Biomedical subjects

B Biber

Publications and source records attributed to B Biber.

At least 73 records · Page 4Linked to original sources

PubMed1988

Hemodynamic changes during laparoscopy with positive end-expiratory pressure ventilation.

Hemodynamic measurements were performed in 10 healthy women undergoing elective laparoscopy for the investigation of infertility. A standardized anesthetic technique which included the application of positive end-expiratory pressure (PEEP), 0.49 kPa (3.7 mmHg) was utilized. The following variables were studied: cardiac output, stroke volume and left ventricular ejection time (determined non-invasively with impedance cardiography), heart rate, blood pressure, total peripheral vascular resistance and end-tidal carbon dioxide (ET-CO2). The combination of 25 degrees head-down tilt and PEEP ventilation during laparoscopy was associated with a pressure response that restored arterial pressures to essentially pre-anesthetic levels. Net cardiac effects were small. With this regime low pressure 0.7-1.1 kPa (5-8 mmHg) intra-abdominal insufflation with CO2 was associated with only minor cardiovascular changes. There were no indications that 0.49 kPa PEEP during laparoscopy produced adverse cardiovascular effects. The application of PEEP reduced (P less than 0.001) ET-CO2. There was no net increase in ET-CO2 after CO2-insufflation compared to the measurement after induction of anesthesia. This is in contrast to earlier studies without PEEP where a significant net increase in ET-CO2 was reported after CO2-insufflation.

Adult↗

PubMed1988

Effects of dopamine on the portal circulation after therapeutic hepatic artery ligation.

The effects of exogenous dopamine (2, 4 and 6 micrograms.kg-1.min-1 i.v.) on the portal circulation were studied in six patients following therapeutic hepatic artery ligation. Portal blood flow (PBF) was measured by the continuous thermodilution technique. Portal venous pressure (PVP, n = 3) was monitored through the thermodilution catheter to allow derivation of preportal vascular resistance (PVR). Blood samples were taken through the portal venous catheter for measurement of dopamine. A significant increase in PBF and a decrease in PVR were observed during graded i.v. dopamine infusion. Thus, PBF was 961 +/- 119 ml.min-1 during control conditions and increased to 1446 +/- 221 ml.min-1 during the dopamine infusion at 6 micrograms.kg-1.min-1. No significant changes in mean arterial pressure or PVP were observed during dopamine administration. The pharmacokinetics of dopamine did not differ from that previously reported in patients with an intact arterial supply. In conclusion, our data indicate that exogenous dopamine consistently increases PBF by preportal vasodilation, also in patients with a surgically restricted hepatic arterial blood supply.

Adult↗

PubMed1988

Improved techniques for cardiovascular monitoring in rats as applied during endotoxemia.

We describe a new combination of techniques for measurements of systemic blood pressure, central venous pressure, pulmonary arterial (PA) pressure, PA wedge pressure, and cardiac output in the rat. Application of the method to the conscious rat in a septic shock (Escherichia coli endotoxin iv injection) model demonstrated a response pattern of decreased cardiac output and stroke volume, increased total peripheral vascular resistance and heart rate, and transiently decreased systemic arterial pressure. In the pulmonary circulation, a very brief hypertension and a sustained increase in pulmonary vascular resistance were observed, but changes in PA wedge pressure were small. The soft PA catheter (0.3 mm ID, 0.6 mm OD) had no undue effects on cardiovascular function. We suggest that this combined technique could be useful for many cardiovascular studies in the rat, not only as related to shock research.

Animals↗

PubMed1987

Dose-related effects of isoflurane on superior mesenteric vasoconstriction induced by endotoxemia in the rat.

To investigate the interplay between endotoxin-induced circulatory shock and the cardiovascular effects of different doses of isoflurane, mean aortic pressure (MAP), central venous pressure (CVP), mean pulmonary arterial pressure (MPAP), heart rate (HR), cardiac output and superior mesenteric artery flow (SMAF), were monitored in rats anesthetized with either 1.4% or 2.0% isoflurane in oxygen. Cardiac index (Cl), total peripheral vascular resistance (TPR) and superior mesenteric vascular resistance (SMVR) were derived. During continuous administration of isoflurane, endotoxin (LD90, 40 mg X kg-1 iv) was given after a 30-min baseline period, and data were collected for an additional 2-h period. Sham-challenged (saline) animals served as controls. The response to endotoxin in the systemic circulation showed a decrease in Cl and MAP, while HR and TPR increased. MPAP and CVP were essentially unchanged. There were no significant differences in the systemic circulation variables between endotoxin groups, apart from a more pronounced HR increase during 1.4% isoflurane. Regionally, however, SMAF was lower and SMVR was higher in the 2.0% versus the 1.4% isoflurane group following endotoxin. To conclude, the degree of mesenteric vasoconstriction during endotoxemia was dependent on the dose of isoflurane. This dose-related effect seems to be mediated through interaction with intrinsic vascular control, a higher dose allowing a more pronounced local blood flow reduction.

