Background and Aims Erector Spinae Plane block (ESPB) has at least 3 reports of probable local anesthetic systemic toxicity1–3, and few local anesthetic absorption reports since first published4–5.
Our primary goal is to measure arterial levo-bupivacaine plasma levels following thoracic ESPB, and the effect of epinephrine addition.
Methods This is a randomized controlled study on ASA I-II patients, undergoing video-assisted thoracic surgery. The study was approved by our Institutional Research Ethic Committee.
Upon written consent, patients were randomized to receive a T5 ESPB with 0.25% levo-bupivacaine 20 mL (LB) or 0.25% levo-bupivacaine plus 100mcg epinephrine, 20 mL (LB-E). ESPB was done by an experienced regional anesthetist. Patients were awake, standard monitoring, iv-line, and arterial line. After ESPB, arterial blood samples were drawn at 5, 10, 20, 30, 45, 60 y 90 minutes. Samples were transferred in EDTA test tubes, plasma was separated and kept at 5°Celsius until analyzed with HPLC technique.
All patients received a standard protocolized general anesthesia after 15 minutes of block completion.
Results 38 patients (19 LB, 19 LE-B) 18–74 years old, were studied. Overall levels and descriptive statistics are presented in figure 1 and 2. Peak arterial plasma concentrations were (median;25–75 percentile) 0.64; 0.50–1,11 mcg/mL in LB group and 0.42; 0.29–0.53 mcg/mL in LB-E group. Mann-Whitney analysis p=0.0046. There was no difference in time to peak concentration (median;25–75 percentile): 10 min;5–20 in LB, and 10 min;5–20 in LB-E. AUC calculations were different: LB 46.63 mcg/mL*min (CI95 28.08–65.17) and LB-E 27.91 mcg/mL*min (CI95 15.56–40.26).
Conclusions Adding epinephrine diminishes levo-bupivacaine arterial plasma levels after thoracic ESPB.
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