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H Stephan

Publications and source records attributed to H Stephan.

At least 37 records · Page 2Linked to original sources
PubMed1989

Cerebral effects of anaesthesia and hypothermia.

Cerebral blood flow, cerebral oxygen and glucose consumption, and cerebral lactate and pyruvate release were measured; spectral analysis of the EEG was recorded in 10 male patients who had coronary artery bypass surgery. The measurements were taken to evaluate the effects of fentanyl-midazolam anaesthesia during normothermia and during hypothermic nonpulsatile cardiopulmonary bypass at 26 degrees C venous blood temperature, when a temperature-corrected PaCO2-value of 5.3 kPa was maintained. Anaesthesia with fentanyl 7 micrograms/kg and midazolam 200 micrograms/kg as induction doses, followed by infusions of fentanyl 0.15 micrograms/kg/minute and midazolam 3 micrograms/kg/minute, was characterised by a decrease in fast-wave activity and an increase in high-amplitude, slow-wave activity in the EEG. There was also a decrease in cerebral blood flow (38%), oxygen consumption (22%) and glucose consumption (25%), while lactate and pyruvate production remained unchanged. Hypothermia of 26 degrees C venous blood temperature suppressed EEG almost completely and decreased oxygen and glucose consumption by a further 61% and 54%, respectively, with no changes in lactate and pyruvate production while cerebral blood flow increased by 145%. These results show that the effects of fentanyl-midazolam anaesthesia on cerebral metabolism are enhanced during hypothermic cardiopulmonary bypass while the influence of anaesthesia on cerebral blood flow is overshadowed by the practice of a temperature-corrected acid-base management.

Adult↗
PubMed1989

Gyrification in the cerebral cortex of primates.

The degree of cortical folding in primates has been analyzed using a gyrification index (GI). Correlation analyses of the GI with body weight, brain weight and neopallial volume show that the human data fit the general trend of the nonhuman anthropoids. Bigger primate brains exhibit a higher degree of fissurization, but a taxonomic difference that is independent of brain weight between prosimians and anthropoids has also been observed. In these regressions, anthropoids differed from prosimians by having a larger increase in gyrification for every unit increase in body or brain weight or neopallial volume. A stepwise regression also shows a prosimian-anthropoid difference. The best predictor for convolutedness in anthropoids is neocortical volume, while in prosimians it is brain weight. The GI in catarrhines is correlated with total sulcal length but not number of sulci. This result suggests paleontological studies of total sulcal length can give direct information on the evolution of cortical folding in primates.

Animals↗
PubMed1989

Sufentanil does not block sympathetic responses to surgical stimuli in patients having coronary artery revascularization surgery.

The effects of a moderate dose of sufentanil (1 microgram.kg-1 + 0.015 micrograms.kg-1.min-1) plus nitrous oxide (30% O2/70% N2O) anesthesia (group I; n = 8) and of high-dose sufentanil/O2 anesthesia (10 micrograms.kg-1 + 0.15 micrograms.kg-1.min-1) without N2O (group II; n = 8) on cardiovascular dynamics, myocardial blood flow, myocardial oxygen consumption, myocardial lactate balance, and hypoxanthine release were studied in two groups of male patients scheduled for elective coronary artery bypass surgery. All patients were on maintenance doses of calcium channel blockers and nitrates with the last doses of medications given the morning of operation. All patients were premedicated with flunitrazepam (2 mg orally), piritramide (7.5 mg IM) and promethazine (25 mg IM). Measurements were performed before the induction of anesthesia with the patients premedicated but awake; 20 min after induction of anesthesia with sufentanil plus pancuronium 0.1 mg.kg-1 for muscle relaxation before surgery; and during sternotomy and sternal spread. Sufentanil at either dose decreased mean arterial pressure, as well as cardiac and stroke volume index while heart rate remained unchanged. Following the induction myocardial blood flow and myocardial oxygen consumption decreased 23% (79 ml.min-1.100 g-1 to 61 ml.min-1.100 g-1 and 28% (9.2 ml O2.min-1.100 g-1 to 6.6 ml O2.min-1.100 g-1) in group I and 14% (78 ml.min-1.100 g-1 to 67 ml.min-1.100 g-1 and 18% (8.7 ml O2.min-1.100 g-1 to 7.1 ml O2.min-1.100 g-1) in group II. Myocardial ischemia was seen in one patient of group II (patient No. 4), as indicated by a hypoxanthine release into the coronary sinus, when after the induction MAP decreased from 93 to 67 mm Hg and heart rate increased from 56 to 71 min-1. During sternotomy 8 of 16 patients (50%) developed hypertension and 9 of 16 patients (56%) showed signs of myocardial ischemia, i.e., a lactate and hypoxanthine release.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[The effect of sufentanil in high doses on hemodynamics and electroencephalography activity in coronary patients].

