Heinz Kerger

Combined inhibition of VEGF and PDGF signaling enforces tumor vessel regression by interfering with pericyte-mediated endothelial cell survival mechanisms

Destruction of existing tumor blood vessels may be achieved by targeting vascular endothelial growth factor (VEGF) signaling, which mediates not only endothelial cell proliferation but also endothelial cell survival. In this study, however, intravital microscopy failed to demonstrate that targeting of VEGFR‐2 (by the tyrosine kinase inhibitor SU5416) induces significant regression of experimental tumor blood vessels. Immunohistochemistry, electron microscopy, expression analyses, and in situ hybridization provide evidence that this resistance of tumor blood vessels to VEGFR‐2 targeting is conferred by pericytes that stabilize blood vessels and provide endothelial cell survival signals via the Ang‐1/Tie2 pathway. In contrast, targeting VEGFR‐2 plus the plate‐let‐derived growth factor receptor (PDGFR)‐β system (PDGFR‐β signaling (by SU6668) rapidly forced 40% of tumor blood vessels into regression, rendering these tumors hypoxic as shown by phosphorescence quenching. TUNEL staining, electron microscopy, and apoptosis blocking experiments suggest that VEGFR‐2 plus PDGFR‐β targeting enforced tumor blood vessel regression by inducing endothelial cell apoptosis. We further show that this is achieved by an interference with pericyte‐endothelial cell interaction. This study provides novel insights into the mechanisms of how 1) pericytes may provide escape strategies to anti‐angiogenic therapies and 2) novel concepts that target not only endothelial cells but also pericyte‐associated pathways involved in vascular stabilization and maturation exert potent anti‐vascular effects.

Systemic and microcirculatory effects of autologous whole blood resuscitation in severe hemorrhagic shock

Systemic and microcirculatory effects of autologous whole blood resuscitation after 4-h hemorrhagic shock with a mean arterial pressure (MAP) level of 40 mmHg were investigated in 63 conscious Syrian golden hamsters. Microcirculation of skeletal skin muscle and subcutaneous connective tissue was visualized in a dorsal skinfold. Shed blood was retransfused within 30 min after 4 h. Animals were grouped into survivors in good (SG) and poor condition (SP) and nonsurvivors (NS) according to 24-h outcome after resuscitation and studied before shock, during shock (60, 120, and 240 min), and 30 min and 24 h after resuscitation. Microvascular and interstitial PO2 values were determined by phosphorescence decay. Shock caused a significant increase of arterial PO2 and decrease of PCO2, pH, and base excess. In the microcirculation, there was a significant decrease in blood flow (QB), functional capillary density (FCD; capillaries with red blood cell flow), and interstitial PO2 [1.8 +/- 0.8 mmHg (SG), 1.3 +/- 1.3 mmHg (SP), and 0.9 +/- 1.1 mmHg (NS) vs. 23.0 +/- 6.1 mmHg at control]. Blood resuscitation caused immediate MAP recompensation in all animals, whereas metabolic acidosis, hyperventilation, and a significant interstitial PO2 decrease (40-60% of control) persisted. In NS (44.4% of the animals), systemic and microcirculatory alterations were significantly more severe both in shock and after resuscitation than in survivors. Whereas in SG (31.8% of the animals) there was only a slight (15-30%) but still significant impairment of microscopic tissue perfusion (QB, FCD) and oxygenation at 24 h, SP (23.8% of the animals) showed severe metabolic acidosis and substantial decreases (>/=50%) of FCD and interstitial PO2. FCD, interstitial PO2, and metabolic state were the main determinants of shock outcome.Systemic and microcirculatory effects of autologous whole blood resuscitation after 4-h hemorrhagic shock with a mean arterial pressure (MAP) level of 40 mmHg were investigated in 63 conscious Syrian golden hamsters. Microcirculation of skeletal skin muscle and subcutaneous connective tissue was visualized in a dorsal skinfold. Shed blood was retransfused within 30 min after 4 h. Animals were grouped into survivors in good (SG) and poor condition (SP) and nonsurvivors (NS) according to 24-h outcome after resuscitation and studied before shock, during shock (60, 120, and 240 min), and 30 min and 24 h after resuscitation. Microvascular and interstitial[Formula: see text] values were determined by phosphorescence decay. Shock caused a significant increase of arterial[Formula: see text] and decrease of[Formula: see text], pH, and base excess. In the microcirculation, there was a significant decrease in blood flow (Q˙B), functional capillary density (FCD; capillaries with red blood cell flow), and interstitial [Formula: see text][1.8 ± 0.8 mmHg (SG), 1.3 ± 1.3 mmHg (SP), and 0.9 ± 1.1 mmHg (NS) vs. 23.0 ± 6.1 mmHg at control]. Blood resuscitation caused immediate MAP recompensation in all animals, whereas metabolic acidosis, hyperventilation, and a significant interstitial [Formula: see text] decrease (40-60% of control) persisted. In NS (44.4% of the animals), systemic and microcirculatory alterations were significantly more severe both in shock and after resuscitation than in survivors. Whereas in SG (31.8% of the animals) there was only a slight (15-30%) but still significant impairment of microscopic tissue perfusion (Q˙B, FCD) and oxygenation at 24 h, SP (23.8% of the animals) showed severe metabolic acidosis and substantial decreases (≥50%) of FCD and interstitial[Formula: see text]. FCD, interstitial[Formula: see text], and metabolic state were the main determinants of shock outcome.

