F. Mielck

Effects of one minimum alveolar anesthetic concentration sevoflurane on cerebral metabolism, blood flow, and CO2 reactivity in cardiac patients.

UNLABELLED We investigated the cerebral hemodynamic effects of 1 minimum alveolar anesthetic concentration (MAC) sevoflurane anesthesia in nine male patients scheduled for elective coronary bypass grafting. For measurement of cerebral blood flow (CBF), a modified Kety-Schmidt saturation technique was used with argon as an inert tracer gas. Measurements of CBF were performed before the induction of anesthesia and 30 min after induction under normocapnic, hypocapnic, and hypercapnic conditions. Compared with the awake state under normocapnic conditions, sevoflurane reduced the mean cerebral metabolic rate of oxygen by 47% and the mean cerebral metabolic rate of glucose by 39%. Concomitantly, CBF was reduced by 38%, although mean arterial pressure was kept constant. Significant changes in jugular venous oxygen saturation were absent. Hypocapnia and hypercapnia caused a 51% decrease and a 58% increase in CBF, respectively. These changes in CBF caused by variation of Paco2 indicate that cerebrovascular CO2 reactivity persists during 1 MAC sevoflurane anesthesia. IMPLICATIONS We used a modified Kety-Schmidt saturation technique to investigate the effects of 1 minimum alveolar anesthetic concentration (MAC) sevoflurane on cerebral blood flow, metabolism, and CO2 reactivity in cardiac patients. We found that the global cerebral blood flow and global cerebral metabolic rate of oxygen remained coupled and that cerebrovascular CO2 reactivity is not impaired by the administration of 1 MAC sevoflurane.

Bedside Assessment of Cerebral Blood Flow by Double-indicator Dilution Technique

Background Currently, quantitative measurement of global cerebral blood flow (CBF) at bedside is not widely performed. The aim of the present study was to evaluate a newly developed method for bedside measurement of CBF based on thermodilution in a clinical setting. Methods The investigation was performed in 14 anesthetized patients before coronary bypass surgery. CBF was altered by hypocapnia, normocapnia, and hypercapnia. CBF was measured simultaneously by the Kety-Schmidt inert-gas technique with argon and a newly developed transcerebral double-indicator dilution technique (TCID). For TCID, bolus injections of ice-cold indocyanine green were performed via a central venous line, and the resulting thermo-dye dilution curves were recorded simultaneously in the aorta and the jugular bulb using combined fiberoptic thermistor catheters. CBF was calculated from the mean transit times of the indicators through the brain. Results Both methods of measurement of CBF indicate a decrease during hypocapnia and an increase during hypercapnia, whereas cerebral metabolic rate remained unchanged. Bias between CBFTCID and CBFargon was −7.1 ± 2.2 (SEM) ml · min−1 · 100 g−1; precision (± 2 · SD of differences) between methods was 26.6 ml · min−1 · 100 g−1. Conclusions In the clinical setting, TCID was feasible and less time-consuming than alternative methods. The authors conclude that TCID is an alternative method to measure global CBF at bedside and offers a new opportunity to monitor cerebral perfusion of patients.

Cerebral inflammatory response during and after cardiac surgery.

Background and objective: Neurological dysfunction is a common problem after cardiac surgery with cardiopulmonary bypass (CPB). Cerebral ischaemia associated with the use of CPB may result in a release of neuronal‐ischaemic markers and a subsequent cerebral inflammatory response which may additionally release inflammatory cytokines. In order to locate the origin and to quantify the release of neuronal‐ischaemic markers and cytokines we investigated arterial‐cerebral venous concentration gradients during and after CPB in a clinical setting. Methods: In twenty‐five patients scheduled for coronary artery bypass grafting surgery we measured the plasma concentration of neuron‐specific enolase, S‐100&bgr; protein as well as interleukins (IL) IL‐6, IL‐8 and IL‐10 from arterial and cerebral venous blood samples prior to surgery (baseline), during hypothermic CPB at 32°C, after termination of bypass, as well as 2, 4 and 6 h after admission to the intensive care unit. Results: Arterial‐cerebral venous concentration gradients of neuron‐specific enolase, S‐100&bgr;, IL‐6, IL‐8 and IL‐10 were neither detectable during nor after CPB. Compared to the baseline period, S‐100&bgr; and neuron‐specific enolase significantly increased during hypothermic CPB. After termination of CPB, neuronal‐ischaemic markers as well as cytokines were increased and remained elevated during the investigated time course without reaching baseline values. Conclusions: Although we found an overall increase in plasma concentrations of neuronal‐ischaemic markers, IL‐6, IL‐8 and IL‐10 during and after CPB, arterial‐cerebral venous gradients were not detectable for any of these parameters. Our results suggest that the increase of investigated parameters associated with the use of CPB are not primarily caused by a cerebral inflammatory response but rather reflect a release from other sources in the systemic circulation.

