OBJECTIVES:The paO(2) and AaDO(2) are routinely measured for evaluating pulmonary gas exchange. The normal value of the AaDO(2) amounts 10 mmHg when breathing atmospheric air and is said to increase with rising FIO(2). This increase is discussed controversially. One possible reason for incongruities in AaDO(2) measurement may be the impact of so called preanalytical errors during paO(2) measurement, which are often neglected. Therefore, the aim of this study was to evaluate the relevance of preanalytical errors on the AaDO(2) under hyperoxic conditions.METHODS:Arterial blood gas analysis was performed on twenty patients without known pulmonary disease after tracheal intubation and 30 min of ventilation with pure oxygen. All preanalytical paO(2) errors (sampling technique, transport and storage of samples, aspirated air bubbles) were assessed and all paO(2) measurements were corrected by applying respective predetermined correction factors. Calculation of the AaDO(2) was performed with corrected and uncorrected paO(2) values.RESULTS:The average amount of the AaDO(2) under ventilation with FIO(2)=1.0 was 118.9+/-41.1 mmHg, calculated from uncorrected paO(2) values, and 13.4+/-7.5 mmHg calculated from paO(2) values corrected for preanalytical errors, respectively.CONCLUSION:The present results show that the assumption of an increasing AaDO(2) with rising FIO(2) is questionable. It could be proved that neglecting preanalytical paO(2) errors leads to a significant overestimation of the AaDO(2). The consequence would be a misinterpretation of the patient's condition in relation to a reduced pulmonary gas exchange, which should in fact be attributed solely to the preanalytical errors.

OBJECTIVE:Antifibrinolytic drug therapy has proved to be effective in reducing blood loss associated with cardiac surgery and cardiopulmonary bypass (CPB). Concerns remain regarding the risk of enhancing thrombosis. In the present study we investigated the effect of aprotinin (AP) and tranexamic acid (TA) on fibrinolysis and thrombin generation during CPB.METHODS:60 patients undergoing coronary artery bypass graft surgery were randomised in 3 groups. They received either aprotinin ("high-dose-scheme"), tranexamic acid (2 g/h) or no antifibrinolytic therapy (control group). Collection of blood was performed at 7 pre-, intra- and postoperatively predetermined intervals. Fibrinolytic activity was determined by measuring concentrations of D-dimer, thrombin generation by the measurement of thrombin-antithrombin III complex (TAT).RESULTS:There was no significant increase of D-dimers in the AP or TA group. D-dimer concentration in the control group increased significantly after starting CPB. Comparing with the control group, thrombin generation in the AP group was significant less, while TA group produced significantly higher values.CONCLUSION:After the administration of AP for cardiac surgery we observed reductions in both intraoperative fibrinolysis and thrombin generation. In case of TA suppression of fibrinolytic activity in the absence of concomitant reduction in thrombin generation occurred. These results suggest that TA could potentiate a hypercoagulable state with the risk of thrombosis in the perioperative setting.

OBJECTIVE:A variety of influences reduce the validity of the measured oxygen partial pressure (paO(2)). Most errors occur when obtaining the blood sample and preparing it for analysis. Unfortunately, there is great controversy concerning the relevance and extent of these pre-analytic errors. Apart from this, the exact estimation of influencing factors under hyperoxic conditions has been neglected. Therefore, the objective of this study was to assess pre-analytic measuring errors for paO(2) under the condition of hyperoxia as completely as possible and to work out solutions to eliminate these errors.METHODS:paO(2) analysis was performed on more than 2000 blood samples. Errors analyzed were the technique of sample taking (direct puncture or from an indwelling catheter), aspirated air bubbles (0.05-0.35 ml), time and temperature of sample storage, and the material, size and manufacturer of the analyzing syringe.RESULTS:The paO(2) was on average 41 mmHg lower in samples taken from the indwelling catheter than by direct puncture. An air bubble size of 0.1-0.25 ml caused a decrease of 17-41 mmHg. Storage time of 2 min accounted for an paO(2) reduction of 6-67 mmHg depending on the type of syringe used. Glass syringes turned out to be more accurate than plastic syringes. The best results were obtained not from commercial "blood gas syringes" but from a simple plastic injection syringe. For all pre-analytic errors correction factors were established.CONCLUSION:All pre-analytic errors investigated caused a significant paO(2) decrease. Even an ideal procedure (almost no air bubble, short storage on ice) contributes a significant error. Only the appropriate correction factors as calculated from this study for routine use lead to the correct results. If they are not taken into account the paO(2) values will be falsely low, potentially leading to misinterpretation and misjudgement of a patient's condition.

