Haemodialysis Complications and Access
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Direct answer
Haemodialysis complications arise from two sources: the vascular access itself and the rapid fluid and solute shifts during each session. The most common acute problem is intradialytic hypotension, usually from ultrafiltration that outruns plasma refilling, while the most dangerous access complication is bloodstream infection from a tunnelled catheter. An arteriovenous fistula is the preferred long-term access, but it needs several weeks to mature before first use.
What you must remember
- Preferred access: arteriovenous fistula first, then arteriovenous graft; a tunnelled catheter is only a temporary bridge.
- Fistula care: no blood pressure cuffs, venepuncture or cannulation on the access arm; check the thrill and bruit daily.
- Intradialytic hypotension: the commonest acute complication, driven by excessive ultrafiltration, cardiac dysfunction and autonomic neuropathy.
- Dialysis disequilibrium syndrome: headache, nausea, restlessness, seizures or coma after a rapid fall in urea, mostly in early sessions.
- Steal syndrome: a cold, pale, painful hand from a high-flow fistula; it needs urgent vascular review.
- Catheter infection: a leading cause of bacteraemia in dialysis units, with Staphylococcus aureus a key organism.
- Dialysis-related amyloidosis: beta-2 microglobulin deposition causing carpal tunnel syndrome and shoulder arthropathy after years of treatment.
An intradialytic crash, step by step
A 58-year-old man, two hours into his third weekly session, develops sweating, cramps and light-headedness. His blood pressure has fallen from 140/84 to 86/50 mmHg, but the fistula thrill is still present.
- Stop ultrafiltration: The first step is to stop ultrafiltration at once, because removing more fluid from a failing circulation turns a mild episode into a serious one.
- Lay him flat: He is then laid flat and given a small saline bolus.
- Review the session: Once he is stable, the session is reviewed: the target weight may have been set too aggressively, his morning antihypertensive should have been held, and the dialysate may be too warm.
- Prevent recurrence: Cooling the dialysate by a degree or so, or using sodium profiling, often prevents recurrence, and midodrine is considered if episodes persist.
- Watch the access: A stenosing fistula shows rising venous pressure during dialysis, falling blood flow and prolonged bleeding after needle removal, and it should be referred for angioplasty before it thromboses.
Where the exam tries to catch you
Four traps recur in examiner questions.
- Trap: confusing intradialytic hypotension with dialysis disequilibrium Correct: hypotension occurs during or soon after ultrafiltration and is managed by adjusting fluid removal.
- Trap: answering headache and vomiting after the first session with hypotension Correct: disequilibrium appears after the first session or early in a new patient's dialysis, when urea falls faster than it does in the brain. Mannitol or hypertonic saline treats established disequilibrium, and prevention depends on slower initial clearance.
- Trap: mistaking steal syndrome for a clot Correct: a clot or deep vein thrombosis can look similar, but a cold, pale, painful hand with a loud bruit points to flow diversion.
- Trap: leaving the fistula arm unprotected Correct: the fistula arm must be labelled and protected on every ward.
Frequently asked questions
Which vascular access is preferred for long-term haemodialysis?
An arteriovenous fistula is preferred because it carries the lowest long-term infection and thrombosis risk, and it is usually made in the non-dominant arm. An arteriovenous graft is the usual second choice when veins are unsuitable. A tunnelled catheter serves only as a temporary bridge.
What causes dialysis disequilibrium syndrome?
Dialysis disequilibrium syndrome results from a rapid fall in plasma urea during haemodialysis, leaving the brain relatively hyperosmolar so that water shifts into it. It causes headache, nausea, restlessness, seizures and, in severe cases, coma, most often in the first session. Slower initial clearance is the key preventive step.
How is intradialytic hypotension treated during a session?
Intradialytic hypotension is treated by stopping or reducing ultrafiltration, lying the patient flat and giving a small saline bolus if needed. Recurrence is reduced by realistic dry weight targets, holding antihypertensives before dialysis and cooling the dialysate. Midodrine is considered when episodes persist.
What is steal syndrome after an arteriovenous fistula?
Steal syndrome is distal limb ischaemia caused by a high-flow fistula diverting blood away from the hand. It presents with a cold, pale, painful hand and sometimes numbness, and it needs urgent vascular assessment. Surgical reduction of fistula flow is the usual definitive treatment.
Why should blood pressure not be measured on the fistula arm?
Cuffs on the fistula arm can compress a maturing or functioning fistula and lead to thrombosis or stenosis. Venepuncture and cannulation are avoided on that arm for the same reason. The opposite arm is used for blood pressure readings and blood sampling.