During the past decade, numerous efforts were undertaken aiming at prolonging the analgesic effect of regional anesthesia. With the development of extended-release formulations and enhanced selectivity for nociceptive sensory neurons, a very promising contribution to the development of pain medications has been achieved. At present, liposomal bupivacaine is the most popular, non-opioid, controlled drug delivery system, but its duration of action, which is still controversially discussed, and its expensiveness have decreased initial enthusiasm. Continuous techniques can be seen as an elegant alternative for providing a prolonged duration of analgesia, but for logistic or anatomical reasons, they are not always the best choice. Therefore, focus has been directed towards the perineural and/or intravenous addition of old and established substances. As for perineural application, most of these so-called ‘adjuvants’ are used outside their indication, and their pharmacological efficacy is often not or only poorly understood. This review aims to summarize the recent developments for prolonging the duration of regional anesthesia. It will also discuss the potential harmful interactions and side effects of frequently used analgesic mixtures.

Background: This randomised crossover mannequin study aimed to compare the insertion time for the newly developed Singularity^TM Air and the Ambu^® AuraGain^TM. The Singularity^TM Air includes a bendable tube in order to allow optimal passform. Methods: Fifty anaesthetists with a minimum of 100 supraglottic airway device insertions were recruited and randomly assigned to start either with the Singularity^TM Air or with the Ambu^® AuraGain^TM. Participants watched a tutorial video the day before the assessment and received a standardized introduction immediately before the assessment. The primary outcome was the time for successful insertion. Secondary parameters were the overall insertion success rate, the numbers of insertion attempts (maximum three), the glottic view through a flexible bronchoscope, and the success rate for gastric tube insertion. Results: Fifty participants were eventually recruited and randomly assigned to insert both devices according to the randomization. The insertion time was 24 s for Singularity^TM Air as compared to 20 s for Ambu^® AuraGain^TM (p < 0.001). Overall insertion rate was 92% for the Singularity^TM Air as compared to 100% for the Ambu^® AuraGain^TM (p could not be derived as one variable is a constant). The primary insertion success rate was better for the Ambu^® AuraGain^TM than for the Singularity^TM Air (94% versus 68%; p: 0.002, respectively). Conclusion: The time for successful insertion and the insertion success rate for the newly developed Singularity^TM Air is inferior to that for the Ambu^® AuraGain^TM.