Acute Hemodialysis Prescription

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  • 25/1/2014 Acute hemodialysis prescription

    http://www.uptodate.com/contents/acute-hemodialysis-prescription?topicKey=NEPH%2F1854&elapsedTimeMs=17&source=search_result&searchTerm= 1/15

    Official reprint from UpToDate www.uptodate.com 2014 UpToDate

    AuthorsPhillip Ramos, MD, MSCIMark R Marshall, MDThomas A Golper, MD

    Section EditorsJeffrey S Berns, MDPaul M Palevsky, MDRichard H Sterns, MD

    Deputy EditorAlice M Sheridan, MD

    Acute hemodialysis prescription

    Disclosures

    All topics are updated as new evidence becomes available and our peer review process is complete.Literature review current through: Dec 2013. | This topic last updated: ene 9, 2013.

    INTRODUCTION Acute renal failure (ARF) is a major cause of morbidity and mortality, particularly in the

    hospital setting. Despite improvements in renal replacement therapy (RRT) techniques during the last several

    decades, the mortality rate associated with ARF in critically ill patients remains above 50 percent. (See "Renal

    and patient outcomes after acute tubular necrosis".)

    RRT is ideally initiated in the acute setting prior to the dangerous accumulation of extravascular volume and/or

    uremic toxins that can result in further multi-organ damage and failure. Once the decision to initiate RRT has

    been made, the specific modality of dialytic support must be chosen. This consists of peritoneal dialysis,

    intermittent hemodialysis (IHD) and its variations (eg, hemofiltration), and continuous RRT (CRRT). Once the

    selection is made, the acute dialysis prescription can be determined.

    An acute hemodialysis treatment is defined as a hemodialysis session specifically performed for ARF (also

    known as acute kidney injury [AKI]) or in the setting of a hospitalized end-stage renal disease (ESRD) patient.

    The choice of specific dialysis modality, particularly the choice between continuous or intermittent dialysis, is

    discussed separately. (See "Continuous renal replacement therapy in acute kidney injury (acute renal failure)".)

    The various components of the acute hemodialysis prescription will be described here. The use of peritoneal

    dialysis in ARF is discussed separately (see "Use of peritoneal dialysis for the treatment of acute kidney injury

    (acute renal failure)").

    INDICATIONS The urgent indications for renal replacement therapy (RRT) in patients with acute renal failure

    (ARF) generally include volume overload refractory to diuretics, hyperkalemia, metabolic acidosis, uremia, and

    toxic overdose of a dialyzable drug. In an attempt to minimize morbidity, dialysis should be started prior to the

    onset of overt complications of renal failure, whenever possible. This is discussed in detail separately. (See

    "Renal replacement therapy (dialysis) in acute kidney injury (acute renal failure) in adults: Indications, timing,

    and dialysis dose", section on 'Indications for and timing of initiation of dialysis'.)

    MODALITY Once the decision to initiate renal replacement therapy (RRT) has been made, the specific

    modality of dialytic support must be chosen. The possibilities include peritoneal dialysis, intermittent

    hemodialysis (IHD) and its variations (eg, hemofiltration), and continuous RRT (CRRT). Once this selection is

    made, the acute dialysis prescription can be determined. The determining factors of which modality is chosen

    include the catabolic state, hemodynamic stability, and whether the primary goal is solute removal (eg, uremia,

    hyperkalemia), fluid removal, or both. This is reviewed elsewhere. (See "Renal replacement therapy (dialysis) in

    acute kidney injury (acute renal failure) in adults: Indications, timing, and dialysis dose".)

    VASCULAR ACCESS When acute hemodialysis is chosen as the dialytic support modality, vascular access

    must be established prior to initiating treatment. Placement of the venous dialysis catheter must be considered

    carefully, especially in the critically ill patient.

    The location depends upon factors such as body habitus, whether the patient is ambulatory or bedridden,

    presence of vascular disease or atypical anatomy, and the avoidance of specific complications in an at-risk

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    patient (eg, risk of pneumothorax while placing a subclavian venous dialysis catheter in a patient with severe

    chronic obstructive pulmonary disease or history of deep vein thrombosis or other venous disease).

