Measurement of cardiac output-transtracheal Doppler versus thermodilution

The ABCOM 1 transtracheal Doppler (TTD) has been developed as a non-invasive cardiac output monitor. With this device, cardiac output is continuously calculated from ascending aortic blood flow velocity and aortic diameter obtained via an ultrasound transducer incorporated into the tip of an endotracheal tube. We evaluated the clinical use of the ABCOM 1 monitor and compared cardiac outputs obtained using the TTD system with simultaneous thermodilution (TD) measurements. We found the operation of the ABCOM 1 monitor to be difficult and time-consuming. In our operating rooms, acceptable Doppler signal quality was difficult to obtain. There was no correlation between 36 simultaneously obtained TTD and TD cardiac output measurements. The average difference between measurement techniques and the limits of agreement were unacceptably large (mean difference = 3.04 L.min-1, mean +/- 2 SD = -6.04 to 12.48 L.min-1). Separately analyzing only those measurements during which Doppler signal quality was adequate did not improve agreement between TTD and TD measurements. On the basis of these findings, TTD cannot be recommended as a clinical cardiac output measurement technique.     

Influence of an acute increase in systemic vascular resistance on transpulmonary thermodilution-derived parameters in critically ill patients

Objective The transpulmonary thermodilution technique enables measurement of cardiac index (CI), intrathoracic blood volume (ITBV), global end-diastolic volume (GEDV), and extravascular lung water (EVLW). In this study, we analyzed the robustness of this technique during an acute increase in systemic vascular resistance (SVR). Design Prospective, clinical study. Setting Surgical intensive care unit in a university hospital. Patients and methods Twenty-four mechanically ventilated septic shock patients, who for clinical indications underwent extended hemodynamic monitoring by transpulmonary thermodilution and continuously received norepinephrine. Interventions and main results After baseline measurements, mean arterial pressure was increased briefly by increasing norepinephrine dosage and hemodynamic measurements were repeated before a control measurement was obtained. At each time point, 15 cc of 0.9% saline (< 8 °C) was administered by central venous injection in triplicate. Fluid status and respirator adjustments were kept constant. ANOVA with an all-pairwise comparison method was used for statistical analysis. Heart rate, central venous pressure, and EVLW remained constant throughout, while SVR significantly changed from 551 ± 106 to 746 ± 91 dyn*s*cm⁻⁵ and again to 566 ± 138 dyn*s*cm⁻⁵ (p < 0.05). However, CI and central blood volumes showed a reversible significant increase, i.e., ITBV went from 816 ± 203 to 867 ± 195 ml/m² and then to 821 ± 205 ml/m² and GEDV from 703 ± 178 to 747 ± 175 ml/m² and finally to 704 ± 170 ml/m², respectively. In eight patients, 2-D echocardiography was applied and revealed a reversible increase in left-ventricular end-diastolic area. Conclusion An acute increase in SVR by increasing norepinephrine dosage results in a reversible increase in central blood volumes (ITBV, GEDV) as measured by transpulmonary thermodilution and supported by echocardiography. This work was presented in part at the 19th annual meeting of the European Society of Intensive Care Medicine, 24–27 September 2006, Barcelona. Samir Sakka has received fees from Pulsion Medical Systems AG, Munich, Germany, for giving lectures.     

Basics of Coronary Thermodilution

Coronary microvascular dysfunction is a highly prevalent condition in both obstructive and nonobstructive coronary artery disease. Intracoronary thermodilution is a promising technique to investigate coronary microvascular (dys)function in vivo and to assess its most important metric: microvascular resistance. Here, the authors provide a practical review of bolus and continuous thermodilution for the measurement of coronary flow and microvascular resistance. The authors describe the basic principles of indicator-dilution theory and of coronary thermodilution and detail the practicalities of their application in the catheterization laboratory. Finally, the authors discuss contemporary clinical applications of coronary thermodilution–based microvascular assessment in humans and future perspectives.     

Hydraulic Bench Testing of the TruCATHTM/TruCCOMTM Continuous Cardiac Output Monitor

The aim of this study was to test the truCATH^TM/ truCOMMS^TM continuous cardiac output catheter/monitor in a computer-controlled pulsatile mock loop system. The pulmonary artery catheter is equipped with two thermistors and a heating coil which maintains a 2°C temperature difference between the thermistors. The required electrical power is assumed to be an indicator of cardiac output. The catheter was tested under a variety of loading conditions including changes in heart rate (60, 75, 90, 120 beats/mm), filling pressures (0–15 mmHg), ventricular driving pressures (22–135 mmHg), and pulmonary resistance (0.08–1.47 mmHgs/mL) in random combinations, generating flows of 1.5–10 L/min. Fluid temperature was varied between 32 and 42°C. Our data demonstrate a good linear relation between the electrical power output of the TruCATH^TM/TruCOMMS^TM catheter and the actual flow as measured volumetrically. The system appeared to be sensitive to fluid temperature changes, but dimensionless analysis with Womersley and Reynolds numbers revealed that it is a direct consequence of the temperature-dependent water viscosity. We conclude that the TruCATH^TM/TruCOMMS^TM is a potentially useful clinical tool but the absolute correspondence between the catheter output and the patient's actual cardiac output remains to be assessed.     