Animals↗

PubMed1987

Choice of anesthetic alters the circulatory shock pattern as gauged by conscious rat endotoxemia.

A standardized rat endotoxin shock model was used to assess the differential effects of four commonly used anesthetics upon hemodynamics before and during endotoxin shock. Forty-nine male Sprague-Dawley rats weighing 307 +/- 4 g were divided into five groups:freely-moving conscious, enflurane (2%), isoflurane (1.4%), pentobarbital (6 mg.kg-1.h-1 i.v.), and ketamine (45 mg.kg-1.h-1 i.v.). Anesthetic doses were chosen as 1.0 MAC equivalent. Anesthetized rats were intubated and ventilated with oxygen. The right carotid artery was cannulated with a thermocouple-catheter for aortic blood pressure, heart rate, and thermodilution cardiac output measurements. The right jugular vein was cannulated for measurement of central venous pressure and for i.v. injections. Data were collected over a 30-min baseline period and for 4 h after an i.v. bolus of endotoxin (40 mg.kg-1, LD100 within 24 h). Gross small intestinal pathology was rated on a 0-4 scale. Anesthetic effects were judged in terms of significant deviations from the awake data on each parameter. Despite differing patterns, total deviations were similar for enflurane, ketamine, and pentobarbital, although the latter drug was the least preferable due to particularly high systemic vascular resistance. Significantly less hemorrhagic small intestinal pathology occurred with enflurane. Ketamine offered no advantage over the inhalation anesthetics. Among the four anesthetics tested, results were closest to the awake pattern with isoflurane anesthesia, thus making it the logical choice for hemodynamic studies in experimental shock research.

Anesthetics↗

PubMed1987

Fatal iron intoxication in late pregnancy.

A case of intoxication with 5 g of elemental iron (25 g of ferrous sulfate) in a 30-year old woman at 36 weeks gestation is reported. Deferoxamine treatment was given with a delay of 26 hours after ingestion. A healthy infant was delivered by cesarean section 31 hours following ingestion. Subsequently, the patient developed hepatic necrosis, coma and hemostatic dysfunction and expired in cardiac failure after two weeks. The fatal outcome supports the view that the potential lethal dose of iron is lower for adults than for children. This case also demonstrates that major hepatic dysfunction can be a prominent feature of adult cases of iron intoxication. It is not unequivocal that early institution of deferoxamine treatment would have had a significant influence on the outcome. However, taking into account the well-documented efficacy of the drug in children and that no major adverse fetal effects have been associated with deferoxamine treatment in pregnancy, we suggest such antidote therapy to be considered for prompt institution in similar cases.

Adult↗

PubMed1986

Portal blood flow in man during graded positive end-expiratory pressure ventilation.

The cardiovascular response to graded PEEP ventilation (5-10 cm H20) was studied peroperatively in patients undergoing cholecystectomy (n = 8) or hepatic tumour surgery (n = 3). Portal blood flow was measured by the continuous thermodilution technique and cardiac output, in a sub-group of the patients, by impedance cardiography. A parallel reduction in cardiac output and portal blood flow was demonstrated in patients undergoing cholecystectomy as the result of the application of PEEP. Thus, ventilation with 5 cm H2O of PEEP elicited a 17% decrease in cardiac output and a 26% decrease in portal blood flow. During 10 cm H2O of PEEP cardiac output decreased by 22% and portal blood flow by 32%. However, there were no significant changes in preportal tissue perfusion pressure by the application of PEEP and preportal vascular resistance increased by 22% and 30%, respectively. This indicates that a vasoconstrictor response, elicited by PEEP, in the preportal tissue is the predominating mechanism for the observed decrease in portal blood flow. Systemic oxygen transport decreased by 214 ml/min during PEEP ventilation, but preportal tissue oxygen utilization was not significantly changed due to a concurrent increase (2.9%; p less than 0.05) in oxygen extraction.

Adolescent↗

PubMed1986

Influence of isoflurane on renal and intestinal vascular responses to stress.

