Influence of Covid-19 disease on hemostasis dynamics during extracorporeal membrane oxygenation (ECMO)1.

INTRODUCTION: COVID-19 causes a considerable degradation of pulmonary function to the point of an acute respiratory distress syndrome (ARDS). Over the course of the disease the gas exchange capability of the lung can get impaired to such an extent that extracorporeal membrane oxygenation (ECMO) is needed as a life-saving intervention. In patients COVID-19 as well as ECMO may cause severe coagulopathies which manifest themselves in micro and macro thrombosis. Previous studies established D-dimers as a marker for critical thrombosis of the ECMO system while on admission increased D-dimers are associated with a higher mortality in COIVD-19 patients. It is therefore crucial to determine if COVID-19 poses an increased risk of early thrombosis of the vital ECMO system. METHODS: 40 patients who required ECMO support were enrolled in a retrospective analysis and assigned into 2 groups. The COVID group consist of 20 COVID-19 patients who required ECMO support (n = 20), whereas 20 ECMO patients without COVID-19 were assigned to the control group. D-dimers, fibrinogen, antithrombin III (AT III), lactate dehydrogenase (LDH) and platelet count were analysed using locally weighted scatterplot smoothing and MANOVAs. RESULTS: The analysis of both groups shows highly significant differences in the dynamics of hemostasis. The increase in D-dimers that is associated with thrombosis of the ECMO systems occurs in COVID-19 patients around 2 days earlier (p = 2,8115 10-11) while fibrinogen is consumed steadily. In the control group fibrinogen levels increase rapidly after ten days with a plateau phase of around five days (p = 1,407 10-3) . Both groups experience a rapid increase in AT III after start of support by ECMO (p = 5,96 10-15). In the COVID group platelet count decreased from 210 giga/l to 130 giga/l within eight days, while in the same time span in the control group platelets decreased from 180 giga/l to 105 giga/l (p = 1,1 10-15). In both groups a marked increase in LDH beyond 5000 U/l occurs (p = 3,0865 10-15). CONCLUSION: The early increase in D-dimers and decrease in fibrinogen suggests that COVID-19 patients bear an increased risk of early thrombosis of the ECMO system compared to other diseases treated with ECMO. Additionally, the control group shows signs of severe inflammation 10 days after the start of ECMO which were absent in COVID-19 patients.

[Awake ECMO therapy in airway stenosis. Bronchoscopic treatment using laser resection]. / Wach-ECMO-Therapie bei Atemwegsstenose. Bronchoskopische Behandlung mithilfe der Laserresektion.

This article presents the case of a 62-year-old patient with cancer in the left upper pulmonary lobe who underwent lobe resection with postoperative respiratory insufficiency. The right upper lobe had already been resected 5 years earlier because of an adenocarcinoma. Prior to the present surgery a computed tomography scan detected a narrow stenosis at the former resection site; however, both pulmonary lobes beyond this stenosis appeared to be sufficiently ventilated. After resection of the left upper lobe attempted extubation was unsuccessful due to insufficient global gas exchange as the stenosis prevented ventilation of the right lung. Bronchoscopy provided evidence of a normal diameter of the bronchus behind the stenosis so both lobes were to be recruited after possible correction of this section. A veno-venous extracorporeal membrane oxygenation device (ECMO) was established as bridging therapy to attain normal gas exchange. As the patient showed no muscle weakness and was cooperative, extubation was performed and spontaneous breathing occurred without any support while still under ECMO treatment. The stenosis was reduced by bronchoscopic laser resection within seven consecutive sessions. Each of these surgeries was conducted with the patient under general anesthesia with oral intubation and jet ventilation in combination with the ECMO. The patient was extubated after each treatment session and weaned from ECMO after the final resection within 2 days. This case demonstrates the use of ECMO in combination with surgical procedures in a spontaneously breathing patient as a causal therapy and option for selected patients to prevent complications from long-term ventilation.

Influence of radiofrequency energy on polypropylene sutures in atrial tissue.

OBJECTIVE: Bipolar radiofrequency (RF) ablation is an established technique for the surgical treatment of atrial fibrillation. To create complete lesion sets, the bipolar device has to be partially inserted into the heart via a purse-string suture, which is subject to heat damage. We investigated the influence of RF ablation on the structure and function of polypropylene sutures. METHODS: Six polypropylene sutures (4/0 Prolene; Ethicon, Norderstedt, Germany) were sutured ex vivo into atrial auricles from excised pig hearts. The tissue was treated by bipolar, saline-irrigated RF ablation (Cardioblate; Medtronic, Duesseldorf, Germany), until increase of tissue impedance pointed out a transmural lesion. After fixation in formaldehyde, the sutures were carefully removed and examined for ultrastructural damage using scanning electron microscopy, comparing them to sutures with intentional damage by instrumental grips. Tensile strength was tested applying a force velocity of 200 mm/min. Here, parts from the ablated zones were compared with parts from nonablated zones of the same suture. RESULTS: We could not find ultrastructural damage in form of heat-induced changes in the helical polypropylene structure. Accordingly, the tensile strength of the ablated sutures (16.5 to 17.5 N) showed no difference to an untreated suture. In contrast, sutures damaged by instruments showed remarkable structural damage and could be torn without force. CONCLUSION: Bipolar, saline-irrigated RF ablation does not damage polypropylene sutures in spite of the heat applied to the tissue. Therefore, it is safe to create bipolar epi/endocardial lesions of the heart through polypropylene purse-string sutures.

Perioperative management in pediatric heart transplantation.

