Apheresis - Practicals Flashcards
What volumes are normally exchanged for TPEs? Harvests?
TPE: 1-1.5x TPV
Harvests: 2-6x TPV
What replacement fluids can be used for apheresis?
Saline, albumin, plasma, RBCs
In which circumstances should a red cell prime be used?
When ECV or ERCV exceeds 15% of TBV/RCV or when the intraoperative crit would drop below 24%. Or, to constitute a simple transfusion otherwise.
What is the “best” central line site?
No best choice.
Femoral: there is no risk to the mediastinal structures, but infection risk is higher.
IJ: Right is preferred over Left (more straight path, less chance of traversing the azygos root)
How are the two lines on a dialysis catheter distinguished?
The red catheter is shorter and thicker and is meant for drawing (inlet). The blue catheter is longer and is meant for return.
Can the same arm be used for both inlet and return when performing apheresis over PIVs?
Yes, but the return should be downstream of the inlet.
How should central lines be maintained?
The dressing should be kept clean and changed often. Heplocks should be used (if >1000u used, draw off before use to avoid systemically anticoagulating patient).
What is recirculation? How much is normally tolerated?
Direct re-draw of blood coming on from the return line. Up to 10% is typical and tolerable.
How do reactions to ethylene oxide present? How should they be managed?
Burning sensation in the eyes with periorbital edema. Prevent by better priming the circuit with saline or using an ethylene-oxide-free kit.
What effect does apheresis have on clotting factors?
Reduces clotting factors by 40-70%; most factors recover in 1-2 days but fibrinogen takes 2-3.
What is Gilcher’s rule of 5s?
Consider an athletic man: 75mL blood/kg bodyweight. Subtract 5mL for normal>thin>obese, and another 5mL for female sex.
How are citrate and heparin metabolized in apheresis?
Citrate normally has very high first-pass effect, but it may accumulate in patients with hepatic disease (monitor iCa). Heparin is more slowly metabolized.
How should exchange in cryoglobulinemic patients be handled?
Used blood warmers, blanket the patient, use warmed components… Warm everything up.
How does pregnancy affect volumes, and how does it affect apheresis procedures?
TBV increases by 40%, but TPV increases by 45-55% resulting in RCV going up by only 20-30% and the crit actually decreasing. Lay patients on their left sides to prevent uterine compression of the ICV.
What drug metabolisms should be considered during apheresis?
Antihypertensives, anticonvulsants, antiarrhythmics, pressors (to a lesser extent; most are short-lived)
What drives hypocalcemia in apheresis?
Binding by calcium, but also binding by replacement albumin (“stripped albumin”). Alkalosis can also make it worse.
Compare and contrast calcium gluconate and calcium chloride for replacement.
Calcium chloride has more calcium per gram (272mg/g) than calcium gluconate (93mg/g) but requires central line administration and cardiac monitoring.
How do plasma proteins redistribute to and from the extravascular space?
Enter extravascular space via simple diffusion but moreso pinocytosis. Leave extravascular space via lymphatics or pinocytosis.
Compare and contrast the catabolic pattern of IgG and IgM.
IgG is metabolized in a first-order fashion (rate of metabolism is dependent on concentration). IgM is metabolized in a zero-order fashion (concentration-independent, amount per unit time)
Why do exchanges in paraproteinemias tend to appear less efficient than expected?
Paraproteins tend to increase the intravascular volume due to oncotic forces. The TPV is often underestimated.
Compare and contrast the distribution of IgG, IgA, and IgM.
IgG is 45% intravascular.
IgA is 42% intravascular.
IgM is 76% intravascular.
How quickly does complement recover in plasma? Coagulant proteins?
Complement mostly recovers in 1 day, as do most coagulation factors. Fibrinogen takes a bit longer (2-3 days).
In what patients should plasmapheresis be performed with plasma as the replacement fluid?
Patients at risk of hemorrhage, and patients with thrombotic microangiopathies (eg. TTP).
How are electrolyte levels affected by plasma exchange?
Urate and potassium tend to fall. Glucose and bicarbonate do not. Sodium and chloride stay the same due to isotonicity of replacement fluid.
How does plasma exchange affect red cell, white cell, and platelet counts?
Red cells may fall slightly (happens with 5% albumin but not with plasma?). White cells transiently increase due to dislodging of marginated pool. Platelets experience a 25-33% reduction and take 2 days to recover.
How many rounds of exchanges should be performed to treat an IgG-mediated disease? An IgM-mediated disease? How long should you wait between procedures?
IgG: 4-6 times, every 1-2 days
IgM: 3-4 times, every day
Why does citrate bind calcium?
