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A Nonlinear Circulatory Model for Artificial Heart Studies

1983

Animals with total artificial heart replacement (TAH) have survived for up to 9 months with manually controlled driving systems. A certain physiological control is provided by the animals intact peripheral regulation resulting in pathological venous hemodynamics, expressing the needs for a technical automatic control system, replacing the natural sympathetic stimulation and Starlings Law of the heart. A nonlinear dynamic mathematical model of the human cardiovascular system (CVSM) containing the systemic and pulmonary components was outlined and verified, which is employable to analyse the hemodynamic behaviour under normal and abnormal states. By modifying this model, assuming that cardiac…

Pathophysiology of Cerebral Ischemia

1991

The weight of the brain amounts to only 2% of total body weight, but it receives 15% of the cardiac output and uses 20% of the oxygen consumed by the body. The energy supply is provided almost exclusively by glucose metabolism. The substrate for this is stored in the brain in the form of glucose or glycogen and is sufficient to cover the energy requirements for only about 1 min. Consequently, there is a delicate equilibrium between oxygen and nutrient supply from the blood and the energy requirements of the brain. Disturbances in neurologic function appear after a few seconds of ischemia, although they are not necessarily persistent at first.

A mathematical model of cardiovascular dynamics for the diagnosis and prognosis of hemorrhagic shock

2020

Abstract A variety of mathematical models of the cardiovascular system have been suggested over several years in order to describe the time-course of a series of physiological variables (i.e. heart rate, cardiac output, arterial pressure) relevant for the compensation mechanisms to perturbations, such as severe haemorrhage. The current study provides a simple but realistic mathematical description of cardiovascular dynamics that may be useful in the assessment and prognosis of hemorrhagic shock. The present work proposes a first version of a differential-algebraic equations model, the model dynamical ODE model for haemorrhage (dODEg). The model consists of 10 differential and 14 algebraic e…

The influence of dopamine on hemodynamics, microcirculation and renal function in patients with hypnotic drug intoxication

1976

The effect of dopamine on hemodynamics (CO, AoPm, TPR, SV, SW, CVP, PAPm, PAEDP), microcirculation (MBF, PS-product) and renal function (VU, CKI, CNa, CK, Cosm, TcH2O) was studied in 8 patients with hypnotic drug poisoning. With increasing doses of dopamine, cardiac output and heart rate increased and the peripheral resistance decreased. An augmentation of stroke volume and left ventricular stroke work was observed in the low dose range only (200--400 mug/min). With increasing doses, central venous pressure as well as mean pulmonary artery pressure and enddiastolic pulmonary artery pressure decreased. No vasoconstriction was found in muscle tissue vessels even with large doses of dopamine. …

Hemodynamic monitoring and management in patients undergoing high risk surgery: a survey among North American and European anesthesiologists

2011

Abstract Introduction Several studies have demonstrated that perioperative hemodynamic optimization has the ability to improve postoperative outcome in high-risk surgical patients. All of these studies aimed at optimizing cardiac output and/or oxygen delivery in the perioperative period. We conducted a survey with the American Society of Anesthesiologists (ASA) and the European Society of Anaesthesiology (ESA) to assess current hemodynamic management practices in patients undergoing high-risk surgery in Europe and in the United States. Methods A survey including 33 specific questions was emailed to 2,500 randomly selected active members of the ASA and to active ESA members. Results Overall,…

Alcohol puts the heart under pressure: Acetaldehyde activates a localized renin angiotensin aldosterone system within the myocardium in alcoholic car…

2018

Special Considerations for Antihypertensive Agents in Dialysis Patients

2010

Hypertension is present in most patients with end-stage renal disease and likely contributes to the premature cardiovascular disease in dialysis patients. Previous practice guidelines have recommended that, in patients on chronic dialysis, blood pressure (BP) should be reduced below 130/80 mm Hg. This is based on opinions but not strong evidence, since no concrete information exists about which BP values should be the parameter to follow and which should be the target BP values. The majority of the antihypertensive agents can be used in this population, but the pharmacokinetics altered by the impaired kidney function and dialyzability influence the appropriate dosage as well as the time and…

Sleep Apnea: New Insights

2004

Sleep apnea is the most common disorder of breathing during sleep. It is defined as repeated episodes of obstructive apnea and hypopnea during sleep, together with daytime sleepiness or altered cardiopulmonary function [1]. There are three syndromes of upper airway closure during sleep: obstructive sleep apnea (OSA), obstructive sleep hypopnea, and upper airway resistance. These three syndromes share two features: excessive daytime sleepiness and arousal associated with increased ventilatory effort in response to upper airway closure. The specific sites of narrowing or closure and upper airway dysfunction are influenced by the underlying neuromuscular tone, upper airway muscle synchrony, an…

The Effect of Intracranial Pressure on Perifocal Hyperemia

1969

It is known that a reversiblecortical trauma caused by local brain compression in the cat is accompanied by a pronounced decrease of rCBF at the compressed area and by a transient perifocal hyperemia [1].

Oral administration of the growth hormone secretagogue NN703 in adult patients with growth hormone deficiency

2003

Summary objective Little is known of the usefulness of GH secretagogues (GHSs) in GH-deficient (GHD) adults. The objective of this study was to determine the number of responders to treatment with NN703 in GHD adults. design A multicentre, randomized, double-blind, and placebo-controlled study. patients Ninety-seven GHD adults were included. measurements The GH response before and after 1 week of oral treatment with NN703 (n = 83) or placebo (n = 14) was determined. The first and last dose of NN703 was 3 mg/kg, whereas the dose of NN703 was 1·5 mg/kg/day during the 6 days between the first and last doses. Furthermore, all 97 patients received 1 µg/kg GH-releasing hormone (GHRH) 3 weeks afte…