Sufentanil, a synthetic opioid that is 5-10 times as potent as fentanyl, has been suggested by some authors to prevent hypertensive responses to noxious stimuli in patients undergoing coronary artery bypass surgery much better than fentanyl, while in other studies it has failed to maintain cardiovascular stability during surgical stimulation. This study was designed to investigate the cardiovascular and electroencephalographic effects of high-dose sufentanil/O2/pancuronium anesthesia in patients undergoing coronary artery bypass surgery. METHODS. Two different doses of sufentanil were administered to two groups including a total of 20 male patients. Patients in group 1 (n = 10) received 10 micrograms.kg-1 sufentanil as an induction dose plus 0.15 microgram.kg-1.min-1 as a continuous infusion, while 10 micrograms.kg-1 plus 0.3 microgram.kg-1.min-1 were administered to the patients in group 2 (n = 10). Hemodynamic measurements were performed with the patients awake (I), 15 min following the induction of anesthesia with sufentanil and pancuronium at rest (II), and during sternotomy and sternal spreading (III). Patients were ventilated with oxygen in air (FiO2 = 0.5). Cerebral electrical activity was recorded by periodic analysis of the EEG, and plasma concentrations of sufentanil were measured throughout the entire study period. RESULTS AND DISCUSSION. The dosage scheme used in this study, which consisted of a sufentanil bolus followed by a continuous infusion, prevented plasma concentrations of sufentanil from declining in both groups during the entire study period. Following induction there was a significant decrease in systolic arterial pressure by 12% in group 1 and 20% in group 2 accompanied by a reduction in cardiac index by 25% and 21%, respectively, and in stroke volume index by 19% in group 1 and 24% in group 2, while systemic vascular resistance increased by 27% and 10%, respectively. Sternotomy led to a rise in systolic arterial pressure that did not exceed the awake values in both groups, while diastolic and mean arterial pressures (MAP) increased by 17% and 14% and by 15%, respectively, due to further increases in systemic vascular resistance by 57% and 41% above the control values. Cardiac and stroke volume indexes stayed significantly lower than the awake values, whereas heart rate remained essentially unchanged during the course of the study. There were no statistically significant differences between the groups during all measurements. In the EEG, sufentanil anesthesia was characterized by a decrease in the number of higher frequency waves and an increase in lower frequency (delta) waves, which did not change during sternotomy in 17 of the 20 patients.

Adult↗
PubMed1988

[Energy and amino acid metabolism in the human brain under Disoprivan anesthesia with various paCO2 values].

Propofol like thiopental and etomidate, suppresses cortical electrical activity in a dose-related manner, which leads to a 36% decrease in cerebral oxygen uptake and a 51% decrease in cerebral blood flow after an induction dose of 2 mg/kg followed by a maintenance dose of 0.2 mg/kg per min. In this study, the effects of propofol and varying paCO2 values on cerebral energy and amino acid metabolism were examined. METHODS. Eleven male patients between 49 and 63 years of age who were about to undergo coronary artery bypass surgery were studied. Measurements were performed with the patient awake (I), during steady-state maintenance anesthesia after propofol 2 mg/kg as an induction dose with 0.2 mg/kg per min by infusion with normocapnia (paCO2 39.9 +/- 3.1 mm Hg) (II), during hypocapnia (paCO2 29.9 +/- 2.6 mmHg) (III), and during hypercapnia (paCO2 50.6 +/- 3.3 mmHg) (IV). Cerebral blood flow was measured using the argon wash-in technique. A catheter was advanced into the superior bulb of the right internal jugular vein for measurement of cerebral oxygen, glucose, lactate, and amino acid uptake and release, which were calculated by multiplying the arterial-cerebral venous oxygen and substrate difference by the cerebral blood flow. Lactate/glucose index was calculated from the equation. Formula: see text. where a-vD lactate and a-vD glucose represent the arterial-cerebral venous substrate differences in mmol/l. Cerebral electrical activity was recorded by Fourier analysis of the EEG.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1988

[Effect of preoperative continuous nifedipine maintenance medication on hemodynamics and myocardial lactate extraction in coronary surgery patients].

