[Bedside thrombelastography. Cost reduction in cardiac surgery]. / "Bedside"-Thrombelastographie. Kostenreduktion in der Herzchirurgie.

BACKGROUND: Demographic changes and aggressive medication with platelet aggregation inhibitors have resulted in a marked increase in blood and coagulation product expenditure and costs in cardiac surgery. We analyzed the bedside coagulation test (ROTEM) in order to verify clot forming quality and to find a cost-effective treatment algorithm. PATIENTS AND METHODS: Annual treatment costs of all cardiosurgical patients were retrospectively analyzed before (729 patients) and after (693 patients) implementation of the bedside ROTEM test. Cumulative numbers and costs of platelet concentrates (PltC), fresh frozen plasma (FFP), red blood cell units (RBC), and the coagulation factors prothrombin complex concentrates (PCC), recombinant factor VIIa (rFVIIa), factor XIII (FXIII), and fibrinogen were assessed. Average monthly numbers and costs were compared. The number of rethoracotomies and early mortality were assessed and compared in both periods. RESULTS: After ROTEM implementation cumulative RBC expenditure showed a 25% decrease and PltC a 50% decrease. FFP expenditure remained unchanged. PCC, FXIII were markedly reduced (-80%) while rFVIIa was entirely omitted. Fibrinogen, however, showed a two-fold increase. Cumulative average monthly costs of all blood products decreased from 66,000 EUR to 45,000 EUR (-32%). Coagulation factor average monthly costs decreased from 60,000 EUR to 30,000 EUR (-50%) yielding combined savings of 44%. In contrast, average monthly costs for ROTEM were 1,580 EUR. The total number of rethoracotomies decreased from 6.6% to 5.5% while early mortality (5.9%; 6.0%) remained stable. CONCLUSIONS: Cumulative costs for treatment of perioperative coagulation disorders were reduced by bedside ROTEM analysis to achieve a selective substitution management. Saved costs for blood and coagulation products clearly outweighed the expenses of ROTEM. Adequate differential coagulation management can therefore be cost-effective.

Opening and closure characteristics of different types of stented biological valves.

BACKGROUND: In an increasingly senescent population stented biological valves have regained renewed popularity because of the absence of anticoagulation, while the stented design allows for safe and easier implantation. Constructed bovine pericardial valves as well as valves with porcine cusps are used, both of which exhibit good clinical results although degeneration still appears. While clinical hemodynamic studies did not show particular differences between both valves types, the opening and closure behavior of native cusps and artificially constructed pericardial leaflets is different. It is unclear whether these phenomena account for differences in load and stress which may influence onset and course of degeneration. MATERIAL AND METHODS: Edwards Perimount (EP) and Medtronic Mosaic (MM) heart valves with diameters of 21 mm, 23 mm, and 25 mm were investigated in a pulse duplicator. Movements of the valves were visualized with a high-speed camera (1000 frames/sec). Mean transvalvular gradient (mm Hg), dissipated power (mW), and power transfer by stretching (mW), mean orifice area (mm2), opening time (ms), and closure time (ms) were analyzed in a range of cardiac outputs from 1.4 l/min to 6.3 l/min and 70 beats per minute. RESULTS: Closure times were generally longer than opening times for both valve types. Opening time of EP valves was longer than opening time of the MM valves of the same size (EP23: 31.2 +/- 2.5 ms; MM23: 12.7 +/- 0.1 ms). With respect to closure times, however, there were no marked differences between all valves (EP23: 69.3 +/- 2.0 ms; MM23: 63.2 +/- 6.3 ms). Smaller sized Perimount valves exhibited lower mean transvalvular gradients than Mosaic valves of the same size (EP23: 7.21 +/- 0.07 mm Hg; MM23: 10.5 +/- 0.15 mm Hg). In larger sizes these differences diminished. Power transfer to the valve's structures was significantly enhanced in EP valves (EP23: 134 +/- 1.3 mW; MM23: 64 +/- 0.9 mW). CONCLUSIONS: While valves with constructed pericardium showed lower mean transvalvular gradients, particularly in the smaller sizes, this valve type exhibited alterations of movement performance in contrast to porcine valves. It can be speculated that constant power transfer to the valve's structures may result in an earlier degeneration because of the impact of the increased load and stress on the suspension apparatus of the constructed pericardial leaflets.

Deairing of the venous drainage in standard extracorporeal circulation results in a profound reduction of arterial micro bubbles.

