Elimination of sevoflurane is reduced in plasma-tight compared to conventional membrane oxygenators.

BACKGROUND AND OBJECTIVE: It has been demonstrated that volatile anaesthetics have cardioprotective properties during open-heart procedures, especially when administered continuously. European Council Directive 93/42/EEC concerning medical devices bans the supplementary incorporation of anaesthetic vaporizers in the bypass circuit. Since the uptake of volatile anaesthetics via diffusion membrane oxygenators is severely reduced, it is hypothesized that clinically relevant concentrations of sevoflurane will remain in the patients' blood following saturation with a volatile agent before start of cardiopulmonary bypass. This study was designed to compare conventional and diffusion membrane oxygenators regarding their in vivo elimination of sevoflurane. METHODS: Twenty patients undergoing elective coronary bypass surgery were randomly allocated to two groups, either using a conventional polypropylene membrane oxygenator or a plasma-tight poly-(4-methyl-1-pentene) membrane oxygenator in a miniaturized extracorporeal circuit. Anaesthesia was maintained with sevoflurane, which was stopped at the start of cardiopulmonary bypass. During cardiopulmonary bypass, sevoflurane concentration was measured in blood and in the exhausted gas from the oxygenator. RESULTS: The elimination of sevoflurane, expressed as the relative blood concentration, was significantly increased in polypropylene membrane oxygenators compared to poly-(4-methyl-1-pentene) membrane oxygenators. This resulted in an approximately threefold higher sevoflurane blood concentration in the poly-(4-methyl-1-pentene) group over the course of cardiopulmonary bypass. CONCLUSIONS: With the incorporation of a poly-(4-methyl-1-pentene) oxygenator in a miniaturized bypass circuit, relevant concentrations of a previously applied volatile agent can be maintained even without further supply throughout cardiopulmonary bypass. This might be an alternative approach to cardioprotection when sevoflurane cannot be administered through cardiopulmonary bypass.

Measuring depth of sedation in intensive care patients with the electroencephalographic Narcotrend Index.

BACKGROUND AND OBJECTIVE: The electroencephalographic Narcotrend Index was evaluated as a measure of sedation in mechanically ventilated intensive care unit patients. Narcotrend Index and conventional electroencephalography parameter values were compared to the Richmond Agitation-Sedation Scale and a simplified three-level sedation scale. METHODS: In all, 100 mechanically ventilated patients, admitted to the cardiac surgical intensive care unit after open-heart surgery, were enrolled in this prospective observational study. The Narcotrend Index was recorded while patients were either sedated by propofol infusion or without sedative medication while being weaned off the ventilator. Clinical assessment of the patients' level of sedation was performed by means of the Richmond Agitation-Sedation Scale by a single observer who was blinded to the Narcotrend Index. RESULTS: With the six-level Richmond Agitation-Sedation Scale, the prediction probability (PK) for the Narcotrend Index (0.81) was better than for all other electroencephalography parameters (P < 0.01) except for relative power in the beta band (PK 0.75). Using the three-level sedation scale instead, PK values for the Narcotrend Index (0.88) and all electroencephalography parameters improved (P < 0.01), and the Narcotrend Index was now superior to all electroencephalography parameters. Narcotrend Index values were distributed among the various sedation levels with significant overlap. CONCLUSION: When used for assessment of propofol sedation in postsurgical cardiac intensive care unit patients, the Narcotrend Index can distinguish between very light and deep sedation. With respect to differentiation between light and moderate or moderate and deep sedation, the Narcotrend Index was not reliable in this study.

Assessment of fluid responsiveness in mechanically ventilated cardiac surgical patients.

BACKGROUND AND OBJECTIVE: Accurate assessment of preload responsiveness is an important goal of the clinician to avoid deleterious volume replacement associated with increased morbidity and mortality in mechanically ventilated patients. This study was designed to evaluate the accuracy of simultaneously assessed stroke volume variation and pulse pressure variation using an improved algorithm for pulse contour analysis (PiCCO plus, V 5.2.2), compared to the respiratory changes in transoesophageal echo-derived aortic blood velocity (deltaVpeak), intrathoracic blood volume index, central venous pressure and pulmonary capillary wedge pressure to predict the response of stroke volume index to volume replacement in normoventilated cardiac surgical patients. METHODS: We studied 20 patients undergoing elective coronary artery bypass grafting. After induction of anaesthesia, haemodynamic measurements were performed before and after volume replacement by infusion of 6% hydroxyethyl starch 200/0.5 (7 mL kg(-1) ) with a rate of 1 mL kg(-1) min(-1). RESULTS: Baseline stroke volume variation correlated significantly with changes in stroke volume index (deltaSVI) (r2 = 0.66; P < 0.05) as did baseline pulse pressure variation (r2 = 0.65; P < 0.05), whereas baseline values of deltaVpeak, intrathoracic blood volume index, central venous pressure and pulmonary artery wedge pressure showed no correlation to deltaSVI. Pulse contour analysis underestimated the volume-induced increase in cardiac index measured by transpulmonary thermodilution (P < 0.05). CONCLUSIONS: The results of our study suggest that stroke volume variation and its surrogate pulse pressure variation derived from pulse contour analysis using an improved algorithm can serve as indicators of fluid responsiveness in normoventilated cardiac surgical patients. Whenever changes in systemic vascular resistance are expected, the PiCCO plus system should be recalibrated.

