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Biomedical subjects

A Gerdes

Publications and source records attributed to A Gerdes.

14 recordsLinked to original sources
PubMed2002

Influence of arteriotomy shape on power losses across in vitro cavopulmonary connections.

BACKGROUND: In the Fontan circulation power supply for maintaining adequate lung perfusion via a total cavopulmonary connection is limited. This study, aiming at the detection of energy consuming variables, compares the influence of two different pulmonary arteriotomy shapes on power losses across cavopulmonary connections. METHODS: Two types of surgical junctions of cavopulmonary connections were studied in a mock circulation. Firstly a slot-shaped incision and secondly an oval-shaped excision within the pulmonary artery was performed. The cross sections of native caval veins were sutured end-to-side with the edges of the incised and excised pulmonary arteries, respectively. Pressures and flows were measured at total flow rates varying from 1200 ml/min to 6000 ml/min and power losses calculated. RESULTS: Power losses were, in dependence of total flow, 10.66-32.64% lower across the oval-shaped junctions if compared to the corresponding slot-shaped junctions (p<0.05). CONCLUSIONS: Surgical junctions including an oval excision within the pulmonary artery may reduce power losses across cavopulmonary connections if compared to simple slot-shaped incisions. These findings may have some influence on surgical techniques to improve hemodynamics of cavopulmonary connections.

Anastomosis, Surgical↗
PubMed2001

Effect of cardiopulmonary bypass on a patient with endocarditis and malaria.

Knowledge about the effects of cardiopulmonary bypass on malarial patients is scant. Malaria-induced hemolysis can exercerbate by performing extracorporeal circulation on a patient infected with Plasmodium and may, therefore, lead to a critical hemolysis jeopardizing the clinical outcome. A 52-year-old patient suffering from malaria and endocarditis was scheduled for urgent aortic valve replacement. During extracorporeal circulation, free hemoglobin showed an increase to maximum of 392.5 mg/L (normal range < 50 mg/L), while haptoglobin decreased to the lowest value of 0.56 g/L (normal range 0.3-2.0 gL). Although hemolysis increased, pump run, weaning, and the postoperative course were uneventful.

Aortic Valve↗
PubMed2000

Hydrodynamics of aortic arch vessels during perfusion through the right subclavian artery.

BACKGROUND: Performing subclavian artery cannulation in patients with an atherosclerotic ascending aorta or acute aortic dissection is of growing interest. To increase knowledge about pressure and flow distribution in the arch vessels, we investigated the in vitro perfusion characteristics in right subclavian artery cannulation. METHODS: Pressures and flow rates in the arch vessels of an aortic arch model were measured during perfusion through the right subclavian artery with different geometries and varying flow rates. Flow visualization was performed by laser light. RESULTS: In normal subclavian artery geometries, pressure and flow showed a significant increase in only the right common carotid artery (8 mm Hg and 25.5 mL/min, respectively, at 5.5 L/min pump flow). In cases of 50% stenosis at the right subclavian artery origin, a reduction of pressure and flow (6 mm Hg and 22.5 mL/min, respectively, at 5.5 L/min pump flow) in the right carotid artery caused by a suction effect was observed. CONCLUSIONS: Right subclavian artery cannulation provides a valuable alternative for ascending aortic cannulation, enabling nearly balanced arch vessel perfusion. Stenosis at the right subclavian artery origin carries the potential risk of slightly reduced perfusion of the right common carotid artery with questionable clinical relevance.

Adult↗
PubMed2000

Prognosis and clinical presentation of BRCA2-associated breast cancer.

