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Biomedical subjects

I Rietbrock

Publications and source records attributed to I Rietbrock.

At least 19 recordsLinked to original sources
PubMed1987

Age-dependence and free fatty acid modulation of binding kinetics at the benzodiazepine binding site of serum albumin in neonates and adults determined using fast reaction methods.

Binding kinetics at the benzodiazepine binding site of albumin have been determined as a function of age and fatty acid concentration in serum from 32 neonates (umbilical cord blood), 28 adults aged 23-65 years and 24 adults aged 66-101 years using fluorescence-time curves obtained in a Durrum-Gibson stopped-flow apparatus and the specific marker ligand dansylsarcosine. The binding reaction can be described by a 2-step mechanism characterised by four constants: the association rate constant k2 and dissociation rate constant k-2 for the rate limiting step-2; the affinity constant KA' for the formation of an unstable intermediate complex in step-1; the affinity constant KA for the overall reaction. There were marked differences in k2 between the three groups of subjects with highest values occurring in neonates (mean: 296 s-1), intermediate values in adults aged 23-65 years (mean: 200 s-1, P less than 0.001) and lowest values in adults aged 66-101 years (mean: 144 s-1, P less than 0.001). The dissociation rate constants (k-2) averaged 18.5 s-1 overall, showed only minor changes with increasing age and corresponded to dissociation half-lives of 42 ms, 38 ms and 33 ms for neonates, adults 23-65 years and adults 66-101 years respectively. KA' in neonates and in the group of elderly subjects were lower than in adults aged 23-65 years.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Dose-response relationship and serum concentrations of methohexital and hydroxymethohexital following rectal anesthesia induction with 1% and 5% methohexital solutions in children].

Dose-response-curves for rectal induction of anaesthesia in children with 1%- or 5%-methohexitone-solutions and dosages of 5, 10, 15, 20 and 25 mg/kg body wt. were obtained in 10 groups of 20 children. Methohexitone and hydroxy-methohexitone serum-levels were compared in another 23 children after application of 1%- or 5%-methohexitone-solutions at dosages of 15 and 20 mg/kg body wt. The sleep induction quota after 1%-methohexitone-solution in the 20 and 25 mg/kg body wt.-dosages was significantly higher, 20% and 25% respectively, and the mean sleep induction time shorter, 37% and 45% respectively compared with results after 5%. The change after 15 mg/kg body wt. was not significant. A study of dosages 5 and 10 mg/kg body wt. was discontinued due to insufficient effect. Methohexitone serum-levels ranged from 0.7-8 mg/l. All of the children after the use of 1%-methohexitone-solution, and only 60% after 5%-methohexitone had serum concentrations above the sleep inducing "borderline" concentration of 2 mg/l. The differences between mean methohexitone and hydroxy-methohexitone-serum-levels were not significant due to the small groups and the wide range of results. We conclude that individual dosages of 15 or 20 mg/kg body wt. 1%-methohexitone-solution should be applied according to clinical criteria such as physical and psychic status of the child.

Anesthesia, Rectal↗
PubMed1984

pH-control via secretin or antacid: prophylaxia of stress ulcers in high-risk surgical patients.

The efficacy of an antacid or synthetic secretin in elevating the intragastric pH above 4 was tested in a controlled, prospective study. Twenty-one high-risk surgical patients received an antacid and 17 secretin. Antacid prophylaxis resulted in a significantly higher intragastric pH than with secretin. This was especially true in patients with several risk factors. The percent of secretin patients with a pH below 4 was higher. An increase in dosage was necessary in 4 of the 17 patients receiving secretin and in none of those receiving antacids. One stress ulcer hemorrhage occurred during secretin prophylaxis.

Aged↗
PubMed1984

[Intragastric pH increase using antacids or secretin for stress ulcer prevention in surgical risk patients].

The efficacy of an antacid or synthetic secretion on elevations in intragastral pH above 4 was tested in a controlled prospective study. 21 surgical high risk patients received an antacid, and 17 secretin. Antacid prophylaxis resulted in a significantly higher intragastral pH than with secretin. This was especially true in patients with several risk factors. The percentage of secretin patients with a pH reduction below 4 was higher. An increase in dosage was necessary in 4 of the 17 patients receiving secretin and in none of those receiving antacids. One stress ulcer hemorrhage occurred during secretin infusion.

Aged↗
PubMed1982

[Cimetidine with suture ligature of ulcers - an alternative in the treatment of severe acute gastroduodenal ulcer hemorrhage].

