A 70-year-old woman is brought to A&E by her husband because she is acutely confused and drowsy. She has a history of chronic kidney disease stage 4 and is on multiple medications including Ramipril and Ibuprofen. Over the last 3 days she has had vomiting and poor oral intake. Her blood pressure is 90/60 mmHg and she has reduced skin turgor. Blood tests show urea 27 mmol/L, creatinine 340 µmol/L (baseline 200 µmol/L) and potassium 5.8 mmol/L. What is the most likely classification of her acute kidney injury?