[Pumpless extracorporeal lung assist using arterio-venous shunt in severe ARDS. Experience with 30 cases]. / Pumpenfreie extrakorporale Lungenunterstützung mit arteriovenösem Shunt beim schweren akuten Lungenversagen des Erwachsenen. Bericht über 30 Einsätze.

BACKGROUND: Extracorporeal lung assist has been proposed as an invasive measure in patients with acute respiratory distress syndrome (ARDS) when oxygenation is critically impaired. However, this technique generally requires high personnel and technical resources. We report on a new system, which is characterised by a short circuit arterio-venous shunt using arterio-venous pressure gradient as driving force (pumpless extracorporeal lung assist [pECLA]). PATIENTS AND METHODS: In 30 patients with ARDS due to multitrauma, pneumonia or after surgery (p(a)O(2)/F(I)O(2)-ratio 67+/-23 mmHg) pECLA was established by insertion of cannulae to the femoral artery and vein followed by connection with a membrane gas exchanger. For this system, only "low dose" continuous heparin infusion is required. RESULTS: Arterial oxygenation was acutely and significantly increased by pECLA (p(a)O(2)/F(I)O(2)=103+/-56 mmHg 2 h after begin) and carbon dioxide removal was markedly enhanced in 25 out of 30 patients (87%) allowing a lung protective ventilation strategy. The mean duration of pECLA therapy was 6.5 days, 15 patients (50%) died due to ARDS or non-ARDS related reasons. CONCLUSION: pECLA represents a feasable and effective treatment in patients with severe ARDS. Compared with pump-driven systems pECLA is characterised by low costs and reduced personnel requirements. However, mortality remains high in patients suffering from severe ARDS despite newer treatment modalities.

Assessment of intrathoracic blood volume as an indicator of cardiac preload: single transpulmonary thermodilution technique versus assessment of pressure preload parameters derived from a pulmonary artery catheter.

OBJECTIVE: To analyze the clinical value of a new device (PiCCO) for cardiac output measurement and volume preload parameter assessment, based on transpulmonary thermodilution technique, as an alternative to the pulmonary artery thermodilution technique and assessment of pressure preload parameters derived from the pulmonary artery catheter. DESIGN: Prospective, controlled, clinical study. SETTING: University hospital. PARTICIPANTS: Eighteen patients with ejection fraction >50% undergoing coronary artery bypass graft surgery. INTERVENTIONS: A baseline measurement was performed after induction of anesthesia under clinical steady-state conditions (T1). Hypovolemia, defined as central venous pressure (CVP) <10 mmHg and pulmonary capillary wedge pressure (PCWP) <12 mmHg, was treated by infusion of 6% hydroxyethyl starch 200/0.5 (7 mL/kg). After 10 minutes, a second measurement (T2) was performed. MEASUREMENTS AND MAIN RESULTS: The mean difference (bias) between transpulmonary thermodilution cardiac output and pulmonary artery thermodilution cardiac output did not differ at the 2 sample points. Changes in pressure preload parameters of the pulmonary artery catheter (CVP, PCWP) did not correlate with changes in cardiac output or stroke volume, whereas changes in volume preload parameter intrathoracic blood volume (ITBV) of the PiCCO correlated significantly with changes in cardiac output and stroke volume (r = 0.55, p < 0.05; r = 0.62, p < 0.01). CONCLUSION: These results suggest that increased cardiac preload is more reliably reflected by ITBV than by CVP or PCWP. The assessment of ITBV by the transpulmonary single indicator dilution technique is an interesting alternative to the pressure preload parameters.

A new endotoxin adsorber: first clinical application.

