Table 3.

Suggestions for preventing and managing HIRRT in critically ill patients

RRT-related factor	Suggestion	Rationale	Comment
Ultrafiltration (fluid removal) rate	Set fluid removal goals to avoid/reduce net positive fluid balance. Check for preload dependence when HIRRT occurs and only reduce ultrafiltration goals if preload dependence is present	HIRRT has many causes beyond just excessive ultrafiltration. As a result, reduction of the ultrafiltration goal is not always the appropriate response to HIRRT (especially for patients with worsening fluid overload)	Starting (or increasing the dose of) a vasopressor or inotrope may be a more appropriate strategy to manage HIRRT when it is unrelated to excessive ultrafiltration
Treatment time	Lengthen treatment times for intermittent RRT modalities if fluid removal is required For example, for intermittent HD, use a minimum 4 h treatment time; for SLED, consider extending usual treatment time	Longer treatment times enable lower ultrafiltration rates to achieve the same ultrafiltration goal. As such, they are more likely to allow for sufficient plasma refilling to prevent HIRRT	For intermittent HD, do not extend treatment time beyond 4–5 h if using conventional dialysate and blood flow rates (may result in dialysis disequilibrium due to overly effective solute clearance) For SLED, consider back-to-back sessions to achieve fluid removal goals if machine software does not allow for treatment time extension
Dose (flow rates)	Start with moderate small solute clearance, especially in patients with significant uremia (hyperosmolality) For example, for intermittent HD, QB ≤ 200 mL/min and QD ≤ 300 mL/min; for CRRT, total effluent rate 20–25 mL/kg/h	More gradual reduction in plasma osmolality induce less fluid shift and promote plasma refilling	Ensure adequate RRT dose once osmolality/uremia has decreased Blood flow rate does not impact small solute clearance in CRRT (more dependent on total effluent rate). Therefore, one should not reduce QB in CRRT to less than usual (~ 150 to 200 mL/min) as clotting risk will increase and no reduction in HIRRT will be achieved
Dialysate sodium concentration	Use higher dialysate sodium concentration for intermittent therapies (HD and SLED): e.g., ≥ 145 mmol/L	Reduced osmolar shift allows for more plasma refilling to occur	Do not employ this strategy in patients with hyponatremia due to risk of overly rapid correction if higher sodium dialysate solutions are used
Dialysate calcium concentration	Consider using higher dialysate calcium concentration (e.g., 1.5 or 1.75 mmol/L) for intermittent therapies (HD and SLED)	Activating calcium-sensing receptors on vascular smooth muscle cells increases vascular tone Higher calcium potentiates cardiac contractility	Some studies have shown that using calcium to correct hypocalcemia in critically ill patients (not requiring RRT) may be harmful. The safety of routinely using higher dialysate calcium concentration in critically ill patients has not been studied
Dialysate temperature	Use cool dialysate for intermittent HD or SLED: i.e., 0.5 °C less than the patient’s temperature (down to a minimum of 35.0–35.5 °C)	Cooling promotes peripheral vasoconstriction and increases blood volume return Also reduces myocardial stunning (presumably leading to improved cardiac output)	Most intermittent HD machines’ software does not allow for dialysate temperature settings < 35.0–35.5 °C (and the safety of using lower temperatures than this has not been studied) Less evidence exists regarding the impact of cooling patients using CRRT as compared to that supporting the use of cool dialysate in SLED and intermittent HD
Buffer	Use a bicarbonate-based buffer (versus lactate-based)	Lactate-based buffers associated with more HIRRT	Acetate-based buffers are no longer used due to increased risk of HIRRT

CRRT continuous renal replacement therapy, HD, RRT renal replacement therapy, hemodialysis, SLED sustained low-efficiency dialysis, HIRRT hemodynamic instability related to RRT, Q_B blood flow rate, Q_D dialysate flow rate, ESKD end-stage kidney disease