Dexmedetomidine as an adjuvant to local anesthetics in brachial plexus blocks: A meta-analysis of randomized controlled trials.

BACKGROUND: Brachial plexus block (BPB) for upper extremity surgery provides superior analgesia, but this advantage is limited by the pharmacological duration of local anesthetics. Dexmedetomidine (DEX) as a local anesthetics adjuvant for BPB has been utilized to prolong the duration of the nerve block in some randomized controlled trials (RCTs) but is far from unanimous in the efficacy and safety of the perineural route. Hence, an updated meta-analysis was conducted to assess the efficacy and safety of DEX as local anesthetic adjuvants on BPB. METHODS: A search in electronic databases was conducted to collect the RCTs that investigated the impact of adding DEX to local anesthetics for BPB. Sensory block duration, motor block duration, onset time of sensory and motor block, time to first analgesic request, the common adverse effects were analyzed. RESULTS: Eighteen trails (1014 patients) were included with 515 patients receiving perineural DEX. The addition of DEX prolonged the duration of sensory block (WMD 257 minutes, 95%CI 191.79-322.24, P < 0.001), motor block (WMD 242 minutes, 95%CI 174.94-309.34, P < 0.001), and analgesia (WMD 26 6 minutes, 95%CI 190.75-342.81, P < 0.001). Perineural DEX also increased the risk of bradycardia (OR=8.25, 95%CI 3.95-17.24, P < 0.001), hypotension (OR = 5.62, 95%CI 1.52-20.79, P < 0.01), and somnolence (OR = 19.67, 95%CI 3.94-98.09, P < 0.001). There was a lack of evidence that perineural DEX increased the risk of other adverse events. CONCLUSIONS: DEX is a potential anesthetic adjuvant that can facilitate better anesthesia and analgesia when administered in BPB. However, it also increased the risk of bradycardia, hypotension, and somnolence. Further research should focus on the efficacy and safety of the preneural administration of DEX.

Molecular and quantitative trait variation within and among small fragmented populations of the endangered plant species Psilopeganum sinense.

BACKGROUND AND AIMS: Natural selection and genetic drift are important evolutionary forces in determining genetic and phenotypic differentiation in plant populations. The extent to which these two distinct evolutionary forces affect locally adaptive quantitative traits has been well studied in common plant and animal species. However, we know less about how quantitative traits respond to selection pressures and drift in endangered species that have small population sizes and fragmented distributions. To address this question, this study assessed the relative strengths of selection and genetic drift in shaping population differentiation of phenotypic traits in Psilopeganum sinense, a naturally rare and recently endangered plant species. METHODS: Population differentiation at five quantitative traits (QST) obtained from a common garden experiment was compared with differentiation at putatively neutral microsatellite markers (FST) in seven populations of P. sinense. QST estimates were derived using a Bayesian hierarchical variance component method. KEY RESULTS: Trait-specific QST values were equal to or lower than FST. Neutral genetic diversity was not correlated with quantitative genetic variation within the populations of P. sinense. CONCLUSIONS: Despite the prevalent empirical evidence for QST > FST, the results instead suggest a definitive role of stabilizing selection and drift leading to phenotypic differentiation among small populations. Three traits exhibited a significantly lower QST relative to FST, suggesting that populations of P. sinense might have experienced stabilizing selection for the same optimal phenotypes despite large geographical distances between populations and habitat fragmentation. For the other two traits, QST estimates were of the same magnitude as FST, indicating that divergence in these traits could have been achieved by genetic drift alone. The lack of correlation between molecular marker and quantitative genetic variation suggests that sophisticated considerations are required for the inference of conservation measures of P. sinense from neutral genetic markers.

[Comparison of ultrasound and nerve stimulation techniques for brachial plexus block for regional hemodynamic changes of upper extremity].

