胸部外科

Low cardiac syndrome（ LOS） is the imbalance of the oxygen supply and demand at the tissue due to reduced oxygen supply by decreased cardiac function. The causes of the cardiac dysfunction are insufficient cardioplegia, elongation of aortic clamp or cardiopulmonary bypass （CPB） duration, incomplete revascularization, and so on. The preventions of LOS are myocardial protections intraoperatively. The most important myocardial protection is to accomplish more quickly, accurately and safety to operation. And today, cardioplegia is essential for surgery requiring CPB. The integrated myocardia protection is likely to be effective to the patients who suffer low cardiac function. LOS is commonly defined the decreased cardiac index （CI）［＜2.0～2.2 l/min/m2］, systolic blood pressure （＜80～90 mmHg） and the signs of tissue malperfusion, in the absence of hypovolemia. The treatment of LOS is, at first, the correction of hypovolemia, then rhythm control, adjustment of preload and afterload. When it does not recover from LOS despite adequate treatment, the mechanical circulatory assist devices should be introduced without hesitation.

Although short and long-term outcomes of aortic surgeries have been improving over the past decade, the procedure is likely to be asscociated with life-threatening complications such as neurological deficits caused by suboptimal brain protection or heavily diseased aorta. Contemporary strategies for brain protection are deep hypothermic arrest with or without retrograde cerebral perfusion retrograde cerebral perfusion or selective antegrade cerebral perfusion. At the moment, majority of evidences failed to show the superiority of selective antegrade cerebral perfusion to retrograde one. Shaggy aorta（ atherothrombotic aorta） was defined as very extensive atheromatous disease with diffuse ulcers associated with soft, loosely held debris and a paucity of actual thrombus and is the prototypical potential embolic source for neurological deficits. Non-physiological flow during cardiopulmonary bypass causes the detachment of atheroma and consequently the debris was washed away into the carotid arteries. Therefore, meticulous selection of cannulation site and type of cannula （a dispersion cannula） and complete exclusion of the diseased aorta contributed to avoiding permanent neurological deficits even when atherothrombotic aorta was present. Shaggy aorta combined with leukoaraiosis, extracranial carotid artery stenosis, and prolonged cardiopulmonary bypass time exponentially increased postoperative transient neurological deficits in patients undergoing total aortic arch replacement, and may therefore deserve special attention.

Cerebrovascular complication is the one of the most dreadful complication after open heart surgery which leads to significant decrease of quality of life even if the patients survived. To decrease these complications, carotid doppler echo as one of the non-invasive carotid screening modalities is effective. Carotid artery stenosis is common in the patients with coronary artery disease, and it is more frequent in the patients with more complexed coronary artery lesions. The more the patients indicated for coronary artery bypass grafting has complexed lesions these days, the more the patients have carotid artery lesions. In case of presence of significant carotid artery stenosis with symptom, carotid artery intervention, either carotid endarterectomy or carotid artery stenting, should be considered by multidisciplinary team. The carotid artery stenosis could cause cerebral infarction by 2 major mechanisms, which are emboli, and low perfusion pressure. In open heart surgery, it is very important to avoid these occasions. Although It is still controversial whether off-pump coronary artery bypass grafting is superior to conventional on-pump coronary artery bypass grafting in randomized trial, it is necessary in common to avoid atheromatous emboli from aorta and to avoid low perfusion pressure by all means.

Chronic kidney disease（CKD） is an important risk factor of open heart surgery. In addition, worsening of kidney function after the surgery leads to poor prognosis long-term. It is therefore crucial to protect the kidney function by intensive perioperative management in open heart surgery. In the patients having stage 3-4 CKD, mean arterial pressure needs to be higher than 70 mmHg and cardiac index needs to be greater than 2.4 intraoperatively and postoperatively. Continuous right heart monitoring by Swan-Ganz catheter is useful for this purpose. In the patients having stage 5 CKD, systemic complications need to be thoroughly evaluated preoperatively. Hemodialysis and serum potassium control during the extracorporeal circulation is important to minimize delay of postoperatively recovery. For coronary artery bypass grafting, off-pump approach would be a good option in stage 3-4 and stage 5 CKD patients.

The number of cardiovascular surgical operations has been increasing, accompanied by an increase in the number of patients with an aging patient and various comorbidities. For this reason, the risk of respiratory complications after cardiovascular surgery is high, and ingenuity to alleviate this is necessary. We evaluated preoperative respiratory function and examined whether there is a difference in the onset of postoperative respiratory complications with or without respiratory rehabilitation from preoperative. As a result, the incidence of respiratory complications was significantly reduced in the group subjected to preoperative respiratory rehabilitation. Also, the intensive care unit stay was significantly shortened. From this, it is important to perform respiratory rehabilitation from preoperative time. And as a breathing exercise method, active cycle breathing technique is safe and highly effective.

Liver cirrhosis has emerged as a serious risk factor for cardiac surgery due to the higher mortality and morbidity that these patients display compared with the non-cirrhotic cardiac surgery population. Child-Pugh classification and model for end-stage liver disease score（ MELD） score are useful to assess perioperative risk in patients with cirrhosis. According to recent research, cardiac surgery could be offered to patients with Child-Pugh A and a low MELD score with only mild increase in the risk of mortality. However, for patients with more advanced cirrhosis, risk of mortality is extremely high. To decrease mortality, careful patient selection, meticulous consideration of surgical strategy and perioperative treatment are vital for the recovery of cirrhotic patients.

Mediastinitis after cardiac surgery occurs about 1％ of the time and is associated with adverse effects on both short- and long-term outcomes. Therefore, prevention of mediastinitis is very important. However, when this complication occurs, a radical cure should be performed using a safe and reliable method. Many pre-， intra-， and post-operative risk factors have been reported. Perioperative management based on an understanding of the pathological condition that causes this complication is an effective prevention strategy. Early detection and treatment are most important, and there should be close coordination with plastic surgeons. Recently, negative pressure wound therapy has been used widely and appears to be effective for this complication.

Acute mesenteric ischemia as malperfusion syndrome associated with acute aortic dissection is a difficult situation. The incidence is approximately 3～4％ in acute type A dissection. Traditionally, most of these patients underwent immediate simple central aortic repair expecting that mesenteric artery obstruction and intestinal ischemia would be resolved by simple central aortic repair. However, short term mortality has been reported very high in this strategy. With the aid of rapidly progressing imaging techniques and newer endovascular repair techniques, results seem to be improving in recent years. Newer management strategy include aggressive and patient specific revascularization to the mesenteric arteries, delayed central aortic repair, and meticulous intensive care. Diagnosis and management of this condition require high level of expertise. Cardiac surgeons, vascular surgeons, interventional radiologists, gastroenterologists, general surgeons, anesthesiologists, intensivists must corporate to save these patients’ lives. Since this is a relatively rare condition, scientific evidence is insufficient to make robust recommendations. Further studies are warranted.

Legs ischemia might be associated with acute aortic dissection, in acute phase or even in subacute phase. In general, immediate central repair for acute aortic dissection is mandatory prior to intervention of leg ischemia because central repair might improve leg ischemia. Depending on condition of leg ischemia, revascularization of occluded artery should be considered. The perfusion to ischemic leg during central repair is useful to diminish leg injury. There are some useful modalities for revascularization such as some route of extra-anatomical bypass, placing of stent graft for closing entry site of dissected aortic wall. Multiple organs injury are occurred simultaneously by occlusion of organ branches on aortic dissection. Leg ischemia is associated frequently with other organs ischemia, and could be a pilot sign for abdominal organ ischemia.