脉搏指示连续心排血量技术在心脏前负荷测量的应用近况

监测心脏负荷变化对了解心脏功能具有十分重要的临床意义。中心静脉压(CVP)与右心前负荷虽存在一定关系,但不能完全反映左心前负荷。经动脉插管入左心房及肺动脉漂浮导管(Swan-Ganz导管)测量肺小动脉嵌顿压(PCWP)评估左心前负荷的方法,虽能为判断心脏前负荷提供较为可靠的依据,     

应用经肺热稀释技术评价幼猪心输出量和容量负荷

目的 评价经肺热稀释法(TPTD)测量心输出量(CO)的准确性,以及该方法测量的胸内血容量指数(ITBVI)用于评价容量负荷的有效性。方法 研究10只幼猪,体重(20.6±1.9)kg。分别在基础血容量、高血容量和低血容量状态下进行同步的肺动脉热稀释法(PATD)测量CO(CO_PA)和TPTD测量CO(CO_TP)、ITBVI,每种状态下连续测量3次,同时记录中心静脉压(CVP)和心率。分析不同血容量状态下CVP、ITBVI与心指数(CI)、每搏输出量指数(SVI)的相关性。结果 共进行90次同步热稀释法测量CO。CO_TP与CO_PA相关系数为0.977(P＜0.001),平均偏差为(0.25±0.26)L/min(95%CI:0.20～0.30 L/min,P＜0.001)。CO_TP变异系数为3.7%,CO_PA变异系数为5.4%。与基础血容量状态比较,高血容量状态下CVP和ITBVI均显著升高(P=0.002、0.019),低血容量状态下ITBVI显著下降(P＜0.001),但CVP的差异无统计学意义(P=0.050)。相关分析显示ITBVI与CI和SVI在基础血容量状态下呈高度正相关(r=0.741,P=0.014;r=0.885,P=0.001),在高血容量和低血容量状态下均无显著相关性;CVP与CI和SVI在各种血容量状态下均无显著相关性。结论 TPTD在不同血容量状态下测量CO的准确度和精确度均理想,其测量的ITBVI与CVP比较可更有效地反映容量负荷。     

Thermodilution cardiac output. Cold vs room temperature injectate and the importance of measuring the injectate temperature in the right atrium

BACKGROUND: The feasibility of thermodilution cardiac output measurements with the more convenient room temperature thermal indicator instead of cold injectates has been repeatedly investigated. However, the issue has not been addressed with the appropriate statistical approach advocated by Altman and Bland. Furthermore, we wished to determine if the incorporation of a second thermistor in the thermodilution catheter, to measure the temperature of the thermal indicator where it is delivered into the right atrium/superior caval vein, would result in more precise cardiac output measurements. METHODS: Fifty patients were randomized to receive a single or dual thermistor pulmonary artery thermodilution catheter. Cardiac output was calculated as the average of four injections of 10 ml of isotonic saline. Precision (2 x SD of differences in replicate measurements) for the two catheters and injectate temperatures, and bias and limits of agreement between measurements, with cold and room temperature injectates, were determined. RESULTS: Precision was (0 degrees C) 0.42 l/min and (20 degrees C) 0.90 l/min, and bias and limits of agreement -0.83 l/min and -1.93-0.27 l/min for the single thermistor catheter. For the dual thermistor system precision was (0 degrees C) 0.34 l/min and (20 degrees C) 0.58 l/min. Bias and limits of agreement were -0.03 l/min and -0.61-0.55 l/min. CONCLUSION: The second thermistor is redundant if cold injectates are used. If one wishes to use room temperature injectates the single thermistor system is inadequate. A dual thermistor catheter is, on the other hand, acceptable.     

冠状动脉微循环功能的定量评估技术及进展

冠状动脉微循环功能异常在某些情况下可导致或促成心肌缺血，广泛存在于各种心血管危险因素和疾病中，常与患者不良结局有关。目前临床上缺乏冠状动脉微血管疾病的标准化定义和特异性诊断方法，导致只能对其进行经验性治疗。本综述重点介绍用于评估冠状动脉微循环功能的相关指标、主要技术及进展，以期对冠状动脉微血管疾病的预防和诊疗提供参考。