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Background: During acellular replacement of an acute blood loss, hyperoxic ventilation (HV) increases the amount of O2 physically dissolved in the plasma and thereby improves O2 supply to the tissues. While this effect could be demonstrated for HV with inspiratory O2 fraction (FiO2) 0.6, it was unclear whether HV with pure oxygen (FiO2 1.0) would have an additional effect on the physiological limit of acute normovolemic anemia. Methods: Seven anesthetized domestic pigs were ventilated with FiO2 1.0 and subjected to an isovolemic hemodilution protocol. Blood was drawn and replaced by a 6% hydroxyethyl starch (HES) solution (130/0.4) until a sudden decrease of total body O2 consumption (VO2) indicated the onset of O2 supply dependency (primary endpoint). The corresponding hemoglobin (Hb) concentration was defined as 'critical Hb' (Hbcrit). Secondary endpoints were parameters of myocardial function, central hemodynamics, O2 transport and tissue oxygenation. Results: HV with FiO2 1.0 enabled a large blood-for-HES exchange (156 ± 28% of the circulating blood volume) until Hbcrit was met at 1.3 ± 0.3 g/dl. After termination of the hemodilution protocol, the contribution of O2 physically dissolved in the plasma to O2 delivery and VO2 had significantly increased from 11.7 ± 2 to 44.2 ± 9.7% and from 29.1 ± 4.2 to 66.2 ± 11.7%, respectively. However, at Hbcrit, cardiovascular performance was found to have severely deteriorated. Conclusion: HV with FiO2 1.0 maintains O2 supply to tissues during extensive blood-for-HES exchange. In acute situations, where profound anemia must be tolerated (e.g. bridging an acute blood loss until red blood cells become available for transfusion), O2 physically dissolved in the plasma becomes an essential source of oxygen. However, compromised cardiovascular performance might require additional treatment. © 2013 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: The patient's individual anemia tolerance is pivotal when blood transfusions become necessary, but are not feasible for some reason. To date, the effects of neuromuscular blockade (NMB) on anemia tolerance have not been investigated. Methods: 14 anesthetized and mechanically ventilated pigs were randomly assigned to the Roc group (3.78 mg/kg rocuronium bromide followed by continuous infusion of 1 mg/kg/min, n = 7) or to the Sal group (administration of the corresponding volume of normal saline, n = 7). Subsequently, acute normovolemic anemia was induced by simultaneous exchange of whole blood for a 6% hydroxyethyl starch solution (130/0.4) until a sudden decrease of total body O2 consumption (VO2) indicated a critical limitation of O2 transport capacity. The Hb concentration quantified at this time point (Hbcrit) was the primary endpoint of the protocol. Secondary endpoints were parameters of hemodynamics, O2 transport and tissue oxygenation. Results: Hbcrit was significantly lower in the Roc group (2.4 ± 0.5 vs. 3.2 ± 0.7 g/dl) reflecting increased anemia tolerance. NMB with rocuronium bromide reduced skeletal muscular VO2 and total body O2 extraction rate. As the cardiac index increased simultaneously, total body VO2 only decreased marginally in the Roc group (change of VO2 relative to baseline -1.7 ± 0.8 vs. 3.2 ± 1.9% in the Sal group, p < 0.05). Conclusion: Deep NMB with rocuronium bromide increases the tolerance of acute normovolemic anemia. The underlying mechanism most likely involves a reduction of skeletal muscular VO2. During acellular treatment of an acute blood loss, NMB might play an adjuvant role in situations where profound stages of normovolemic anemia have to be tolerated (e.g. bridging an unexpected blood loss until blood products become available for transfusion). Copyright © 2011 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Fluorescent microspheres (FM) have become an attractive alternative to radioactive microspheres (RM) for the measurement of regional blood flow (RBF). The aim of the present study was to investigate the comparability of both methods by measuring RBF with FM and RM. Eight anaesthetised pigs received simultaneous, left atrial injections of FM and RM with a diameter of 15 μm at six different time points. Blood reference samples were collected from the descending aorta. RBF was determined in tissue samples of the myocardium, spleen and kidneys of all 8 animals. After radioactivity of the tissue samples was determined, the samples were processed automatically for measuring fluorescence using a recently developed filter device (SPU). RBF was calculated with both the isotope and spectrometric data of both methods for each sample resulting in a total of 10,512 blood flow values. The comparison of the RBF values yielded high linear correlation (mean r[sup 2] = 0.95 ± 0.03 to 0.97 ± 0.02) and excellent agreement (bias 5.4–6.7%, precision 9.9– 16.5%) of both methods. Our results indicate the validity of MS and of the automated tissue processing technique by means of the SPU.Copyright © 2002 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Intraoperative surgical blood loss is initially replaced by infusion of red cell-free, cristalloidal or colloidal solutions. When normovolemia is maintained the ensuing dilutional anemia is compensated by an increase of cardiac output and of arterial oxygen extraction. In the ideal case, a surgical blood loss can entirely be ‘bridged’ without transfusion by intraoperative normovolemic hemodilution. However major blood loss results in extreme hemodilution and the