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Biomedical subjects

F W Ahnefeld

Publications and source records attributed to F W Ahnefeld.

At least 91 records · Page 5Linked to original sources
PubMed1987

[Comparative humidity measurements in semiclosed and semiopen systems with the additional use of artificial noses].

The administration of dry anesthetic gases for ventilation lasting more than 1 h leads to morphological changes of the tracheobronchial epithelium that may cause postoperative pulmonary complications. Therefore, additional humidification is suggested for ventilation during anesthesia, particularly when using semiopen breathing systems. Recommendations concerning the use of semiclosed systems are controversial: previous studies have shown sufficient humidification on the one hand, and insufficient water content in the inspired air on the other hand. In this study, comparative humidity measurements in a semiopen and a semiclosed system were carried out during anesthesia and mechanical ventilation. We particularly wanted to find out whether placement of the fresh gas inlet into the circle before or behind the soda lime canister influences the humidity of the inspired gas. In addition, we tested three types of "heat and moisture exchanges"--Engström "Edith", Siemens "Servo Humidifier", and Portex "Humid Vent". A total of 58 patients between 23 and 78 years of age were studied. They were divided into three groups. Group I: In 10 patients comparative humidity measurements were carried out using both a semiopen and a semiclosed system. Group II: The time course of water saturation during a 3-h period was determined in 10 patients ventilated with a semiopen and 8 patients ventilated with a semiclosed circle system. Group III: In 20 patients we tested the effect of "heat and moisture exchangers". All patients were intubated and ventilated with the Spiromat 656 and the Circle System 8 (Drger) that made ventilation in both a semiclosed and a semiopen system possible. The humidity measurements were carried out using a psychometric method.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1986

[Emergency medicine--first-aid outside of the clinic. Development and status determination].

A survey of actual problems in first-aid-treatment of life threatened patients is given. The life-threatened patient who needs immediate and sufficient treatment on the place of the accident is described and all the necessary steps to accomplish efficiency are listed as well as the necessary training of doctors who will be emergency-doctors in the future. Statistical data on the positive results of a sufficient first aid treatment with special ambulances are shown.

Emergency Medical Service Communication Systems↗
PubMed1986

[Comparative echocardiographic studies on the negative inotropic effect of halothane, enflurane and isoflurane].

Using the afterload-independent end-systolic pressure-dimension-relationship a study was performed in order to investigate whether there are differences in the negative inotropic effects of halothane, enflurane and isoflurane at 1 MAC in 70% N2O. 30 patients of ASA-groups I and II were studied. Using transoesophageal 2d- and m-mode echocardiography the end-systolic-pressure-dimension-relationship was established and the slope (parameter of contractility) determined. The slope decreased significantly (paired Wilcoxon-test 2 alpha less than 0.01) with halothane (68.5/46.5 mmHg/cm), enflurane (56/48 mm Hg/cm) and isoflurane (63/35 mmHg/cm). There is no difference between the three groups (Kruskal-Wallis-test 2 alpha greater than 0.05). The negative inotropic effects of halothane, enflurane and isoflurane at 1 MAC in 70% N2O are the same. The vasodilation caused by isoflurane enables better pump function compared to halothane and enflurane, but may cause severe hypotension. We conclude that for cardiac risk patients isoflurane has no outstanding advantages in comparison to halothane and enflurane.

Adult↗
PubMed1986

[Therapy using blood components. Prerequisites, indications and clinical use].

The therapeutic benefit of blood components for specific substitution and volume replacement has been recognized for more than ten years. The increasing demand for blood and blood products, especially for albumin in connection with an only moderate growth of the base of blood donors has promoted the idea of a more efficient utilization of blood by specific replacement with blood components. The component therapy has reduced the side effects and improved the efficacy of blood transfusion and last but not least has led to a positive cost-effectiveness. Our clinical management of blood transfusion with a nearly complete use of components in surgical patients is presented. Particularly, the therapeutic strategy for massive transfusions by component therapy is discussed. In face of the technical and logistic problems, a transfusion schedule was developed which outlines the nearly exclusive therapeutic use of components. It applies with modifications and adjustment to the critical parameters to all cases of rapid and massive blood loss. In addition, diagnostic and therapeutic strategies are considered to preserve hemostasis or correct occurring hemostatic defects and to prevent thrombo-embolic events.

Blood Coagulation Factors↗
PubMed1986

[Aortofemoral bifurcation bypass. Effect of the anesthesia procedure (NLA, thoracic continuous catheter peridural anesthesia) on circulation, respiration and metabolism. Homeostasis and oxygen transport].

