Laboratory Equipment 105 Procedure 6-2: Operating the Centrifuge

TASK

Use a benchtop centrifuge to successfully separate plasma from cells in a blood specimen.

CAAHEP/ABHES STANDARDS None

1. Wash hands and gather necessary supplies. Apply

gloves.

2. Verify that the centrifuge is plugged into an elec-

trical outlet. Open the lid and verify that all the slots in the centrifuge are empty.

3. Pick up the blood specimen and hold the tube at

eye level. Fill the balance tube with water until the two tubes have an equal volume of fluid.

4. Verify that the original rubber cap is on the blood

tube securely. The balance tube should also be capped with the original rubber cap.

5. For some centrifuge models, it may be necessary

to place a rubber spacer or adapter in the cen- trifuge slot to accommodate the size of tube spun. Consult the manufacturer’s recommendations.

6. Place the two tubes in slots within the centrifuge

that are across from each other. The centrifuge can be operated if the other slots are empty, as long as the two tubes are across from each other.

7. Close the lid securely. Turn on the timer on the

centrifuge to the appropriate time for spinning a blood specimen. This will be indicated on the front of the centrifuge or in the manufacturer’s insert.

CONDITIONS

• Gloves

• Benchtop centrifuge

• Blood specimen in tube

• Balance tube

• Spacers to go inside slots in centrifuge if necessary

• Water and transfer pipette

• Test tube rack

• Disinfectant wipe

Hands should be washed before and after performing any procedures in the laboratory, and gloves must be worn whenever handling blood specimens.

Occasionally the previous user will have left a tube or a spacer in one of the slots within the centrifuge, which can cause it to become unbalanced while processing the specimen. Care should also be taken to verify that there is no liquid in the bottom of the receptacles in the centrifuge, as this could also cause the centrifuge to become unbalanced.

The tubes must have the same fluid volume for the centrifuge to be balanced. This can also be accom- plished with two tubes of blood that are the same and are filled to the same level.

To avoid aerosol formation, all specimens processed in the centrifuge should be securely capped.

The spacer or adapter will allow the blood tube to remain high enough in the centrifuge to be removed after spinning, and it may also allow for a tighter fit within the slot to avoid the breakage from vibration that is possible when the tube does not fit securely. Balance is essential to keep the centrifuge from vibrat-

ing excessively while operating. An unbalanced cen- trifuge can cause the tubes to break, and it also can cause the centrifuge to fall off the countertop due to the excessive motion.

Larger tubes may require a higher rate of centrifugation or a longer time in the centrifuge to achieve the desired separation of cells and plasma.

Procedure Rationale

Procedure Rationale

8. Monitor the centrifuge for at least 20 to 30 seconds

after it has been turned on to see if the instrument is vibrating excessively. If so, turn off or unplug the centrifuge immediately.

9. Do not attempt to open the centrifuge until it has

come to a full stop.

10. When the centrifuge has come to a complete stop,

open the lid and carefully remove the tube of blood. Place the blood in a rack for further processing.

11. Remove the balance tube and the spacers and

adapters if used. The balance tube may be discarded or reused for another specimen. The spacers and adapters are to be stored for use with the next centrifuge load.

12. Use a disinfectant wipe to wipe down the exterior

and interior of the unit.

13. Remove gloves and wash hands.

An unbalanced centrifuge can be dangerous if it vibrates on the countertop and moves from its original position.

Opening the centrifuge prematurely or placing a hand into the unit while it is still spinning can be very dangerous.

Care needs to be taken when removing the tube of blood so that the plasma and cells do not become mixed.

Some laboratories keep a set of balance tubes close at hand to be used for additional centrifugation. Be sure that the tube cap is securely fastened if using the balance tube again.

If excessive contamination is evident, it may be neces- sary to clean the unit to a greater extent. In many units, the slots in which the tubes are placed are removable so that they can be washed if necessary. Hands should be washed before and after performing

any procedures in the laboratory.

Procedure 6-2: Operating the Centrifuge—cont’d

POINT OF INTEREST6-1

“Sally Centrifuge”

In many areas of the world health-care providers do not have access to electricity or funds for purchasing traditional instruments used for diagnosis. The pres- ence of anemia contributes significantly to the diag- nosis and subsequent treatment of disorders such as malnutrition, HIV/AIDS, tuberculosis, and malaria. Blood specimens collected from the patients in these areas must be shipped to larger health-care facilities for testing, which is expensive and time consuming. In 2010, two Rice University college students cre- ated an inexpensive centrifuge that allows the cells to be separated from the plasma in microhematocrit tubes in 10 to 20 minutes without the use of electric- ity. Lauren Theis and Lila Kerr created the centrifuge as a class project, using materials that included combs, yogurt containers, and a salad spinner. The centrifuge

cost approximately $30 to build, and it can process 30 samples of 15 microliters each at one time. The cen- trifuge must be pumped by hand for 10 to 20 minutes, at which point it reaches speeds of approximately 950 rotations per minute and successfully separates the blood cells from the plasma in the tubes. The tubes then can be compared to a reference chart to obtain the hematocrit result, used to diagnosis the presence of anemia.

These students are part of a Rice University pro- gram, Beyond Traditional Borders. As part of this program, the students used the centrifuges in several remote locations during the summer of 2010 to test their ability to withstand traditional use in a health- care setting. If successful, “Sally Centrifuge” could have a profound impact on the ability to deliver affordable, timely health care in many locations across the globe.