“Decreased circulation causes nerve damage”

This is an interesting one. I’ve had people insist to me that someone with nerve damage following a bondage scene does not have nerve damage due to focal compression caused by the rope, but rather has “mild damage to the nerves of the entire limb” caused by “loss of blood flow to the limb.” The suggested fix for this was to reperfuse the limb more frequently (taking weight off a futomono, for example) – which MAY work to prevent nerve damage by moving the ropes and altering the sites of focal compression. However, reperfusion to the limb preventing nerve damage (or loss of circulation, in isolation, causing nerve damage) is NOT A THING.

IMG_5606It’s very clear that muscle is more vulnerable to ischemia than nerves. Lack of blood flow to a limb in isolation will generally not cause nerve damage. For example, surgical guidelines consider application of a tourniquet to a lower extremity for 2 hours, or upper extremity for 1.5 hours, to be safe (there is always a risk of complications of course but it is relatively low) – after that time a deflation of at least 10 minutes is recommended.1

Interestingly, animal studies (ethically – not into it. But the data is relevant) show that there is damage to nerves where they are directly compressed by a tourniquet (as shown in nerve conduction studies) but interestingly no abnormalities in the conduction velocity of the same nerves distal to the injury2 (which is to say, if the tourniquet was around the thigh, there was no damage to nerve segments running in the lower leg). This tells us the damage was caused by the mechanical compression, as nerve segments that suffered the lack of blood flow without the direct compression were apparently unaffected. In practice, I think the more important thing is that decreased circulation and the symptoms thereof complicate detection of focal nerve damage/compression, and would make bottoms more vulnerable in that way, even if not strictly physiologically increasing vulnerability.

 

References:

[1] Tourniquets in orthopedic surgery. http://www.ncbi.nlm.nih.gov/pubmed/22912509

[2] Intermittent reperfusion fails to prevent posttourniquet neurapraxia. http://www.ncbi.nlm.nih.gov/pubmed/10447158