54 female breast cancer patients from 22 families with BRCA2 germ line mutations from Sweden and Denmark were compared with 214 age- and date of diagnosis-matched controls identified among breast cancer patients from South Sweden. At diagnosis, BRCA2-associated cases were more often node-positive (N+). OR=1.9 (95% confidence interval (CI)=1.0-3.6; P=0.036), and were more often clinical stage IV: OR=4.6 (95% CI=1.3-17; P=0.021) than the controls. Bilateral disease was also more common among the BRCA2-associated cases: OR=2. 4 (95% CI=1.1-5.3; P=0.027). Breast cancer-specific survival (BCSS) was significantly worse among the BRCA2-associated cases: RR=2.0 (95% CI=1.2-3.4; P=0.010). When stage was corrected for in a multivariate analysis, BCSS was no longer significantly worse for the BRCA2-associated cases: RR=1.6 (95% CI=0.85-3.1). The corresponding effect after correction for bilateral disease was: RR=1.8 (95% CI=1.0-3.1; P=0.034). The unfavourable prognosis in BRCA2-associated breast cancer seems, to a great extent, to be a consequence of the higher clinical stage at diagnosis. The increased presence of bilateral cancers appears to have less impact on survival in this group of hereditary breast cancer. Data presented here needs to be taken into account when counselling healthy carriers of BRCA2 germ line mutations.

Adult↗
PubMed2000

An in vitro evaluation of a new cannula tip design compared with two clinically established cannula-tip designs regarding aortic arch vessel perfusion characteristics.

We investigated in vitro aortic arch vessel perfusion characteristics of single and multiple jet-stream cannulae and a new dispersion stream tip aortic cannula. Pressures and flows of all arch vessels were measured while directing cannulae jets at the different arch vessels using 6 l/min pump flow. The highest increase in pressure above the set systemic level of 80 mmHg and increase in flow above the set normal flow distribution in the arch vessels occurred in the jet-streamed arch vessels with the single stream cannula. The values were as follows: 29 mmHg and 118 ml/min for the innominate artery, 28 mmHg and 42 ml/min for the left common carotid artery, and 25 mmHg and 54 ml/min for the left subclavian artery. The dispersion stream cannula showed increases in pressure and flow, followed by the multiple stream cannula. Aortic cannula tips and the orientation of jets are potential sources of imbalances of arch vessel perfusion with possible clinical implications regarding perfusion of arch vessels during extracorporeal circulation.

Aorta↗
PubMed1999

Addition of a small curvature reduces power losses across total cavopulmonary connections.

BACKGROUND: In the Fontan circulation the vis a tergo for lung perfusion is limited. The hypothesis of this in vitro study was that energy dissipation at the common cavopulmonary connection can be reduced by the addition of caval curvature. METHODS: Two Perspex models were analyzed, the commonly used crosslike cavopulmonary connection (model 1) and a modified curved configuration (model 2). Pressures and flows across the connections were measured simultaneously at various caval and pulmonary artery flow splits and resistances. Mixing of inferior and superior caval fluid was evaluated. RESULTS: Caval pressure oscillations occurred in model 1 only. Curvature reduced power losses in all settings significantly (alpha = 0.05), most successfully at adult caval flow ratios and at high flow rates. At equal pulmonary resistances pulmonary flow was balanced in both models. The inferior caval fluid is preferably directed to the right lung in model 2 predominantly for caval flow conditions in younger patients. CONCLUSIONS: Our data show that the modified curved cavopulmonary connection is hydrodynamically advantageous but might impair caval fluid mixing in younger children.

Age Factors↗
PubMed1999

An in-vitro evaluation of aortic arch vessel perfusion characteristics comparing single versus multiple stream aortic cannulae.

OBJECTIVE: During extracorporeal circulation design and orientation of aortic cannulae tips mainly determine flow pattern in the aortic arch and arch vessels which is the objective of this in vitro study, comparing single versus multiple stream cannulae. METHODS: In an aortic arch glass model, jet streams of 21-24 French aortic cannulae which were inserted in the ascending aorta were directed alternatively at the different arch vessels. Flows and pressures in the arch vessels were measured at pump flows of 3-6 l/min. RESULTS: With optimal orientation of the jet stream in the aortic arch, no preferential flow in the arch vessels was seen. In the single jet stream aortic cannulae group a significant parallel increase in flow and pressure in the jet streamed arch vessels compared to the non-jet streamed arch vessels occurred (P < 0.05). With the jet stream directed on vessel 2 (left carotid vessel) there was a significant pressure and flow difference comparing the two non-jet streamed vessels with each other (P < 0.03). In the single stream 24 French cannulae the highest vessel pressure of 168 mmHg and an increase in flow of 186 ml/min was measured in the jet streamed left carotid artery at 6 l/min pump flow. The multiple stream cannulae provoked the highest vessel pressure of 106 mmHg in the corresponding jet streamed vessel and an increase in flow of 20 ml/min. CONCLUSION: Tip design of aortic cannulae and the orientation of its jet stream are potential sources of remarkable imbalance of arch vessel perfusion especially with single jet stream cannulae. These effects are more pronounced with single jet stream cannulae. These results may have important clinical implications regarding perfusion of arch vessels during extracorporeal circulation.

