If you have serious fade with tetany, it may be best to leave the tube in. In the afore mentioned case, I would probably max out my Neostigmine dose, which I consider to be 0.6 mg/kg, and then apply a little tincture of time.
As we all know, we are usually giving reversals at the end of a case and I often think in this age of "fast on-fast off" anesthetics, that we probably aren't seeing peak effect of reversals, at least according to textbook onset times, by the time we are thinking about pulling the tube. I do agree with others, if they look weak, they are weak.
In the afore mentioned case however, you are also in a bit of a quandary, since what you are seeing clinically, is not jiving with what you are seeing with your twitcher. ie. Classically, a five second head lift was considered a clinical sign of adequate reversal, the patient has adequate VTs, etc.
I would not resedate unless I planned on keeping the patient intubated for a long period of time, ie. unknown pseudocholinesterase deficiency. A good explanation of why the OETT remains in place and adequate pain relief with narcotics, with perhaps a wee bit of versed in those anxious patients is all that is needed until you are confident to extubate.