Cerebral venous congestion during cardio-pulmonary bypass: role of bispectral index monitoring

Is venous congestion associated with reduced cerebral oxygenation and worse neurological outcome after cardiac arrest?

Background

Post-cardiac arrest (CA) patients are at risk of secondary ischemic damage in the case of suboptimal brain oxygenation during an ICU stay. We hypothesized that elevated central venous pressures (CVP) would impair cerebral perfusion and oxygenation (venous cerebral congestion). The aim of the present study was to investigate the relationship between CVP, cerebral tissue oxygen saturation (SctO₂) as assessed with near-infrared spectroscopy (NIRS) and outcome in post-CA patients.

Methods

This was an observational study in 48 post-CA patients with continuous CVP and SctO₂ monitoring during therapeutic hypothermia.

Results

The relationship between CVP and mean SctO₂ was best described by an S-shaped, third-degree polynomial regression curve (SctO₂ = −0.002 × CVP³ + 0.08 × CVP² – 1.07 × CVP + 69.78 %, R² 0.89, n = 1,949,108 data points) with high CVP (>20 mmHg) being associated with cerebral desaturation. Multivariate linear regression revealed CVP to be a more important determinant of SctO₂ than mean arterial pressure (MAP) without important interaction between both (SctO₂ = 0.01 × MAP – 0.20 × CVP + 0.001 × MAP × CVP + 65.55 %). CVP and cardiac output were independent determinants of SctO₂ with some interaction between both (SctO₂ = 1.86 × CO – 0.09 × CVP – 0.05 × CO × CVP + 60.04 %). Logistic regression revealed that a higher percentage of time with CVP above 5 mmHg was associated with lower chance of survival with a good neurological outcome (cerebral performance category (CPC) 1–2) at 180 days (OR 0.96, 95 % CI 0.92–1.00, p = 0.04). In a multivariate model, the negative association between CVP and outcome persisted after correction for hemodynamic variables, including ejection fraction and MAP.

Conclusions

Elevated CVP results in lower brain saturation and is associated with worse outcome in post-CA patients. This pilot study provides support that venous cerebral congestion as indicated by high CVP may be detrimental for post-CA patients.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-016-1297-2) contains supplementary material, which is available to authorized users.

Experimental treatment of superior venous congestion during cardiopulmonary bypass

OBJECTIVES

Superior venous outflow obstruction affects cerebral perfusion negatively by reducing cerebral perfusion pressure (CPP). We present a randomized study designed to compare two alternative strategies to preserve the CPP during superior vena cava (SVC) congestion and cardiopulmonary bypass (CPB).

METHODS

Fourteen pigs on bi-caval CPB were subjected to 75% occlusion of the SVC flow. CPP was restored either by vasopressor treatment (VP, n = 7) or by partial relief (PR) of the congestion (n = 7). The cerebral effects of the interventions were studied for 60 min with intracranial pressure (ICP) monitoring, cerebral blood flow measurement, the near-infrared light spectroscopy tissue oxygen saturation index (StO2), arterial and venous blood gas analyses and serial measurements of the glial cell damage marker protein S100β.

RESULTS

Both strategies restored the CPP to baseline levels and no signs of severe ischaemia were observed. In the PR group, the venous and ICPs were normalized in response to the intervention, while in the VP group those parameters remained elevated throughout the experiment. The haemoglobin oxygen saturation in the sagittal sinus (SsagO2) was increased by both VP and PR, while significant improvement in the StO2 was observed only in the PR group. The S100β concentrations were similar in the two groups.

CONCLUSIONS

Experimental SVC obstruction during CPB may reduce the CPP, resulting in impaired cerebral perfusion. Both vasopressor treatment and improved venous drainage can, in the short term, individually restore the CPP during these circumstances.