transfusion of red blood cells may finally become necessary to increase arterial oxygen content and to preserve tissue oxygenation. When transfusion has to be started before surgical control of bleeding has been achieved, parts of the red blood cells transfused will get lost, thereby increasing intraoperative transfusion needs. Beside red blood cell transfusion, arterial oxygen content can be rapidly increased by ventilating the patient with 100% oxygen (hyperoxic ventilation), thus enhancing the amount of physically dissolved oxygen in plasma (hyperoxia). In experimental and clinical studies hyperoxic ventilation has emerged as a simple, safe and effective intervention to enlarge the margin of safety for hemodynamic compensation and tissue oxygenation in hemodiluted subjects experiencing major bleeding. The hyperoxia-associated microcirculatory dysregulation and impaired tissue oxygenation known to take place in the presence of a physiologic hemoglobin concentration are not encountered in hemodiluted subjects. Hyperoxic hemodilution i.e. the combination of intraoperative extreme hemodilution and hyperoxic ventilation may therefore be considered a cost-effective, safe and efficient supplement to reduce allogeneic transfusion during surgical interventions associated with high blood losses. The vast majority of the experimental and clinical investigations this new concept is based on was initiated and performed under the guidance of Prof. Konrad Messmer.Copyright © 2002 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Today, the technique to directly administer vasodilators via the airway to treat pulmonary hypertension and to improve pulmonary gas exchange is widely accepted among clinicians. The flood of scientific work focussing on this new therapeutic concept had been initiated by a fundamental new observation by Pepke-Zaba [1]and Frostell in 1991 [2]: Both scientists reported, that inhalation of exogenous nitric oxide (NO) gas selectively dilates pulmonary vessels without a concomittant systemic vasodilation. No more than another decade ago NO was identified as an important endogenous vasodilator [3]while having merely been regarded an environmental pollutant before that time. Although inhaled NO proved to be efficacious, alternatives were sought-after due to NO’s potential side-effects. In search for the ideal inhaled vasodilator another group of endogenous mediators – the prostanoids – came into the focus of interest. The evidence for safety and efficacy of inhaled prostanoids is – among a lot of other valuable work – based on a series of experimental and clinical investigations that have been performed or designed at the Institute for Surgical Research under the guidance and mentorship of Prof. Dr. med. Dr. h.c. mult. K. Messmer [4-19]. In the following, the current and newly emerging clinical applications of inhaled prostanoids and the experimental data which they are based on, will be reviewed.Copyright © 2002 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

In severe hemorrhagic shock, left ventricular (LV) diastolic dysfunction is an early sign of cardiac failure due to compromised myocardial oxygenation. Immediate fluid replacement or, in particular, administration of a hemoglobin-based oxygen carrier (diaspirin cross-linked hemoglobin; DCLHb) improves myocardial oxygenation; therefore, positive effects on LV diastolic function could be expected. The effects of fluid resuscitation from severe hemorrhagic shock with DCLHb were investigated in 20 anesthetized domestic pigs. After generation of a critical left anterior descending coronary artery stenosis (narrowing of the artery until disappearance of reactive hyperemia after a 10-second complete vessel occlusion), hemorrhagic shock (mean arterial blood pressure 45 mm Hg) was induced within 15 min by controlled blood withdrawal and maintained for 60 min. Fluid resuscitation consisted of replacement of the plasma volume withdrawn during hemorrhage by infusion of either 10% DCLHb (DCLHb group, n = 10) or 8% human serum albumin (HSA) oncotically matched to DCLHb (HSA group, n = 10). After completion of resuscitation, an observation period of 60 min elapsed. Measurements of central hemodynamics, myocardial oxygenation, and LV diastolic function were performed at baseline, after induction of critical coronary artery stenosis, after 60 min of hemorrhagic shock, immediately after resuscitation, and 60 min later. While 5 out of 10 animals treated with HSA died within the first 20 min after fluid resuscitation from acute LV pump failure, all DCLHb-treated animals survived until the end of the protocol (p < 0.05). Despite superior myocardial oxygenation due to augmentation of the arterial O[sub 2] content as well as of coronary perfusion pressure, no beneficial effects on LV diastolic function were observed after infusion of DCLHb. Peak velocity of LV pressure decrease (dp/dt[sub min] ) did not reveal significant differences between the two groups. Immediately after completion of fluid resuscitation with DCLHb, the time constant of LV diastolic relaxation (τ) was prolonged when compared with HSA-treated animals (p < 0.05), indicating retardation of early LV diastolic relaxation. Our data suggest that DCLHb fails to improve LV diastolic function after fluid resuscitation from severe hemorrhagic shock. However, positive effects on myocardial perfusion and oxygenation result in a significant reduction of the mortality of severe hemorrhagic shock.Copyright © 2001 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]