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Biomedical subjects

K van Ackern

Publications and source records attributed to K van Ackern.

At least 55 records · Page 3Linked to original sources
PubMed1994

Effect of hypertonic NaCl-starch-solution on oedema of different pathogenesis.

Small volumes of hypertonic NaCl-solutions have been proven to restore haemodynamics in hypovolemic shock patients. Topic of this study was to investigate whether bolus application of 7.5% NaCl-6.5% starch-solution (HSS) apart from its relevance in shock might be an effective therapy in oedema. Considering differential therapeutic aspects, the volume effects of 7.2 ml HSS were tested in three types of oedema: hydrostatic oedema induced by venous congestion (n = 6), oedema caused by bradykinin injection (n = 6), and proteinase-induced oedema (n = 6). The arterial, venous pressure and weight changes indicating volume shifts between intra- and extravascular space were continuously monitored in 36 isolated perfused rabbit hindlimbs. Oedema formation was induced corresponding to a weight gain of 18-20 g. Subsequently 7.2 ml HSS were injected into the extracorporeal circulation system containing 200 ml cell free, isoosmotic perfusate. Six experiments of each oedema group without HSS-application served as controls. 75-100% of oedema formation could be remobilised via bolus application of HSS within 5 min in all types of oedema. A persisting weight reduction was detectable in the hydrostatic and bradykinin oedema, whereas in the elastase oedema the initial weight loss was followed by a regain of weight up to 180% of initial oedema formation at 120 min after HSS-application. The results show that, due to the osmotic gradient induced by bolus application of HSS, the hydrostatic and bradykinin oedema can be permanently remobilised, whereas the therapeutic effect during proteinase oedema is only short-lasting due to an irreversible damage of barrier function.

Animals↗
PubMed1994

Effects of a perfluorocarbon emulsion on regional cerebral blood flow and metabolism after fluid resuscitation from hemorrhage in conscious rats.

Regional cerebral blood flow and metabolism were investigated after addition of a small volume of perfluorocarbon (PFC) emulsion to the resuscitation fluid after hemorrhage. Severe volume-controlled hemorrhage (40 mL/kg body weight (bw) withdrawn over 30 min followed by hypovolemia of 30 min duration) was induced in conscious rats. While breathing 100% oxygen, the intravascular volume was repleted by the infusion of either 6% hydroxyethyl starch (mean mol wt 200,000/0.5; HES) or 6% hydroxyethyl starch plus perflubron (90% wt/vol emulsion of perfluoroctylbromide, 3 mL/kg bw; HES-PFOB). Two hours after fluid resuscitation either iodo[14C]antipyrine or 2[14C]deoxy-D-glucose were infused. Local cerebral blood flow (LCBF) or local cerebral glucose utilization (LCGU) were determined in 34 brain structures using quantitative autoradiography. Local cerebral metabolism was not disturbed in the HES and the HES-PFOB groups after fluid resuscitation, although slight reductions (mean -14%) were measured (HES-PFOB vs HES; P < 0.05). The HES-PFOB group showed LCBF values that were higher in the different brain structures than those of the HES group (mean +30%). A close correlation was found between LCGU and LCBF of the 34 brain structures in both groups (HES: r = 0.96, P < 0.01; HES-PFOB: r = 0.98, P < 0.01), whereas the LCBF-to-LCGU ratio was reset from 2.2 mL/mumol in the HES group to 3.4 mL/mumol in the HES-PFOB group (P < 0.05). The higher blood flows in the HES-PFOB group were sufficient to restore cerebral oxygen delivery to normal levels at a reduced arterial oxygen content.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Infusion of oxidized glutathione enhances postischemic segment-shortening in dog hearts.

