SLED & Prolonged Intermittent

The contract between this chapter and the reader.

1. 1. Define SLED / prolonged intermittent RRT as a hybrid between intermittent HD and CRRT.
2. 2. Describe how it is delivered — extended time, reduced flows, a standard machine.
3. 3. Position it for the moderately unstable patient and resource-limited settings.
4. 4. Prescribe a SLED session (duration, flows, ultrafiltration, anticoagulation).
5. 5. Explain why it is better tolerated haemodynamically than fast intermittent HD.
6. 6. State its advantages over CRRT and its limitations.
7. 7. Use it to transition or wean a patient off CRRT.
8. 8. Adjust drug dosing for prolonged intermittent clearance.

A sixty-second reading. Each bullet stands alone.

• SLED (sustained low-efficiency dialysis), also called prolonged intermittent RRT, is a hybrid between intermittent HD and CRRT.
• It runs on a conventional HD machine over an extended time (about 6–12 hours) with reduced blood and dialysate flows.
• The slow removal gives CRRT-like haemodynamic tolerance with the economy and flexibility of intermittent HD.
• It suits the moderately unstable patient who cannot tolerate fast IHD but does not require, or cannot access, full continuous therapy.
• It allows time off the machine for procedures, transport, and mobilization — flexibility CRRT lacks.
• A typical prescription is 6–12 hours daily or near-daily, with a blood flow of ~150–250 and a dialysate flow of ~300–400 mL/min.
• Ultrafiltration is spread gently over the long session, limiting hypotension.
• It uses existing HD infrastructure and less anticoagulant than 24-hour CRRT.
• It is well suited to resource-limited settings and to weaning a recovering patient off CRRT.
• Outcomes — mortality and renal recovery — are comparable to CRRT, with better tolerance than conventional IHD.
• Its limitations are the gaps between sessions and the need for adequate water treatment or a batch dialysate system.
• Drug dosing must account for the significant clearance delivered during the prolonged session.

The medical core. An expert should agree SLED and prolonged intermittent therapy are fully covered here.

Why it matters at the bedside

Between the fast efficiency of intermittent dialysis and the round-the-clock gentleness of CRRT sits a practical middle ground. SLED takes a standard dialysis machine, slows it right down, and runs it for hours — buying much of CRRT's tolerance at a fraction of its cost and complexity. For many units, and many patients, it is the sensible compromise.

What SLED is

• SLED — sustained low-efficiency dialysis, also called prolonged intermittent renal replacement therapy or extended daily dialysis — is a hybrid. It delivers dialysis slowly over an extended period rather than quickly over a few hours or continuously over a day, capturing the haemodynamic advantage of slow removal without committing to true continuous therapy.

How it is delivered

• It runs on a conventional haemodialysis machine (or one with a batch dialysate system) over roughly 6 to 12 hours, daily or near-daily, with reduced blood flow (around 150–250 mL/min) and reduced dialysate flow (around 300–400 mL/min). The reduced flows are what make the treatment slow and gentle.

Why it is gentle

• Spreading both solute and fluid removal over many hours means smaller shifts per unit time: plasma refilling keeps pace with ultrafiltration, and solute falls gradually. The result is haemodynamic tolerance approaching CRRT's and clearly better than fast intermittent HD, with little risk of disequilibrium.

When to use it

• SLED fits the moderately unstable critically ill patient who cannot tolerate a fast intermittent run but for whom full 24-hour CRRT is either unnecessary or impractical — because of cost, staffing, or resource constraints. It is especially valuable in resource-limited intensive care units that lack dedicated CRRT, and as a step down from CRRT in a patient who is recovering.

The prescription

• Set a duration of 6 to 12 hours, daily or near-daily; a blood flow of about 150–250 and a dialysate flow of about 300–400 mL/min; a standard dialyzer; ultrafiltration spread gently across the whole session to reach the fluid goal; and anticoagulation by heparin, citrate, or none according to bleeding risk. Run for an adequate duration, the delivered dose is comparable to CRRT.

Advantages over CRRT and IHD

• Against CRRT, SLED is cheaper and simpler, uses existing HD infrastructure, needs less nursing intensity and less anticoagulant, and — crucially — leaves the patient free between sessions for procedures, imaging, transport, and mobilization. Against fast intermittent HD, its great advantage is haemodynamic tolerance.

Limitations

• Because it is intermittent, there are gaps when no clearance or fluid removal occurs, which can be a problem in the most severely catabolic or unstable patients; a session that is too short can under-treat; and online SLED requires adequate water treatment, or else a batch dialysate system.

Transitioning from CRRT

• As an unstable patient stabilises on CRRT, SLED is the logical next step — a planned de-escalation that restores mobility and frees ICU resources before a final transition to conventional intermittent HD as recovery continues.

Drug dosing

• The prolonged session delivers significant clearance, so drug dosing — especially antibiotics — must account for it, often by timing doses around the session rather than assuming the intermittent, lower clearance of a short IHD run or the steady clearance of CRRT.

Five fully-built tables.

Table A — IHD versus SLED versus CRRT

Table B — SLED prescription

Table C — When to use SLED

Table D — Advantages and limitations

Table E — Practical considerations

Visualise & Map

Numbered rules. These numbers are the cross-reference handle for the cases and flowcharts.

Clinical Reasoning

Four cases. Each stops you at a decision before it answers it.

Exhaustive. Every rule in the chapter is here.

Safety & Evidence

Panel A — Red flags

Panel B — NEVER DO

Anti-patterns clinicians fall into. Each becomes a Level 22 distractor.

The grade reflects strength of evidence, not importance.

Patient Decisions

Outcomes as natural frequencies. Figures are representative; the direction of effect is given where precise numbers are uncertain.

Apply & Test

Copy-paste chart notes that map to the real decisions in this chapter.

Template 1 — SLED prescription note

• Rationale: moderately unstable / CRRT unavailable / weaning from CRRT / resource setting.
• Duration: ___ h; frequency: daily / near-daily.
• Flows: blood (Qb) ___ mL/min; dialysate (Qd) ___ mL/min (or batch system).
• Dialyzer ___; ultrafiltration goal ___ (spread over the session).
• Anticoagulation: heparin / citrate / none; water/dialysate source verified.

Template 2 — CRRT → SLED → IHD transition note

• Current therapy and stability: ___ (vasopressors? tolerance?).
• Step taken: CRRT → SLED / SLED → IHD; rationale ___.
• Mobilization / procedures enabled: ___.
• Drug dosing reviewed for the new clearance pattern: yes/no.
• Reassessment plan: ___.

Pre-rounds compression. Rules only.

Active recall. At least one card per objective.

Micro-teaching for rounds. Two scenarios, five steps each.

Eight items, each anchored in this chapter. At least one per objective.