What we need to know on timing principle of nondepolarizing muscle relaxant administration

Corresponding author: Dr Arsen Uvelin, M.D. Clinical centre of Vojvodina, Emergency Centre, Department of Anaesthesia and Intensive Therapy Hajduk Veljka 1, 21000 Novi Sad, Serbia e-mail: [email protected] Sir, the “timing principle” utilises administration of a single bolus dose of nondepolarizing muscle relaxant (NMR), followed by an induction drug at the onset of muscular weakness (1) was used in order to reduce the time for endotracheal intubation. Studied and extensively used in 1980s this method nowadays is somewhat forgotten, although still used. In the era of novel airway manipulation techniques, high dose rocuronium administration and sugammadex, is there still a place for timing principle during NMR administration in order to achieve a fast neuromuscular block? The “timing principle’’ utilises administration of a single bolus dose of nondepolarizing muscle relaxant, followed by an induction drug at the onset of clinical weakness (1-4). Vecuronium, atracurium and rocuronium have all been used in this manner to decrease the effective onset time of NMR (1-4). This means administering muscle relaxant to an awake patient before induction of anaesthesia. What is the safest way to do this? Rocuronium is known to cause pain during injection in 40-80 % of the patients (5). InWhat we need to know on timing principle of nondepolarizing muscle relaxant administration