Kai Winkler

University of Bonn, Bonn, North Rhine-Westphalia, Germany

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Publications (6)9.64 Total impact

  • A. Welz · C. Welz · K. Winkler · W. Schiller · N. Theuerkauf
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    ABSTRACT: In recent years extracorporeal life support systems (ECLS) have become well-established in specialized centers for treatment of acute respiratory failure and cardiogenic shock. They are used in combination with veno-venous extracorporeal membrane oxygenation (vv-ECMO) to treat potentially reversible respiratory insufficiency and by way of veno-arterial (va)-ECMO for severe acute cardiorespiratory failure. An ECLS is designed to be a temporary support with the intention of bridge to recovery, bridge to next decision and finally bridge to transplantation. Vascular access for vv-ECMO is gained percutaneously via the femoral or internal jugular vein. In cases of va-ECMO support systems percutaneous puncture or cannulation by surgical preparation can be advantageous. In addition intrathoracic cannulation of the right atrium and the ascending aorta is performed especially in cases of postcardiotomy low cardiac output. The most common indications for vv-ECMO are acute respiratory distress syndrome (ARDS) due to viral, bacterial and fungal infections and posttraumatic pulmonary shock syndrome. In addition to being used after failed weaning from a heart-lung machine following cardiac surgery, va-ECMO is used for cardiogenic shock after myocarditis and myocardial infarction. This article describes the technical aspects of ECLS. Additionally, the pathophysiological details of ECMO, the indications, complication possibilities and outcomes are discussed.
    No preview · Article · Jul 2015 · Zeitschrift für Herz- Thorax- und Gefäßchirurgie
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    ABSTRACT: Background Aortic dissection is a severe and sophisticated disease that is often linked with a number of possible complications. Our study concerns with long-term outcome and quality of life (QoL) in acute aortic dissection type A (AADA) survivors. Methods From January 1999 until December 2006, 120 consecutive patients with AADA received an emergency operation. Of the total number of patients, 84 were males (70.0%) and 36 females (30.0%), mean aged 59.8 ± 12 years with a mean follow-up (FU) of 99.2 ± 6 months. Results Overall mortality was 39.1% during the observational period with a maximum of 156 months. SF-36 observation showed a significant decay in both Physical Component Summary (PCS) and Mental Component Summary (MCS) in FUII (PCS = 38.4) versus FUI (PCS = 43.4, p = 0.013). Conclusion With ongoing postoperative time, patients did not recover but instead have got worse in terms of QoL. The decrease in MCP and linked subscores is an underestimated factor in QoL and long-term outcome after AADA. This is especially true in younger patients, which are judged to compensate better than older patients. Georg Thieme Verlag KG Stuttgart · New York.
    No preview · Article · Apr 2015 · The Thoracic and Cardiovascular Surgeon
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    ABSTRACT: The scope of this paper was to determine whether ischemic and reperfusion damage in cardiac surgery can be detected by measurement of electrical bioimpedance (EBI). Conventional pacing wires were replaced by pacing wires with sputtered iridium coating in order to reduce polarization associated with two-electrode impedance measurements. A custom-built bioimpedance analyzer (Osypka Medical GmbH, Berlin, Germany) measured the real part of impedance Re(Z) and the phase (ϕ) at three frequencies (1, 10, and 1000 kHz) and determined an extracellular space index (EZRI) as the quotient of Re(Z) at 1000 kHz and Re(Z) at 1 kHz. Our study included six patients (conventional coronary artery bypass graft, age 68.1 ± 8.3 years) subject to routine cardioplegic ischemia and reperfusion. Preischemic bioimpedance measurements were not impaired by interference of the beating heart. Intraischemically, bioimpedance at 1 kHz and phase at 10 kHz increased until opening of a bypass graft, which is probably induced by closure of gap junctions and cell swelling processes. After cross clamping, EZRI slowly decreased as an effect of mild cell swelling. After ischemia, values returned almost to baseline measurements, indicating sufficient reperfusion processes. Measurement of EBI correlates with myocardial ischemic injury and is applicable in a two-electrode setup providing low-polarization pacing wires.
    No preview · Article · Jun 2011 · IEEE transactions on bio-medical engineering
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    ABSTRACT: On-pump cardiac surgery is accompanied by complex alterations of hemostasis. The excessive postoperative bleeding has been attributed to acquired platelet dysfunction, impaired plasmatic coagulation, and increased fibrinolysis. The characterization of the hemostatic defects responsible for bleeding is crucial for specific treatment and optimal clinical management of the patient. For rapid determination of platelet-dependent primary hemostatic capacity (PHC), the Platelet Function Analyzer PFA-100 system is available. To evaluate the PFA performance in perioperative monitoring, a study was performed in 49 patients selected for low bleeding risk undergoing selective primary coronary artery bypass grafting (CABG). We compared PHC with Simplate bleeding time (BT) and platelet aggregometry. Furthermore, we analyzed global hemostasis by thromboelastography (TEG) and plasmatic coagulation by standard clotting tests prothrombin time (PT, Quick), activated partial thromboplastin time (aPTT), thrombin time (TT) and clotting factors and fibrinolysis by batroxobin (reptilase) time (RT). In all patients BT was postoperatively increased by 1.5- to 2-fold irrespective of perioperative complications and decreased to mildly prolonged values on the first postoperative day (1st day). In patients without complications, PHC in both collagen-adenosine diphosphate closure time (CADP-CT: 83 seconds preop, 78 seconds postop, and 74 seconds 1st day) and collagen-epinephrine closure time (CEPI-CT: 98 seconds preop, 95 seconds postop, 85 seconds 1st day) remained nearly stable. Apart from a patient with postoperative moderate thrombocytopenia, in bleeding patients no other significant defect of postoperative platelet hemostatic capacity was observed. However, on 1st day, the PHC of those patients was significantly reduced compared with non-bleeding patients. In patients with postoperative myocardial ischemia, increased PHC was identified by significantly shorter postoperative CADP-CT (66 seconds vs. 83 seconds) than in uncomplicated patients. By aggregometry, partial platelet dysfunction was observed in some patients without correlation to bleeding complications. In seven of 9 patients the postoperative bleeding complication was attributed to prolonged heparin anticoagulation and/or mildly enhanced fibrinogenolysis/fibrinolysis by TEG and standard plasmatic coagulation tests (TEG: k time 18 minutes vs. 8 minutes; aPTT: 47 seconds vs. 32 seconds; TT: 18.0 seconds vs. 12.3 seconds) and (RT: 19.5 seconds vs. 17.7 seconds). The impairment of PHC, platelet aggregation, and clotting factors observed on the 1st day in bleeding and in intra-aortic balloon pump (IABP) patients are most likely secondary effects, for example, loss of active platelets and clotting factors, to the primary postoperative bleeding or implantation of the IABP. In conclusion, our data indicate that in standard CABG procedures highly variable alterations of the hemostatic system occur after cardiopulmonary bypass (CPB) even in patients with assumed low operative risks. For identification of post-CPB bleeding complications, thromboelastography, aPTT, and TT and heparin and batroxobin (reptilase) time as fibrinolysis-sensitive assays are useful. Platelet function appears to be rapidly restored in uncomplicated CABG. PHC determination by PFA-100 demonstrates a high specificity for adequate platelet function and, therefore, could be beneficial in improved transfusion of platelet concentrates. PHC testing by PFA-100 may help identify postoperative platelet hyper-reactivity associated with myocardial lesion.
    No preview · Article · Feb 2005 · Seminars in Thrombosis and Hemostasis
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    ABSTRACT: The aim of this study was to evaluate the role of cardiac Troponin I (cTnI) and CK-MB for early prediction of outcome of patients undergoing coronary artery bypass grafting (CABG) surgery. In 134 consecutive patients undergoing CABG-surgery blood samples were analyzed for cTnI concentration and CK-MB activity. ECG, hemodynamic parameters and the need for inotropic support, were continuously registered. Patients were divided into group A (uneventful course), group B (ischemia by ECG, hemodynamic stability) and group C (ischemia by ECG and IABP). After removal of X-clamp an increase cTnI and CK-MB was observed in all patients. Five hrs after stop of CPB group A (8.3+/-4.2 microg/L) had lower cTnI values compared to group B (14.8+/-5.3 microg/L) (p=0.035) and C (54+/-22.8 microg/L) (p=0.023). The cut off value was 14.8 microg/L. Sensitivity and specificity (99%/97%) was higher for cTnI than for CK-MB (90%/30%). The positive predictive value of outcome was better for cTnI (86%) than for CK-MB (33%). CTnI is a specific and sensitive marker for evaluation of perioperative myocardial ischemia (PMI). Additional determination of CK-MB activity does not provide further clinical information. CTnI should be the marker of first choice in CABG surgery.
    No preview · Article · May 2003 · The Journal of cardiovascular surgery
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    ABSTRACT: Transcatheter occlusion of uncomplicated atrial septum defects (ASD) is recognized as an effective and minimally invasive method. Sometimes, serious early and late complications require surgical intervention. We therefore investigated reasons and outcomes of the secondary surgical approach. 5 patients (aged 5-73 yrs) were admitted to our institution for device explantation and surgical ASD closure. ASDOS devices (A devices) had to be explanted in 4 patients and a SIDERIS "buttoned" occluder (S device) had to be explanted in 1 patient. The period from transcatheter implantation to surgical explantation ranged from 1 hour to 3 years. 3 patients (60 %) had to be operated in an emergency setting. In our youngest patient (5 yrs), the A device separated and embolized into the aorta and pulmonary artery. A pregnant women who needed emergent cesarean section developed hemopericard and tamponade due to atrial perforation by a fractured leg of an A device. In another A device, a suspect endocarditis caused membrane perforation. Malpositioning of an S device was the reason for operation. All patients recovered well without neurological symptoms. Transcatheter closure of uncomplicated ASD is a feasible alternative but surgical stand-by is essential. Nevertheless more complicated ASD should be operated, especially since the cosmetically satisfactory techniques of minimal invasive heart surgery are available.
    No preview · Article · Jan 2002 · The Thoracic and Cardiovascular Surgeon