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Biomedical subjects

K Wiedemann

Publications and source records attributed to K Wiedemann.

At least 127 records · Page 7Linked to original sources
PubMed1980

Dihydroergotamine--stimulation of intestinal peristalsis. An experimental and clinical study.

In an experimental study in 15 beagle hounds using strain gauges a significantly increased motility in the small and large intestine after dihydroergotamine was observed. Since this assessment did not provide any information about mucus transport, gastro-intestinal passage time in patient and control groups was determined using radioopaque catheter material. While transit time in the patient group was significantly reduced by 2 x 0.5 mg DHE s.c./day, this effect was not observed in controls. We related the significantly reduced passage time after DHE in the patient group to a normalisation of a functional disturbance of regulation. The action of the drug is seen in the blocking of the stress induced increased sympathetic tone, without the side effects often seen after pure alpha-antagonists of the phentolamine type or the adrenergic guanethidine type neuronal blocking agents. The specific efficacy of DHE as a partial alpha-antagonist is pointed out. For the clinician, postoperative gastro-intestinal atony might be an indication for its use.

Animals↗
PubMed1980

[Barbiturate infusion in severe brain trauma (preliminary report) (author's transl)].

The pathophysiology of brain trauma regarding disturbances of energy and transmitter metabolism, development of intra- and extracellular cerebral oedema are briefly outlined. Possible mechanisms of action of barbiturates in amelioration of cerebral ischaemia, decrease of cerebral metabolism, preservation of membrane stability, reduction of cerebral oedema and intracranial pressure are reviewed. We report on 6 patients with severe brain trauma due to head injury whose intracranial pressure despite conventional treatment with hyperventilation, steroids and osmotic diuresis remained above 25 mm Hg. They were infused with thiopentone 6--12 mg/kg x h for 6 to 15 days, to reduce cerebral electrical activity to the point of "burst suppression" in the electroencephalogram. Three patients survived, two of them regaining their previous good health. The results in these patients are discussed as regards thiopentone dosage and severity of trauma. Marked cardiovascular instability in one case and cholostatic jaundice due to barbiturate administration in two cases were the most important side effects. Barbiturate infusion seems to be indicated in brain trauma with sustained elevation of intracranial pressure above 25 mm Hg despite vigorous conventional therapy. Monitoring most essential to this aggressive treatment scheme comprises measurement of intracranial pressure and continuous observation of the EEG.

Adult↗
PubMed1979

[Influence of combined moderate arterial hypoxaemia and moderate hypovolaemic hypotension on cerebral blood flow and cerebral oxidative and energy metabolism in the dog (author's transl)].

The influence on total cerebral blood flow, cerebral metabolic rates for oxygen, carbon dioxide, glucose, lactate and pyruvate and on cerebral grey matter content of glucose, lactate and pyruvate and high energy phosphate compounds of combined moderate reduction in cerebral perfusion pressure (CPP) and moderate arterial hypoxaemia was studied. Individually arterial hypoxaemia and arterial hypotension of the same degree would neither impair autoregulation of cerebral blood flow nor cerebral oxygen availability. Four groups of 10 dogs each were studied under control conditions (group I), with reduction of CPP to 70 mm Hg (group II), with reduction of paO2 to 45 mm Hg (group III) or with a combination of these degrees of hypotension and hypoxaemia (group IV) after steady states of 30 min duration. Cbf was elevated by 40% in group III (p less than or equal to 0.01), CMRO2 was reduced significantly in group IV (p less than or equal to 0.01, CMR lactate was raised significantly in all three experimental groups (p less than or equal to 0.01). All other data were not significantly different from values in control animals. Cerebral tissue lactate content was elevated significantly in groups II to IV as compared to controls (less than or equal to 0.05); changes in cerebral tissue content of glucose and energy rich phosphate compounds were not statistically significant. From the seemingly normal cerebral blood flow in hypotensive-hypoxaemic dogs it is concluded that autoregulation of cerebral blood flow has become ineffective because of vasodilatation consequent upon arterial hypoxaemia. Reduction of CMRO2 in this group points to metabolic insufficiency and to relative cerebral hypoperfusion, but since changes in cerebral content of high energy phosphate compounds were not significant, severe tissue hypoxia may be excluded. The increase in cerebral tissue lactate content is attributable to increased glycolytic activity known from hypotensive and hypoxaemic states. The present investigation suggests that in patients with hypoxaemia and hypotension, brain function may be endangered by a similarly marked change of circulatory and metabolic parameters.