Objective: To ascertain whether there is a difference between total intravenous anaesthesia with propofol (P) and remifentanil (R) and inhalational anaesthesia with desflurane (D) and nitrous oxide (N) with regard to haemodynamic reactions, recovery profile and postoperative analgesic demand in patients scheduled for elective microsurgical vertebral disc resection.Methods: 50 patients (ASA I-II, 18-65 years) were randomly assigned to receive total intravenous anaesthesia with propofol and remifentanil or inhalational anaesthesia with desflurane and nitrous oxide. After standardised induction of anaesthesia in both groups (1 mu g . kg(-1) remifentanil, 1.5 mg . kg(-1) propofol, 0.1 mg . kg(-1) cisatracurium), anaesthesia was maintained in the D/N group with desflurane in 50% N(2)O. The patients of the P/R group received a constant infusion of 2 mg . kg(-1). h(-1) propofol and a constant infusion of 0.5 mu g . kg(-1). min(-1) remifentanil, which was reduced after 15 min by 50%. The administration of desflurane and the infusion of the anaesthetics were adjusted to maintain a surgical depth of anaesthesia. At the end of surgery the anaesthetics were discontinued and early emergence from anaesthesia was assessed by measuring time to spontaneous ventilation (V(T)>4 ml/kg), tracheal extubation,opening of the eyes and stating correct name and data of birth. The frequency of analgesics and total demand for analgesics were determined using patient-controlled analgesia and recorded for 2 h postoperatively. In addition the pain level of the patients was measured on a visual analogue scale and the incidence of postoperative shivering, nausea and vomiting was noted.Results: Patients anaesthetised with desflurane responded to tracheal intubation and skin incision with increasing blood pressure and showed higher heart rates than patients anaesthetised with propofol and remifentanil, but there were no other haemodynamic differences between the groups in response to surgical stimuli. There were significantly shorter times to spontaneous ventilation (3.2 vs. 6.3 min), extubation (3.8 vs. 9.5 min), eye opening (3.0 vs. 11.5 min) and giving name and date of birth (4.8 vs. 14.3 min) in patients anaesthetised with remifentanil and propofol than in those receiving desflurane and nitrous oxide. In addition, patients anaesthetised with remifentanil and propofol had a greater incidence of postoperative shivering. There were no significant differences between the two groups in the patients' pain scores, analgesic demand and incidence of nausea and vomiting.Conclusion: Patients anaesthetised with propofol and remifentanil have significantly shorter emergence times than patients anaesthetised with desflurane and nitrous oxide. The low incidence of postoperative pain after microsurgical vertebral disc resections requires no large-scale analgesic therapy, even after total intravenous anaesthesia including remifentanil.

