Biomedical subjects
Publications and source records attributed to R Dennhardt.
Following continuous epidural anaesthesia, the urine volumes of patients were collected. By gas-chromatographic analysis 6 metabolites of bupivacaine were identified: 1. Desbutylbupivacaine; 2. 3'-Hydroxy-bupivacaine; 3. N-Butyl-pipecolyl-2-amide; 4. and 5. monohydroxylated isomeres on the piperidine ring; 6. 4'-Hydroxy-bupivacaine.
With an in vivo-perfusion-technique the influence of unconjugated bile salts (cholate, desoxycholate) on the net electrolyte and volume absorption is studied in the jejunum of conscious rats. The applied doses correspond to physiological concentrations in the intestine of rats. Control experiments were performed in the same animal. Cholate and desoxycholate diminish the net electrolyte and volume absorption resp. cause a net secretion. The effects are largely reversible. The extent of net volume absorption depends on the applied dose of each bile salt. The possible mode of action of unconjugated bile salts on the electrolyte and water absorption in the small intestine is discussed.
Experiments were carried out in different segments of the intestine of unanaesthetised rats to assess the effect of vasopressin on intestinal absorptive processes. The following data were observed. (1) Within a physiological range of doses (Aziz, 1969), ADH diminished the net sodium absorption mainly by reducing the unidirectional sodium influx, whereas the behaviour of the efflux was not uniform. (2) The unidirectional volume fluxes showed the same behaviour as did the sodium fluxes. (3) ADH produced an oral-aboral gradient (jejunum greater than ileum greater than colon). (4) ADH did not significantly change the transfer of actively transported sugars; it did influence, however, passively transported substances. (5) During the intravenous application of ADH, a substance was secreted into the perfusion solution which diminished the absorption of volume and electrolytes. (6) Cyclic AMP acted on intestinal absorption in the same way as did ADH. In view of these results two mutually independent transport pathways for sodium and water are supposed, one of which is influenced by ADH or cAMP. Based on a two membrane model, an ADH mechanism is discussed: the permeability of the luminal membrane system is enhanced in the presence of vasopressin.
The application of a two-channel flow-through analyzer with carrier membrane disc electrodes for the electrochemical analysis of heparinized blood, plasma or serum is described, its capabilities discussed and results of direct patient measurements presented.
Arterial haematocrit and blood electrolyte concentrations are measured continuously by conductometry in three hemodialysis patients. Haematocrit elevation during meals, particularly when rich in carbohydrates, indicate fluid losses into the gut. Simultaneous biphasic responses in electrolyte concentration indicate osmotic and diffusional shifts of water and electrolytes. Similarly, blood volume and electrolyte concentration changes can be followed during and after intravenous infusion of colloid and crystalloid solutions. The quantitative aspects of such measurements are discussed.
Anaerobically prepared serum samples from healthy subjects were simultaneously analysed for Ca++ in a flow-through-system of three ion selective disc-electrodes (electrochemical multimeasurementsystem). Two of the sensors contained electrically charged ligands, the third contained a neutral carrier. With neutral carriers an improvement of performance was noted in that there was a large increase in selectivity toward H+- and NH+4-ions and a distinct enhancement of reproducibility.
Explore the source record for details and available documents.
A method is described enabling blood concentrations and urinary and biliary excretion of bupivacaine to be estimated in unanaesthetized rats. After enteral application of bupivacaine, the urine volumes of 40 rats are collected, cleared off and analysed by gas chromatography. 5 fractions are obtained, of which the structures are identified by mass spectrometry and nuclear magnetic resonance. The following five metabolites could be identified: (1) Desbutyl-bupivacaine, (2) 3'-Hydroxy-bupivacaine, (3) N-Butylpipecolyl-2-amide, (4, 5) mono-hydroxylated isomeres on the piperidine ring.
To avoid the influence of general anaesthetics on the functions of most organ systems, the present experiments were carried out in unanaesthetized rats. Blood concentrations in the aorta, V. portae and Vv. hepaticae as well as urinary and biliary excretions of bupivacaine were studied after either intravenous or enteral administration. From the course of the aortic bupivacaine concentrations after i.v. injection the following pharmacokinetic data were derived: t1/2 = 24,7 min; k2 = 1,467 h; V = 1,492 1. Absorption of bupivacaine from the jejunum is rapid. The hepatic clearance of bupivacaine in the rat is 12 ml/kg b.w..min-1. The biliary excretion of bupivacaine in the rat is very small; therefore the enterohepatic circulation of this substance may be considered neglible.
In 23 patients 18 to 73 years old transcutaneous PO2, relative local perfusion and cardiorespirogram during induction and end stage of anaesthesia were monitored. This method allows continuous sufficiently exact estimation of PaO2. The comparison between tcPO2 and corresponding blood gas analysis from arterial samples showed a good correlation of r=0.94. Thus continuous tcPO2 registration enables quick diagnosis of hypoxia and its therapy.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.