OPCABG surgery is an important therapy to treat CAD, as OPCABG surgery may improve long-term outcomes by reducing the rates of perioperative myocardial injury, stroke, and cardiac-related mortality, more and more patients receive this therapy3. However, OPCABG surgery is also known to cause a number of complications, including fluid, electrolyte, and acid-based imbalances3. The changes of these internal environment could cause DI which is a condition that the kidney are unable to conserve water4. DI is either due to deficient secretion of arginine vasopressin (AVP/ADH) (central) or to tubular unresponsiveness (nephrogenic). It has a high mortality and carries severe morbidity. DI after OPCABG surgery can lead to increased medication requirements. Predicting which patients are at high risks for developing DI can help direct services to ensure adequate care and follow-up.
The objective of this study was to retrospectively review our institution’s data on patients undergoing OPCABG surgery and determine which clinical/laboratory variables are associated with DI in this patient population.
In our study, the occurrence of DI in the patients underwent OPCABG was very common, the percentage of patients suffered from DI perioperatively was 43.2%, the percentage of DI intraoperatively and postoperatively was 87.9% and 62.8%.
DI morbidity and mortality is mostly dependent on the electrolyte imbalance it produces, osmotic disturbances, acid base changes and the effect that has on end organ function. As it has shown in our results, the DI(+) group had a higher imbalanced postoperative PH condition than DI(-) group. We highly considered that the occurrence of DI was central DI due to the touch to aortic arch and left atrium of the heart and stimulating to the osmotic pressure receptor. Although the creatinine concentration was higher in the DI (-) group, both the concentration of these two group were in normal condition. After the occurrence of DI, fluid imbalance was further aggravated in patients with a low BMI compared to those with a high BMI5. In our study, there was significant difference between BMI in these two group (DI (-) vs. DI (+), 26.99 + 3.46 vs. 24.76 + 2.94).
DI is caused by insufficient production and secretion of antidiuretic hormone (ADH), or the inability of the kidney tubules to respond to ADH. ADH is a key factor to adjust kidney to conserve water. Secretion of ADH is primarily regulated by plasma osmolarity, but other factors such as left atrial distention, circulating blood volume, exercise, and certain emotional states can also alter ADH releasing6.
The release of ADH directly acts on the kidney. Non-osmotic stimulus of ADH releasing is mediated through volume receptors located in the left atrium of the heart, aortic arch, and carotid artery. Osmotic stimulus of ADH release is mediated through osmoreceptors in the hypothalamus7. What’s more, ADH were found to deficiency developed in patients undergoing aortocoronary bypass operations in some studies8, 9
The reason of DI in patients undergoing OPCABG may associated with both non-osmotic and osmotic stimulus of ADH. For non-osmotic of ADH, the operative procedures of OPCABG including changing the position of the heart always lead to touch to aortic arch and left atrium of the heart. For osmotic stimulus, Cerebral hypoperfusion can occur from intraoperative hypotension and declined cardiac output, Embolic strokes associated with the operation are predominantly attributable to thromboembolism and aeroembolism, these factors may restrict the function of hypothalamus10.
For CAD patients underwent OPCABG surgery, the use of propofol and fentanyl can influence blood pressure, and the operator's operation on the heart also aggravates the difficulty of hemodynamic maintenance. The use of noradrenaline is very common in OPCABG surgery to maintain blood pressure. Adrenal hormone inhibits the synthesis and secretion of AVP, thus adrenal insufficiency can result in increased levels of AVP, which are then lowered following initiation of glucocorticoid replacement.
There were several limitations to this study. This was a retrospective study that needs independent validation. Patients evaluated here underwent OPCABG surgery by different operator and anesthetist, it is hard to avoid the influence caused by the operator and anesthetist. The use of drugs during perioperative period was not recorded very accuracy, there may be some factors of drugs associated with DI.
The occurrence of DI in patients undergoing OPCABG surgery is very common, prospective studies are needed to validate these findings and we need to focus more on this point.