Each day, thousands of people worldwide have heart surgery. Surgeries may be used to repair or replace the valves that control blood flow through the heart’s chambers, bypass or widen the blocked or narrowed arteries to the heart, repair aneurysms, or bulges in the aorta, destroy small amounts of tissue that disturb electrical flow through the heart, implant devices to regulate heart rhythms, make channels in the heart muscle to allow blood from heart chamber directly into the heart muscle, boost the heart’s pumping power with muscles taken from the back or abdomen, and replace the damaged heart with a heart from a donor. When heart cells become damaged, they release different enzymes and other molecules into the bloodstream. Elevated levels of such markers of heart damage in the blood or urine may help predict a heart attack in patients with severe chest pain, and help determine treatment.
Testing for these markers soon after the surgery could help doctors protect the health of patients’ kidneys. Blood and urine markers can indicate which patients with an Acute Kidney Injury (AKI), previously known as acute renal failure, following heart surgery will experience progressive kidney problems. High urinary interleukin-18 and the albumin-to-creatinine ratio increases patients’ risk of experiencing persistent AKI by approximately three-fold, while high blood levels of a protein called neutrophil gelatinase-associated lipocalin increases their risk by more than seven-fold. Acute kidney injury (AKI) is the sudden loss of kidney function. It occurs when the kidneys stop working over a period of hours, days, or in some cases, weeks. It’s a sharp increase of the serum creatinine level from baseline (i.e., an increase of at least 0.5 mg/dl) and the urine output is less than 400 ml per day.
Hypotension, or decreased blood pressure, is often seen during and after open heart surgery. This decrease in blood pressure decreases blood flow to the kidneys causing AKI and is one of the most common causes of kidney failure after open heart surgery. During surgery, pieces of plaque buildup, called emboli, can break off and travel to various organs including kidneys causing AKI. Patients with a certain kind of gene complex, called eNOS 786C/T polymorphism are also at an increased risk of developing acute kidney injury after cardiac surgery. With the exclusion of relevant medical conditions, the mortality rate for AKI stands at 10%. In most cases, AKI after heart surgery resolves quickly, but some cases worsen and can seriously affect patients’ health and survival.