Effects of milrinone on jugular bulb oxygen saturation and cerebrovascular carbon dioxide reactivity in patients undergoing coronary artery bypass graft surgery

Abstract

Background. Jugular bulb oxygen saturation (SjvO2) is a surrogate marker for global cerebral oxygenation. The effect of milrinone on SjvO2, and the cerebrovascular carbon dioxide reactivity (CCO2R) was investigated. Methods. Thirty patients scheduled for coronary artery bypass graft surgery (CABG) were studied prospectively. After sternotomy, normoventilation (at T1; PaCO2=4.7-5.0 kPa) and hyperventilation (at T2; PaCO2 =3.3-3.7 kPa) were induced and the changes in SjvO2 (ΔSjvO2) and PaCO2 (ΔPaCO2), and ΔSjvO2/ΔPaCO2 (CCO2R) were measured. After normoventilation was re-established (at T3), milrinone 50 μg kg-1 was given (at T4), followed by hyperventilation (at T5), and ΔSjvO2, ΔPaCO2 and CCO2R were measured. Results. After milrinone administration at normoventilation (T3 and T4), cardiac index and mixed venous oxygen saturation increased, while mean arterial pressure and systemic vascular resistance index decreased, without a significant change in SjvO2. Before milrinone administration (T1 and T2), hyperventilation decreased PaCO2 and SjvO2, and ΔSjvO2 showed positive linear correlation with ΔPaCO2. After milrinone administration (T4 and T5), hyperventilation decreased PaCO2 and SjvO2 and ΔSjvO2 showed positive linear correlation with ΔPaCO2. There was no significant difference in CCO2R before and after milrinone administration (13.3 (5.7)% kPa-1 and 12.3 (3.9)% kPa-1, respectively). Conclusions. Although milrinone induced significant haemodynamic changes, SjvO2 and CCO2R were unchanged during its administration. © The Board of Management and Trustees of the British Journal of Anaethesia 2004.