32.7% to 75.9% depending on the series [12] [19] . In our study, sepsis accounted for 44.2% of organic causes. Studies have shown that sepsis and renal hypoperfusion preceded the onset of acute renal failure in 70% of cases, while 72% of intensive care patients in renal failure presented with sepsis [10] [19] . Their presence calls for vigilance in optimizing blood volume and limiting any additional nephrotoxicity [6] .

Therapeutically, vascular filling with crystalloids was the most commonly used treatment for hemodynamic failure (82.7%), and antibiotic therapy in 53.8% of cases. The incidence of ARF requiring extra-renal replacement therapy (ERT) in the ICU varies from one series to another. In our series, EER was indicated in 20 patients (38.46%), but only five (9.61%) patients had received EER, involving an average of two hemodialysis sessions lasting 2 hours per session. In the study by Cruz DN and Imane A, the incidence was 30% and 33.3% respectively [9] [20] . On the other hand, 4% and 6% depending on the series [3] [21] . This could be explained by the absence of consensus criteria for the indication of EER and the type of department recruitment. In our study, most patients requiring EER were unable to benefit from it for various reasons: the unavailability of dialysis machines in the ICU, the distance between the two departments posed logistical and packaging problems for patients with hemodynamic instability, and above all the absence of direct coordination between departments for absolute nephrological emergencies.

We recorded 40 deaths (76.9%), the causes of death being related to multivisceral failure syndrome and ARF (p = 0.036). This result is in line with mortality data for ARF reported in the intensive care setting, which varies between 56% and 79% [17] . The high proportion of mortality in our series could be explained essentially by the delay in admission of patients to the ICU, the severity of the initial clinical picture, notably multivisceral failure due to septic states, which are poor prognostic factors [22] . At the end of the stay, 15.4% (n = 8) patients had fully recovered their renal function. Four patients (7.7%) had progressed to chronic renal failure. The average length of stay for patients in intensive care in our cohort was 4.4 days [1 - 48 days].

Despite technological advances and a better therapeutic approach, our study highlights the high mortality of AKI due to the multiplicity of causes and imposes urgent measures to reduce its prevalence.