A mechanistic analysis of the inoculum requirement for the cultivation of mammalian cells on microcarriers. 1985.
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Bioreactors↗
Biomedical subjects
J Meier
Publications and source records attributed to J Meier.
Blood pressure control in a diabetic population assessed by computer review.
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Aged↗
[Tolerance to perioperative anemia. Mechanisms, influencing factors and limits].
The expected cost explosion in transfusion medicine (increasing imbalance between donors and potential recipients, treatment of transfusion-associated complications) increases the socio-economic significance of specific institutional transfusion programs. In this context the estimated use of the patient's physiologic tolerance to anemia enables 1) the tolerance of larger blood losses (loss of "diluted blood"), 2) the onset of transfusion to the time after surgical control of bleeding to be delayed and 3) the perioperative collection of autologous red blood cells. The present review article summarizes the mechanisms, influencing factors and limits of this natural tolerance to anemia and deduces the indication for perioperative red blood cell transfusion. Under strictly controlled conditions (anesthesia, normovolemia, complete muscular relaxation, hyperoxemia, mild hypothermia) extremely low hemoglobin concentrations [Hb <3 g/dl (<1.86 mmol/l)] are tolerated without transfusion by individuals with no cardiopulmonary disease. In the clinical routine these situations are limited to borderline situations e.g. unexpected massive blood losses in Jehovah's Witnesses or unexpected shortcomings in blood supply. The current recommendations coincide to the effect that perioperative red blood cell transfusion 1) is unnecessary up to a Hb concentration of 10 g/dl (6.21 mmol/l) even in older patients with cardiopulmonary comorbidity and 2) is only recommended in cases of Hb <6 g/dl (<3.72 mmol/l) in otherwise healthy subjects including pregnant women and children. Critically ill patients with multiple trauma and sepsis do not seem to benefit from transfusions up to Hb concentrations >9 g/dl (>5.59 mmol/l). In cases of massive hemorrhaging and diffuse bleeding disorders the maintenance of a Hb concentration of 10 g/dl (6.21 mmol/l) seems to contribute to stabilization of coagulation.
Anemia↗
Hyperoxic ventilation increases the tolerance of acute normovolemic anemia in anesthetized pigs.
OBJECTIVE: To investigate the impact of prophylactic hyperoxic ventilation with Fio2 0.6 on the physiologic limit of acute normovolemic anemia. DESIGN: Prospective, controlled, randomized experimental study. SETTING: Experimental animal laboratory of a university hospital. SUBJECTS: Fourteen anesthetized domestic pigs. INTERVENTIONS: Animals were randomly ventilated with either Fio2 0.21 (group 0.21, n = 7) or Fio2 0.6 (group 0.6, n = 7), and acute anemia was induced by isovolemic blood-for-hydroxy-ethylstarch (HES) exchange using a 6% HES solution (130/0.4). MEASUREMENTS AND MAIN RESULTS: The blood-for-HES-exchange was continued until a sudden decrease of total body oxygen consumption indicated the onset of oxygen supply dependency (primary end point); the corresponding hemoglobin (Hb) concentration was defined as "critical" (Hb(crit)). Secondary end points were changes in myocardial function, central hemodynamics, oxygen transport, and tissue oxygenation. Compared with room air ventilation (Fio2 0.21), hyperoxic ventilation with Fio2 0.6 enabled a larger blood-for-HES-exchange (139%, 124/156) of circulating blood volume vs. 87% (68/94, p < .05), until Hb(crit) was reached (1.5 g/dL [1.4/2.1] vs. 2.4 g/dL [2.0/2.8], p < .05). At Hb 2.4 g/dL (i.e., Hb(crit) in group 0.21), animals of group 0.6 still presented with superior oxygen transport, tissue oxygenation, and hemodynamic stability. However, hemodynamic and oxygen transport variables were found deteriorated more severely at Hb 1.5 g/dL (i.e., Hb(crit) of group 0.6) compared with group 0.21 at Hb 2.4 g/dL. CONCLUSION: During cell-free volume replacement, hyperoxic ventilation with Fio2 0.6 generates a readily usable plasmatic oxygen reserve and thereby increases the tolerance toward acute normovolemic anemia.
