Contact your doctor - s/he must tell you what the clamps are made of.
The clamps, if metal, are likely made of surgical stainless steel. They certainly do not contain mercury, but they almost certainly contain nickel and chromium - nearly all surgical stainless steel does.
They could be titanium, which is pure or nearly pure titanium, although some people can have allergic reactions to even titanium (any material implanted can cause reactions in certain people).
I went through this concern about stainless steel thread used for an operation. I was concerned about the nickel and chromium content, even though I do not think I am allergic to them.
There is a conflict about what doctors tell you about nickel and chromium in stainless steel. At least 10% of people are allergic to nickel (women are much more likely than men because a lot of them have developed nickel allergies from wearing nickel content jewelry). They make "nickel free" surgical stainless steel for people allergic to nickel. Yet, they will tell you that the nickel and chromium is "locked" into the metal and doesn't escape (sounds like the mercury Amalgam issue huh?). If this is true, that the nickel doesn't escape, why do they bother making "nickel-free" stainless steel for people allergic to it?
I have a lot of info that I can post if you find out exactly what metal was used.