Cardiopulmonary bypass surgical techniques that allow a surgeon to operate on the infant's heart ... more Cardiopulmonary bypass surgical techniques that allow a surgeon to operate on the infant's heart use an extracorporeal circuit consisting of a pump, oxygenator, arterial and venous reservoirs, cannulae, an arterial filter, and tubing. The extracorporeal technique currently used in infants and neonates is sometimes associated with neurologic damage. We are developing a modified cardiopulmonary bypass system for neonates that has been tested in vitro and in one animal in vivo. Unlike other extracorporeal circuits which use steady flo w, this system utilizes pulsatile flo w, a low prime volume (500ml) and a closed circuit. During in vitro experiments, the pseudo patient's mean arterial pressure was kept constant at 40 mmHg and the extracorporeal circuit pressure did not exceed a mean pressure of 200 mmHg. In our single in vivo experiment, the pr imary objective was to determine whether physiologic pulsatility with a 10F (3.3 mm) aortic cannula could be achieved. The results suggest that this is possible.
Eleven goats (mean weight, 69 +/- 16 kg) underwent 5 hrs of normothermic nonpulsatile cardiopulmo... more Eleven goats (mean weight, 69 +/- 16 kg) underwent 5 hrs of normothermic nonpulsatile cardiopulmonary bypass (CPB) using as priming fluid either a Ringer's based crystalloid priming solution (CP, n = 5) of a hyperosmolar oxyreplete hemosubstitute (HS, n = 6). The HS contained 20% w/v perfluorocarbon (perfluorodecalin), its osmolarity was 800-900 mOsm/1, and the administered dose of perfluorocarbon was 30-50 ml/kg. Otherwise, the experimental procedure was identical for both groups. PaCO2 was maintained above 35 mmHg and blood flow rate at 65 ml/kg. Brain tissue pH, PO2, and PCO2, cerebral blood flow (CBF), arterial and venous blood gases, and other systemic variables were monitored. During CPB, PVO2 and brain tissue PO2 were increased significantly in the HS group. The CBF per kilogram of weight also was significantly higher in the HS group. Metabolic acidosis developed in both groups and, surprisingly, brain tissue pH and pHV were lower in the HS group. The mean values of PVCO2 and brain tissue PCO2 indicate that brain tissue hypercapnia also occurred in both groups. The HS provided long-term stability and compatibility with electrolytes, and did not cause major complications or allergic reactions during CPB. Perfluorocarbon based HSs improve tissue oxygenation, eliminate the risk of infection due to homologous transfusions, do not require blood type matching, have a shelf life longer than that of blood, and, therefore, they can be an important factor in diminishing the incidence of complications after CPB.
An idealized plated bone model was used to test the hypothesis that selected screw removal could ... more An idealized plated bone model was used to test the hypothesis that selected screw removal could alter the bone strain field and be a viable treatment for stress protection osteoporosis. Eighteen bone screw modifications were evaluated for their effects on bone strain. The three variables studied were number, position, and length of screws. Removal of two or four bone screws from an eight hole plate significantly increased the strain per load on the bone model over the values with eight screws in the plate (p less than 0.05). The four screw configurations increased bone strain more than the six screw configurations. It also was shown that the position of screws in the plate could significantly alter the bone strain per load results. Removal of six bone screws from an eight hole plate also increased the bone strain per load, but to excess in some tests. In those configurations, the results were not statistically different from the unplated configuration. Replacement of the full length screws with eight half length screws that engaged only the near cortex significantly reduced bone strain per load as compared with eight bicortical bone screws.
Background. The purpose of this study was to evaluate the ability of Harmonic energy technology t... more Background. The purpose of this study was to evaluate the ability of Harmonic energy technology to transect and seal the pancreatic duct compared with the standard monopolar electrosurgery transection and oversew technique in a porcine distal pancreatectomy survival model. Harmonic energy technology is as effective as standard oversew technique for preventing pancreatic leak after distal pancreatectomy.
