Clancy M J, Alderman J, Cavallero N, Taylor K J
Accident and Emergency Department, Bristol Royal Infirmary, United Kingdom.
J Accid Emerg Med. 1996 Sep;13(5):316-20. doi: 10.1136/emj.13.5.316.
To determine, using an animal model of blood loss, (1) if stroke distance, derived non-invasively from the time integral of the maximum velocity of red cells in the aorta, changed to a greater extent than heart rate and mean arterial pressure (MAP), which are recognised to be unreliable indicators of blood loss; (2) if changes in stroke distance reflected changes in stroke volume derived from thermodilution cardiac output measurements.
Eight anaesthetised swine had baseline measurements of heart rate, MAP, stroke volume, and stroke distance and were then exsanguinated at a rate of 1 ml/kg/min. Percentage changes from baseline of heart rate, MAP, stroke volume, and stroke distance were compared after 10, 20, and 30 ml/kg blood loss. The animal's blood was then reinfused at the rate of 2 ml/kg/min for 15 min, followed by normal saline 1 ml/kg/min. Percentage changes from baseline measurement of stroke volume and stroke distance over the whole experiment were evaluated by regression analysis.
Heart rate, MAP, and stroke distance changed +7.9%, -22.5%, and -18.1% respectively (from baseline values) after 10 ml/kg blood loss; +23.2%, -44.0%, and -47.4% after 20 ml/kg blood loss; and +55.7%, -62.0%, and -69.8% after 30 ml/kg blood loss. Regression analysis of percentage changes in stroke volume and stroke distance from their baseline values at experimental time zero is stroke volume = 1.014 x stroke distance -2.156, r = 0.92, n = 54, P < 0.0001.
(1) At maximal blood loss, stroke distance changes to a greater extent than heart rate and MAP. (2) Changes in stroke distance reflected changes in stroke volume but with less variability at lower values. Stroke distance may be a more useful measure of blood loss than heart rate and MAP.
利用失血性动物模型，（1）确定从主动脉红细胞最大速度的时间积分无创得出的搏出距离，其变化程度是否大于心率和平均动脉压（MAP），已知心率和平均动脉压是不可靠的失血指标；（2）确定搏出距离的变化是否反映了热稀释法心输出量测量得出的每搏量的变化。
八只麻醉猪进行心率、MAP、每搏量和搏出距离的基线测量，然后以1 ml/kg/min的速率放血。在失血10、20和30 ml/kg后，比较心率、MAP、每搏量和搏出距离相对于基线的百分比变化。然后以2 ml/kg/min的速率将动物的血液回输15分钟，随后以1 ml/kg/min的速率输注生理盐水。通过回归分析评估整个实验过程中每搏量和搏出距离相对于基线测量的百分比变化。
失血10 ml/kg后，心率、MAP和搏出距离分别相对于基线值变化了+7.9%、-22.5%和-18.1%；失血20 ml/kg后分别为+23.2%、-44.0%和-47.4%；失血30 ml/kg后分别为+55.7%、-62.0%和-69.8%。实验开始时每搏量和搏出距离相对于其基线值的百分比变化的回归分析结果为：每搏量 = 1.014×搏出距离 - 2.156，r = 0.92，n = 54，P < 0.0001。
（1）在最大失血量时，搏出距离的变化程度大于心率和MAP。（2）搏出距离的变化反映了每搏量的变化，但在较低值时变异性较小。搏出距离可能是比心率和MAP更有用的失血指标。