The results of SPV with suture ligation of the ulcer (n = 60), suture ligation combined with postoperative Cimetidine medication (n = 20) and suture ligation alone (n = 20) for severely bleeding gastroduodenal ulcers were studied retrospectively and compared. No significant difference could be found between suture ligations of the ulcer combined with SPV or Cimetidine concerning recurrent bleeding and specific or overall mortality. Their rate were highest after suture ligation alone as well in bleeding duodenal ulcers as in gastric ulcers.

Acute Disease↗
PubMed1981

Verapamil disposition in liver disease and intensive-care patients: kinetics, clearance, and apparent blood flow relationships.

Verapamil kinetics have been determined in liver disease (mainly in cirrhotic patients), in intensive-care patients, and in healthy control subjects. Areas under the concentration-time curves (AUCs) after intravenous 5-mg and oral 80-mg doses were used to calculate systemic blood clearance, intrinsic blood clearance, and bioavailability of verapamil in patients and to calculate apparent hepatic blood flow. Intravenous data showed that verapamil clearance was reduced in all patients with liver disease (mean = -66%), but intensive-care patients were a more heterogenous group in which some patients had increases (five patients; mean = +72%) and others had decreases (two patients; mean = 6-57%) in verapamil clearance. The changes in clearance corresponded to changes in the half-time for the beta-phase (t1/2 beta). Verapamil bioavailability is low, and the intensive-care patients and healthy subjects examined it ranged from 13% to 21%. There was considerable variation in liver disease subjects, in whom verapamil bioavailability ranged from 3.8% to 64%. THe systemic clearance of verapamil correlated linearly with calculated apparent hepatic blood flow (r = 0.99; regression coefficient = 0.87). In the case of one liver patient the kinetic results could be used to confirm the clinical diagnosis of hepatic shunts. It is concluded that there are clinically significant changes in verapamil elimination in liver disease and in intensive-care patients. For patients with normal hepatic vascular anatomy, these changes can be explained in terms of differences in hepatic blood flow.

Adolescent↗
PubMed1981

Hexobarbitone disposition at different stages of intensive care treatment.

The pharmacokinetics of hexobarbitone were investigated in 22 patients in an intensive care unit. The results were compared with those obtained in a healthy group for three time periods: 3rd or 4th day (I), 5-8th days (II) and 13-29th days (III) of treatment. Hexobarbitone 7.32 mg per kg of body weight was administered by i.v. infusion in 60 min. At the end of the infusion, the mean plasma concentration of group I was 71% greater than control group; groups II and III were near to control. In all patients the post-infusion concentration-time course of hexobarbitone could be described by two-compartment kinetics. The biphasic decrease in plasma concentration of hexobarbitone was more rapid in groups II and III, than in either the control group or in group I. At the beginning of treatment patients generally showed an unchanged hexobarbitone half-life, a slightly decreased plasma clearance, a reduction of approximately 50% of the initial distribution volume. (V1) and a reduction of 44% of the distribution volume at steady state. In groups II and III the mean of these values were comparable to control. However, plasma clearance had increased by about 87% in group II compared with control, and after 2-3 weeks (group III) by about 143%. Correspondingly, half-life was reduced by 45% and 58% respectively. The pharmacokinetics were not related to change in liver function. The presence of clinical and bacteriological signs of septicaemia was closely associated with an enhanced hexobarbitone clearance.

Adult↗
PubMed1981

[Differential peridural analgesia for vaginal delivery. A randomised study of its influence on the progress and mode of delivery (author's transl)].

This randomised study of 611 deliveries deals with the side effects of a modified extradural analgesic technique. The modification is based on a flexible reduction of local anaesthetic concentration (bupivacaine) which allows a reliable analgesia without a marked loss of labour sensation and bearing down reflex. Randomisation was achieved by offering this analgesia to the parturients in an alternating 24 hours rhythm. Statistical comparisons were carried out for the following groups of deliveries: 1. for deliveries on both of the two alternating days (Group A). 2. for deliveries with and without extradural analgesia of the peridural days (Group B). - 3. for all deliveries with and without extradural analgesia (Group C). - 4. For deliveries without extradural analgesia on "peridural days" and on "alternating days" (Group D). - The main subjects of investigation were the duration of the two stages of delivery, the dynamics of both the cervical dilation and the movement of the fetal head and the frequency, modes and causes of operative and instrumental deliveries. The safety of the analgesic technique was investigated by evaluating its influence on the status of the newborn and on the maternal regulation of body temperature and circulation. The results were obtained as follows: 1. In the group of parturients who had chosen extradural analgesia several antenatal factors accumulated which evidently had a greater influence on the course of delivery than the analgesic technique itself. - 2. The low concentration of local anaesthetic adapted to the labour pain produced a sufficient analgesia in almost every case. - 3. The duration of both stages of delivery was not altered directly by this technique. An average increase of the duration of the second stage by 116 minutes was due to postponed indications of instrumental and operative deliveries by analgesia. - 4. There was no influence on the overall frequency of operative and instrumental deliveries. Extradural analgesia, however, significantly reduced the frequency of caesarean sections to the same extent as it increased instrumental deliveries from the bottom of the pelvis. - 5. The extradural analgesia had no influence on the status of the newborn. - 6. The regulatory mechanisms of circulation and body temperature were not altered by this dosage of extradural analgesia.

