Which Modality is Best? IHD is a shorter treatment (2 to 4 hours), typically performed three times per week but as often as daily. Fluid and electrolyte clearance is rapid, making IHD very efficient but increasing the risk for complications, such as hemodynamic instability. Furthermore, the abrupt fluid and electrolyte shifts associated with IHD do not mimic native kidney function. Providing slower treatments delivered continuously over 24 hours has many benefits.
Continuous renal replacement therapy (CRRT) provides clearance of large amounts of fluid and electrolytes over 24 hours, with minimal hemodynamic disturbances. This allows for more gradual shifts in volume and electrolyte levels, reducing the potential for ischemic damage to the kidney and other organs. Also, CRRT more closely replicates normal renal function than IHD.
CRRT is now extremely safe and efficient, although it has been difficult to prove its superiority to IHD in regard to mortality. While there may be no actual benefit to CRRT, it is also likely that its benefit is observed only in certain subsets of patients with renal failure. For example, we do have compelling evidence of increased intracranial pressure during IHD; CRRT is much safer for patients at risk for this development.1 It is also possible that we need to further improve CRRT systems and delivery in order to see a benefit.
Because current data favor neither CRRT nor IHD, most experts recommend choosing a therapy based on patient characteristics. For instance, hemodynamically unstable patients commonly receive generous amounts of fluid daily (antibiotics, nutrition, etc), and thus are often better suited for CRRT because it is more likely to remove higher volumes of fluid successfully, and less likely to contribute to hemodynamic instability than IHD. Conversely, patients with acute electrolyte deviations may benefit more from the rapid electrolyte removal IHD provides.
Additionally, stable patients may be more suitable candidates for IHD because of location (CRRT requires intensive care monitoring) and other variables.2,3 Results from multiple studies have suggested that CRRT may also provide renal protection and consequently improve renal recovery. However, this evidence is not conclusive; the possibility needs further evaluation.1
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