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Biomedical subjects

Akif Undar

Publications and source records attributed to Akif Undar.

At least 19 recordsLinked to original sources
PubMed2006

A microfluidic device for continuous, real time blood plasma separation.

A microfluidic device for continuous, real time blood plasma separation is introduced. The principle of the blood plasma separation from blood cells is supported by the Zweifach-Fung effect and was experimentally demonstrated using simple microchannels. The blood plasma separation device is composed of a blood inlet, a bifurcating region which leads to a purified plasma outlet, and a concentrated blood cell outlet. It was designed to separate blood plasma from an initial blood sample of up to 45% inlet hematocrit (volume percentage of cells). The microfluidic network was designed using an analogous electrical circuit, as well as analytical and numerical studies. The functionality of this device was demonstrated using defibrinated sheep blood. During 30 minutes of continuous blood infusion through the device, all the erythrocytes (red blood cells) traveled through the device toward the concentrated blood outlet while only the plasma was separated at the bifurcating regions and flowed towards the plasma outlet. The device has been operated continuously without any clogging or hemolysis of cells. The experimentally determined plasma selectivity with respect to blood hematocrit level was almost 100% regardless of the inlet hematocrit. The total plasma separation volume percent varied from 15% to 25% with increasing inlet hematocrit. Due to the device's simple structure and control mechanism, this microdevice is expected to be used for highly efficient continuous, real time cell-free blood plasma separation from blood samples for use in lab on a chip applications.

Fluorescent Dyes↗
PubMed2006

Initial European clinical experience with pulsatile extracorporeal membrane oxygenation.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) for post-cardiotomy heart failure in neonates and infants still carries high mortality and morbidity rates. In this study we present the first European clinical experience with the Medos DeltaStream DP1, a new pulsatile flow pump, in neonates and infants. METHODS: The DP1 is an extracorporeal rotary blood pump. The pump features a diagonal flow impeller, and can be used for both continuous and pulsatile output. Special characteristics include its small priming volume of approximately 30 ml and a high pumping capacity. A temperature sensor and speed sensors are integrated into the pump. The pump has a delivery rate of up to 8 liters/min and a speed range of 100 to 10,000 rpm. RESULTS: Two patients being assisted with the pulsatile pump system were successfully weaned after 36 and 53 hours, respectively. CONCLUSIONS: Based on our limited experience with 2 patients, we believe that pulsatile DP1 device is a reasonable alternative to current conventional non-pulsatile systems.

Cardiac Surgical Procedures↗
PubMed2006

Transcutaneous near-infrared spectroscopy for detection of regional spinal ischemia during intercostal artery ligation: preliminary experimental results.

OBJECTIVE: Real-time information about regional spinal cord ischemia can guide intraoperative management and reduce the risk of paraplegia after thoracic aortic surgery. We hypothesized that near-infrared spectroscopy could provide such information during intercostal and lumbar artery ligation in pigs. METHODS: Transcutaneous near-infrared spectroscopic sensors were placed in the midline over the upper and lower thoracic vertebrae of 4 progressively larger pigs (weight range 21-70 kg). After the entire aorta was exposed, segmental arteries from T6 through L1 were sequentially ligated while regional oxygen saturation was monitored. Decreases in regional oxygen saturation were calculated as percentage changes from baseline. The degrees of ischemia in the upper and lower spinal cord were compared histopathologically. RESULTS: Baseline regional oxygen saturations were similar in the upper (68.8% +/- 9.0%) and lower (68.0% +/- 11.5%, P = .82) cord. After ligation, however, regional oxygen saturation levels were significantly lower in the lower cord (41.3% +/- 10.1%) than in the upper cord (64.8% +/- 9.3%, P = .037). The regional oxygen saturation had decreased by 39.0% +/- 11.5% in the lower cord but only by 6.3% +/- 7.6% in the upper cord (P = .026). This difference was confirmed microscopically: upper-cord sections had fewer ischemic neurons (8.8 +/- 9.4) than did lower-cord sections (21.3 +/- 13.6, P = .002). CONCLUSION: Intraoperative spinal cord ischemia was detectable with near-infrared spectroscopy in pigs weighing as much as 70 kg. The potential utility of this technique in patients undergoing thoracic aortic surgery warrants investigation.

