Makindo Medical Notes

💧 Renal Replacement Therapy (RRT) refers to life-sustaining interventions that replace kidney function when intrinsic renal activity is inadequate. It includes dialysis (haemodialysis, peritoneal dialysis) and renal transplantation. Indications span acute kidney injury (AKI) with refractory complications to long-term end-stage kidney disease (ESKD).

ℹ️ About

• RRT removes metabolic waste products (urea, creatinine, toxins). 🧪
• Maintains fluid, electrolyte, and acid–base balance. ⚖️
• Options include intermittent haemodialysis, continuous RRT (CRRT), peritoneal dialysis, and transplantation.
• Choice depends on acuity, haemodynamic stability, patient comorbidities, and resource availability.

🧑‍⚕️ Patient Selection for RRT

RRT is not “one size fits all” — selection depends on indication, patient factors, prognosis, and goals of care. The key challenge is deciding between dialysis initiation, transplantation, or conservative management.

✅ Candidates for RRT

• 💥 Acute Kidney Injury (AKI): • Severe metabolic acidosis (pH < 7.1) • Hyperkalaemia > 6.5 mmol/L with ECG changes refractory to therapy • Pulmonary oedema unresponsive to diuretics • Uraemic encephalopathy, pericarditis, seizures • Ingested dialysable toxins (e.g. lithium, ethylene glycol)
• 🧪 Chronic Kidney Disease (CKD stage 5 / ESKD): • eGFR < 10 mL/min/1.73m² (or < 15 with symptoms) • Intractable pruritus, cachexia, weight loss • Resistant fluid overload or hypertension • Persistent uraemic complications (nausea, neuropathy, bleeding tendency)
• 🫁 Critical care patients: • CRRT indicated if haemodynamically unstable or with multi-organ failure. • Dialysis can be started early (pre-emptive) or delayed (symptom-driven) depending on centre protocol and KDIGO guidance.
• 🧬 Renal Transplant candidates: • Patients with ESRD who are < 70 years, relatively fit, and have no absolute contraindication to surgery. • Offers best survival and quality of life compared to dialysis.

⚠️ Relative Contraindications

• 📉 Severe frailty, advanced dementia, or very limited life expectancy → dialysis often offers no meaningful survival benefit.
• 💔 Severe comorbidities (advanced heart failure, metastatic cancer) where RRT burdens outweigh benefit.
• 🦠 Uncontrolled sepsis, haemodynamic collapse — CRRT may still be used as supportive, but prognosis is poor.

🌿 Conservative (Non-Dialytic) Management

• Selected in frail elderly or patients with multiple comorbidities.
• Focus on symptom control, fluid balance, diet, and palliative care input.
• Studies show similar survival to dialysis in >80s with severe frailty, but with better quality of life and fewer hospital admissions.

🤝 Shared Decision-Making

• 🔑 Discuss prognosis, goals of care, and patient/family preferences.
• Multidisciplinary approach: nephrology, cardiology, geriatrics, palliative care.
• Education on dialysis modalities (HD vs PD vs conservative) empowers patient choice.

💡 Exam Pearl: • Start RRT: refractory AEIOU indications. • Delay/avoid RRT: in advanced frailty, poor prognosis, or patient refusal. • Transplantation: best option for eligible patients → survival benefit over dialysis.

⚠️ Indications for Acute RRT (AEIOU mnemonic)

• 🍏 Acidosis: Severe, refractory metabolic acidosis (pH < 7.1).
• ⚡ Electrolyte imbalance: Life-threatening hyperkalaemia (>6.5 mmol/L or ECG changes) despite medical therapy.
• 💧 Intoxications: Dialysable toxins (lithium, ethylene glycol, salicylates, methanol).
• 🌊 Overload: Refractory fluid overload causing pulmonary oedema/respiratory failure.
• ⏱️ Uraemia: Complications such as pericarditis, encephalopathy, severe nausea/bleeding.

🔎 Modalities of RRT

• 🩸 Haemodialysis (HD): Blood is pumped through a dialyser against a dialysate solution. • Intermittent HD (IHD) 3×/week common in ESKD. • Efficient solute clearance, but rapid fluid shifts may cause hypotension.
• 💤 Continuous Renal Replacement Therapy (CRRT): Used in ICU for unstable patients. • Includes CVVH (haemofiltration), CVVHD (haemodialysis), CVVHDF (haemodiafiltration). • Gentle solute and fluid removal, avoids haemodynamic instability. • Requires anticoagulation (heparin or citrate). ⚠️
• 🩺 Sustained Low-Efficiency Dialysis (SLED): Hybrid between IHD and CRRT. Runs over 6–12h.
• 🫁 Peritoneal Dialysis (PD): Uses peritoneum as a semipermeable membrane. • Continuous Ambulatory PD (CAPD): manual exchanges during the day. • Automated PD (APD): cycler-assisted overnight. • Less haemodynamic stress, can be performed at home. Risk = peritonitis. 🦠
• 🧬 Renal Transplantation: Gold standard for ESKD if eligible. • Restores full renal function & quality of life. • Requires lifelong immunosuppression & carries risks (infection, malignancy, rejection).