This study characterizes the healing response of the glenoid after spherical reaming and prosthet... more This study characterizes the healing response of the glenoid after spherical reaming and prosthetic humeral head replacement in a canine model of glenohumeral hemiarthroplasty. The right glenoid of twelve skeletally mature female dogs was reamed to a uniform radius of curvature, removing all cartilage down to bleeding subchondral bone. The glenoid was not resurfaced. The humeral head was replaced with a stemmed metal prosthesis. Post-surgery, the operated limbs were immobilized for seven days, with motion allowed ad libitum thereafter. Fluorescent bone labels were administered to identify bone formation. These procedures were not complicated by instability, infection or death. Six animals were euthanized at 10 week and six more at 24 week. The intact glenohumeral joints were evaluated by gross examination, assessment of glenoid concavity, and light microscopy of methylmethacrylate sections. At 10 week, vascular fibrous tissue partially covered the glenoid, maintaining a concave surface congruent with the prosthetic humeral head. New bone formed at the margin of the glenoid, and the density of the periarticular trabecular bone increased. At 24 week, the healing was more advanced; thick fibrocartilaginous tissue covered the entire glenoid surface.
The use of biodegradable sca!olds for articular cartilage repair has been investigated by numerou... more The use of biodegradable sca!olds for articular cartilage repair has been investigated by numerous researchers. The objective of this screening study was to examine how the mechanical and physical properties of four multiphase implants can a!ect the cartilage healing response. Multiphase implant prototypes were prepared using poly(D,L)lactide-co-glycolide as the base material. PGA "bers (FR), 45S5 Bioglass (BG) and medical grade calcium sulfate (MGCS) were used as additives to vary sti!ness and chemical properties. Osteochondral defects (3 mm dia. and 4 mm in depth) were created bilaterally in the medial femoral condyle (high-weight bearing) and the distal medial portion of the patellar groove (low-weight bearing) of 16 Spanish goats. Half of the implants were loaded with autologous costochondral chondrocytes. Defect sites (total n"64, 4 sites/treatment) were randomly treated and allowed to heal for 16 weeks, fully weight bearing. At euthanasia, gross evaluations and biomechanical testing were conducted. Histological sections of the defect sites were stained with H and E, Safranin O/Fast Green or processed to analyze collagen architecture. Sections were semi-quantitatively scored for repair tissue structure. Qualitative evaluations showed that all groups had a high percentage of hyaline cartilage and good bony restoration, with new tissue integrating well with the native cartilage. Gross and histology scoring indicated a signi"cantly higher score for defect healing in the condyle than in the patellar groove, but no di!erence in healing for implant types or addition/omission of cells was found. This investigation demonstrates that focal, osteochondral defects in caprine distal femurs treated with various implant constructs were repaired with hyaline-like cartilage and good underlying bone. The multiphase implants show potential for treatment of osteochondral defects and long-term studies need to be undertaken to con"rm the longevity of the regenerated tissue.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 1998
We evaluated radiolabeled liposomes (liposomes labeled both with 99mTc and 111In) for the early d... more We evaluated radiolabeled liposomes (liposomes labeled both with 99mTc and 111In) for the early detection of osteomyelitis in an experimental model. Liposomes, containing 5% polyethylene glycol-distearoyl phosphatidylethanolamine with encapsulated glutathione and deferoxamine, were prepared and labeled with 99mTc and 111In by a previously described method. Acute osteomyelitis was induced in male New Zealand rabbits by intramedullary injection of sodium-morrhuate and Staphylococcus aureus in the tibial bone marrow. Serial imaging studies, consisting of radiolabeled liposome imaging (2-4 mCi 99mTc and 75-125 microCi 111In), 99mTc-methylene diphosphonate (MDP) (3-5 mCi) and 67Ga-citrate (500 microCi), were performed starting at the third day after injection. Each radionuclide study was separated by at least 2 days. The animals also underwent radiography of the lower extremities. The animals were then killed and the infected tibia was excised for histopathology. For interpreting relativ...
An extracorporeal pulsatile heart pump has been modified to render biventricular cardiac support ... more An extracorporeal pulsatile heart pump has been modified to render biventricular cardiac support while maintaining automatic volume balance between the left and right sides. The device consists of two independent fluid circuits, externally valved and compressed by a common pusher plate configuration. Because the pusher plate compresses both circuits simultaneously, the volume-heavy side is unloaded via larger stroke volumes until the two sides achieve a balanced stroke volume. The process is automatic from beat-to-beat and is not dependent upon external pressure or flow transducers to maintain equilibrium. Two in vivo studies in pigs weighing 25 kg have demonstrated the feasibility of the concept, with physiologic aortic and pulmonary artery flow during 2 hr of ac-induced ventricular fibrillation and oscillatory ventilator support via left atrium-to-aorta and right atrium-to-pulmonary artery cannulation. Efforts to scale up to human adult size requirements have resulted in in vitro outputs of up to 7.0 L/min in each circuit.