Renal and intestinal vasoconstrictor responses elicited by either hypothalamic defence alarm area activation or stimulation of somatic and visceral afferents were studied in 17 cats. In part I, the circulatory adjustments during 2% (end-tidal) isoflurane plus 70% nitrous oxide in oxygen were compared with a medium-dose fentanyl in 70% nitrous oxide-oxygen sequence which was supplemented by diazepam. In part II, three end-tidal concentrations of isoflurane (1.4%, 2% and 3%) plus nitrous oxide in oxygen were evaluated before and after pre-treatment with droperidol 200 micrograms kg-1. During fentanyl-diazepam anaesthesia, intense vasoconstrictor responses with associated decreases in renal and intestinal blood flows were observed. Isoflurane 2% counteracted this reflex vasoconstriction, particularly in the renal vascular bed. The pressor and vasoconstrictor responses were suppressed by isoflurane in a dose-dependent fashion. After the administration of droperidol, the vascular beds were unaffected by noxious stimulation. It is concluded that isoflurane blunts stress-related vasoconstriction in a dose-dependent fashion, especially in the renal, but also in the intestinal, circulation. Droperidol adds to the vasodilatory effect of isoflurane.

Animals↗

PubMed1986

Carotid sinus baroreceptor modulation of fluid transport and blood flow in the feline jejunum.

Carotid sinus baroreceptor control of jejunal fluid transport and vascular resistance was studied in chloralose-anesthetized cats. The carotid sinuses were isolated and perfused with blood from the femoral arteries. The aortic nerves were divided. In an isolated jejunal segment we measured net fluid transport rate, transmural potential difference (PD), and blood flow at a constant perfusion pressure of 75 mmHg. Carotid sinus pressure (CSP) was increased to 200-250 mmHg and was then lowered, in steps of approximately 25 mmHg, down to 50 mmHg. In the pressure interval from 90 to 200 mmHg, decreases in CSP increased jejunal vascular resistance and fluid absorption rate and decreased PD. In the interval from 50 to 90 mmHg, decreases in CSP increased vascular resistance and decreased PD but did not affect net fluid absorption rate. The results indicate that changes in baroreceptor activity may reflexly influence both vascular resistance and fluid transport rate in the feline jejunum, possibly via separate sympathetic mechanisms.

Animals↗

PubMed1985

[Glaucoma, ocular hypertension and diabetic retinopathy].

71 out of 4803 diabetics attending the special outpatient clinic for diabetic eye complications at the 1st Eye Department of the University of Vienna were found to be suffering from glaucoma. Ocular hypertension was observed in 717 cases. Neither the course of diabetic retinopathy nor the correlation between duration of diabetes mellitus and the manifestation of retinal changes differed from the findings in diabetics with normal ocular pressure. The hypothesis that increased ocular pressure in response to the topical application of steroids might be of beneficial influence on the course of diabetic retinopathy was not confirmed by these observations.

Diabetes Mellitus, Type 1↗

PubMed1985

Cardiovascular studies during controlled baroreflex activation in the dog: I. Effects of enflurane.

In chloralose-anaesthetized dogs the carotid sinuses were bilaterally perfused with blood from a femoral artery, either at systemic arterial pressure through a direct by-pass or with a pump in order to control the sinus pressure. Influences from cardiac receptors and aortic baroreceptors were eliminated by denervation. Administration of enflurane (1.6% end-tidal concentration) with the presence of barostatic modulation, i.e. the carotid sinuses were perfused at prevailing systemic arterial pressure, reduced cardiac performance (cardiac output, cardiac contractility, heart rate and left ventricular stroke work) and mean arterial pressure. When barostatic compensation of enflurane-induced circulatory changes was prevented by maintaining sinus perfusion pressure constant at the pre-enflurane level, these haemodynamic alterations, with the exception of cardiac output, were significantly more pronounced. Furthermore, systemic vascular resistance decreased. We conclude that barostatic reflexes significantly modify cardiovascular depressive effects of enflurane.

Animals↗

PubMed1985

Cardiovascular studies during controlled baroreflex activation in the dog: II. Effects of metoprolol and enflurane.