Animals↗
PubMed2005

Comparison of hollow-fiber membrane oxygenators in terms of pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass in neonates.

UNLABELLED: The objective of this study was to investigate the effects of two hollow-fiber membrane oxygenators, the Capiox SX10 and the Lilliput 901, on pressure drop of the membranes during normothermic and hypothermic cardiopulmonary bypass (CPB) in neonates. METHODS: Twenty-six congenital heart surgery patients (n = 13 in each group) with a mean weight of 3 kg were included in this study. Pressure drops of the membranes, pre- and post-oxygenator extracorporeal circuit pressures (ECC) were recorded during normothermic CPB, hypothermic CPB (20 degrees C) and after rewarming. There were no differences between the groups in mean arterial pressure, pump flow rate, temperature, duration of CPB, crossclamp time or the severity of the surgical repairs. RESULTS: Pressure drop of the Capiox SX10 oxygenator was significantly lower during normothermic (32 +/- 10 versus 55 +/- 16 mmHg, p < 0.001), hypothermic (38 +/- 15 versus 72 +/- 18 mmHg, p < 0.001) and post-rewarming (42 +/- 13 versus 72 +/- 21 mmHg, p < 0.001) periods compared to the Lilliput oxygenator. In the Capiox group, the pre-oxygenator ECC pressure was also significantly lower during normothermic CPB (142 +/- 27 versus 184 +/- 43 mmHg, p < 0.01), hypothermic CPB (162 +/- 30 versus 199 +/- 38 mmHg, p < 0.01) and after rewarming periods (172 +/- 32 versus 212 +/- 42 mmHg, p < 0.01). Post-oxygenator pressures in the Capiox group were also lower than in the Lilliput group, but results were not statistically significant. CONCLUSIONS: These results suggest that the Capiox SX10 hollow-fiber membrane oxygenator produced significantly lower membrane pressure drops and pre- and post-oxygenator ECC during normothermic and hypothermic CPB. Thus, blood trauma with the Capiox during extracorporeal circulation may be significantly lower compared to the Lilliput. Further studies, including the level of complements, platelets, neutrophils and cytokines, with these oxygenators are warranted.

Blood Flow Velocity↗
PubMed2004

Comparison of pulsatile and non-pulsatile cardiopulmonary bypass in patients with chronic obstructive pulmonary disease.

BACKGROUND: Patients with chronic obstructive pulmonary disease have an increased risk of mortality and morbidity after open-heart surgery. This is mostly due to a dysfunction of the pulmonary system during and after non-pulsatile cardiopulmonary bypass. The purpose of this study was to compare the pulsatile and non-pulsatile blood flows during cardiopulmonary bypass in patients with chronic obstructive pulmonary disease. MATERIAL/METHODS: This is a prospective study. Ten patients with chronic obstructive pulmonary disease had open-heart surgery with pulsatile flow, and another 9 patients with non-pulsatile flow. We compared clinical, hemodynamic, biochemical and hematological parameters and arterial and venous blood gases before initiating cardiopulmonary bypass, at aortic cross-clamping and de-clamping, and 1 and 24 hours postoperative. RESULTS: In the pulsatile flow group, systemic vascular resistance at the time of aortic cross clamping (p=0.041), pulmonary vascular resistance 1 hour postoperative (p=0.05), and the percentage of neutrophils 1 hour postoperative (p=0.034) were significantly lower than those of the non-pulsatile group. Though white blood cell count was significantly high in the pulsatile group 1 hour postoperative, absolute neutrophil count was significantly low (p=0.034). The postoperative mechanical ventilation period was significantly shorter in the pulsatile flow group (p=0.016). CONCLUSIONS: Pulsatile blood flow during cardiopulmonary bypass has a favorable influence on patients with chronic obstructive pulmonary disease, who have high risk in open-heart surgery.