Anemia↗
Incoherent blocker soliton interactions in Kerr waveguide arrays.
We have observed the incoherent interaction between a highly confined (blocker) soliton and wide, moving signal beams of a different wavelength in a one-dimensional discrete Kerr medium. Digital switching of the blocker solitons to successive adjacent channels was measured with increasing signal power via both one and two cascaded interactions in an AlGaAs waveguide array, operations equivalent to a reconfigurable three-output router.
Journal Article↗
Hyperoxic ventilation enables hemodilution beyond the critical myocardial hemoglobin concentration.
BACKGROUND: When initiated in anemic hypoxia, hyperoxic ventilation (ventilation with pure O2, FiO2 1.0, HV) reverses hypoxia-induced ECG-changes and enables survival for several hours. The quantification of the HV-induced gain in anemia tolerance and particularly the Hb-equivalent of HV in this situation are unknown. METHODS: Nine anaesthetized pigs were hemodiluted under normoxia (FiO2 0.21) by exchange of whole blood for hydroxyethyl starch (HES) until predefined, ischemia associated ECG-changes occurred (timepoint Hb(crit)). From that time on all animals were ventilated with 100% O2 (FiO2 1.0). In the case of disappearance of the ECG changes with onset of HV, the animals were further hemodiluted until ECG changes reoccurred. RESULTS: HV initiated in anemic hypoxia (Hb 2.3 +/- 0.2 g/dl) improved ECG-readings of all animals, and allowed for a further exchange of 14 +/- 11 ml/kg blood until ECG-changes reoccurred at Hb 1.2 +/- 0.4 g/dl. CONCLUSION: HV initiated in anemic hypoxia creates a margin of safety for myocardial tissue oxygenation and thus further increases anemia tolerance. The Hb equivalent of HV in this situation amounts to approximately 1g/dl.
Animals↗
Beam interactions with a blocker soliton in one-dimensional arrays.
We investigate experimentally and numerically the interaction of a highly localized, single-channel discrete soliton (blocker) with a wide, tilted beam in a one-dimensional AlGaAs array. In agreement with theory the blocker is observed to discretely shift its position by multiple channels, depending on the intensity and relative phase of the tilted beam.
Journal Article↗
[Artificial oxygen carriers as an alternative to red blood cell transfusion].
The expected cost-explosion in transfusion medicine (increasing imbalance between donors and recipients, treatment of transfusion-associated complications) increases the socio-economic significance of the development of safe and effective synthetic oxygen carriers as an alternative to the transfusion of allogeneic red blood cells. Currently two types of artificial oxygen carriers have been tested for safety and efficacy in cases of severe anemia otherwise requiring transfusion. Solutions based on human or bovine hemoglobin (HBOC) possess vasoconstrictor properties in addition to their oxygen transport capacity. The impact of vasoconstriction on tissue perfusion and organ function is however not yet fully understood. Nevertheless, in 2001 the bovine HBOC Hemopure was approved in South Africa for treatment of acutely anemic surgical patients. The purely synthetic perfluorocarbon (PFC) emulsions increase the physically dissolved portion of arterial oxygen content. Due to their particulate nature (emulsion droplets) PFCs may only be infused in low doses to avoid overload and malfunction of phagocytic cells of the reticulo-endothelial system. As part of a multimodal blood conservation program (including normovolemic hemodilution and hyperoxia) the low-dose administration of Oxygent effectively increases intraoperative anemia tolerance. Although reduction of perioperative allogeneic blood transfusion has already been demonstrated for HBOC and PFC, the global clinical establishment of artificial oxygen carriers is not to be expected in the near future.