Animals↗
PubMed1978

Cerebral glucose and energy metabolism, cerebral oxygen consumption, and blood flow in arterial hypoxaemia.

The influence of moderately reduced arterial oxygen tension (aPO2 of about 45 Torr) on the metabolism and the blood flow of the brain was tested in 20 anaesthetized, artificially ventilated normotensive, normocapnic beagle dogs. It is demonstrated that the decrease in systemic oxygen delivery to the brain is countered by an appropriate increase in flow (CBF being 60.3 ml/100 g min at normoxia and 84.5 mg/100 g min in hypoxaemia) which maintained the cerebral oxygen consumption unchanged (CMRO2 3.80 versus 3.32 ml/100 g min). The cortical tissue content of energy-rich phosphates such as ATP, ADP, AMP, and phosphocreatine was also found to be unaltered. Neuropathological examinations excluded any hypoxic cell damage. This reactive vasodilatory reaction of the cerebral vessels is apparently a sensitive regulatory process which protects the brain against marked oxygen lack. However, a normal carbohydrate metabolism is not restored by this cerebrovascular mechanism. For, significantly increased CMRlactate (0.32 versus 1.46 ml/100 g min) indicated raised cerebral glycolysis, and the tissue metabolites of glucose suggested an increased glycolytic flux in the brain. It is concluded that in moderate arterial hypoxaemia, which is not uncommon in clinical practice, cerebral blood flow plays an effective homeostatic role in preventing a disturbance of the energy metabolism of the brain.

Adenine Nucleotides↗
PubMed1978

[Air embolism; a complication during neurosurgery in the sitting position (author's transl)].

Neurosurgery in the sitting position not only puts a strain on the cardiopulmonary system, but also carries the risk of venous air embolism. Special monitoring procedures as well as prophylactic measures greatly contribute towards the safety of the patient. The pathogenesis, pathophysiology and the symptoms of venous air embolism are reviewed, and various monitoring methods are discussed, with special reference to their reliability, sensitivity and practicability. The analysis shows that the Doppler ultrasound method, continuous capnography during the duration of the operation, intra-arterial measurement of blood pressure, recording of the central venous pressure and of electrocardiographic changes are essential means of routine monitoring. Suspected air embolism must be promptly dealt with not only by ligation of the severed vein but also by attempts at aspiration of the air bubbles via the atrial catheter. The latter, therefore, plays an important role both as a diagnostic parameter and a therapeutic agent. Although the suggested prophylactic measures do not absolutely protect against complications they will markedly reduce the incidence of venous air embolism.

Blood Pressure↗
PubMed1977

Influence of systemic and cerebral vascular factors on the cerebrospinal fluid pulse waves.

