Time Window For Tracheal Intubation Afer Administration Of Rocuronium Or Succinylcholine

Backgroud and Study ObjectivePrevious studies have concentrated on the preparation, dosage or injection methods of anesthetics in order to obtain the earlier and quicker time point for tracheal intubation, and to attenuate the profound sympathetic responses such as hypertension and tachycardia during intubation by the prior administration of additional hypnotics, volatile anesthetics, opioids, orβ-adrenergic blockers. And often had neglected the best opportunity for intubation (the best intubating condition, the least physical stress reaction) and the optimal time window for intubation. On the basis of pharmacy, the optimal time for intubation must be a period after drug's onset time, not a single moment. In purpose of finding the optimal time for intubation, the author investigated the intubation conditions at 1,2,3,4 min after the administration of rocuronium (0.9 mg·kg^-1)or succinylcholine(1.0 mg·kg^-1), during induction given by target-controlled infusions with propofol and sulfentanil.Patients and MethodsFollowing approval by the Hospital Ethics Committee and written informed consent, 240 patients aged 18-55 years, ASA gradesâ… -â…¡, who were given elective surgery under general anaesthesia, were randomized into two groups to receive rocuronium (n=120) or succinylcholine (n=120). And then the 120 patients in each group were randomized into four groups according to the intubation time of 1min,2min,3min,4min after the administration of neuromuscular blocking drugs. Patients with increased risk of pulmonary aspiration of gastric content, and a potentially difficult airway, and patients who deviated by more than 30% from their ideal weight were excluded. None of the patients was taking drugs known to interact with neuromuscular blocking agents, or had evidence of renal, hepatic, metabolic, or neuromuscular disease.General anaesthesia was induced by target controlled infusion with propofol(target concentration 3.5μg·ml^-1)and sulfentanil (target concentration 0.3ng·ml^-1). A senior anesthesiologist 'blinded' for randomization, performed the intubations 1min, 2min, 3min, 4min after injection of relaxant. Intubation conditions were evaluated according to Cooper's score. And we chose the Cormack-Lehane (C/L) score method for the grade of the vocal cards visibility.The electrocadiography, heart rate(HR), noninvasive artrial blood pressure(MAP), pulse oximatry were monitored throughout the study period. The volumes of HR and MAP were recorded at the time before induction(T₁), one minutes after induction(T₂), one minute before intubation(T₃), the time when intubation(T₄), one minute after intubation(T₅). The values of train of four stimulation at the time of intubating were recorded. Neuromuscular monitoring was started after successful automatic calibration of an acceleromyographic monitor (TOF-watch SX; Organon, Dublin, Ireland), attached to the adductor pollicis muscle and using ulnar nerve stimulation with a train-of-four for every 15s. The skin of the arm and wrist was cleaned with alcohol and application of a conductive jelly to the surface electrodes to facilitate optimal monitoring. ResultsThe degree of neuromuscular block of the aductor pollicis measured at the time of intubation in group R_1min, S_4min were differed significantly from that in other groups.The intubation conditions according Copper's score There were no siginificant difference (P＞0.05) in acceptable intubating conditions between group R_1min, R_2min, R_3min, R_4min and S_1min, S_2min, S_3min. But the acceptable intubating conditions in group S_4imn differed significantly from other groups (P＜0.001).The vocal cards conditions There were no statistically significant differences with the vocal cards conditions in groups R_2min, R_3min and R_4min, but the vocal cards conditions ( Cormack--Lehane score ) in groups R_2min, R_3min and R_4min were differed significantly from that in groups R_1min and S_1min. There were no statistically significant differences with the vocal cards conditions in groups S_1min, S_2min and S_3min, but the vocal cards conditions (Cormack--Lehane score) in group S_4min were differed significantly from that in group S_1min. The rate of moving vocal cards in group S_4min was higher than that in other groups.Haemodynaic variables There were no significant differences in haemodynaic variables among the groups prior to induction. Mean arterial pressure(MAP) decreased in all groups after induction of anaesthesia. In the succinylcholine group, 13 patients required atropine 500μg when the heart rate decreased below 45 beat·min^-1.ConclusionsIntubating conditions were similar between 1～4min after the administration of rocuronium (0.9 mg·kg^-1) and 1～3min after the administration of succinylcholine (1.0 mg·kg^-1). From 2min to 4 min afer administration of rocuronium (0.9mg·kg^-1) was the ideal time window for intubation during TCI propofol and sulfentanil, and that was at 1～3min with succinylcholine (1.0 mg·kg^-1). This may conduct us to operate intubation in a leisurely manner and achieve the operation at the first time, and with that we can avoid injuries due to explore the glottis many times.