Cardiopulmonary bypass surgical techniques that allow a surgeon to operate on the infant's heart ... more Cardiopulmonary bypass surgical techniques that allow a surgeon to operate on the infant's heart use an extracorporeal circuit consisting of a pump, oxygenator, arterial and venous reservoirs, cannulae, an arterial filter, and tubing. The extracorporeal technique currently used in infants and neonates is sometimes associated with neurologic damage. We are developing a modified cardiopulmonary bypass system for neonates that has been tested in vitro and in one animal in vivo. Unlike other extracorporeal circuits which use steady flo w, this system utilizes pulsatile flo w, a low prime volume (500ml) and a closed circuit. During in vitro experiments, the pseudo patient's mean arterial pressure was kept constant at 40 mmHg and the extracorporeal circuit pressure did not exceed a mean pressure of 200 mmHg. In our single in vivo experiment, the pr imary objective was to determine whether physiologic pulsatility with a 10F (3.3 mm) aortic cannula could be achieved. The results suggest that this is possible.
Eleven goats (mean weight, 69 +/- 16 kg) underwent 5 hrs of normothermic nonpulsatile cardiopulmo... more Eleven goats (mean weight, 69 +/- 16 kg) underwent 5 hrs of normothermic nonpulsatile cardiopulmonary bypass (CPB) using as priming fluid either a Ringer's based crystalloid priming solution (CP, n = 5) of a hyperosmolar oxyreplete hemosubstitute (HS, n = 6). The HS contained 20% w/v perfluorocarbon (perfluorodecalin), its osmolarity was 800-900 mOsm/1, and the administered dose of perfluorocarbon was 30-50 ml/kg. Otherwise, the experimental procedure was identical for both groups. PaCO2 was maintained above 35 mmHg and blood flow rate at 65 ml/kg. Brain tissue pH, PO2, and PCO2, cerebral blood flow (CBF), arterial and venous blood gases, and other systemic variables were monitored. During CPB, PVO2 and brain tissue PO2 were increased significantly in the HS group. The CBF per kilogram of weight also was significantly higher in the HS group. Metabolic acidosis developed in both groups and, surprisingly, brain tissue pH and pHV were lower in the HS group. The mean values of PVCO2 and brain tissue PCO2 indicate that brain tissue hypercapnia also occurred in both groups. The HS provided long-term stability and compatibility with electrolytes, and did not cause major complications or allergic reactions during CPB. Perfluorocarbon based HSs improve tissue oxygenation, eliminate the risk of infection due to homologous transfusions, do not require blood type matching, have a shelf life longer than that of blood, and, therefore, they can be an important factor in diminishing the incidence of complications after CPB.
An idealized plated bone model was used to test the hypothesis that selected screw removal could ... more An idealized plated bone model was used to test the hypothesis that selected screw removal could alter the bone strain field and be a viable treatment for stress protection osteoporosis. Eighteen bone screw modifications were evaluated for their effects on bone strain. The three variables studied were number, position, and length of screws. Removal of two or four bone screws from an eight hole plate significantly increased the strain per load on the bone model over the values with eight screws in the plate (p less than 0.05). The four screw configurations increased bone strain more than the six screw configurations. It also was shown that the position of screws in the plate could significantly alter the bone strain per load results. Removal of six bone screws from an eight hole plate also increased the bone strain per load, but to excess in some tests. In those configurations, the results were not statistically different from the unplated configuration. Replacement of the full length screws with eight half length screws that engaged only the near cortex significantly reduced bone strain per load as compared with eight bicortical bone screws.
Background. The purpose of this study was to evaluate the ability of Harmonic energy technology t... more Background. The purpose of this study was to evaluate the ability of Harmonic energy technology to transect and seal the pancreatic duct compared with the standard monopolar electrosurgery transection and oversew technique in a porcine distal pancreatectomy survival model. Harmonic energy technology is as effective as standard oversew technique for preventing pancreatic leak after distal pancreatectomy.
This study characterizes the healing response of the glenoid after spherical reaming and prosthet... more This study characterizes the healing response of the glenoid after spherical reaming and prosthetic humeral head replacement in a canine model of glenohumeral hemiarthroplasty. The right glenoid of twelve skeletally mature female dogs was reamed to a uniform radius of curvature, removing all cartilage down to bleeding subchondral bone. The glenoid was not resurfaced. The humeral head was replaced with a stemmed metal prosthesis. Post-surgery, the operated limbs were immobilized for seven days, with motion allowed ad libitum thereafter. Fluorescent bone labels were administered to identify bone formation. These procedures were not complicated by instability, infection or death. Six animals were euthanized at 10 week and six more at 24 week. The intact glenohumeral joints were evaluated by gross examination, assessment of glenoid concavity, and light microscopy of methylmethacrylate sections. At 10 week, vascular fibrous tissue partially covered the glenoid, maintaining a concave surface congruent with the prosthetic humeral head. New bone formed at the margin of the glenoid, and the density of the periarticular trabecular bone increased. At 24 week, the healing was more advanced; thick fibrocartilaginous tissue covered the entire glenoid surface.