An experimental model was designed to study circulatory drug effects with or without barostatic reflex influences. In dogs anaesthetized with chloralose, both carotid sinuses were perfused from a femoral by-pass either with systemic arterial pressure or with a pump in order to control the sinus pressure. Cardiac and aortic baroreceptors were denervated. I.v. metoprolol (240 micrograms X kg-1 + 102 micrograms X kg-1 X h-1) with constant carotid sinus pressure and thereby constant baroreceptor activation reduced cardiac output, heart rate, cardiac contractility and left ventricular stroke work index. Systemic vascular resistance increased. This response was independent of the degree of baroreflex activation. During the combined administration of enflurane (1.6% end-tidal concentration) and metoprolol, cardiac performance (cardiac output, stroke volume, heart rate, cardiac contractility and left ventricular stroke work index) was depressed independent of the degree of baroreflex activation. Barostatic reflexes, however, counteracted an observed decrease in systemic vascular resistance. This reflex vascular response was, during metoprolol-enflurane administration, associated with an increased left ventricular end-diastolic pressure.

Animals↗

PubMed1985

Maternal haemodynamic changes during caesarean section: a comparison of epidural and general anaesthesia.

Haemodynamic measurements were performed on 20 healthy women before and during elective caesarean section under epidural (10 women) or general anaesthesia (10 women). The influence of the two anaesthetic techniques on the haemodynamic changes associated with operative delivery was compared. The following haemodynamic variables were studied: cardiac output (CO), stroke volume (SV) determined non-invasively with impedance cardiography, heart rate (HR), systolic (SBP) and diastolic blood pressure (DBP), pulse pressure, mean arterial pressure (MAP) and total peripheral vascular resistance (TPR). During epidural anaesthesia, SV was largely unchanged before delivery but increased (P less than 0.05) following delivery. However, CO increased (P less than 0.05) prior to delivery due to an increase (P less than 0.01) in HR. A further increase (P less than 0.05) in CO was recorded following delivery. SBP, DBP, MAP and TPR decreased (P less than 0.01) during epidural anaesthesia. In the patients undergoing general anaesthesia, SV decreased (P less than 0.05) prior to delivery. However, CO remained largely unchanged due to an increase (P less than 0.01) in HR. Following delivery, CO (P less than 0.05) and SV (P less than 0.01) increased whereas HR decreased (P less than 0.01). SBP, DBP and MAP increased (P less than 0.01) prior to delivery, returning to the same level as prior to induction of anaesthesia following delivery. TPR was largely unchanged prior to delivery but decreased (P less than 0.01) following delivery.

Anesthesia, Epidural↗

PubMed1985

Vasodilator responses to enflurane in the small intestine.

Local effects of enflurane on intestinal vascular resistance were studied in vivo in cats. A jejunal segment was prepared and perfused at constant flow with blood from the femoral arteries. The intestine was either: (1) left with intact sympathetic innervation, (2) denervated and exposed to electrical post-ganglionic vasoconstrictor nerve stimulation, or (3) excluded from neurogenic remote control by post-ganglionic denervation. Enflurane dissolved in lipid and intra-arterially administered to the jejunal segment in doses comparable to those clinically encountered, decreased intestinal vascular resistance in relation to the intra-arterial concentration of the drug. The vasodilator response was, at the highest enflurane doses studied (blood concentration: 400 and 800 mg X 1(-1], most pronounced in the intestine with intact sympathetic innervation. Otherwise, no differences were observed in vasodilator responses between the three different investigated modes of neurogenic influence on the intestine. In vitro enflurane (-in-lipid) did not affect the vasoconstrictor response to electrical field stimulation in the rat mesenteric arterioles. Enflurane, however, dose-dependently reduced spontaneous contractile activity in the rat portal veins.

Animals↗

PubMed1985

Intestinal vascular effects of inhaled and locally administered enflurane in the cat.

The effects of enflurane on intestinal vascular resistance and blood flow in the intestine were studied in cats during basal chloralose anaesthesia. A jejunal segment was prepared and perfused with blood from both femoral arteries, allowing control of intestinal inflow pressure. Mesenteric venous blood flow was measured with an optical drop recorder. During constant intestinal arterial pressure (75 mmHg; 10 kPa), intestinal vascular resistance was calculated during enflurane inhalation at MAC 0.5 and 1.0 before and after postganglionic denervation of the jejunal segment. Inhalation of enflurane reduced intestinal vascular resistance in a dose-dependent fashion. The decrease in vascular resistance was attenuated but not abolished by post-ganglionic denervation, indicating both peripheral and central nervous sites of action for enflurane. Furthermore, with the intestinal segment perfused at systemic arterial pressure, the effects of locally intraarterially infused enflurane dissolved in a fat emulsion was studied. A vasodilator response was elicited in the intestine when exposed to local arterial enflurane concentrations in the same range as encountered during surgical anaesthesia in man, supporting the hypothesis of a peripheral site of action.