The cardioprotective efficacy of preoperatively maintained long-term oral nifedipine application to 21 patients undergoing coronary artery bypass grafting (CABG) was investigated during fentanyl-N2O-anaesthesia. Two groups were defined at random; one group of patients receiving their normal morning doses together with the premedication, the other, who received the last nifedipine medication in the evening before surgery. Measurements where performed: 1. before induction of anaesthesia (reference value), 2. after induction, 3. at skin incision, 4. during sternotomy. There were no significant differences of hemodynamic parameters between the two groups. The hemodynamic parameters heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), and coronary perfusion pressure (CPP) decreased after induction in accordance with the plasma-concentrations of epinephrine and norepinephrine in both groups and increased again during sternotomy with HR and CI remaining below and MAP and CPP rising above the reference value. The nifedipine-plasma-concentrations were significantly higher in the group with the morning dose and just within the minimal therapeutic range before and after induction of anaesthesia. But during skin incision and sternotomy the plasma levels fell below 10 ng/ml, i.e. below the therapeutic level. The incidence of myocardial lactate extraction values greater than 10% was highest immediately after induction of anaesthesia and lowest during sternotomy with one patient in both groups exhibiting negative lactate extraction as a symptom of myocardial ischemia. The results suggest that the preoperatively maintained oral nifedipine medication of 10-20 mg p.o. was not able to provide sufficiently high nifedipine-plasma-levels during sternotomy nor to improve the hemodynamic state in patients with CABG.(ABSTRACT TRUNCATED AT 250 WORDS)

Anesthesia, General↗
PubMed1988

Comparison of brain structure volumes in insectivora and primates. VIII. Vestibular complex.

Volumes of the vestibular complex (VC) and its four main components (medial, inferior, lateral and superior nuclei; VM, VI, VL and VS) were measured in 28 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of non-human simians and in man. The relative size showed a definite tendency to increase 2-4.5 times from Insectivora through simians (expressed by size indices). The highest increase was found in VS, the lowest in VI and, in Pongidae and man, also in VL. The differences are discussed with respect to differences in the locomotory behavior of the various taxonomic groups and to differences in the fiber connections and thus different functions of the various nuclei. Species which exploit a 3-dimensional environment and execute fast and complicated head and body movements have a larger VC than closely related species confined to the ground or which are less skilled leapers. The great increase of the VS may be related to the predominant role of vision in primates, particularly in simians.

Animals↗
PubMed1988

Global and regional myocardial blood flow and metabolism during equipotent halothane and isoflurane anesthesia in patients with coronary artery disease.

Global and regional myocardial blood flow and metabolism were examined in 20 patients with coronary artery disease before surgical stimulation. Half were anesthetized with halothane (0.8%) and half with isoflurane (1.2%). Coronary perfusion pressure decreased similarly in both groups. During halothane anesthesia coronary sinus blood flow, an index of global perfusion, decreased from an awake value of 129 +/- 7 to 97 +/- 7 ml/min (P less than 0.05), and great cardiac vein blood flow, an index of regional perfusion, decreased from 60 +/- 8 to 44 +/- 5 ml/min (P less than 0.05). In contrast, during isoflurane anesthesia global coronary blood flow increased from 131 +/- 13 to 153 +/- 16 ml/min (P less than 0.05), while regional blood flow decreased from 68 +/- 7 to 56 +/- 6 ml/min (P less than 0.05). Thus, the ratio of great cardiac vein blood flow to coronary sinus blood flow was unchanged during halothane anesthesia but decreased significantly during isoflurane. Neither global nor regional coronary vascular resistance was altered by halothane, whereas isoflurane decreased global coronary vascular resistance without affecting regional coronary vascular resistance. All patients receiving halothane had net myocardial lactate extraction. In the isoflurane group, four patients showed global lactate production and three regional lactate production. All patients demonstrating lactate production also developed electrocardiographic evidence of myocardial ischemia, which was not present before induction. The authors conclude that halothane is a preferable anesthetic to isoflurane in patients with coronary artery disease because the latter has the propensity to induce maldistribution of the coronary circulation and myocardial ischemia.

