No change in impedance upon intravascular injection of D5W

Abstract

Purpose Electrical impedance increases following test injections of non-conducting solutions around nerves; however, this increase should diminish rapidly with intravascular needle placement, wherein the systemic circulation will dissipate the solution. For this observational study, we hypothesized that the impedance increases significantly at the perineural space after an injection of 5% dextrose in water (D5W), but that it does not increase correspondingly at the intravascular location Methods After Ethics Research Board approval, electrical impedance was measured by a nerve stimulator displaying resistance, StimuplexÒ HNS 12, before and during (30 sec) an injection of D5W 3 mL: 1) during intravenous cannula placement using an insulated stimulating needle sheathed in its plastic cannula, MultiSet NanoLine with 18G needle; and 2) during needle placement (Pajunk 22G insulated) for an ultrasound-guided supraclavicular block in patients undergoing hand surgery. The impedance changes at each location were analyzed and compared. Results Data were collected from 16 patients. Baseline impedance was lower intravascularly (mean 16.5 ± standard deviation 7.2 kX) compared with perineurally (23.5 ± 8.3 kX) (P = 0.037). Peak impedance after intravascular D5W injection was 20.1 ± 6.8 kX, which was not a significant change (P = 0.15). In contrast, peak impedance after perineural D5W injection was 58.6 ± 29.1 kX, an increase of 35.1 ± 26.4 kX (155 ± 117%), and then it reached a plateau of 36.7 ± 19.6 kX. The increase in impedance was significantly greater at the perineural location (P \ 0.0001). Conclusion The absence of a significant increase in impedance upon injection of D5W prior to injection of local anesthetic may provide useful information to warn of intravascular injection. RésuméObjectif L'impe´dance e´lectrique augmente apre`s les injections de test de solutions non conductrices autour des nerfs; toutefois, cette augmentation devrait diminuer rapidement lors d'un positionnement intravasculaire de l'aiguille, situation dans laquelle la circulation syste´mique dissipera la solution. Pour re´aliser cette e´tude observationnelle, nous avons e´mis l'hypothe`se que l'impe´dance augmentait de façon significative dans l'espace pe´rineural apre`s une injection de dextrose a`5 % dilue´e dans de l'eau (D5W), mais qu'elle n'augmentait pas de la meˆme manie`re dans un site intravasculaire. Méthode Apre`s avoir reçu l'approbation du Comited 'e´thique de la recherche, l'impe´dance e´lectrique a e´teḿ esure´e à l'aide d'un stimulateur nerveux affichant la re´sistance, le StimuplexÒ HNS 12, avant et pendant (30 sec) une injection de 3 mL de D5W: 1) pendant le positionnement d'une canule intraveineuse a`l'aide d'une aiguille de stimulation isole´e prote´ge´e par sa canule de plastique, le MultiSet NanoLine avec une aiguille 18G; et 2) pendant le positionnement de l'aiguille (Pajunk 22G isole´e) pour un bloc supraclaviculaire par e´choguidage chez des patients subissant une chirurgie de la main. Les changements d'impe´dance a`c...

Practice advisory on the bleeding risks for peripheral nerve and interfascial plane blockade: evidence review and expert consensus

“…The panel also recommends that intermediate risk blocks be monitored for hemodynamic changes and any bleeding manifestations following the procedure until deemed necessary. Routine monitoring such as ultrasound assessment of the block site for any fluid collections over time, impedance monitoring, 135 or inclusion of a vascular marker in the local anesthetic mixture may be additional useful aids, but whether they improve the safety profile of block performance is currently unknown.…”