Assessment of postoperative atrial fibrillation development in patients undergoing thoracotomy

Introduction: Atrial Fibrillation (AF) is one of the commonly observed cardiac arrhythmias following thoracic surgery. The development of postoperative cardiac arrhythmia increases morbidity, mortality, length of hospital stay and healthcare costs. Stroke, thromboembolic event and pulmonary complications may occur due to the development of postoperative AF (POAF). Moreover, hemodynamic instability induced by perioperative AF and impaired tissue perfusion can lead to adverse surgical outcomes. The risk of developing POAF varies approximately between 20-40% after cardiac surgery and 10-20% after non-cardiac surgery, depending on the type of surgery undergone. Patient-related risk factors for POAF include age (>50 years), gender (male), smoking and alcohol use, heart failure, history of previous AF episodes, and comorbidities such as hypertension and COPD. Surgical-related risk factors for AF development include open surgery using the thoracotomy method, intraoperative use of vasoactive-inotropic agents and steroids, transfusion of colloid fluid and erythrocyte suspension intraoperatively, and maintaining positive fluid balance. Choosing thoracic epidural anesthesia as the anesthesia method is also a surgical-related risk factor for AF development. The aim of our study is to identify factors leading to the development of atrial fibrillation and/or arrhythmia in patients undergoing thoracotomy in the postoperative period, to closely monitor hemodynamic and respiratory parameters during intraoperative and postoperative periods, and to investigate risk factors through the measurement of biomarkers such as BNP, CRP, and NLR that predispose susceptibility. Materials and Methods: Our study was conducted at the Department of Anesthesiology and Reanimation, Faculty of Medicine, Akdeniz University Hospital, between June 2022 and June 2023. The study included 172 patients aged between 40 and 79 years, with an American Society of Anesthesiologists (ASA) score of 1-4, who underwent elective thoracotomy and Video-Assisted Thoracoscopic Surgery (VATS) in the thoracic surgery department. Prior to the operation, routine preoperative evaluations were performed, including inquiries about the patients' age, gender, height, weight, comorbidities, medications, smoking, and alcohol consumption. Additionally, ASA classification, preoperative respiratory function tests, preoperative hemogram values, NT-proBNP, CRP, troponin T, and magnesium levels were recorded. Hemodynamic data, blood gas parameters, and laboratory values were recorded in all patients before anesthesia induction, upon transitioning to single lung ventilation, at 30 minutes and 1 hour after single lung ventilation, upon transitioning to double lung ventilation, at 30 minutes after double lung ventilation, and at the end of the operation. Blood gas monitoring was performed after extubation and at 24th hour postoperatively. Hemogram, NT-proBNP, CRP, troponin T, and magnesium values were recorded at 24th hour postoperatively. Postoperative respiratory function tests were conducted using a handheld spirometer (Firstmed SP-10 spirometer). Postoperative fever was recorded, and electrocardiograms were performed in the first 5 days postoperatively. The amount, duration, and dose of inotropic support administered to patients postoperatively were recorded for those requiring inotropic support. For patients requiring blood product transfusion, the type and quantity of product transfused were recorded. Patients developing postoperative arrhythmias were evaluated, and medical treatment or cardioversion was administered to those requiring treatment. Treatment responses were recorded. Statistical analyses of the data obtained in the study were performed using SAS 9.4 software. For statistical significance, the p value was determined to be less than 0.05 throughout the study. Results: Postoperative arrhythmia developed in 32 cases. Among these 32 cases, 18 had POAF, 5 had Ventricular Extrasystole (VES), 3 had right bundle branch block (RBBB), 3 had premature atrial contraction, 2 had QT prolongation, and 1 had Premature Ventricular Complex (PVC). When cases were analyzed according to the surgical type and the extent of resection, the rate of POAF was significantly higher in cases undergoing pneumonectomy. The duration of smoking in the cases with arrhythmia was found to be significantly longer compared to non-arrhythmic cases (p=0.0178). Comparing intraoperative blood transfusion, it was observed that the amount of transfusion was highest in cases where other arrhythmias developed, while it was lowest in the non-arrhythmic group, with a significant difference between the groups (p=0.0385). Systolic blood pressure (p=0.0005) and mean arterial pressure (p=0.0483) were found to be significantly lower in the POAF group at all times, while heart rate was found to be significantly higher in the POAF group (p<0.0001). Significant differences were observed in PaO2 and SaO2 values in preoperative arterial blood gas analysis, with lower values found in the POAF group (p=0.0152, p=0.0168). Lactate levels were significantly higher in the POAF group in arterial blood gas analysis obtained postoperatively and at 24th hour postoperatively (p=0.0290, p=0.0174). Comparing results of respiratory function tests, preoperative FEV1 percentage was lowest in the POAF group (72.8%) and highest in the non-arrhythmic group (85.3%), with a significant difference between the groups (p=0.0453). Postoperative FEV1 percentage decreased in all groups compared to preoperative values, with the non-arrhythmic group having the highest percentage (51.2%), while the POAF (45%) and other arrhythmias group (37.2%) had lower and significant differences. No significant difference was observed in preoperative FEV1/FVC ratio among groups, but in the postoperative period, this ratio was significantly lower in the group with other arrhythmias (p=0.0245). Nt-proBNP values were lowest in the non-arrhythmic group both preoperatively and postoperatively, while they were highest in the group with arrhythmia (p=0.0123, p=0.0365). Preoperative CRP values were significantly higher in the group with other arrhythmias (p=0.0144), while postoperative 24th hour CRP values were highest in the POAF group (p=0.0258). Comparing NLR values at postoperative 24th hour, it was found to be lower in the non-arrhythmic group while showing a significant increase in the arrhythmia groups (p=0.0069). Conclusion: We found that smoking history and duration, extent of pulmonary resection, intraoperative blood transfusion, preoperative low PaO2 and SaO2 values, preoperative high heart rate, and preoperative low FEV1% values were significantly associated with the development of POAF. These findings are consistent with similar studies in the literature. We also observed that postoperative levels of lactate, NLR, Nt-proBNP and CRP were higher in patients developing POAF, which is consistent with findings in the literature. We observed that meticulous preoperative preparation, especially in patients undergoing major thoracic surgery, is effective in identifying known risk factors and closely monitoring hemodynamic and respiratory parameters during the perioperative period, leading to early diagnosis and prevention of POAF. With these findings, we believe that hospital stays and costs related to the frequency of POAF and potential complications can decrease, as suggested in the literature. We also believe that larger case series studies will further support this. Keywords: Postoperative Atrial Fibrillation, POAF, Thoracotomy, NLR, Nt-proBNP, CRP