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.