Oxidized glutathione (GSSG) but not its reduced form (GSH) is taken up by intact myocardial cells, and is rapidly converted into GSH. Reduced glutathione is an important intracellular defense against oxygen-derived free radicals and has been found to enhance calcium sensitivity in skinned cardiac fibers. We have investigated the effects of intravenous GSSG on left ventricular systolic pressure, maximal rate of rise of pressure and regional segment-shortening in dogs subjected to occlusion of the left anterior descending artery for 30 minutes, followed by 45 minutes reperfusion. Starting 10 minutes before reperfusion, the dogs were randomly treated with either GSSG (100 mM, 5 ml/min, n = 5) or Ringer's solution (5 ml/min, n = 5) until 30 minutes of reperfusion. Myocardial blood flow was measured by radioactive microspheres. Infusion of GSSG increased total glutathione content in both ischemic (47 +/- 16 mumol/g protein) and nonischemic myocardium (71 +/- 17 mumol/g protein) as compared to controls (23 +/- 2 mumol/g protein, p < 0.05). In both groups paradoxical wall motion occurred in the ischemic region during occlusion. On reperfusion, regional dyskinesia persisted in controls; while, in glutathione-treated dogs, systolic segment-shortening reached half the baseline values (p < 0.05, treated vs controls, at 15, 30, 45 minutes reperfusion). During ischemia the area of pressure-length loops, obtained from simultaneous recordings of left ventricular pressure and regional segment length, decreased to 30 +/- 7% of baseline in controls and to 40 +/- 18% of baseline in GSSG-treated animals. After 45 minutes reperfusion it was restored to 78 +/- 22% baseline in treated hearts but was still 36 +/- 16 of baseline in controls (p < 0.05). We conclude that infusion of GSSG increases the intracellular stores of glutathione and improves the contractile state of postischemic myocardium.

Animals↗
PubMed1994

[Evaluating lung failure and the limits of artificial respiration].

The treatment and outcome of the respiratory failure decisively depend on its pathophysiological background. Besides simple blood gas analysis the investigation of the respiratory mechanics, interstitial lung water and the monitoring of the pulmonary pressure are necessary for an exact diagnosis. As a scoring method of lung failure the classification by Murray and Morell is most common. In addition to normal volume or pressure controlled artificial ventilation the treatment of lung failure sometimes requires new but accepted modes of ventilation as inversed ratio ventilation, permissive hypercapnea and high frequency ventilation. New methods as negative pressure ventilation, extracorporeal lung ventilation and liquid or partial liquid ventilation are not common yet and should be used only under special conditions. As a supplement of these modes of ventilation the application of prostacyclins, nitric oxide, surfactant and inhibitors of the arachidonic pathway is under clinical investigation. A limitation of the treatment of lung failure should be considered in irreversible multiple organ failure.

Critical Care↗
PubMed1993

Alterations of bacterial clearance induced by endotoxin and tumor necrosis factor.

The purpose of the study was to investigate the potential influence of endotoxin and tumor necrosis factor (TNF) on immune function in terms of systemic clearance and organ distribution of injected Escherichia coli in a rabbit model. To enable quantification of the clearance process, defined numbers of exogenous E. coli (1.3 x 10(8) CFU) were injected intravenously 60 min after bolus application of TNF (4 x 10(5) U, n = 6), after infusion of endotoxin (40 micrograms/kg of body weight) for 1 h (n = 6) or 4 h (n = 6), or after saline infusion (controls, n = 6). Parameters monitored were arterial pressure, oxygen uptake, and rates of bacterial elimination from the blood. At 180 min after E. coli injection, the animals were sacrificed, and tissue samples of liver, kidney, spleen, and lung were collected for bacterial counts. Endotoxin infusion produced a significant delay in blood clearance compared with saline and TNF pretreatment. The diminished systemic bacterial elimination was associated with significantly higher numbers of E. coli in the organs, thus reflecting reticuloendothelial system dysfunction. TNF had no major influence on the elimination kinetics of bacteria but affected the tissue distribution pattern with increased accumulation of E. coli in the lung (up to 100-fold of control values; P < 0.001).

Animals↗
PubMed1993

Local cerebral blood flow and glucose utilization after blood exchange with a hemoglobin-based O2 carrier in conscious rats.

