Sino-orbital giant cell reparative granuloma.

An otherwise healthy, 9-year-old boy had gradual onset of a mass deformity in the region of the left medial canthus with resulting superior and lateral globe displacement. Radiographic evaluation demonstrated an osteolytic, expansile lesion involving the bones of the ethmoid and maxillary sinuses. Combined anterior orbitotomy and nasal endoscopic surgical resection revealed additional involvement of the nasolacrimal sac wall. Histopathology was consistent with a giant cell reparative granuloma. The authors know of 15 case reports of sino-orbital giant cell reparative granulomas with ophthalmic manifestations; only 3 of these appeared in the ophthalmology literature. This case appears unique in that extension of the abnormal tissue into the nasolacrimal sac wall was demonstrated.

A model of the volumetrically-controlled hemodialysis circuit.

We developed a model that predicts the hemodynamics of the volumetrically-controlled circuit used to administer high flux hemodialysis. The equations simulate the entire blood side of the circuit so that blood and dialysate pressures can be predicted from a knowledge of circuit component and patient characteristics. An alternative method of computation has also been devised which permits measured circuit pressures to be used to predict patient blood access pressure, dialyzer resistance to flow and membrane hydraulic conductivity. Success of the model was evaluated by measuring both circuit pressure and component characteristics. The model successfully predicted circuit pressures when measured component characteristics were employed as model inputs. Conversely, the model accurately predicted circuit component characteristics when measured pressures were employed as inputs (8 patients, 30 dialyses). Specific predictions of the model include the following. Elevations of patient blood access pressure will cause blood and dialysate pressures to rise equivalently without affecting the rate of back-filtration or location of pressure equilibrium along the dialyzer axis. Elevated hematocrit is predicted to increase circuit pressures to a degree that is similar to a poorly functioning blood access, however, high hematocrit markedly augments back-filtration and moves the point of pressure equilibrium toward the dialyzer entrance. We conclude that the model provides a predictive tool that can be used to optimize circuit design. Alternatively, the model can be used to separate the influence of a poorly functioning patient access from other factors which can elevate circuit pressures.

An in vivo analysis of reverse ultrafiltration during high-flux and high-efficiency dialysis.

We have developed an in vivo pressure monitoring system to study the phenomenon of reverse ultrafiltration of dialysate during high-flux and high-efficiency dialysis. Under the usual operating conditions of either type of dialysis, driving pressures existed for reverse ultrafiltration of dialysate into the venous end of the blood compartment. Whether or not reverse ultrafiltration could be abolished at higher ultrafiltration rates was dialyzer-dependent, being least with high-efficiency dialysis. In addition, the degree of reverse ultrafiltration was affected by patients hematocrit, dialyzer inlet and outlet oncotic pressures, and the rate and direction of dialysate flow.