pO2 measurements by phosphorescence quenching: characteristics and applications of an automated system

An automated system for pO(2) analysis based upon phosphorescence quenching was tested. The system was calibrated in vitro with capillary samples of saline and blood. Results were compared to a conventional measuring procedure wherein pO(2) was calculated off-line by computer fitting of phosphorescence decay signals. PO(2) measurements obtained by the automated system were correlated (r(2) = 0.98) with readings simultaneously generated by a blood gas analyzer, accuracy being highest in the low (0-20 mm Hg) and medium pO(2) ranges (21-70 mm Hg). Measurements in in vivo studies in the hamster skin-fold preparation were similar to previously reported results. The automated system fits the phosphorescence decay data to a single exponential and allows repeated pO(2) measurements in rapid sequence.

Subcutaneous microvascular responses to hemodilution with a red cell substitute consisting of polyethyleneglycol‐modified vesicles encapsulating hemoglobin

Phospholipid vesicles encapsulating purified hemoglobin [Hb vesicles (HbV); diameter 259 +/- 82 mm; oxygen affinity 31 mm Hg; [Hb] 5 and 10 g/dL] were developed to provide oxygen-carrying capacity to plasma expanders. Their function as a blood replacement was tested in the subcutaneous microvasculature of awake hamsters during severe hemodilution in which 80% of the red blood cell mass was substituted with suspensions of the vesicles in 5% human serum albumin (HSA) solution. Vesicles were tested with membranes that were unmodified (HbV/HSA) or conjugated with polyethyleneglycol (PEG) on the vesicular surface (PEG-HbV/HSA). The viscosity of 10 g/dL HbV/HSA was 8 cP at 358 s-1 owing to the intervesicular aggregation, while that of 10 g/dL PEG-HbV/HSA was 3.5 cP, since PEG chains inhibit aggregation. Both materials yielded normal mean arterial pressure, heart rate, and blood gas parameters at all levels of exchange, which could not be achieved with HSA alone. Subcutaneous microvascular studies showed that PEG-HbV/HSA significantly improved microhemodynamic conditions (flow rate, functional capillary density, vessel diameter, and oxygen tension) relative to unmodified HbV/HSA. Even though the enhancement of PEG modification did not achieve the functional characteristics of the blood-perfused microcirculation, PEG reduced vesicular aggregation and viscosity, improving microvascular perfusion relative to the unmodified type. These results highlight the significance of microvascular analysis in the design of red cell substitutes and the necessity of surface modification of HbV to prevent aggregation.

