Search PubMed⌕ Search

Biomedical subjects

W Hess

Publications and source records attributed to W Hess.

At least 91 records · Page 5Linked to original sources
PubMed1976

Haemodynamics and myocardial oxygen consumption during isoflurane (forane) anaesthesia in geriatric patients.

The influence of isoflurane on haemodynamics and myocardial oxygen consumption was examined in seven geriatric patients under conditions of controlled ventilation and a normal arterial carbon dioxide tension. During isoflurane/nitrous oxide in oxygen anaesthesia (0.75 and 1.5 vol% inspired isoflurane) no significant changes occurred in cardiac output, stroke volume, heart rate, central venous and pulmonary artery pressure. Arterial pressure decreased, as did total peripheral resistance. A reduction in left ventricular maximum dp/dt (18-39%) was, at least in part, a result of changes in loading conditions. Total body (CaO2--CVO2) and base excess values remained within the normal range. We consider that the oxygen supply was adequate to meet the metabolic demands of the body as a whole. Myocardial oxygen consumption decreased by 25% during 0.75 vol% inspired isoflurane and by 43.5% with deepening of anaesthesia (1.5 vol% isoflurane).

Anesthesia, Inhalation↗
PubMed1976

[The effect of Fentanyl and Althesin on haemodynamics, inotropism of the heart and myocardial oxygen consumption in man (author's transl)].

The acute effect of Fentanyl and Althesin upon haemodynamics, inotropism of the heart and myocardial oxygen consumption has not been studied in man so far. Healthy premedicated pateints (n = 16) were lightly anaesthetized with nitrous oxide-oxygen (ratio 2:1), 0.3 Vol.-% forane and 0.3 Vol.-% halothane respectively. In order to avoid any interference with respiratory depression all subjects were normoventilated via an orotracheal tube. In a circulatory steady state a single dose of 0.01 mg/kg Fentanyl (n = 7) and 0.075 mg/kg Althesin (n = 9) respectively was injected intravenously within 20 sec. After the application of Fentanyl there was a delayed (5th min) fall in blood pressure by 23%, which was due to a reduction in total peripheral resistance (12%) and in cardiac output (thermodilution technique) by 13%. The decrease in cardiac output was the result of a bradycardia (18%). Considering heart rate, pre- and afterload simultaneously, the fall in max dp/dt (catheter-tip manometer) by 20% could not be explained as a decrease in myocardial contractility. The altered haemodynamics led to a decrease of the myocardial oxygen consumption (control 6.4 ml O2/min x 100 g) by 31%. The energy demand of the heart was quantitatively calculated using the formula of the complex haemodynamic parameter developed by Bretschneider. Immediately after the administration of Althesin the cardiac output rose on account of tachycardia slightly, while stroke volume (19%), total peripheral resistance (32%) and mean arterial pressure (24%) reacted reversely. Since heart rate increased (11%), preload remainded unchanged and afterload decreased, the fall in dp/dt max (20%) has to be understood as a moderate reduction in myocardial inotropism. The energy demand of the heart decreased only initially by 15%. The clinical implications of the results were discussed.

Adult↗
PubMed1976

[The effects of sodiumnitroprusside and trimethaphan induced hypotension on haemodynamics and myocardial oxygen consumption (author's transl)].

The influence of controlled hypotension (mean arterial pressure 60 mmHg) induced by sodium nitroprusside and trimethaphan on systemic circulation and myocardial oxygen consumption was studied in 7 anaesthetized closed chest dogs. The hypotensive effect of both drugs was primarily mediated by a reduction in total peripheral resistance. No change in cardiac output was observed. Stroke volume decreased in the presence of tachycardia. Left ventricular max dp/dt remained unaffected during sodium nitroprusside hypotension and was reduced by trimethaphan. Max dp/dt, load data and heart rate indicated that trimetaphan possesses negative inotropic properties. Sodium nitroprusside induced a hyperperfusion of the heart with a marked decrease in myocardial arteriovenous difference in oxygen. Myocardial oxygen consumption remained unchanged. Trimethaphan, on the other hand, induced only small increments in coronary blood flow and a rise in the arteriovenous difference in oxygen of the heart. This resulted in a higher myocardial oxygen consumption (+16%). Cardiac efficiency was lessened by trimethaphan and remained unaffected in the presence of sodium nitroprusside. As sodium nitroprusside neither affects myocardial oxygen consumption nor alters myocardial contractility, we conclude that sodium nitroprusside has advantages over trimethaphan in the management of controlled hypotension and in the therapy of hypertensive crisis and cardiogenic shock.

