Acute Hemodialysis Prescription
R2吳佳哲
The hemodialysis prescription
Rx：Acute hemodialysis
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Session length：Perform hemodialysis for 4 hours
Blood flow rate：350 mL per minute
Dialyzer
Dialysis solution composition (variable)
Dialysis solution flow rate：500 mL per minute
Dialysis solution temperature：35–36°C
Fluid removal orders：
• Use ultrafiltration control device
• Remove 2.2 L over 4 hours at a constant rate
 Anticoagulation orders：
Reduce the amount of dialysis for the
initial one or two sessions
For 1st hemodialysis：
 Dialysis session length and blood flow rate should
both be reduced
 Target of BUN reduction ratio：<40%
• As 250ml/min for 2 hours
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 Longer initial dialysis session or use of excessively
high blood flow rates (excessively rapid removal of blood solutes)
• Disequilibrium syndrome：obtundation, seizure and coma,
during or after dialysis
• Risk of disequilibrium syndrome：high serum BUN in predialyisis
Reduce the amount of dialysis for the
initial one or two sessions
For 2nd hemodialysis
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 Dialysis session can be increased to 3 hours when
pre-dialysis serum BUN < 100mg/dl
 Length of single dialysis treatment rarely exceeds 6
hours unless dialysis for drug overdose
 Slow low-efficiency hemodialysis (SLED)：low
blood and dialysis solution flow rates and longer
sessions for more safely removal of fluid
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Ultrafiltration coefficient (KUf)
Machine without volumetric ultrafiltration
controllers：
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 Membrane with a relatively low water permeability
(KUf)
 Transmembrane pressure (TMP) should be set at a
relatively high level to remove amount of fluid
 Close monitoring of fluid removal rate is required
Choosing the dialysis solution
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Dialysis solution bicarbonate
concentration level
Dialysis solution sodium level
Dialysis solution potassium level
Dialysis solution calcium level
Dialysis solution magnesium level
Dialysis solution dextrose level
Dialysis solution phosphate level
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Dialysis solution bicarbonate
concentration level
Intensive care unit patients often are
relatively alkalotic
 Prescriptions for “standard” bicarbonate dialysis
solution：containing 35–38 mM
 Should not be used without first carefully evaluating
acid–base status
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Pre-dialysis plasma bicarbonate level > 28
mM or respiratory alkalosis
 Custom dialysis solution：containing appropriately
lower bicarbonate level (20–28 mM, depending on
the degree of alkalosis)
Dialysis solution bicarbonate
concentration level
Dangers of metabolic alkalosis
 Alkalemia (blood pH >7.50) is more dangerous than
acidemia
 Dangers of alkalemia：
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• Soft tissue calcification
• Cardiac arrhythmia (sometimes with sudden death)
• Adverse symptoms：nausea, lethargy, and headache
Dialysis solution bicarbonate
concentration level
Dangers of metabolic alkalosis
 Cause of metabolic alkalosis
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Reduced intake of protein
Intensive dialysis for any reason (e.g., daily dialysis)
Vomiting or nasogastric suction
Administer lactate or acetate with total parenteral nutrition
(TPN) solutions, or citrate due to citrate anticoagulation
• Coadministration of aluminum hydroxide with sodium
polystyrene sulfonate resin
Dialysis solution bicarbonate
concentration level
Pre-dialysis respiratory alkalosis
 Cause of respiratory alkalosis with normal renal
function
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• Pulmonary disease (pneumonia, edema, embolus)
• Hepatic failure
• Central nervous system disorders
 An acute decrease in the plasma bicarbonate level
due to release of hydrogen ions from body buffer
stores
 In normal renal function delayed (2–3 days)
compensatory fall in plasma bicarbonate level due
to excretion of bicarbonate in the urine
Dialysis solution bicarbonate
concentration level
Pre-dialysis respiratory alkalosis
 Therapeutic goal：
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• Normalize the pH rather than the plasma bicarbonate level
• In respiratory alkalosis, the plasma bicarbonate level at
