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Biomedical subjects

J Radke

Publications and source records attributed to J Radke.

At least 19 recordsLinked to original sources
PubMed1992

The influence of isoflurane on peri-operative endocrine and metabolic stress responses.

Trauma and surgery profoundly affect the circulating concentrations of metabolites and so-called stress hormones, and may thereby directly or indirectly influence recovery. This stress response on the other hand is subject to modification by the anaesthetics employed. We investigated the effects of isoflurane on selected stress parameters in 10 patients undergoing major abdominal surgery and compared them to those in 10 patients receiving halothane. Plasma levels of adrenaline, noradrenaline, cortisol, ACTH, and beta-endorphin, as well as glucose, non-esterified fatty acids (NEFA), and lactate were determined during a pre-operative anaesthesia period as well as intra- and post-operatively. The levels of all parameters remained stable or decreased during the pre-operative anaesthesia period. They increased intra- and/or post-operatively, reaching peak values in the recovery period. Although the changes in both groups were basically similar, we observed lower serum concentrations of cortisol and lactate in the isoflurane group. We conclude that isoflurane and halothane have similar effects on peri-operative changes of endocrine and metabolic parameters, and that neither can effectively block the stress response to major surgery. We found no firm evidence for a stimulatory effect of isoflurane on the parameters studied.

Adrenocorticotropic Hormone↗
PubMed1992

[Analgesia and sedation in intensive care patients].

Analgesia and sedation with the associated reduction of undesired vegetative reactions are important components in the therapeutic regimen of intensive care patients. None of the sedative drugs available can fulfil every one of the criteria expected of an "ideal" sedative. Four commonly used drug combinations have been established as standards: 1. opioid and neuroleptic, 2. opioid and benzodiazepine, 3. ketamine and benzodiazepine, and 4. opioid and propofol. In everyday use one must take not only the specific side-effects of a drug into consideration but also its pharmacokinetic properties. These are often markedly altered in critically ill patients who have impaired functions of vital organs. The pharmacokinetics of a drug is affected by disturbed renal or hepatic function, interactions with other drugs, altered protein binding and the induction or inhibition of metabolic enzymes. The best method of drug administration is by motor-driven pump, with which large fluctuations of the dosage can be avoided. Constant ratios of drug combinations are not recommended, since the pharmacokinetics of each drug is affected to a different degree in the critically ill patient. Withdrawal symptoms, can occur for example after prolonged administration of benzodiazepines, can often be avoided by slowly reducing the dose or by switching to a short-acting substance. In some patients (e.g. those with a history of alcohol abuse) a massive increase of the drug dose is not indicated when the effect is not adequate. Instead, an entirely different substance should be employed and the administration of less frequently used drugs should be considered. Despite detailed knowledge of the altered pharmacokinetics in critically ill patients, the drugs should be dosed as dictated by the situation, true to the anaesthesiologists' adage: "Dosage according to effect!"

Analgesics↗
PubMed1992

[Endotracheal suctioning using a 24-hour continuous system. Can costs and waste products be reduced?].

Suctioning of the airways is often required in critically ill, intubated, or tracheotomised patients. In addition to the primary cost of these disposable materials, expenditures for waste disposal and environmental problems due to plastics should also be considered. In this study, the primary costs and amount of waste products of the closed suction system "Trach Care" were compared with a conventional disposable system. Other advantages and disadvantages of a closed suction system are discussed. METHODS. In this prospective, randomised investigation, both the open disposable suction system and the closed Trach Care system were used, in 60 patients (30 in each group) who were intubated for 1 week or more. During the first 7 days, we counted the number of times endotracheal suctioning was performed and measured the time it took. The costs of purchasing the systems, amounts of waste products, and costs of disposal were compared. RESULTS. The frequency of endotracheal suctioning was quite different from patient to patient and varied from 6 to 41 times per day. On average it was necessary 15 times per day per patient in both groups. Using the disposable system, a mean time of 3.5 min was measured in contrast to 2.5 min with the closed system. The costs of purchase were much lower with the disposable system taking into account all materials needed (17.36 DM vs 53.36 DM per day), whereas the weight of litter produced by the closed system was lower (429 g vs 745 g per day), the costs of disposal being accordingly different. During endotracheal suctioning O2 desaturation was not observed with the closed system, whereas in patients with acute respiratory failure O2 saturation fell rapidly from 90% to as far as 70% when a disposable system was used. CONCLUSION. The closed Trach Care suction system is more expensive to acquire, but may reduce the risk of exogenous nosocomial pneumonias as disconnections from the ventilator are minimised. The workload, weight of waste products, and costs of disposal are lower using the Trach Care system. From the physician's viewpoint, the main advantage of the Trach Care system becomes evident in patients with acute respiratory failure and patients with elevated intracranial pressure. In these cases, we now favor the Trach Care system as a matter of principle.

