by Swaroop Sood

Open centrifuges

After the arrival of HIV in the early 1980s, we all became aware of the dangers of infection to healthcare workers by body fluids. Laboratory personnel were particularly concerned, since there was a real danger from aerosol-spread infections. Despite that, until about fifteen years ago, open centrifuges continued to be used in laboratories.

The other problem with these centrifuges was that tube breakages were common, for three reasons. One reason was that the centrifuges were badly balanced. The second reason was that the tubes were made of cheap glass of terrible quality, and it broke easily. The third reason was that we were supposed to place small rubber bungs under the tubes for centrifugation. For many laboratories it was difficult to replace these bungs since the purchase procedure was typically long and inefficient (A comprehensive maintenance contract made matters much better, but more about that elsewhere!) Since the laboratory often ran out of these bungs, the technicians resorted to placing wads of cotton below the tubes, and these wads just were not good enough.

It was not uncommon to find, after a centrifuge run, a broken tube or two. Apart from the loss of sample, the technicians were at risk as they cleaned the mess. They did use gloved hands, but the use of glutaraldehyde was uncommon.

Over the years, these open centrifuges were replaced by centrifuges with lids.

Cleaning

Laboratory centrifuges require particular attention. Any spillage of blood should be dealt with immediately, and the bowl, head and buckets (including rubber pads) should be disinfected regularly with a 2% w/v glutaraldehyde solution. Centrifuges should never be cleaned using hypochlorite solution or other metal corrosives. Special care is required when a glass or plastic tube breaks in a centrifuge.

Procedure for decontaminating a centrifuge after breakage of a tube 

1. Switch off the centrifuge motor and do not open the lid for 30 min. Inform the safety officer.
2. When the breakage involves a high-risk specimen, gloves, googles, and a protective apron must be worn, and the bucket must be opened in a safety cabinet.
3. Puncture-resistant gloves must be worn, and forceps (not hands) must be used when removing broken tubes and any solid debris. These, together with buckets, trunnions, and rotor should be placed in 2% w/v glutaraldehyde solution for 24 hours.
4. The centrifuge bowl should be washed with 2% w/v glutaraldehyde solution, left to dry, and washed again.
5. All contaminated disposable material must be placed in appropriate containers for autoclaving.

 

Newer primary sample tubes and the decreased need for centrifugation

In clinical chemistry, the most commonly tested sample is serum. These days the primary sample tubes are so designed that the blood separates effectively into serum and cells, and does not easily remix. Laboratories have achieved remarkable degrees of automation, and the analytical machines can draw serum directly from the primary sample tube. These primary sample tubes sometimes may not need any centrifugation at all. Also, a technician does not need to make aliquots and load the analytical machine sample by sample. I strongly recommend these systems for all major laboratories.