In anesthetized, artificially ventilated dogs, the intracranial cerebrospinal fluid (CSF) pulse waves were studied simultaneously with the central aortic pressure, central venous pressure (CVP), and the sagital sinus pressure under physiological conditions and in normovolemic arterial hypotension and hypertension, in acute cardiac insufficiency of the right atrium, in raised intracranial pressure (ICP), and in arterial hypoxemia. The physiological CSF pulsations are shown to be mainly arterial in origin. In the diastolic phase, the descending part of the pulse curve can be modified by venous superpositions coinciding with the right atrial "A" wave. With increase of ICP the configuration of the CSF pulsations changes: the venous superpositions disappear and the waves become more and more arterial in shape. Furthermore, the pulse amplitude increases considerably. The same change can be observed when cerebral vessels are dilated by arterial hypoxemia. During cardiac insufficiency and consecutive increase of CVP, the CSF pulse curve is venous in shape and the right atrial "A" wabe predominates. In arterial hypotension, CSF pressure decreased. Conversely, in angiotensin-induced systemic arterial hypertension, CSF pressure and its pulse amplitude increased. It is concluded that both systemic arterial blood pressure and cerebrovascular reactivity are major determinants for the shape and the pressure amplitude of the intracranial CSF pulse waves. In the presence of cerebral vasodilatation, systemic arterial blood pressure may be an important factor in raising ICP and altering the brain tissue compliance, because cerebral vascular damping of the arterial pulse is diminished and the arterial pressure head may be directly transmitted to the cerebral capillary bed.

Animals↗
PubMed1977

[Infusion therapy in cardio-pulmonary insufficiency (author's transl)].

The pathogenesis of cardiopulmonary insufficiency in intensive-care patients is reviewed, with special reference to the development of interstitial pulmonary oedema. Measures designed to control the condition and compensate for the increased post-operative and post-traumatic calorie and aminoacid requirements are: 1. restricted fluid intake; 2. digitalization and administration of diuretics; 3. administration of highly concentrated human albumin. Potential pulmonary reactions to, and possible beneficial effects of, parenteral fat administration are discussed.

Angiotensin II↗
PubMed1976

[Risks attendant on the use of electrical equipment in anaesthesia and intensive care units].

The physical principles of electricity and types of electrical injuries are reviewed. The extent of such injuries depends on the strength of the current: ventricular fibrillations can be induced by a current of 10mA, and even of 10 muA if the current passes directly through the heart. The extent of electrothermal injuries depends on the duration of the current flow and the contact area. Indirect electrical injuries may arise from interferance with cardiac pacemakers or monitoring equipment. Risks attendant on the use of even the "safest" electrical apparatus are discussed, with special reference to the risks arising from interaction between, e.g., high frequency diathermy and monitoring equipment or domestic appliances (beside lamp, razor) and monitoring or electrical therapeutic equipment. A number of safety measures to minimize the risk of electrical injuries are discussed.

Anesthesiology↗
PubMed1976

[Pre-operative and post-operative parenteral feeding in infancy (author's transl)].

The fluid, electrolyte and caloric requirements and the necessary intake of protein-building elements are reviewed with special reference to parenteral feeding before, during and after surgical operations. During the pre-operative stage the replacement of lost body fluid arising from gastro-intestinal disturbances in infancy is of major importance. Adequate quantities of electrolytes must also be added to the replacement fluid during the operation; sodium depletion is usually counteracted by administration of bicarbonate buffers. Methods for restoring the blood volume to normal and for approximately estimating the required quantities are described. During the post-operative period, which is characterized by the so-called post-aggression metabolism with increased ergotropy, the caloric requirements are particularly high while glucose utilization is apt to be disturbed. A plan for meeting the caloric requirements under various post-operative conditions is outlined.

Adult↗
PubMed1976

[Toxicity of sodium nitroprusside (author's transl)].

The mode of breakdown of sodium nitroprusside (NPN) is described and the fact is pointed out that cyanide is formed during the process. The main mode of detoxication leads to the production of thiocyanate. Potential effects of cyanide formation are: blocking of cytochrome oxidase and carbonic anhydrase and cyanmethaemoglobin. The clinical features of NPN poisoning are reviewed. The importance of preventing NPN poisoning by strictly adhering to the maximun doses (1.5mg/kg bodyweight) is emphasized. Anti-dose are; injections of hydroxycobalamin (22.4 mg/mg NPN) and sodium thiosulfate (5.0 mg/mg NPN). The use of drugs to induce methaemoglobin formation is now obsolete. As only very few cases of NPN poisoning have so far been reported; there is no need to discontinue the use of this drug, provided the maximun dosis is not exceeded and the patient is under strict surveillance.

Acidosis↗