50 patients were investigated during induction of anaesthesia and infrarenal aortic bypass surgery. 26 were operated on under neuroleptanaesthesia (NA group) and 24 under continuous epidural combined with a light general anaesthesia (epidural group). Blood losses were replaced with 5 per cent human albumin, red cell concentrates, and fresh frozen plasma. Ringer lactate solution was used to replace the functional extracellular fluid volume. During induction and maintenance of anaesthesia body temperature fell (NA group from 36.7 to 35.3 degrees C; epidural group from 36.7 to 34.9 degrees C) but no statistically significant difference could be found between the groups, in spite of better surface perfusion of the lower part of the body in the epidural group. The increase of plasma glucose concentration was lower in the epidural group as compared to the NA group. Stress mediated hypokalaemia was of the same degree in both groups, the median values of the plasma potassium concentrations being in the lower reference range (3.5-3.7 mmol X 1(-1], although large amounts of red cell concentrates were given. During clamping of the aorta a moderate compensated acidosis developed in both groups. Declamping caused a more marked increase of paCO2 and a greater fall of pH in the NA group as compared to the epidural group. Induction of anaesthesia was followed by a fall in oxygen uptake (NA group from 221 to 163 ml X min-1; epidural group from 230 to 189 ml X min-1) which appears to be delayed in the epidural group, with a short lasting statistically significant difference between the groups after eventration of the gut (NA group: 162 ml X min-1 less than epidural group 184 ml X min-1). Later on, oxygen uptake was equal in both groups, with no further changes due to clamping or declamping of the aorta. At the end of the operation, when nitrous oxide had been turned of, the oxygen uptake increased considerably in several patients, despite continuing artificial ventilation and intravenous hypnotics and analgesics having been given. Eventration and exterioration of the gut caused the most marked changes in haemodynamics and oxygen transport with significant differences between the groups. Immediately after eventration there was a sudden fall in paO2 in both groups (NA group from 99 to 83 mm Hg; epidural group from 96 to 84 mm Hg) and an increase of the calculated intrapulmonary right-to-left-shunt (NA group from 7 to 21%; epidural group from 10 to 19%).(ABSTRACT TRUNCATED AT 400 WORDS)

Acid-Base Equilibrium↗
PubMed1985

[Sodium bicarbonate administration in cardiopulmonary resuscitation. Results of an animal experimental study].

One minute following electrically induced ventricular fibrillation, 12 anaesthetized pigs (hybrids between German and Belgian pedigree swine of 29 kg average body weight) were resuscitated for 30 min with a mechanical thorax compressor and ventilator. Six animals were given 1 mval sodium bicarbonate per kilogram body weight via a central venous line during the first ten minutes of resuscitation, and then 0.5 mval/kg body weight during both of the remaining ten minute intervals. The remaining 6 animals served as control group. In the control group constant volume ventilation led to a fall in the arterial partial pressure of CO2 because perfusion was diminished in relation to ventilation and despite the slowly developing metabolic acidosis this initially led to an increase in pH. At the end of the period of observation an arterial base deficit of 10 mmol/l was measured. Infusion of sodium bicarbonate led to a metabolic alkalosis and to an arterial base excess which at 10 min reached a maximum value of 13.8 mmol/l. In the bicarbonate group serum osmolality rose as a result of the sodium application from 293-334 mosm/l. In contrast, the osmolality of the control group only rose to 309 mosm/l.

Animals↗
PubMed1985

[Changes in acid-base status, potassium ions and glucose concentrations in blood during cardiopulmonary resuscitation. Study of the significance of animal experiment results in emergency medicine case examples].

Results obtained during animal investigations cannot be directly applied to patients because of the anatomical and physiological differences present. Experience has shown that cases of sudden cardiac arrest can only be effectively helped if cardiac massage and artificial ventilation are carried out as soon as possible, and that no sodium bicarbonate need be given when resuscitation measures are begun immediately, or very soon after arrest. In this situation it is better to use adrenaline only, in order to improve organ perfusion. The examples presented show that giving bicarbonate can alter potassium kinetics. Very low serum potassium concentrations are often measured during and following successful resuscitation, and giving too large an amount of buffer solution can worsen this hypokalaemia and lead to a further arrest. The infusion of sodium bicarbonate and the rapid increase in blood sugar levels during resuscitation can lead to a marked rise in serum osmolality which in turn can jeopardize the return of cerebral function. Because in the presence of reduced cerebral perfusion, high blood glucose levels increase the degree of cerebral lactacidosis blood glucose levels should be measured and corrected as necessary.

Acid-Base Equilibrium↗
PubMed1985

[Aortofemoral bifurcation bypass--effect of the anesthesia procedure (NLA, thoracic continuous catheter peridural anesthesia) on circulation, respiration and metabolism. Intraoperative circulatory reactions].

