EVALUATION OF INTUBATING CONDITIONS WITH ROCURONIUM 0.6 mg/Kg USING TRAIN OF FOUR STIMULATION IN ELECTIVE SURGERY

Neuromuscularblockers (NMBs) are widely used in anaesthesia practice during endotrachealintubation. The degree of neuromuscular block is usually evaluated by clinicalcriteria. But the recommendation for application of neuromuscular monitoring topatients receiving NMBs is based on two important issues: first, on thevariable individual response to muscle relaxants and second because of thenarrow therapeutic window. Adequate muscle relaxation  for intubation corresponds to a narrow rangeof 90 to 95% receptor occupancy.1 Inadequate muscle relaxationduring intubation can lead to difficulty in securing the airway or multipleattempts leading to laryngeal morbidity like postoperative hoarseness (4-42%)and vocal cord injury.2

Rocuroniumis one of the most commonly used non depolarising muscle relaxant forintubation of the trachea. It has been postulated that laryngeal muscles beingresistant to the effects of neuromuscular blocking agents,3 requireat least twice the ED95 dose.4

Asit is difficult to quantify the relaxation of the laryngeal muscles, thereforesurrogates such as Adductor pollicis longus (APL), orbicularis oculi (OO),corrugator supercilii (CS)5 and even flexor hallucis brevis (FHB)6have been utilised, though APL is the preferred site. Neuromuscular transmissioncan be monitored by various methods like single twitch (ST), double burststimulation (DBS) and train of four (TOF). Although good clinical researchpractice (GCRP) states that either ST or TOF can be used as a guide forintubation, TOF is preferable because it is more sensitive to lesser degree ofreceptor occupancy than single twitch.1 Observation of evoked TOFresponses after a dose of non depolarising muscle relaxant allows prediction of onset time of paralysis oflaryngeal muscles  in individualpatients.

Inthe absence of availability of NMT monitors, timed intubation has beenpracticed. However, patient factors1 such as age, gender,7medical condition (ASA physical status), body weight affect thepharmacokinetics and pharmacodynamics of the drug.

Onreviewing the literature, we found that although, clinically acceptableconditions have been obtained with rocuronium 0.6mg/kg in 90 seconds, therehave not been many studies to quantify the proportion of patients havingexcellent conditions and time required thereof for a standard observableendpoint i.e, disappearance of either three (T1) or all twitches (T0) after aTOF stimulus. The literature does not indicate which endpoint provides the bestintubating conditions.

Thereforethere is a need to ascertain the percentage of healthy routine patientsachieving excellent intubating conditions and the time taken to achieve thesewith rocuronium 0.6mg/Kg using defined monitor i.e, TOF stimulation and associatedpost operative sore throat if any.