Alp Alayunt

Effect of pulsatile flow during cardiopulmonary bypass on thyroid hormone metabolism

Changes in thyroid hormone levels during and after cardiopulmonary bypass (CPB) are well documented. However, little is known about the effects of pulsatile flow during CPB on thyroid hormone metabolism. To examine the effect of flow pattern, a prospective study was carried out using 30 patients undergoing coronary artery bypass grafting. Fifteen patients had pulsatile flow during CPB and 15, nonpulsatile flow. Serum samples were obtained preoperatively, during bypass, and at 2 and 24 hours postoperatively. Thyroid-stimulating hormone, thyroxine (T4), triiodothyronine (T3), free T4, and free T3 levels were measured by radioimmunoassay. All measured hormone levels except free T4 and thyroid-stimulating hormone decreased after the initiation of CPB. There were no differences in preoperative values between the two groups. However, levels of T3 and free T3 during and after CPB showed a significant difference between the two groups, with a smaller decrease in patients in whom pulsatile flow was used during bypass (p < 0.05). Thyroxine, and thyroid-stimulating hormone free T4 values showed no difference between the two groups at any sampling time. These data provide support for the use of pulsatile flow during CPB to establish a more physiologic state and maintain better thyroid hormone metabolism.

Determinants of Early Mortality and Neurological Morbidity in Aortic Operations Performed Under Circulatory Arrest

Abstract Objective: Aneurysms and dissections of the thoracic aorta continue to present a surgical challenge and their incidence is increasing in recent years. The mortality rate of surgical treatment is still higher than those of other cardiovascular operations. Neurological injury is the most feared complication resulting from repair of these lesions. This study aims to determine the factors that influence the neurological outcome and mortality after thoracic aortic operations. Methods: During the period from November 1993 through May 1999, 144 patients were operated on for conditions involving the ascending aorta and/or aortic arch. Ninety‐five (66.0%) were operated for aortic dissection and 49 (34.0%) were for aortic aneurysms. Sixty‐two patients (43.1%) had replacement of ascending aorta with distal open technique; 82 patients (56.9%) had hemiarch or total arch replacement or repair of the distal arch. Results: Twenty‐seven (18.7%) early deaths occurred. New stroke occurred in two patients (1.4%) and temporary neurological dysfunction in nine patients (6.3%). Deep hypothermic circulatory arrest with retrograde cerebral perfusion was used in all patients. On multivariate logistic regression analysis, risk factors for mortality were chronic renal failure, preoperative organ malperfusion, rupture, total circulatory arrest time > 60 minutes, postoperative acute renal failure, postoperative low cardiac output, sepsis, and multiple organ failure. Risk factors for neurological morbidity were preoperative chronic renal failure, preoperative hemodynamic instability, postoperative low cardiac output, and pulmonary complications. Conclusions: Hypothermic circulatory arrest with retrograde cerebral perfusion was not an independent predictor of neurological morbidity on multivariate analysis, even if the arrest period was more than 60 minutes. Lengths of circulatory arrest periods and clinical presentations of the patients are important determinants of mortality.

CONTINUOUS RETROGRADE CEREBRAL PERFUSION SUPPLIES SUBSTRATES FOR BRAIN METABOLISM DURING HYPOTHERMIC CIRCULATORY ARREST

Ten patients underwent replacement of ascending aorta and/or aortic arch with aneurysm or dissection, using hypothermic circulatory arrest (HCA) with retrograde cerebral perfusion (RCP). RCP was administered through the superior vena cava cannula continuously during HCA (15°C to 20°C). Mean HCA time was 32 minutes (range, 18-45 minutes). To assess the metabolic changes during RCP, blood samples were taken from carotid arteries and the superior vena cava cannula simultaneously, five minutes after the onset and five minutes prior to termination of continuous retrograde cerebral perfusion (CRCP) for analysis of blood gas and glucose level. One patient died intraoperatively due to left ventricular failure. Nine patients survived their operations and all except one with stroke due to partial intimal flap obstruction of innominate artery awoke neurologically intact within four to six hours. One patient died on the postoperative fifth day due to septic shock following resection of ischaemic bowel due to dissection involving the mesenteric artery. Oxygen saturation, pH and glucose level were all found to be lower in blood back-bleeding from the carotid arteries than in blood perfused through the superior vena cava cannula at all sampling times during HCA and CRCP (p < 0.05). Although oxygen and glucose extraction is not only from brain tissue, these data demonstrate the efficacy of CRCP in supplying substrates for brain protection. CRCP is a reliable method as an adjunct to HCA for brain protection.

Effect of pleurotomy on blood loss during coronary artery bypass grafting.

Abstract  Background: We conducted a retrospective study to compare two different techniques of internal mammarian artery (IMA) preparation concerning pleurotomy upon the effects of blood loss and pulmonary functions. Methods: Between January 1998 and November 2006, 1357 consecutive patients undergoing coronary artery bypass grafting (CABG) using the left IMA, either alone or in combination with saphenous vein graft, were included in this study. The patients were divided into two groups according to the pleural opening: Group I (n = 1046) patients underwent IMA harvesting with pleurotomy and Group 2 (n = 311) patients with intact pleura. Results: During the study, 27 hospital deaths (1.9%) occurred. The amount of postoperative blood loss and blood transfusion requirements were significantly higher in Group 1 than in Group 2 (p = 0.029 and p = 0.0001). The mechanical ventilation stay was significantly higher in Group 1 than in Group 2 (p = 0.0001). The incidence of left pleural effusion and atelectasis was significantly higher in Group 1 than in Group 2 on day 1 and day 3 after operation. Conclusions: These results demonstrate that preserving pleural integrity has beneficial effects on the postoperative blood loss. Postoperative blood loss and transfusion requirements were higher in patients with pleurotomy. Left pleural effusion, atelectasis, and mechanical ventilatory stay were significantly reduced in patients with preserved pleural integrity.

Techniques for retrograde cerebral perfusion in the treatment of aortic lesions via left thoracotomy.

Abstract Retrograde cerebral perfusion under deep hypothermic circulatory arrest is a simple and useful adjunct in aortic surgery and is performed by many surgeons in the treatment of aortic arch pathology. In recent years, this technique has been recommended in the surgery of distal arch and proximal descending aortic lesions through a left thoracotomy incision. The aim of the technique is to increase the right atrial pressure for retrograde cerebral perfusion. After cooling using femorofemoral bypass, circulatory arrest is initiated. The right atrial pressure is increased to 20 mmHg, and retrograde cerebral circulation results. In this article, five patients with distal aortic arch and proximal descending thoracic aortic lesions who were operated on by using this technique were evaluated. It is suggested that this technique can be used with a lateral thoracotomy approach that is suitable for procedures on a distal aortic arch and proximal descending aorta.