The use of biodegradable sca!olds for articular cartilage repair has been investigated by numerou... more The use of biodegradable sca!olds for articular cartilage repair has been investigated by numerous researchers. The objective of this screening study was to examine how the mechanical and physical properties of four multiphase implants can a!ect the cartilage healing response. Multiphase implant prototypes were prepared using poly(D,L)lactide-co-glycolide as the base material. PGA "bers (FR), 45S5 Bioglass (BG) and medical grade calcium sulfate (MGCS) were used as additives to vary sti!ness and chemical properties. Osteochondral defects (3 mm dia. and 4 mm in depth) were created bilaterally in the medial femoral condyle (high-weight bearing) and the distal medial portion of the patellar groove (low-weight bearing) of 16 Spanish goats. Half of the implants were loaded with autologous costochondral chondrocytes. Defect sites (total n"64, 4 sites/treatment) were randomly treated and allowed to heal for 16 weeks, fully weight bearing. At euthanasia, gross evaluations and biomechanical testing were conducted. Histological sections of the defect sites were stained with H and E, Safranin O/Fast Green or processed to analyze collagen architecture. Sections were semi-quantitatively scored for repair tissue structure. Qualitative evaluations showed that all groups had a high percentage of hyaline cartilage and good bony restoration, with new tissue integrating well with the native cartilage. Gross and histology scoring indicated a signi"cantly higher score for defect healing in the condyle than in the patellar groove, but no di!erence in healing for implant types or addition/omission of cells was found. This investigation demonstrates that focal, osteochondral defects in caprine distal femurs treated with various implant constructs were repaired with hyaline-like cartilage and good underlying bone. The multiphase implants show potential for treatment of osteochondral defects and long-term studies need to be undertaken to con"rm the longevity of the regenerated tissue.
Journal of nuclear medicine : official publication, Society of Nuclear Medicine, 1998
We evaluated radiolabeled liposomes (liposomes labeled both with 99mTc and 111In) for the early d... more We evaluated radiolabeled liposomes (liposomes labeled both with 99mTc and 111In) for the early detection of osteomyelitis in an experimental model. Liposomes, containing 5% polyethylene glycol-distearoyl phosphatidylethanolamine with encapsulated glutathione and deferoxamine, were prepared and labeled with 99mTc and 111In by a previously described method. Acute osteomyelitis was induced in male New Zealand rabbits by intramedullary injection of sodium-morrhuate and Staphylococcus aureus in the tibial bone marrow. Serial imaging studies, consisting of radiolabeled liposome imaging (2-4 mCi 99mTc and 75-125 microCi 111In), 99mTc-methylene diphosphonate (MDP) (3-5 mCi) and 67Ga-citrate (500 microCi), were performed starting at the third day after injection. Each radionuclide study was separated by at least 2 days. The animals also underwent radiography of the lower extremities. The animals were then killed and the infected tibia was excised for histopathology. For interpreting relativ...
An extracorporeal pulsatile heart pump has been modified to render biventricular cardiac support ... more An extracorporeal pulsatile heart pump has been modified to render biventricular cardiac support while maintaining automatic volume balance between the left and right sides. The device consists of two independent fluid circuits, externally valved and compressed by a common pusher plate configuration. Because the pusher plate compresses both circuits simultaneously, the volume-heavy side is unloaded via larger stroke volumes until the two sides achieve a balanced stroke volume. The process is automatic from beat-to-beat and is not dependent upon external pressure or flow transducers to maintain equilibrium. Two in vivo studies in pigs weighing 25 kg have demonstrated the feasibility of the concept, with physiologic aortic and pulmonary artery flow during 2 hr of ac-induced ventricular fibrillation and oscillatory ventilator support via left atrium-to-aorta and right atrium-to-pulmonary artery cannulation. Efforts to scale up to human adult size requirements have resulted in in vitro outputs of up to 7.0 L/min in each circuit.
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Papers by Donna Korvick