Messung der menschlichen Hirndurchblutung

ZusammenfassungIn der vorliegenden Untersuchung wurde die Hirndurchblutung simultan sowohl mit der intravenösen 133Xenon-Clearancetechnik als auch mit der Kety-Schmidt-Technik gemessen. Unter Standardanästhesiebedingungen wurden Hirndurchblutung, zerebraler Stoffwechsel und die CO2-Reaktivität der Hirndurchblutung miteinander verglichen. Untersucht wurden 13 männliche Patienten, unmittelbar bevor sie sich einer aortokoronaren Bypassoperation unterzogen. Die Hirndurchblutungsmessungen wurden simultan durchgeführt und zwar jeweils unter normokapnischen (paCO2 43±3 mm Hg), hypokapnischen (paCO2 31±3 mm Hg) und hyperkapnischen (paCO2 54±4 mm Hg) Bedingungen. Mit der Xenonmethode wurden unter allen Ventilationsbedingungen signifikant niedrigere Hirndurchblutungswerte gemessen als mit der Kety-Schmidt-Technik. Eine signifikante Korrelation zwischen den Hirndurchblutungswerten beider Methoden wurde nicht gefunden (y=1,82x−8,58, r=0,76, p=0,357). Die CO2-Antwortkurven der Hirndurchblutung zeigten für beide Verfahren einen exponentiellen Verlauf. Die CO2-Reaktivität war jedoch bei der Kety-Schmidt-Technik deutlichgrößer als bei der Xenonmethode (y=8,14e0,039xvs. y=10,75 e0,023x). Wahrscheinlich aufgrund einer Miterfassung langsam perfundierter extrazerebraler Areale ist die intravenöse Xenonmethode unter Verwendung von CBF15 als Durchblutungsparameter mit einer deutlichen Unterschätzung von Hirndurchblutung, -stoffwechsel und zerebrovaskulärer CO2-Reaktivität behaftet.AbstractIn this study cerebral blood flow (CBF) was simultaneously measured with the Kety-Schmidt method and the intravenous 133Xe clearance technique. CBF, cerebral metabolic rate of oxygen (CMRO2), and CO2 reactivity of CBF were compared under fentanyl-midazolam anaesthesia and varying paCO2 levels. Methods. Thirteen male patients were studied before they underwent coronary artery bypass surgery. For measurement of CBF with the Kety-Schmidt inert gas saturation technique, argon was used as indicator instead of nitrous oxide, because argon is less soluble in water and lipid such that arterial and hence organ saturation is attained earlier. Wash-in periods of 10 min were used for all measurements. For measurement of CBF with the intravenous xenon method 10 scintillation detectors placed lateral to the skull and an air detector for calculation of tracer recirculation were used. 10–15 mCi of 133Xe dissolved in physiological saline was injected via a peripheral i.v. cannula. For comparison with the Kety-Schmidt technique CBF15-values representing the flow of the grey and white matter were chosen. CBF was measured simultaneously with both methods under normocapnic (paCO2 43±3 mmHg), hypocapnic (paCO2 31±3 mmHg), and under hypercapnic (paCO2 54±4 mmHg) conditions. Results. All CBF15 values obtained with the intravenous xenon method were significantly lower than the corresponding CBF-values measured with the Kety-Schmidt technique: by 36% under normocapnic, 23% under hypocapnic, and 39% under hypercapnic conditions, respectively. Hence, CMRO2 values calculated from CBF values obtained with the xenon method were reduced to about the same degree as those derived from CBF values measured with the Kety-Schmidt technique. There was no significant correlation between the CBF values of either method (y=1.82x−8.58,r=0.76 P=0.357). Non-linear curve-fitting procedures yielded exponential CBF−paCO2 relationships for both methods, although the relative carbon dioxide reactivity was higher with the Kety-Schmidt technique than with the xenon method (y=8.14 e0.039x vs y=10,75 e0.023x). Conclusions. Most probably due to contamination with radioactivity from slowly perfused extracerebral tissues the intravenous 133Xe-clearance technique underestimates CBF, CMRO2, and cerebrovascular CO2 reactivity, at least when CBF15 values are used as flow parameters.

