Manual evaluation of residual curarization using double burst stimulation: a comparison with train-of-four

Double burst stimulation (DBS) is a new mode of stimulation developed to reveal residual neuromuscular blockade under clinical conditions. The stimulus consists of two short bursts of 50 Hz tetanic stimulation, separated by 750 ms, and the response to the stimulation is two short muscle contractions. Fade in the response results from neuromuscular blockade as with train-of-four stimulation (TOF). The authors compared the sensitivity of DBS and TOF in the detection of residual neuromuscular blockade during clinical anaesthesia. Fifty-two healthy patients undergoing surgery were studied. For both stimulation patterns the frequencies of manually detectable fade in the response to stimulation were determined and compared at various electromechanically measured TOF ratios. A total of 369 fade evaluations for DBS and TOF were performed. Fade frequencies were statistically significantly higher with DBS than with TOF, regardless of the TOF ratio level. Absence of fade with TOF implied a 48% chance of considerable residual relaxation as compared with 9% when fade was absent with DBS. The results demonstrate that DBS is more sensitive than TOF in the manual detection of residual neuromuscular blockade.