Interaction Between Magnesium and Neostigmine or Sugammadex for the Reversal of a Rocuronium-induced Neuromuscular Block

Magnesium sulphate is regularly used in perioperative medicine. During and after general anesthesia, it enhances the effect of muscle relaxants because it reduces the liberation of acetylcholine at the neuromuscular junction. When administered immediately after spontaneous recovery of a neuromuscular block (NMB), magnesium may cause a recurrence of NMB and compromise patient safety. Rocuronium is a neuromuscular blocking agent which is frequently used to facilitate intubating and surgical conditions. At the end of the procedure, there are two ways to accelerate the reversal of a neuromuscular block induced by rocuronium: 1. Administration of neostigmine, an anticholinesterase agent and competitive antagonist; 2. Administration of sugammadex, a γ-cyclodextrin compound and specific encapsulator of rocuronium. The study is done in patients receiving rocuronium and either neostigmine or sugammadex for reversal of NMB. It is hypothesized that when sugammadex is used as an antagonist of a rocuronium-induced NMB, it prevents the reappearance of NMB when magnesium is injected, because sugammadex should inactivate all remaining rocuronium molecules and restore neuromuscular reserve of the neuromuscular junctions. Further more it is hypothesized that reversal with neostigmine will not prevent a magnesium-induced recurrence of NMB to the same extent. The primary objective of the study is to show that after reversal with sugammadex there is no or only very little re-occurrence of neuromuscular block after a magnesium perfusion. Furthermore we want to show that after reversal with neostigmine there is a re-occurrence of neuromuscular block.