We performed a post-hoc analysis of a prospective study in septic patients who were resuscitated according a strict non-CVP guided treatment protocol. Simultaneous measurements of hemodynamics and sublingual Sidestream Dark Field imaging were obtained 0 and 30 minutes after fulfillment of resuscitation goals. Data were examined for differences in microcirculatory variables for CVP less than or equal to or greater than 12 mmHg and its evolution over time, as well as for predictors of a microvascular flow index (MFI) less than 2.6.
In 70 patients with a mean APACHE II score of 21, 140 simultaneous measurements of CVP and sublingual microcirculation (vessels less than 20 µmeter) were obtained. (MFI) and the percentage of perfused small vessels (PPV) were significantly lower in the ‘high’ CVP (greater than 12 mmHg) group as compared to patients in the ‘low’ CVP (less than or equal to 12 mmHg) group (1.4 ± 0.9 vs. 1.9 ± 0.9, P = 0.006; and 88 ± 21% vs. 95 ± 8%, P = 0.006 respectively). Perfusion pressure (MAP–CVP) and cardiac output did not differ significantly between both CVP groups. From time point 0 to 30 minutes, a significant increase in MFI (from 1.6 ± 0.6 to 1.8 ± 0.9, P = 0.027) but not in PPV, was observed, while CVP and perfusion pressure significantly decreased in the same period. In a multivariate model CVP greater than 12 mmHg was the only significant predictor for a capillary MFI less than 2.6 (Odds ratio 2.5 (95% confidence interval 1.1-5.8), P = 0.026).
We observed a significant association between a higher CVP and impairment of microcirculatory blood flow. Further research is needed to elaborate on our hypothesis generating findings that an elevated CVP may act as an outflow obstruction of organ perfusion.