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Biomedical subjects

W Erdmann

Publications and source records attributed to W Erdmann.

At least 73 records · Page 4Linked to original sources

Informative imaging of multiple parameters for the practice of the anesthesiologist.

The development of informative design principles is necessary to permit logical, informative and understandable computer-aided imaging of the flood of measured parameters the practising anesthesiologist is currently confronted with. The computer-assisted workplace, furthermore, can use the computer to close the loop from sensor to therapy through software directed feed back control mechanisms. The general principles of information design should be based on the rule of three derived from the limited visual integration capacity of the human brain. Thus multiple parameters should be logically grouped in blocks of three strictly distinct from each other in the visual display output. Alarm signalisations have to include two senses: visual and audible and should use the large range of variability that is possible to make them distinct from each other. The operational keyboard should be logically designed with grouping in three parts: 1. a group of buttons for activation of operational screen information that appear with never more than three at the same time; 2. buttons for presetting of wanted parameter values, of alarm limits and for introduction of patient data with adjoint but strictly separated OK-mode necessity to alert that change is being made. 3. a row of buttons separated from the normal operational keyboard area for emergency changes and computer feed back mode bypass, for example. The most illogical, unoverseeable and confusing computeraided workplace can be organized to a fully assisting anesthesia workplace if proper design is applied. The use of a users' manual should be rendered unnecessary even to a computer-naive user. This can be achieved through adequate informative design and operational information flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, Closed-Circuit↗

[Local anesthetics. Side effects and their treatment].

Local anesthetics are increasingly being used, especially in the treatment of pain. This makes it important for the physician to be familiar with possible side effects and their treatment. In this paper the most important complications affecting the CNS, circulatory system and heart, as also allergies, psychological reactions, etc. are discussed.

Anaphylaxis↗

Tissue oxygen tension in the cerebral cortex of the rabbit.

Polarographic techniques were employed to measure oxygen partial pressure using 10 micron glass-protected gold microelectrodes. When inserting the electrode into the cortex, a PO2-profile is produced. The average PO2 was about 9 mm Hg. Nearly all measurements were below 25 mm Hg and measurements above 50 mm Hg were rare. When the FiO2 was increased from 0.3 to 1.0, tissue PO2 increased, then gradually decreased. This is probably due to vasoconstriction of pre-capillary sphincters. Acute hypoxia showed the opposite effect, but the autoregulation does not seem to be so effective. When CO2 was added to the inspiratory gas mixture the PO2 increased and showed little tendency to return to normal values. This increase in PO2 is due to the direct effect of CO2 and H+ on the blood vessels, causing vasodilation, and therefore an increase in blood flow and tissue oxygenation.

Animals↗

Tolerance to N2O-induced alterations in somatosensory evoked potentials.

The effect of nitrous oxide (N2O) on somatosensory evoked potentials from the cortical (CEP) and spinal cord (SCP) regions in response to forepaw stimulation was studied in ketamine-anesthetized and mechanically ventilated rats. The CEP was recorded from the skull over the contralateral somatosensory area; the SCP was recorded from the supraspinous ligament at C57-6 and L1-2 levels of the spine. Rats were exposed to 70% N2O for 5 h, whereupon N2O was withdrawn for 2 h. Thereafter, the rats were re-exposed to N2O for 10 min. The N13-P21 component of the CEP, the slow positive wave (P2) of the segmental SCP, and the heterosegmental positive cord dorsum potential (HSP) were significantly suppressed by N2O, while the large negative (N1) component of the segmental SCP remained unchanged. A partial recovery of the CEP and HSP was observed during the 5 h of N2O anesthesia, while significant recovery of the P2 component of the SCP was not observed. The withdrawal from N2O following 5 h exposure caused an augmentation of the CEP (When compared to the control values). Re-exposure of rats to N2O again caused the suppression of these potentials as in the initial exposure. The results suggest that the phenomenon of tolerance to N2O in terms of evoked potentials develops within 5 h in the brain but not in the spinal cord.

Journal Article↗

Role of dopamine receptors in gastrointestinal motility.

Apomorphine (3.5 and 10 mg/kg, s.c.) and morphine (1.3 and 10 mg/kg, s.c.) produced a dose-dependent decrease in gastrointestinal transit of charcoal dust in rats. The involvement of dopamine in such a constipatory effect was found to be mediated to a greater extent by DA2 than by DA1 receptors, using a specific DA1 antagonist (SCH 23390) and DA2 antagonists (alizapride, domperidone). The decrease in apomorphine (50 micrograms) and dopamine (100 and 200 micrograms)-induced gastrointestinal transit after intracisternal administration was antagonized by haloperidol. These results provide evidence for the involvement of dopamine receptors in the constipatory effects of apomorphine and morphine in rats.

