Thrush D N, Varlotta D
Department of Anesthesiology, University of South Florida, College of Medicine, Tampa 33612.
J Cardiothorac Vasc Anesth. 1992 Feb;6(1):17-9. doi: 10.1016/1053-0770(91)90038-u.
In clinical practice, cardiac output (CO) is usually reported as the average of thermodilution determinations with injection of the thermal indicator performed at end-exhalation. However, an average of multiple determinations with injections equally dispersed throughout the respiratory cycle has been shown to provide the best estimate of mean CO. This study sought to determine the reproducibility of CO determinations obtained with manual injections of indicator solution performed at end-exhalation, compared with those determined by computer-controlled injections equally dispersed throughout the breathing cycle of 27 patients undergoing cardiac operations. Mean CO was calculated by averaging the four determinations obtained with each technique before induction of anesthesia, after induction of anesthesia, after sternotomy, after cardiopulmonary bypass, and after sternal closure. A total of 130 pairs of mean CO estimations were obtained with manual and automated injections. Mean CO values obtained with manual injections were significantly lower than those obtained with the dispersed injection technique (5.0 +/- 1.4 L/min vs 5.3 +/- 1.6 L/min, P = 0.002). The bias between CO values measured with the manual technique was -0.25 +/- 0.47 L/min lower than those obtained with the dispersed technique. The mean relative bias for the group was 7 +/- 18% with 95% confidence intervals of +/- 26%. During mechanical ventilation, the thermodilution technique with manual injection of indicator solution significantly underestimated CO. Variability in the manual injection technique and inappropriate representation of the mean CO by injections timed to occur at end-exhalation contributed to the disparity. These results indicate that the manual technique of determining CO at end-exhalation may not accurately reflect the average CO.
在临床实践中，心输出量（CO）通常报告为呼气末注射热指示剂后热稀释测定值的平均值。然而，已表明在整个呼吸周期中均匀分散注射进行多次测定的平均值能提供对平均CO的最佳估计。本研究旨在确定与通过计算机控制在27例接受心脏手术患者的呼吸周期中均匀分散注射所测定的CO相比，呼气末手动注射指示剂溶液所获得的CO测定的可重复性。在麻醉诱导前、麻醉诱导后、胸骨切开后、体外循环后和胸骨闭合后，通过对每种技术获得的四次测定值求平均来计算平均CO。通过手动和自动注射共获得130对平均CO估计值。手动注射获得的平均CO值显著低于分散注射技术获得的值（5.0±1.4升/分钟对5.3±1.6升/分钟，P = 0.002）。手动技术测量的CO值之间的偏差比分散技术低-0.25±0.47升/分钟。该组的平均相对偏差为7±18%，95%置信区间为±26%。在机械通气期间，手动注射指示剂溶液的热稀释技术显著低估了CO。手动注射技术的变异性以及呼气末定时注射对平均CO的不恰当表示导致了差异。这些结果表明，呼气末手动测定CO的技术可能无法准确反映平均CO。
