Oh, the thrilling world of biological sex differences in peripheral regional anaesthesia—because when you’re getting your nerves numbed, the first thing on your mind is definitely whether your chromosomes are influencing the experience. So, these intrepid researchers set out with a grand plan to recruit 90 volunteers, because they were absolutely certain they’d find a whopping 35-minute difference in how long the numbness would last between the sexes. But then, the ethical review board stepped in and said, “Let’s pump the brakes and start with just 24 people, okay?”

In this corner, we have 12 women, and in the other corner, 12 men, all getting their ulnar nerves shot with ropivacaine. The main event? Measuring how long it takes for them to feel a pinprick. And the results? Drumroll, please… 450 minutes of numbness for the ladies and 480 minutes for the gents. But wait, the p-value of 0.49 tells us that’s basically the statistical equivalent of a shrug.

Secondary outcomes? Onset time of the block and whether you could actually see the nerves on ultrasound—spoiler alert: no gender VIP passes there either. But, oh, there was a glimmer of difference in the pharmacokinetics, with women having a higher total drug exposure over time. Cue the collective gasp.

After crunching the numbers, the researchers realized they’d need to kidnap—er, I mean, recruit—more than 400 people to find a significant difference in numbness duration. So, they did the only sensible thing: they called it quits.

In the end, they found that whether you’re a Jack or a Jill, it doesn’t really matter when it comes to how long you’ll stay numb after an ulnar nerve block. But if you’re into the nitty-gritty of drug exposure, ladies, you might just have the men beat. And that, my friends, is the tale of how biological sex was found to be a bit of a non-starter in the world of peripheral nerve blocks. Who knew?