Multiple levels paravertebral block versus morphine patient-controlled analgesia for postoperative analgesia following breast cancer surgery with unilateral lumpectomy, and axillary lymph nodes dissection.

BACKGROUND: Postoperative pain after breast cancer surgery is not uncommon. Narcotic based analgesia is commonly used for postoperative pain management. However, the side-effects and complications of systemic narcotics is a significant disadvantage. Different locoregional anesthetic techniques have been tried including, single and multiple levels paravertebral block (PVB), which seems to have a significant reduction in immediate postoperative pain with fewer side-effects. The aim of this study was to compare unilateral multiple level PVB versus morphine patient-controlled analgesia (PCA) for pain relief after breast cancer surgery with unilateral lumpectomy and axillary lymph nodes dissection. MATERIALS AND METHODS: Forty patients scheduled for breast cancer surgery were randomized to receive either preoperative unilateral multiple injections PVB at five thoracic dermatomes (group P, 20 patients) or postoperative intravenous PCA with morphine (group M, 20 patients) for postoperative pain control. Numerical pain scale, mean arterial pressure, heart rate, Time to first analgesic demand, 24-h morphine consumption side-effects and length of hospital stay were recorded. RESULTS: PVB resulted in a significantly more postoperative analgesia, maintained hemodynamic, more significant reduction in nausea and vomiting, and shorter hospital stay compared with PCA patients. CONCLUSION: Multiple levels PVB is an effective regional anesthetic technique for postoperative pain management, it provides superior analgesia with less narcotics consumption, and fewer side-effects compared with PCA morphine for patients with breast cancer who undergo unilateral lumpectomy, with axillary lymph nodes dissection.

Biological and mechanical properties of PMMA-based bioactive bone cements.

We reported previously that a bioactive PMMA-based cement was obtained by using a dry method of silanation of apatite-wollastonite glass ceramic (AW-GC) particles, and using high molecular weight PMMA particles. But handling and mechanical properties of the cement were poor (Mousa et al., J Biomed Mater Res 1999;47:336-44). In the present study, we investigated the effect of the characteristics of PMMA powder on the cement. Different cements containing different PMMA powders (CMW1, Surgical Simplex, Palacos-R and other two types of PMMA powders with Mw 270,000 and 1,200,000) and AW-GC filler in 70 wt% ratio except Palacos-R (abbreviated as B-CMW1 and B-Surg Simp, B-Palacos 50 [50 wt% AW-GC filler] and B-Palacos 70 [70 wt% AW-GC filler], B-270 and B-1200) were made. Dough and setting times of B-CMW1, B-Surg Simp B-270 and B-1200 were similar to the commercial CMW1 cement which did not contain bioactive powder (C-CMW1), but B-palacos which contained large PMMA beads with high Mw had delayed setting time. B-270 had the highest bending strength among the tested cements. After 4 and 8 weeks of implantation in the medullary canals of rat tibiae, the bone-cement interface was examined using SEM. The affinity index of B-1200 was significantly higher than the other types of cements. B-270 showed good combination of handling properties, high mechanical properties and showed higher bioactivity with minimal soft tissue interposition between bone and cement compared with commercial PMMA bone cement. This may increase the strength of the bone-cement interface and increase the longevity of cemented arthroplasties.

Thiopental induces contraction of rat aortic smooth muscle through Ca(2+) release from the sarcoplasmic reticulum.

