[Perioperative antibiotic prophylaxis]. / Perioperative Antibiotikaprophylaxe.

In times of growing bacterial resistance against antimicrobiotic drugs the broad prescription of antibiotics in human medicine must be carefully considered. The perioperative antibiotic treatment is in the center of that conflict. On the one hand an efficient pathogen reduction for the preemptive treatment of infectious complications is desired but on the other hand it is suspected that this promotes the selection of multiresistant pathogens which could lead to an increase of more complicated nosocomial infections. The aim of this article is a critical appraisal of this subject on the basis of the 2012 guidelines of the German working group of Hygiene in Hospital and Practice (AWMF) and the 2010 recommendations of the Paul-Ehrlich-Gesellschaft.

Changes in sevoflurane plasma concentration with delivery through the oxygenator during on-pump cardiac surgery.

BACKGROUND: It is unclear what factors affect the uptake of sevoflurane administered through the membrane oxygenator during cardiopulmonary bypass (CPB) and whether this can be monitored via the oxygenator exhaust gas. METHODS: Stable delivery of sevoflurane was administered to 30 elective cardiac surgery patients at 1.8 vol% (inspiratory) via the anaesthetic circuit and ventilator. During CPB, sevoflurane was administered in the oxygenator fresh gas supply (Compactflo Evolution™; Sorin Group, Milano, Italy). Sevoflurane plasma concentration (SPC) was measured using gas chromatography. Changes were correlated with bispectral index (BIS), patient temperature, haematocrit, plasma albumin concentration, oxygenator fresh gas flow, and the sevoflurane concentration in the oxygenator exhaust at predefined time points. RESULTS: The mean SPC pre-bypass was 54.9 µg ml(-1) [95% confidence interval (CI): 50.6-59.1]. SPC decreased to 43.2 µg ml(-1) (95% CI: 40.3-46.1; P<0.001) after initiation of CPB, and was lower still during rewarming and weaning from bypass, 39.4 µg ml(-1) (95% CI: 36.6-42.3; P<0.001). BIS did not exceed a value of 55. SPCs were higher during hypothermia (P<0.001) and with an increase in oxygenator fresh gas flow (P=0.015), and lower with haemodilution (P=0.027). No correlation was found between SPC and the concentration of sevoflurane in the oxygenator exhaust gas (r=-0.04; 95% CI: -0.18 to 0.09; P=0.53). CONCLUSIONS: The uptake of sevoflurane delivered via the membrane oxygenator during CPB seems to be affected by hypothermia, haemodilution, and changes in the oxygenator fresh gas supply flow. Measuring the concentration of sevoflurane in the exhaust from the oxygenator is not useful for monitoring sevoflurane administration during bypass.

Comparison of values in critically ill patients for global end-diastolic volume and extravascular lung water measured by transcardiopulmonary thermodilution: A metaanalysis of the literature

Introduction: Hemodynamic parameters such as the global end-diastolic volume index (GEDVI) and extravascular lung water index (EVLWI), derived by transpulmonary thermodilution, have gained increasing interest for guiding fluid therapy in critically ill patients. The proposed normal values (680-800ml/m2 for GEDVI and 3-7ml/kg for EVLWI) are based on measurements in healthy individuals and on expert opinion, and are assumed to be suitable for all patients. We analyzed the published data for GEDVI and EVLWI, and investigated the differences between a cohort of septic patients (SEP) and patients undergoing major surgery (SURG), respectively. Methods: A PubMed literature search for GEDVI, EVLWI or transcardiopulmonary single/double indicator thermodilution was carried out, covering the period from 1990 to 2010. Intervention: Meta-regression analysis was performed to identify any differences between the surgical (SURG) and non-surgical septic groups (SEP). Results: Data from 1925 patients corresponding to 64 studies were included. On comparing both groups, mean GEDVI was significantly higher by 94ml/m2 (95%CI: [54; 134]) in SEP compared to SURG patients (788ml/m2 95%CI: [762; 816], vs. 694ml/m2, 95%CI: [678; 711], p<0.001). Mean EVLWI also differed significantly by 3.3ml/kg (95%CI: [1.4; 5.2], SURG 7.2ml/kg, 95%CI: [6.9; 7.6] vs. SEP 11.0ml/kg, 95%CI: [9.1; 13.0], p=0.001).Conclusions: The published data for GEDVI and EVLWI are heterogeneous, particularly in critically ill patients, and often exceed the proposed normal values derived from healthy individuals. In the group of septic patients, GEDVI and EVLWI were significantly higher than in the group of patients undergoing major surgery. This points to the need for defining different therapeutic targets for different patient populations (AU)