Aorta, Thoracic↗
PubMed1998

Superior hydrodynamics of a modified cavopulmonary connection for the Norwood operation.

BACKGROUND: In the Fontan circulation, energy consumption at the cavopulmonary connection is crucial. Our hypothesis was that a modification of the standard Norwood variant of cavopulmonary connection with an extended anastomosis would improve hydrodynamics. METHODS: The in vitro hydrodynamics of two different Perspex glass models resembling the Norwood variant of cavopulmonary connection (model I) and the modification (model II) were analyzed in a mock circulation at nonpulsatile flows of 2 to 5 L/min to simulate rest and exercise. The pulmonary flow split was varied to imitate varying lung resistances. Inferior-to-superior caval flow ratio and size of models were increased to simulate growth. RESULTS: The pulmonary flow was preferentially directed to the left lung in model I and was better balanced in model II. Power losses increased exponentially with total flow in both models and were markedly higher in model I. These differences were attenuated in the larger models. Anastomotic turbulences were larger in model I. Power losses in both models were relatively insensitive to changes in pulmonary flow split. CONCLUSIONS: The proposed modification of the Norwood variant of cavopulmonary connection seems to be hydrodynamically advantageous and warrants further evaluation.

Anastomosis, Surgical↗
PubMed1977

Are pelvic irradiation and routine staging laparotomy necessary in clinically staged IA and IIA Hodgkin's disease?

Thirty-nine patients with clinically staged IA and IIA Hodgkin's disease were treated with mantle plus paraaortic/splenic irradiation between 1968 and 1975. All patients had supradiaphragmatic presentations, and none had staging laparotomies. With a follow-up time of 1 to 9 years, mean 4.3 years, the overall relapse-free survival is 92% (100% for stage IA and 89% for stage IIA). The absolute relapse-free 5-year survival is 91% There were no pelvic recurrences. These data show that routine staging laparotomy and pelvic irradiation are not indicated for clinically staged IA and IIA Hodgkin's disease with supradiaphragmatic presentation. The criteria for staging laparotomy in early-stage Hodgkin's disease are discussed.

Adolescent↗
PubMed1977

Effect of local irradiation on the acute rejection process in transplanted kidneys.

The graft in 178 renal transplant patients was irradiated in an effort to halt acute rejection phenomena. Of the patients, 61 per cent received their transplant from either a sibling, parent or child and 38 per cent received cadaveric kidneys. Of the irradiated kidneys 61 per cent were functioning at 6 months, 58 per cent at 12 months and 49 per cent at 18 months. The rational for irradiation of transplanted kidneys with acute rejection is discussed.

Adolescent↗
PubMedDate not supplied

Does caval aplanarity influence power losses across in vitro cavopulmonary connections?

Optimally designed cavopulmonary connections are desirable to reduce transanastomotic power loss. Since aplanarity of the total cavopulmonary connections results from the natural anterior-posterior position of the superior vena cava and the right pulmonary artery, the aim of this study was to investigate the influence of aplanarity of caval offset on transanastomotic power losses. Two types of cavopulmonary connections, a planar cross-like connection and a nonplanar V-shaped anastomosis, were studied in a mock circulation, comparing for each type native porcine vessels and Perspex glass models. Total flow varied between 1200 and 6000 ml/min at superior to inferior caval flow ratios of SVC/IVC = 50/50% and 33/67%, respectively. Pressures and flows were measured and power losses calculated. No significant differences in power losses were found between the planar and aplanar connections for native vessels or for Perspex glass models. Power losses across the native preparations in each configuration were significantly higher than those in the corresponding Perspex glass model. The simulation of the natural aplanar V-shaped caval offset in total cavopulmonary connections used to bypass the right ventricle seems to have no relevant additional effect on in vitro power losses compared to planar connections.

Adolescent↗