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Biomedical subjects

R Zander

Publications and source records attributed to R Zander.

At least 55 records · Page 3Linked to original sources
PubMed1993

Perioperative respiratory monitoring of oxygen transport.

Oximetry nowadays is understood as the in vitro measurement of O2 saturation (sO2, %) and hemoglobin (Hb) derivatives (%) using 4-7 wavelengths (CO- and Hem-oximeters). Pulse oximeters, using only 2 wavelengths, are designed for the continuous noninvasive measurement of the arterial partial O2 saturation (psO2, %) in vivo. Light-emitting diodes allow light to pass through the peripheral site of measurement with red and infrared light to enable a distinction between oxygenated and deoxygenated hemoglobin during a recorded pulse wave. In case of physiological concentrations of Hb derivatives the determination of psO2 is performed with clinically relevant accuracy of +/- 2-3%. However, at carboxyhemoglobin (COHb) concentrations above normal, under normoxia as well as under hypoxia the accuracy of measurement varies considerably among the instruments from different manufacturers. In the case of elevated methemoglobin (MetHb) concentrations, the situation is completely different. With increasing cMetHb, the psO2 is still the value required, but success depends on the concentration of MetHb: under normoxia psO2 is increasingly underestimated, whereas under hypoxia increasing overestimation must be anticipated. Provided there is a constant Hb concentration, knowledge of the initial sO2, and absence of the derivatives COHb and MetHb as well as of severe perfusion disorders, pulse oximetry is suitable for perioperative respiratory monitoring of oxygen transport.

Carboxyhemoglobin↗
PubMed1993

[Critical limits of hemodilution: theoretical principles].

For daily clinical practice an isovolemic hemodilution down to an arterial O2 content of 10 ml/dl, corresponding to a hemoglobin content of 7.5 g/dl or a hematocrit value of 22.5%, is described as a tolerable value, as long as normovolemia and normoxia (no disturbances of lung function) are guaranteed and local restrictions in perfusion (coronary or cerebral sclerosis) are excluded. This value is not derived from the mixed venous O2 status but from the situation of the myocardium as the main limiting organ for anemic hypoxemia. Compensation of anemia is regulated hemodynamically: First, by an increase in stroke volume; secondary, by an increase in heart frequency and, tertiary, by an increase in venous utilization. The last may reach 100% without any restrictions from the so-called critical mixed venous pO2 as a possible limiting factor for hemodilution.

Coronary Circulation↗
PubMed1993

[Physiology and clinical aspects of the extracellular bicarbonate pool: plea for cognizant use of HCO3-].

OBJECTIVE: Derived from literature data the function of bicarbonate (HCO3-) is described together with its extracellular pool, the regulating organs, and the clinical variations. DATA SOURCES AND SELECTION CRITERIA: The medical German and English literature was reviewed. No special literature retrieval was performed. Results from measurements at the author's laboratory were used. RESULTS: HCO3- may be described as the most potential nonrespiratory buffer base. For a 65 kg patient, the extracellular HCO3- pool amounts to approximately 350 mmol with a maximum tolerance limit of +/- 200 mmol. An influx of H+ ions (acidosis) and/or a reduction in the pCO2 (hyperventilation) will reduce this pool, whereas alkalosis and hypoventilation will enlarge it. The lungs (in close cooperation with the erythrocytes), liver and kidneys all contribute to the regulation of this HCO3- pool. The paramount organ for this regulation seems to be the liver, since it is able, even within a period of only a few hours, to eliminate much larger amounts of H+ ions (and correspondingly release HCO3-) than the kidneys are able to eliminate even under extreme conditions. It is primarily the liver which regulates the size of the HCO3- pool through the metabolism of the so-called metabolizable anions (bases) such as acetate, lactate, malate and citrate. The metabolism of these anions in the form of acetic, lactic, malic or citric acid requires (per mol) 1 mol H+ (acetate, lactate), 2 mol H+ (malate) or even 3 mol H+ (citrate), with the corresponding release of HCO3-. Iatrogenic alterations in the HCO3- pool occur more frequently than previously assumed. Infusion solutions may lead to a dilution acidosis (dilution of HCO3-), an infusion acidosis (addition of H+) or an infusion alkalosis (administration of metabolizable anions). CONCLUSION: An improvement in the declaration accompanying infusion solutions is recommended according to their actual pH-dependent composition. In particular, the concepts of base excess (BE, mmol/l) and BE pot. (mmol/l) should be introduced, in order to give an indication of potential alterations in the HCO3- pool after infusion and metabolism. This also applies to blood derivatives, where transfusion acidosis as well as alkalosis may occur, and in hemodialysis and peritoneal dialysis where the occurrence of acidosis and alkalosis during therapy need to be reckoned with.

Acid-Base Imbalance↗
PubMed1992

[Insulin-like growth factor I--a connecting link between nutrition and growth].

