Background: Invasive mechanical ventilation (IMV) is life-saving in critically ill patients but may reduce renal perfusion and contribute to acute kidney injury (AKI). Local data on how often AKI develops in ventilated patients are limited.

Methods: This prospective observational study enrolled adults aged 20–80 years on IMV in the intensive care units (ICUs) of a tertiary teaching hospital in Tamil Nadu, India, over 18 months. Patients with chronic kidney disease, pregnancy, systolic blood pressure <90 mmHg or inotropic support before ventilation were excluded. Serum creatinine, urea and electrolytes were measured at baseline and every 24 hours, and urine output was recorded hourly. Patients were followed for up to 7 days or until liberation from the ventilator. AKI was defined by the serum creatinine criteria of the Acute Kidney Injury Network (AKIN); the primary outcome was a rise in creatinine of more than 0.3 mg/dL from baseline within 48 hours, and secondary outcomes were reduced urine output and electrolyte disturbance.

Results: Of 86 patients screened, 78 were analysed (45 men, 57.7%; 33 women, 42.3%). AKI developed in 34 patients (43.6%), all of whom also had reduced urine output; 44 patients (56.4%) did not develop AKI. Head injury (46.2%), hypertension (38.5%), diabetes mellitus (35.9%) and respiratory disorders (33.3%) were the recorded risk factors. Mild hypokalaemia occurred in 19 patients (24.4%; 9 with AKI), mild hyperkalaemia in 2 (both with AKI), moderate hyperkalaemia in 1 (no AKI) and mild hypernatraemia in 2 (no AKI). Two patients with AKI required continuous renal replacement therapy. Overall, 57 patients (73.1%) were extubated, 19 (24.4%) died and 2 (2.6%) left against medical advice. 

Conclusions: Nearly 44% of patients on IMV developed AKI, recognised by a rising serum creatinine with falling urine output. Daily monitoring of creatinine, urine output and electrolytes should be routine in ventilated patients so that AKI is identified early.