One reason for the brisk slap of the instrument is to overcome what I call the trampoline effect. The surgeon has his hand extended in the open position when receiving an instrument. This action stretches his glove between the extended thumb and extended index finger creating an elastic mini- trampoline smack dab in the middle of his hand. If the instrument is not delivered in a firm manner it will bounce right out of the surgeon's hand and he might offer some unpleasant editorial comment.
Dr. Oddo, our international neurosurgeon, always had novice scrub nurses wear glasses with loupe magnifiers just to see what they were like. All I could say is kudos to anyone with the patience to work with these things on their eyes. Your peripheral vision is blocked out and you cannot really see much of anything except that which directly in front of you. Anytime a scrub nurse works with a surgeon wearing loupes you know he is working by feel when receiving an instrument. It takes a slap and then a little push into the hand for the surgeon to easily grasp it. Don't be timid. The surgeon's vision for anything outside the operative field is nil.
Mentioning loupe magnifiers brings to mind a bit of foolishness unrelated to slapping instruments. Dr. Oddo used to tell his residents to wear loupe magnifier eyeglasses on all their cases just to get used to wearing them. When one of these eager beaver residents showed up in Dr. Slambow's general surgery room wearing loupe magnifiers he would bellow, "We're not operating on an ant's ass in here. Take those damn things off." General surgery cases did not really need the up close magnification and Dr. Slambow was not one to be trifled with.
When the tempo of a case picks up or something unexpected happens the instrument slapping can become a little more aggressive. I think it is a subconscious thing that goes along with the hyper vigilance when you have to move really fast and not think too much about what you are doing. It's a conditioned response. I have never had a surgeon complain about me slapping an instrument too hard into his hand.
About the worst thing you can do when instrument trafficking ( a slick term I learned from you bright young whippersnapperrns) is to "dangle" an instrument over the field. It's a novice mistake everyone makes. The surgeon has no idea where a dangled instrument is in space so it's of no use to anyone. To a novice, a dangled instrument does feel like a security blanket- you at least have an instrument at hand. It's really just in the way and you might miss handing off something that is needed in a hurry.
Some old school scrub nurses (to me), so it's second generation old school to you whippersnappers engaged in what I call malicious instrument slapping. If a resident was caught napping or was slow to respond they would take a sponge ring forceps and whack the knuckles with the handle end of this instrument. A sponge stick is one of the more lengthy instruments and with the leverage, capable of delivering a painful blow. Come to think of it a sponge stick is about the same length as a ruler. I wonder if this is the operating room sister equivalent to the parochial school knuckle slapping nuns. I never thought of this angle before, but it seems to make sense. Do not attempt knuckle slapping with an attending surgeon, it would be a big mistake. I never had the guts to pull this trick on anyone, but based on anecdotal accounts, it was a favorite trick of old time scrub nurses.
Old scrub nurse mentors have told me, "Now that stunt deserves a good crack on the knuckles. Always have a sponge ring forceps ready to go on the residents side of your Mayo Stand." I never did this and I never talked back to any surgeon. These same old scrub nurses used to counsel me, " Don't let that surgeon scream at you like that when it's not your fault. It's bad for your soul." Maybe I should have heeded their advice.
When an instrument is passed correctly it's not really a hard smack. It's like a brisk flick into the hand followed by a very brief firm push. The surgeon then reflexively grasps it and is ready to go. It probably looks like a smack and might even sound like a smack, but I'm not sure that thinking of it as a pure smack is the best way to conceptualize it. You know a proper instrument smack when you feel it!
I suspect that with modern laparoscopic and minimally invasive procedures instrument slapping is becoming a lost art. How in the world do you slap a laparoscope?