The influence of an increasing protein supply in combination with soybean oil upon the IGF-I concentration in the serum in correlation with growth was measured on 8 x 10 male Wistar rats. With a casein content of 0% in the food, the IGF-I level was 0.13 +/- 0.02 rU/ml. An IGF-I plateau of 0.74 +/- 0.07 rU/ml was reached at some 15% casein. The additional application of 3% soybean oil increased the IGF-I concentration significantly (P less than 0.01) up to 0.95 +/- 0.16 rU/ml. The investigations show a specific increase of the IGF-I synthesis by the addition of oil, which is paralleled by a further stimulation of the growth of the rats. The nutrition-dependent IGF production in the peripheral tissues (mainly liver) represents the connection link between the growth hormone axis (genetically potential growth) and the growth realizable depending on the supply with nutrients.

Animal Nutritional Physiological Phenomena↗
PubMed1992

[Checking the precision of capnometers].

Capnometry, i.e. measurement of CO2 concentration (cCO2, vol%) and calculation of the respective CO2 partial pressure (pCO2, mmHg), is simple to apply, but the user must understand its principles of operation in order to appreciate its power and its limitations. However, sidestream capnometers use to dry the humidified respired gas (37 degrees C, pH2O 47 mmHg) for methodological reasons, thus increasing pCO2 by ca. 6% which, in turn, requires correction. With infrared spectroscopy, overestimation of pCO2 in presence of N2O and underreporting of pCO2 in presence of O2 also require to be corrected. These require either knowledge of the respective gas concentrations (mainstream analyzers) or adequate (i.e. correct) measurement (some sidestream capnometers). Changes in barometric pressure (pB) must be also either known or be measured automatically. Evaluation of the precision of capnometers must therefore focus on, (1) the possible pH2O correction, (2) the possible effects exercised by O2 and N2O, and (3) the possible dependence on barometric pressure. Two mainstream (Capnolog D/Dräger; Sirecust 404-1/Siemens) and eight sidestream capnometers (AGM 1304/Brüel & Kjaer; SARAcap A. G. and SARA-trans/Biomedical Systems/Hellige; Capnomac and Normocap 200/Datex/Hoyer; CO2 Monitor/Dräger; Nellcor N-1000/Nellcor/Dräger; Multinex/Datascope) were investigated. Dry and humidified gases (37 degrees C) of defined composition in respect of CO2, O2, N2, N2O, and H2O, were used for evaluation. The results prove reproducibility of ca. =/- 1 mmHg for the 10 capnometers within the 30-50 mmHg pCO2 range.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesiology↗
PubMed1992

[The extraction particles from winter rapeseed with different glucosinolate fractions in swine with regard to the iodine supply. 3. Apparent digestibility of crude nutrients with special regard to the carbohydrate and nitrogen balance].

In two digestibility and N-balance experiments the following solvent extracted meals were examined in a grain (barley and wheat in equal parts) or in a starch diet with four female pigs/group fitted with urethra catheters during the 5 days sampling period: 48% soyabean meal (SBM) (1), 24% conventional rapeseed meal (RSM) (2), 24 (3) or 48% (4) RSM from a newly bred low glucosinolate variety, groups 1 to 4 with grain, 48% low glucosinolate RSM (5) or 48% SBM (6) both with starch. In numeric order of the groups 88, 85, 86, 84, 79 and 89% N were digested. Pigs responded to the additional faecal N excretion from RSM diets by a lower urinary N excretion and thus they reached the N-balance of the animals fed on SBM. In numeric order of the groups 86, 79, 80, 73, 73 and 92% of the organic matter of the solvent extracted meals were digested. In comparison with SBM even 48% RSM in the feed significantly lowered the digestibility of organic matter. Using detergents the additional faecal organic matter excretion of RSM versus SBM could quantified as two third lignin. In the case of 24% RSM in the diet--i.e. 15% of the carbohydrates given--the carbohydrate digestibility is estimated with a high error, that an energetic feed value should not calculated. Investigating 48% SBM or RSM respectively in a grain diet the net energy content was 9.8 MJ (666 Energetic Feed Units, EFU pig) or 8.3 MJ (569 EFU pig)/kg dry matter (DM). Based on the starch diet, however, little relevant for estimation of normal pig diets, there were evaluated 10.6 MJ (720 EFU pig) for SBM and 8.3 MJ (567 EFU pig) net energy/kg DM for RSM.

Animal Feed↗
PubMed1992

[Measurement errors in determination of electrolyte concentrations with ion selective electrodes in the presence of inorganic or metabolizable anions].

Ion-selective electrodes (ISE) from various manufacturers were tested with regard to their accuracy in determining the concentrations of sodium, potassium and calcium in aqueous solutions when uni- or polyvalent, inorganic or organic anions are being present in physiological concentrations. The results obtained by all measuring instruments using ISE revealed that the presence of anions such as acetate, citrate, malate, lactate, phosphate or sulfate, either in physiological or therapeutic concentrations, may lead to considerable errors when determining the concentrations of sodium and calcium. A certain caution is therefore recommended in order to minimize the risk when using ISE for the electrolyte diagnosis of infusion solutions, blood derivatives, dialysates and urine samples.