The effects of a blood exchange on cerebral blood flow and glucose utilization were studied. A near to total blood exchange (hematocrit < 3%) was achieved in conscious rats by isovolemic hemodilution. Ultrapurified, polymerized, bovine hemoglobin (UPBHB) served as a blood substitute. Local cerebral blood flow (LCBF) and local cerebral glucose utilization (LCGU) were measured in 34 brain structures of conscious rats by means of the ido[14C]antipyrine and the 2-[14C]-deoxy-D-glucose methods. A group of rats without blood exchange served as control. After blood exchange LCBF increased from 36 to 126% in the different brain structures resulting in a nearly doubled mean cerebral blood flow (+82%). LCGU increased only moderately by 0-24%. Significant increases in LCGU were observed in 16 brain structures. Mean cerebral glucose utilization slightly increased (+14%). The relationship between LCGU and LCBF was found to be tight both in the control group (r = 0.95) as well as after blood replacement (r = 0.94), although it was reset to a higher overall LCBF-to-LCGU ratio. The profound increases in LCBF observed after blood exchange, which were not paralleled by comparable increases in LCGU, might be explained by a reduction of blood viscosity after blood exchange. Additional effects of blood exchange observed in the present study were an increase of mean arterial blood pressure and a decline of heart rate. The results indicate that replacement of blood with the hemoglobin-based oxygen carrier UPBHB appears to meet the cerebral circulatory and metabolic demands of the brain tissue.

Animals↗
PubMed1993

Modulation of pulmonary vascular resistance and edema formation by short-term infusion of a 10% fish oil emulsion.

BACKGROUND: The aim of this study was to investigate whether the pulmonary response to inflammatory stimulation, resulting in increased vascular resistance and permeability, could be attenuated by short-term infusion of triglycerides containing omega-3 fatty acids. With the concept of altering the composition of membrane phospholipids in such a manner that stimulation resulted in the release of less vasoconstrictive and permeability-enhancing metabolites of eicosapentaenoic acid instead of those of arachidonic acid (AA), the parenteral application of a lipid emulsion prepared from fish oil (Omegavenös) was tested in comparison with a soy oil preparation (Lipovenös). METHODS: Isolated lungs from anesthetized rabbits were ventilated and recirculatingly perfused (200 ml/min) with 200 ml cell-free buffer solution to which either 2 ml saline (controls, n = 6), 2 ml Lipovenös 10% (n = 6) or 2 ml Omegavenös 10% (n = 6) were added. To study the possible metabolic alterations in states of an enhanced AA turnover, lungs of each group were stimulated with smaller doses of A23187 (10(-8) M) during the 180-min lipid perfusion period, followed by a 10 times higher calcium ionophore A23187 (10(-7) M) challenge after washing out the lipids by exchange of perfusion fluid. Pulmonary artery pressure (PAP) and the lung weight gain indicating edema formation were monitored, and eicosanoids were analyzed in samples of the perfusate. RESULTS: Upon A23187 injection lung weight gain and PAP increase were significantly reduced (50%) in Omegavenös-perfused lungs in comparison with controls and Lipovenös treatment. The vascular reactions were accompanied by a shifting from LTC4 to LTC5 during and after Omegavenös perfusion. CONCLUSION: The data demonstrate that omega-3 fatty acids seem to be incorporated into the phospholipid pool of the pulmonary tissue, even after short-term infusion (3 h) resulting in an attenuated pressure reaction and edema formation due to an altered spectrum of metabolites in the case of inflammatory stimulation.

Acute-Phase Proteins↗
PubMed1993

Influence of a pentoxifylline-analogue on the granulocyte-mediated pulmonary mediator release and vascular reaction.

The influence of a novel pentoxifylline-analogue, HWA 138, on the polymorphonuclear neutrophil leukocyte (PMN)-mediated changes in pulmonary resistance and mediator release was investigated in the isolated perfused and ventilated rabbit lung model. Isolated, washed human granulocytes were injected into the pulmonary artery and stimulated by either 10(-6) mol/L N-formyl-L-leucin-methionyl-L-phenylalanine (FMP) or 3 x 10(-8) mol/L phorbol 12-myristate 13-acetate (PMA) in the presence or absence (controls) of HWA 138 (10(-4) mol/L). Shortly after granulocyte activation, there was a massive generation and release of thromboxane (> 110 pg/ml) and histamine (150-400 nmol/L), with an acute increase of pulmonary artery pressure (> 8 mmHg) in the control groups. Application of HWA 138 almost completely suppressed mediator formation and release as well as pulmonary vascular reaction in the FMP stimulated group. In contrast to this, HWA 138 was unable to influence either mediator release, the pulmonary pressure reaction or interstitial edema formation following PMA stimulation. In the present model, HWA 138 is supposed to be effective via granulocytes by decreasing mediator release, obviously due to burst reaction.

