Discussions
With the update and progress of cardiac surgery technology, OPCABG has been more and more favored by cardiac surgeons. Although the debating of OPCABG and CABG remained, OPCABG has similar survival rate comparing with CABG presently, and it shows great advantages for some older and severe patients1,2,36-39.
Since OPCABG does not require CPB, related complications such as inflammation and blood cell destruction caused by CPB are avoided. Additionally, in OPCABG surgeons performs coronary artery anastomosis on a beating heart which requires very high surgical skills, and which also poses greater challenges to the cooperation of anesthesiologists whose intraoperative monitoring is vital. Anesthesia for cardiac surgery is more challenging while OPCABG requires much higher for anesthesia. Anesthesiologists must always monitor the vital signs of patients, monitor hemodynamic changes, and cooperate with surgeons’ operations at all times intraoperatively. Although diverse anaesthetic and sedative analgesics have been used since modern times, intraoperative complications are still inevitable40-42.
Delirium is one of the common complications following cardiac surgery. On account of sedation and mechanical ventilation are routinely required after cardiac surgery, and most patients need vasoactive drugs to stabilize vital signs, therefore the occurrence of delirium has threatened the safety of patient postoperatively6,43-46. Delirious patients often remove intubation and infusion tubes from the body, which seriously threatens the safety of patients’ lives. For the occurrence of postoperative delirium, current research has confirmed many factors including major bleeding during surgery, hemodynamic instability, and the patient’s history of cerebrovascular disease47-51. However, there is still a lack of a systematic and effective prediction system, thence it is of great significance to explore and study the prediction scoring system for delirium following OPCABG.
The SAS score was mean to be used to assess the prediction of serious complications after general and vascular surgery which includes EBL, LMAP and LHR during anesthesia and shows a good predictive effect. Several research groups noted that the SAS could accurately predict postoperative complications in surgical subspecialties including neurosurgery and esophagectomy16,52-54. In another report, stabilizing the vital signs during surgery improved the surgical outcomes in major surgeries. However, whether SAS score has similar predictive effect on the occurrence of delirium following OPCABG, there are few studies at present. Therefore, we though to explore whether the SAS intraoperative score has a good predictive effect on patients following OPCABG.
In the present study, we included patients who underwent OPCABG surgery. The SAS score was calculated by monitoring the patient’s anesthesia data during the surgery. The incidence of postoperative delirium was observed through the ICU trained nurses47,55,56. Through statistical analysis, we found that low SAS score is an independent risk factor for delirium in OPCABG patients, with EBL and LMAP within the three factors are the main influencing factors. In the prediction model, we found that SAS has a high sensitivity and specificity for predicting the occurrence of postoperative delirium, which has a good warning effect on the prevention of high-risk patients after surgery. In addition, we stratified according to the level of SAS, and found that patients with a low score of 4 have a significantly increased incidence of postoperative delirium, which also provides a good significance for the postoperative monitoring of patients16,25,29,57. We thought that because most patients receiving OPCABG have severe coronary calcification, and the vascular elasticity is significantly reduced. Surgical manipulation on beating heart have a greater impact on hemodynamics, usually causing blood pressure fluctuation drastically, and minimum blood pressure may occur between 30-50mmHg. Consequently, the occurrence of hypotension during OPCABG surgery significantly reduced the SAS score16,58-60. In addition, although OPCABG does not require CPB, compared with other general surgery, intraoperative blood loss also increased as a result of greater trauma and heparinization. As for changes in heart rate, patients on OPCABG had tachycardia occurred much more than bradycardia because stimulating to the heart. Wherefore, the SAS score during the operation reduced significantly during surgery which can be used to predict postoperative complications such as delirium.
In conclusion, in this retrospective study, we found that for patients underwent OPCABG, the intraoperative SAS score has a useful predictive effect on the occurrence of delirium postoperatively and which shows great correlation with delirium. The main limitation of this study is its retrospective designing and lack of high level of evidence. Secondly, we did not calculate the effect of intraoperative anesthetic and postoperative sedation in this study, and a larger sample size study is expected to draw more persuading conclusions.