OBJECTIVE: To compare ultrasound guidance versus nerve stimulator guidance supraclavicular brachial plexus block for regional hemodynamic changes of upper extremity. METHODS: Sixty ASA I-II patients scheduled for upper extremity operation were randomly assigned to receive a supraclavicular brachial plexus block guided by either ultrasound (U group, n = 30) or nerve stimulation (N group, n = 30).20 ml mixture of equal volumes of 2% lidocaine and 0.75% ropivacaine was injected in both groups. Regional hemodynamic parameters were measured in the ipsilateral ulnar artery and radial artery, using pulsed-wave Doppler ultrasound, before and 30 minutes after the block. Regional hemodynamic parameters included peak systolic velocity (PSV), end-diastolic velocity (EDV), time averaged maximum velocity (TAMAX), resistance index (RI), pulsatility index (PI), cross-sectional area (Area) and Blood flow (Q). The intensity of sensory block was measured at 30 minutes after the block. RESULTS: There was no significant difference in the hemodynamic parameters of ulnar artery and radial artery before the block between two groups. Compared with N group, EDV, TAMAX and Q of ulnar artery were higher in U group (1.88-fold, 1.71-fold and 1.84-fold)(P < 0.01 or P < 0.05), PI and RI of ulnar artery were lower in U group (P < 0.01) at 30 minutes after the block, EDV of radial artery was higher in U group (1.47-fold) (P < 0.01), PI and RI of radial artery were lower in U group (P < 0.05) at 30 minutes after the block. Comparing the hemodynamic parameters of ulnar artery and radial artery with complete block between two groups at 30 minutes after the block, EDV, TAMAX and Q of ulnar artery in U group were higher than that in N group (1.68-fold, 1.55-fold and 1.62-fold) (P < 0.01 or P < 0.05), PI of ulnar artery in U group was lower than that in N group (P < 0.01), EDV and TAMAX of radial artery in U group was higher than that in N group (1.54-fold and 1.26-fold) (P < 0.01 or P < 0.05), PI and RI of radial artery in U group was lower than that in N group (P < 0.05). The rate of complete block in U group was higher than that in N group (28/30 vs 22/30, P < 0.05). CONCLUSION: Ultrasound-guided supraclavicular brachial plexus block enhance the degree of sympathetic block of upper extremity, especially of ulnar artery and increase the blood flow of ulnar artery compared with nerve stimulator.

Spontaneous interspecific hybridization and patterns of pollen dispersal in ex situ populations of a tree species (Sinojackia xylocarpa) that is extinct in the wild.

For endangered plants interspecific hybridization occurring in ex situ collections may lead to failure of reintroduction actions. We used Sinojackia xylocarpa, a well documented Chinese endemic species that is extinct in the wild, as a model case to address this concern. We used paternity analyses to assess the spontaneous hybridization and patterns of pollen flow between S. xylocarpa and its congener species, S. rehderiana, in conserved populations in Wuhan Botanic Garden. Interspecific hybridization events were detected in seven out of eight maternal trees of S. xylocarpa, and an average of 32.7% seeds collected from maternal trees of S. xylocarpa were hybrids. The paternity of 93 out of 249 seedlings from S. xylocarpa assigned to S. rehderiana provided convincing evidence that spontaneous interspecific hybridization occurred extensively in the living garden collection we studied. Different patterns of pollen dispersal (predominantly short-distance vs. long-distance pollination) were observed between intra- and interspecific hybridization events in the garden. Pollen dispersal within the ex situ populations was not restricted by distance, as evidenced by a lack of significant correlations between the average effective pollen dispersal distance (delta) and the geographic distances (d1 and d2) between maternal and paternal trees. The interspecific pollen-dispersal distance ranged from 10 to 620.1 m (mean 294.4 m). Such extensive hybridization in ex situ collections could jeopardize the genetic integrity of endangered species and irrevocably contaminate the gene pool if such hybrids are used for reintroduction and restoration. We recommend strongly that measures be taken to minimize the genetic risks of this kind of hybridization, including establishing buffer zones in ex situ collections, manipulating flowering phenology, testing seed lots before use in reintroduction programs, and controlling pollination for seed purity.

Neither biased sex ratio nor spatial segregation of the sexes in the subtropical dioecious tree Eurycorymbus cavaleriei (Sapindaceae).

Knowledge of sex ratio and spatial distribution of males and females of dioecious species is both of evolutionary interest and of crucial importance for biological conservation. Eurycorymbus cavaleriei, the only species in the genus Eurycorymbus (Sapindaceae), is a dioecious tree endemic to subtropical montane forest in South China. Sex ratios were investigated in 15 natural populations for the two defined ages (young and old). Spatial distribution of males and females was further studied in six large populations occurring in different habitats (fragmented and continuous). The study revealed a slight trend of male-biased sex ratio in both ages of E. cavaleriei, but sex ratio of most populations (13 out of 15) did not display statistically significant deviation from equality. All of the four significantly male-biased populations in the young class shifted to equality or even female-biased. The Ripley's K analysis of the distribution of males with respect to females suggested that individuals of the opposite sexes were more randomly distributed rather than spatially structured. These results suggest that the male-biased sex ratio in E. cavaleriei may result from the precocity of males and habitat heterogeneity. The sex ratio and the sex spatial distribution pattern are unlikely to constitute a serious threat to the survival of the species.

Phylogeny of Sinojackia (Styracaceae) based on DNA sequence and microsatellite data: implications for taxonomy and conservation.