Adult↗
PubMed1987

[Effect of Disoprivan (propofol) on the circulation and oxygen consumption of the brain and CO2 reactivity of brain vessels in the human].

The effects of Disoprivan on cerebral blood flow (CBF), cerebral oxygen consumption, and CO2-reactivity of the cerebral vessels were studied in 11 male patients between 49 and 63 years of age who were about to undergo coronary artery bypass surgery. Mean perfusion pressure was decreased by 25% under anaesthesia by 0.2 mg/kg per minute Disoprivan, but remained within the ranges of autoregulation. CBF decreased by 51% and cerebral vascular resistance (CVR) increased by 55% following a 36% decrease in cerebral oxygen consumption which was associated with a decrease in neuronal activity in the EEG. Hyperventilation led to a 25% further decrease in CBF due to a 43% increase in CVR while cerebral oxygen consumption remained unchanged. Hypoventilation was followed by a 67% increase in CBF and a 44% decrease in CVR cerebral oxygen consumption was decreased by 38%. This study shows that the reactivity of the cerebral vessels to changes in paCO2 is well maintained under Disoprivan.

Anesthesia, General↗
PubMed1987

Comparison of brain structure volumes in Insectivora and primates. VI. Paleocortical components.

Volumes of the main structures of the 'paleocortical complex' were measured in 2 species of Macroscelidea, 39 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of nonhuman simians and man. Changes in the relative size from Insectivora through man (expressed by size indices) showed a definite tendency to decrease in the lateral olfactory tract (TRL), its nucleus (NTO), and in the olfactory cortices (RB, PRPI, TOL) and to increase in the anterior commissure (COA) and substantia innominata (SIN). The reduction in the olfactory cortices is strongest for the retrobulbar region (RB, = anterior olfactory nucleus in Anglo-American terminology), and least for the olfactory tubercle (TOL). In prosimians, the reduction clearly parallels that of the main olfactory bulb (BOL); in simians and especially in man, the indices of PRPI and TOL are clearly larger than those of BOL. Possible reasons for these growing deviations were discussed: (1) increasing difficulties in clearly homologizing and delineating the olfactory cortices in the microsmatic simians, and (2) non-olfactory functional influences.

Animals↗
PubMed1987

[Non-invasive Doppler-ultrasound determination of cardiac output. Results and experiences with the ACCUCOM].

Because of the invasiveness of the method, the determination of cardiac output (CO) by the thermodilution technique is not without a certain risk to the patient. Previous studies have suggested that noninvasive Doppler technology could be used to determine the velocity of blood in the aorta. With knowledge of the diameter of the aorta, CO can be calculated. The newly developed ACCUCOM (Datascope Corp.) measures CO noninvasively by Doppler ultrasound. However, there is not much information as to how the ACCUCOM performs in clinical practice. The present study was designed to compare the determination of CO by the ACCUCOM with that by thermodilution. CO was determined simultaneously in 12 anesthetized patients scheduled for abdominal or orthopedic surgery. There was a significant but not very tight linear correlation (r = 0.82) between ACCUCOM and reference measurements. The ACCUCOM underestimated CO on the average by 32%. In order to analyze the ACCUCOM tracking of relative changes in CO, in 6 out of 12 patients CO was also determined during cardiac stimulation by isoprenaline (0.5-1.0 microgram.min-1) IV. The resulting increase in CO was detected reliably using the ACCUCOM. It was, however, significantly overestimated by the Doppler technique (average increase = 58%) as compared to the reference method (average increase = 42%). These results suggest the possibility of major deviations in determining CO with the ACCUCOM.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1987

Comparison of brain structure volumes in Insectivora and primates. VII. Amygdaloid components.

Volumes of the amygdaloid complex (AMY) and some subdivisions were measured in 2 species of Macroscelidea, 39 species of Insectivora, 3 species of Scandentia, 18 species of prosimians, 26 species of simians and man. Changes in the relative size from Insectivora through man (expressed by size indices) showed a definite tendency to increase in the cortico-basolateral subdivision (LAM) and more or less constant relations in the centromedial subdivision (MAM), except for the nucleus tractus olfactorii lateralis (NTO), which becomes distinctly reduced. The reduction of NTO is even stronger than that of the main olfactory bulb (BOL), which in simians and man is small but distinct, whereas NTO is hardly recognizable in most of these forms. In the LAM group the size increase of the large-celled part of the basal nucleus (MCB) is less than that of the small-celled components (including the lateral nucleus). The differences between LAM and MAM groups are discussed with regard to the predominant fiber connections, which in MAM are stronger with conservative brains parts (brainstem), and in LAM with progressive brain parts (e.g. neocortex).

