Comparison between transcranial Doppler and Coulter counter for detection of lipid micro embolization from mediastinal shed blood reinfusion during cardiac surgery.

INTRODUCTION: Lipid micro embolization (LME) from re-transfused shed blood has been postulated to be a potential reason for short- and long-term cognitive dysfunction after cardiac surgery. The purpose of this investigation was to evaluate if transcranial Doppler (TCD) has the capacity to detect LME. METHODS: Thirteen patients undergoing cardiopulmonary bypass surgery were investigated. Each patient's cerebral circulation was monitored with transcranial Doppler during the first two minutes after re-transfusion of shed blood and blood was simultaneously sampled and characterised by a Coulter counter. RESULTS: Strong correlation was found between embolic loads, as measured by transcranial Doppler and Coulter counter (r=0.79, P<0.005). CONCLUSIONS: This pilot study shows that non-invasive monitoring by transcranial Doppler could be a potential tool to monitor LME during cardiopulmonary bypass surgery.

Blood transfusion after cardiac surgery: is it the patient or the transfusion that carries the risk?

BACKGROUND: The transfusion of red blood cells (RBCs) after cardiac surgery has been associated with increased long-term mortality. This study reexamines this hypothesis by including pre-operative hemoglobin (Hb) levels and renal function in the analysis. METHODS: A retrospective single-center study was performed including 5261 coronary artery bypass grafting (CABG) patients in a Cox proportional hazard survival analysis. Patients with more than eight RBC transfusions, early death (7 days), and emergent cases were excluded. Patients were followed for 7.5 years. Previously known risk factors were entered into the analysis together with pre-operative Hb and estimated glomerular filtration rate (eGFR). In addition, subgroups were formed based on the patients' pre-operative renal function and Hb levels. RESULTS: When classical risk factors were entered into the analysis, transfusion of RBCs was associated with reduced long-term survival. When pre-operative eGFR and Hb was entered into the analysis, however, transfusion of RBCs did not affect survival significantly. In the subgroups, transfusion of RBCs did not have any effect on long-term survival. CONCLUSIONS: When pre-operative Hb levels and renal function are taken into account, moderate transfusions of RBC after CABG surgery do not seem to be associated with reduced long-term survival.

Evaluation of cystatin C with iohexol clearance in cardiac surgery.

BACKGROUND: Post-operative renal dysfunction after cardiac surgery is not uncommon and can lead to adverse outcome. The ability to accurately monitor renal function is therefore important. Cystatin C is known to be a sensitive marker of the glomerular filtration rate (GFR), but it has not been fully evaluated in cardiac surgery. Iohexol clearance is considered a reliable reference method for the determination of GFR. The aim of this study is to, for the first time, evaluate the diagnostic accuracy of plasma cystatin C compared with iohexol clearance in cardiac surgery. METHODS: Twenty-one patients scheduled for elective coronary artery bypass grafting were prospectively enrolled in the study. Before surgery and on the second post-operative day, an iohexol clearance was performed. Plasma cystatin C, plasma creatinine and plasma C-reactive protein were determined before surgery and on the first, second, third and fifth post-operative day. Estimated creatinine and cystatin C clearances were determined. RESULTS: Post-operative cystatin C and 1/cystatin C correlated strongly to iohexol clearance (r=-0.90 and 0.86) and so did creatinine and 1/creatinine (r=-0.83 and 0.78). Estimated creatinine clearance differed from iohexol clearance (P<0.01), whereas estimated cystatin C clearance did not differ from iohexol clearance (P=0.81). No correlation was found between C-reactive protein and cystatin C. CONCLUSION: This study indicates that clearance estimations based on cystatin C are more accurate compared with estimations based on creatinine in determining GFR in cardiac surgery. Cystatin C has, in this study population, a stronger correlation to iohexol clearance than creatinine.