Increase in plasma free haemoglobin during cardiopulmonary bypass in heart valve surgery: assessment of renal dysfunction by RIFLE classification

Abstract

Heart valve surgery carries a high risk of renal insufficiency as an independent risk factor due to prolonged cardiopulmonary bypass. Multiple causes of cardiopulmonary bypass-associated renal damage have been described, and haemoglobin-induced renal injury is presently being investigated. Forty-three patients scheduled for heart valve surgery (mostly combined) were enrolled in the prospective study. Plasma free haemoglobin (PFH) levels were evaluated by photocolorimetric measurement at the start of procedures (t(0)) and before the end of extracorporeal circulation (t(1)). A statistically significant increase in PFH levels during cardiopulmonary bypass was detected [median values (interquartile range) - t(0): 62.0 (53.4) mg/L, t(1): 320.4 (352.2) mg/L], P < 0.001. A significant regression relationship between the duration of cardiopulmonary bypass and the increased PFH was found (Spearman's correlation coefficient 0.628, P < 0.001). In some elderly patients, the tendency towards a high release of PFH during cardiopulmonary bypass was more pronounced, but the overall association between age and PFH levels was of borderline significance (P = 0.077). The correlation between PFH and post-operative serum creatinine was low and non-significant, but the latter correlated highly with the pre-operative serum creatinine values (Spearman's correlation coefficient reached values of 0.6-0.7, P < 0.001). Patients were classified according to the Risk of renal failure, Injury to the kidney, Failure of kidney function, Loss of kidney function and End-stage renal failure (RIFLE) classification for acute renal dysfunction during post-operative days 1 - 4; the influence of PFH levels at t(1) on the consequent RIFLE classification was not proven (P=0.648), but 4 patients in the Injury category had shown a higher median value of PFH (433.6 mg/L) in comparison with the others (29 patients with no acute renal dysfunction - 313.7 mg/L, 10 patients at Risk - 330.1 mg/L).

Acute kidney injury during a pediatric sickle cell vaso-occlusive pain crisis

“…Second, the murine model of SCD has shown that an increase in hemolysis or exposure to excess cell free hemoglobin can also lead to renal injury [27]. While not demonstrated yet in SCD, hemolysis or increases in plasma free heme/hemoglobin in patients undergoing cardiac surgery have been associated with renal injury and AKI [28, 29]. In the setting of a pain crisis, patients with a larger drop in hemoglobin may be subject to a higher risk for kidney injury due to an acute, direct toxic effect of plasma free heme or hemoglobin [30, 31].…”

Urinary Hepcidin-25 and Risk of Acute Kidney Injury Following Cardiopulmonary Bypass

“…More recently, there has been accumulating evidence for the role of labile free iron in potentiating renal IRI in human models of CPB (16,17). Hemolysis is an unavoidable side effect of CPB and the release of plasma free hemoglobin is directly correlated with length of time on CPB (18). In an observational study of thoracoabdominal and thoracic aortic repair, elevated plasma free hemoglobin was independently and significantly associated with renal tubular injury markers (N-acetyl-␤-d-glucosaminidase) as well as clinical AKI (12).…”

Benefits and risks of furosemide in acute kidney injury

“…Recently, sodium bicarbonate has been shown to be useful in preventing AKI after cardiac surgery [68]. It is possible that haemolysis during cardiopulmonary bypass contributes to AKI after cardiac surgery [69], and as such, furosemide may potentially be harmful for on‐pump cardiac surgery by inducing aciduria. It may, therefore, be prudent to monitor the urinary pH and consider concurrent sodium bicarbonate therapy if furosemide is used in patients with rhabdomyolysis or haemolysis.…”