[Histonet] Freezing Sprays in Cryostats

[Shirley A. Powell]

I agree with not using a spray in cryostats.  We had to get tested a few times in the hospital for TB after discovering the case was positive after the fact, scary.  This is the same as flushing the toilet with the seat open.  I know that sounds crazy but here is just one article of many online that explains the aerosol effect.  
https://www.realtor.com/advice/home-improvement/flushing-the-toilet-with-the-lid-up-what-happens/ 

Please don't send me criticism for posting this, it is real. Read the articles. It is a good reason to stop using sprays in the cryostat.  


Shirley Powell, HTL (ASCP)
Technical Director Histology Curricular Support Lab
Pathology
Mercer University School of Medicine
1550 College Street | Macon, GA | 31207
O:478-301-2374| F:478-301-5489
medicine.mercer.edu.







-----Original Message-----
From: Bob Richmond via Histonet [mailto:histonet at lists.utsouthwestern.edu] 
Sent: Thursday, September 26, 2019 12:05 PM
To: Histonet at lists.utsouthwestern.edu
Subject: Re: [Histonet] Freezing Sprays in Cryostats

Freezing sprays for frozen sections in cryostats are deplorable, but try and get pathologists to give them up. I think that's probably why the CAP has been reluctant to ban them.

During my career in pathology I saw more than one case where frozen sections were inadvertently cut on tuberculous tissue. Tuberculosis is a disease that sneaks up on you. In Baltimore (a hotbed of the disease) around 1970 when we did this, we'd put the cryostat (one of the basic Damon IEC models we had then) out of action until somebody (usually the chief
resident) could bring it up to room temperature, scrub it out with alcohol, lubricate it, and plug it back in to cool down.

The heat extractors are usually all you need. Liquid nitrogen is not a very satisfactory freezing medium. It's better to submerge a freezing medium liquid into liquid nitrogen (which will eventually freeze it solid, however). Shandon used to market a freezing container called a Histobath - is any equivalent product available today? It held the right temperature not to freeze the liquid medium solid.

People usually use acetone or isopentane (2-methylbutane) as the freezing medium, both highly flammable. Better is:
3M™ Novec™ Engineered Fluid HFE-7100
This product belongs to a class of fluorocarbons called "segregated hydrofluoroethers (HFE's)"
According to various MSDS, HFE-7100 is
methyl nonafluoroisobutyl ether
C4F9-O-CH3

But try to substitute any such thing for freezing spray, and be prepared for a hissy-fit from your senior pathologist.

I'm glad the CDC weighed in on this. I do remind them that the decision to do a frozen section is between the surgeon and the pathologist.

Bob Richmond
Samurai Pathologist
Maryville TN
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