A Comparison of Local Infiltration Analgesia and PECS II Block for Analgesia in Mastectomy with Axillary Dissection—A Randomised Equivalence Study

Objective: Various analgesic techniques can be used for a mastectomy with axillary dissection with varying degrees of efficacy. In our institution, local anaesthesia infiltration (LIA) is commonly performed by surgeons. In this study, we hypothesise that the relatively novel PECS II block is equivalent to the analgesic profile of LIA. Methodology: In this single center, prospective, randomised control trial, 40 patients undergoing unilateral mastectomy with axillary dissection were randomly assigned to receive either 30 ml 0.5% ropivacaine before skin via LIA by a specialist breast surgeon during surgery or 30 ml 0.5% ropivacaine via PECS II block, before skin incision. Fentanyl was used as rescue analgesia intraoperatively, and all patients received morphine via patient-controlled analgesia (PCA) device postoperatively. The primary outcome was the difference in total morphine consumption in 24 hours between the 2 groups after surgery with equivalency set at ±1 mg. Secondary outcomes included time to rescue analgesia after block administration, post-operative pain score over 24 hours, adverse effects encountered, total intraoperative opioid usage, effect on operative time, block performance time as well as block and surgery related complications. Results: Unadjusted mean PCA morphine consumption over 24 hours post-operatively comparing local infiltration analgesia (LIA) to that of PECS II at 95% confidence interval was -1.22 mg (95% CI: -3.77, 1.33). Total IV Fentanyl use comparing LIA to PECS II was 2.53 ± 0.98 mcg/kg and 1.96 ± 0.57 mcg, P = 0.035. There were no other significant differences in the secondary outcome. Conclusion: We conclude there is a lack of equivalence between that of LIA and PECS II block, with the PECS II block providing superior analgesia.

Effects of laponite and silica nanoparticles on the cleaning performance of amylase towards starch soils

This work aims to understand the effect of nanoparticle-enzyme interactions and how such interactions affect starch based soil removal. Silica and laponite are used as the model nanoparticles, and s-amylase is employed as the model enzyme. The results show that, if the nanoparticles and enzyme are added simultaneously, laponite enhances the enzyme performance toward starch soil removal, whereas silica imposes a small effect on the enzymatic activity towards the same soil substrates. However, when nanoparticles are added first, the enzyme activity is not affected much by laponite but is hindered significantly by silica nanoparticles. Furthermore, sequential addition of the enzyme followed by silica nanoparticles improves soil removal. Electron microscopic analyses, measurements of the enzyme activity in suspen- sions of nanoparticles, and particle size characterisation suggest that dense coverage of soil surface by the silica nanoparticles be likely a mechanism for the experimentally observed hindrance of soil removal when silica nanoparticles are added before enzyme.