6-Ketoprostaglandin F1 alpha↗
PubMed1993

[Modified hemoglobin as a blood substitute in a rat model].

The use of modified haemoglobin solutions as blood substitutes has been investigated extensively during the past decades. Ultrapurified, polymerised bovine haemoglobin (upbHb) is a promising new substance in this respect. It was the aim of the present investigation to study the cardiovascular and respiratory effects of massive blood replacement with upbHb in a new model of conscious rats with continuous haemodynamic monitoring. METHODS. The right femoral artery and vein of 13 male Sprague-Dawley rats were catheterised during halothane-N2O-O2 anaesthesia. A thermistor catheter was placed in the descending aorta via the left femoral artery for measuring cardiac output by the thermodilution method. After recovery from anaesthesia blood replacement was achieved by arterial blood withdrawal and simultaneous venous infusion of upbHb in equal amounts. The haematocrit was lowered to < 3% and the animals were then left undisturbed in a rat restrainer while breathing room air. RESULTS. The animals showed no signs of disturbed behaviour patterns, distress, or adverse reactions. There were no significant changes in cardiac index and oxygen delivery during the investigation period of 4 h. A marked increase in mean arterial pressure (MABP) and systemic vascular resistance (SVR) of 30% was observed while stroke volume remained unchanged. Blood gases, acid-base status, and plasma glucose showed no major changes. Plasma oncotic pressure increased during the investigation period. CONCLUSIONS. The results indicate that there is adequate oxygenation and sufficient systemic oxygen delivery in conscious and drug-free rats after isovolaemic haemodilution with upbHb to a final haematocrit of < 3%. In contrast to previous haemodilution studies, which have tested non-oxygen-carrying solutions, no changes in cardiac index were observed. The cause of the increase in MAP and SVR remains to be established.

Animals↗
PubMed1993

Increased phospholipase A activities in sera of intensive-care patients show sn-2 specificity but no acyl-chain selectivity.

Phospholipase A (PLA) activities were measured by high-performance liquid chromatography in two enzyme preparations purified from human duodenal juice and a serum pool as well as in 52 sera from 31 intensive-care patients with various diseases. On the basis of a position-specific fatty acid analysis of the natural substrate ("soybean lecithin") from a commercial PLA kit, serum activities of PLA1 could be clearly distinguished from those of PLA2, which is not possible in the usual measurements made with single-label radioactive substrates. Independent of the type of disease, all sera with highly increased PLA activities (40-200 U/L) showed nearly pure PLA2 characteristics without any preference among oleic, linoleic, and linolenic acid in the sn-2 position of the glycerophospholipid substrate. Nevertheless, very low PLA1 activities (< or = 5 U/L, most likely due to heparin perfusion therapy) could also be detected by palmitic and stearic acid release from the sn-1 position, leading to small changes in fatty acid release patterns of sera with low PLA activities. Measurements with sera from heparin-treated volunteers demonstrated that heparin therapy may initially contribute as much as 22 U/L to increased PLA1 activities but is not important under prolonged therapy. The absence of selectivity with respect to acyl-chain desaturation supports the concept of serum PLA2 as an acute-phase protein rather than a regulator of the arachidonic acid cascade.

Adult↗
PubMed1992

[Are humidity filters necessary in the inspired air in the breathing circuit? A new in vivo method of measuring humidity in the air breathed].