which the blood pH will be normal may be as low as 17–
20 mmol/L
• Dialysis solution should contain less than usual amount of
bicarbonate to achieve a post-dialysis plasma bicarbonate
level in the desired subnormal range
Dialysis solution bicarbonate
concentration level
Patients with severe pre-dialysis acidosis
 Dangers of excessive correction of metabolic
acidosis
• Excessive correction of severe metabolic acidosis (starting
plasma bicarbonate level <10 mmol/L)
• Adverse consequences
– Paradoxical acidification of the cerebrospinal fluid
– Increase in tissue production rate of lactic acid
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• Initial therapy should aim for only partial correction of the
plasma bicarbonate level
– Target post-dialysis plasma bicarbonate value of 15–20
mmol/L
– For severe acidosis：dialysis solution bicarbonate level of
20–25 mM
Dialysis solution bicarbonate
concentration level
Patients with severe pre-dialysis acidosis
 Respiratory acidosis
• The normal compensation to respiratory acidosis
– Acute buffer response：increase plasma bicarbonate level
by 2–4 mmol/L
– Delayed (3–4 days)：increase in renal bicarbonate
generation
• Because 2nd response is obviated in dialysis patients
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– Respiratory acidosis have more pronounced effect on blood
pH
– Dialysis solution bicarbonate levels should be at the higher
range to keep pH in the normal range
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Dialysis solution sodium level
Hyponatremia
 Common in seriously illness with acute dialysis
 Primary cause
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• Large amount of hyponatric intravenous solutions
• Hyponatremia with severe hyperglycemia in diabetic
dialysis patients
– For every increase of 100 mg/dL in the serum glucose
concentration decrease of 1.3 mmol/L in the serum
sodium concentration
– Because osmotic shift of water from intracellular to
extracellular compartment
– Correction of hyperglycemia by insulin  reverse initial
water shift and correct the hyponatremia
Dialysis solution sodium level
Hyponatremia
 Pre-dialysis serum sodium level >130 mmol/L
• 4-hour dialysis：post-dialysis serum sodium level of 140
mmol/L can usually be achieved by setting dialysis
solution sodium concentration to 140 + (140 – predialysis
serum sodium value)
– For example, pre-dialysis serum sodium level is 130 mmol/L,
to attain normonatremia the dialysis solution sodium
concentration should be 150 mM (140 + [140 – 130])
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• Overcorrection or undercorrection of serum sodium level
results if an unusually intense or mild dialysis treatment
Dialysis solution sodium level
Hyponatremia
 Pre-dialysis serum sodium level <130 mmol/L
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• Rapid correction  potential fatal neurologic syndrome
(osmotic demyelination syndrome)
• Maximum safe rate of correction of serum sodium
concentration：controversial
• To set dialysis solution sodium level < 15–20 mM above
plasma level
• Goal of correcting hyponatremia during multiple dialysis
treatments performed over several days
Dialysis solution sodium level
Hypernatremia
 Less common than hyponatremia in hemodialysis
 Usually in a context of
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• Dehydration
• Osmotic diuresis
• Failure to give sufficient electrolyte-free water
Dialysis solution sodium level
Hypernatremia
 Dialysis solution sodium level > 3–5 mM lower than
the plasma value  three complications
• Hypotension
– Osmotic contraction of plasma volume occurs as water
shifts from dialyzed blood (containing less sodium than
before) to relatively hyperosmotic interstitium
• Muscle cramps
• Cerebral edema and disequilibrium syndrome
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– Water from dialyzed, relatively hyponatremic blood enters
cells
Dialysis solution sodium level
Hypernatremia
 Risk of disequilibrium syndrome
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• Use of low-sodium dialysis solution should certainly be
avoided in high pre-dialysis serum BUN level is high (>
100 mg/dL)
• Safest approach：1st dialyze with dialysis solution sodium
level close (within 2 mM) to that of plasma
• Correct hypernatremia by slow administration of slightly
hyponatric fluids
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Dialysis solution potassium level
Usual dialysis solution K concentration for
