Transplantation of osteogenic cells with a suitable matrix is one strategy for engineering bone tissue. Three-dimensional distribution and growth of cells within the porous scaffold are of clinical significance for the repair of large bony defects. A nano-HAp/collagen (nHAC) composite that mimics the natural bone both in composition and microstructure to some extent was employed as a matrix for the tissue engineering of bone. A porous nHAC composite was produced in sheet form and convolved to be a three-dimensional scaffold. Using organ culture techniques and the convolving method, we have developed three-dimensional osteogenic cells/nHAC constructs in vitro. Scanning electron microscopic and histological examination has demonstrated the development of the cells/material complex. Spindle-shaped cells migrating out of bone fragments continuously proliferated and migrated throughout the network of the coil. The porous nHAC scaffold provided a microenvironment resembling that seen in vivo, and cells within the composite eventually acquired a tridimensional polygonal shape. In addition, new bone matrix was synthesized at the interface of bone fragments and the composite.

Several types of calcium phosphate/collagen composites, including noncrystalline calcium phosphate/collagen, poorly crystalline carbonate-apatite (PCCA)/collagen, and PCCA + tetracalcium phosphate/collagen composites, were prepared through the mineralization of collagen matrix. The type I collagen was presoaked with a PO(3-)(4) containing solution and then immersed in a Ca(2+) containing solution to allow mineral deposition. The solution of 0.56 M sodium dibasic phosphate (Na(2)HPO(4)) with a pH of nearly 14 was metastable and its crystallization produced Na(2)HPO(4) and sodium tripolyphosphate hexahydrate (Na(5)P(3)O(10)). 6H(2)O), leading to a controlled release of orthophosphate ions during the subsequent mineral precipitation. The development of the composites was investigated in detail. The mineral contributed up to 60-70% of the weight of the final composites. The strength and Young's modulus of the composites in tensile tests overlapped the lower range of values reported for bone. When implanted in muscle tissue, the composite showed biodegradability that was partly through a multinucleated giant cell mediated process. In a bone explant culture model it was observed that bone-derived cells deposited mineralizing collagenous matrix on the composite.

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Background To identify patient and procedural characteristics associated with postoperative respiratory depression or sedation that required naloxone intervention. Methods We identified patients who received naloxone to reverse opioid-induced respiratory depression or sedation within 48 hours after discharge from anesthetic care (transfer from the post anesthesia care unit, or transfer from the operating room to postoperative areas) between July 1, 2008 and June 30, 2010. Patients were matched to two controls based on age, sex, and exact type of procedure performed during the same year. A chart review was performed to identify patient, anesthetic and surgical factors that may be associated with risk for intervention requiring naloxone. In addition, we identified all patients who developed adverse respiratory events [hypoventilation, apnea, oxyhemoglobin desaturation, pain/sedation mismatch] during Phase I anesthesia recovery. We performed conditional logistic regression taking into account the 1:2 matched set case-control study design to assess patient and procedural characteristics associated with naloxone use. Results We identified 134 naloxone administrations, 58% within 12 hours of discharge from anesthesia care, with incidence of 1.6 per 1,000 (95% CI 1.3 – 1.9) anesthetics. Presence of obstructive sleep apnea (odds ratio = 2.45, 95%CI 1.27-4.66, P = 0.008), and diagnosis of adverse respiratory event in postanesthesia recovery room (odds ratio = 5.11, 95%CI 2.32-11.27, P < 0.001) were associated with increased risk for requiring naloxone to treat respiratory depression or sedation following discharge from anesthesia care. Following discharge from anesthesia care, patients administered naloxone used a greater median dose of opioids (10 [interquartile range 0, 47.1] vs. 5 [0, 24.8] intravenous morphine equivalents, P = 0.020) and more medications with sedating side effects (N = 41 [31%] vs. 24 [9%], P<0.001). Conclusion Obstructive sleep apnea and adverse respiratory events in recovery room are harbingers of increased risk for respiratory depression or sedation requiring naloxone after discharge from anesthesia care. Also, patients administered naloxone received more opioids and other sedating medications after discharge from anesthetic care. Our findings suggest that these patients may benefit from more careful monitoring after being discharged from anesthesia care.

The tissue response to a nano-hydroxyapatite/collagen composite implanted in a marrow cavity was investigated by histology and scanning electron microscopy. A Knoop microhardness test was performed to compare the mechanical behavior of the composite and bone. The ultrastructural features of the composite, especially the carbonate-substituted hydroxyapatite with low crystallinity and nanometer size, made it a bone-resembling material. It was bioactive, as well as biodegradable. At the interface of the implant and marrow tissue, solution-mediated dissolution and giant cell mediated resorption led to the degradation of the composite. Interfacial bone formation by osteoblasts was also evident. The process of implant degradation and bone substitution was reminiscent of bone remodeling. The composite can be incorporated into bone metabolism instead of being a permanent implant. For lack of the hierarchical organization similar to that of bone, the composite exhibited an isotropic mechanical behavior. However, the resistance of the composite to localized pressure could reach the lower limit of that of the femur compacta.