Cardiovascular Complications Following Thoracic Anesthesia:Incidence, Risk Factors, and Prevention

Abstract

Thoracic anesthesia covers anesthesia involving various types of diagnostic and therapeutic procedures for airways, intrathoracic structures, and lung parenchyma. Common indications for thoracic surgery are malignancies, esophageal diseases, mediastinal diseases, and thoracic injuries. Majority of thoracic patients have smoking exposures, pre-existing respiratory diseases, coronary artery diseases, and other co-morbidities. Therefore, an appropriate preoperative assessment and management for thoracic patients usually involves good communication among anesthesiologists, medical specialists, and thoracic surgeons. To facilitate surgical exposures during thoracic surgery, anesthetic techniques require special devices such as double-lumen endotracheal tube (DLT) for providing lung separation and one-lung ventilation. The placement of DLT can stimulate significant hemodynamic responses such as hypertension, tachycardia, and cardiac arrhythmias due to the larger size and greater degree of carinal stimulation compared to conventional endotracheal intubation. An increase in hemodynamic responses can be harmful to some groups of patients such as elderly, hypertensive patients or patients with coronary artery diseases. Furthermore, thoracic surgery can increase significant postoperative complications and increased mortality rate. Pulmonary complications and cardiovascular complications are two common complications following thoracic surgery. The incidence and risk factors of cardiovascular complications have been previously less explored than those of pulmonary complications. Furthermore, patients with lung cancer were majority of population in most previous studies conducted in developed countries. However those with non-cancer lesions are more common in most developing countries. There are differences in pathophysiology of diseases, unique characteristics of individual patients, and risk for specific types of surgeries. Therefore, studies about the incidence and risk factors of cardiovascular complications for both groups of patients should be determined separately. Previous studies found that risk factors of cardiovascular complications after thoracic surgery were elderly patients, American Society of Anesthesiologists (ASA) classification 3 and 4, male patients, comorbid diseases, long duration of surgery, and patients with positive fluid balance. However, there are still inconclusive results about an association between positive fluid balance (PFB) and perioperative cardiovascular complications after thoracic surgery. Studies in this thesis were conducted to investigate the incidence and risk factors of cardiovascular complications for patients undergoing thoracic surgery for non-cancer lesions at Chiang Mai University Hospital (Maharaj Nakorn Chiang Mai Hospital). This study also explored an effect of positive fluid balance on the incidence of cardiovascular complications for non-cancer patients undergoing thoracotomy. In addition, the study determined an effect of 0.7 µg/kg dexmedetomidine on the hemodynamic responses to DLT intubation compared to placebo and the adverse effects of dexmedetomidine. The study found that the incidence of cardiovascular complications was 6.7% and age > 55 years, diabetes mellitus, coronary artery diseases, duration of surgery > 180 minutes, intraoperative hypotension, and perioperative PFB > 2,000 ml were significant risk factors of cardiovascular complications after thoracic surgery. Thoracic patients with cardiovascular complications had higher significant incidences of intensive care unit admission rate and prolonged hospital stays than those without cardiovascular complications. After exploration of the relationship between patients with positive fluid balance and cardiovascular complications, we found that the incidence of cardiovascular complications after thoracotomy was 8.1% and patients with PEB > 2,000 ml remained the independent risk factor after adjusting for potential confounding variables. Common causes of patients receiving higher PFB were massive hemorrhage and hypotension without significant hemorrhage. Furthermore, our result demonstrated that intravenous dexmedetomidine could attenuate hemodynamic responses to DLT intubation without producing significant serious adverse effects. The mean differences of systolic blood pressure, diastolic blood pressure, mean arterial pressure, and heart rate were significantly higher in the control group before intubation, during intubation, and from 1 to 10 minutes after intubation after being adjusted for all potential variables (age, gender, ASA, concurrent disease, baseline hemodynamic values, intubation time and attempts). In conclusion, the incidences of cardiovascular complications follow thoracic surgery for non-cancer lesions were 6.7% and 8.1%, which were comparable to those of previous studies. Knowledge of incidence and risk factors of cardiovascular complications can help all surgical personnel including anesthesiologists, surgeons, and medical personnel identify high risk patients and provide preventive strategies in order to adjust modifiable risk factors, reduce incidence and severity of complications, and improve quality of anesthesia and surgical safety. We found that PFB > 2,000 ml was a significant risk factor for cardiovascular complications. Therefore, fluid administration should be optimized by using of appropriate hemodynamic monitoring particularly in high risk patients. The use of 0.7 µg/kg dexmedetomidine could attenuate hemodynamic responses to DLT intubation and this could be useful for patients with high risk for cardiovascular complications such as patients with coronary artery diseases or cerebrovascular accident.