OBJECTIVE: Standard extracorporeal circulation (ECC) remains the staple procedure for cardiac surgeons. Despite modern membrane oxygenators and arterial filters micro bubbles are regularly detected in the arterial line. We investigated whether initial deairing of the venous drainage during connection can reduce the quantity and size of micro bubbles on the arterial side. METHODS: 12 patients underwent isolated coronary artery revascularization with conventional ECC using a two-stage venous catheter and an open, passive venous return into a reservoir. In 6 patients (Control) the venous catheter was routinely connected to the venous line, thereby accepting moderate incorporation of air. In another 6 patients (deaired) the catheter was connected avoiding any visible air entrapment. A bubble counter was used to detect the number and size of any micro bubbles in the arterial line of the ECC. The total number of bubbles as well as the number of bubbles of different sizes was assessed directly after initiation of ECC and during the first 60 sec. RESULTS: All patients had an uneventful surgery with a normal postoperative course. In the Control group a considerable number of bubbles of all sizes occurred initially and after 60 sec. In contrast, very few bubbles were detected in the deaired group. CONCLUSION: Incorporated venous air inevitably reaches the arterial side of the ECC. As deairing of the venous line is a simple and effective manoeuvre to significantly reduce the amount of micro bubbles on the arterial side, we recommend and perform routine deairing in all our patients.

Different tilting disc valves show similar rotation-dependent impairment in hemodynamic performance under a tilted implantation position.

BACKGROUND: Aortic annulus calcification can promote tilted implantation of mechanical valves. This study evaluates the hemodynamics of tilting disc valves under this condition. METHODS: 23 mm and 25 mm Ultracor (UC) and Medtronic-Hall-Easy-Fit (MH) valves were investigated in a pulse-duplicator under physiological conditions. Mean pressure gradient (dP(mean)), systolic energy loss (dW(sys)), effective orifice area (EOA), closure (V(Cl)), leakage (V(L)), and total regurgitation volume (V(R)) were assessed. Valves were independently positioned at five axial rotations (0 - 180 degrees , zero defined as major orifice facing the top of the "tilt-ramp") and three tilt angles (0 degrees, 10 degrees, 20 degrees) by lifting the prosthesis in the noncoronary sinus. RESULTS: Diameter-enhanced MH valves exhibited a better systolic performance but a higher regurgitation than corresponding UC valves. Moderate tilting showed a rotation-independent increase in dP(mean) and dW(sys) and a decrease in V (R) and EOA with no fundamental differences between valve types. Further tilting caused small additional changes at 90 - 180 degrees rotation. At 0 degrees rotation, however, dramatic regurgitation occurred throughout. CONCLUSION: Tilting worsened systolic performance regardless of valve type. It should therefore be avoided. Due to extensive regurgitation at 0 degrees rotation, this position should be corrected whenever tilting is inevitable.

Inhaled nitric oxide and inhaled prostaglandin E1: effect on left ventricular contractility when used for treatment of experimental pulmonary hypertension.

OBJECTIVE: Pulmonary hypertension (PHT) is a life-threatening complication after isolated heart and lung transplantation. Recent work has shown that inhaled nitric oxide (NO) in combination with inhaled prostaglandin E1 (PGE1) reduce pulmonary hypertension but their influence on cardiac contractility is less well defined. METHODS: This study investigated left ventricular contractility as measured by the 'Preload Recruitable Stroke Work-Relation' (PRSW) in 24 anesthetized open chest pigs, 12 receiving in random order NO (50 ppm), PGE1 (20 microg/ml) and their combination compared to 12 controls. PHT was induced by embolization with glass beads (500 microm). Prior to induction of PHT, sonomicrometric crystals were placed on the heart to measure instantaneous cardiac dimensions. Instantaneous intraventricular pressure (micro-tip catheter) and intraventricular dimensions were recorded digitally, while intraventricular volumes were calculated from the intraventricular dimensions applying the cylindric ellipsoidal volume model for the left ventricle. PRSW was calculated from the instantaneous pressure and volume data during rapid vena caval occlusion by analysis of generated pressure-volume loops. All data were analyzed by MANOVA and corrected for heart rate (level of significance #: P < 0.05); PRSW-slope measures contractility, (PRSW-X-intercept did not change significantly). RESULTS: PRSW-change +/- SEM (in percent of initial PRSW after induction of PHT) was -14.6% +/- 4.4% versus 1.6% +/- 4.4% for NO versus Control (P = 0.004), -8.8% +/- 4.6% versus 1% +/- 3.3% (P = 0.18) for PGE1 versus Control and -5.7% +/- 4.4% versus 2.5% +/- 4.2% for NO + PGE1 versus Control (P = 0.33), respectively. In summary, application of NO 50 ppm significantly reduced left ventricular contractility while PGE1 20 microg/ml and the combination of NO and PGE1 did not. CONCLUSION: If NO is not available, the sole application of nebulized PGE1 (20 microg/ml) appears to be safe with respect to left ventricular contractility in the setting of PHT. The combination of NO and PGE1 for the treatment of pulmonary hypertension should be considered for clinical application in situations where a combination of pulmonary hypertension and decreased left ventricular function is present.

Optical three-dimensional measurements by radially symmetric structured light projection.

This structured light projection technique has been developed for the inspection of holes and tubes. In contrast to others, the triangulation base is parallel to the line of sight. The features of systems using this measurement method are the following: high accuracy in the wide-angle region, minimal diameter, symmetry of the measurements to the line of sight, and simplified coordinate calculation. The prototype application is the optics of the sewer pipe inspection robot KARO. Application fields are medical or technical wide-angle inspection systems (e.g., endoscopes).