Animals↗
PubMed1976

[Effect of high dosages of fentanyl and piritramide upon haemodynamics, coronary blood flow and myocardial oxygen consumption (author's transl)].

High dosages of narcotic analgesics are frequently utilized as the sole anaesthetic agents for patients requiring open-heart surgery. The purpose of this study was to investigate the effect of high dosages of fentanyl and piritramide upon the cardiovascular system. In anaesthetized dogs (N2O:O2=2:1; 0.5 vol% halothane) 0.03 mg/kg fentanyl (=8) and 1.5 mg/kg piritramide (n=8) respectively were given intravenously as a bolus. After the administration of fentanyl there was a slight decrease in blood pressure (10%). The hypotension was the result of a decrease in cardiac output (thermodilution technique) by 13% due to bradycardia. Total peripheral resistance and myocardial contractility remained unaffected. Similar effects were only found late after injection of piritramide, since there was an initial cardiovascular response to piritramide characterized by a marked fall in blood pressure (29%). The major cause of arterial hypotension was peripheral vasodilatation. Load data and the decrease in max dp/dt however indicated also a slight myocardial depression. The altered haemodynamics led to a decrease in myocardial oxygen consumption with both narcotics, which was nearly paralleled by a reduction in coronary blood flow. The narrowing of arteriovenous oxygen difference of the heart proved coronary dilatatory properties of fentanyl and especially of piritramide. This study indicated that high dosages of fentanyl have advantages in comparison to high dosages of piritramide. The clinical implications of the results are discussed.

Animals↗
PubMed1975

[Cardiovascular effects of the new inhalation anaesthetic isoflurane in man (author's transl)].

Cardiovascular responses to isoflurane (forane)-nitrous oxide-oxygen anaesthesia were studied in seven older premedicated patients. Anaesthesia was induced with the new non-barbiturate induction agen etomidate. All patients were intubated and mechanically ventilated to maintain normal PaCO2. Clinical concentrations of isoflurane (0.75 and 1.5 vol.-% inspiratory) decreased mean arterial pressure 22%-42%. Only small reductions in cardiac output and stroke volume were seen. Heart rate, central venous and pulmonary artery pressure remained nearly unaffected. The major cause of the arterial hypotension was a fall in total peripheral resistance by 36% as anaesthesia deepened. Left ventricular maximum dp/dt and load data indicated that isoflurane also possesses negative inotropic properties. Tension-time-index and total body oxygen consumption decreased by 47% and 20% respectively. AVDO2 values remained within the normal range. We take this to mean that the oxygen supply was adequate to meet the metabolic demands of the body as a whole. This was corroborated by the finding that base excess did not change significantly. Conclusions considering the use of isoflurane in patients with diminished cardiovascular reserve are drawn.

Adult↗
PubMed1973

Induction kinetics of the L-arabinose operon of Escherichia coli.

After addition of l-arabinose to growing Escherichia coli, the l-ribulokinase (EC 2.7.1.16) and l-arabinose isomerase (EC 5.3.1.4) first appear at about 0.7 and 1.4 min, respectively. These times are consistent with the distances of the genes from the ribonucleic acid polymerase initiation site in the operon. The kinetics of appearance of these enzymes as well as those of beta-galactosidase (EC 3.2.1.23) in the same strain are consistent with a peptide elongation rate of no less than 14 amino acids per second. A measurement of the average peptide elongation rate made by measuring the kinetics of radioactive amino acid appearance in completed polypeptides yielded a rate of about 12 amino acids per s. Convenient assays of the arabinose isomerase and ribulokinase are also given.

Arabinose↗