Patient-Specific Susceptibility to the Nadir Oxygen Delivery on Cardiopulmonary Bypass

Maintaining a nadir oxygen delivery ≥ 280 mL/min/m2 during cardiopulmonary bypass is a pillar of the goal-directed perfusion strategy in cardiac surgery. However, there are patients who develop a cardiac surgery associated acute kidney injury despite an adequate oxygen delivery and others who do not develop an acute kidney injury despite a low oxygen delivery. The present study aims to determine the independent factors associated with these 2 conditions.

Post-hoc analysis of 2 previously published series.

The population size was 1030 patients. Inability to maintain the target oxygen delivery was found in 35% of the patients, and the independent determinants were female gender, low creatinine clearance, low preoperative haematocrit, and non-elective surgery. Acute kidney injury was found in 18.3% of the total patient population. Within the patients with a nadir oxygen delivery < 280 mL/min/m2, 73% did not develop an acute kidney injury. These patients were younger, with a lower baseline serum creatinine, shorter cardiopulmonary bypass, and lower peak lactate. Within the patients with a nadir oxygen delivery ≥ 280 mL/min/m2, 13% developed an acute kidney injury: these patients were older, with a lower baseline haematocrit and longer cardiopulmonary bypass.

Preoperative anaemia is the main determinant of a failing goal-directed perfusion. In younger patients at short cardiopulmonary bypass may be possible to reduce the target oxygen delivery. Acute kidney injury in patients with a nadir oxygen delivery ≥ 280 mL/min/m2 is a relatively rare condition whose mechanisms remain to be elucidated.