Animals↗
[The surgeon's role as expert witness in malpractice lawsuits. Purpose and requirements of legal medical opinions].
Even experienced medical advisors need clear guidelines on the extent and form of expert opinions presented to courts of law. The importance of thorough document study, correctly organizing findings, and carefully weighing the various factors influencing an opinion cannot be stressed enough. Presented here is a sample opinion for German civil court trials at the state level. It illustrates how best to combine research and clinical results, personal professional experience, and citations from the literature to structure legally valid evidence in the form of an expert opinion. The importance of cogent response to examiners' and cross-examiners' questions is demonstrated, as are differences between civil and criminal proceedings. An appendix cites the appropriate passages from the German legal code concerning remuneration for expert opinions.
Certification↗
Experimental observation of discrete modulational instability.
We report the first experimental observation of modulation instability in a discrete optical nonlinear array.
Journal Article↗
[Indications for blood transfusion during orthopedic surgery].
Ageing of the population increases the number of large orthopedic surgical interventions in elder people. High perioperative blood loss together with a reduced tolerance to anemia increase the transfusion probability in this patient subgroup. The expected cost explosion in the transfusion system (cost intensive quality management, imbalance between the number of donors and recipients) as well as the remaining transfusion related risk of hemolysis, infection and immunosuppression reflect the high socio-economic significance of the development of institutional transfusion programs. The present article summarizes: (1) the (patho-) physiology of anemia compensation, (2) the decision making for transfusion in healthy patients and patients with cardiovascular disease, and (3) the currently applied pre- and intraoperative techniques to reduce allogeneic transfusion in orthopedic patients.
Aged↗
Hyperoxic ventilation at the critical hematocrit: effects on myocardial perfusion and function.
BACKGROUND: Hemodilution reduces hematocrit (Hct) and blood oxygen content. Tissue oxygenation is mainly preserved by increased cardiac output. As myocardial O2-demands increase, coronary vasodilatation becomes necessary to increase myocardial blood flow. Myocardial ischemia occurs at a critical Hct-value (Hctcrit), with accompanying exhaustion of coronary reserve. Hyperoxic ventilation is known to both reverse peripheral tissue hypoxia at Hctcrit and also to induce coronary vasoconstriction. This study aimed to determine whether hyperoxic ventilation at Hctcrit further exacerbates myocardial ischemia and dysfunction. METHODS: Nine anesthetized pigs ventilated on room air were hemodiluted by 1:1 exchange of blood with pentastarch (6%HES) to Hctcrit, defined as onset of myocardial ischemia (ECG changes). At Hctcrit, hyperoxic ventilation was started. Measurements were performed at baseline, at Hctcrit, and after 15 min of hyperoxic ventilation. We determined myocardial blood flow (microsphere method), arterial O2-content, subendocardial O2-delivery and myocardial function (left ventricular pressure increase). RESULTS: At Hctcrit 7 (6;8)%, O2-content was reduced [3.7 (3.1;3.9) ml dl(-1)]. Despite a compensatory increase of myocardial blood flow [531 (449;573), ml min(-1)100 g(-1)], all pigs displayed myocardial ischemia and compromised myocardial function (P < 0.05). Hyperoxic ventilation produced increased coronary vascular resistance secondary to vasoconstriction, and reduced myocardial blood flow [426 (404;464), ml min(-1)100 g(-1); P < 0.05]. Myocardial oxygenation was found to be maintained by increased O2-content [4.4 (4.2;4.8), ml dl(-1); P < 0.05], the contribution of dissolved O2 to subendocardial O2-delivery increased (32 vs. 8%; P < 0.05), which preserved myocardial function. CONCLUSION: Hyperoxic ventilation at Hctcrit is followed by coronary vasoconstriction and reduction of coronary blood flow. However, myocardial oxygenation and function is maintained, as increased O2-content (in particular dissolved O2) preserves myocardial oxygenation.
Animals↗
Fluid resuscitation from severe hemorrhagic shock using diaspirin cross-linked hemoglobin fails to improve pancreatic and renal perfusion.