Introducción: Parámetros hemodinámicos como el índice de volumen diastólico final global (GEDVI) y el índice de agua pulmonar extravascular (EVLWI), obtenidos mediante termodilución transpulmonar, suscitan un interés creciente como guía de la terapia de fluidos en pacientes críticamente enfermos. Los valores normales propuestos (680-800ml/m2 para el GEDVI y 3-7ml/kg para el EVLWI) se basan en mediciones realizadas a individuos sanos y en la opinión de expertos, y se asume que son adecuados para todos los pacientes. Analizamos los datos publicados sobre el GEDVI y el EVLWI e investigamos las diferencias entre una cohorte de pacientes septicémicos (SEP) y pacientes sometidos a cirugía mayor (SURG) respectivamente. Métodos: Se realizó una búsqueda bibliográfica en PubMed de GEDVI, EVLWI o termodilución trasncardiopulmonar de indicador único/doble referida al periodo comprendido entre 1990 y 2010. Intervenciones: Se realizó un análisis de metarregresión para identificar las diferencias entre los grupos quirúrgico (SURG) y no quirúrgico septicémico (SEP). Resultados: Se incluyeron los datos de 1925 pacientes correspondientes a 64 estudios. Al comparar ambos grupos, el GEDVI medio resultó ser significativamente (..) (AU)

[Intraoperative electrophysiological monitoring with evoked potentials]. / Intraoperatives elektrophysiologisches Monitoring mit evozierten Potenzialen.

During the last 30 years intraoperative electrophysiological monitoring (IOEM) has gained increasing importance in monitoring the function of neuronal structures and the intraoperative detection of impending new neurological deficits. The use of IOEM could reduce the incidence of postoperative neurological deficits after various surgical procedures. Motor evoked potentials (MEP) seem to be superior to other methods for many indications regarding monitoring of the central nervous system. During the application of IOEM general anesthesia should be provided by total intravenous anesthesia with propofol with an emphasis on a continuous high opioid dosage. When intraoperative MEP or electromyography guidance is planned, muscle relaxation must be either completely omitted or maintained in a titrated dose range in a steady state. The IOEM can be performed by surgeons, neurologists and neurophysiologists or increasingly more by anesthesiologists. However, to guarantee a safe application and interpretation, sufficient knowledge of the effects of the surgical procedure and pharmacological and physiological influences on the neurophysiological findings are indispensable.

Effects of one-lung ventilation on thermodilution-derived assessment of cardiac output.

BACKGROUND: Cardiac output (CO) monitoring can be useful in high-risk patients during one-lung ventilation (OLV), but it is unclear whether thermodilution-derived CO monitoring is valid during OLV. Therefore, we compared pulmonary artery (CO(PATD)) and transcardiopulmonary thermodilution (CO(TPTD)) with an experimental reference in a porcine model. METHODS: CO(PATD) and CO(TPTD) were measured in 23 pigs during double-lung ventilation (DLV) and 15 min after the onset of OLV, during conditions of normovolaemia and after haemorrhage. An ultrasonic flow probe placed around the pulmonary artery (CO(PAFP)) was used for reference. RESULTS: The range of CO in these experiments was 1.5-3 litre min(-1). Normovolaemia: during DLV and conditions of normovolaemia, the mean (95% limits of agreement) bias for CO(PATD) compared with CO(PAFP) was -0.05 (-0.92 and 0.83) litre min(-1), and 0.58 (-0.40 and 1.55) litre min(-1) for CO(TPTD). During OLV, the bias for CO(PATD) remained unchanged at 0.08 (-0.51 and 0.66) litre min(-1), P=0.15, and the bias for CO(TPTD) increased significantly to 0.85 (0.05 and 1.64) litre min(-1), P=0.047. Hypovolaemia: during DLV, the bias for CO(PATD) compared with CO(PAFP) was 0.22 (-0.20 and 0.66) litre min(-1) and for CO(TPTD) was 0.60 (0.12 and 1.10) litre min(-1). There was no significant change of bias during OLV for CO(PATD) [0.30 (-0.10 and 0.70) (litre min(-1)), P=0.25] or bias CO(TPTD) [0.72 (0.21 and 1.22) (litre min(-1)), P=0.14]. Trending ability during OLV, quantified by the mean of angles θ, showed good values for both CO(PATD) (θ=11.2°) and CO(TPTD) (θ=1.3°). CONCLUSIONS: CO(TPTD) is, to some extent, affected by OLV, whereas CO(PATD) is unchanged. Nonetheless, both methods provide an acceptable estimation of CO and particularly of relative changes of CO during OLV.

Comparison of values in critically ill patients for global end-diastolic volume and extravascular lung water measured by transcardiopulmonary thermodilution: a meta-analysis of the literature.