Anesthesiology↗
PubMed1991

[Gas embolism with cardiac arrest during hysteroscopy. A case report on 3 patients].

Hysteroscopy and laparoscopy are relatively non-invasive methods routinely employed in the investigation of infertility. The danger of air embolism during these procedures was recognized early, and carbon dioxide was substituted for air since it is more readily soluble in blood. In this report we describe 3 cases of circulatory collapse and cardiac arrest in healthy young women during routine hysteroscopy (out of a total of 62 patients during the period 1989-1990) which were most probably caused by massive carbon dioxide embolism. Premedication was with oral diazepam 10 mg. Anesthesia was induced with 0.1 mg fentanyl, 2.5 mg droperidol and 100 mg methohexital (100 mg propofol in one case). Intubation was facilitated with 2 mg pancuronium and 50-100mg succinylcholine. Anesthesia was maintained with nitrous oxide 66% and halothane. Ventilation was controlled with a tidal volume of 10 ml per kilogram body weight at a rate of 10 per minute. Monitoring included ECG, automated non-invasive blood pressure, capnometry, pulse oximetry and body temperature. Anesthesia was uneventful prior to insufflation. In each case the signs and symptoms began approximately 5-8 minutes after the start of insufflation and consisted of an initial tachycardia rapidly followed by ventricular dysrhythmias, bradycardia and cardiac arrest. The end-tidal CO2 decreased during the tachycardic phase and prior to asystole. The patients were cyanotic with engorged jugular veins. Resuscitation with closed chest heart massage and intravenous epinephrine or orciprenaline was successful in every case. The typical "mill wheel phenomenon" of gas embolism was audible on auscultation after heart activity had returned, but disappeared after about 5 minutes.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Haemodynamic and endocrine effects of deliberate hypotension with magnesium sulphate for cerebral-aneurysm surgery.

Deliberate hypotension is widely used during cerebral-artery aneurysm surgery to facilitate clipping and to prevent rupture. A large number of drugs are commonly employed to achieve hypotension, but all have their specific drawbacks. We investigated the effects of magnesium-sulphate-induced hypotension on haemodynamics, as well as on plasma catecholamine and renin concentrations in 11 patients undergoing cerebral-aneurysm surgery. Magnesium sulphate lowered blood pressure by reducing systemic vascular resistance. There was no reflex tachycardia or rebound hypertension, and cardiac output was not decreased. Plasma renin activity increased during hypotension but the inhibitory effects of magnesium on angiotensin converting enzyme prevented angiotensin-II-associated hypertension. Plasma catecholamine concentrations increased moderately during hypotension. Renal perfusion was not impaired since diuresis remained constant or even improved during and after hypotension. Magnesium sulphate in high doses has major drawbacks, however, among which are enhanced neuromuscular blockade and delayed return of consciousness. Although the haemodynamic effects of magnesium sulphate during hypotension appear to be beneficial, these side-effects might limits its usefulness, particularly in neurosurgery. More research must be conducted before magnesium sulphate can be considered a routine method.

Adult↗
PubMed1991

[The ozone layer and its modification by N2O and inhalation anesthetics].