acute dialysis：
 2.0–4.5 mM
Hypokalemia：
 Complication of TPN
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Correction of severe acidosis during
dialysis
 shift of K into cells
 lowering plasma K
 hypokalemia and arrhythmia
Dialysis solution potassium level
Pre-dialysis serum K <4.0 mmol/L
 Dialysis solution K：≧ 4.0 mM
Pre-dialysis plasma K >5.5 mmol/L
 Dialysis solution K：
• 2.0 mM for stable patients
• 2.5 ～ 3.0 mM for risk for arrhythmia or receiving digitalis
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Pre-dialysis plasma K >7.0 mmol/L
 Dialysis solution K：＜ 2.0 mM
 Monitor plasma K：hourly
 Consider danger of precipitating arrhythmia when
plasma K is lowered too rapidly
Dialysis solution potassium level
Potassium rebound
 Marked rebound increase in serum K：within 1–2
hours after dialysis
 Don’t treat post-dialysis hypokalemia with K
supplement
Acute hyperkalemia
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 EKG change (low P, peaked T, widening QRS,
cardiac standstill), weakness and lethargy
 Treatment：
• Calcium chloride or calcium gluconate (intravenous
infusion)
• Glucose plus insulin (intravenous)
• Albuterol (intravenous or inhaled)
Dialysis solution potassium level
Subacute hyperkalemia
 Careful review of diet for high-potassium food
 Reduce alimentary K intake
 Oral administration of sodium–potassium exchange
resin (sodium polystyrene sulfonate)
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• With or mixed with sorbitol  prevent constipation
• Several reports：intestinal necrosis associated with
sorbitol and oral sodium polystyrene sulfonate
Dialysis solution potassium level
Potassium removal and dialysis solution
glucose
 K removal during dialysis
• Glucose-free dialysis solution：
– May be 30% greater than K removal using a 200 mg/dL
glucose solution
– May be decreased intradialytic translocation of K into cells
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• Use of a dialysis solution containing 100 mg/dL glucose
may be the best option
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Dialysis solution calcium levels
Normal level for acute dialysis：
 1.5–1.75 mM (3.0–3.5 mEq/L)
Dialysis solution Ca <1.5 mM (3.0 mEq/L)
 Predispose to hypotension during dialysis
Pre-dialysis hypocalcemia
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 Use high dialysis solution calcium
 Correction of acidosis  lowering of ionized
plasma Ca (with possible precipitation of seizures)
Dialysis solution calcium levels
Dialytic treatment of acute hypercalcemia
 Hemodialysis can be effective in lowering serum
Ca for hypercalcemia
 Ca concentration：1.25～1.75 mM (2.5–3.5 mEq/L)
• At least 1.25 mM (2.5 mEq/L) Ca to minimize the
possibility of an overly rapid decrease in serum ionized Ca
(which can cause tetany or seizure)
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 Frequent measurement of serum ionized Ca and
physical examination during dialysis to avoid these
complication
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Dialysis solution magnesium levels
Usual dialysis solution Mg：
 0.25～0.75 mM (0.5–1.5 mEq/L)
Magnesium
 Vasodilator
 Study for blood pressure control in acute dialysis
• Dialysis solution Mg：0.375 mM (0.75 mEq/L) better than
0.75 mM (1.5 mEq/L) Mg Roy and Danziger, 1996
• Higher dialysis solution Mg  Kyriazis et al., 2004
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 The best dialysis solution Mg for acute dialysis in
terms of blood pressure maintenance：unknown
Dialysis solution magnesium levels
Hypomagnesemia
 Cause：
• Malnourished
• Receiving TPN (due to shifting of Mg into cells during
anabolism)
 Manifestation：
• Cardiac arrhythmia
• Impair release and action of parathyroid hormone (PTH)
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 Monitor serum Mg during TPN and TPN fluids
should be supplemented routinely with Mg
Dialysis solution magnesium levels
Hypermagnesemia
 Cause：
• Accidental
• Covert use of Ma-containing laxatives, enema, or antacid
 Manifestation：
• Hypotension
• Weakness
• Brady-arrhythmia
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 Treatment：
• Cessation of ingestion of magnesium-containing
compounds
• Hemodialysis to lower serum Mg
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Dialysis solution dextrose level
Dialysis solution for acute dialysis：
 Dextrose (100–200 mg/dL; 5.5–11 mmol/L)
 Risk for severe hypoglycemia：
• Sepsis
• Diabetes mellitus
• Receiving β-blocker