Animals↗

Analgesic effect of tramadol in the rat.

The analgesic effect of tramadol was studied in the rat using tail flick and hot plate tests following intrathecal and subcutaneous administrations. Tramadol had only a short-lasting analgesic effect (20 min) on intrathecal administration which may be due to rapid removal from the subarachnoid space. Its analgesic effects were antagonized by pretreatment with naloxone. It seems that the opiate system may involve in the analgesic effect of tramadol, while the noradrenergic, serotonergic and cholinergic systems may play a modulating role.

Analgesics↗

[Nitrous oxide in anesthesia--present status of the use of nitrous oxide, risks for patients and personnel and treatment of side effects].

Mechanisms of some effects of nitrous oxide have recently been elucidated. Its antinociceptive action depends partly on the involvement of the endorphinergic system. Although vitamin B 12 becomes biologically inactive in the presence of nitrous oxide, this certainly is of no clinical consequence in exposures lasting less than eight hours. Should exposures last over 8 hours, effects of vitamin B 12 inactivation can be compensated for by administration of folinic acid. In contrast, professional exposure to trace levels of nitrous oxide seems not to interfere with human health. Furthermore, closed circle apparatus should be used and operating room air be well scavenged when nitrous oxide is used.

Anesthesia, Inhalation↗

Myocardial oxygen tensions during ischaemia in fluorocarbon diluted pigs.

Previous work by the authors has shown that, following ligation of the left anterior descending coronary artery (LAD), myocardial oxygen tension (PmO2) in expected areas of maximal ischaemia is maintained at the expense of ischaemic border zones of the infarct area. Post-ischaemic haemodilution with the fluorocarbon containing plasma substitute Fluosol-DA 20% (FDA) could significantly improve PmO2 and pre-ischaemic haemodilution can delay myocardial ischaemia. We now present an analysis of the pattern of PmO2 changes to be seen when myocardial ischaemia is induced following prior haemodilution with FDA. Two groups of juvenile Yorkshire pigs were anaesthetised with intraperitoneal thiopentone, intubated and ventilated with halothane, nitrous oxide and oxygen. After placement of cardiovascular monitoring lines, a thoracotomy was performed. The pericardium was opened and 4 steel-protected gold microelectrodes were placed in the terminal supply area of the LAD in such a way that 2 electrodes were in the area of myocardial ischaema to be produced. One group of pigs were bled (20 ml/kg) and the loss was replaced with equal volumes of FDA. The animals were ventilated with halothane and oxygen and the terminal LAD was ligated. Electrode outputs were recorded on a flat bed recorder and analysed. LAD occlusion in the control animals resulted in similar changes in PmO2 to those described above.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Protection against myocardial ischaemia by prior haemodilution with fluorocarbon emulsions.

The possible prophylactic effects of Fluosol-DA 20% (FDA) haemodilution against myocardial hypoxia were studied in two groups of anaesthetized immature pigs. Precalibrated 200-micron diameter oxygen microelectrodes were inserted to the myocardium of the left ventricle. One group of animals was haemodiluted with FDA and both groups received 100% oxygen (plus halothane). The lower one-third of the left anterior descending coronary artery was occluded; this caused no significant cardiovascular changes. Analysis from the microelectrodes in the most hypoxic areas of the myocardium revealed significant decreases in myocardial oxygen tension (PmO2) in the control group 15 min after occlusion in the FDA-diluted group. Analysis of other electrodes suggested greater hyperaemic compensatory response in ischaemic border areas in the FDA-treated group.

Animals↗

Aprotinin reduces hypothermic mortality--an experimental model.

In order to test the postulate that post-hypothermic damage may be caused by protease activation, the effect of the administration of aprotinin on hypothermic mortality was investigated in anaesthetized rabbits. A group of 6 animals received 40.000 KIU aprotinin intravenously prior to the induction of hypothermia by surface cooling and this was followed by a further 35.000 KIU each hour for 5 h. The animals were cooled to 29 degrees C and then rewarmed. A control group received equal volumes of physiological saline. The aprotinin treated animals survived, whereas all the control group died within 7 days, 5 of them within 24 h. The haemodynamic, biochemical and haematological changes in the two groups are reported.

Animals↗