A high fidelity tissue-based cardiac surgical simulator.

OBJECTIVE: Issues concerning the training and certification of surgical specialists have taken on great significance in the last decade. A realistic computer-assisted, tissue-based simulator developed for use in the training of cardiac surgical residents in the conduct of a variety of cardiac surgical procedures in a low-volume cardiothoracic surgery unit of a typical developing country is described. The simulator can also be used to demonstrate the function of technology specific to cardiac surgical procedures in a way that previously has only been possible via the conduct of a procedure on a live animal or human being. METHODS: A porcine heart in a novel simulated operating theatre environment with real-time simulated haemodynamic monitoring and coronary blood flow, in arrested and beating-heart modes, is used as a training tool for surgical residents. RESULTS: Standard and beating-heart coronary arterial bypass, aortic valve replacement, aortic homograft replacement and pulmonary autograft procedures can be simulated with high degrees of realism and with the superimposition of adverse clinical scenarios requiring valid decision making and clinical judgments to be made by the trainees. CONCLUSIONS: The cardiac surgical simulation preparation described here would appear to be able to contribute positively to the training of residents in low-volume centres, as well as having the potential for application in other settings as a training tool or clinical skills assessment or accreditation device. Collaboration with larger centres is recommended in order to accurately assess the utility of this preparation as an adjunctive cardiothoracic surgical training aid.     

Percutaneous absorption of 2,6-di-tert-butyl-4-nitrophenol (DBNP) in isolated perfused porcine skin.

DBNP (2,6-di-tert-butyl-4-nitrophenol) has been reported as a potential contaminant in submarines. This yellow substance forms when lubrication oil mist containing the antioxidant additive 2,6-di-tert-butylphenol passes through an electrostatic precipitator and is nitrated. Percutaneous absorption of 14C-DBNP was assessed in the isolated perfused porcine skin flap (IPPSF). Four treatments were studied (n=4 flaps/treatment): 40.0 microgram/cm(2) in 100% ethanol; 40.0 microgram/cm(2) in 85% ethanol/15% H(2)O; 4.0 microgram/cm(2) in 100% ethanol; and 4.0 microgram/cm(2) in 85% ethanol/15% water. DBNP absorption was minimal across all treatment groups, with the highest absorption detected being only 1.08% applied dose in an aqueous ethanol group. The highest mass of 14C-DBNP absorbed was only 0.5 microgram. The majority of the applied dose remained on the surface of the skin. This suggests that there is minimal dermal exposure of DBNP when exposed topically to skin.     

Functional Anatomy of Visuomotor Skill Learning in Human Subjects Examined with Positron Emission Tomography

The present study was designed to examine patterns of regional cerebral blood flow (CBF) associated with the learning of a repeated visuomotor sequence both in the early and late phases of the acquisition process. In addition, changes in blood flow related to the implicit versus explicit aspects of learning such a skill were investigated. Fourteen normal control subjects were scanned while performing the task (i) in both early and advanced learning stages of the visuomotor sequence; (ii) after having acquired explicit knowledge of the sequences; and (iii) in two control conditions (perceptual and random sequence). Subtraction of the random condition from the highly learned condition revealed specific areas of activity in the right ventral striatum and dentate nucleus of the cerebellum. Blood flow changes in the right hemisphere were also seen in the medial posterior parietal and prestriate regions, as well as in the anterior cingulate cortex. Finally, once the subjects had acquired explicit knowledge of the embedded sequence that was presented in the highly learned condition, increased CBF activity was observed only in the mid-ventrolateral frontal area in the right hemisphere. These findings confirm that both the striatum and the cerebellum are involved in the implicit acquisition of a visuomotor skill, especially in the advanced stages of the learning process, and furthermore that the ventrolateral prefrontal cortex contributes preferentially to the declarative aspect of this task.     

Evaluation of filling materials in membrane‐protected bone defects. A comparative histomorphometric study in the mandible of miniature pigs.

In recent years, bone grafts and bone substitutes have been increasingly utilized underneath barrier membranes to optimize the treatment outcome of bone reconstructive therapy for defects in the alveolar process. In the present study, 4 different filling materials were evaluated in bone defects of similar dimensions in the mandible of miniature pigs. Blood clots and autografts were used as controls. The defects were covered with barrier membranes and allowed to heal for 4, 12 or 24 weeks. Histologic examination demonstrated that bone repair progressed through a programmed sequence of maturation steps closely resembling the pattern of bone development and growth regardless of whether bone grafts or substitutes were present or not. Histomorphometric analysis showed that autologous bone grafts (autografts) had the best osteoconductive properties during the initial healing period, with 39% of newly formed bone inside the membrane-covered defects at 4 weeks of healing. In addition, 87% of the graft surfaces were already covered by bone at this time. Both values were significantly higher for autografts than for the 4 alternative bone fillers (P < or = 0.05). At 12 weeks, these differences were no longer apparent, with all 5 filling materials showing similar values. Among the tested bone substitutes, tricalcium phosphate (TCP) showed a significantly higher percentage of bone fill at 24 weeks of healing. It can be concluded that sites filled with autografts clearly demonstrated the best results underneath barrier membranes in the early phase of healing. As far as degradation and substitution are concerned, TCP showed the most promising results. This filler, however, needs to be tested further in a more demanding animal model. Less favorable results were obtained for coral-derived hydroxyapatite granules and for demineralized freeze-dried bone allografts.