Adult↗
PubMed1980

Current knowledge on pharmacokinetics of halothane and enflurane.

Blood solubilities of halothane and enflurane are in a favourable range and differ only for 21%. There are some pharmacokinetical advantages to enflurane compared to halothane, but more because of its lower tissue/blood partition coefficient than due to the difference in blood solubility. The differences in physical behaviour are of more practical significance during recovery than during induction. With the use of enflurane recovery will be more rapid and somewhat less influenced by the duration of anesthesia and by alterations of distribution capacity. With both agents induction can be made faster by adjusting to a higher inspiratory concentration, whereas the waking-up time is commonly reduced by starting recovery from a lower alveolar concentration immediately at the end of operation. Hyperventilation in this period is limited by the resulting hypocapnia with reduced brain perfusion.

Cardiac Output↗
PubMed1978

[Plasma concentrations of digoxin in patients under intensive care conditions and in patients undergoing anesthesia and operation (author' transl)].

Pharmacokinetic behavior of digoxin or beta-acetyldigoxin was examined in 66 patients (27 patiets under intensive care conditions, partially with controlled breathing, 22 patients undergoing extirpation of the uterus and 17 patients treated with radium or chemotherapeutics; 19 males and 47 females) by determining plasma concentrations of digoxin (PDC). After intravenous and oral application with a maintenance dose of 0.20--0.50 mg/day blood was taken daily during a 2 to 3 week period, resulting in 510 determinations. 24 hours after the first application of 0.50 mg digoxin i.v. the mean values of PDC amounted to 0.62 +/- 0.08 ng/ml. After 0.40 or 0.25 mg digoxin per day i.v. therapeutical concentrations could be observed at the third vs fifth day. An equilibrium of PDC was reached on the 6th day after starting digitalization using maintenance doses. Intravenous application of 0.25, 0.40 or 0.50 mg digoxin per day resulted in a mean steady state of 0.68 +/- 0.37, 0.86 +/- 0.33 or 1.27 +/- 0.49 ng/ml PDC, respectively. The results were significantly different (p less than 0.01--0.001). Serial measurements indicated a great variation of PDC. In patients without renal failure the intraindividual variation of the plasma concentrations was maximal 37.4% referring to the mean steady state, interindividual 37.1% and the evaluation of the inter- and intraindividual differences amounted to 54.1%. After oral administration of digoxin (maintenance dose: 0.50 mg/day) or beta-acetyldigoxin (maintenance doses: 0.20--0.40 mg/day) differences in PDC of 38.3% and 29.7% were obtained. Body weight, age and serum creatinine concentration were partly responsible for the variance of PDC. Multiple linear regression between stead state PDC and dose, age, body weight and serum creatinine concentration revealed 62.1% of the variance of the PDC after intravenous administration of digoxin. After oral administration of beta-acetyldigoxin 39.9% were obtained. Thus, 40% of the variance were caused by differences in distribution and elimination of digoxin after i.v. application. After oral application additional 20% of the variance could be attributed to resorption and possible disturbances.

Cardiac Glycosides↗
PubMed1977

[Hydroxy-ethyl-starch as plasma substitute in transurethral prostatectomy with the "cold-punch" method (author's transl)].

Each of 24 patients undergoing transurethral prostatectomy under spinal anaesthesia received 1000 ml HES and, depending from the clinical situation, some patients received blood-transfusion. Afterwards two groups were formed: group A (11 patients), who received HES only, and group B (13 Patients) with additional blood-transfusions. The following parameters were monitored simultaneously: blood pressure, heart rate, stroke index, cardiac output, active blood volume, hemoglobin and hematocrit in whole blood as well as in the irrigatin fluid of the bladder. They showed HES to be a useful plasma substitute for older patients. It is well tolerated and has a slow stabilising effect on circulation, which was effective for several hours. Furthermore, HES-infusion reduced the average need of bloodtransfusion by 500 ml.

Aged↗