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Interactions among venoarterial extracorporeal membrane oxygenation, macrocirculation, and microcirculation may have unintended consequences.
Contexts in source publication
Context 1
... coagulation and inflammatory systems, may all lead to further cardiac injury. Therefore, merely replacing the native pump (patient's own heart) with a nonpulsatile, continuous flow pump (venoarterial extracorporeal membrane oxygenation) without optimizing the microcirculation and unloading the left ventricular may result in suboptimal outcomes ( fig. ...
Context 2
... measurements during venoarterial extracorporeal membrane oxygenation are a means to an end and may help us better understand and address the research questions in relation to macro-and microcirculation ( fig. 1) that may ultimately lead to improved outcomes. In the future, holistic monitoring during venoarterial extracorporeal membrane oxygenation may include continuous monitoring of cardiac mechanics and output, pulmonary pressures, hemostasis, microcirculation, and brain tissue oxygenation. Defining cardiogenic shock patient populations ...
Context 3
... coagulation and inflammatory systems, may all lead to further cardiac injury. Therefore, merely replacing the native pump (patient's own heart) with a nonpulsatile, continuous flow pump (venoarterial extracorporeal membrane oxygenation) without optimizing the microcirculation and unloading the left ventricular may result in suboptimal outcomes ( fig. ...
Context 4
... measurements during venoarterial extracorporeal membrane oxygenation are a means to an end and may help us better understand and address the research questions in relation to macro-and microcirculation ( fig. 1) that may ultimately lead to improved outcomes. In the future, holistic monitoring during venoarterial extracorporeal membrane oxygenation may include continuous monitoring of cardiac mechanics and output, pulmonary pressures, hemostasis, microcirculation, and brain tissue oxygenation. Defining cardiogenic shock patient populations ...
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Background
Thermodilution is unreliable in veno-venous extracorporeal membrane oxygenation (VV-ECMO). Systemic oxygenation depends on recirculation fractions and ratios of ECMO flow to cardiac output. In a prospective in vitro simulation, we assessed the diagnostic accuracy of a modified thermodilution technique for recirculation and cardiac output. We hypothesized that this method provided clinically acceptable precision and accuracy for cardiac output and recirculation.
Methods
Two ECMO circuits ran in parallel, one representing a VV-ECMO, the second representing native heart, lung and circulation. Both circuits shared the right atrium. Extra limbs for recirculation and pulmonary shunt were added. We simulated ECMO flows from 1 to 2.5 l/min and cardiac outputs from 2.5 to 3.5 l/min with recirculation fractions (0 – 80%) and pulmonary shunts. Thermistors in both ECMO-limbs and the pulmonary artery measured the temperature changes induced by cold bolus injections into the arterial ECMO-limb. Recirculation fractions were calculated from the ratio of the areas under the temperature curve (AUC) in the ECMO-limbs and from partitioning of the bolus volume (flow based). With known partitioning of bolus volumes between ECMO and pulmonary artery, cardiac output was calculated. High precision ultrasonic flow probes served as reference for Bland-Altman plots and linear mixed-effect models.
Results
Accuracy and precision for both the recirculation fraction based on AUC (bias -5.4 %; limits of agreement (LoA) -18.6 to 7.9 %) and flow based (bias -5.9 %; LoA -18.8 to 7.0 %) are clinically acceptable. Calculated cardiac output for all recirculation fractions was accurate, but imprecise (RecirculationAUC: Bias 0.56 L/min; LoA -2.27 to 3.4 L/min; RecirculationFLOW: Bias 0.48 L/min; LoA -2.22 to 3.19 L/min). Recirculation fraction increased bias and decreased precision.
Conclusions
Adapted thermodilution for VV-ECMO allows simultaneous measurement of recirculation fraction and cardiac output and may help optimize patient management with severe respiratory failure.
Assessment of native cardiac output during extracorporeal circulation is challenging. We assessed a modified Fick principle under conditions such as deadspace and shunt in 13 anesthetized swine undergoing centrally canulated veno-arterial extracorporeal membrane oxygenation (V-A ECMO, 308 measurement periods) therapy. We assumed that the ratio of carbon dioxide elimination (V̇CO 2 ) or oxygen uptake (V̇O 2 ) between the membrane and native lung corresponds to the ratio of respective blood flows. Unequal ventilation/perfusion (V̇/Q̇) ratios were corrected towards unity. Pulmonary blood flow was calculated and compared to an ultrasonic flow probe on the pulmonary artery with a bias of 99 mL/min (limits of agreement -542 to 741 mL/min) with blood content VO 2 and no-shunt, no-deadspace conditions, which showed good trending ability (least significant change from 82 to 129 mL). Shunt conditions led to underestimation of native pulmonary blood flow (bias -395, limits of agreement -1290 to 500 mL/min). Bias and trending further depended on the gas (O 2 , CO 2 ), and measurement approach (blood content vs. gas phase). Measurements in the gas phase increased the bias (253 [LoA -1357 to 1863 mL/min] for expired V̇O 2 bias 482 [LoA -760 to 1724 mL/min] for expired V̇CO 2 ) and could be improved by correction of V̇/Q̇ inequalities. Our results show that common assumptions of the Fick principle in two competing circulations give results with adequate accuracy and may offer a clinically applicable tool. Precision depends on specific conditions. This highlights the complexity of gas exchange in membrane lungs and may further deepen the understanding of V-A ECMO.