In an open, uncontrolled pilot study, 5 men and 1 woman with suspected gram-negative sepsis were treated with a new whole-blood endotoxin adsorption system. Lipopolysaccharide (LPS) adsorption was carried out by hemoperfusion over high-affinity polymethacrylate-bound albumin (Fresenius Endotoxin Adsorber EN 500). All patients suffered from endotoxemia (>20 pg/ml LAL) and met at least two systemic inflammatory response syndrome (SIRS) criteria. Four patients suffered from pneumonia due to mechanical ventilation, one from peritonitis, and one from pneumonia and peritonitis. Endotoxin adsorption was very well tolerated, and efficient LPS removal was shown in all patients. Apache II score immediately before immunoadsorption was 23.5 and was 22.3 after the last treatment. All 6 critically ill patients improved substantially and were discharged from the intensive care unit. LPS whole blood immunoadsorption is a promising new method. No side effects have been observed thus far. A large controlled study to prove clinical efficacy in patients with severe sepsis is under way.

Continuous cardiac output measurement: pulse contour analysis vs thermodilution technique in cardiac surgical patients.

We have analysed the clinical agreement between two methods of continuous cardiac output measurement pulse contour analysis (PCCO) and a continuous thermodilution technique (CCO), were both compared with the intermittent bolus thermodilution technique (BCO). Measurements were performed in 26 cardiac surgical patients (groups 1 and 2, 13 patients each, with an ejection fraction > 45% and < 45%, respectively) at 12 selected times. During operation, mean differences (bias) between PCCO-BCO and CCO-BCO did not differ in either group. However, phenylephrine-induced increases in systemic vascular resistance (SVR) by approximately 60% resulted in significant differences. Significantly higher absolute bias values of PCCO-BCO compared with CCO-BCO were also found early after operation in the ICU. Thus PCCO and CCO provided comparable measurements during coronary bypass surgery. After marked changes in SVR, further calibration of the PCCO device is necessary.

[Experimental principles and general practice of intraoperative autotransfusion with blood irradiation in tumor operation]. / Experimentelle Grundlagen und Praxis der intraoperativen Autotransfusion mit Blutbestrahlung bei Tumoroperationen.

Clinical studies fail to verify or to exclude the lethal risk of tumor spread after intraoperative autotransfusion in tumor surgery. An alternative approach is the development of methods for the elimination of tumor cells in the salvaged blood. The radiosensitivity of tumor cells especially in oxygenated single cell suspensions is well known, while the non-nucleated red blood cells are radioresistant. With 50 Gy a 12 log reduction in proliferating cells is expected. This we have tested experimentally and put into clinical practice. The suppression of colony formation in cell culture by irradiation with 50 Gy was tested with tumor cells from established cell lines or from solid tumors after admixture in high cell number to red blood cells from volunteer blood donations. DNA metabolism was tested by incorporation of bromodesoxyuridine (BrdUrd) and staining with mcab-anti-BrdUrd. Colony formation and DNA metabolism was absent in all samples of cell lines or tumor cells in blood after irradiation with 50 Gy, reflecting a 10 log, or 7 log reduction, respectively. In clinical practice the method of intraoperative blood salvage during tumor surgery with blood irradiation showed its practicability and efficacy in reducing homologous transfusions.

Diagnostic value of AgNOR staining in follicular cell neoplasms of the thyroid: comparison of evaluation methods and nucleolar features.

The diagnostic value of argyrophil staining of nucleolar organizer regions (AgNOR) was studied in 95 nonneoplastic and neoplastic follicular lesions of the thyroid. Different AgNOR parameters such as number, size, and distribution pattern were determined using digital image analysis. In addition, nuclear and nucleolar size as well as the percentage of nucleoli touching the nuclear membrane (nucleolar margination) were assessed. A stepwise increase in nuclear size and AgNOR counts from normal thyroid tissue to follicular adenoma as well as from differentiated follicular to anaplastic carcinoma was found (mean nuclear area [micron2]/mean AgNOR number per cell: 21.5/1.6 vs. 34.4/3.5 and 45.3/5.0 vs. 66.5/10.8, p < 0.01/p < 0.001). There was, however, no clear separation between these diagnostic groups. In contrast, an almost total discrimination between follicular adenoma and carcinoma was achieved by quantification of AgNORs per tumor cell nucleolus (AgNOR distribution score). In benign adenomas, 3.3% (range, 0-8.8%) of the cells showed nucleoli with at least five AgNOR dots within one focal plane, whereas in follicular carcinomas, the corresponding value was 34.1% (range, 12-75%). Two of four cases of so-called atypical adenomas showed values in the range of benign adenomas, and two were in the range of follicular carcinomas. In comparison with other nuclear and nucleolar parameters, the AgNOR distribution score proved the most valuable diagnostic criterion for the cytomorphological differentiation between follicular adenoma and carcinoma of the thyroid.