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Biomedical subjects

E Freye

Publications and source records attributed to E Freye.

89 records · Page 5Linked to original sources
PubMed1979

Perfusion of the fourth cerebral ventricle with fentanyl induces naloxone-reversible bradycardia, hypotension, and EEG synchronisation in conscious dogs.

Injection of fentanyl into the cisterna magna of the brain leads to hypotension and bradycardia in anesthetised dogs. To determine if this effect is related to the recently discovered opiate receptors fentanyl was perfused in increasing concentrations (2.5-20 microgram/ml) through the cerebro-ventricular system in conscious dogs. Blood pressure was recorded continuously from a punctured exteriorised carotid artery; heart rate was derived from the ECG. Baroreflex activity was tested repeatedly by clamping of both common carotid arteries. Cerebral activity was evaluated from the EEG. Perfusion of the fourth cerebral ventricle resulted in a concentration-related fall in heart rate by 43% and in an inhibition of the reflex response of heart rate to carotid clamping. In contrast, blood pressure fell only moderately by 14% and its reflex response was well maintained. The EEG pattern changed from frequencies in the beta-band (awake control) to gradual synchronisation with delta-activity corresponding to behavioural signs of tranquilisation and sleep-like states. All these effects were reversed by naloxone. No effects were seen when fentanyl was perfused through the lateral ventricles and third ventricle although this yielded similar serum concentration as after perfusion of the fourth ventricle. It is concluded that opiate receptors bordering the fourth cerebral ventricle mediate the cardiovascular and hypnotic action of fentanyl.

Animals↗
PubMed1979

Perfusion of naloxone through the fourth cerebral ventricle reverses the circulatory and hypnotic effects of halothane in dogs.

To determine whether naloxone when perfused through the cerebroventricular system would modify the circulatory and hypnotic effects of halothane, the authors studied its effect in six trained dogs. Naloxone, 20 microgram/ml, was perfused through the fourth cerebral ventricle in three and through the third cerebral and lateral ventricles in three other dogs when awake and during halothane anesthesia (0.75--0.82 vol per cent in oxygen). Blood pressure, heart rate, and circulatory responses to bilateral occlusion of the carotid arteries were measured. The state of consciousness was evaluated by the animals behavior and the EEG. Arterial hypotension, bradycardia, depressed baroreceptor responses, and EEG synchronization associated with halothane anesthesia were reversed when naloxone was perfused through the fourth ventricle. To maintain comparable depths of anesthesia the halothane concentration had to be doubled during naloxone perfusion. No change in the circulatory or hypnotic effects of halothane occurred when the third ventricle was perfused with naloxone. It is concluded that opiate receptors in structures bordering the fourth cerebral ventricle may be important modulators of inhalational anesthesia.

Animals↗
PubMed1978

The action of vitamin B1 (thiamine) on the cardiovascular system of the cat.

Vitamin B1 administered in a high dose (160 mg/kg) parenterally is known to cause neuromuscular and ganglionic blockade. The effects on the cardiovascular system however have not been sufficiently investigated. In artificially ventilated cats under light ethrane-anesthesia, following parameters were measured continuously before and after B1 administration : Left ventricular pressure, left ventricular end-diastolic pressure, LV dP/dt max, electrocardiogram, heart rate, central venous pressure, and peripheral blood pressure (systolic, diastolic, mean). The data indicate a three-phase reaction after B1 injection : Phase 1--shortly after injection there is a drop of all parameters lasting for 30 sec. The LVEDP showed no change while CVP increased. The drop could not be eliminated by the pretreatment with antihistaminiergic or anticholinergic drug. Sequential stimulation with norepinephrine was able to re-establish base-line values. In Phase 2 (two minutes after injection) all parameters return to their control values ; except CVP which stays elevated. Phase 3 (around the 7th minute after injection) shows a gradual decrease of all parameters; CVP returns to control values. It is suggested that phase 1 represents an immediate alpha-blockade, phase 2 reveals a compensatory reflex mechanism, and phase 3 shows full ganglionic blockade.

Animals↗
PubMed1976

Tyrosine hydroxylation in the rat striatum after fentanyl and droperidol in vivo.

The effects of fentanyl, droperidol, and morphine on tyrosine hydroxylation in the rat striatum was measured after inhibition of aromatic amino acid decarboxylase with R04-4602. Any direct change in the product of hydroxylation (i.e.dopa) was supposed to reflect a change in enzyme activity. Fentanyl (0.1 mg/kg intraperitoneally) first (10 min) appears to slightly depress, and later (30 min) significantly activate tyrosine hydroxylation. Morphine (10 mg/kg i.p.) activates tyrosine hydroxylation to a much lesser degree than fentanyl. Droperidol (3 mg/kg i.p.) only slightly activates the in vivo activity of the enzyme.

Animals↗
PubMed1976

Effects of fentanyl and droperidol on the dopamine metabolism of the rat striatum.

Fentanyl in low doses (0.02-0.05 mg/kg) had no significant effect on the dopamine turnover 20 min after intraperitoneal (i.p.) injection and raised the homovanillic acid (HVA) concentration in the rat striatum with a maximum at 60 min after i.p. injection. Higher doses (0.1-0.2 mg/kg)reduced the HVA content after 20 min and raised it after 60 min. Naloxone (1 mg/kg) given shortly (5min) after high doses of fentanyl (0.2 mg/kg) was able to eliminate the early (i.e., 20 min after i.p. injection) decrease and the late (i.e., 60 min after i.p. injection)increase of HVA content in the striatum. Naloxone (1mg/kg) alone slightly increased the HVA concentration, after 20 as well as after 60 min. Droperidol (3-12 mg/kg) and haloperidol (6-12 mg/kg) markedly increased the HVA content in the rat striatum 90 min after i.p. injection. These effects were dose-dependent. Naloxone (1 mg/kg) did not significantly inhibit the rise of HVA induced by droperidol.