BACKGROUND: Fluid resuscitation from hemorrhagic shock is intended to abolish microcirculatory disorders and to restore adequate tissue oxygenation. Diaspirin cross-linked hemoglobin (DCLHb) is a hemoglobin-based oxygen carrier (HBOC) with vasoconstrictive properties. Therefore, fluid resuscitation from severe hemorrhagic shock using DCLHb was expected to improve perfusion pressure and tissue perfusion of kidneys and pancreas. METHODS: In 20 anesthetized domestic pigs with an experimentally induced coronary stenosis, shock (mean arterial pressure 45 mmHg) was induced by controlled withdrawal of blood and maintained for 60 min. Fluid resuscitation (replacement of the plasma volume withdrawn during hemorrhage) was performed with either 10% DCLHb (DCLHb group, n = 10) or 8% human serum albumin (HSA) oncotically matched to DCLHb (HSA group, n = 10). Completion of resuscitation was followed by a 60-min observation period. Regional blood flow to the kidneys and the pancreas was measured by use of the radioactive microspheres method at baseline, after shock and 60 min after fluid resuscitation. RESULTS: All animals (10/10) resuscitated with DCLHb survived the 60-min observation period, while 5/10 control animals died within 20 min due to persisting subendocardial ischemia. In contrast to HSA survivors, pancreas and kidneys of DCLHb-treated animals revealed lower total and regional organ perfusion and regional oxygen delivery. Renal and pancreatic blood flow heterogeneity was higher in the DCLHb group. CONCLUSION: DCLHb-induced vasoconstriction afforded superior myocardial perfusion, but impaired regional perfusion of the kidneys and the pancreas.
Algorithms↗
New mathematical model for the correct prediction of the exchangeable blood volume during acute normovolemic hemodilution.
BACKGROUND: The blood volume that has to be exchanged for crystalloids and/or colloids during acute normovolemic hemodilution (ANH) in order to reach a preset target hemoglobin concentration (hb) is usually predicted by the Bourke and Smith formula developed in 1974. This formula systematically overestimates the 'true' exchangeable blood volume (EBV), a fact that may potentially endanger patients because the target hb will be missed and the normovolemic anemia might turn out to be more severe than a priori intended. Our objective was to develop a more accurate mathematical model of hemodilution kinetics and to validate this new model in animals and in patients undergoing ANH. METHODS: Twenty-two anesthetized beagle dogs and 18 patients under balanced anesthesia underwent isovolemic hemodilution with hydroxyethyl starch (HAES 6%, 200 000) to a target hb of 7 g dl-1 or 9 g dl-1, respectively. Exchangeable blood volume predicted by use of the different mathematical models was compared with the blood volume actually exchanged to meet the preset target hb. RESULTS: Calculation of EBV by the Bourke and Smith formula (EBVB + S) systematically overestimated the volume actually exchanged (overestimation: dogs 15%, patients 20%), whereas our new iterative model predicted EBV (EBViterative) more reliably (overestimation: dogs 1%, patients 8%). In both cases EBVB + S differed significantly from the EBViterative. CONCLUSION: Exchangeable blood volume is predicted more accurately by the new iterative model than by the Bourke and Smith formula. The iterative model leads to an improvement in patient safety and provides a physiologically adequate basis for future studies investigating the efficacy of ANH in reducing allogenic blood transfusions.
Algorithms↗
[Water Birth: experience at a university clinic and a district hospital in Austria].
