Sublingual microcirculation is impaired during cardiopulmonary bypass in cardiac surgery

Introduction

Cardiac surgery patients are at low risk for postoperative complications, but these may involve multiple organ failure with a high mortality rate. These complications may be related to occurrence of organ ischemia and reperfusion during and just after surgery. We investigated whether microcirculatory flow alterations occur during cardiac surgery.

Methods

We observed 10 consecutive patients who underwent cardiac surgery with cardiopulmonary bypass (CPB). The micro-circulation was studied using sidestream dark field (SDF) imaging. The sublingual capillary flow was estimated using a semi-quantitative microvascular flow index (MFI) in small (diameter 10–25 μm), medium (25–50 μm), and large (50–100 μm) sized microvessels (0 = none, 1 = intermittent, 2 = sluggish, 3 = continuous flow). SDF imaging was performed at least three times per time period (that is, at baseline, after starting CPB and after surgery) in each patient. Data are presented as the median and interquartile range.

Results

The MFI decreased in all sizes of microvessels <15 minutes after starting CPB in comparison with baseline (P < 0.05, Table 1). After starting CPB, the mean arterial pressure (MAP) was lower (61 mmHg (53–65 mmHg)) than at baseline (100 mmHg (92–118 mmHg); P = 0.01). After return to the ICU, the MFI increased (P < 0.05) and returned to baseline values in all microvessels.

Table 1 abstract P264

Conclusion

SDF imaging can be used as a bedside tool to evaluate sublingual microcirculatory changes during cardiac surgery. Despite maintaining common circulatory parameters during CPB, the nonpulsatile status, hypothermia, and the temporary drop in MAP after starting CPB were associated with decreased sublingual MFI, which normalized after surgery. Further studies should reveal whether these changes are related to outcome.