Background and Aims:Knee replacement surgery causes tremendous post-operative pain and adductor canal block (ACB) is used for post-operative analgesia. This is a randomised, controlled, three-arm parallel group study using different doses of dexmedetomidine added to ropiavcaine for ACB.Methods:A total of 150 patients aged 18–75 years, scheduled for simultaneous bilateral total knee replacement, received ultrasound-guided ACB. They were randomised into three groups -Group A received ACB with plain ropivacaine; Groups B and C received ACB with ropivacaine and addition of dexmedetomidine 0.25 μg/kg and 0.50 μg/kg, respectively, on each side of ACB. The primary outcome was the duration of analgesia. Total opioid consumption, success of early ambulation, and level of patient satisfaction were also assessed.Results:The patient characteristics and block success rates were comparable in all groups. Group C patients had longer duration of analgesia (Group C 18.4 h ± 7.4; Group B 14.6 ± 7.1; Group A 10.8 ± 7; P < 0.001); lesser tramadol consumption (Group C 43.8 mg ± 53.2; Group B 76.4 ± 49.6; Group A 93.9 mg ± 58.3; P < 0.001) and lesser pain on movement (P < 0.001). The patients in Group B and C walked more steps than in Group A (P < 0.002). The level of patient satisfaction was highest in Group C (P < 0.001).Conclusions:The addition of dexmedetomidine to ropivacaine resulted in longer duration of analgesia after adductor canal block for simultaneous bilateral total knee replacement surgery.

The substitution of the chelating oxalate group by a group of nucleophiles, viz. thiourea (L1), 2‐thiouracil (L2), diethyldithiocarbamate (L3), dl‐penicillamine (L4), and thiosemicarbazide (L5) was studied under pseudo–first‐order conditions as a function of concentration and temperature using UV–vis spectrophotometry and stopped‐flow technique. π‐Accepting effects are often used to account for the unusual high lability of Pt(bipy) complexes. The complexes [Pt(dach)(oxalate)] (1) (dach = cis‐1,2‐diaminocyclohexane) and [Pt(bipy)(oxalate)] (2) (bipy = 2,2'‐bipyridine) and substituted products were isolated and characterized by FTIR and ESI‐MS spectroscopic analysis. The negative entropies of activation support a strong contribution from bond making in the transition state of the substitution processes.

Kinetics of aqua ligand substitution from diaquaethylenediamineplatinum(II) ion by three vicinal dioximes, namely dimethylglyoxime, 1,2-cyclohexanedione dioxime, and a-furil dioxime have been studied spectrophotometrically in the 40-55°C temperature range. All the above substitution reactions have been monitored at 297, 298, and 314 nm where the differences in absorbances between the reactant and products are maximum. At pH 4.0, all the three reactions have been found to proceed via two distinct consecutive steps, i.e., it shows a non-linear dependence on the concentrations of ligands: first step is [ligand] dependent but the second step is [ligand] independent. The rate constants for the processes are k 1 * 10 -3 and k 2 * 10 -5 s -1 . The activation parameters, calculated from Eyring plots, suggest an associative mechanism for the interaction processes. From the temperature dependence of the outer sphere association equilibrium constants (K E ) for the first step, the thermodynamic parameters were also calculated, which gives a negative DG 0 1 value at all temperatures studied, supporting the spontaneous formation of an outer sphere association complex in the first step. The products of the reactions have been characterized with the help of Job's method, IR and ESI-MS spectroscopic analysis. Graphical abstract

The kinetics of the interactions between three sulfur-containing ligands, thioglycolic acid, 2-thiouracil, glutathione, and the title complex, have been studied spectrophotometrically in aqueous medium as a function of the concentrations of the ligands, temperature, and pH at constant ionic strength. The reactions follow a two-step process in which the first step is ligand-dependent and the second step is ligand-independent chelation. Rate constants (k 1 ß10 −3 s −1 and k 2 ß10 −5 s −1 ) and activation parameters (for thioglycolic acid:= −105 ± 3 J K −1 mol −1 ) were calculated. Based on the kinetic and activation parameters, an associative interchange mechanism is proposed for the interaction processes. The products of the reactions have been characterized from IR and ESI mass spectroscopic analysis.