Depression of endothelial and smooth muscle cell oxygen consumption by endotoxin

An optical method based on the oxygen-dependent quenching of a phosphorescent probe (palladium-porphyrin) was used to investigate the effect of bacterial endotoxin [lipopolysaccharide (LPS)] on oxygen consumption (V˙o 2) by vascular cells. Endothelial (EC) and smooth muscle (SMC) cells from pig aorta were suspended in culture medium in the presence of palladium-porphyrin and transferred to glass capillary tubes that were sealed to create a hypoxic environment. Measured [Formula: see text]changed as a function of time in a highly predictable fashion when cell suspensions were exposed to agents or treatment known to affect cellular metabolism. Both EC and SMC showed a significant decrease inV˙o 2 as cell density increased, and SMC V˙o 2 was significantly higher than EC (1.94 ± 0.09 vs. 1.0 ± 0.15 nmol ⋅ min-1 ⋅ 106cells-1). Exposure to LPS (1 μg/ml) caused a decrease inV˙o 2 of 46% and 15% for EC and SMC, respectively. Pretreatment of cells with N-acetyl-l-cysteine, a substrate for glutathione synthesis with antioxidant properties, restored V˙o 2to normal values after exposure to LPS. These data suggest that endotoxin impairsV˙o 2 in cells derived from the vascular wall and indicate the importance of EC and SMC respiration in maintaining vascular homeostasis under conditions of sepsis.An optical method based on the oxygen-dependent quenching of a phosphorescent probe (palladium-porphyrin) was used to investigate the effect of bacterial endotoxin [lipopolysaccharide (LPS)] on oxygen consumption (VO2) by vascular cells. Endothelial (EC) and smooth muscle (SMC) cells from pig aorta were suspended in culture medium in the presence of palladium-porphyrin and transferred to glass capillary tubes that were sealed to create a hypoxic environment. Measured PO2 changed as a function of time in a highly predictable fashion when cell suspensions were exposed to agents or treatment known to affect cellular metabolism. Both EC and SMC showed a significant decrease in VO2 as cell density increased, and SMC VO2 was significantly higher than EC (1.94 +/- 0.09 vs. 1.0 +/- 0.15 nmol . min-1 . 10(6) cells-1). Exposure to LPS (1 microg/ml) caused a decrease in VO2 of 46% and 15% for EC and SMC, respectively. Pretreatment of cells with N-acetyl-L-cysteine, a substrate for glutathione synthesis with antioxidant properties, restored VO2 to normal values after exposure to LPS. These data suggest that endotoxin impairs VO2 in cells derived from the vascular wall and indicate the importance of EC and SMC respiration in maintaining vascular homeostasis under conditions of sepsis.

Microvascular Oxygen Delivery and Interstitial Oxygenation during Sodium Pentobarbital Anesthesia

Background Anesthesia may represent a considerable bias in experimental medicine, particularly in conditions of stress (such as hemorrhage). Sodium pentobarbital (PB), widely used for cardiovascular investigations, may impair oxygen delivery by hemodynamic and respiratory depression. The critical issue, however, is whether the microcirculation can still maintain tissue oxygenation during anesthesia. To answer this question, the authors studied the effect of PB anesthesia on subcutaneous microvascular oxygen delivery and interstitial oxygenation in Syrian golden hamsters. Methods Sodium pentobarbital anesthesia was induced by intravenous injection (30 mg/kg body weight) and maintained by a 15‐min infusion (2 mg [center dot] kg‐1 [center dot] min‐1), with animals breathing spontaneously (PB‐S) or ventilated with air (PB‐V). Systemic parameters evaluated were mean arterial pressure (MAP), heart rate, cardiac index (CI), arterial oxygen tension (PaO2), arterial carbon dioxide tension (PaCO2), base excess, and pH. Microvascular and interstitial oxygen tension (PO2), vessel diameter, red blood cell velocity (upsilonRBC), and blood flow (Qb) were measured in a dorsal skinfold preparation. Microcirculatory PO2 values were determined by phosphorescence decay. Results Sodium pentobarbital anesthesia significantly decreased CI, MAP, upsilonRBC, and Qb. During PB infusion, PaO2 values were 56 +/‐ 12.8 mmHg (PB‐S) and 115.9 +/‐ 14.6 mmHg (PB‐V) compared with 69.4 +/‐ 18.2 mmHg and 61.4 +/‐ 12.6 mmHg at baseline. However, microvascular PO2 was reduced by 25–55% in both groups, resulting in an interstitial PO2 decrease from 23.9 +/‐ 5.6 mmHg (control) to 13.1 +/‐ 9.1 mmHg (PB‐S) and 15.2 +/‐ 7 mmHg (PB‐V). Microcirculatory PO2 values were restored 30 min after PB infusion, even though hemodynamic depression and a light anesthetic plane were maintained. Conclusions Sodium pentobarbital anesthesia caused impairment of microvascular oxygen delivery and interstitial oxygenation, effects that were not prevented by mechanical ventilation. Although these effects were restricted to deep anesthetic planes, prolonged hemodynamic depression suggests that caution is warranted when using PB as an anesthetic in cardiovascular investigations.

