Epinephrine decreases the dose of hyperbaric bupivacaine necessary for tourniquet pain blockade during spinal anesthesia for total knee replacement arthroplasty.
OBJECTIVE
We quantified the dose-sparing effect of epinephrine by comparing the median effective dose (ED(50)) of intrathecal hyperbaric bupivacaine co-administered with epinephrine with the ED(50) of intrathecal hyperbaric bupivacaine alone.


METHODS
Three groups were randomly generated from 162 patients undergoing total knee replacement arthroplasty under combined spinal and epidural anesthesia: Group B (bupivacaine), Group BE1 (bupivacaine plus epinephrine 100 μg), and Group BE2 (bupivacaine plus epinephrine 200 μg). Each group was further divided by bupivacaine doses of 6, 7, 8, 9, 10, or 11 mg. The anesthesia was defined as successful if a bilateral T12 sensory block occurred within 15 min, and no intraoperative epidural supplement was required. The ED(50) and ED(95) for successful anesthesia and successful tourniquet pain blockade were determined separately by probit regression analysis.


RESULTS
The ED(50) and ED(95) of intrathecal hyperbaric bupivacaine for successful anesthesia were not different among the groups: the ED(50) values were 7.1 mg [95 % confidence interval (95 % CI) 6.0-8.0 mg] in Group B, 6.2 mg (95 % CI 4.8-7.2 mg) in Group BE1, and 6.3 mg (95 % CI 4.9-7.2 mg) in Group BE2. However, the ED(50) and ED(95) values for tourniquet pain control were significantly smaller in Groups BE1 and BE2 than in Group B: the ED(50) values were 7.2 mg (95 % CI 6.3-7.9 mg), 5.5 mg (95 % CI 4.1-6.3 mg), and 5.3 mg (95 % CI 3.7-6.2 mg) in Groups B, BE1, and BE2, respectively. The incidence of tourniquet pain was significantly lower in Groups BE1 and BE2 than in Group B. The time to patients' requests for supplemental analgesia was significantly longer in Groups BE1 and BE2 than in Group B.


CONCLUSIONS
Intrathecal epinephrine did not decrease the dose of intrathecal hyperbaric bupivacaine required for successful anesthesia. However, it reduced the dose required for tourniquet pain blockade.
Department of Anesthesiology and Pain Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, 50, Irwon-dong, Kangnam-gu, Seoul, 135-710, Republic of Korea.
Won Ho
WH
Kim
Justin Sangwook
JS
Ko
Hyun Joo
HJ
Ahn
Soo Joo
SJ
Choi
Byung Seop
BS
Shin
Mi Sook
MS
Gwak
Woo Seog
WS
Sim
Mikyung
M
Yang
D000368:Aged; D000767:Anesthesia, Epidural; D000775:Anesthesia, Spinal / Q000379:methods*; D000779:Anesthetics, Local / Q000008:administration & dosage*; D019645:Arthroplasty, Replacement, Knee / Q000379:methods*; D001794:Blood Pressure / Q000187:drug effects; D002045:Bupivacaine / Q000008:administration & dosage*; D023381:Endpoint Determination; D004837:Epinephrine / Q000494:pharmacology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010146:Pain / Q000517:prevention & control*; D010147:Pain Measurement; D018401:Sample Size; D014111:Tourniquets / Q000009:adverse effects*; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D000779:Anesthetics, Local; D014662:Vasoconstrictor Agents; D002045:Bupivacaine; D004837:Epinephrine