UNLABELLED: Little is known about the mechanism of thiopental-induced contraction in vascular smooth muscle. This study aimed to clarify this question by conducting isometric tension experiments and (45)Ca(2+) flux measurements in endothelium-denuded rat aortic rings. Thiopental induced a concentration-dependent contraction under basal tension. This contraction was enhanced when rings were precontracted with phenylephrine in the presence of verapamil. In Ca(2+)-free solution, thiopental-induced contraction was reduced but not abolished with high concentrations. Ca(2+) store depletion with a maximum dose of caffeine in Ca(2+)-free solution further reduced the contraction by subsequent thiopental. Ca(2+) store depletion with thapsigargin completely abolished contraction by thiopental. (45)Ca(2+) influx experiment in the presence of verapamil showed that thiopental could not induce any Ca(2+) influx with or without phenylephrine prestimulation. The (45)Ca(2+) efflux experiment showed more evidence of thiopental-induced Ca(2+) release, which was abolished by thapsigargin. In conclusion, thiopental induces contraction in rat aortic smooth muscle by releasing Ca(2+) from the sarcoplasmic reticulum without Ca(2+) influx. IMPLICATIONS: This is the first study providing evidence that thiopental-induced vascular contraction is caused by Ca(2+) release from the sarcoplasmic reticulum of the smooth muscle.

Bioactive polymethyl methacrylate-based bone cement: comparison of glass beads, apatite- and wollastonite-containing glass-ceramic, and hydroxyapatite fillers on mechanical and biological properties.

A new bioactive bone cement (designated GBC) consisting of polymethyl methacrylate (PMMA) as an organic matrix and bioactive glass beads as an inorganic filler has been developed. The bioactive beads, consisting of MgO-CaO-SiO(2)-P(2)O(5)-CaF(2) glass, have been newly designed, and a novel PMMA powder was selected. The purpose of the present study was to compare this new bone cement GBC's mechanical properties in vitro and its osteoconductivity in vivo with cements consisting of the same matrix as GBC and either apatite- and wollastonite-containing glass-ceramic (AW-GC) powder (designated AWC) or sintered hydroxyapatite (HA) powder (HAC). Each filler added to the cements amounted to 70 wt %. The bending strength of GBC was significantly higher than that of AWC and HAC (p < 0.0001). Cements were packed into intramedullar canals of rat tibiae in order to evaluate osteoconductivity as determined by an affinity index. Rats were sacrificed at 2, 4, and 8 weeks after operation. An affinity index, which equaled the length of bone in direct contact with the cement expressed as a percentage of the total length of the cement surface, was calculated for each cement. At each time interval studied, GBC showed a significantly higher affinity index than AWC or HAC up to 8 weeks after implantation (p < 0.03). The value for GBC increased significantly with time up to 8 weeks (p < 0.006). The handling property of GBC was comparable with that of PMMA bone cement. Our study revealed that the higher osteoconductivity of GBC was due to the higher bioactivity of the bioactive glass beads at the cement surface and the lower solubility of the new PMMA powder to MMA monomer. In addition, it was found that the smaller spherical shape and glassy phase of the glass beads gave GBC strong enough mechanical properties to be useful under weight-bearing conditions. GBC shows promise as an alternative with improved properties to the conventionally used PMMA bone cement.

Bioactive bone cement: effect of surface curing properties on bone-bonding strength.

The fact that bisphenol-a-glycidyl methacrylate (bis-GMA)-based cements contain an uncured surface is believed to play an important role when determining the surface curing properties of the cements. Therefore, in the present study, the bone-bonding strength of cement plates having an uncured surface on one side and a cured surface on the other side has been evaluated. These cement plates were composites of a bis-GMA-based resin with either an apatite- and wollastonite-containing glass-ceramic (AW-GC) powder or a hydroxyapatite (HA) powder, respectively designated AWC and HAC. The amount of each of these powders in a composite cement was 70 wt %. We formulate the hypothesis that the uncured surface of a cement plate is bioactive having bone-bonding properties. The goal of the present study was to indicate the bone-bonding strength of the uncured surfaces of AWC and HAC and compare the strength with the respective cured surfaces by a detaching in vivo test, as well as to histologically examine the bone-cement interface. Each plate has been implanted into the tibiae of male Japanese white rabbits, taking care to retain the surface properties, and the so-called "failure load has been measured using a detaching test followed 8 weeks after implantation. The failure load for AWC-plates at the uncured surface (2.05 +/- 1.11 kgf, n = 8) was significantly higher than AWC at its cured surface side (0.28 +/- 0.64 kgf, n = 8). The failure load for HAC-plates at the uncured surfaces (1.40 +/- 0.68 kgf, n = 8) was significantly higher than HAC at its cured surface (0.00 +/- 0.00 kgf, n = 8). Failure loads for AWC at its uncured and cured surfaces were both higher than for HAC, although not significantly. Direct bone formation has been observed histologically for both AWC and HAC on the uncured surfaces, and a Ca-P-rich layer was observed only at the uncured surface of AWC. These findings strongly suggest that uncured surfaces are useful for exposing a bioactive filler on a surface of composites, being very effective in inducing bone bonding.