Zusammenfassung Fragestellung: Unterscheidet sich eine totale intravenöse Anästhesie mit Propofol (P) und Remifentanil (R) von einer Inhalationsanästhesie mit Desfluran (D) und Lachgas (L) bei lumbalen Bandscheibenoperationen hinsichtlich der Steuerbarkeit der Narkose, der Beeinflussung hämodynamischer Parameter, des Aufwachverhaltens und des postoperativen Analgetikabedarfs der Patienten? Methodik: 50 Patienten (ASA I–II, 18–65 Jahre) wurden randomisiert entweder einer P/R- oder D/L-Gruppe zugeteilt. Nach standardisierter Narkoseeinleitung (1 µg/kg Remifentanil, 1,5 mg/kg Propofol, 0,1 mg/kg Cisatracurium) wurde die Anästhesie in der D/L-Gruppe bedarfsadaptiert mit Desfluran in 50% N 2 O und in der P/R-Gruppe mit 2 mg/kg/h Propofol und 0,5 µg/kg/min Remifentanil aufrechterhalten, wobei die Remifentanildosis nach 15 min halbiert wurde. Am Operationsende unmittelbar vor der Umlagerung in die horizontale Rückenlage wurde die Zufuhr der Anästhetika abrupt unterbrochen und folgende Aufwachzeiten erfaßt: Eintritt Spontanatmung (V T >4 ml/kg), Extubation, Augenöffnen, richtiges Benennen von Namen und Geburtsdatum und der Analgetikabedarf der ersten 2 postoperativen Stunden im Aufwachraum. Ergebnisse: Die Patienten der D/L-Gruppe reagierten auf den Intubationsreiz und die Hautinzision mit signifikanten Blutdruckanstiegen und zeigten signifikant höhere Herzfrequenzwerte, während ansonsten die hämodynamischen Parameter während des Narkoseverlaufs vergleichbar waren. Die Patienten der P/R-Gruppe erreichten signifikant früher eine stabile Spontanatmung (3,2 vs. 6,4 min), konnten früher extubiert werden (3,8 vs. 9,5 min), öffneten früher die Augen (3,0 vs. 11,5 min) und waren eher in der Lage, ihren Namen und Geburtsdatum zu benennen (4,8 vs. 14,3 min), wiesen aber auch signifikant häufiger Muskelzittern auf. Keine signifikanten Unterschiede fanden sich im Analgetikabedarf sowie in der Inzidenz von Übelkeit und Erbrechen. Schlußfolgerung: Die Patienten erwachen aus der TIVA mit Propofol/Remifentanil schneller als aus der Desfluran/N 2 O-Narkose und erreichen schneller ein höheres Vigilanzniveau, wobei die geringe Intensität postoperativer Wundschmerzen nach Bandscheibenoperationen kein aufwendiges Konzept zur postoperativen Analgesie erfordert.

OBJECTIVE:To ascertain whether there is a difference between total intravenous anaesthesia with propofol (P) and remifentanil (R) and inhalational anaesthesia with desflurane (D) and nitrous oxide (N) with regard to haemodynamic reactions, recovery profile and postoperative analgesic demand in patients scheduled for elective microsurgical vertebral disc resection.METHODS:50 patients (ASA I-II, 18-65 years) were randomly assigned to receive total intravenous anaesthesia with propofol and remifentanil or inhalational anaesthesia with desflurane and nitrous oxide. After standardised induction of anaesthesia in both groups (1 microgram.kg-1 remifentanil, 1.5 mg.kg-1 propofol 0.1 mg.kg-1 cisatracurium), anaesthesia was maintained in the D/N group with desflurane in 50% N2O. The patients of the P/R group received a constant infusion of 2 mg.kg-1.h-1 propofol and a constant infusion of 0.5 microgram.kg-1.min-1 remifentanil, which was reduced after 15 min by 50%. The administration of desflurane and the infusion of the anaesthetics were adjusted to maintain a surgical depth of anaesthesia. At the end of surgery the anaesthetics were discontinued and early emergence from anaesthesia was assessed by measuring time to spontaneous ventilation (VT > 4 ml/kg), tracheal extubation, opening of the eyes and stating correct name and data of birth. The frequency of