51 patients who were selected for aorto-bifemoral bypass operation (infrarenal aortic aneurysm, iliac or iliofemoral occlusive disease) were randomized into two groups. 26 patients were operated on under neuroleptanaesthesia and 25 patients had a continuous thoracic epidural, which was supplemented with a light general anaesthesia during the operation. All patients were optimally volume loaded prior to surgery. The most marked haemodynamic alterations (tachycardia, arterial hypertension, increase of cardiac index, left ventricular stroke work index and cardiac minute work) were provoked by eventration of the gut. In the epidural group, these changes were attenuated and in contrast to the neuroleptanaesthesia group, there were a few patients who had a serious fall in blood pressure. These reactions were regularly accompanied by a generalized flush which led to the hypothesis that they were caused by the release of intestinal hormones, reactive peptides and neurotransmitters, from the mechanically irritated gut. Clamping of the aorta was relatively uneventful. Heart rate and cardiac index decreased in both groups but mean arterial pressure and pulmonary capillary wedge pressure remained stable. Systemic vascular resistance increased slightly in the neuroleptanaesthesia, but not in the epidural group. Declamping was followed by significant but transient falls in systemic vascular resistance and arterial pressure in both groups, despite sufficient volume loading before opening the clamp. In the neuroleptanaesthesia group these changes spontaneously returned to normal; in the epidural group 6 patients received vasopressors or positive inotropic drugs. These results indicate the following: Epidural anaesthesia prevents hypertension and tachycardia and lowers cardiac minute work. Eventration of the gut, acute blood losses and declamping of the aorta may be critical situations, which can lead to profound hypotension. Under neuroleptanaesthesia eventration of the gut is followed by tachycardia and hypertension whereas blood losses and declamping are not as critical as when an epidural is used. Only experienced anaesthetists should use epidural anaesthesia for aortic surgery. An intensive monitoring of haemodynamic function during this form of anaesthesia is mandatory.

Adult↗
PubMed1985

[Intracranial pressure during ketamine administration with spontaneous respiration. An animal experimental model].

A sequence of i.v. ketamine injections, 0.5, 2.0, and 5.0 mg/kg body weight, was given to thirty piglets. At the beginning of the investigation, 10 of these animals had a normal intracranial pressure and stable circulation. The intracranial pressure of the remaining 20 piglets was raised to 30 mm Hg, and an additional haemorrhagic shock was induced in 10 of these animals. Those animals with a normal intracranial pressure showed no alteration there of at any of the three doses given, and the arterial pCO2 remained practically unchanged. In contrast, all animals with a raised intracranial pressure, both with and without superimposed haemorrhagic shock, had a significant rise in intracranial pressure and pCO2. These two parameters were found to correlate well with each other. We conclude that in the model used, where the animals were breathing spontaneously, the intracranial pressure rise seen following ketamine application is secondary to the increase in pCO2.

Animals↗
PubMed1985

[Intraoperative monitoring using transesophageal 2-dimensional echocardiography].

Currently used monitoring techniques, such as measurements of blood pressure and heart rate, provide incomplete information about cardiac function during surgery. Invasive monitoring like intraoperative pulmonary artery pressure measurement with flow-directed balloon catheters may be more sensitive to detect cardiac instability, but they are associated with potentially fatal complications such as dysrhythmias and pulmonary artery rupture. In search of a more informative and yet safe intraoperative hemodynamic monitoring system, we have investigated the use of 2-D transoesophageal echocardiography (TEE). So far more than 400 patients were studied by TEE for up to 12 hours during elective surgery without any complications. High quality recordings of the left ventricle (LV) could be obtained in 87% of all patients. On the basis of the results presented below, we believe that TEE holds three fundamental advantages over the existing monitoring systems: it is inherently safer than intravascular measures, it allows direct assessment of LV filing, and it provides direct information on global and regional LV wall motion.

Abdomen↗
PubMed1985

[Transesophageal 2-dimensional echocardiography in hip endoprostheses].

Previous studies indicate that during total hip replacement intraoperative pulmonary embolization of air and medullary bone marrow occurs. This was based on histological examination of lung tissue obtained during animal investigations and postmortem in human tissue. In vivo proof of this embolization has not as yet been found because of the methodological problems involved. Using transoesophageal two-dimensional echocardiography continuously direct imaging of the right atrium and the right ventricle can be carried out and the embolization thus visualized. In a prospective randomized study in 26 patients having to undergo total hip replacement operation the right atrium and right ventricle were continuously scanned. Endexpiratory CO2-partial pressure was simultaneously recorded. A venting hole in the femur is said to prevent the pressure rising in the medullary space and therefore prevents embolization. In 13 patients therefore, a 4.5 mm lateral drill hole 4 cm distal the tip of the prosthesis was made in order to vent the medullary space. Transoesophageal two-dimensional echocardiography revealed air bubbles in 12 of 13 patients in the control group during implantation of the femoral prosthesis. This is significantly different to the group of vented patients where bubbles were only seen in 4 cases (p less than 0.01). Emboli were visible in 8 patients in the control group in contrast to only 2 cases in the vented group (p less than 0.05). The endexpiratory CO2-pressure of the control group fell from 35 mmHg to 33 mm Hg (Median, p less than 0.001). The CO2 of the vented patients remained constant.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