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 Addition of dextrose to the dialysis solution reduce
risk of hypoglycemia and lower incidence of
dialysis-related side effects
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Dialysis solution phosphate level
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Phosphate is normally absent from the
dialysis solution, and justifiably so, as
patients in renal failure typically have
elevated serum phosphate values
Large-surface-area dialyzer and a longer
dialysis session increase amount of P
removed during dialysis
Dialysis solution phosphate level
Hypophosphatemia
 Pre-dialysis hypophosphatemia：
• Malnourished, Receiving hyperalimentation, Intensively
dialyzed for any purpose
• Aggravated by dialysis against zero-P bath
 Manifestation：
• Respiratory muscle weakness
• Alteration in hemoglobin oxygen affinity
• Respiratory arrest during dialysis
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 Treatment：
• Add P to dialysis solution
• Intravenous P, to avoid overcorrection and hypocalcemia
Dialysis solution phosphate level
Adding phosphorus to bicarbonatecontaining dialysis solutions
 For prevention of hypophosphatemia
• Add P in final dialysis solution as 1.3 mmol/L (4 mg/dL)
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 P cannot be added to acetate-containing dialysis
solutions because of Ca-Mg-PO4 solubility
problems
 P can be added to bicarbonate-containing dialysis
solution (no contain calcium or magnesium)
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Choosing dialysis solution flow rates
For acute dialysis
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 Usual dialysis solution flow rate is 500 mL/min
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Dialysis solution temperature
Usual：
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 35–37°C
 Lower temperature should be used in hypotensionprone patients
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Ultrafiltration orders
Fluid removal：0–5 kg / dialysis session
Guidelines for ultrafiltration orders
 Quite edematous and pulmonary edema
• Rarely need removal of > 4L of fluid during initial session
• Remaining excess fluid is best removed during a second
session the following day
 Without edematous and pulmonary edema
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• No pedal edema, anasarca, or pulmonary congestion ：
not need to remove >2–3 L over the dialysis session
• Little or no jugular venous distension  zero fluid removal
 脫水需加約0.2L
• At the end of dialysis in the form of saline to rinse the
dialyzer
• Any other fluid ingested or administered during H/D
Ultrafiltration orders
Guidelines for ultrafiltration orders
 As initial dialysis
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• Dialysis session：limited to 2 hours
• For a large amount of fluid (e.g., 4.0 L) must be removed
– Impractical and dangerous to remove over a 2-hour period
– Isolated ultrafiltration (1–2 hours, 2–3 kg of fluid), then
dialysis for 2 hours, removing remainder of desired fluid
– Severe e- abnormality：先dialysis，再isolated ultrafiltration
– Dialysis with reduced blood flow rate and removing fluid
1L/h for 4–5 hours
– Blood flow rates < 200 mL/min through adult-size dialyzer：
increase risk of dialyzer clotting  change to small-surfacearea dialyzer
Ultrafiltration orders
Guidelines for ultrafiltration orders
 Best：removal of fluid at a constant rate
 Na in dialysis solution < serum Na：
• Ultrafiltration rate should initially be reduced to
compensate for osmotic contraction of blood volume that
will occur as the plasma sodium concentration is being
lowered
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 In acute renal failure
• Important to avoid hypotension at all times
• In rat model (Kelleher et al.(1987))：renal autoregulatory
response to systemic hypotension is greatly impaired
• Hypotension caused by blood withdrawal caused further
renal damage and delay of functional renal recovery
Ultrafiltration orders
Impact of dialysis frequency on
ultrafiltration needs
 Difficulty to limit fluid gain to <2 L/day
• Often 3 L/day is absorbed in patients receiving parenteral
nutrition
 Daily (6 or 7 times / week) dialysis：
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• Reducing amount of fluid with each dialysis
• Lowering risk of intradialytic hypotension and ischemic
damage
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