Double-Burst Stimulation
DBS consists of two short bursts of 50-Hz tetanic stimulation
separated by 750 msec. The duration of each square wave impulse in the burst is
0.2 msec ( Fig. 39-7
). Although
the number of impulses in each burst can vary, most commonly used is DBS with three
impulses in each of the two tetanic bursts (DBS3,3
).[27]
[28]
[29]
[30]
In nonparalyzed muscle, the response to DBS3,3
is two
short muscle contractions of equal strength. In the partly paralyzed muscle, the
second response is weaker than the first (i.e., the response fades) (see Fig
39-7
). Measured mechanically, the TOF ratio correlates closely with the
DBS3,3
ratio. DBS was developed with the specific aim of allowing manual
(tactile) detection of small amounts of residual blockade under clinical conditions,
[27]
and during recovery and immediately after surgery,
tactile evaluation of the response to DBS3,3
is superior to tactile evaluation
of the response to TOF stimulation.[29]
[31]
[32]
However, as shown in Figure
39-8
, absence of fade in the manually evaluated response to DBS3,3
(and TOF) does not exclude residual neuromuscular blockade.[33]
