Changes in the Skin Conductance Monitor as an End Point for Sympathetic Nerve Blocks.
OBJECTIVE
There is a lack of objective methods for determining the achievement of sympathetic block. This study validates the skin conductance monitor (SCM) as an end point indicator of successful sympathetic blockade as compared with traditional monitors.


METHODS
This interventional study included 13 patients undergoing 25 lumbar sympathetic blocks to compare time to indication of successful blockade between the SCM indices and traditional measures, clinically visible hyperemia, clinically visible engorgement of veins, subjective skin temperature difference, unilateral thermometry monitoring, bilateral comparative thermometry monitoring, and change in waveform amplitude in pulse oximetry plethysmography, within a 30-minute observation period. Differences in the SCM indices were studied pre- and postblock to validate the SCM.


RESULTS
SCM showed substantially greater odds of indicating achievement of sympathetic block in the next moment (i.e., hazard rate) compared with all traditional measures (clinically visible hyperemia, clinically visible engorgement of veins, subjective temperature difference, unilateral thermometry monitoring, bilateral comparative thermometry monitoring, and change in waveform amplitude in pulse oximetry plethysmography; P ≤ 0.011). SCM indicated successful block for all (100%) procedures, while the traditional measures failed to indicate successful blocks in 16-84% of procedures. The SCM indices were significantly higher in preblock compared with postblock measurements (P < 0.005).


CONCLUSIONS
This preliminary study suggests that SCM is a more reliable and rapid response indicator of a successful sympathetic blockade when compared with traditional monitors.
Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, New York, USA.
Semih
S
Gungor
Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, New York, USA.
Bhumika
B
Rana
Healthcare Research Institute, Hospital for Special Surgery, New York, New York, USA.
Kara
K
Fields
Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, New York, USA.
James J
JJ
Bae
Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, New York, USA.
Lauren
L
Mount
Department of Anesthesiology, Hospital for Special Surgery, Weill Cornell Medical College, New York, New York, USA.
Valeria
V
Buschiazzo
The Simulation Center, The Acute Clinic, Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
Hanne
H
Storm
D000328:Adult; D000368:Aged; D001340:Autonomic Nerve Block / Q000379:methods; D001831:Body Temperature / Q000502:physiology*; D005260:Female; D005712:Galvanic Skin Response / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012867:Skin / Q000294:innervation*; D012879:Skin Physiological Phenomena; D012881:Skin Temperature / Q000502:physiology*
Complex Regional Pain Syndrome; Monitor; Skin Conductance; Sympathetic Nerve Block