Humidification of inspiratory gases under anaesthetic conditions still is a matter of controversial discussion. Physiological humidification and heating of breathing air are preconditions for mucociliary clearance, pulmonary cleaning and defence mechanisms. These functions of the upper respiratory tract are eliminated by application of artificial airways. In general the humidification of inspiratory gases should not remain under 70% of relative air humidity at 37 degrees C. Under clinical conditions it is problematic to ensure sufficiently rapid and reproducible measurements of humidity during breathing cycles. We developed a measuring method that enables to make these measurements without big mechanical device. Aim of this investigation was to measure air humidity in typical semiclosed systems during anaesthesia and semiopen CPAP-respiration. The necessity and efficiency of a heat and moisture exchanger (HME) was to be investigated as well. After approximately 5 minutes there was an inspiratory relative air humidity not below 70% at 28 degrees C (19 mg H2O/l humid air) within the breathing circuit with CO2 double-absorber. By using an HME it is possible to increase relative air humidity within this system to 86% at 29.5 degrees C (25 mg/l). After one hour's respiration with this system without HME a relative humidity of 87% at 30 degrees C (26 mg/l) is reached after replaced HME. Initial relative humidity in a semiopen CPAP-system is about 12% at 28 degrees C (3 mg/l). This is increased to 85% at 29.5 degrees C (25 mg/l) after 15 minutes respiration with HME.(ABSTRACT TRUNCATED AT 250 WORDS)

Air↗
PubMed1985

Effects of enflurane on myocardial ischaemia in the dog.

The effects of experimentally induced, severe coronary artery stenosis on regional changes in myocardial blood supply, cardiac function, and metabolism were studied in 14 dogs. The anterior interventricular branch of the left coronary artery (LAD) was constricted such that arterial inflow was reduced by 80%. Nine dogs were given enflurane in a concentration of 2.2 vol.% (1 MAC) in air, and five animals received no enflurane (controls). Regional myocardial blood supply was measured by the tracer microspheres technique, using 8-micron microspheres labelled with five different radioisotopes. Regional cardiac function (end-diastolic length of the muscle fibres = EDL; segmental shortening during systole = delta L) was estimated with the aid of two ultrasonic crystals which were placed in the subendocardial layer of the myocardium supplied by the LAD. Regional myocardial metabolism (oxygen consumption; lactate extraction) was evaluated from arterial and coronary venous blood samples. The latter were collected selectively from the region supplied by the LAD via the great cardiac vein. The results showed that, during severe coronary artery stenosis comparable to clinical conditions, apart from the known actions on systemic haemodynamics and contractility, enflurane had beneficial effects on regional myocardial variables. This was indicated by reduced regional contraction, measured as EDL and delta L; unchanged subendocardial blood flow without any redistribution; and improved lactate extraction in the ischaemic region.

Animals↗
PubMed1985

[Modification of circulatory behavior by the administration of buprenorphine in the postoperative phase].

Buprenorphin, 0,3 mg i.v., was used in 20 patients in the age of 51 to 75 years for analgesia after surgery for aortic aneurysm. Haemodynamic parameters of peripheral and pulmonary circulation, cardiac output, as well as blood gases were determined during routine postoperative controlled ventilation. The main results were an initial vasodilation and a decrease in heart rate, both of which reduce myocardial oxygen consumption. This effect is beneficial in the presence of sufficient volume substitution and optimal oxygenation in high-risk patients.

Aged↗
PubMed1985

[A simple system for emergency coniotomy].

The successful clinical application of a new emergency cricothyrotomy device is reported. We used it first in a patient who was in acute respiratory insufficiency and could not be intubated because of a large tumour in the pharynx. Emphasis is placed on the description of the easy handling especially for less experienced physicians and of the atraumatic procedure.

Acute Disease↗
PubMed1982

[Anesthesia in patients with concomitant cardiovascular diseases].

Hypertension and coronary heart disease occupy a decisive position among the cardiovascular concomitant diseases. The article presents the pathophysiological interlinks between these two diseased conditions. It is evident that the left ventricle is in danger of being exposed to ischaemia, which must be considered a major risk factor in anaesthesia and surgery. Pretreatment with beta-blockers and digitalis is discussed. To the present day, no generally valid recommendation can be given for a definite method of anaesthesia. It is of decisive importance to protect the patient against sympathetic stimulation by providing for satisfactory analgesia and sedation. The therapeutical concept in case of undesirable intraoperative states of hypertension is explained.

Adrenergic beta-Antagonists↗