PURPOSE AND METHODS: In a retrospective case-control study, 265 water deliveries (with cephalic presentation) carried out at an Austrian university clinic and a district hospital were compared with a group of spontaneous births (without any surgical intervention) matched for age, gestational age and parity regarding the most important fetal and maternal obstetric parameters. RESULTS: 4.3% of all births at the university clinic and 13% of those at the district hospital took place in the water. Austrian women and women with a higher educational level were more numerous in this group. The duration of the different stages of birth was not essentially changed by the delivery in water. The cord blood pH of the water babies (median 7.29 and 7.35, respectively) was better than that of the control group (median 7.26), which may however be due to a positive selection of the women giving birth in the water. The number of episiotomies was markedly lower for water births (14 and 4%) than for land births (48%). In contrast, water births showed distinctly more first- and second-degree perineal tears (36 and 41%) and labial tears (23 and 21%) than the control group (perineal 23%; labial 7%). Women assigned to water birth needed fewer analgesics (8 and 9%) than the controls (64%). In puerperium, the haemoglobin values after water birth and after land birth did not differ. The infectious morbidity of the mother and child was not higher after water birth. CONCLUSIONS: Water birth is to be considered a safe method for a healthy mother and a healthy, full-term fetus with cephalic presentation (if the appropriate criteria are used at hospital wards with a specific infrastructure).
Adult↗
Intestinal ischemia after bushmaster (Lachesis muta) snakebite--a case report.
After a snakebite by the Costa Rican bushmaster Lachesis stenophrys, a 64-year-old patient developed cardiovascular shock and coagulopathy. After intensive care and antivenom treatment, he was discharged after 4 days but had to be hospitalised again 3 days later because of abdominal pain and bowel obstruction. An emergency laparotomy revealed a necrotic ileum and caecum, and an obstruction of the superior mesenteric artery. Until now, this type of intestinal ischemic complication after a snakebite has not been reported in the literature. The effects of bushmaster venom are discussed.
Animals↗
Novel method for the investigation of single nanoparticle reactivity.
The reactivity of planar surfaces has been well investigated but there are many new unexplored aspects involved in the reactivity of nanoparticle surfaces. Most investigative methods only measure the average properties of the particles present on the surface. In order to investigate the local reactivity of nanoparticles, the STM tip electrode can be used as a local sensor. The feasibility of this approach is demonstrated by detecting some of the hydrogen (through the hydrogen oxidation reaction current at the tip) which is evolved at a single Pd particle on the Au(111) substrate at a constant distance from the tip. In principle, it is thereby possible to determine the reactivities of surfaces on a nanometre scale. To avoid interference from different reactive particles it is essential to use electrodes with a very low particle density. Hence, in this investigation electrodes with single Pd particles which were deposited from the STM tip onto the substrate are used. Results of potential-dependent measurements at single metal nanoparticles will be shown and the possibilities and limitations of the approach will also be discussed.
Journal Article↗
Efficiency of cold passover and heated humidification under continuous positive airway pressure.
Cold passover and heated humidifiers are employed for the prevention of side-effects associated with continuous positive airway pressure (CPAP) treatment. However, to date, it has not been possible to separately measure the humidity of inspired and expired air. The aim of this study was to compare the relative humidity of the inspired air and the water loss during respiration between cold passover and heated humidifiers under CPAP. Humidity and temperature were determined separately for the respiratory phases, without humidification, with cold passover and heated humidifiers in 10 healthy subjects. Humidity was measured with a capacitive hygrometer, temperature with a "Type K" thermosensor, and impedance of the total respiratory system with impulse oscillometry. The relative humidity (rH) of the inspired air (mean+/-SD) increased significantly from 24.0+/-9.1%, rH (34.8+/-1.0 degrees C, no humidifier) to 34.5+/-10.1%, rH (34.6+/-1.0 degrees C) under cold humidification, and to 53.9+/-13.2% rH (35.0+/-1.1 degrees C) under heated humidification. With heated humidification, water loss was reduced by 38% compared to cold humidification. The impedance increased from 5.7+/-1.8 cmH2O x L x s(-1) (no humidifier) to 6.7+/-1.8 cmH2O x L x s(-1) (heated humidifier). The authors conclude that the use of a heated humidifier during continuous positive airway pressure appreciably increases the relative humidity of the inspired air and reduces the water loss during respiration.
Adolescent↗