Peak plasma concentration of total and free bupivacaine after erector spinae plane and pectointercostal fascial plane blocks

Purpose Erector spinae plane blocks (ESPB) and pectointercostal fascial (PIFB) plane blocks are novel interfascial blocks for which local anesthetic (LA) doses and concentrations necessary to achieve safe and effective analgesia are unknown. The goal of this prospective observational study was to provide the timing (T-max) and concentration (C-max) of maximum total and free plasma bupivacaine after ESPB in breast surgery and after PIFB in cardiac surgery patients. Methods Erector spinae plane blocks or PIFBs (18 patients per block; total, 36 patients) were performed with 2 mg.kg(-1) of bupivacaine with epinephrine 5 mu g.mL(-1). Our principal outcomes were the mean or median C-max of total and free plasma bupivacaine measured 10, 20, 30, 45, 60, 90, 180, and 240 min after LA injection using liquid chromatography with tandem mass spectrometry. Results For ESPB, the mean (standard deviation [SD]) total bupivacaine C-max was 0.37 (0.12) mu g.mL(-1) (range, 0.19 to 0.64), and the median [interquartile range (IQR)] T-max was 30 [50] min (range, 10-180). For ESPB, the mean (SD) free bupivacaine C-max was 0.015 (0.017) mu g.mL(-1) (range, 0.003-0.067), and the median [IQR] T-max was 30 [20] min (range, 10-120). After PIFB, mean plasma concentrations plateaued at 60-240 min. For PIFB, the mean (SD) total bupivacaine C-max was 0.32 (0.21) mu g.mL(-1) (range, 0.14-0.95), with a median [IQR] T-max of 120 [150] min (range, 30-240). For PIFB, the mean (SD) free bupivacaine C-max was 0.019 (0.010) mu g.mL(-1) (range, 0.005-0.048), and the median [IQR] T-max was 180 [120] min (range, 30-240). For both ESPB and PIFB, we observed no correlations between pharmacokinetic and demographic parameters. Conclusion Total and free bupivacaine C-max observed after ESPB and PIFB with 2 mg.kg(-1) of bupivacaine with epinephrine 5 mu g.mL(-1) were five to twenty times lower than levels considered toxic in the literature.

Automated summary

The aim of this study was to investigate the maximum concentrations and timing of plasma bupivacaine after ESPB and PIFB. The study found that the C-max of total and free bupivacaine were significantly lower than toxic levels reported in the literature when using a dose of 2 mg/kg.