Peri- and early postoperative mortality significantly influences the probability of survival following heart transplantation in children. Main causes of death early after transplantation are rejection, non specific graft failure and RV failure due to pulmonary hypertension. Optimal therapy of pulmonary hypertension and aggressive use of assist devices as a bridge to recovery will substantially improve survival in the early period after transplantation. Furthermore, the use of marginal donor organs will be more acceptable because transient myocardial insufficiency may recover during extracorporeal life support.

Selective Cerebral Perfusion Via Innominate Artery in Aortic Arch Replacement Without Deep Hypothermic Circulatory Arrest.

To attain satisfactory results in aortic arch surgery a reliable method of cerebral protection, avoidance of emboli, and control of hemorrhage is mandatory. Deep hypothermic circulatory arrest is the most common technique at present but gives only a limited period of protection, whereas a complicated aortic arch operation may require more time than anticipated. Therefore the selective cannulation and perfusion of the innominate artery has not been widely used until now because it is uncertain whether the left hemisphere of the brain is adequately perfused. Between 1990 and 1995, 21 of 69 patients within the last 36 months, consisting of 15 men and 6 women averaging 45 +/- 13.4 years, underwent operative treatment for aneurysm (n = 9) or type A dissection (n = 12) involving the aortic valve and aortic arch; selective innominate perfusion (SCP [i]) in moderate hypothermia (28 degreesC) for brain protection was used. Extended perioperative monitoring included bilateral somatosensory-evoked potentials (SEP), transcranial Doppler sonography (TCD), a computer-aided topographical electro-encephalometry (CATEEM), and analysis of the arterial and venous oxygen saturation and desaturation. Mean time periods were 229.7 +/- 56.5 minutes for extracorporeal circulation, 151.7 +/- 34.1 minutes for aortic cross-clamping, and 67.05 +/- 34.03 for selective cerebral perfusion via the innominate artery. Not once did the intraoperative monitoring reveal hints of cerebral damage due to inadequate perfusion. All patients survived surgery but two could not be weaned from the respirator; one died 2 days and the other 6 days after the operation due to multiple organ failure (MOF). Another two patients died after 13 days due to untreatable septic syndrome with pulmonary insufficiency. All four patients died within 30 days, during which time they had aortic dissection involving the complete aortic arch and severe aortic valvular incompetence (grade IV). There was no late death and follow-up time of 19.76 +/- 8.04 months revealed an overall mortality rate of 19%. Only temporary neurological affections (left-sided hemiparesis) were found in two patients (9.5%). Additionally, we observed neuropsychological disturbances in one of these. Our first experience with selective cerebral perfusion via innominate artery and the attendant CATEEM monitoring for assessment of adequate bilateral cerebral perfusion suggests that this method is a useful addition to the armamentarium in complicated aortic arch surgery.

An assessment of selective cerebral perfusion via the innominate artery in aortic arch replacement.

Maintaining an adequate cerebral oxygen supply is a serious problem in aortic arch surgery. Deep hypothermic circulatory arrest is the most common method used for cerebral protection, but guarantees only a time-limited safety period. Based on experimental investigations, we applied selective cerebral perfusion via the innominate artery alone with only moderate hypothermia (28 degrees C) and without circulatory arrest in 25 consecutive patients undergoing surgical treatment of an aneurysm (n = 10) or acute type-A dissection (n = 15) involving the aortic valve and arch. In every case a test perfusion was carried out to assess whether the cerebral perfusion achieved would be adequate for the whole operation. In no case was the perfusion inadequate. As a new perioperative monitoring system, we used computer-aided topographical electroencephalometry (CATEEM). There were 18 male and 7 female patients, their age was 47.0 +/- 15.1 years (mean +/- SD). Mean time periods were 155.1 +/- 37.3 min for aortic cross-clamping, and 69.3 +/- 35 min for selective cerebral perfusion. Postoperatively, two patients (8%) revealed a temporary left-sided hemiparesis, and 4 patients (16%) died within 30 days. The overall mortality rate was 16% in a follow-up period of 24.2 +/- 9.5 months. In this small group the CATEEM monitoring enabled an intraoperative selection of patients with sufficient bihemispheric collateral circulation and therefore suitable for simple innominate artery perfusion.

Potential problems with simplified selective cerebral perfusion--experimental investigations and clinical improvements.

Currently the most used perfusion techniques during aortic arch surgery to prevent cerebral damage include hypothermic circulatory arrest, retrograde cerebral perfusion and selective cerebral perfusion (SCP). The application of simplified SCP, which does not require deep hypothermia, has become an alternative procedure for brain protection. Including the physiological principle of autoregulated cerebral blood flow, cerebral perfusion flow is not predetermined, but differentiated from the different cannula sizes for the lower and upper body perfusion. In a mock circulation loop, we could show that resistance changes in the two compartments led to flow shifts between the systemic and brachiocephalic regions. In addition to mechanical factors cerebral perfusion is determined from physiological changes. In practice, these shifts can be initiated with disrupted autoregulation due to ph-stat management or dramatic pressure changes. To prevent mismatched cerebral perfusion extended perioperative monitoring was included in our clinical setting. With bilateral somatosensory evoked potentials, a computer aided topographical electroencephalometry system, transcranial doppler-sonography and jugular venous bulb saturation, we could provide a sufficient bihemispheric perfusion. Between 1990 and 1995 we operated on 21 patients using SCP. Intraoperatively no signs of cerebral ischaemia due to inadequate perfusion could be observed. Only temporary neurological changes were found postoperatively. In summary, the simplified SCP, despite its physiological basis, is intricately involved in control and influence. We think that the application of SCP is safe if extended neurophysiological monitoring is included in the clinical setting.