INTRODUCTION: Hemodynamic parameters such as the global end-diastolic volume index (GEDVI) and extravascular lung water index (EVLWI), derived by transpulmonary thermodilution, have gained increasing interest for guiding fluid therapy in critically ill patients. The proposed normal values (680-800ml/m(2) for GEDVI and 3-7ml/kg for EVLWI) are based on measurements in healthy individuals and on expert opinion, and are assumed to be suitable for all patients. We analyzed the published data for GEDVI and EVLWI, and investigated the differences between a cohort of septic patients (SEP) and patients undergoing major surgery (SURG), respectively. METHODS: A PubMed literature search for GEDVI, EVLWI or transcardiopulmonary single/double indicator thermodilution was carried out, covering the period from 1990 to 2010. INTERVENTION: Meta-regression analysis was performed to identify any differences between the surgical (SURG) and non-surgical septic groups (SEP). RESULTS: Data from 1925 patients corresponding to 64 studies were included. On comparing both groups, mean GEDVI was significantly higher by 94ml/m(2) (95%CI: [54; 134]) in SEP compared to SURG patients (788ml/m(2) 95%CI: [762; 816], vs. 694ml/m(2), 95%CI: [678; 711], p<0.001). Mean EVLWI also differed significantly by 3.3ml/kg (95%CI: [1.4; 5.2], SURG 7.2ml/kg, 95%CI: [6.9; 7.6] vs. SEP 11.0ml/kg, 95%CI: [9.1; 13.0], p=0.001). CONCLUSIONS: The published data for GEDVI and EVLWI are heterogeneous, particularly in critically ill patients, and often exceed the proposed normal values derived from healthy individuals. In the group of septic patients, GEDVI and EVLWI were significantly higher than in the group of patients undergoing major surgery. This points to the need for defining different therapeutic targets for different patient populations.

Respiratory systolic variation test in acutely impaired cardiac function for predicting volume responsiveness in pigs.

BACKGROUND: Predicting the response of cardiac output (CO) to volume administration remains difficult, in particular in patients with acutely compromised cardiac function, where, even small amounts of i.v. fluids can lead to volume overload. We compared the ability to predict volume responsiveness of different functional haemodynamic parameters, such as pulse pressure variation (PPV), stroke volume variation (SVV), the static preload parameter right atrial pressure (RAP), and global end-diastolic volume (GEDV) with the recently proposed respiratory systolic variation test (RSVT) in acutely impaired cardiac function. METHODS: In 13 mechanically ventilated pigs, cardiac function was acutely reduced by continuous application of verapamil to reach a decrease in peak change of left ventricular pressure over time (dP/dt) of 50%. After withdrawal of 20 ml kg(-1) BW blood to establish hypovolaemia, four volume loading steps of 7 ml kg(-1) BW using the shed blood and 6% hydroxyethylstarch 130/0.4 were performed. Volume responsiveness was considered as positive, if CO increased more than 10%. RESULTS: Receiver operating characteristic curve analysis revealed an area under the curve (AUC) of 0.88 for the RSVT, 0.84 for PPV, 0.82 for SVV, 0.78 for RAP, and 0.77 for GEDV. CONCLUSIONS: Functional parameters of cardiac preload, including the RSVT, allow prediction of fluid responsiveness in an experimental model of acutely impaired cardiac function.

[Accuracy of pulse contour cardiac index measurements during changes of preload and aortic impedance]. / Arterielle Pulskonturanalyse zur Messung des Herzindex unter Veränderungen der Vorlast und der aortalen Impedanz.

BACKGROUND: Cardiac index obtained by arterial pulse contour analysis (CI(PC)) demonstrated good agreement with arterial or pulmonary arterial thermodilution derived cardiac index (CI(TD), CI(PA)) in cardiac surgical or critically ill patients. However as the accuracy of pulse contour analysis during changes of the aortic impedance is unclear, we compared CI(PC), CI(TD) and CI(PA) during changes of preload and the aortic impedance as occurring during sternotomy. PATIENTS AND METHODS: CI(PC) und CI(TD), were compared in 28 patients, (and CI(PA) in 6 patients) undergoing elective coronary artery bypass grafting, before and after sternotomy. The relative changes DeltaCI(PC) und DeltaCI(PC) were calculated. RESULTS: Sternotomy resulted in a significant increase in CI in 25 out of 28 patients. Regression analysis was performed between CI(PC) and CI(TD) before and after sternotomy (r(2) = 0.87, p<0.0001, r(2) = 0.88, p<0.0001) as well as between CI(PC) and CI(PA), before and after sternotomy (r(2) = 0.85, p<0.0001, r(2) = 0.93, p<0.01) and between DeltaCI(PC) and DeltaCI(TD) (r(2) = 0.72, p<0.0001). Bland Altman-Analysis for determining bias (m) and precision (2SD) between CI(PC) and CI(TD) before and after sternotomy and between DeltaCI(PC) and DeltaCI(TD) resulted in m = -0.03 L/min/m(2), 2SD = -0.34 to 0.28 L/min/m(2), m = -0.06 L/min/m(2), 2SD = -0.45 to 0.33 L/min/m(2) and m = -0.02 L/min/m(2), SD = -0.47 to 0.44 L/min/m(2). CONCLUSION: Pulse contour analysis derived CI(PC) accurately reflects thermodilution derived CI(TD) or CI(PA) during changes of preload and the aortic impedance as occurring during sternotomy.

