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Assessment of blood flow during extra-corporeal circulation from arterial waveform analysis


The pressure recording analytical method (PRAM) is a recently developed method for beat-to-beat quantification of cardiac output (CO) based on the analysis of the arterial waveform. Since PRAM can be implemented in various conditions of flow, we assessed its accuracy in cardiac surgery during extra-corporeal circulation (ECC), using the roller pump device (RP) as the reference gold standard.


In 25 patients undergoing cardiac surgery, CO values obtained by the PRAM from the radial artery were compared with bolus thermodilution (TD) before and after ECC, and with the RP readings during ECC before and after aortic clamp. PRAM flow measurements during ECC were based on the analysis of each sinusoidal arterial waveform (the continuous component of flow) produced by the RP.


The estimates of blood flow measured by the PRAM closely agreed with TD (r2 = 0.75; P < 0.0001; bias = 0.07 ± 0.40; coefficient of variation < 2%) and simultaneous RP readings (r2= 0.71; P < 0.0001; bias = 0.11 ± 0.33; coefficient of variation 2.5%). During weaning from ECC, two patterns of hemodynamic adaptation were documented by PRAM following resumption of cardiac contraction. (1) Most patients (Fig. 1A, upper line) had a rapid and stable recovery of CO (a reduction < 10% as compared with ECC flow) at the decreasing of RP-infused volumes (lower line). (2) Five patients showed a marked fall in CO > 10% up to38% (Fig. 1B, upper line) and required longer ECC assistance and weaning time (lower line), and inotropic support. In Figs 1A,1B, shaded areas represent the cardiac contribution to CO.

figure 1

Figure 1


The PRAM provided accurate and continuous quantification of flow during each phase of cardiac surgery. This new method may allow early recognition of low CO during weaning from ECC.


  1. Romano SM, Pistolesi M: Assessment of cardiac output from systemic arterial pressure in humans. Crit Care Med 2002, 30: 1834-1841. 10.1097/00003246-200208000-00027

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Scolletta, S., Biagioli, B., Giomarelli, P. et al. Assessment of blood flow during extra-corporeal circulation from arterial waveform analysis. Crit Care 8 (Suppl 1), P48 (2004).

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