Anesthesia, Inhalation↗

PubMed1985

Cardiovascular effects of enflurane and asphyxia during long-term beta 1-adrenoceptor blockade.

The haemodynamic effects of enflurane (1.7% and 3.4% expiratory concentrations) were investigated in sheep (n = 6) pretreated with an infusion of metoprolol (0.2 mg X kg-1 X h-1 for 5 days) and in control animals (n = 6). Chloralose was used as basal anaesthetic. A 90 s apnoea period was included in the experiment to evaluate further the possible side-effects of long-term metoprolol treatment in combination with enflurane anaesthesia. MAC 1.0 for enflurane in the sheep was found at 1.45% end-tidal concentration by separate measurements. Before enflurane administration, the only significant differences between the two groups of animals were a lower systemic vascular resistance and a higher stroke volume during metoprolol treatment. Enflurane abolished these discrepancies in a dose-dependent fashion and similar cardiovascular depression was observed in both groups of animals at 3.4% expiratory concentration of enflurane. Metoprolol did not significantly affect the hypertensive response to apnoea during chloralose anaesthesia alone. At enflurane 1.7% expiratory concentration the apnoea response was small and only the metoprolol-treated animals showed a significant increase in left ventricular end-diastolic pressure. We conclude that 5 days of pretreatment with metoprolol in the sheep model does not significantly impair cardiovascular performance during enflurane anaesthesia.

Adrenergic beta-Antagonists↗

PubMed1985

Effects of isoflurane on vascular tone and circulatory autoregulation in the feline small intestine.

The vascular response in autoperfused small intestine was studied in ten cats during basal chloralose anaesthesia and controlled ventilation with either air, nitrous oxide/oxygen (70/30) or 0.7% end-tidal concentration of isoflurane + nitrous oxide/oxygen (70/30). Intestinal blood flow was measured by the optical drop recording technique, and intestinal perfusion pressure was kept constant at either 100, 75 or 50 mmHg (13.30, 9.98 or 6.65 kPa). At perfusion pressures of 100 and 75 mmHg (13.30 and 9.98 kPa), intestinal blood flow was significantly increased and intestinal vascular resistance decreased during isoflurane- + nitrous oxide/oxygen anaesthesia, compared with nitrous oxide/oxygen or air. According to the equation of closed loop gain (Gf), autoregulation was active in the pressure range 100-75 mmHg (13.30-9.98 kPa). In the pressure range 75-50 mmHg (9.98-6.65 kPa), the autoregulatory capacity was attenuated during air or nitrous oxide/oxygen and absent during isoflurane + nitrous oxide/oxygen. The vasodilator responses and the autoregulatory pattern were not changed by post-ganglionic intestinal denervation. The intestinal vasodilator effect of isoflurane was further investigated in the denervated intestine, perfused at systemic arterial pressure by local intra-arterial administration of isoflurane dissolved in a fat emulsion. A dose-dependent vasodilator response was hereby observed.

Anesthesia, General↗

PubMed1985

Does dopamine suppress stress-induced intestinal and renal vasoconstriction?

Dopamine interference with intestinal and renal sympathetic reflex vasoconstrictor responses was studied in cats anaesthetized with diazepam, fentanyl and nitrous oxide. Vasoconstriction was induced by electric stimulation of the hypothalamic defence-alarm area and by stimulation of somatic and visceral afferents. In addition, intestinal vasoconstriction was elicited by direct stimulation of postganglionic sympathetic efferent nerves. In the intestine, dopamine administration (7.5 microgram X kg-1 X min-1) was not associated with an attenuation of the investigated sympathetic vasoconstrictor responses, although dopamine per se decreased intestinal vascular resistance by 36 +/- 4%. Due to this dopamine-induced background vasodilation, the intestinal blood flow level during stimulation procedures and concomitant dopamine infusion was higher than during similar stimulations prior to dopamine (for defence-alarm area stimulation 45 +/- 16%, for afferent nerve stimulation 79 +/- 22% and for efferent postganglionic nerve stimulation 66 +/- 16%). In the kidney, dopamine per se had only minor effects on vascular resistance and on changes in vascular tone elicited by the stimulation procedures. The renal blood flow level in response to the stimulation procedures was not significantly affected by dopamine. In conclusion, dopamine may contribute to a sustained intestinal blood flow level when administered during supervening stress-related sympathetic activation.

Anesthetics↗