Thoracic epidural analgesia with low concentration of bupivacaine induces thoracic and lumbar sympathetic block: a randomized, double-blind clinical trial.
BACKGROUND
Clinical benefits of thoracic epidural anesthesia (TEA) are partly ascribed to thoracic sympathetic block. However, data regarding sympathetic activity during TEA are scarce and contradictory. This prospective, randomized, double-blind study evaluated the segmental propagation of sympathetic block after low-concentration, high-volume TEA using digital thermography.


METHODS
Twenty-four patients were included in the study. Thoracic epidural catheters were placed at a median insertion level of T8-T9. Patients were accommodated for 20 min to the room temperature of 23 degrees +/- 0.3 degrees C. Skin temperature was recorded by digital thermography. After baseline measurement of heart rate, arterial pressure, and core body and skin temperature, 10 ml saline (control group) or 10 ml bupivacaine, 0.25% (TEA group), respectively, was administered epidurally. Five minutes (t5) and 20 min (t20) after baseline measurements, hemodynamic parameters and core body temperature were again measured, and sensory block was identified by loss of cold-warm discrimination. In the thumb, the toe, and each thoracic dermatome, difference from baseline temperature was calculated at t5 and t20. Data were analyzed by Mann-Whitney U test.


RESULTS
Baseline characteristics did not differ among groups. Median spread of sensory block at t20 was T5-L5. At both t5 and t20, skin temperature decreased more in the control group than in the TEA group in all thoracic dermatomes (P < 0.05). Toe temperature increased in the TEA group compared with the control group (P < 0.05), whereas thumb temperature remained unchanged.


CONCLUSIONS
TEA with 10 ml bupivacaine, 0.25%, induced thoracic and lumbar sympathetic block that precedes and exceeds sensory block. Caudal limit of sympathetic block could not be demonstrated in this study.
Freise
Hendrik
H
Department of Anesthesiology and Intensive Care Medicine, University Hospital Muenster, Albert Schweitzer Strasse33, 48149 Muenster, Germany. freiseh@uni-muenster.de
Meissner
Andreas
A
Lauer
Stefan
S
Ellger
Björn
B
Radke
Robert
R
Bruewer
Mathias
M
Brodner
Gerd
G
Van Aken
Hugo K
HK
Sielenkämper
Andreas W
AW
Fischer
Lars G
LG
D000328:Adult; D000368:Aged; D015360:Analgesia, Epidural; D001340:Autonomic Nerve Block / Q000379:methods*; D002045:Bupivacaine / Q000008:administration & dosage*; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008161:Lumbosacral Region / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012881:Skin Temperature / Q000187:drug effects / Q000502:physiology; D013909:Thorax / Q000187:drug effects* / Q000502:physiology
D002045:Bupivacaine