Is cerebral venous oxygen saturation an indicator of cerebral circulation

ZusammenfassungIn der klinischen Routine stellt die Bestimmung der Hirndurchblutung häufig ein Problem dar. Leichter meßbar ist die arteriovenöse Sauerstoffgehaltsdifferenz (avDO2) des Gehirns, die abhängig ist von dessen O2-Verbrauch (CMRO2) und dem zerebralen Blutfluß (CBF). Bei gleichbleibendem Sauerstoffangebot ist die avDO2 umgekehrt proportional zur hirnvenösen O2-Sättigung (ShvO2). Damit erlaubt die Bestimmung der hirnvenösen Sättigung nicht nur eine Aussage über die Sauerstoffausschöpfung des Gehirns, sondern könnte bei einer konstanten O2-Aufnahme eine Einschätzung des CBF ermöglichen. In der vorliegenden Untersuchung wurde an 62 männlichen Patienten im Alter von 41–60 Jahren im Rahmen von aorto-koronaren Bypassoperationen dieser Zusammenhang untersucht. Zu vier definierten Meßpunkten wurden die arterielle und hirnvenöse Sauerstoffsättigung sowie die zerebrale Durchblutung gemessen. Die erhaltenen Werte wurden gepoolt. Es konnte eine lineare Abhängigkeit zwischen der avDO2 und ShvO2 bestätigt werden; eine hinreichend enge Verknüpfung zwischen ShvO2 und CBF lag unter diesen klinischen Bedingungen jedoch nicht vor. Die Ursache lag in der hohen Variabilität des CMRO2. Ohne Kenntnis der CMRO2 dürfen aus Sättigungsänderungen keine Rückschlüsse auf perioperative Veränderungen der Hirndurchblutung gezogen werden.AbstractThe arteriovenous oxygen content difference (avDO2) of the brain is dependent on O2 consumption (CMRO2) and cerebral blood flow (CBF). With unchanging arterial O2 content, avDO2 is inversely related to cerebral venous O2 saturation (SO2). Measurement of SO2 in the jugular bulb not only provides information about the O2 balance of the brain, but may give an important estimation of CBF if a clinically useful correlation is proven. The aim of the present study was to verify this aspect. Methods. Sixty-two male patients undergoing coronary revascularisation were investigated. The study was approved by the local Ethical Committee and each patient gave written informed consent on the preoperative day. At four points during the perioperative course arterial and cerebral venous SO2 and CBF were measured. Cerebral venous blood was sampled from a catheter in the superior bulb of the right internal jugular vein. CBF was measured using the argon wash-in technique. All sampled data were pooled and evaluated. Results. As expected from theory, cerebral venous SO2 and avDO2 showed a close linear relationship (r=−0.892). However, only a weak hyperbolic relationship was found between cerebral venous SO2 and CBF. In addition, no direct correlation between CMRO2 and SO2 in the jugular bulb could be demonstrated. Conclusions. In this clinical study, a close relationship between cerebral venous SO2 and CBF was not found. This was primarily due to the high variability of cerebral O2 uptake. Changes in cerebral venous SO2 may therefore not be used as an estimate of perioperative changes in CBF.

[Acute myocardial infarction--special aspects for anesthetists].

Zusammenfassung. Patienten nach akutem Myokardinfarkt und mit einem erhöhten perioperativen Risiko bei bestehender koronarer Herzkrankheit stellen eine besondere Herausforderung für den klinisch tätigen Anästhesisten dar. Insbesondere für die präoperative Diagnostik, Festlegung des Operationszeitpunktes und postoperative Überwachung und Therapie sind enge Absprachen mit Hausarzt, operativen Kollegen und Internist notwendig. Deutlich verbessertes intraoperatives Monitoring und hämodynamisches Management von Patienten mit hohem kardialen Risiko führt erst durch optimiertes postoperatives Vorgehen zur deutlichen Abnahme der Inzidenz myokardialer Ischämien und letztlich der kardialen Morbidität.

Implementierung eines neuen Schockraumprotokolls an einem Universitätsklinikum in Deutschland@@@Implementation of a new emergency room protocol at a University Medical Center in Germany: Grundlage für einen verbesserten Informationsfluss, adäquates Qualitätsmanagement und wissenschaftliche Auswertungen@@@Basis for improved flow of information, adequate quality management and scientific assessment

BACKGROUND After analyzing the existing documentation protocol for the emergency room (ER), the department of anesthesiology of the Medical University of Göttingen (UMG) developed a new department-specific ER protocol. AIM The objective was to improve the flow of patient information from the preclinical situation through the emergency room to the early inpatient period. With this in mind a new emergency protocol was developed that encompasses the very heterogeneic patient collective in the ER as well as forming a basis for quality management and scientific investigation, taking user friendliness and efficiency into consideration. MATERIAL AND METHODS A strategical development of a new emergency room protocol is represented, which was realized using a self-developed 8-step approach. Technical support and realization was carried out using the Scribus 1.4.2 open source desktop and GIMP 2.8.4 GNU image manipulation graphic programs. RESULTS The new emergency room protocol was developed based on scientific knowledge and defined targets. The following 13 sections represent the contents of the new protocol: general characteristics, emergency event, initial findings and interventions, vital parameters, injury pattern, vascular access, hemodynamics, hemogram/blood gas analysis (BGA), coagulopathy, diagnostics, emergency interventions, termination of ER treatment and final evaluation. CONCLUSION The structured and elaborated documentation was limited to the target of two sides and succeeds in incorporating trauma patients as well as non-trauma patients in the ER.