As a result of human activities the ozone layer in the stratosphere, which is necessary for life on earth, has changed. The main causes of ozone destruction are chlorofluorcarbons (CFCs) 11 and 12. Recently, caring anesthetists have wondered if and to what degree N2O and popular potent inhalation anesthetics may also contribute to ozone loss. Having consulted the literature, we attempt to answer that question. The ozone-destroying N2O is chiefly produced by burning fossil elements and nitrogenous fertilizing used in agriculture; the share of medically used N2O lies below 2%. Halothane, enflurane, and isoflurane are halogenated anesthetics that contain ozone-destroying halogens (bromine, chlorine, fluorine) to different extents. Complicated experimental calculations for these volatile anesthetics result in a potential for ozone destruction of 0.36 for halothane and 0.02 for enflurane and isoflurane if the potential for ozone destruction by CFCs is set at 1.0. The lifespan of the inhalation anesthetics in the troposphere is with less than 3 years, dramatically less than that of CFCs (70-140 years). The two most important CFCs, 11 and 12, are considered to be currently produced in a quantity of about 800,000 tons per year. On the other hand, the worldwide production of inhalation anesthetics is said to be only 2,000 tons. In view of the experimental calculations and the low worldwide production, the small greenhouse effect, the shorter lifespan in the troposphere, and the low potential for ozone destruction, the negative effects of medically used N2O and inhalation anesthetics on the ozone layer seem negligible. All in all, the inhalation anesthetics are considered to be responsible for only 0.0005% of the ozone destruction at present.

Air Pollutants↗
PubMed1991

[Deterioration of pulmonary gas exchange caused by PEEP in a pulmonary vascular shunt (Rendu-Osler-Weber syndrome)].

A 25-year-old patient with headache was admitted to the neurology department. Computerized tomography revealed an intracerebral abscess of unknown origin, which was removed by craniotomy. After an uneventful operation and anesthetic low arterial oxygen tensions were noted that did not respond to increased FiO2. Angiography revealed a pulmonary arteriovenous (a-v) fistula (angioma), which was responsible for the right-left shunt. A Swan-Ganz catheter was inserted and the effects of varying levels of PEEP on the magnitude of the shunt during spontaneous breathing of 100% oxygen were determined. At zero PEEP the arterial pO2 was 211 mm Hg (AaDO2 470 mm Hg). 5 mbar PEEP caused the arterial pO2 to fall to 118 mm Hg (AaDO2 563 mm Hg). Increasing PEEP to 15 mbar caused a further decrease in arterial pO2 to 72 mm Hg (AaDO2 603 mm Hg), which resulted in arterial desaturation. The arterial pCO2 remained constant. At a virtually constant cardiac output the shunt volume increased from 23% at zero PEEP to 30% at a PEEP of 15 mbar--a relative increase of 30%. Elevating the intrathoracic pressure presumably caused redistribution of the pulmonary perfusion toward the shunt vessels, probably because the vascular resistance increased more rapidly in the normal vasculature than in the angioma. The therapeutic consequences were to reduce the PEEP and avoid mechanical ventilation. Pulmonary a-v-fistulas are not uncommonly associated with brain abscesses, probably because the normal filter function of the pulmonary vascular bed is disrupted. Therapy consists either in resecting the afflicted lung segment or in transvenous occlusion of the fistula with a silicon ballon.

Adult↗
PubMed1990

[Control of the placement of a central venous catheter using Doppler ultrasound].

Precise placement of central venous catheters is necessary to prevent complications and assure proper functioning. Chest X-ray is the current standard method of locating the catheter tip. This is usually not feasible in the operating room setting, particularly after the induction of anesthesia. Intravascular ECG registration using the catheter as a lead and identification of intra-atrial P-waves has been suggested as an alternative. In the present study we evaluated the use of Doppler sonography as a noninvasive method of locating the catheter tip and detecting faulty placement. Two hundred patients scheduled for insertion of a central venous catheter took part in this study. The catheters were inserted via standard routes (internal or external jugular vein, basilar or cephalic vein). A Doppler sonographic device with a 2 mHz probe was used (Parke Electronics 915L). The probe was applied to the right sternal border and affixed at the position where the characteristic venous flow sound was most distinct. The signals were displayed visually, subjected to spectral analysis, and also recorded for later evaluation. A rapid injection of 2-5 ml isotonic saline causes turbulences which can readily be heard and recognized without special training. The position of every catheter was later confirmed by radiography, and in 159 patients the intraatrial ECG method was subjected to direct comparison with the sonographic method. The turbulences due to the injected fluid were found to cause an increased amplitude at frequencies above 350 Hz. If the catheter tip was positioned correctly there was no discernable time lag between the start of the injection and perception of turbulences.(ABSTRACT TRUNCATED AT 250 WORDS)

Catheterization, Central Venous↗
PubMed1989

[Hemodynamic effects of the benzodiazepine antagonist flumazenil following laparotomy under total intravenous anesthesia using midazolam].

