Biomedical subjects

K Taeger

Publications and source records attributed to K Taeger.

78 records · Page 5Linked to original sources

PubMed1988

Pulmonary kinetics of fentanyl and alfentanil in surgical patients.

The pulmonary kinetics of fentanyl and alfentanil were studied quantitatively in two groups of five and six surgical patients, respectively, after the induction of anaesthesia. A mixture of one of the opioids and indocyanine green was administered as a bolus. From measurements of the concentrations of the dye in plasma and the opioids in blood, central blood volume and the amount of drug which passed through the pulmonary circulation were calculated. The pulmonary release of fentanyl and alfentanil was calculated from the arterial-mixed venous blood concentration differences. Fentanyl 43.0-86.9% (median 70.9%) and 35.9-79.8% of alfentanil (median 58.6%) were sequestered by the lung on first passage of the opioid-containing blood through the pulmonary capillaries. During the following 14 min, fentanyl was released, apparently from two binding sites (T1/2fast: 0.22 (0.16-0.27) min; T1/2slow: 5.78 (3.65-13.86) min). Initially, there was a rapid release of alfentanil (T1/2: 0.28 (0.08-0.51) min). However, 1-3 min after injection, the arterial-mixed venous blood concentration differences of alfentanil disappeared, although considerable amounts of drug were still present in the lung of five of the six patients studied. It may be expected that a temporary pulmonary sequestration of fentanyl and alfentanil has considerable impact on the time course of their pharmacological effects, on the time necessary to reach their maximum effect and on the intensity and (in case of fentanyl) the duration of these effects.

Adult↗

PubMed1986

[Thiopental distribution in the blood of surgical patients].

The influence of hematocrit, of the concentration of plasma proteins, and of CO2 pressure on the distribution of thiopental in the blood was studied in vitro in 30 venous blood samples. Thiopental was bound to plasma proteins to 80.3-89.2%, mean 85.0%, at a plasma protein concentration of 60 g/l and a pH of 7.37. Considerable changes in the plasma protein concentration had a considerable influence on the binding rate. By halving the protein concentration the free fraction was almost doubled. Increasing the protein concentration to 90 g/l led to binding rates of around 88-89%. When the pCO2 was increased from 40 to 60 torr protein binding decreased slightly, indicating that this barbiturate is mainly bound in its anionic form. At a hematocrit of just under 40 vol.%, 14-34% of the thiopental was absorbed by the erythrocytes. Changes in the plasma protein binding rate influenced the thiopental proportion of erythrocytes, as changes in the hematocrit influenced the plasma thiopental proportion. The concentration of liposoluble thiopental acid physically dissolved in the plasma fluid, just under 8% of the thiopental in the blood, changed relatively little on variation of the hematocrit and the CO2 pressure, thanks to the compensatory function of the plasma proteins and erythrocytes. Since most of the thiopental in the blood is bound to plasma proteins, changes in the protein concentration had the greatest effect on the proportion of thiopental acid of the barbiturate content of the blood.

Anesthesia, General↗

PubMed1986

[Thiopental levels in the plasma during induction of anesthesia].

The thiopentone sodium surge in plasma was investigated in 15 elderly surgical patients and 10 young adults during injection, over a period of 1 minute, of 4 mg of anaesthetic per kg of fat-free body weight (in 18 patients), and 5 mg per kg of fat-free body weight (7 patients). In keeping with prolonged circulation time in old age, thiopentone sodium reached the sampling site faster in the younger patients than it did in the older patients. In the majority of cases, thiopentone sodium concentrations in plasma reached a maximum of between 60 and 80 micrograms/ml. Mean thiopentone sodium concentrations in the older patients were 10% higher, but here values differed so widely that this result must be regarded as coincidental. It was, accordingly, impossible to establish any statistically verifiable differences between young and old patients by estimating the volume of thiopentone sodium distribution shortly after the end of injection. Plasma protein binding, 85% on average, with extremes ranging from 79% to 89% did not depend on thiopentone concentration or age. In the group of patients studied, it was not possible to confirm statistically that the plasma protein concentration influenced the rate of binding. Dosage according to fat-free body weight did not diminish inter-individual differences in plasma concentration-time profiles.