[Erratum to: Implementation of a new emergency room protocol at a University Medical Center in Germany : Basis for improved flow of information, adequate quality management and scientific assessment].

BACKGROUND After analyzing the existing documentation protocol for the emergency room (ER), the department of anesthesiology of the Medical University of Göttingen (UMG) developed a new department-specific ER protocol. AIM The objective was to improve the flow of patient information from the preclinical situation through the emergency room to the early inpatient period. With this in mind a new emergency protocol was developed that encompasses the very heterogeneic patient collective in the ER as well as forming a basis for quality management and scientific investigation, taking user friendliness and efficiency into consideration. MATERIAL AND METHODS A strategical development of a new emergency room protocol is represented, which was realized using a self-developed 8-step approach. Technical support and realization was carried out using the Scribus 1.4.2 open source desktop and GIMP 2.8.4 GNU image manipulation graphic programs. RESULTS The new emergency room protocol was developed based on scientific knowledge and defined targets. The following 13 sections represent the contents of the new protocol: general characteristics, emergency event, initial findings and interventions, vital parameters, injury pattern, vascular access, hemodynamics, hemogram/blood gas analysis (BGA), coagulopathy, diagnostics, emergency interventions, termination of ER treatment and final evaluation. CONCLUSION The structured and elaborated documentation was limited to the target of two sides and succeeds in incorporating trauma patients as well as non-trauma patients in the ER.

Implementierung eines neuen Schockraumprotokolls an einem Universitätsklinikum in Deutschland

BACKGROUND After analyzing the existing documentation protocol for the emergency room (ER), the department of anesthesiology of the Medical University of Göttingen (UMG) developed a new department-specific ER protocol. AIM The objective was to improve the flow of patient information from the preclinical situation through the emergency room to the early inpatient period. With this in mind a new emergency protocol was developed that encompasses the very heterogeneic patient collective in the ER as well as forming a basis for quality management and scientific investigation, taking user friendliness and efficiency into consideration. MATERIAL AND METHODS A strategical development of a new emergency room protocol is represented, which was realized using a self-developed 8-step approach. Technical support and realization was carried out using the Scribus 1.4.2 open source desktop and GIMP 2.8.4 GNU image manipulation graphic programs. RESULTS The new emergency room protocol was developed based on scientific knowledge and defined targets. The following 13 sections represent the contents of the new protocol: general characteristics, emergency event, initial findings and interventions, vital parameters, injury pattern, vascular access, hemodynamics, hemogram/blood gas analysis (BGA), coagulopathy, diagnostics, emergency interventions, termination of ER treatment and final evaluation. CONCLUSION The structured and elaborated documentation was limited to the target of two sides and succeeds in incorporating trauma patients as well as non-trauma patients in the ER.

Possibilities of neuromonitoring in cardiac surgery with cardiopulmonary bypass

Zusammenfassung Patienten nach kardiochirurgischen Eingriffen mit extrakorporaler Zirkulation weisen eine hohe Inzidenz neurologischer bzw. neuropsychologischer Symptome auf. Die Ursachen für derartige Störungen sind als multifaktoriell einzuordnen und lassen sich Risikofaktoren zuweisen, die durch den Einsatz einer extrakorporalen Zirkulation und durch patientenspezifische Charakteristika bedingt sind. In dieser Übersicht werden nicht-invasive (Transkranielle Doppler-Sonographie, Elektroenzephalographie, Infrarotspektroskopie) und invasive (Messung der jugularvenösen Sauerstoffsättigung, Kety-Schmidt-Technik, Xenon-Clearancetechnik, Transzerebrale Doppelindikatorverdünnungstechnik) Überwachungs- und Untersuchungsverfahren auf ihre Einsetzbarkeit und Aussagekraft zur Detektion von Störungen der zerebralen Hämodynamik und des Hirnmetabolismus bei kardiochirurgischen Eingriffen betrachtet.Summary In patients receiving surgical interventions with the use of cardiopulmonary bypass, the incidence of postoperative neurological and neuropsychological dysfunction still remains high. The reasons for these disorders may be seen as multifactorial and can be divided into patient and cardiopulmonary bypass related risk factors. In this review non-invasive (transcranial Doppler sonography, electroencephalography, infrared spectroscopy) and invasive (measurement of jugular venous oxygen saturation, Kety-Schmidt technique, 133Xenon-clearance technique, transcerebral double indicator dilution technique) monitoring methods were evaluated for clinical applicability and evidence to detect cerebral hemodynamic and metabolic impairment during and after the cardiopulmonary bypass period.