Management of Intermittent Hemodialysis in the Critically Ill Patient

Abstract

Intermittent hemodialysis remains a cornerstone of extracorporeal KRT in the intensive care unit, either as a first-line therapy for AKI or a second-line therapy when patients transition from a continuous or prolonged intermittent therapy. Intermittent hemodialysis is usually provided 3 days per week in this setting on the basis that no clinical benefits have been demonstrated with more frequent hemodialysis. This should not detract from the importance of continually assessing and refining the hemodialysis prescription (including the need for extra treatments) according to dynamic changes in extracellular volume and other parameters, and ensuring that an adequate dose of hemodialysis is being delivered to the patient. Compared with other KRT modalities, the cardinal challenge encountered during intermittent hemodialysis is hemodynamic instability. This phenomenon occurs when reductions in intravascular volume, as a consequence of ultrafiltration and/or osmotic shifts, outpace compensatory plasma refilling from the extravascular space. Myocardial stunning, triggered by intermittent hemodialysis, and independent of ultrafiltration, may also contribute. The hemodynamic effect of intermittent hemodialysis is likely magnified in patients who are critically ill due to an inability to mount sufficient compensatory physiologic responses in the context of multiorgan dysfunction. Of the many interventions that have undergone testing to mitigate hemodynamic instability related to KRT, the best evidence exists for cooling the dialysate and raising the dialysate sodium concentration. Unfortunately, the evidence supporting routine use of these and other interventions is weak owing to poor study quality and limited sample sizes. Intermittent hemodialysis will continue to be an important and commonly used KRT modality for AKI in patients with critical illness, especially in jurisdictions where resources are limited. There is an urgent need to harmonize the definition of hemodynamic instability related to KRT in clinical trials and robustly test strategies to combat it in this vulnerable patient population.

Debate: Intermittent Hemodialysis versus Continuous Kidney Replacement Therapy in the Critically Ill Patient: The Choice Should Be Evidence Based

“…7 As a matter of fact, some but not all studies 6 reported delayed kidney function recovery with intermittent HD. Intermittent HD, if administered for 3-4 hours every session using parameters (in particular ultrafiltration rate) usually prescribed for stable end-stage kidney disease patients, 8 causes rapid plasma solute clearance provoking a decrease in plasma osmolality and free water movement from the intravascular to the interstitial and intracellular compartments, which have relatively higher osmolality. 7 In addition, the rate of ultrafiltration may exceed that of plasma refilling from interstitium and contribute to occurrence of hypotension.…”

“…11 A recent review insisted on this aspect. 8 In our era of evidence-based medicine, it is noteworthy that conclusions from previous observational and even randomized controlled trials (RCTs) comparing treatment methods date back at least 15 years. [12][13][14][15] Their validity can be challenged for two main reasons.…”

“…7,9 This aspect is discussed in more detail in the chapters devoted to description of techniques. 8,10 By providing a more progressive equilibration, CKRT may be associated with better hemodynamic stability. Interestingly, a before-after study showed that simple interventions (inspired by KRT practices in end-stage kidney disease) such as isovolemic initiation of KRT, reduced dialysate temperature, preferential use of bicarbonate buffer, sodium profiling (i.e., dialysate [Na1] .145 mmol/L), and conservative initial ultrafiltration dramatically improved the hemodynamic tolerance of intermittent HD.…”

Renal medicine in the intensive care unit: a narrative review

“…In those with more severe AKI, approximately 70% require treatment and AKI severe enough to require kidney replacement therapy is associated with mortality rates of up to 50% [3,60]. often by the bedside, to allow production of dialysate water [64,65]. This has led to an increase in the use of prolonged intermittent techniques which provide the benefits of haemodynamic stability with reduced treatment times.…”

Volume Management with Kidney Replacement Therapy in the Critically Ill Patient

“…Just as the presence of fluid responsiveness may not rule out fluid toxicity, the toxicity from fluid does not ensure that its removal will be well tolerated. As recent reviews have described, 69,70 classic strategies to mitigate hemodynamic instability—such as higher dialysate sodium concentration, ultrafiltration profiling, isolated ultrafiltration, and cooled dialysate—have limited data that are largely extrapolated from the outpatient setting. Among the various strategies, cool dialysate temperature has the best evidence base and is already widely used.…”