S-ketamine versus racemic ketamine in dogs: their relative potency as induction agents.

OBJECTIVE To determine the potency ratio between S-ketamine and racemic ketamine as inductive agents for achieving tracheal intubation in dogs. STUDY DESIGN Prospective, randomized, 'blinded', clinical trial conducted in two consecutive phases. ANIMALS 112 client-owned dogs (ASA I or II). METHODS All animals were premedicated with intramuscular acepromazine (0.02 mg kg(-1) ) and methadone (0.2 mg kg(-1) ). In phase 1, midazolam (0.2 mg kg(-1) ) with either 3 mg kg(-1) of racemic ketamine (group K) or 1.5 mg kg(-1) of S-ketamine (group S) was administered IV, for induction of anaesthesia and intubation. Up to two additional doses of racemic (1.5 mg kg(-1) ) or S-ketamine (0.75 mg kg(-1) ) were administered if required. In phase 2, midazolam (0.2 mg kg(-1) ) with 1 mg kg(-1) of either racemic ketamine (group K) or S-ketamine (group S) was injected and followed by a continuous infusion (1 mg kg minute(-1) ) of each respective drug. Differences between groups were statistically analyzed via t-test, Fisher exact test and ANOVA for repeated measures. RESULTS Demographics and quality and duration of premedication, induction and intubation were comparable among groups. During phase 1 it was possible to achieve tracheal intubation after a single dose in more dogs in group K (n = 25) than in group S (n = 16) (p = 0.046). A dose of 3 mg kg(-1) S-ketamine allowed tracheal intubation in the same number of dogs as 4.5 mg kg(-1) of racemic ketamine. The estimated potency ratio was 1.5:1. During phase 2, the total dose (mean ± SD) of S-ketamine (4.02 ±1.56 mg kg(-1) ) and racemic ketamine (4.01 ± 1.42) required for tracheal intubation was similar. CONCLUSION AND CLINICAL RELEVANCE Racemic and S-ketamine provide a similar quality of anaesthetic induction and intubation. S-ketamine is not twice as potent as racemic ketamine and, if infused, the potency ratio is 1:1.

Retention of Root Canal Posts: Effect of Cement Film Thickness, Luting Cement, and Post Pretreatment.

The aim of this study was to investigate the effect of the cement film thickness of a zinc phosphate or a resin cement on retention of untreated and pretreated root canal posts. Prefabricated zirconia posts (CosmoPost: 1.4 mm) and two types of luting cements (a zinc phosphate cement [DeTrey Zinc] and a self-etch adhesive resin cement [Panavia F2.0]) were used. After removal of the crowns of 360 extracted premolars, canines, or incisors, the root canals were prepared with a parallel-sided drill system to three different final diameters. Half the posts did not receive any pretreatment. The other half received tribochemical silicate coating according to the manufacturer's instructions. Posts were then luted in the prepared root canals (n=30 per group). Following water storage at 37°C for seven days, retention of the posts was determined by the pull-out method. Irrespective of the luting cement, pretreatment with tribochemical silicate coating significantly increased retention of the posts. Increased cement film thickness resulted in decreased retention of untreated posts and of pretreated posts luted with zinc phosphate cement. Increased cement film thickness had no influence on retention of pretreated posts luted with resin cement. Thus, retention of the posts was influenced by the type of luting cement, by the cement film thickness, and by the post pretreatment.

Scleral thinning after repeated intravitreal injections of antivascular endothelial growth factor agents in the same quadrant

PURPOSE We assessed the effects of intravitreal anti-vascular endothelial growth factor (anti-VEGF) therapy on scleral architecture using spectral domain anterior segment optical coherence tomography (OCT). METHODS A total of 35 eyes of 35 patients treated with at least 30 intravitreal injections in one eye in the inferotemporal quadrant with ranibizumab or aflibercept and 10 or less intravitreal injections in the fellow eye attending the intravitreal injection clinic were included. Enhanced depth imaging anterior segment OCT was used to measure scleral thickness. For each eye the sclera was measured in four quadrants at 3 mm from the limbus. In addition axial eye length was measured in all subjects using partial coherence interferometry. RESULTS The mean number of intravitreal injections was 42 (range, 30-73) and 1.6 (range, 0-9) in the fellow eyes. In the study eyes with more than 30 injections the average scleral thickness in the inferotemporal quadrant was 568.4 μm (SD ± 66 μm) and 590.6 μm (SD ± 75 μm) in the fellow eyes with 10 or less injections (P = 0.003). The mean average scleral thickness in the other three quadrants (inferonasal, superotemporal, and superonasal) was 536.6 μm in the study eyes (SD ± 100 μm) and 545.2 μm (SD ± 109 μm) in the fellow eyes (P = 0.22). There was a borderline association of the total number of injections with scleral thickness change in the inferotemporal quadrant (r = 0.3, P = 0.052). CONCLUSIONS Intravitreal injections may lead to scleral changes when applied repeatedly in the same quadrant. Thus, alternating the injection site should be considered in patients requiring multiple intravitreal injections.

Functionalization of PAMAM dendrimers with nitronyl nitroxide radicals as models for the outer-sphere relaxation in dentritic potential MRI contrast agents

PAMAM dendrimers functionalized with nitronyl nitroxide radicals were characterized. Quantitative determination of substitution with radicals was performed using EPR and electrochemical methods. The study of the 1H NMR relaxation of the surrounding water showed how the outer-sphere contribution to the relaxivity may be limited by the presence of the dendrimer core.