A Randomized Comparison Between Single- and Triple-Injection Subparaneural Popliteal Sciatic Nerve Block.
OBJECTIVE
This prospective randomized trial compared ultrasound-guided single-injection (SI) and triple-injection (TI) subparaneural popliteal sciatic nerve block. We hypothesized that multiple injections are not required when local anesthetic (LA) is deposited under the paraneurium because the latter entraps LA molecules, ensuring circumferential spread around the nerve. Therefore, in addition to comparable success rates, we also expected similar total anesthesia-related times (sum of performance and onset times) and designed this study as an equivalency trial.


METHODS
Ultrasound-guided subparaneural posterior popliteal sciatic nerve block was carried out in 100 patients. In the SI group, LA was deposited at a single location between the tibial and peroneal nerves. In the TI group, LA was injected between the tibial and peroneal divisions, medial to the tibial nerve, and lateral to the common peroneal nerve. The total LA volume (15 mL) and mixture (lidocaine 1%-bupivacaine 0.25%-epinephrine 5 μg/mL) were identical in all subjects. The performance time, number of needle passes, and adverse events (paresthesia, neural edema) were recorded by the (nonblinded) investigator supervising the block. A blinded observer evaluated the success rate (sensorimotor composite score ≥6/8 points at 30 minutes) as well as the onset time and contacted patients 7 days after the surgery to inquire about persistent numbness or motor deficit.


RESULTS
Both techniques provided comparable success rates (92%) and total anesthesia-related times (17.1-19.7 minutes). Expectedly, the SI group required fewer needle passes (1 vs 3; P < 0.001) and a shorter needling time (3.0 ± 2.3 minutes vs 4.0 ± 2.3 minutes; P = 0.025). The TI group displayed a shorter onset time (12.5 ± 7.9 minutes vs 15.8 ± 7.9 minutes; P = 0.027). The performance time, procedural discomfort, and incidence of paresthesia (14%-20%) were similar between the 2 groups. Sonographic neural swelling was detected in 2 subjects in the SI group. In both cases, the needle was carefully withdrawn and the injection was completed uneventfully. Follow-up of the 100 subjects 1 week after surgery revealed no residual numbness or motor deficit.


CONCLUSIONS
Ultrasound-guided SI and TI subparaneural popliteal sciatic nerve blocks result in comparable success rates and total anesthesia-related times. Expectedly, the SI technique requires fewer needle passes.
From the *Maharaj Nakorn Chiang Mai Hospital, Department of Anesthesia, Chiang Mai University, Chiang Mai, Thailand; †Department of Anesthesia, Hospital de Carabineros, Santiago, Chile; and ‡Montreal General Hospital, Department of Anesthesia, McGill University, Montreal, Quebec, Canada.
Worakamol
W
Tiyaprasertkul
Francisca
F
Bernucci
Andrea P
AP
González
Prangmalee
P
Leurcharusmee
Murray S
MS
Yazer
Wallaya
W
Techasuk
Vanlapa
V
Arnuntasupakul
Daniel Chora
DC
de la Garza
Roderick J
RJ
Finlayson
De Q H
DQ
Tran
D000328:Adult; D019162:Anesthetics, Combined / Q000008:administration & dosage* / Q000009:adverse effects; D000779:Anesthetics, Local / Q000008:administration & dosage* / Q000009:adverse effects; D002045:Bupivacaine / Q000008:administration & dosage* / Q000009:adverse effects; D002677:Chile; D004338:Drug Combinations; D004837:Epinephrine / Q000008:administration & dosage; D005260:Female; D006801:Humans; D007267:Injections; D008012:Lidocaine / Q000008:administration & dosage* / Q000009:adverse effects; D008297:Male; D008875:Middle Aged; D009407:Nerve Block / Q000009:adverse effects / Q000379:methods*; D011446:Prospective Studies; D011792:Quebec; D012584:Sciatic Nerve / Q000000981:diagnostic imaging / Q000187:drug effects*; D013785:Thailand; D013997:Time Factors; D018084:Ultrasonography, Interventional
D019162:Anesthetics, Combined; D000779:Anesthetics, Local; D004338:Drug Combinations; D008012:Lidocaine; D002045:Bupivacaine; D004837:Epinephrine