Adult↗

PubMed1986

[Thiopental kinetics in high-dose use].

The kinetics of thiopentone when administered in high doses were investigated in two patients with elevated intracranial pressure and three patients with focal cerebral ischemia. Initial saturation of the tissues is best achieved by a series of infusions with decreasing infusion rate. Administration of a bolus followed by maintenance doses proved unsuitable. The course of concentration under maintenance dosage was extremely variable, mainly due to interindividual and intraindividual variations in clearance. The apparent distribution volumes in these patients (1.38-3.10 l/kg, mean 2.43 l/kg) corresponded to the volumes determined after bolus administration. The total body clearance was low (45.8-103.4 ml/min, mean 72.3 ml/min) and was the reason for long elimination half-times (15.6-25.0 h, mean 23.2 h). Four patients biotransformed thiopentone regardless of the concentration. In one female patient the biotransforming enzyme systems may have been saturated. While conversion of thiopentone to pentobarbitone is generally only of secondary importance, an unusually high plasma pentobarbitone concentration was observed in one patient, reaching 50% of the concentration of the original substance. On the average, thiopentone was 75-80% proteinbound. The binding rate changed considerably with time. It could not be shown that this was influenced by albumin concentration between 25 and 50 g/l. The thiopentone concentration in the ventricular fluid corresponded approximately to that in the plasma fluid. Owing to the variability of the total body clearance and plasma protein binding, and the possibility of changes in tolerance, thiopentone administration must be controlled individually according to the EEG and intracranial pressure. Monitoring of the drug concentration in plasma is recommended.

Adult↗

PubMed1982

[Methohexital for rectal anesthetic induction in children].

To induce anaesthesia, 100 children between 18 months and 7 years of age who had been selected for surgery or invasive diagnosis, received a 10% methohexitone solution in a dosage of 20-30 mg/kg body weight by rectal instillation. The time until onset of sleep, the pulse rate and blood pressure changes, duration of operation, recovery time and any special observations were recorded. Methohexitone concentrations in the plasma were measured in 7 children during rectal induction of anaesthesia. It was found that induction of anaesthesia in children by rectal application of 20-30 mg/kg body weight methohexitone is a safe procedure which does not cause discomfort to the children and is easily handled by the physician. The methohexitone levels in the plasma are not higher than those after intravenous administration.

Anesthesia, Inhalation↗

PubMed1976

The fate of phenylhydroxylamine in human red cells.

Phenylhydroxylamine added to human red cells under aerobic conditions and in the presence of glucose was partly reduced to aniline. About half the hydroxylamine was recovered as amine after a 2-hr incubation. The aniline, after acetylation, was identified as acetanilide by melting point, Rf-value in TCL as well as UV, IR, and NMR spectroscopy. The fate of the remaining phenylhydroxylamine was followed by use of 14C-labeled phenylhydroxylamine. About 30% of the total radioactivity was bound to hemoglobin or other proteins and about 20% was found in highly polar low-molecular substances which were insoluble in organic solvents. The elucidation of the sites at which phenylhydroxylamine was bound to hemoglobin was complicated by the lability of the bonds. When purified human hemoglobin had reacted with radioactive phenylhydroxylamine, large proportions of the radioactivity bound to hemoglobin were removed by treatment with acid or with PMB for separation of alpha- and beta-chains. The radioactive compound liberated from hemoglobin by acid was found to be aniline. After reaction with phenylhydroxylamine the number of SH groups titrable with PMB was found to be diminished. Pretreatment of hemoglobin with N-ethylmaleimide or PMB decreased the amount of phenylhydroxylamine bound to hemoglobin but did not fully prevent the reaction. Tryptic digestion of hemoglobin after reaction with radioactive phenylhydroxylamine yielded tryptic peptides with lower specific activity than that of hemoglobin. Chymotryptic digestion of the tryptic core yielded a core with specific activity much higher than that of hemoglobin. Fingerprinting of the tryptic or chymotryptic hydrolyzates showed the presence of peptides with high and other ones with low or no radioactivity and of radioactive compounds which did not react with ninhydrin. In the covalent binding of phenylhydroxylamine to globin the SH group beta93 plays an important role, but other yet unknown sites are also reactive.

Acetanilides↗