Does the Common Practice of Adding Diluted Epinephrine in Tranverse Abdominal Plan Block to Ropivacaine Significantly Decrease the Peak Systemic Resorption of Ropivacaine?

Locoregional anesthesia techniques are now widely recommended in perioperative multimodal analgesia protocols. The transverse abdominal plane block (TAP block), which consists of the injection of a local anesthetic in the vascular-nervous plane between the internal oblique muscle and the transverse abdominal muscle, has seen a significant increase in abdominal surgery with the advent of ultrasound guidance. Aimed at blocking the nerves destined to the antero-lateral abdominal wall, it has shown a benefit in several abdominopelvic surgeries with in particular a reduction of pain and a morphine sparing during the 24 postoperative hours as well as a shortening of the delay of resumption of the intestinal transit.

Ropivacaine is the molecule of choice in transverse abdominal plane block because of its better safety profile among long-acting local anesthetics. Nevertheless, transverse abdominal plane block using ropivacaine has a risk of systemic toxicity, correlated to the peak systemic resorption of the local anesthetic, whose low incidence is probably underestimated in patients under general anesthesia.

In this context, the addition of diluted adrenaline to the ropivacaine solution is a common practice in loco-regional anesthesia, including transverse abdominal plane block, to increase the duration of the peripheral block and reduce the peak plasma concentration of the local anesthetic.

The objective of our study is to compare the pharmacokinetics of total and free ropivacaine administered in transverse abdominal plane block at the minimum effective dosage of 1 mg/kg without and with the addition of epinephrine at the concentration of 1:200000 (5 µg/mL) in patients scheduled for laparoscopic colectomy. The hypothesis is a significant reduction in the mean maximum concentration (Cmax) of total or free plasma ropivacaine in the adrenalized block transverse abdominal plane group.

The practical applications in case of verification of the hypothesis are the provision of an argument to recommend the systematic adrenalization of the transverse abdominal plane block with ropivacaine in the interest of patient safety and the prospect of a downward reassessment of the minimum time to be respected between the administration of a transverse abdominal plane block with ropivacaine and that of another locoregional anesthesia.