Department of Anesthesiology, Baystate Medical Center, Springfield, MA; Tufts University School of Medicine, Boston, MA.
J Cardiothorac Vasc Anesth. 2013 Dec;27(6):1140-4. doi: 10.1053/j.jvca.2013.06.011. Epub 2013 Sep 30.
Cardiac and stroke indices routinely are used to communicate the adequacy of circulation, especially by cardiac anesthesiologists. However, indexed values may be distorted when derived using conventional formulae on morbidly obese patients. In extreme cases, distortion of the raw value by the indexed value may suggest inappropriate therapeutic interventions. This study attempted to highlight threshold values of body surface area (BSA) that place morbidly obese patients at risk of being overtreated.
Mathematical analysis.
Simulated patients.
BSA was derived using the commonly used Mosteller and Dubois and Dubois formulae on a range of simulated patients. These simulated BSAs then were applied to normal cardiac output (CO) and stroke volume (SV) values to identify the threshold at which BSA-indexed values result in a change in classification to abnormal. Additionally, the effects of 7 different published BSA formulae were examined, using a range of height-weight combinations.
Critical thresholds at which BSA calculations would classify normal CO and SV as abnormal are presented in a tabular form. Among the 7 BSA formulae, there was substantial variation in predicted BSA at a given height-weight combination when values typically associated with morbid obesity are used.
In morbidly obese patients, cardiac and stroke indices can be misleading relative to the underlying raw values (CO and SV) as a result of distortion by widely used BSA formulae. The authors caution against relying on threshold cardiac and stroke indices as triggers for the initiation of hemodynamic therapies in the morbidly obese. Further research on what BSA formula should be used on patients with very extreme body types is warranted.
心脏和中风指数常用于传达循环的充分性，尤其是由心脏麻醉师使用。然而，在病态肥胖患者中，使用传统公式推导指数值可能会导致失真。在极端情况下，指数值对原始值的扭曲可能会导致不适当的治疗干预。本研究试图强调体表面积（BSA）的阈值，使病态肥胖患者面临过度治疗的风险。
数学分析。
模拟患者。
使用常用的 Mosteller 和 Dubois 公式以及 Dubois 公式在一系列模拟患者中得出 BSA。然后，将这些模拟的 BSA 应用于正常的心输出量（CO）和每搏输出量（SV）值，以确定 BSA 指数值导致分类异常的阈值。此外，还使用一系列身高体重组合检查了 7 种不同的已发表 BSA 公式的影响。
以表格形式呈现了 BSA 计算将正常 CO 和 SV 分类为异常的临界阈值。在 7 种 BSA 公式中，当使用与病态肥胖相关的值时，在给定的身高体重组合下，预测的 BSA 存在很大差异。
在病态肥胖患者中，由于广泛使用的 BSA 公式的扭曲，心脏和中风指数相对于潜在的原始值（CO 和 SV）可能会产生误导。作者警告不要依赖心脏和中风指数阈值作为启动病态肥胖患者血液动力学治疗的触发因素。需要进一步研究在非常极端体型的患者中应使用哪种 BSA 公式。