    For hospitalized end-stage renal disease (ESRD) patients, daily reassessment of the existing angioaccess (eg,

    arteriovenous graft or fistula) is appropriate. Many events during the hospitalization can jeopardize the existing

    access (eg, hypotension). (See "Overview of central catheters for acute and chronic hemodialysis access".)

    HEMODIALYZER MEMBRANES In the setting of acute renal failure (ARF), the choice of artificial membranes

    utilized may have a bearing on clinical outcome. Previously, it was postulated that non-complement-activating

    membranes may incur less inflammatory risk, with resultant decrease in infectious complications and possibly

    an increased probability of improved restoration of renal function. However, there are inconsistent findings

    concerning the effect of membrane biocompatibility on outcomes among patients with ARF, with several meta-

    analyses reporting disparate results. (See "Renal replacement therapy (dialysis) in acute kidney injury (acute

    renal failure): Recovery of renal function and effect of hemodialysis membrane", section on 'Complement

    activation, membrane biocompatibility, renal recovery, and survival'.)

    Membranes can also be of low or high flux. High-flux membranes contain large pores that allow for enhanced

    permeability of larger molecules [1]. Although this property can enhance removal of putative toxins and improve

    outcome, it could also allow the back transport (from dialysate to blood) of potentially harmful water-borne

    molecules. This property is a factor that confounds some of the conclusions from previously performed studies.

    Certainly, having the purest dialysate water possible should be a goal when using these more porous

    membranes to utilize their positive attributes and to minimize their potential risks.

    Overall, there are theoretical advantages to high-flux biocompatible membranes that have not been consistently

    corroborated by often underpowered or flawed clinical studies. However, the effect of membrane biocompatibility

    on outcomes (when present) is consistently beneficial. In addition, since such membranes can now be obtained

    cheaply, cost has been eliminated as a deciding factor.

    We therefore suggest the following approach:

    (See "Renal replacement therapy (dialysis) in acute kidney injury (acute renal failure): Recovery of renal function

    and effect of hemodialysis membrane", section on 'Complement activation, membrane biocompatibility, renal

    recovery, and survival' and "Renal replacement therapy (dialysis) in acute kidney injury (acute renal failure):

    Recovery of renal function and effect of hemodialysis membrane", section on 'Membranes' and "Maintaining

    water quality for hemodialysis".)

    DIALYSATE COMPOSITION The dialysate solution composition consists of potassium, sodium, bicarbonate

    buffer, calcium, magnesium, chloride, and glucose. Unlike chronic hemodialysis, the dialysate composition in

    acute hemodialysis is routinely altered each treatment to correct the metabolic abnormalities that can rapidly

    develop during acute renal failure (ARF). This is particularly true in the treatment of potassium and/or acid/base

    derangements. Thus, the dialysate potassium, sodium, bicarbonate, and calcium are routinely changed in this

    setting.

    Issues surrounding magnesium, chloride, and glucose include the following:

    If the water system used is high quality, high-flux biocompatible dialysis membranes should be used in the

    ARF setting.

    If the water system is not of high quality, low-flux biocompatible dialysis membranes should be used.

    Another option is the use of in-line membrane filtration devices on dialysis machines to generate ultrapure

    dialysate.

    The usual dialysate magnesium concentration is 0.5 to 1.0 mEq/L and is not usually different from that in

    the chronic setting.

    The amount of dialysate chloride is dependent upon the dialysate sodium and bicarbonate concentrations.

    The standard dialysate glucose concentration is 200 mg/dL, but may be decreased to more efficiently

    lower the serum potassium during hemodialysis.

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    Dialysate potassium concentration There is no standard dialysate potassium concentration in the acute

    hemodialysis prescription because of wide variability in serum potassium prior to initiating the hemodialysis

    session. It is crucial to know the predialysis serum potassium level at the start of the hemodialysis session to

    tailor the dialysate potassium so that normokalemia will be attained with avoidance of hypokalemia.

    The goal of an acute hemodialysis treatment is not necessarily to lower the total body potassium burden for

    general nutritional purposes. Instead, the goals are often more short term, such as normalizing the s