analgesics and total demand for analgesics were determined using patient-controlled analgesia and recorded for 2 h postoperatively. In addition the pain level of the patients was measured on a visual analogue scale and the incidence of postoperative shivering, nausea and vomiting was noted.RESULTS:Patients anaesthetised with desflurane responded to tracheal intubation and skin incision with increasing blood pressure and showed higher heart rates than patients anaesthetised with propofol and remifentanil, but there were no other haemodynamic differences between the groups in response to surgical stimuli. There were significantly shorter times to spontaneous ventilation (3.2 vs. 6.3 min), extubation (3.8 vs. 9.5 min), eye opening (3.0 vs. 11.5 min) and giving name and date of birth (4.8 vs. 14.3 min) in patients anaesthetised with remifentanil and propofol than in those receiving desflurane and nitrous oxide. In addition, patients anaesthetised with remifentanil and propofol had a greater incidence of postoperative shivering. There were no significant differences between the two groups in the patients' pain scores, analgesic demand and incidence of nausea and vomiting.CONCLUSION:Patients anaesthetised with propofol and remifentanil have significantly shorter emergence times than patients anaesthetised with desflurane and nitrous oxide. The low incidence of postoperative pain after microsurgical vertebral disc resections requires no large-scale analgesic therapy, even after total intravenous anaesthesia including remifentanil.

Zusammenfassung Fragestellung: Moderne Biosensortechnologie ermöglicht die bettseitige Messung von Laktat ohne zeitliche Verzögerung. Bisherige Verfahren waren durch methodische Einschränkungen oder relevante Ungenauigkeit limitiert. Ziel vorliegender Untersuchung war zu prüfen, welche Genauigkeit mit einem neuen, direkt messenden Gerät (Chiron Diagnostics) und einem überarbeiteten bestehenden Biosensorverfahren (NOVA Biomedical) derzeit zu erreichen ist. Methodik: Untersucht wurden die Geräte „System 860” (Chiron Diagnostics) und „StatProfile 9” (NOVA Biomedical) im Vergleich zu einem etablierten photometrischen Verfahren (Analyticon). Messungen erfolgten mit 9 verschiedenen Biosensoren beider Hersteller in Zitratblut und Frischplasma als Doppelbestimmungen ( n =1120), vor und nach Zugabe definierter Mengen 1molarer Na-Laktatlösung (2–24 mmol/l) sowie in kommerziell erhältlichen Qualitätskontrollösungen über einen Zeitraum von 60 Tagen. Ergebnisse: Die Reproduzierbarkeit betrug in Zitratblut 2,6±2,8% (Chiron), 4,1±4,0% (NOVA) und 1,5±2,1% (Analyticon), in Plasma entsprechend 2,1±2,4%, 2,1±2,9% und 1,0±1,1%. Die Präzision von Tag zu Tag ergab Variationskoeffizienten von im Mittel 11,5±4,9% (Chiron) und 14,0±5,9% (NOVA). Die mittlere Meßabweichung betrug für Chiron –0,2±16,4% (Plasma) und +7,2±13,1% (Zitratblut), für NOVA +9,4±18,4% und +18,7±16,7% sowie für Analyticon –37,8± 18,2% und –27,5±17,6%. Schlußfolgerungen: Das Hauptproblem der Laktatmessung mit Biosensoren ist neben der Meßungenauigkeit (im Mittel 0–18%) und dem Lebensalter der Sensoren die Größe des zufälligen Fehlers (im Mittel 13–18%). Trotz adäquat durchgeführter interner und externer Qualitätskontrollen ist es für den Anwender nicht vorhersehbar, wie sehr der angezeigte Wert von der tatsächlichen Laktatkonzentration nach oben oder unten abweicht. Folglich dürfen Absolutwerte der Laktatkonzentration nur mit Vorsicht interpretiert werden und sind zusammen mit anderen klinischen Parametern eher für die Beurteilung eines Verlaufs geeignet als für die konkrete Einschätzung des aktuellen klinischen Zustands.