Citrate has 3 negatively charged carboxyl groups, two of which can complex with cations.
How is body calcium mostly stored? In what forms is plasma calcium found?
Mostly in bones as hydroxyapatite. Plasma calcium is 40% albumin/protein bound, 13% complexed, and 47% ionized (free).
What are some possible severe complications of citrate toxicity?
From hypocalcemia: Spasms (carpopedal, Chvostek/Trousseau), laryngospasm, QT prolongation.
Note: Hypomagnesemia can also result, but this isn’t usually an issue.
What is the effect of citrate infusion on acid balance?
Citrate binds free hydrogen, causing a metabolic alkalosis. This is worse in renal failure or with plasma replacement (more citrate).
At what WB:AC ratio does platelet clumping occur?
18:1
What is the usual prime volume of an apheresis circuit?
170-200mL.
What proteins may be activated by filtration surface contact?
Complement, kinins
What are the most common side effects resulting from apheresis procedures?
Citrate toxicity Vasovagal effects (bradycardia, hypotension, diaphoresis, sometimes nausea/vomiting, defecation, and convulsions).
What are the side effects of hetastarch?
Weight gain, anemia, abnormal coags. Never really clears bone marrow…
How much protein is removed in a typical 1x TPV TPE?
110g albumin (-15g with 5% albumin) 40g of other proteins
What is the rationale behind rheopheresis?
Removal of proteins to affect blood viscosity and cellular aggregation to affect circulation in microvasculature. Used for prevention of wet AMD in Europe but not well-proven.
How does immunoadsorption work?
Nonspecifically remove antibodies usually using staph protein agarose columns.
What conditions may be treated by immunoadsorption?
In the US? None. But literature has described use in…
- Renal transplant (pre and post)
- Coagulation factor inhibitors
- Dilated cardiomyopathy (associated with autoantibodies)
What is the primary downside of immunoadsorption?
Because of serious contact activation, most patients will experience side effects including nausea/vomiting, hypotension, pain…mercury poisoning?
What different immunoadsorption instruments are in use?
Ig-Therasorb (sheep anti-IgG column)
Selesorb (dextran sulfate column)
Immusorba (tryptophan/phenylalanine column)
What is the only specific immunoadsorption column in use?
Glycosorb: Removes isohemagglutinins for pre-transplant. Europe only.
Why is TPE not the best for treating familial hypercholesterolemia?
Removes LDL, but also removes cardioprotective HDL.
What are the indications to treat familial hypercholesterolemia with LDL pheresis?
Homozygous patients (with >500 LDL) Heterozygous patients (with >300 failing medication or with evidence of coronary artery disease)
What are the indications for LDL pheresis besides hypercholesterolemia?
FSGS, sudden sensorineural hearing loss, maybe acute stroke/MI?
What are the 5 methods available for LDL pheresis?
Dextran column (liposorber LA-15) Dextran direct perfusion (liposorber D) HELP (heparin precipitation) Immunoadsorption (sheep anti-human-LDL) DALI (polyacrylamide column)
What methods of LDL pheresis are approved for use in the USA?
Dextran-sulfate column (all around better)
HELP
What is the mechanism of removal of LDL using HELP?
Heparin precipitates out ApoB100 and Lp(a) at acidic pH (5.12).
How much LDL is removed with a 3x TPV exchange using DS-A column? Other proteins?
85% of LDL and Lp(a)
5% of HDL
Fibrinogen not significantly reduced.
What are McLeod’s criteria?
REquirements to indicate for apheresis: 1. Need clear understanding of pathophysiology, 2. Abnormality should be correctable by apheresis, 3. Clinical evidence demonstrates improved outcomes.
How is intraprocedural hematocrit calculated?
(Patient crit * TBV) / (TBV + ECV)
What are the 4 major goals of apheresis?
Remove a pathogenic substance
Replace a missing substance
Modulate cellular function
Collect a product
What is the difference between plasma exchange and plasmapheresis?
Plasma exchange is larger volume (>1L).
What needle gauges are needed to perform apheresis over peripherals?
17ga access
18ga return
In what settings is heparin anticoagulation preferable to ACD?
Small children
Patients with metabolic alkalosis
Patients in renal failure
What adverse reactions may be seen during apheresis?
Citrate toxicity Allergic reaction Respiratory difficulty (TRALI, anaphylaxis, ethylene oxide?) Hypotension Coagulopathy, hemolysis... (rare)
What effect does ECP have on the adaptive immune system?
Induces monocyte differentiation into dendritic cells
Alters T-cell subsets
Alters cytokine profiles
How does the citrate content of FFP compare to 5% albumin?
About 4 times the citrate load.