Acid-Base Equilibrium↗
PubMed1991

First results on the incorporation and excretion of 15N from orally administered urea in lactating pony mares.

Two lactating pony mares were given oral offers of 20 g 15N urea [95 atom-% 15N-excess (15N')] on 6 subsequent days. About 80% of the consumed 15N' were excreted via urine and faeces, but only about 2% via milk. The 15N' secreted via milk-lysine only amounted to 0.04% of the 15N' intake. The recovery was about 90% in each case. Tissues with active metabolism had an unexpectedly high labelling (greater than 0.3 atom-% 15N'). The low extent of the conversion of oral urea N into milk-lysine speaks against an essential participation of the enteral synthesis in meeting the amino acid requirement of lactating mares. It was already concluded from this results that the determination of the amino acid requirement will be necessary for this group of performance.

Administration, Oral↗
PubMed1990

Tumor tissue oxygenation as evaluated by computerized-pO2-histography.

A computerized pO2 measurement system with a novel electrode motion pattern (Sigma-pO2-histography) was evaluated in vitro and in vivo. The system was found to be reliable in 0.9% saline and 10% hydroxyethylene starch solution and in fresh donor blood. Marked deviations were found in lipid and hemoglobin solutions and in fluorocarbon emulsions. Histograms obtained in rat liver, mouse muscle, and subcutis were similar to previously reported distributions. Direct comparison between Sigma-Eppendorf and self-constructed Whalen-type electrodes in hypoxic tumors gave similar results. A large series of measurements indicated that hypoxic and anoxic tissue areas were frequently found both in isografted rodent and in xenografted human tumors. The extent of oxygen deprivation depended on the cell line studied, tumor size, implantation site, the vascularity, and the actual tissue perfusion. Pentobarbital anesthesia redistributed the tumor oxygenation without affecting the median pO2 value. Tumors growing in a pre-irradiated bed were less oxygenated than those at untreated sites. Hyperthermia at therapeutically relevant temperatures reduced pO2 levels in adequately oxygenated tumors whereas little change was detected in poorly oxygenated tumors. First measurements in tumors in patients revealed marked inter- and intratumor heterogeneity. It is concluded that this novel technique is suitable for routine measurements of tissue oxygenation of solid tumors in situ.

Animals↗
PubMed1990

[The effect of different high doses of field peas on the digestibility of their crude nutrients in colostomized laying hens].

Five groups of five colostomized laying hens each received 0 g, 15 g, 30 g, 45 g and 60 g peas of the variety Grapis per animal and day with Triticum rations. The apparent digestibility of the crude nutrients of the rations and the peas was determined, ascertained according to the difference method in dependence on their quotas in the rations. The digestibility of the N-free extracts of the peas increases by 3 digestion units each under the influence of the increasing intake of peas, so that the digestibility of the organic matter of the peas increases with the growing quota. On an average of the 20 individual values the following digestion values for the pea variety Grapis are indicated: organic matter 66.9%, crude protein 78.5%, crude fat 48.7%, N-free extracts 70.3%. Energy concentration amounts to 572 EFU-hen/kg dry matter.

Animal Feed↗
PubMed1990

Oxygen parameters of blood: definitions and symbols.

Definitions and symbols for relevant parameters of the oxygen status of arterial blood are recommended. The recommendations are as simple as possible, easy to understand, and devoid of misinterpretations and double meanings. The authors propose no new definitions for limited new methods, no combination of symbols and methods, and no association between definition, symbol and commercial name.

Abbreviations as Topic↗
PubMed1990

The oxygen status of arterial human blood.

The oxygen status of arterial human blood is described at least by four variables: Oxygen partial pressure (pO2, mmHg), oxygen saturation (sO2, %), hemoglobin content (cHb, g/dL) and oxygen content (cO2, mL/dL). Beside perfusion, however, the oxygen supply of all organs is decisively determined by the mean capillary pO2 which itself is primarily dependent on the arterial cO2. Therefore, the oxygen availability (cardiac output x caO2, mL/min) may be described by the cO2 value in arterial blood or those variables who determine the latter one. The diagnostic significance of the O2 variables of the oxygen status consequently increases in the order of pO2, sO2 (cHb) and cO2. In arterial blood, oxygen partial pressure is the result of O2 diffusion within the lungs into the blood (lung function). Oxygen saturation describes the portion of chemically bound oxygen expressed as O2Hb in relation to total Hb (Hb + O2Hb + COHb + MetHb). Oxygen content is the total amount of oxygen in blood chemically bound plus physically dissolved. Under pathophysiological conditions the diagnostic significance becomes very clear. Disturbances of lung function decreases all three variables, pO2 (hypoxia), sO2 (hypoxygenation) and cO2 (hypoxemia), to produce hypoxic hypoxemia. Carbon monoxide poisoning or methemoglobin formation decreases two variables, sO2 and cO2, where the pO2 remains normal and results in toxic hypoxemia. Anemia with a decrease in the hemoglobin content lowers cO2 only, while pO2 and sO2 remain normal (anemic hypoxemia).

Anemia↗