RESUMO
BACKGROUND: Microcirculatory driving pressure is defined as the difference between post-arteriolar and venular pressure. In previous research, an absence of correlation between mean arterial blood pressure (MAP) and microcirculatory perfusion has been observed. However, the microcirculation may be considered as a low pressure compartment with capillary pressure closer to venous than to arterial pressure. From this perspective, it is conceivable that central venous pressure (CVP) plays a more important role in determination of capillary perfusion. We aimed to explore associations between CVP and microcirculatory perfusion. METHODS: 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 ≤ or > 12 mmHg and its evolution over time, as well as for predictors of a microvascular flow index (MFI) < 2.6. RESULTS: In 70 patients with a mean APACHE II score of 21, 140 simultaneous measurements of CVP and sublingual microcirculation (vessels < 20 µmeter) were obtained. (MFI) and the percentage of perfused small vessels (PPV) were significantly lower in the 'high' CVP (> 12 mmHg) group as compared to patients in the 'low' CVP (≤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 > 12 mmHg was the only significant predictor for a capillary MFI < 2.6 (Odds ratio 2.5 (95% confidence interval 1.1-5.8), P = 0.026). CONCLUSION: 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.
RESUMO
BACKGROUND: Microcirculatory alterations play a pivotal role in sepsis and persist despite correction of systemic hemodynamic parameters. Therefore it seems tempting to test specific pro-microcirculatory strategies, including vasodilators, to attenuate impaired organ perfusion. As opposed to nitric oxide donors, magnesium has both endothelium-dependent and non-endothelium-dependent vasodilatory pathways. METHODS: In a single-center open label study we evaluated the effects of magnesium sulphate (MgS) infusion on the sublingual microcirculation perfusion in fluid resuscitated patients with severe sepsis and septic shock within the first 48 hours after ICU admission. Directly prior to and after 1 hour of magnesium sulphate (MgS) infusion (2 gram) systemic hemodynamic variables, sublingual SDF images and standard laboratory tests, were obtained. RESULTS: Fourteen patients (12 septic shock, 2 severe sepsis) with a median APACHE II score of 20 were enrolled. No significant difference of the systemic hemodynamic variables was found between baseline and after MgS infusion. We did not observe any significant difference pre and post MgS infusion in the primary endpoint microvascular flow index (MFI) of small vessels: 2.25(1.98-2.69) vs. 2.33(1.96-2.62), p = 0.65. Other variables of microcirculatory perfusion were also unaltered. In the overall unchanged microvascular perfusion there was a non-significant trend to an inverse linear relationship between the changes of MFI and its baseline value (y = -0.7260 × + 1.629, r2 = 0.270, p = 0.057). The correlation between baseline Mg concentrations and the change in MFI pre- and post MgS infusion was non-significant (rs = -0.165, p = 0.67). CONCLUSIONS: In the setting of severe sepsis and septic shock sublingual microcirculatory alterations were observed despite fulfillment of sepsis resuscitation guidelines. After infusion of a limited and fixed dose of MgS, microcirculatory perfusion did not improve over time. TRIAL REGISTRATION: ClinicalTrials.gov NTC01332734.