Inhalational anesthetic agents, particularly nitrous oxide, are potentially hazardous to both the patient and operating room personnel. Recent efforts have been directed towards the development of intravenous anesthetic techniques using combinations of a hypnotic with an analgesic. The hypnotic used in such a combination should have a short elimination half-life, little or no influence on hemodynamics, and no side effects. Benzodiazepines are likely candidates for total intravenous anesthesia (TIVA) since they combine hemodynamic stability and paucity of unwanted effects with the ability to induce amnesia for the entire perioperative period. They do have long elimination half-lives; even midazolam, the shortest-acting benzodiazepine, has a half-life of 2 to 3 h. This disadvantage might be counteracted by the use of flumazenil, the recently introduced, specifically acting benzodiazepine antagonist. The aim of this study was to determine the effects of rapid awakening following flumazenil after major abdominal surgery with benzodiazepine-fentanyl TIVA. Six patients (4 male, 2 female) scheduled for elective laparotomies participated in this pilot study. The average duration of surgery was 2.2 +/- 0.9 h. The patients were given 2 mg flunitrazepam p.o. the evening before surgery and 1 h before being brought to the operating room. Baseline pre-induction values were obtained 15 min after inserting catheters and attaching the EEG electrodes. Fentanyl (0.005 mg/kg) was given as a bolus injection followed by a rapid midazolam infusion. The infusion rate was calculated using the method of Wagner et. al. from the data of Lauven et al. to give plasma concentrations of 500 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[A case of bronchospasm under isoflurane anesthesia].

Isoflurane is generally considered to have little effect on bronchomotor tone. The following case report shows that isoflurane anesthesia can be associated with severe bronchospasm. A 9-year-old girl (35 kg, 140 cm) with no history of asthma or drug sensitivity was scheduled for emergency appendectomy. Anesthesia was induced with fentanyl, methohexital, and vecuronium. Breath sounds were normal prior to induction and after endotracheal intubation. Isoflurane was added to the gas mixture 5 min after the last injection. Almost immediately after isoflurane was added the mean inspiratory pressure increased from 15 to ca. 35 cm H2O, expiration was prolonged, and wheezing was heard on auscultation. End-expiratory CO2 increased from 5.1% to more than 8% (pCO2 ca. 60 mmHg). Halothane was substituted for isoflurane and theophylline was injected, i.v. shortly after which the inspiratory pressure decreased, the wheezing improved, and the end-expiratory CO2 returned to normal. The remaining course and postoperative period were uneventful. Isoflurane is considered to be the causative agent in this case. Other possible mechanisms are discussed and pertinent literature is reviewed.

Anesthesia↗
PubMed1979

Myocardial metabolism and oxygenation in man awake and during halothane anesthesia.

Cardiac catheters were placed in seven healthy conscious patients so that aortic and left ventricular pressures (and the derivative), cardiac output (thermodilution) and myocardial blood flow (argon washin) could be measured. Blood was drawn for measurement of arterial blood-gas and arterial and coronary venous oxygen, glucose, lactate, pyruvate and fatty acid values. After induction of anesthesia by inhalation of halothane, the measurements were made during administration of low (0.70%) and high (1.54%) end-tidal halothane concentrations. Myocardial function decreased in a dose-related fashion without a change in heart rate. Myocardial blood flow and oxygen consumption were depressed in a similar manner. Myocardial oxygen extraction decreased and lactate did not change, suggesting that myocardial oxygenation was adequate. The heart rate-systolic blood pressure product correlated poorly with myocardial oxygen consumption. Systolic blood and the contractile performance index dP/dt/IP were better correlated with myocardial oxygen consumption, but the value of the coefficient was still low. Without significant changes in heart rate, systolic blood pressure is the best correlate of myocardial oxygen consumption in healthy man during the myocardial depression produced by halothane.

Adult↗
PubMed1979

[The effects of halothane-, nitroprusside- and trimethaphan-induced hypotension on cerebral blood flow and intracranial pressure (author's transl)].