Blood Gas Analysis↗
PubMed2004

Anesthetic induction with ketamine inhibits platelet activation before, during, and after cardiopulmonary bypass in baboons.

The objective of this study was to investigate the effects of antifactor D monoclonal antibody (Mab) 166-32 on platelet activation during and after hypothermic cardiopulmonary bypass (CPB) in baboons. Fourteen baboons (mean weight, 15 kg) underwent hypothermic CPB. Seven of them were treated with a single injection of antifactor D Mab 166-32 (5 mg/kg) and the other seven animals were given saline as control. Each baboon was sedated with an intramuscular injection of 10 mg/kg of ketamine hydrochloride. A 20-gauge angiocatheter was placed in the cephalic vein, and 5 mg of diazepam was administered intravenously. Anesthesia was maintained with 0.80% to 2.25% isoflurane, 100% O2, and an inspiratory tidal volume of 13 mL/kg at a rate of 13 breaths per minute throughout the surgical procedure except during CPB. Pancuronium bromide, 0.1 mg/kg, was administered to achieve adequate muscle paralysis. Blood samples were collected before CPB, during CPB, and 1, 2, 3, and 6 h after CPB. Assays were performed to measure platelet activation [CD62P (P-selectin)] using immunofluorocytometric methods. There were no significant differences on CD62P expression of platelets between control and antibody groups before CPB (105 +/- 12% vs. 99 +/- 8%, P=NS), during normothermic CPB (62 +/- 6% vs. 63 +/- 19%, P=NS), during hypothermic CPB (55 +/- 8% vs. 54 +/- 13%, P=NS), and 1, 3, or 6 h after CPB (74 +/- 20% vs. 81 +/- 11%, P=NS). Anesthetic induction with ketamine caused significant reduction in the platelet activation in both groups. Ketamine did not affect complement, neutrophil, and monocyte activation or cytokine production. Further studies on the mechanisms of platelet inhibition by ketamine are warranted.

Analysis of Variance↗
PubMed2004

Outcomes of congenital heart surgery patients after extracorporeal life support at Texas Children's Hospital.

The objective of this study was to investigate the outcomes of children with heart failure of various etiologies requiring temporary use of currently available technology in the U.S.A. after extracorporeal life support (ECLS) [left ventricular assist device (LVAD) or extracorporeal membrane oxygenation (ECMO)] at Texas Children's Hospital. Between July of 1995 and October of 2002, 2847 patients underwent congenital heart surgical repairs with the aid of cardiopulmonary bypass at Texas Children's Hospital. During this period, 17 patients required chronic mechanical circulatory assistance with Biomedicus centrifugal pump (n=8) or Thoratec LVAD (n=4), and ECMO (n=5). Six out of 17 patients required ECLS for postcardiotomy heart failure. Seven of the 17 patients had congenital heart disease, six had cardiomyopathy, three had late acute rejection following heart transplantation, and one had myocardial infarction. Twelve patients survived and five patients expired. Six of 12 survivors recovered sufficient cardiac function to allow device removal; and the remaining six patients underwent heart transplantation. Three out of five deaths were ECMO patients. The need for ECLS following repair of congenital heart disease is extremely rare in our institution. The requirement for the use of ECMO confers a significantly higher mortality presumably because of associated combined cardiopulmonary failure. Congenital heart disease appears to be associated with significantly higher mortality.

Adolescent↗
PubMed2003

Use of near-infrared spectroscopy to monitor regional cerebral oxygen saturation during infrarenal aortic crossclamping in piglets.

