Peripheral and central venous blood oxygen saturation used to indicate systemic vascular resistance
Laleh Alim Marvasti
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Introduction: We used a new index to evaluate Systemic Vascular Resistance (SVR) which included arterial, peripheral and central venous saturations. Method: Twenty candidates for coronary artery bypass surgery were enrolled. SVR was calculated at two different time points (when patient is at pre-pump stage and then onpump stage). At each time point, SVR was measured conventionally and with this new method. The conventional method utilized echocardiography and pump indices to calculate SVR. Forty pairs of data were analyzed. Correlation and agreement between conventional SVR measurements and SVR index were assessed. Result: There was good correlation and agreement between the new and conventional method. Pearson coefficient was 0.83 and 0.93 (prepump and on-pump respectively) (p < 0.001). Bland-Altman plot of percentage difference in pre-pump and on-pump measurements showed 0.1 and -0.05 unit bias, and limits of agreement were -0.4 to 0.65 and -0.5 to 0.4 units respectively. Measured SVR can be predicted by SVR index using linear regression. Pre-pump SVR (Dynes.Sec.cm-5.1000-1) = 0.57 (95% CI: 0.2-0.8) × pre-pump SVR Index + 0.9 (95% CI: 0.6-1.2) On-pump SVR (Dynes.Sec.cm-5.1000-1) = 0.58 (95% CI: 0.3-0.7) × on-pump SVR Index + 0.6 (95% CI: 0.4-0.8) Conclusion: This novel index had good statistical agreement with the conventional method. It is a simple, less invasive and inexpensive technique. For general application of this method, further studied are necessary.