Animals↗
PubMed1975

Multivariate data analysis based on a computerized patient monitoring system.

Multivariate time series data in post-operative patients (respiratory and cardiovascular) are compared to reference groups. Using this technique under the program control of a computerized patient monitoring system (IBM 1800) various classes in the respiratory and cardiovascular spectrum can define the co-ordinate system in hyperspace. The patient in crisis is recognised by his deviation from normal rates of change of the variable set, as well as by the time trajectories of recovery in the hyperspace.

Computers↗
PubMed1975

[High doses of fentanyl as the sole anaesthetic agent and naloxone as its antagonist (author's transl)].

In 70 patients (maxillo-facial-, neurosurgical-, abdominal- and gynaecological operations) the technique of "analgetic anaesthesia" using high doses of fentanyl (0.025 mg/kg body weight) and naloxone as its antagonist (0.02 mg/kg body weight) has been employed. All patients were artificially ventilated with N2O/O2 in a 3:1 ratio. Muscle relaxation was achieved with pancuronium-bromide (0.08 mg/kg). The patients had no apparent heart or lung disease. The youngest patient was 4 years of age, the oldest 82 years of age (average age 48.9). The necessity for a reinjection of fentanyl (half the initial dose) was determined by continously monitoring heart rate. This variable appeared to be the most subtle index indicating a reduction in analgesia. Sufficient analgesia was maintained once the heart rate stayed 20% below preanaesthetic levels. At the end of the operation naloxone reversed the respiratory depression. There was no evidence indicating postoperative pain, which may have required administration of additional analgesics. If deep analgesia was maintained up to the last surgical procedures no emesis appeared in the post operative period. The incidence of emesis was higher 10% compared to the classical neuroleptanalgesia with droperidol this was often noted in cases where blood accumulated in the stomach (maxillo-facial operations) (70%). In 3% of all cases psychomotor agitation with delirium appeared right after the injection of naloxone. This lasted for about 15 minutes. We suspect that due to the sudden and powerful effect of naxolone, in replacing fentanyl from its receptor site, acute withdrawal symptoms may be precipitated.

Adolescent↗
PubMed1975

[Computerized patient-monitoring in the O.R (author's transl)].

The routinely performed data-aquisition and its analysis by means of a computerized patient-monitoring-system will reduce the repetitive and often monotonous task of data collection accompanied by accuracy and objectivity as much as possible. Another and equally important point for the anesthesiologists is to remove some of the pencil-and-paper burden, reduce the possibilities of human errors in reading instruments and note-taking and the rapid retrieval of monitored and stored data for the purpose of trend analysis. In detail this paper deals with two major systems (department of anesthesia, Latter-Day-Saints Hospital, Salt-Lake City, Utah, and the department of anesthesia, Center of System Research, Stanford University, Palo Alto, Calif., U.S.A.) where the computer is used to extend present monitoring capabilities and frees the staff of those tasks which can be done more efficiently by a machine. It is shown that the more experienced the computer center and the less complex the programming will be, the more liable the anesthesiologist trapped in the routine work will profit from this device. The System in Salt-Lake City proved to be a reliable tool while the system in Stanford so far has shown only to be valid in the remote surveillance of nurse anesthetists in the OR.

Anesthesia↗
PubMedDate not supplied

Cardiovascular effects of high doses of thiamine (vit B1) in the dog with special reference to myocardial oxygen consumption.

The purpose of this study was to determine the reactions of the cardiovascular system with special reference to myocardial oxygen consumption (MVO2) after the administration of graded doses (up to 2.4 g/kg) of thiamine. The data obtained indicate that thiamine: 1. Decreases mean peripheral pressure up to 25%. 2. Decreases LVEDP, left ventricular pressure, and LV dP/dtmax up to 10%, 15%, and 20% respectively. 3. Reduces pulse rate up to 25%. 4. Reduces coronary sinus blood flow up to 31%. 5. Reduces myocardial oxygen consumption up to 45%. The reduction in LVEDP, LVP, and LV dP/dtmax could be antagonized by dextran or norepinephrine infusion. It is suggested that thiamine blocks alpha-receptors which leads to pooling of blood with a concomitant reduction in pre- and afterload of the heart. The effect on MVO2 suggests that thiamine, the essential coenzyme for the formation of high energy substrates reduced the metabolic needs of the heart. The drug warrants further investigation for the treatment of myocardial ischemia.

Animals↗
PubMedDate not supplied

Somatosensory-evoked potentials (SEPs) are affected differently by mu- and kappa-selective opioids in the dog.

Alfentanil, a mu-opioid receptor ligand, induced a dose-related suppression of the early N50 peak and an increase in latency of the late N140 peak. The highest dose blocked all potentials. These effects were reversible by naloxone. The kappa-ligand bremazocine, induced a dose-related increase in latency of the late P150 peak which was, however, reversed by the specific kappa-antagonist Mr2266, not by naloxone. Continuous blockade of the mu-receptor with low-dose naloxone topped with cumulative doses of nalbuphine, a mixed narcotic analgesic, resulted in a Mr 2266-reversible increase in latency of the late N100 peak. Influences of the opioids on the SEP may account for their difference in clinical effects.

Alfentanil↗