Microcirculatory Consequences of Blood Substitution with αα-Hemoglobin

Blood substitution with non-cellular fluids lowers blood viscosity and increases blood flow velocity, altering the oxygen delivering capacity of the microcirculation and the balance between diffusive and convective oxygen transport. When blood volume is maintained with either crystalloid or colloidal volume replacement, microcirculatory oxygen transport is adequate for red blood cell losses of the order of 60%. Hemoglobin solutions utilizing αα-hemoglobin show microvascular effects similar to those found with non-oxygen carrying solutions, but are reduced and the additional intrinsic oxygen carrying capacity of the blood/solution mixture is not manifested. Mathematical analysis of microvascular data shows that these effects are due to increased oxygen delivery capacity of the circulation, which increases arteriolar oxygenation. Ensuing metabolic autoregulatory responses lead to an oxygenation paradox resulting in vasoconstriction, impairment of functional capillary density, and increased microcirculatory metabolism, causing decreased tissue oxygenation. It is proposed that higher viscosity, left-shifted hemoglobin oxygen saturation solutions will fully oxygenate tissue.

Microvascular Oxygen Distribution: Effects Due to Free Hemoglobin in Plasma

Results from our and other laboratories indicate that while cell-free O2 carriers based on modifications of the hemoglobin molecule do carry O2 in vivo when they are used to replace blood or restitute blood volume, the maintained or increased O2 content does not lead to a corresponding maintained or increased O2 delivery due to effects that appear to be of vasoactive origin. As a consequence, the full benefit of the O2 carrier is not realized, and in many instances results are similar to those obtained with blood volume restitution with non-oxygen carrying plasma expanders. This paradox, which must be understood and resolved if efficacy is to be established, is likely to arise from events that develop in the microcirculation when comparatively large amounts of hemoglobin are introduced in the circulation.

Prophylaxis of intra- and postoperative nausea and vomiting in patients during cesarean section in spinal anesthesia

Background This paper describes a randomized prospective study conducted in 308 patients undergoing caesarean section in spinal anaesthesia at a single hospital between 2010 and 2012 to find a suitable anti-emetic strategy for these patients. Material/Methods Spinal anesthesia was performed in left prone position, at L3/L4 with hyperbaric 0.5% Bupivacaine according to a cc/cm body height ratio. There were no opioids given peri-operatively. The patients received either no prophylaxis (Group I) or tropisetron and metoclopramide (Group II) or dimenhydrinate and dexamethasone (Group III), or tropisetron as a single medication (Group IV). The primary outcome was nausea and/or vomiting (NV) in the intraoperative, early (0–2 h) or late (2–24 h) postoperative period. Multivariate statistical analysis was conducted with a regression analysis and a backward elimination of factors without significant correlation. Results All prophylactic agents significantly reduced NV incidence intraoperatively. Relative risk reduction for NV by prophylaxis was most effective (59.5%) in Group II (tropisetron and metoclopramide). In Group III (dimenhydrinate and dexamethasone), NV risk was reduced by 29.9% and by 28.7% in Group IV (tropisetron mono-therapy). The incidence of NV in the early (0–2 h) and the late (2–24 h) postoperative period was low all over (7.8%), but the relative risk reduction of NV in the early postoperative period was 54.1% (Group IV), 45.1% (Group III), and 34.8% (Group II), respectively. In the late postoperative period, there was no significant difference between the 4 groups. Conclusions We recommend a prophylactic medication with tropisetron 2 mg and metoclopramide 20 mg for patients during caesarean section. These agents are safe, reasonably priced, and highly efficient in preventing nausea and vomiting.