PURPOSE: The hemodynamic changes induced by infrarenal aortic crossclamping have been well documented, but the effects of such crossclamping on cerebral perfusion are unknown. To investigate these effects, we used near-infrared spectroscopy (NIRS) to monitor regional cerebral oxygen saturation (rSO2) during infrarenal aortic crossclamping in a piglet model. METHODS: The study involved 19 piglets, each weighing 7.8 +/- 1 kg. The NIRS sensor was placed on each animal's forehead. General anesthesia was induced, and the infrarenal abdominal aorta was mobilized through a laparotomy. After heparin (1 mg/kg) was administered, crossclamps were applied proximally and distally. A 2 mm segment was resected from the proximal aortic stump, and an aorto-aortic anastomosis was performed. RESULTS: Crossclamping lasted for 30.6 +/- 6.7 min. Between the time of baseline measurement and clamp application, the rSO2 did not decrease significantly (65.4%+/- 8.9% vs. 62.4%+/- 7.8%). However, significant decreases in the rSO2 occurred between baseline measurement and clamp removal (65.4%+/- 8.9% vs. 55.7%+/- 8.9%; P<0.01), between baseline measurement and the end of surgery (65.4%+/- 8.9% vs. 57.7%+/- 7.5%; P<0.01), and between clamp application and removal (62.4%+/- 7.8% vs. 55.7%+/- 8.9%; P<0.01). At these same intervals, no intergroup differences occurred in the temperature, heart rate, or mean arterial pressure. CONCLUSION: Infrarenal aortic crossclamping significantly decreases the rSO2. NIRS, which has the advantages of being non-invasive and continuous, may be useful for monitoring this variable intraoperatively.

Analysis of Variance↗
PubMed2003

First Turkish experience with the MicroMed DeBakey VAD.

Mechanical bridging to cardiac transplantation with a ventricular assist device may be a life-saving procedure for patients with end-stage heart failure. Here we report our 3 cases of patients implanted with the MicroMed DeBakey VAD (ventricular assist device). Three male patients, aged 37, 41, and 40, had end-stage left heart failure due to idiopathic cardiomyopathy and were listed for cardiac transplantation. They had progressive hemodynamic deterioration. Although Patient 1 underwent surgery, after device implantation, for bowel necrosis caused by thromboemboli of unknown origin, heart transplantation was performed 70 days after implantation. Pump thrombosis occurred in Patient 2 on the 120th day. Outflow graft ligation was performed because the patient refused a pump exchange. This patient died on the 25th day after ligation and the 145th day after ventricular assist device implantation. A heparin-coated version of the device was implanted in Patient 3, whose preoperative profound biventricular failure had been improved by inotropic medication and intra-aortic balloon pump support. Successful heart transplantation was performed 161 days after implantation. These are the 1st implantations of a left ventricular assist device in Turkey. From these cases, we have learned that the DeBakey VAD supplies adequate blood flow during the bridging period and, due to its simplicity, portability, and low infection rate, enables discharge of the patient from the hospital. However, preoperative psychological evaluation and postoperative psychological support are important for a successful bridging procedure, as is close observation of coagulation and of pump operation.

Adult↗
PubMed2002

BioGlue surgical adhesive impairs aortic growth and causes anastomotic strictures.

BACKGROUND: BioGlue surgical adhesive (CryoLife, Inc, Kennesaw, GA) is currently being used to secure hemostasis at cardiovascular anastomoses in adults. Interference with vessel growth would preclude its use during congenital heart surgery. The purpose of this study was to determine if BioGlue reinforcement of aortic anastomoses impairs vessel growth and causes strictures. METHODS: Ten 4-week-old piglets (8.0 +/- 1.4 kg) underwent primary aorto-aortic anastomoses. Five piglets were randomly assigned to anastomotic reinforcement with BioGlue. After a 7-week growth period, the aortas were excised for morphometric analysis and histopathology. RESULTS: Weight gains were similar in both groups. In BioGlue animals, however, aortic circumference increased only 1.5 +/- 0.8 mm (versus 2.7 +/- 0.8 mm in controls; p = 0.054). BioGlue animals developed a 33.9% stenosis of the aortic lumen area (versus 3.7% in controls, p = 0.038). Adventitial changes reflecting tissue injury and fibrosis were present in all BioGlue animals versus none of the control animals (p = 0.008). CONCLUSIONS: BioGlue reinforcement impairs vascular growth and causes stricture when applied circumferentially around an aorto-aortic anastomosis. This adhesive should not be used on cardiovascular anastomoses in pediatric patients.

Age Factors↗