Given its prevalence after cardiac surgery—particularly in patients with chronic renal impairment—finding a way to curb postoperative acute kidney injury (AKI) stands to have a significant effect on patient outcomes. A Japanese research team seems to have taken a step in that direction; their study found that intraoperative administration of haptoglobin was independently associated with lower risk for postoperative AKI in these patients.
“Acute kidney injury occurs in approximately 30% of cardiovascular surgery patients,” said Kenta Kubota, MD, a staff anesthesiologist at Kobe University Hospital in Japan.
“Postoperative AKI in these patients is independently associated with mortality rates, so its prevention is very important. In addition, cardiopulmonary bypass may increase plasma free hemoglobin due to hemolysis,” he continued. “Since plasma free hemoglobin is considered a nephrotoxic agent, haptoglobin may have potential to prevent postoperative AKI in cardiac surgery patients.”
Although haptoglobin is sometimes used to treat hemolysis, few studies have assessed its effect on the incidence of postoperative AKI in these individuals.
Postoperative Incidence About Half
To help fill that void, Dr. Kubota and his colleagues screened the records of 156 patients with chronic renal impairment (creatinine clearance, <60 mL/min) in this retrospective, observational study; all patients underwent cardiac surgery requiring cardiopulmonary bypass. Patients who had undergone preoperative renal replacement therapy were excluded. The incidence of postoperative AKI was assessed within 72 hours of the operation.
As Dr. Kubota reported at the 2015 annual meeting of the American Society of Anesthesiologists (abstract A2106), the overall incidence of postoperative AKI was 48.7% in the cohort (76/156). A total of 41 patients received intraoperative haptoglobin; 115 did not. The incidence of postoperative AKI was 34.1% in patients with haptoglobin, significantly lower than the 53.9% in those who did not receive the agent (odds ratio [OR], 0.44; P=0.046).
Even after adjusting for a host of relevant confounders, the administration of haptoglobin was independently significantly associated with a decreased risk for postoperative AKI (adjusted OR, 0.40; P=0.04; Table). Male gender was the only other independent predictor to be significantly associated with increased risk for postoperative AKI.
“Maximum serum creatinine level was also found to be significantly lower in haptoglobin patients, by a factor of 1.5,” he said.
“So in conclusion, preoperative haptoglobin administration was significantly related to decreased maximum serum creatinine level and lower incidence of postoperative AKI in cardiovascular surgery,” Dr. Kubota summed up. “We are conducting a prospective study about this, and would like to more deeply investigate haptoglobin and its functions.”
Table. Association of Confounders With Postoperative AKI
Adjusted Odds Ratio P Value
Intraoperative haptoglobin 0.4 (0.17-0.96) 0.04
Sex (male) 2.34 (1.04-5.23) 0.04
Aortic operation 1.99 (0.51-7.79) 0.32
CAB operation 1.3 (0.55-3.03) 0.55
Valve operation 0.73 (0.18-2.95) 0.66
EuroSCORE 2 0.98 (0.85-1.12) 0.73
AKI, acute kidney injury; CAB, coronary artery bypass; EuroSCORE, European System for Cardiac Operative Risk Evaluation
Andrew Shaw, MB, FRCA, FFICM, FCCM, professor and vice chair for clinical affairs at Vanderbilt University School of Medicine, in Nashville, Tenn., noted that AKI after cardiac surgery is common, but usually mild. “Despite this, it still leads to significant clinical problems during the recovery phase of the surgery and is associated with increased hospital length of stay, reduced long-term kidney function and reduced mid- to long-term survival,” Dr. Shaw said.
He found the current study exciting, because it suggests there may be a modifiable risk factor—increased plasma free hemoglobin—that can be reduced by giving haptoglobin during surgery. “We usually think of haptoglobin as a test rather than a treatment, but if these data can be reproduced in double-blind, randomized controlled trials, then its use as a therapeutic would certainly be an innovative advance in the field,” Dr. Shaw added.