📊 Comparison of RRT Modalities

Modality	Mechanism	Setting	Advantages	Limitations
🩸 Haemodialysis (HD)	Diffusion across semipermeable membrane	Hospital / dialysis unit	Efficient solute & fluid clearance	Rapid shifts → hypotension, requires vascular access
💤 CRRT	Slow continuous filtration & dialysis	ICU (unstable patients)	Gentle fluid removal, better tolerated in shock	Needs ICU nursing, anticoagulation, slower clearance
🫁 Peritoneal Dialysis (PD)	Peritoneum = dialysis membrane	Home / long-term	No vascular access, more independence, haemodynamic stability	Risk of peritonitis, less efficient clearance, not ideal in abdominal pathology
🧬 Renal Transplant	Surgical implantation of donor kidney	Tertiary centre	Best survival & QoL, restores full renal function	Requires immunosuppression, risk of rejection/infection, donor shortage

🧬 Renal Transplant: Contraindications

• 🚫 Active or recent malignancy (except some skin cancers).
• 🚫 Untreated chronic infection (TB, HIV uncontrolled, hepatitis with viraemia).
• 🚫 Severe cardiovascular disease (unfit for major surgery).
• 🚫 Ongoing sepsis or immunodeficiency.
• 🚫 Severe dementia, frailty, or inability to comply with lifelong immunosuppression.
• ⚠️ Relative: obesity (BMI > 40), severe liver disease, psychiatric illness without support.

⚙️ Vascular Access

• 🔪 Temporary catheter: Internal jugular, subclavian, or femoral vein (for AKI/urgent dialysis).
• 🔄 Tunneled catheter: Semi-permanent access for chronic HD.
• 💪 Arteriovenous fistula (AVF): Gold standard for long-term HD (low infection, durable). Takes weeks to mature.
• 🧵 Arteriovenous graft: Synthetic graft when veins unsuitable.

💡 OSCE Pearl: • AVF = best long-term access (low infection, lasts years). • Catheter = fastest access but high infection risk. • Always check thrill & bruit when examining an AV fistula.

📊 Complications of RRT

• 🩸 Hypotension, arrhythmias, cramps (especially IHD).
• ⚖️ Disequilibrium syndrome (neurological symptoms due to rapid osmotic shifts).
• 🦠 Infection (catheter sepsis, PD-associated peritonitis).
• 💎 Electrolyte shifts: hypophosphataemia, hypocalcaemia, alkalosis.
• 🫀 Long-term: AVF thrombosis, amyloidosis, accelerated atherosclerosis.

👩‍⚕️ Special Considerations

• 🧪 Drug dosing: Many antibiotics/antivirals require renal dose adjustment or redosing post-dialysis.
• 🫁 Critical care: CRRT preferred in septic shock or ARDS patients requiring tight fluid balance.
• 👵 Frailty/elderly: Conservative management may be more appropriate than RRT in advanced frailty.
• 📉 Prognosis: Mortality remains high in critically ill AKI patients needing RRT (~40–60%).

🧑‍⚕️ Case Examples — Renal Replacement Therapy (RRT)

• Case 1 (Haemodialysis for end-stage CKD): 💉 A 72-year-old man with diabetic nephropathy and eGFR 7 mL/min develops refractory hyperkalaemia and severe uraemic symptoms (pruritus, confusion). Haemodialysis is initiated via a tunneled central line. Teaching point: haemodialysis rapidly clears toxins and electrolytes, but requires vascular access and frequent sessions.
• Case 2 (Peritoneal dialysis at home): 🏠 A 68-year-old woman with CKD 5 opts for peritoneal dialysis to maintain independence. She performs continuous ambulatory peritoneal dialysis (CAPD) at home with carer support. She later develops peritonitis (cloudy effluent, abdominal pain), treated with intraperitoneal antibiotics. Teaching point: peritoneal dialysis offers lifestyle flexibility but carries infection risk.
• Case 3 (Acute kidney injury & CRRT in ICU): 🏥 A 75-year-old man with septic shock develops AKI with refractory acidosis and fluid overload despite diuretics. Continuous renal replacement therapy (CRRT) is started in ICU to gently remove solute and fluid. Teaching point: CRRT is preferred in haemodynamically unstable patients, as it avoids rapid fluid shifts of conventional dialysis.
• Case 4 (Conservative management): 🤝 An 84-year-old frail woman with advanced heart failure and stage 5 CKD declines dialysis after discussion of risks, burden, and limited survival benefit. She is managed conservatively with symptom control, anaemia treatment, and palliative support. Teaching point: in selected elderly patients, conservative management is a valid option, prioritising quality of life over invasive RRT.