It's been nearly two years since AORN published its "Recommended practices for the care and handling of specimens in the perioperative environment." While these detailed recommendations have led to improved specimen handling, questions remain that could affect the integrity of your patient's specimens and efficiency of your facility.
Q. Should we put all specimens in fixative?
A. No, not all. In some instances, evaluation of specimens requires fresh tissue. These include:
- intraoperative consultation by gross or frozen section examination (including renal biopsies);
- tissue culture (wounds, debridements, sinus contents, lymph nodes and others);
- skin and kidney biopsies evaluated with immunofluorescence;
- lymph nodes and other tissue being evaluated for lymphoma; and
- any tissue that must undergo chromosomal, cytogenetic or gene rearrangement studies.
If none of the above applies and you don't need immediate fresh tissue study, quickly place the tissue in the sufficient volume of the appropriate fixative. This must be done quickly because once the tissue is separated from the blood supply during surgery, it begins to deteriorate. To provide an accurate and complete diagnosis on each piece of tissue, it's best to provide tissue to the pathologist in as close to the living state as possible.
Nearly all fixative solutions are dilute formalin solutions mixed with water and other chemicals. Formalin fixes tissue at the rate of 1mm of tissue per hour. Fixation occurs by diffusion and this requires direct contact of the solution with the tissue. For adequate fixation, the ratio of formalin volume to specimen volume must be between 3:1 and 10:1 (depending on what makes up the tissue). Various pathology lab guidelines and the AORN Recommendations simply tell you to "cover the tissue with fixative." But covering the tissue with fixative provides at best a 1:1 ratio of fixative to specimen. Incomplete fixation of tissue can lead to increased turnaround time (longer time to fix and reprocess specimens) and can even cause diagnostic error. Take-home message: Use more fixative.
Q. What about the type of fixative we use?
A. The type of fixative used does makes a difference. Fixative solutions are formulated to provide ideal fixation and appearance of the tissue under the microscope for the pathologist. The fixative solution also impacts how the tissue reacts with some of the esoteric testing that is done on specimens (immunohistochemistry and fluorescent in situ hybridization, for example). Special formulations have been devised to more quickly fix fatty tissues and to make lymph nodes easier to visualize.
Q. What's the appropriate container for the specimens we generate in our facility?
A. The proper amount of fixative is 3 to 10 times the volume of the specimen and specimen containers should be only 75 percent full to avoid leakage and spilling. In your specimen supply area, create photographic inventory cards that have an image of the container filled to 75 percent with colored fluid (water and food coloring work great), with a list of the types of specimens that are appropriate for this container.
Q. How to ensure the best fixation?
A. At the beginning of every procedure, verbally confirm whether there will be a need for tissue culture, frozen section or gene studies. This tells you whether to keep the tissue fresh or fix it quickly.
To remove gastrointestinal biopsies and colon polyps from the forceps, flush the forceps with formalin solution from the biopsy bottle (disposable squeeze pipettes are easier to use than syringes and less expensive) rather than with saline which will dilute the fixative solution.
Take specimens out of the operating field specimen cups before placing them in their transport containers. Otherwise, the specimen will only be in contact with the volume of fixative in the cup.
If the tissue is soft and fragments easily (such as a liver biopsy or an endometrial biopsy), avoid using gauze or mesh. These tissues get stuck in the gauze and mesh, and may never be able to be evaluated.
For specimens with a hollow viscous (such as segments of bowel or gallbladders), your pathologists can show you how to safely "open" the specimen to allow fixative in or use a syringe and needle to infuse fixative into the closed specimen.