Bone-bonding ability of bioactive bone cement under mechanical stress.

Bioactive bone cement (BABC) is able to bond to bone through a Ca-P rich layer. It was evaluated so far in a rat tibial model, where no mechanical stresses are supposed to take place. The objective is to investigate the behavior of BABC in the environment of posterolateral spinal fixation model, in which the bone cement interface is exposed to continuous mechanical stress. Japanese white rabbits were used. Fixation of L5-L6 segment was done by wiring the spinous and transverse processes of L5 and L6 vertebrae. Then BABC was applied over the transverse processes and the intertransverse process membrane on both sides. Polymethylmethacrylate (PMMA) bone cement was used similarly in the control group. Animals were sacrificed after 1 day, 4, 8, and 16 weeks postoperatively. Bone cement interface was examined using Giemsa surface staining and SEM, and affinity index was measured. Biomechanical testing was done nondestructively in right and left torsion. BABC bonded to bone directly with no intervening soft tissue at 4, 8, and 16 weeks, while soft tissue was consistently seen between PMMA bone cement and bone. BABC-spine constructs were stiffer than PMMA-spine constructs at all time intervals. BABC bonded directly to bone under mechanical stress and afforded stiffer fixation than PMMA bone cement.

Effect of silane treatment and different resin compositions on biological properties of bioactive bone cement containing apatite-wollastonite glass ceramic powder.

In methylmethacrylate (MMA)-based cements containing bioactive particles, polymethylmetacrylate (PMMA) is known to suppress the bioactivity of Bioglass(R) and apatite-wollastonite glass ceramic (AW-GC). Little is known about the effect of different silane treatment methods on the bioactivity of AW-GC. MMA-based cement plates containing dry silanated AW-GC particles and PMMA particles of different molecular weights (12,000-900,000) were immersed in simulated body fluid (SBF). Cements containing PMMA particles of high molecular weight formed an apatite layer on the surface after 24 h. Using PMMA particles with a molecular weight of 60,000 and AW-GC particles silanated with different methods (dry method vs. slurry method), cement plates were made and immersed in SBF. Only cement plates containing dry silanated AW-GC particles showed apatite formation in SBF after 3 days. In vivo implantation in rat tibias of MMA-based cement containing dry silanated AW-GC particles and PMMA particles (molecular weight 900,000) demonstrated an affinity index of 32.1 +/- 15.8% after 8 weeks of implantation compared to 89.4 +/- 10.7% achieved by bisphenol-A-glycidyl methacrylate based cement containing the same bioactive powder. By using a dry method of silane treatment and high molecular weight PMMA particles, the bioactivity of cement based on MMA monomer was achieved; but further effort is needed to improve the mechanical properties of the composite.

Effect of bioactive filler content on mechanical properties and osteoconductivity of bioactive bone cement.

