Cardiovascular system stroke volume

Practitioners must have a good understanding of cardiovascular physiology to diagnose, treat, and monitor circulatory problems in critically ill patients. Eugene Braunwald, a renowned cardiologist, described the interrelationships between the major hemodynamic variables (Fig. 10-1).1 These variables include arterial blood pressure, cardiac output (CO), systemic vascular resistance (SVR), heart rate (HR), stroke volume (SV), left ventricular size, afterload, myocardial contractility, and preload. While an oversim-... 

Cardiovascular system Decreased peripheral vascular resistance increased heart rate, stroke volume, cardiac output, pulse pressure high-output heart failure increased inotropic and chronotropic effects arrhythmias angina Increased peripheral vascular resistance decreased heart rate, stroke volume, cardiac output, pulse pressure low-output heart failure ECG bradycardia, prolonged PR interval, flat T wave, low voltage pericardial effusion... 

The function of the cardiovascular system is to maintain adequate tissue perfusion. Cardiac output is the product of heart rate (rhythm) and cardiac contractility (giving rise to stroke volume). These factors are under neuronal, hormonal and mechanical control systems. Pharmacological manipulation of any of these contributors will result in changes in cardiovascular function and hence peripheral blood flow. In human medicine, the primary goal is to increase life expectancy, while maintenance of performance and quality of life are the main priorities in equine medicine. 

Propane has been shown to have adverse effects on the cardiovascular system in the primate, dog, cat, and mouse. Guinea pigs exposed to 2.2-5.5% of the gas showed sniffing and chewing movements. In dogs, 1% caused hemodynamic changes, whereas 3.3% produced decreases in aortic pressure, stroke volume, and cardiac output and an increase in pulmonary resistance. Ten percent propane in the mouse and 15% in the dog did not produce arrhythmia but did produce weak cardiac sensitization. 

Blood pressure (BP) is a product of the total peripheral resistance (TPR) times the cardiac output (CO). The CO is equal to the heart rate (HR) times the stroke volume (SV). The autonomic (neural) system helps regulate the BP through feedback control involving the baroreceptors, the cardiovascular centers in the brain stem, and the PANS and SANS, which act in an opposing but coordinated manner to regulate the pressure. 

Chapter 17 adopts a comparative approach using biological scaling laws to compare the cardiovascular systems of different mammals. Allometry, the change of proportions with increase of size, and dimensional analysis is used to develop allometric relations for important cardiovascular parameters such as stroke volume, peripheral resistance, and heart efficiency. Optimal cardiovascular design is also discussed. 

Non-invasive monitoring of blood pressure has become increasingly important in research. High-Definition Oscillometry (HDO) delivers not only accurate, reproducible and thus reliable blood pressure but also visualises the pulse waves on screen. This allows for on-screen feedback in real time on data validity but even more on additional parameters like systemic vascular resistance (SVR), stroke volume (SV), stroke volume variances (SVV), rhythm and dysrhythmia. Since complex information on drug effects are delivered within a short period of time, almost stress-free and visible in real time, it makes HDO a valuable technology in safety pharmacology and toxicology within a variety of fields like but not limited to cardiovascular, renal or metabolic research. 

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