Post-op renal dysfunction identified, mitigated
Myocardial revascularization often leads to kidney problems or failure, resulting in prolonged ICU and hospital stays, high death rates, and the need for specialized long-term care. Based on the 600,000 bypass procedures performed annually worldwide, about 46,000 patients can be expected to develop renal dysfunction. The effect can be an increased ICU stay by more than 200,000 days and total hospital stay of twice that, increasing costs by hundreds of millions.
In a study reported in the Annals of Internal Medicine, investigators studied patients who underwent revascularization with bypass and looked at the incidence and characteristics of post-op renal dysfunction and failure.1 Researchers wanted to determine their predictors and effect upon in-hospital resource utilization and patient disposition. If high-risk patients can be identified early, they and their physicians can make informed decisions about surgery and point the way to reducing the risk of serious and expensive complications.
Post-op renal dysfunction occurred in 171 of 2,400 study participants; 30 required up to 90 days of dialysis, and 19 patients died. Post-op renal failure was defined by the need for dialysis after surgery. Renal dysfunction was defined by a post-op serum creatinine level of 177 µmol/L or greater and an increase in serum creatinine level of 62 µmol/L or greater from pre-op to maximum post-op values.
The proportion of patients developing dysfunction increased with age, and almost half had a history of unstable angina. A history of Type 1 diabetes, elevated glucose level, congestive heart failure, previous bypass surgery, and pre-op serum creatinine levels of between 124 and 177 µmol/L were associated with a twofold increased risk. The risk increased threefold for those with moderate to severe congestive heart failure.
Prolonged aortic cross-clamp time was found to be an independent risk factor as was total surgery time of more than two hours. A bypass lasting up to three hours was associated with nearly fourfold elevated risk. Patients undergoing concomitant procedures such as valve replacement or carotid surgery doubled their risk.
The report suggests that surgeons consider modifying their techniques by choosing to perform fewer anastomoses or instituting more substantive hypothermic regimens. Anesthesiologists and intensivists should optimize ventricular function, aggressively control serum glucose levels, and closely monitor fluid and renal status.
Therapy with potentially nephrotoxic medications, such as aminoglycoside antibiotics, nonsteroidal anti-inflammatory drugs, or angiotensin- converting enzyme inhibitors before, during, and after surgery in patients with risk factors is dangerous.
The average length of stay in ICUs for patients with dysfunction - with and without dialysis - was twice as long as for patients without. Those requiring dialysis stayed twice as long as those with dysfunction without dialysis and more than five times as long as those without dysfunction.
In-hospital mortality among patients with dysfunction was 27%; 0.9% of patients without dysfunction died. Discharges to extended care, acute care, skilled nursing, or rehabilitation facilities were two to five times more frequent for patients with renal failure.
Reference
1. Mangano CM, Diamondstone LS, Ramsay JG, et al. Renal dysfunction after myocardial revascularization: Risk factors, adverse outcomes, and hospital resource utilization. Ann Intern Med 1998; 128:194-203.
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