First Dialysis Session Protocol
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Direct answer
A patient's first haemodialysis session is deliberately half-sized: commonly 2-3 hours at blood flow 150-200 mL/min with conservative ultrafiltration, because a brisk urea clearance in a heavily uraemic patient invites dialysis disequilibrium — headache, restlessness, nausea, occasionally seizures and coma from the osmotic brain shift. The session begins with verified consent, weight, vitals, hepatitis B status and a working access — usually a dialysis catheter, since a fistula will not have matured. Monitoring is intense (blood pressure every 15-30 minutes initially), the heparin is cautious, and the team documents the disequilibrium and hypotension drills before they are needed rather than after.
What you must remember
- First-session sizing: 2-3 hours, blood flow 150-200 mL/min rising over successive sessions, aiming for a modest urea reduction (commonly cited as keeping the first session's reduction under about 40-50 per cent in high-risk patients).
- Disequilibrium syndrome: occurs in severe uraemia (very high urea, acidosis), presented as headache, nausea, agitation, confusion, seizures; the mechanism is an osmotic gradient — cerebral cells lag in shedding urea, so water shifts into the brain.
- Prevention: short slow first sessions, avoid over-rapid ultrafiltration, consider mannitol or hypertonic strategies only per medical orders in very high-risk starts.
- Access at initiation: a non-tunneled (or tunneled) central venous catheter — internal jugular preferred over femoral for flow and infection; the catheter is the bridge while a fistula matures.
- Cautious heparin: uraemic platelet dysfunction plus possible residual bleeding risk (recent surgery, uraemic pericarditis) argues for the lower effective dose; citrate if bleeding risk is high.
- Bath choices for the first run: potassium 3 rather than 2 in digitalised or malnourished patients, bicarbonate moderate, temperature 36-36.5, dialysate flow standard 500 mL/min.
- Circuit priming: saline prime is routine; blood priming is reserved for small children or severe anaemia with haemodynamic fragility, per policy.
- Documentation and monitoring: pre weight and vitals, hourly minimum observation with 15-30 minute blood pressures early, access site checks, and patient counselling — the first session sets adherence for years.
The first hour, minute by minute
A 46-year-old woman arrives with a uraemia of 210 mg/dL blood urea, creatinine 12, potassium 6.1, acidotic and breathless, 6 litres over dry. Zero minute: identity, consent, weight on the same scale she will use forever, vitals, chest auscultation for effusion and pericardial rub, access inspected — right internal jugular catheter, drawn and locked. The machine, self-tested and chlorine-cleared, carries a smaller-start prescription: 2.5 hours, blood flow 180, no ambitious ultrafiltration — perhaps 1.5 litres today and the rest across a daily short-run series, because pulling six litres on a first session invites both collapse and disequilibrium.
Blood flows at minute one; the technologist's eyes stay on the access limb, the chambers and the patient's face. At twenty minutes she reports a headache — blood pressure is holding, so the response is reassurance, closer observation and a slower pump, not termination; a true disequilibrium trajectory (worsening headache with confusion, hypertension then obtundation) would mean stopping and treating per protocol. By the end she is mildly tired, potassium 5.0, no cramps, and the schedule handed over is a gentle ramp over the week to full four-hour sessions. What the log records — weights, flows, symptoms, drug doses — becomes the baseline against which every future session reads.
Where students slip
Two slips recur. The first is prescribing ambition: a textbook four-hour full-flow session on a urea of 200 treats the numbers and harms the brain — the correct instinct is slower, shorter, more frequent. The second is access assumption: examining the catheter's function before the patient is draped, because a positional flow limitation found at minute zero is an inconvenience, found at minute forty it is a hypotensive emergency of unreturned blood. A quieter third slip is forgetting that the first session is also the patient's first experience of the machine, the needles-to-come and the lifestyle change — counselling and a gentle stable run are part of the prescription, and examiners increasingly phrase scenario questions around exactly that.
Frequently asked questions
Why is the first dialysis session kept short and slow?
To limit the rate of urea removal and prevent dialysis disequilibrium syndrome — cerebral osmotic shift causing headache, seizures and coma in severely uraemic patients.
Which access is typically used for the first dialysis session?
A central venous dialysis catheter, internal jugular preferred, because an arteriovenous fistula takes weeks to mature and cannot be needled safely at initiation.
What is dialysis disequilibrium syndrome and its earliest sign?
A neurological complication of overly rapid solute removal; early signs are headache, nausea and restlessness, progressing to confusion, seizures or coma in severe cases.
How is ultrafiltration handled in the first session?
Conservatively — remove a modest volume at a low rate, spreading a large total overload over successive daily sessions rather than attempting full correction at once.
Which dialysate potassium suits a digitalised patient starting dialysis?
A higher bath of 3 mmol/L, because rapid potassium lowering with a 2 bath predisposes to digoxin-toxic arrhythmias in these patients.