We took three types of bioactive bone cement (designated AWC, HAC, and TCPC), each with a different bioactive filler, and evaluated the influence of each filler on the mechanical properties and osteoconductivity of the cement. The cements consisted of bisphenol-a-glycidyl methacrylate-based (Bis-GMA based) monomers as an organic matrix, with a bioactive filler of apatite/wollastonite containing glass-ceramic (AW-GC) or sintered hydroxyapatite (HA) or beta-tricalcium phosphate (beta-TCP) powder. Each filler was mixed with the monomers in proportions of 50, 70, and 80% (w/w), giving a total of nine cement subgroups. The nine subgroups were designated AWC50, AWC70, AWC80, HAC50, HAC70, HAC80, TCPC50, TCPC70, and TCPC80. The compressive and bending strengths of AWC were found to be higher than those of HAC and TCPC for all bioactive filler contents. We also evaluated the cements in vivo by packing them into the intramedullary canals of rat tibiae. To compare the osteoconductivity of the cements, an affinity index was calculated for each cement; it equaled the length of bone in direct apposition to the cement, expressed as a percentage of the total length of the cement surface. Microradiographic examination up to 26 weeks after implantation revealed that AWC showed a higher affinity index than HAC and TCPC for each filler content although the affinity indices of all nine subgroups (especially the AWC and HAC subgroups) increased with time. New bone had formed along the AWC surface within 4 weeks, even in the cement containing AW-GC filler at only 50% (w/w); observation of the cement-bone interfaces using a scanning electron microscope showed that all the cements had directly contacted the bone. At 4 weeks the AWC had bonded to the bone via a 10 micron-thick reactive layer; the width of the layer, in which partly degraded AW-GC particles were seen, became slightly thicker with time. On the other hand, in the HAC- and TCPC-implanted tibiae, some particles on the cement surface were surrounded by new bone and partly absorbed or degraded. The results suggest that the stronger bonding between the inorganic filler and the organic matrix in the AWC cements gave them better mechanical properties. The results also indicate that the higher osteoconductivity of AWC was caused by the higher reactivity of the AW-GC powder on the cement surface.

Osteoconductivity and bone-bonding strength of high- and low-viscous bioactive bone cements.

A study was conducted to evaluate the osteoconductivity and bone-bonding ability of two types of bioactive bone cement, both consisting of apatite and wollastonite containing glass-ceramic powder (AW-P), fused silica glass powder (SG-P), submicron fumed silica as an inorganic filler, and bisphenol-a-glycidyl methacrylate (Bis-GMA) based resin as an organic matrix. The cements had two kinds of formulas: one (dough-type cement; designated DTC) composed of 85% (w/w) filler and 15% resin, which was developed for fixation of the acetabular component in total hip arthroplasty and could be handled manually; and one (injection-type cement; designated ITC) composed of 79% (w/w) filler and 21% resin. ITC was developed for fixation of the femoral component and, because it had a lower viscosity than DTC, could be injected. The DTC and ITC both contained 73% AW-P, 25% SG-P, and 2% fumed silica in the weight ratio of the filler component. Two other types of cement, both of which consisted of 83.3% AW-P or SG-P, 1.7% fumed silica, and 15% resin, were used as reference material (designated AWC or SGC) for a detaching test. Following the packing of bone defects in the rat tibiae with either DTC or ITC, histological examination revealed that the DTC and ITC had both directly contacted the bone and were almost completely surrounded by bone by 16 weeks after the surgery and that no marked biodegradation had occurred at 52 weeks postimplantation. Rectangular plates (2 x 10 x 15 mm) of AWC, DTC, ITC, and SGC were implanted into the metaphysis of the tibia of male rabbits and the failure load was measured by a detaching test at 10 and 25 weeks after implantation. The failure loads of AWC, DTC, ITC, and SGC were 3.65, 2.21, 2.44, and 0.04 kgf at 10 weeks and 4.87, 2. 81, 2.82, and 0.13 kgf at 25 weeks, respectively. Observation of the bone-implant interface by scanning electron microscopy and energy dispersive X-ray microanalysis revealed that all the samples except SGC formed direct contact with the bone and that only AWC-implanted tibiae had a layer of a low calcium and phosphorus level at the bone-implant interface. Results showed that DTC and ITC have excellent osteoconductivity and bone-bonding ability under non-weight-bearing conditions.