Arterial concentration

In addition, the brain can make limited use of other substrates for metabolism, e.g. during fasting (see above). Under normal circumstances, the venous lactate concentration is slightly higher than the arterial concentration,... 

Table 13.5 Arterial concentrations of some fuels during prolonged physical activity in human volunteers "...

Table 21.4 Arterial Concentrations of Metabolites in Normal, Fasting, and Untreated Diabetics (mM)...

Therapeutic Concentration. During surgical anaesthesia, concentrations in blood are usually in the range 22 to 84 pg/ml. Venous blood concentrations lag behind arterial concentrations during induction and decline less rapidly during recovery. 

Sato, Y., Eriksson, S., Hagenfeldt, L., and Wahren, J., Influence of branched-chain amino acid infusion on arterial concentrations and brain exchange of amino acids in patients with hepatic cirrhosis, Clin. Physiol., 1, 151, 1981. 

The total amount of contrast material delivered to the tissue via the arteries is the product of the CBF times the integral of the arterial concentration, According... 

It follows that the rate of contrast accumulation will peak when the arterial concentration is maximal ... 

Hence, CBF is the ratio of the maximum slope of Q(t) to the maximum arterial concentration. This is analogous to a differentiation with respect to time of the Mullani-Gould formulation, and is called the maximum slope method. The principal advantage of the maximum slope method is the simplicity and hence speed of calculation of the perfusion values. A very high rate of contrast agent injection, however, is required - typically at least 10 mL/s - in order to satisfy the no venous outflow assumption [28, 122]. These rates cannot be routinely achieved in clinical practice. The no venous outflow assumption is clearly an oversimpliflcation, and this method yields relative, rather than absolute, perfusion measurements, making interpatient or interinstitutional comparison of results difficult. 

Sharrock, N.E. Mather, L.E. Go, G. Sculco, T.P. Arterial and pulmonary arterial concentrations of the enantiomers of bupivacaine after epidural injection in elderly patients. Anesth. Analg. 1998, 86, 812-817. 

The greater the blood/air partition coefficient, the closer the arterial concentration will be to the venous concentration. 

Metabolic pathways due to its lipophilicity, epidural clonidine is quickly absorbed into systemic circulation, with peak arterial concentrations after 10 minutes, peak venous concentrations after 30-45 minutes, and peak CSF concentrations after 30-60 minutes. The liver is responsible for metabolism of 50% of clonidine into inactive metabolites. Approximately two-thirds of clonidine, metabolized and unmetabolized, are excreted renally. While the effects of epidural clonidine may last only 3-5 hours, elimination takes longer. The plasma elimination half-life of clonidine is 22 15 hours and can be prolonged in renal failure [1,2]. 

Rychen, G. and Nunes, C.S. (1995) Effects of three microbial probiotics on postprandial porto-arterial concentration differences of glucose, galactose and amino-nitrogen in the young pig. Brit J Nutria, 19-26. 

Among the other AA (Table 1), the uptake of AA from group II (He, Leu, Lys, Val) and the uptake of Ala and Glu (NEAA) did not vary in the same way in response to increasing protein and GN supplies. The mammary uptake of AA from group II increased in response to increasing protein supply as did their AV differences (one component of the uptake). The AV difference increased in relation with the increased arterial concentration, probably due to their increased intestinal supply. In addition, the mammary U O ratio of group II AA increased. This excess uptake relative to milk protein output could supply extra carbon for oxidative pathways or as carbon skeletons for the synthesis of other... 

Digestible in the Intestine (PDIE INRA, 1989) His+Met+Phe+Tyr Arterial concentration Ai1erio venous differences Half-udder net uptake Ile+Lys+Leu+Val Uptake to output in milk protein ratio "Alanine plus glutamate "b-Hydroxybutyrate X = intestinal glucose and ruminal propionic acid (infusions plus diet). 

Conversely, the uptake of group II AA was not affected by GN supply because the two components of uptake varied in opposite direction the AV difference decreased as arterial concentration while MPF increased. In the absence of any significant increase in net uptake of group II AA by the mammary gland, the increased uptake of nitrogen required for the increased milk protein yield could be supplied... 

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