Storage: properties of stored products (storage lesion)

6 ASCP MLS practice questions on Storage: properties of stored products (storage lesion), part of Blood Banking. The first 6 are below; the first 5 with answers and explanations (tap Show answer after you have chosen), the rest in Learn with a free account.

1. Question 1 · Hard

   To license a red cell storage system, FDA requires that at the end of storage:

   1. AHemolysis is below 5%
   2. BAt least 75% of transfused red cells are still circulating 24 hours after transfusion
   3. C2,3-DPG is at least 90% of normal
   4. DAt least 95% of transfused red cells are still circulating 24 hours after transfusion

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   Answer: B · At least 75% of transfused red cells are still circulating 24 hours after transfusion

   A storage system is acceptable only if, at the end of its shelf life, an average of at least 75% of the transfused red cells survive 24 hours after transfusion. Cells that survive the first day then have a near-normal lifespan. FDA also requires hemolysis below 1% at the end of storage. These two limits set the 21-, 35- and 42-day shelf lives.

   • A: The hemolysis limit is below 1%, not 5%.
   • C: 2,3-DPG falls to very low levels during storage and is not a licensing criterion.
   • D: 95% is higher than any current storage system achieves at the end of storage.

2. Question 2 · Medium

   Which patient is most at risk from the raised potassium in older stored red cells?

   1. AA stable adult receiving one unit over 2 hours
   2. BA neonate receiving a large-volume exchange transfusion
   3. CAn adult receiving a platelet transfusion
   4. DAn adult receiving albumin

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   Answer: B · A neonate receiving a large-volume exchange transfusion

   A neonate's small blood volume means a large, fast transfusion delivers a big potassium load relative to body size, which can cause arrhythmias. Fresh red cells, usually 5 to 7 days old or less, or washed red cells are used for exchange and massive transfusion in neonates. Small top-up transfusions of older units are safe for most infants. One unit given slowly to an adult is diluted and causes no problem.

   • A: One slowly given unit is diluted in an adult's large blood volume.
   • C: Platelets are stored at room temperature and do not carry a high potassium load.
   • D: Albumin contains no red cells and no potassium load.

3. Question 3 · Hard

   The pH of a stored platelet unit falls when its oxygen supply is poor. The main cause is:

   1. ACarbon dioxide from bacterial growth
   2. BCitrate from the anticoagulant
   3. CPotassium released from the platelets
   4. DLactic acid from anaerobic glycolysis

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   Answer: D · Lactic acid from anaerobic glycolysis

   When oxygen is short, platelets switch to anaerobic glycolysis and produce lactic acid. Too many platelets in too little plasma, or a bag with poor gas permeability, makes this worse. A low pH makes platelets lose their disc shape and survive poorly after transfusion. Gas-permeable bags and gentle agitation keep oxygen supply adequate.

   • A: Bacteria can lower pH, but the usual cause in an uncontaminated unit is lactate.
   • B: Citrate is present from the start; the fall during storage comes from lactate.
   • C: Potassium leak does not lower pH meaningfully.

4. Question 4 · Medium

   Stored red cells lose 2,3-DPG. What is the effect?

   1. APlasma potassium falls sharply
   2. BOxygen affinity rises (left shift)
   3. COxygen affinity falls (right shift)
   4. DHemoglobin is oxidized to methemoglobin

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   Answer: B · Oxygen affinity rises (left shift)

   2,3-DPG binds deoxyhemoglobin and helps it release oxygen. With less 2,3-DPG the oxygen dissociation curve shifts to the left, so hemoglobin holds on to oxygen. Transfused cells rebuild their 2,3-DPG over the first one to three days in the circulation. Low 2,3-DPG matters most in neonates and in massive transfusion.

   • A: Plasma potassium rises during storage.
   • C: Easier oxygen release is a right shift, which needs more 2,3-DPG, not less.
   • D: Loss of 2,3-DPG does not oxidize hemoglobin.

5. Question 5 · Easy

   During storage at 1 to 6 °C, the plasma potassium in a red cell unit:

   1. AStays the same
   2. BFalls, then rises
   3. CFalls
   4. DRises

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   Answer: D · Rises

   Cold slows the sodium-potassium pump, so potassium leaks out of the red cells into the plasma. Plasma potassium rises steadily over the storage period. For most adults the total amount is small and harmless. It matters in large, rapid transfusions to neonates and in patients with renal failure.

   • A: Plasma potassium changes steadily during storage.
   • B: Potassium rises throughout storage; it does not fall first.
   • C: Potassium does not fall; it leaks out of the cells into the plasma.

6. Question 6 · Hard

   A 3.5-kg infant needs cardiac surgery with cardiopulmonary bypass, and the perfusionist plans to prime the circuit with a whole group O red cell unit. The only unit available is an AS-1 unit on day 38 of storage. Unit data: total volume 320 mL; hematocrit 60%; supernatant potassium 50 mmol/L; supernatant hemoglobin 0.4 g/dL; ATP and 2,3-DPG both well below their day-1 values; pH 6.6. The pathologist asks how much potassium the infant would receive from the fluid outside the red cells. About how much extracellular potassium does this unit contain?

   1. AAbout 9.6 mmol
   2. BAbout 16 mmol
   3. CAbout 64 mmol
   4. DAbout 6.4 mmol

   Answer and explanation in LearnFree account