Preparação, caracterização e avaliação in vitro de microesferas de bupivacaína em excesso enantiomérico de 50% (S75-R25)

Analysis of the acute cytotoxic potential of bupivacaine and 50% enantiomeric excess bupivacaine (s75-r25) incorporated into microspheres in rat sciatic nerves

BACKGROUND AND OBJECTIVES

The duration of Local Anesthetic (LA) effects can be expanded by its incorporation into systems of sustained release microspheres. However, the possibility that LA sustained release systems are neurotoxic has not received due attention in literature. The objective of this study was to investigate the effects of pure microspheres of poly(lactic-co-glycolic acid), filled with 50% enantiomeric excess bupivacaine or bupivacaine (BP), as well as the effects of 50% enantiomeric excess bupivacaine in the sciatic nerve of Wistar rats.

METHODS

The rats were allocated into four groups according to the evaluation time (two, four, six, and eight days) and nominated according to the injected solution on the sciatic nerve: Microspheres with 50% Enantiomeric excess Bupivacaine (MEB), Microspheres with Bupivacaine (MB), Pure Microspheres (PM), and 50% Enantiomeric excess Bupivacaine (EB).

RESULTS

In semi-fine histologic sections, no regular homogeneous distribution of collagen fibers in the endoneurium or degenerative changes of axons and myelin sheaths were observed. In ultrathin sections, we found myelinated axons and normal Remak fibers with axoplasm showing homogeneous distribution of neurofilaments and microtubules. Histomorphometric analysis of axons revealed no significant difference between the axon diameters of the studied groups.

Assessing the use of 50% enantiomeric excess bupivacaine-loaded microspheres after sciatic nerve block in rats

BACKGROUND AND OBJECTIVES

To achieve better therapeutic benefits of local anesthetics in the control of postoperative pain through controlled-release carrier. The objective of this study was to compare the characteristics of sensory and motor blockade between microspheres without local anesthetic: racemic bupivacaine-loaded microspheres; 50% enantiomeric excess bupivacaine-loaded microspheres; and free 50% enantiomeric excess bupivacaine.

METHODS

Wistar rats were distributed into four groups: A (Microsphere); B (S50-R50 bupivacaine-loaded microsphere); C (50% enantiomeric excess bupivacaine-loaded microsphere); and D (50% enantiomeric excess bupivacaine). Inhalation anesthesia was performed before the sciatic nerve block (2% halothane and 100% O(2)). Sensorial blockade was measured by the time required for each rat to withdraw its paw from a hot plate at 56°C (positive>4 sec). Motor blockade was measured by the time between drug injection until recovery of a motor score of 2 on the established criterion.

RESULTS

The sensory response was significantly more frequent in groups B, C, and D than in group A (p<0.001). There were no statistically significant differences in the response to the sensory test in groups B, C, and D (p>0.05). The response to the motor test was also significantly more frequent in groups B, C, and D than in group A (p=0.02). A tendency to greater positivity in the motor test was more frequently found in groups B and D than in group C (p=0.10).

CONCLUSIONS

Controlled-release of 50% enantiomeric excess bupivacaine-loaded microspheres showed similar results regarding analgesia and less motor blockade when compared to other anesthetic formulations.

Assessing the quality of random clinical anesthesiology trials published on the Brazilian Journal of Anesthesiology from 2005 to 2008

BACKGROUND AND OBJECTIVES

A random clinical trial (RCT) is defined as a study involving intervention and control groups with random distribution of the participants. The objective of the present study was to assess the quality of RCT in anesthesiology published during a specific time.

DESIGN OF THE STUDY

descriptive.

METHODS

A manual search of the articles published by the Brazilian Journal of Anesthesiology between January 2005 and February 2008 was undertaken to identify studies with characteristics of RCTs. The quality of RCTs was the primary parameter; secondary parameters included: approval by the Ethics on Research Committee (ERC), use of the informed consent (IC), description of the source of the grant, the sample size was calculated, number of authors, place of origin, statistical tests used, level of significance adopted, and classification of the type of study. The quality scale, descriptive statistics, and calculation of the 95% confidence interval were used to evaluate the quality of the RCTs.

RESULTS

Out of 114 studies, 42 were identified as RCT. Only 3 (7.1%) of those were classified as having good methodological quality considering the random distribution, double blind, losses, and exclusions. One-hundred and seven out of 114 studies were submitted to the ERC, 67 used IC, none of them described the source of the grant, 17 calculated the size of the sample, the studies had a mean of 4.49 authors; 60 publications were from São Paulo; the Student t test was used more often (47.4%), a level of significance of 5% was adopted by 97 studies; and 42 were RCTs.

CONCLUSIONS

After the manual search, 7.1% of the random clinical assays were considered of good methodological quality.