Kidney replacement therapy and dialysis in children: Viva

Branch 1: Recognising the need for kidney replacement therapy

The candidate should recognise that this post-cardiac surgery girl has severe acute kidney injury with several of the AEIOU indications for urgent dialysis. She has refractory hyperkalaemia with widening of the QRS complex, an emergency, and fluid overload with rising ventilator pressures that signals early pulmonary oedema. A strong candidate should state that the hyperkalaemia is life-threatening and needs immediate calcium gluconate to stabilise the myocardium while definitive removal by dialysis is arranged, because the medical therapies of insulin-dextrose, salbutamol, and bicarbonate only shift potassium and do not remove it. [1]

If the examiner asks how common this scenario is, the candidate should cite the AWARE study finding that acute kidney injury develops in roughly 27 percent of critically ill children within the first week and severe AKI in about 12 percent, with post-cardiac surgery being a classic trigger because cardiopulmonary bypass and low cardiac output injure the kidney. The candidate should explain that the decision to dialyse rests on whether the disturbances are refractory and progressive with end-organ effects, which this child clearly has. [1]

Branch 2: Choosing the modality and starting it

If asked what modality, the candidate should justify continuous renal replacement therapy. This girl is on noradrenaline and is fluid overloaded, so she is haemodynamically too unstable for intermittent haemodialysis, which would crash her circulation with rapid fluid and solute shifts. Continuous renal replacement therapy removes fluid and solute gently over hours to days at the bedside and is the standard for the unstable critically ill child. The candidate should mention the need for a central venous line favouring the right internal jugular vein and avoiding the subclavian to preserve veins for a future fistula. [1]

A strong candidate should describe the prescription: an effluent dose of 25 to 35 mL per kg per hour, with anticoagulation by heparin or regional citrate, the latter monitored by ionised calcium and the total to ionised calcium ratio because citrate accumulates in liver dysfunction. Fluid removal is set to bring her gently toward her dry weight over 24 to 48 hours guided by her haemodynamics and ventilator pressures. If the examiner presses on alternatives, the candidate should note that acute peritoneal dialysis is a valid option in stable infants and resource-limited settings but is less efficient in severe hypercatabolism. [2]

Branch 3: The infant scenario and peritonitis

If the examiner changes the scenario to a 6-month-old infant with end-stage kidney disease, the candidate should shift to chronic peritoneal dialysis as the modality of choice. The candidate should explain that peritoneal dialysis uses the peritoneal membrane, needs no vascular access or needles, tolerates low blood pressure, and fits a small body where fistula creation and blood-circuit management are difficult. The prescription uses dwell volumes of 600 to 1100 mL per square metre, beginning low, with an overnight cycler, glucose-based dialysate, and icodextrin for the long dwell, and the candidate should stress the central role of nutrition via gastrostomy for growth. [2]

If the examiner introduces cloudy peritoneal dialysis effluent with abdominal pain and fever, the candidate should diagnose peritoneal dialysis-related peritonitis, the leading cause of technique failure and catheter loss. The candidate should state the diagnostic criterion of an effluent white cell count above 100 per microlitre after a dwell, send the effluent for culture, and start empirical intraperitoneal antibiotics covering gram-positive and gram-negative organisms immediately, then narrow to the organism, guided by the 2024 paediatric International Society for Peritoneal Dialysis update. The candidate should close by emphasising that dialysis in children is a bridge to transplantation, which offers the best survival and quality of life and should be planned from the outset. [3]