Guide — Renal
Hemodialysis Fundamentals
Hemodialysis is the most common form of renal replacement therapy, using an artificial kidney (dialyzer) to filter blood when the kidneys can no longer maintain fluid and solute balance.
11 min read · Renal
Educational use only. This content is intended for nursing students and exam preparation. Clinical decisions require licensed professional judgment and institutional protocols. This material supports nursing education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional policy, or medical direction. Always follow facility protocols and current provider orders.
Purpose of Dialysis
Dialysis replaces the filtration and regulatory functions of failed kidneys. It performs four key functions:
Waste removal
Removes uremic toxins — urea, creatinine, uric acid, and other nitrogen-containing compounds that accumulate in kidney failure
Fluid removal
Removes excess fluid (ultrafiltration) — essential when kidneys can no longer maintain fluid balance or when fluid overload is life-threatening
Electrolyte balance
Corrects hyperkalemia, hyperphosphatemia, and other electrolyte imbalances that cannot be managed medically
Acid-base correction
Removes excess acid (H⁺) and provides bicarbonate — corrects the metabolic acidosis of renal failure
Dialysis is life-sustaining, not curative. It replaces approximately 10–15% of normal kidney function. Transplant is the only true "cure" for ESRD.
Hemodialysis Process
Vascular access established
Blood is withdrawn from the patient through the arterial needle/port of the access device. Flow rate: typically 300–400 mL/min.
Blood passes through the extracorporeal circuit
Anticoagulation (heparin IV or regional citrate) prevents clotting in the circuit. Blood circulates outside the body through tubing to the dialyzer.
Dialysis membrane filtration (dialyzer = artificial kidney)
Diffusion: waste products (urea, creatinine, potassium) move from blood into dialysate across semipermeable membrane (concentration gradient). Ultrafiltration: hydrostatic pressure removes excess fluid from blood.
Dialysate flows counter-current
Dialysate flows in the opposite direction of blood flow to maximize concentration gradient efficiency. Dialysate composition adjusted to patient's needs (potassium bath, bicarbonate concentration).
Cleaned blood returned to patient
Processed blood is returned through the venous needle/port. Temperature maintained with blood warmer. Session typically lasts 3–5 hours, 3 times per week for ESRD.
Vascular Access Types
| Access Type | Description | Pros / Cons |
|---|---|---|
| AV Fistula (preferred) | Surgical anastomosis of artery to vein — typically radial artery to cephalic vein in non-dominant forearm. Requires 6–12 weeks to mature. | BEST: longest lasting, lowest infection rate, lowest clotting risk. Requires planning — create before dialysis needed. |
| AV Graft | Synthetic graft (PTFE) connects artery to vein when vessels are inadequate for fistula. Ready in 2–4 weeks. | Higher infection and clotting rate than fistula. Lasts 2–3 years on average. |
| Tunneled Central Venous Catheter (CVC) | Double-lumen catheter tunneled under skin to internal jugular or femoral vein (e.g., Permcath, Quinton). Used when no AV access available. | Immediate use possible. Highest infection rate, highest clotting risk, poorest blood flow rates. Last resort for permanent access. |
| Temporary CVC (non-tunneled) | Non-tunneled IJ, subclavian, or femoral catheter for emergent dialysis. Not tunneled under skin. | Emergent use only. Very high infection and thrombosis risk. Should not remain in >2 weeks if possible. |
Complications
| Complication | Signs / Symptoms | Nursing Action |
|---|---|---|
| Hypotension (most common intradialytic complication) | BP drop ≥20 mmHg systolic, lightheadedness, nausea, cramping | Trendelenburg position, reduce ultrafiltration rate, NS bolus per order, notify provider |
| Muscle cramps | Painful cramping — often legs — due to rapid fluid/electrolyte shifts | Reduce ultrafiltration rate, NS or hypertonic saline bolus, dialysate sodium adjustment |
| Air embolism (rare, life-threatening) | Sudden dyspnea, chest pain, cyanosis, altered consciousness — air enters circuit | STOP dialysis immediately; clamp blood lines; turn patient left lateral Trendelenburg; O₂; emergency response |
| Dialysis disequilibrium syndrome | Headache, nausea, AMS, seizures — occurs in first treatments when urea removed too quickly from blood but brain equilibration lags | Slow dialysis rate; shorter first sessions; monitor neurologic status closely |
| Access infection | Redness, warmth, swelling, purulent drainage at access site; fever | Culture; antibiotics; may require catheter removal for tunnel infection |
| Clotting of access | Loss of bruit/thrill on fistula/graft; poor blood flow during dialysis | Thrombectomy or declot procedure; report immediately |
| Bleeding | Prolonged bleeding post-needlestick, anticoagulant effect | Apply pressure; protamine sulfate reverses heparin if needed; assess for internal bleeding post-treatment |
Pre-Dialysis Assessment
Post-Dialysis Assessment
NCLEX Pearls
- ✦AV fistula arm: NEVER take BP, draw blood, or start IV in that arm. Assess bruit AND thrill every visit.
- ✦Order of preferred access: AV Fistula → AV Graft → Tunneled CVC → Temporary CVC (best to worst).
- ✦Most common intradialytic complication = hypotension. Intervention: Trendelenburg, slow UF rate, NS bolus.
- ✦Hold antihypertensives before dialysis (hypotension risk). Hold water-soluble vitamins (dialyzed off).
- ✦Air embolism = stop treatment immediately, left lateral Trendelenburg, 100% O₂, emergency response.
- ✦Loss of bruit and thrill = fistula thrombosis — immediate nursing action = notify provider.
- ✦Dialysis disequilibrium: first-time dialysis patients — urea removed faster from blood than brain → cerebral edema symptoms. Prevention: shorter, slower first sessions.
- ✦Hepatitis B vaccination before starting dialysis — better immune response at higher eGFR.
- ✦Dry weight = the weight after dialysis with no extra fluid — the patient's fluid-free target weight.
Related Resources
Standards & sources
Fact-checked Jun 21, 2026This page is written to align with KDIGO Clinical Practice Guidelines · National Kidney Foundation (NKF). It is an educational summary, not a citation of any single document — always verify specific doses, values, and protocols against current guidelines and your facility policy. How we source content →