Anaphylaktisches Herz-Kreislauf-Versagen nach intraoperativer Metamizolapplikation

ZusammenfassungDas nichtsteroidale Analgetikum Metamizol gehört chemisch zur Gruppe der Pyrazolderivate und nimmt aufgrund seiner ausgezeichneten Wirkung derzeit einen wesentlichen Platz im anästhesiologischen und perioperativen Umfeld ein. Es wird sehr häufig und erfolgreich zur postoperativen Akutschmerztherapie und – obwohl von der Zulassungsbehörde nicht dafür zugelassen – auch zur Schmerzprophylaxe eingesetzt.Die Substanz geriet jedoch in den letzten Jahren immer wieder in die Diskussion,nachdem neben allergischen Reaktionen über Agranulozytosen als Nebenwirkung berichtet wurde. Im vorliegenden Fall erhielt eine 48-jährige Patientin ohne Vorerkrankungen im Rahmen einer Tympanoplastik bei chronischer Otits media unter Allgemeinanästhesie eine Kurzinfusion von 2 g Metamizol/100 ml 0,9%iger NaCl-Lösung zur Schmerzprophylaxe.Fünf Minuten nach Beginn der Infusion und nachdem 1 g Metamizol appliziert waren,wurde die Patientin bei nicht mehr messbarem Blutdruck und ausgeprägter Zyanose reanimationspflichtig. Erst nach 20-minütiger Herzdruckmassage,Gabe von 3 mg Adrenalin sowie 2 mg Noradrenalin erlangte die Patientin wieder eine suffiziente Kreislauffunktion. Nachdem eine fulminante Lungenembolie durch Computertomographie und auch ein primäres kardiales Ereignis durch EKG und Enzymdiagnostik ausgeschlossen werden konnten,wurde die Patientin auf die Intensivstation verbracht und über 6 h nachbeatmet. Eine postoperativ durchgeführte allergologische Untersuchung ergab eine Typ-I-Sensibilisierung auf Metamizol, die als ursächlich für das intraoperative Herz-Kreislauf-Versagen in Folge einer massiven anaphylaktischen Reaktion anzusehen ist.AbstractCase report. In our case, a 48-year-old healthy woman undergoing elective tympanoplasty under general anesthesia received an infusion of 2 g dipyrone in 100 ml 0.9% sodium chloride solution for pain prophylaxis. After receiving 1 g dipyrone within 5 min, the patient exhibited a cardiocirculatory failure and cyanosis and had to be resuscitated.After 20 min of cardiopulmonary resuscitation and administration of 3mg epinephrine and 2 mg norepinephrine, a stable circulation was reestablished.After exclusion of a fulminant pulmonary embolism and a primary cardiac event by computer tomography, electrocardiogram and enzyme diagnostics, the patient was transferred to an intensive care unit where she was mechanically ventilated for a period of 6 h.After 2 days of intensive monitoring, she was transferred to a peripheral ward,where she exhibited a normal neurological status and stable cardiocirculatory condition. A postoperatively performed allergy testing revealed a type I sensitization to dipyrone, which was responsible for the intraoperative cardiocirculatory failure due to a massive anaphylactic reaction.However, in this case, the typical symptoms of allergic reactions such as erythema, edema or bronchospasm were missing, which did not allow for an immediate diagnosis. Conclusion. Regarding the frequent perioperative use of dipyrone and the severity of anaphylaxis observed in this case, it should be considered that this analgesic should be applied intravenously only if adequate safety measures such as emergency therapy option and patient monitoring are guaranteed as recommended by the German drug regulation authority since 1982.