Sustained Low-Efficiency Dialysis, or SLED, is a specialized form of renal replacement therapy primarily used in the intensive care unit (ICU) for patients experiencing acute kidney failure. This technique acts as a bridge between the two traditional types of dialysis, offering a unique balance between efficiency and patient tolerance. SLED’s defining feature is its gentle, prolonged duration, which makes it particularly suitable for critically ill patients who cannot withstand the rapid physiological shifts of standard treatments. It allows for the effective removal of waste products and excess fluid over an extended period.
The Spectrum of Dialysis Treatment
SLED is positioned as a hybrid therapy within the range of options for kidney support, which includes Intermittent Hemodialysis (IHD) and Continuous Renal Replacement Therapy (CRRT). IHD is characterized by short, high-intensity sessions, typically lasting about three to four hours, and is designed to rapidly clear solutes and remove fluid from the body. This fast-paced clearance requires high blood and dialysate flow rates, which can sometimes lead to sudden drops in blood pressure in vulnerable patients.
CRRT represents the opposite end of the spectrum, providing very slow and continuous therapy over a 24-hour period. Its low-intensity approach is the gentlest on the cardiovascular system, making it the preferred choice for patients with severe hemodynamic instability. However, CRRT is resource-intensive and often requires continuous monitoring, which can restrict patient mobility and access for other procedures.
SLED occupies the middle ground, borrowing attributes from both modalities. It runs for an extended duration, usually between six and twelve hours, which is longer than IHD but shorter than CRRT. This extended time allows for lower blood and dialysate flow rates compared to IHD, resulting in a gradual and sustained rate of solute and fluid removal. SLED provides effective detoxification while being better tolerated by patients who are mildly to moderately hemodynamically unstable.
How the SLED Treatment Session Works
The SLED session is designed for gradual detoxification, typically running for eight to twelve hours, often performed daily or every other day depending on the patient’s metabolic needs. A primary advantage of this longer duration is the flexibility it offers, as the treatment can be scheduled overnight, allowing the patient to be mobile and available for diagnostic tests or therapeutic procedures during the day. The procedure uses the same standard hemodialysis machines found in most hospitals, but the settings are adjusted to accommodate the slower, sustained approach.
The “low efficiency” aspect is achieved by significantly reducing the flow rates of both blood and dialysate compared to standard IHD. Blood flow rates are typically set between 100 to 200 milliliters per minute, and dialysate flow rates are often around 100 to 300 milliliters per minute. These reduced rates ensure that waste products and excess fluid are removed gently over the extended session, minimizing the physiological stress on the patient’s body.
Throughout the prolonged session, patient monitoring is maintained to carefully manage fluid removal, known as ultrafiltration. The slower ultrafiltration rate prevents the rapid fluid shifts that can trigger complications like hypotension in unstable patients. Anticoagulation is often necessary to keep the blood circuit from clotting during the extended treatment time, though the specific agent is chosen based on the patient’s specific risks and condition.
Clinical Rationale for Choosing SLED
The primary reason for selecting SLED over other modalities is the patient’s hemodynamic status, particularly in the intensive care unit setting where acute kidney injury is common. Critically ill patients, especially those with sepsis or multi-organ failure, often have low or fluctuating blood pressure, making them poor candidates for the rapid fluid and solute removal of Intermittent Hemodialysis. The sudden removal of a large volume of fluid during a short IHD session can lead to dangerous drops in blood pressure, potentially causing further organ damage.
SLED’s sustained, gentle fluid removal minimizes the risk of hypotension because the body has more time to physiologically adjust to the fluid loss. The slow ultrafiltration rate prevents the abrupt decrease in circulating blood volume that can destabilize the cardiovascular system. This makes SLED a safer choice for patients who require ongoing support with vasoactive medications to maintain their blood pressure.
Furthermore, SLED is beneficial for managing severe fluid overload that is resistant to diuretics. By providing sustained fluid removal over many hours, it can achieve the necessary volume control without compromising the patient’s stability. Although CRRT is also well-tolerated hemodynamically, SLED is often preferred due to its lower cost, reduced resource consumption, and the use of widely available standard dialysis equipment.
SLED serves as a flexible, intermediate option in the management of kidney failure for critically ill patients. It effectively balances the need for efficient toxin and fluid clearance with the necessity of patient tolerance, particularly concerning cardiovascular stability.