Arterial hypotension to about 50 mm Hg mean pressure was induced in anaesthetized and artificially ventilated dogs by halothane, nitroprusside, and trimethaphan to study their effects on cerebral blood flow and intracranial pressure during hypotension. During nitroprusside induced hypotension there was a 32% increase in cerebral blood flow above control and a marked decrease in cerebral arteriovenous oxygen content difference indicating luxury perfusion of the brain. Cerebral blood flow remained high even 30 min after termination of hypotension. During halothane and trimethaphan hypotension cerebral blood flow remained unchanged. In all groups epidural pressure did not change substantially during hypotension but increased during recovery from nitroprusside hypotension by a maximum of 72% above control. It is concluded that during and after nitroprusside hypotension loss of cerebral autoregulation occurs which may result in a marked rise in intracranial pressure. Special vulnerability seems to exist shortly after termination of induced hypotension when arterial pressure begins to rise and brain perfusion follows a pressure-flow relationship.

Animals↗
PubMed1978

[Effects of isovolaemic haemodilution on pulmonary gas exchange and haemodynamics (author's transl)].

In experiments on 11 closed chest dogs the behaviour of pulmonary gas exchange and haemodynamics during isovolaemic haemodilution with 6% dextran was studied. The dogs were ventilated artificially (IPPB, PEEP = 0) with room air. After haemodilution a slight increase of arterial PO2 from 86 to 92 mm Hg was found. In another series of experiments an inspiratory O2-concentration of 25% was applied resulting in an increase of arterial PO2 from 106 to 113 mm Hg. In both series a decrease of alveolararterial PO2 gradients was observed. Effective pulmonary capillary blood flow varied in accordance with changes of cardiac output. Thus intrapulmonary shunt is supposed to have remained constant. The changes of pulmonary O2 diffusing capacity could be explained by the effect of haemodilution per se. At the end of the experiments ventilation was changed by adding a positive endexpiratory pressure of 8 cm H2O resulting in a decrease of arterial PO2 and a steep fall of cardiac output. In conclusion, isovolaemic haemodilution leads to only negligible variations of pulmonary gas exchange which should not be of any clinical importance.

Animals↗
PubMed1977

[A new volumetric infusion pump (author's transl)].

Our experience with a new volumetric infusion pump "Tekmar T 92" is reported. Over a period of months the reported advantages of the instrument were investigated on three separate units. Some few disadvantages for routine use were observed.

Air↗
PubMed1977

[Pulmonary gas exchange during isovolaemic haemodilution (author's transl)].

In experiments on 6 closed chest dogs the behaviour of pulmonary gas exchange during isovolaemic haemodilution with 6% dextran was studied. The dogs were ventilated artificially using an inspiratory gas mixture containing 25% O2. A slight increase of arterial Po2 values was found. This change was accompanied by a decrease in alveolar-arterial Po2 and Pco2 gradients. The size of effective pulmonary capillary blood flow varied in accordance with the size of cardiac output. The changes of pulmonary O2 diffusing capacity could be explained by the effect of haemodilution per se.

Animals↗
PubMed1975

[Comparison of tolerance to ischemia in human and animal myocardium during various forms of induced cardiac arrest (author's transl)].

In a total of 16 patients the tissue pH was determined on myocardium both during surgery and on isolated samples. Cardiac arrest was induced by hypothermal infusion cardioplegia and external cooling. In the isolated human myocardium section pH values were continuously determined at 15 degrees C. Parallel to these measurements samples were taken for electron microscopic examinations. In this way the pH limit under which the human myocardium cannot be revived could be visualized by additional morphologic examination. These results and those from the intrasurgical measurements with a fixed heart muscle surface probe were compared with each other and with results from animal experiments.

Adenosine Triphosphate↗
PubMed1975

[Anatomy of the lateral malleolar sulcus - a contribution to the causation of displacement of peroneal tendons (author's transl)].

On 100 specimens of the fibula repeatable parameters were developed so as to measure the bony bed of the peroneal tendons and to evaluate the results statistically. The specimens were investigated frontally and in profile. And the sulcus was measured with a special tool. By determining height, width and slope of the walls of the groove absolute values were found which permitted differentiation between the various types of salcus.

Ankle Injuries↗