RT Journal Article SR Electronic T1 Opening injection pressure monitoring using an in-line device does not prevent intraneural injection in an isolated nerve model JF Regional Anesthesia & Pain Medicine JO Reg Anesth Pain Med FD BMJ Publishing Group Ltd SP 916 OP 918 DO 10.1136/rapm-2021-102788 VO 46 IS 10 A1 Mejia, Jorge A1 Varela, Victor A1 Domenech, Javier A1 Goffin, Pierre A1 Prats-Galino, Alberto A1 Sala-Blanch, Xavier YR 2021 UL http://rapm.bmj.com/content/46/10/916.abstract AB Background Injection pressure monitoring using in-line devices is affordable and easy to implement into a regional anesthesia practice. However, solid evidence regarding their performance is lacking. We aimed to evaluate if opening injection pressure (OIP), measured with a disposable in-line pressure monitor, can prevent intraneural (subepineural) injection using 15 pound per square inch (PSI) as the reference safety threshold.Methods An isolated nerve model with six tibial and six common peroneal nerves from three unembalmed fresh cadavers was used for this observational study. A mixture of 0.5% ropivacaine with methylene blue was injected intraneurally at a rate of 10 mL/min, to a maximum of 3 mL. OIP was recorded for each injection as well as evidence of intraneural contrast. Injected volume at 15 and 20 PSI was recorded, and when it leaked out the epineurium, if it occurred.Results In all cases, OIP was<15 PSI and intraneural contrast was evident before the safety threshold. The 15–20 PSI mark was attained in 5 of 12 injections (41%), with a median injected volume of 0.9 mL (range 0.4–2.3 mL). Peak pressure of >20 PSI was reached in two injections (at 0.6 mL and 2.7 mL). Contrast leaked out the epineurium in 11 of 12 injections (91%) with a median injected volume of 0.6 mL (range 0.1–1.3 mL).Conclusions Our results suggest that in-line pressure monitoring may not prevent intraneural injection using an injection pressure of 15 PSI as reference threshold. Due to the preliminary nature of our study, further evidence is needed to demonstrate clinical relevance.