最新深静脉穿刺置管术(颈内、锁骨下、股静脉)含解剖图谱44884.ppt

* Representation of the association between cardiac preload (ventricular end-diastolic filling volume) and stroke volume: up to a certain limit, the stroke volume increases with increasing preload (area of volume responsiveness). The optimal filling volume is reached when a further increase of the preload leads to no further or only a slight increase in stroke volume (target area). If there is a further increase in preload beyond this point, there is then a fall in the stroke volume as the cardiac muscle is over-stretched and so loses some of its contractility (volume overload). This curve can demonstrate different slopes and different areas for volume responsiveness and volume overload depending on the contractility of the ventricle. * With low contractility, the Frank-Starling curve is flatter, i.e. when contractility is low, the same increase in preload leads to a smaller increase in stroke volume than with normal contractility. The ventricle with impaired contractility usually requires a higher preload volume to achieve its maximum ejection, but reacts more sensitively to volume overload so that the target area overall is usually narrower and shifted to the right compared to a ventricle with normal contractility. * When contractility is high, the course of the curve is steeper so that an identical increase in preload leads to a greater increase in stroke volume compared to normal contractility. The maximal stroke volume is reached at a low end-diastolic filling volume and the ventricle is less sensitive to volume overload so when the preload is increased excessively, it reacts later with a fall in stroke volume than the normally contractile ventricle. * Measurement of CO on its own does not allow the location on the Frank-Starling curve to be determined. In order to estimate the area where the individual patient‘s heart is located, the preload must be measured. * What parameters are available for measuring the preload? - classical parameters: cardiac filling pr