Assessing fluid responsiveness during open chest conditions.

BACKGROUND: Measurement of ventilation-induced left ventricular stroke volume variations (SVV) or pulse pressure variations (PPV) is useful to optimize preload in patients after cardiac surgery. The aim of this study was to investigate the ability of SVV and PPV measured by arterial pulse contour analysis to assess fluid responsiveness in patients undergoing coronary artery bypass surgery during open-chest conditions. METHODS: We studied 22 patients immediately after midline sternotomy. We determined SVV, PPV, left ventricular end-diastolic area index by transoesophageal echocardiography, global end-diastolic volume index and cardiac index by thermodilution before and after removal of blood 500 ml and after volume substitution with hydroxyethyl starch 6%, 500 ml. RESULTS: Blood removal resulted in a significant increase in SVV from 6.7 (2.2) to 12.7 (3.8)%. PPV increased from 5.2 (2.5) to 11.9 (4.6)% (both P<0.001). Cardiac index decreased from 2.9 (0.6) to 2.3 (0.5) litres min(-1) m(-2) and global end-diastolic volume index decreased from 650 (98) to 565 (98) ml m(-2) (both P<0.025). Left ventricular end-diastolic area index did not change significantly. After fluid loading SVV decreased significantly to 6.8 (2.2)% and PPV decreased to 5.4 (2.1)% (both P<0.001). Concomitantly, cardiac index increased significantly to 3.3 (0.5) litres min(-1) m(-2) (P<0.001) and global end-diastolic volume index increased significantly to 663 (104) ml m(-2) (P<0.005). Left ventricular end-diastolic area index did not change significantly. We found a significant correlation between the increase in cardiac index caused by fluid loading and SVV as well as PPV before fluid loading (SVV, R=0.74, P<0.001; PPV, R=0.61, P<0.005). No correlations were found between values of global end-diastolic volume index or left ventricular end-diastolic area index before fluid loading and the increase in cardiac index. CONCLUSION: Measurement of SVV or PPV allows assessment of fluid responsiveness in hypovolaemic patients under open-chest and open-pericardium conditions. Thus, measuring heart-lung interactions may improve haemodynamic management during surgical procedures requiring mid-line sternotomy.

Effects of mid-line thoracotomy on the interaction between mechanical ventilation and cardiac filling during cardiac surgery.

BACKGROUND: Mid-line thoracotomy is a standard approach for cardiac surgery. However, little is known how this surgical approach affects the interaction between the circulation and mechanical ventilation. We studied how mid-line thoracotomy affects cardiac filling volumes and cardiovascular haemodynamics, particularly variations in stroke volume and pulse pressure caused by mechanical ventilation. METHODS: We studied 19 patients during elective coronary artery bypass surgery. Before and after mid-line thoracotomy, we measured arterial pressure, cardiac index (CI) and global end-diastolic volume index (GEDVI) by thermodilution, left ventricular end-diastolic area index (LVEDAI) by transoesophageal echocardiography and the variations in left ventricular stroke volume and pulse pressure during ventilation by arterial pulse contour analysis. RESULTS: After thoracotomy, CI increased from 2.3 (0.4) to 2.9 (0.6) litre min(-1) m(-2), GEDVI increased from 605 (110) to 640 (94) litre min(-1) m(-2), and LVEDAI increased from 9.2 (3.7) to 11.2 (4.1) cm(2) m(-2). All these changes were significant. In contrast, stroke volume variation (SVV) decreased from 10 (3) to 6 (2)% and pulse pressure variation (PPV) decreased from 11 (3) to 5 (3)%. Before thoracotomy, SVV and PPV significantly correlated with GEDVI (both P<0.01). When the chest was open, similar significant correlations of SVV (P<0.001) and PPV (P<0.01) were found with GEDVI. CONCLUSION: Thoracotomy increases cardiac filling and preload. Further, thoracotomy reduces the effect of mechanical ventilation on left ventricular stroke volume. However, also under open chest conditions, SVV and PPV are preload-dependent.