BACKGROUND AND AIMS: The genus Sinojackia consists of eight species, all endemic to China. All species of Sinojackia are endangered or threatened owing to poor recruitment within populations. Information on molecular phylogenetics is critical for developing successful conservation strategies for this genus. METHODS: Combined DNA sequence data from the nuclear ribosomal internal transcribed spacer regions and plastid psbA-trnH intergenic spacer and microsatellite data were used to infer a phylogeny of the genus. KEY RESULTS: Parsimony analysis of the combined sequence data and multivariate analysis based on fruit characters indicated that Sinojackia dolichocarpa is monophyletic and genetically well separated from the other Sinojackia species, thus supporting its rank at the generic level as Changiostyrax. Phylogenetic relationships within Sinojackia sensu stricto are unresolved from the combined sequence data. A UPGMA dendrogram based on seven microsatellite loci of 96 individual plants yielded a first-diverging cluster of all individuals of S. microcarpa. The remaining species form another cluster without any definitive patterns corresponding to current species circumscriptions, suggesting either extensive hybridization or incipient speciation. CONCLUSIONS: The results suggest that there are too many species recognized within Sinojackia sensu stricto, but this must be further assessed with comprehensive morphological and taxonomic revisionary work. The implications of the phylogenetic data for conservation are discussed.

Isolation and characterization of microsatellite loci in Psilopeganum sinense Hemsl (Rutaceae), an endangered herb endemic to Yangtze River valley.

Twenty-nine primer pairs flanking microsatellite repeats were designed from an AC-enriched genomic library of Psilopeganum sinense and tested using 24 individuals derived from a natural population. A total of 11 microsatellite loci were found polymorphic. The number of alleles per locus varied from two to eight, with an average value of 3.7. The ranges of observed and expected heterozygosities were 0.000-0.750 and 0.365-0.800, respectively. These microsatellite loci have been directly applied to the ongoing conservation genetic studies of P. sinense.

Microsatellite analysis reveals interpopulation differentiation and gene flow in the endangered tree Changiostyrax dolichocarpa (Styracaceae) with fragmented distribution in central China.

Polymorphic simple sequence repeat (SSR) markers were used to investigate the impact of habitat fragmentation on the population structure and gene flow of Changiostyrax dolichocarpa, a critically endangered tree in central China. Intrapopulation genetic diversity, population structure and gene flow in the five extant populations of this species were analysed by eight SSR markers. Intrapopulation genetic diversity results suggest that C. dolichocarpa remnants maintained a relatively high degree of genetic diversity despite severe fragmentation. Low genetic differentiation among populations was found based on Wright's F(ST) and amova analysis. Both the F(ST)-based estimate and private allele method revealed high historical gene flow among the remnant populations. Recent immigrants, detected by assignment tests, tend to decrease from the grandparent generation to the current generation. The potentially highly restricted current gene flow among fragments may render the fragmented populations of C. dolichocarpa at a higher risk of local extinction several generations after fragmentation. Both in situ and ex situ conservation management for the remnant populations of C. dolichocarpa are therefore urgently needed to rescue remaining genetic diversity.

Genetic consequence of restricted habitat and population decline in endangered Isoetes sinensis (Isoetaceae).

BACKGROUND AND AIMS: Isoetes sinensis (Isoeteaceae) is a critically endangered aquatic quillwort in eastern China. Rapid decline of extant population size and local population extinction have occurred in recent years and have raised great concerns among conservationists. METHODS: Amplified fragment length polymorphisms (AFLPs) were used to investigate the genetic variation and population structure of seven extant populations of the species. KEY RESULTS: Eight primer combinations produced a total of 343 unambiguous bands of which 210 (61.2 %) were polymorphic. Isoetes sinensis exhibited a high level of intra-population genetic diversity (H(E) = 0.118; hs = 0.147; I = 0.192; P = 35.2 %). The genetic variation within each of the populations was not positively correlated with their size, suggesting recent population decline, which is well in accordance with field data of demographic surveys. Moreover, a high degree of genetic differentiation (F(ST) = 0.535; G(ST) = 0.608; theta(B) = 0.607) was detected among populations and no correlation was found between geographical and genetic distance, suggesting that populations were in disequilibrium of migration-drift. Genetic drift played a more important role than gene flow in the current population genetic structure of I. sinensis because migration of I. sinensis is predominantly water-mediated and habitat range was highly influenced by environment changes. CONCLUSIONS: Genetic information obtained in the present study provides useful baseline data for formulating conservation strategies. Conservation management, including both reinforcement for in situ populations and ex situ conservation programmes should be carefully designed to avoid the potential risk of outbreeding depression by admixture of individuals from different regions. However, translocation within the same regional population should be considered as a measure of genetic enhancement to rehabilitate local populations. An ex situ conservation strategy for conserving all extant populations to maximize genomic representation of the species is also recommended.

[Genetic risks in plant ex situ conservation].

Conserving genetic diversity of rare and endangered species and their evolutionary potential is one of the long-term goals of ex-situ conservation. Some potential genetic risks in ex-situ conservation in botanical gardens are presented. The preserved species may lack genetic representativity because of poor sampling. Inappropriate plantations, inadequate records and unclear kinships jeopardize endangered species to genetic confusion, inbreeding depression or outbreeding depression. Artificial selection and habitat conversion also potentially result endangered plants in adapting to ex-situ conservation, which had been usually overlooked. All the genetic risks can decrease the success of reintroduction and recovery. Therefore, appropriate genetic management should be carried out in botanical gardens to decrease or avoid genetic risks in ex-situ conservation.