S. Ziege et al., LONG-TERM REGISTRATION OF CUTANEOUS MICROCIRCULATION DURING GENERAL-ANESTHESIA, International journal of microcirculation, clinical and experimental, 17(6), 1997, pp. 385-394
under the provision that the active control of the microcirculatory pe
rfusion is eliminated. Using this approach, we have been able to detec
t a highly stable The temporal dynamics of the systemic arterial press
ure can be monitored noninvasively from the skin of the earlobe or for
ehead by photoplethysmography blood pressure rhythm in the range of 0.
15 Hz during psychophysical relaxation or sleep. The aim of the presen
t study was to investigate the occurrence and behavior of blood pressu
re rhythms below 0.2 Hz during general anesthesia. In 30 patients (ASA
groups I-II) undergoing basic surgical procedures, photoplethysmograp
hic recordings from the earlobe were made during the whole time of ane
sthesia. The recorded signals were divided into segments of 200 s of d
uration, the temporal structure of which was analyzed by fast Fourier
transform. Different characteristic patterns of rhythmical behavior we
re detected: (1) absence of activity below 0.2 Hz ('low-frequency rang
e'); (2) slow sinusoidal rhythmicity below 0.05 Hz; (3) 'chaotic' beha
vior, i.e. multiple incoherent fluctuations without stationary periods
or amplitudes; (4) short-term rhythmical activity at about 0.15 Hz, a
nd (5) long-term rhythmical activity at about 0.15 Hz. In patients suf
ficiently sedated to eliminate low-frequency activity, rhythmicity cou
ld sometimes be triggered by certain surgical stimuli, the response to
which was suppressed by injection of opioids. The data presented stro
ngly suggest that rhythmical perfusion patterns of the cutaneous micro
circulation could serve as an indicator for the depth of anesthesia.