Cardiac displacement during off-pump coronary artery bypass grafting surgery: effect on sublingual microcirculation and cerebral oxygenation

Abstract

Cardiac displacement during off-pump coronary artery bypass (OPCAB) surgery causes a fall in cardiac output. Here, we investigate how this drop in systemic perfusion is transferred to the oxygenation of sublingual and cerebral tissue. Sublingual microcirculatory perfusion or microcirculatory hemoglobin oxygen saturation (μHbSO(2)) measurements were performed using sidestream dark-field imaging and reflectance spectrophotometry, respectively (both n = 12). The cerebral tissue oxygenation index was measured by near-infrared spectrophotometry (n = 12). Cardiac output was calculated by pulse contour analysis of arterial pressure. Cardiac displacement reduced the cardiac output from 4.3 ± 0.8 to 1.2 ± 0.3 l/min (P < 0.05), paralleled by a decrease in μHbSO(2) from 64.2 ± 9.1 to 48.6 ± 8.7% (P < 0.01). Cardiac displacement did not change functional capillary density, while red blood cell velocity decreased from 895 ± 209 to 396 ± 178 μm/s (P<0.01). Cerebral tissue oxygenation index decreased from 69.5 ± 4.0 to 57.4 ± 8.5% (P<0.01) during cardiac displacement. After repositioning of the heart, all the values returned to baseline. Our data suggest that systemic hemodynamic alterations during cardiac displacement in OPCAB surgery reduce sublingual and cerebral tissue oxygenation. These findings are particularly important for patients at risk for the consequences of cerebral ischemia.

Changes in Microcirculatory Perfusion and Oxygenation During Cardiac Surgery With or Without Cardiopulmonary Bypass

“…23 Reflectance spectrophotometry measures the mucosal blood oxygenation in the terminal network of the microcirculation, but this technique only scarcely has been described for perioperative sublingual microvascular evaluation. [24][25][26] Alternatively, Fournell et al used gastric reflectance spectrophotometry to measure alterations in microvascular oxygen saturation during CPB. 27 In addition to the local measurement dimensions of reflectance spectrophotometry, NIRS can be used to assess regional tissue oxygenation.…”

“…Indeed, it was earlier shown that off-pump procedures were associated with distinct alterations in microcirculatory function when compared with cardiac surgery with extracorporeal circulation. 24,25 In particular, cardiac displacement during off-pump surgery did not affect capillary density, but resulted in cessation of microcirculatory flow due to a reduced entry of red blood cells into the microvasculature and decreased hemoglobin oxygen saturation in parallel to the sudden decrease in cardiac output as a result of cardiac displacement. 24,25 The results in off-pump patients during cardiac positioning showed that oxygen availability in the sublingual microcirculation was reduced due to the failure of red blood cells entering the capillaries, while the authors observed a redistribution of blood with concomitant hemodilution at the onset of CPB in cardiac surgery.…”

Coronary Artery Bypass Surgery for Patients with Severe Cerebrovascular Atherosclerosis: Importance of Preoperative Assessment and Perioperative Management

“…However, it is known that heart displacement for distal anastomosis can cause significant drops in cardiac performance and cerebral perfusion [18]. Because decreases in cerebral oxygen saturation and hemodynamic parameters during heart displacement were correlated in previous studies [19], we determined the targeted lowest SAP for each grade (raising it accordance with up-grading) in order to maintain cerebral blood flow. It is known that cerebral blood flow is determined by autoregulatory mechanisms between the mean arterial pressures of 50 mmHg and 150 mmHg [20].…”

The case for 0.9% NaCl: is the undefendable, defensible?

“…In experimental studies in rats, we demonstrated in various models of shock and resuscitation that, although fluids were able to correct the global systemic hemodynamics and renal arterial flow to baseline, micro-heterogeneous malperfusion rendered the renal microcirculation hypoxemic, which was associated with raised indicators of renal dysfunction. 69,73 Clinical studies showed that hemodilution is associated with a reduction in functionally filled capillaries resulting in increased diffusion distances 70,74,75 associated with reduced viscosity. Such increased diffusion distances associated with reduced functional capillary density will augment diffusion limitation of oxygen transport and contribute to renal hypoxia.…”