Imagine supervising a training session on abdominal surgery in mice and suddenly hearing a loud thump at the table behind you. You redirect your attention from the suture line to see that one of your students fell to the floor, having fainted. It's not unheard of.

In fact, it happened to me once. When I was in high school, I got to spend the day behind the scenes at the local veterinary clinic. I had always wanted to work with animals, so I was really excited to be there. The vet invited me to don a head cover and mask and watch while he spayed a dog. I marveled at how he knew what he was doing from such a tiny incision; I was thoroughly engrossed, when I suddenly felt light-headed. My vision narrowed, and it became difficult to breathe. The next thing I remember was sitting outside with two very concerned hospital staff members telling me I was going to be OK. I was so embarrassed—how would I be able to work with animals if I was going to pass out like that? Fortunately, I have never again felt like I was going to lose consciousness while watching a procedure.

However, during two decades of providing training in laboratory animal science, I have had several trainees become light-headed or feel as if they might faint during training. After recently observing a couple of near-fainting incidents, I consulted the Laboratory Animal Welfare and Training Exchange (LAWTE) listserv to find out whether other trainers had experienced similar incidents. The ensuing discussion showed that many trainers are aware of the possibility that trainees may faint. Some routinely take precautions with all students to prevent fainting. Others sought help from the group regarding what to do if a student should become light-headed during training.

I searched the Internet to find out more about light-headedness or fainting in a laboratory setting. Risk factors include standing for long periods of time, the sight of blood, observation of medical procedures, stress, youth, dehydration and hunger. There are several indicators that a person may be likely to faint: pale or 'green' complexion, sweating and feeling too hot or ill. People experiencing these symptoms may be embarrassed (as I was when it happened to me) and therefore may not alert anyone. Trainers should learn to look for and recognize the signs that someone may be at risk of fainting and should know how to respond.

An individual who is feeling light-headed or faint should immediately sit or lie down and remain in that position until he or she feels better. Removing personal protective equipment, when it is safe to do so, can help the person feel more comfortable. Some institutions may have policies governing response to such a situation. For example, an institution may require that the security department or emergency services be called. Trainers should learn and follow their own institutions' policies.

Trainers can also reassure trainees that fainting during training is not an unusual circumstance and educate them about what to do if they feel as if they may faint. I, and others from the LAWTE group, routinely tell trainees in certain situations that there is a possibility that they may feel faint. We advise them that if they do feel ill or light-headed, they should sit down and ask for help. One LAWTE respondent advises trainees to eat a hearty meal and be sure they are well-hydrated before class. Some trainers also offer students the option to remain seated during procedures when possible.

Finally, trainers should keep in mind that even if a student becomes light-headed or faints when observing a procedure, that does not mean that he or she can't do the job. As in my case, it may be a one-time occurrence, resulting from a combination of being young and inexperienced, standing up for a while and observing a medical procedure for the first time.