Acute Kidney Injury — SAQ

Stem

A 72-year-old man is admitted with three days of vomiting and diarrhoea.^[1] He takes ibuprofen 400 mg three times daily for osteoarthritis, ramipril 10 mg daily, furosemide 40 mg daily and metformin 500 mg twice daily for type 2 diabetes. On examination he is drowsy (GCS 14), pulse 108, blood pressure 96/60, respiratory rate 24, oxygen saturation 94 per cent on air; JVP is not visible, mucosae are dry, capillary refill 4 seconds. Investigations: sodium 132, potassium 6.8 mmol/L, urea 28, creatinine 346 micromol/L (3.9 mg/dL) (baseline 95 micromol/L three months ago), venous bicarbonate 11, pH 7.18. Urine dipstick: blood +, protein +, leucocytes negative; urine microscopy shows muddy brown granular casts. ECG shows peaked T waves and a widened QRS. Chest X-ray is clear. Renal ultrasound shows two kidneys of 11 cm with no hydronephrosis.

Questions

a) What is the diagnosis and what KDIGO stage is this? Justify with the criteria. (2 marks)

Acute kidney injury (KDIGO Stage 3):^[1] creatinine 3.6 times baseline (over the 3.0 threshold for Stage 3), with hyperkalaemia and acidosis. The muddy brown granular casts indicate intrinsic AKI, specifically acute tubular necrosis — the result of prolonged pre-renal hypoperfusion (volume depletion from gastroenteritis) compounded by the "triple whammy" of NSAID (afferent vasoconstriction), ACE inhibitor (efferent vasodilation) and diuretic.

b) Outline your immediate resuscitation. (3 marks)

Treat this as a hyperkalaemia emergency with ECG changes:^[2]

• Calcium gluconate 10 per cent, 10 mL IV over 5 to 10 minutes — to stabilise the myocardial membrane (no effect on potassium).^[2]
• Insulin 10 units soluble IV with 50 mL of 50 per cent dextrose over 15 to 30 minutes — to shift potassium into cells; check glucose at 30 min and hourly.
• Salbutamol 10 to 20 mg nebulised — adjunctive intracellular shift.
• Stop the nephrotoxins — ibuprofen, ramipril, furosemide (until volume replete), metformin (lactic acidosis).
• Cautious volume resuscitation with balanced crystalloid 250 to 500 mL boluses reassessed against perfusion (he is volume-depleted but at risk of pulmonary oedema given the ramipril and ARF); oxygen to keep saturation 94 to 98 per cent.
• Plan renal replacement therapy if K fails to fall or for the AEIOU indication (acidosis, refractory hyperkalaemia).

c) Outline the definitive management plan. (3 marks)

• Treat the cause — rehydrate for the pre-renal component; the ATN will take days to weeks to recover.^[1]
• Optimise haemodynamics — target mean arterial pressure 65 mmHg or more.
• Manage complications — potassium (ladder above), metabolic acidosis (sodium bicarbonate as pH is under 7.15), fluid balance with strict input-output chart and daily weights.
• Drug review — dose-adjust all renally cleared drugs (he is on metformin, now withheld); refer to pharmacy.
• Refer nephrology and critical care for likely dialysis given Stage 3 AKI with hyperkalaemia, acidosis and ECG changes.
• Monitor — hourly urine output (catheterise), daily U&E and creatinine, repeat ECG.

d) State two important complications of this condition and one long-term consequence. (2 marks)^[1]

Complications (any two):^[1] cardiac arrhythmia/arrest from hyperkalaemia; uraemic pericarditis; uraemic encephalopathy (he is already drowsy); pulmonary oedema from fluid overload; severe metabolic acidosis; infection (the leading cause of death in AKI). Long-term consequence: increased risk of future chronic kidney disease, accelerated CKD progression and cardiovascular events — all AKI survivors should have kidney function monitored and followed up.^[1]

References4ShowHide

1. [1]Kellum JA, Lameire N Diagnosis, evaluation, and management of acute kidney injury: a KDIGO summary (Part 1). Crit Care, 2013.PMID 23394211
2. [2]Long B, Warix JR, Koyfman A. Controversies in Management of Hyperkalemia. J Emerg Med, 2018.PMID 29731287
3. [3]Gaudry S, Hajage D, Schortgen F, et al. Initiation Strategies for Renal-Replacement Therapy in the Intensive Care Unit. N Engl J Med, 2016.PMID 27181456
4. [4]Bagshaw SM, Wald R, Adhikari NKJ, et al. Timing of Initiation of Renal-Replacement Therapy in Acute Kidney Injury. N Engl J Med, 2020.PMID 32668114