儿童体外膜肺氧合技术应用现状和前景

【摘要】 体外膜肺氧合(ECMO)作为目前最高级的生命支持技术之一，可暂时替代患者心肺功能，为患者器官功能恢复争取宝贵时间。本文就体外膜肺氧合技术在儿科重症中的临床应用作一述评，并分析我国儿童ECMO发展的制约因素，希望中国儿科ECMO技术快速发展，进一步发挥对危重患儿的救治作用。     

Permanent brain arrest as the sole criterion of death in systemic circulatory arrest

Historically, there has been a tendency to think that there are two types of death: circulatory and neurological. Holding onto this tendency is making it harder to navigate emerging resuscitative technologies, such as extracorporeal membrane oxygenation and the recent well-publicised experiment that demonstrated the possibility of restoring cellular function to some brain neurons 4 h after normothermic circulatory arrest (decapitation) in pigs. Attempts have been made to respond to these difficulties by proposing a unified brain-based criterion for human death, which we call ‘permanent brain arrest’. The clinical characteristics of permanent brain arrest are the permanent loss of capacity for consciousness and permanent loss of all brainstem functions, including the capacity to breathe. These losses could arise from a primary brain injury or as a result of systemic circulatory arrest. We argue that permanent brain arrest is the true and sole criterion for the death of human beings and show that this is already implicit in the circulatory-respiratory criterion itself. We argue that accepting the concept of permanent cessation of brain function in patients with systemic permanent circulatory arrest will help us better navigate the medical advances and new technologies of the future whilst continuing to provide sound medical criteria for the determination of death.     

Tracheal intubation

Tracheal intubation is the act of placing a tube into the trachea thus enabling oxygen delivery and carbon dioxide removal. Intubation is the most reliable method of maintaining an airway under anaesthesia, and for protecting against aspiration of stomach contents. Traditionally, intubation is achieved by direct visualization of the glottis, but indirect laryngoscopy (via a videolaryngoscope) has become a common alternative. Prior to embarking upon intubation, a thorough patient history and examination must be undertaken by the laryngoscopist; equipment must be prepared and checked; a trained assistant present; and an experienced anaesthetist available in case assistance is required. Once the endotracheal tube has been placed, correct positioning must be confirmed via both clinical examination and monitoring, which must include capnography. Tracheal intubation is a procedure that should only be undertaken by trained operators and is not without risk. It is important to note that it is failure to oxygenate patients rather than failure to intubate that ultimately leads to serious morbidity and mortality. The Difficult Airway Society has produced guidelines on how to manage unanticipated difficulty in tracheal intubation; it is essential that every practitioner trained to intubate patients is familiar with these algorithms and the key principles of safe airway management.     

Brain tissue oxygenation during transnasal endoscopic skull base procedures

PurposeWe aimed to study brain tissue oxygenation during the period of controlled reduction of arterial blood pressure – a maneuver often used in extended endoscopic skull base surgery for bloodless operative field.MethodsIntracranial pressure, arterial blood pressure and the resultant cerebral perfusion pressure were measured during extended endoscopic skull base surgery in 5 patients with diagnosed tumors of the skull base and arterial hypertension. Simultaneously, in those patients, we measured partial pressure of oxygen in the brain parenchyma (PbtO₂).ResultsValues of PbtO₂ lower than 15 mm Hg (risk of brain ischemia) were observed in 3 patients for periods of 40 min, 110 min and 123 min, respectively. In 2 of these patients, no hypotension (mean arterial pressure <65 mm Hg) was necessary for bloodless operative field. Another 2 patients had PbtO₂ above 30 mm Hg at the time when their mean arterial pressure was below 65 mm Hg. The time course of PbtO₂ followed that of cerebral perfusion pressure with a time lag of 40–60 s in all patients.ConclusionModerate reduction of arterial pressure, often used to obtain bloodless operative field during extended endoscopic skull base surgery, may in patients with the medical history of arterial hypertension be associated with critically low values of partial oxygen pressure in brain tissue.     

Improvements in Extracorporeal Membrane Oxygenation for Primary Graft Failure After Heart Transplant

BackgroundSevere primary graft failure is a life-threatening complication of heart transplantation that may require venoarterial extracorporeal membrane oxygenation (VA-ECMO) support. Surgical practices and management strategies regarding VA-ECMO vary between and within centers.MethodsWe performed a single-center retrospective cohort study on adult patients who received VA-ECMO for primary graft failure between 2013 and 2020. Clinical data were obtained from chart review and national databases. Patients were stratified by transplantation before or after 2017, when our center adopted additional objective criteria for VA-ECMO, adopted partial-flow support, and changed from central cannulation to chimney graft arterial cannulation of brachiocephalic, axillary, or aorta. The primary outcome was survival to device weaning. Secondary outcomes were survival to discharge, survival to 1 year, complications on support, and time to sedation weaning and extubation.ResultsFrom 276 heart transplant recipients, 39 severe primary graft failure patients requiring VA-ECMO were identified. Incidence of graft failure was 13% (n = 18 of 135) pre-2017 and 15% (n = 21 of 141) post-2017. Survival at all time points improved significantly after 2017, with greatest difference in survival to device weaning (61% pre-2017 vs 100% post-2017). After controlling for other factors in multivariable Cox regression modeling, transplantation after 2017 was a predictor of reduced mortality (hazard ratio, 0.209; 95% CI, 0.06-0.71; P = .01). Significant differences were not observed in other secondary outcomes of recovery.ConclusionsThe new VA-ECMO strategy displayed reasonable survival and a remarkable improvement from the prior system.     

The American Association for Thoracic Surgery (AATS) 2022 Expert Consensus Document: The use of mechanical circulatory support in lung transplantation

ObjectiveThe use of mechanical circulatory support (MCS) in lung transplantation has been steadily increasing over the prior decade, with evolving strategies for incorporating support in the preoperative, intraoperative, and postoperative settings. There is significant practice variability in the use of these techniques, however, and relatively limited data to help establish institutional protocols. The objective of the AATS Clinical Practice Standards Committee (CPSC) expert panel was to review the existing literature and establish recommendations about the use of MCS before, during, and after lung transplantation.MethodsThe AATS CPSC assembled an expert panel of 16 lung transplantation physicians who developed a consensus document of recommendations. The panel was broken into subgroups focused on preoperative, intraoperative, and postoperative support, and each subgroup performed a focused literature review. These subgroups formulated recommendation statements for each subtopic, which were evaluated by the entire group. The statements were then developed via discussion among the panel and refined until consensus was achieved on each statement.ResultsThe expert panel achieved consensus on 36 recommendations for how and when to use MCS in lung transplantation. These recommendations included the use of veno-venous extracorporeal membrane oxygenation (ECMO) as a bridging strategy in the preoperative setting, a preference for central veno-arterial ECMO over traditional cardiopulmonary bypass during the transplantation procedure, and the benefit of supporting selected patients with MCS postoperatively.ConclusionsAchieving optimal results in lung transplantation requires the use of a wide range of strategies. MCS provides an important mechanism for helping these critically ill patients through the peritransplantation period. Despite the complex nature of the decision making process in the treatment of these patients, the expert panel was able to achieve consensus on 36 recommendations. These recommendations should provide guidance for professionals involved in the care of end-stage lung disease patients considered for transplantation.