Amygdala↗
PubMed1986

Effects of propofol on cardiovascular dynamics, myocardial blood flow and myocardial metabolism in patients with coronary artery disease.

The effects of propofol (emulsion formulation) on cardiovascular dynamics, myocardial blood flow and myocardial metabolism were studied in 12 patients scheduled for elective coronary artery bypass surgery. Measurements were performed with the patient awake, during steady-state maintenance anaesthesia with propofol 200 micrograms kg-1 min-1 at rest, and during sternotomy when the propofol was supplemented with fentanyl 10 micrograms kg-1. Propofol alone decreased mean arterial pressure and cardiac index; heart rate was increased. Myocardial blood flow and myocardial oxygen consumption were decreased by 26% and 31%, respectively. Myocardial lactate production was seen in one patient during this period. Surgical stimulation, under propofol-fentanyl anaesthesia, led to the return of arterial pressure and heart rate towards baseline; cardiac index decreased further. Myocardial blood flow and oxygen consumption increased such that they almost achieved their baseline values. Myocardial lactate production was seen in one patient. These results suggest that propofol may on occasions, lead to myocardial ischaemia in patients with coronary artery disease, but that it is able to block the sympathetic responses to surgical stimulation when combined with a suitable analgesic.

Adult↗
PubMed1986

The pineal organ of bats: a comparative morphological and volumetric investigation.

Bats are seasonal breeders and roost under a wide range of lighting conditions, from broad daylight to the total darkness of subterranean passageways and caves. Some are true hibernators. These characteristics and the paucity of information on their pineal organ prompted this investigation, which is based upon the pineals of 191 specimens of 88 species and 12 families of bats. Comparative morphological and volumetric observations have been made on serially sectioned brains of each species. Data include brain and body weights, mean pineal dimensions and volume, a computed pineal size index for each species and salient characteristics and relations of the pineal organ of the 12 chiropteran families. Generally speaking, despite some exceptions, larger bodied bats also have larger pineals. Bats of the microchiropteran families such as the Emballonuridae, Megadermatidae, Rhinolophidae, Hipposideridae, and a few vespertilionids (for example, Myotis adversus) and molossids (for example, Tadarida mops), have very large pineal organs, of which many reach the brain surface. All of these bat families inhabit dark caves. By contrast, in megachiropterans (pteropodids) which roost in broad daylight, the pineal lies deeply recessed and covered by the cerebral hemispheres. It is postulated that in general the superficial and deep location of pineal in micro- and megachiropteran species respectively may be a consequence of several factors, such as their habitat and their neocortical and cerebellar development. A system of classifying chiropteran pineal organs has been presented; in most species they are either of Type A or of Type AB. Most species have non-uniformly distributed parenchymal cells arranged in cords or clusters. In some species (for example, Rhinolopus trifoliatus and R. luctus) morphologically distinct dorsal and ventral divisions are observed. Pineal vascularity appears to be related to its size. Intrapineal neurons are rare and, when present, are associated with blood vessels. Epithelium-lined cavities are seen in the pineals of several species, while in a few others, the pineal is either absent or consists of a few scattered cells. Variable relationships between the pineal and the habenular commissure suggest that they may be unrelated functionally.

Animals↗
PubMed1986

The brain of Geogale aurita Milne-Edwards and Grandidier 1872 (Tenrecidae, Insectivora).

Macromorphology, composition, and encephalization of the brain of Geogale aurita, a small Madagascan tenrec, were studied. The relative brain size (encephalization) seems to be lower in Geogale than in the Tenrecinae (spiny or bristled tenrecs) which so far have been found to be at the bottom of the encephalization scale of extant mammalian species. Conservative features found in brain macromorphology are e.g. a minute corpus callosum and an uncovered tectum, and such found in brain composition are e.g. an extremely small neocortex and a large medulla oblongata. In all these brain characteristics, Geogale approaches more to the Tenrecinae than to the Oryzorictinae. However, including Geogale in the Tenrecinae would distinctly widen the range of variation of these characters in this subfamily. Therefore, a classification of Geogale in a specific subfamily would be more appropriate.

Animals↗