Discussion
toxicity, cardiotoxicity, pain
SEPARATION, COMPLICATIONS
In this prospective, double-blind up-and-down sequential allocation study, we estimated the minimum effective concentration for 50%(MEC50) and 95%(MEC95) patients in two different volumes of ropivacaine for CEB. Ropivacaine is an amide-type local anesthetic with a long-acting mechanism of action that is usually well tolerated and considered to have a longer blocking effect, much has a lower cardiotoxicity and greater sensory and motor block separation than other local anesthetics. it has been widely used for CEB in children and adults [The choice of local anesthetic agent, doses, concentrations, and volume can influence the onset, spread, quality of blockade, and duration of anesthesia [There are several methods that can improve the success rates of CEB. Firstly, using ultrasound-guided in-plane puncture technique, which helped me see the needle's entire length in the sacral lumen. The serious complications of caudal epidurals are accidental intrathecal injection and intravascular injection caused by variable filum terminale termination. It has been suggested that the needle should not be inserted too cephalad into the sacral canal and its tip should be visible under an ultrasound image to avoid dural puncture. Secondly, When we are not sure whether the puncture needle is in the sacral lumen for some patients with unclear anatomy, the needle tip was confirmed using a transverse view (frog’s face), and few milliliters of drug was injected in a pulsatile manner, and the expansion of the epidural space was observed.The limitation of study is that all blocks were performed by a highly experienced anesthesiologist, which might limit the applicability of our findings. Another limitation of our study was the lack of quantitative and objective markers as indicators of a successful CEB. For example, to date, no objective measure of pain has been developed to quantify the degree of pain, and there is no way to objectively gauge how much the anal sphincter relaxes. Furthermore, sex differences have not been taken into consideration, and the guiding principle for recruiting participants was to have a mix of included and fewer excluded participants, rather than focusing on sex differences. To strengthen the validity of our study results, we need to conduct further dose-finding studies using other volumes of ropivacaine, other LAs, and out-of-plane injection techniques. Future clinical studies should focus on the optimal concentration and volume of ropivacaine for CEB and the optimum weight ratio of local anesthetic concentration and volume for CEB with the greatest benefit for anorectal surgery and minimal risk of toxicity.