Source: future think tank
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1. ECMO is directly involved in the treatment of NCP patients, but the equipment is in short supply
ECMO is a technology of severe treatment. For severe patients infected with new coronavirus, ECMO equipment can temporarily replace human heart and lung, waiting for the recovery of cardiopulmonary function. Since January 22, Central South Hospital of Wuhan University successfully treated severe pneumonia with ECMO, according to incomplete statistics, six hospitals have used ECMO technology to pull severe patients back from the edge of death.
Novel coronavirus pneumonia has become a "life-saving straw" for new crown pneumonia patients in many hospitals, using ECMO technology to succeed. But in the face of the epidemic, relevant parties are also trying to coordinate and support Hubei. According to the current relevant reports, the medical teams in Shandong and Zhejiang not only sent out elite support to Hubei, but also carried ECMO and other key equipment with them. Shiyan Taihe hospital purchased an assembled ECMO equipment through national resource allocation. It shows the importance and urgency of ECMO in the first-line severe treatment.
When the health and Health Commission invited medical teams from all over the country to assist Hubei, it made requirements for the equipment carried by all units. In the letter on February 12, it was clearly pointed out that many hospitals carried ECMO equipment to Wuhan. In view of the small number of ECMO equipment purchased by most hospitals in China at present, one set is standard, in fact, each hospital takes the best equipment for severe patients to support. It also shows that ECMO plays an important role in emergency and critical care.
2. ECMO is an auxiliary artifact for the treatment of severe patients
2.1. ECMO is an essential equipment of ICU, and upstream capacity is in short supply
The full name of ECMO is extractorporeal membrane oxygen generation, which is commonly known as artificial cardiopulmonary mechanism and "Yeke membrane". It is used to provide continuous cardiopulmonary respiration and circulation for patients with severe cardiopulmonary failure, so as to maintain the life of patients.
Its working principle is to drain the patient's venous blood to the outside of the body, after the membrane oxygenator (its function is similar to artificial lung, referred to as membrane lung) oxygenation and carbon dioxide removal, it is transported back to the patient's body, and undertakes the function of gas exchange and (or) part of blood circulation. ECMO technology mainly includes venovenous ECMO (VV-ECMO) and venoventricular ECMO (VA-ECMO). In these two ways, the blood discharged from the venous system will be oxidized in vitro, VV only has the respiratory assistance function, while VA has the circulatory and respiratory assistance function at the same time.
The core part of ECMO is membrane lung and blood pump, which play the role of artificial lung and artificial heart respectively. It can provide short-term cardiopulmonary support for patients with severe cardiopulmonary failure, and win precious time for the rescue of critical illness. It is the most core support means for severe cardiopulmonary failure at present, also known as the "last straw" for severe patients.
ECMO system mainly includes blood driven pump (usually centrifugal pump) and matching disposable consumables. Among them, consumables include blood pipeline (cuff), membrane oxygenator, pump head, intubation (used for blood drainage and reinfusion) and various joints. In addition, the equipment includes a temperature changing water tank for regulating body temperature, an air oxygen mixer for regulating oxygen concentration, and detection equipment for blood oxygen saturation, pressure, temperature sensors, etc.
Considering the critical nature of patients' condition and the complexity of ECMO system, the international organization for in vitro life support (elso) suggests that ECMO center should be built in ICU with high medical level as the main advanced life support form for the treatment of various acute circulatory and / or respiratory failure.
2.1.1. The core membrane lung materials of ECMO are in short supply and the production capacity is limited
ECMO is a niche product with few daily applications. In fact, ECMO is composed of a complete set of equipment system, upstream raw materials of various types, electronic components, high-end materials, etc.; while ECMO equipment manufacturers produce core membrane lungs, pumps, consumables, etc., combined with other equipment, to form a complete system; at present, the hospitals with high medical level have the ability to manage ECMO.
In terms of upstream raw materials, the core part of ECMO raw materials is the membrane lung which bears the blood oxygen and the internal part is composed of hollow microporous fiber membrane wires. When the system is running, the patient's blood flows outside the hollow fiber membrane wires and oxygen is injected inside the membrane wires. The carbon dioxide in the blood and oxygen in the membrane wires are replaced by the way of differential pressure to realize Now the gas exchange function of the lung. This requires that the material not only has good air permeability, but also can realize long-term hydrophobicity, so as to meet the requirements of continuous operation for weeks or even months. PMP (poly-4-methyl-1-pentene) is a kind of polyolefin material with excellent performance. It has good oxygen flux, nitrogen and oxygen selectivity, low dissolution and biological safety. It is recognized as the optimal medium of "membrane lung oxygenator". At present, only membrana company of 3M company can supply this material exclusively. Due to its tight production capacity, the capacity of downstream ECMO enterprises is limited; and due to its supply monopoly and price monopoly, the price remains high.
At present, the main manufacturers of ECMO in the world are Medtronic, mcowell, SOLIN, etc., which are dominated by imported foreign enterprises. Domestic MAQUET (mcowell) and Medtronic occupy the main market. Domestic companies do not produce ECMO manufacturers. They have their own parts in time, but also mainly puncture catheter and connecting catheter in consumables package And other auxiliary consumables, but the core components such as pump and membrane lung cannot be supplied.
Membranous lung is the core component of ECMO system. Three generations of products have been developed for gas exchange. At present, the materials of membrane lung on the market include the first generation of solid silica membrane, the second generation of microporous hollow fiber membrane and the third generation of solid hollow fiber membrane (PMP).
The development of the third generation of membrane lung materials has gradually improved the clinical application effect: the first generation of solid silica gel membrane has the advantages of good compatibility and less plasma leakage, but it has the problem of exhaust difficulty; the second generation of microporous hollow fiber membrane has solved the problem of exhaust difficulty, but due to its microporous membrane prone to plasma leakage and loss of function, it has limited its clinical application At present, the third generation solid hollow fiber membrane mainly used combines the advantages of the first generation and the second generation membrane lung materials, overcomes the problem of plasma leakage, and effectively prolongs the clinical use time of ECMO.
2.1.2. ECMO has a history of nearly 60 years
ECMO is a kind of cardiopulmonary bypass, which is born with the concept of cardiopulmonary bypass. In fact, it was not until the 1980s that the ECMO center was established in the hospital as the real emergency center of the hospital.
In 1953, cardiopulmonary bypass was born.
In 1960, Bartlett, emeritus professor of the University of Michigan Medical Center and his colleagues launched a pioneering exploration on ECMO. But at that time, there were still a series of problems in the use of ECMO equipment, such as difficult to maintain for more than a few hours, the contradiction between heparin anticoagulation and bleeding, etc.
From 1961 to 1970, membrane oxygenator appeared, which separated blood gas phase with semi permeable membrane, protected red blood cells and platelets, and made ECMO safe for a long time.
From 1971 to 1975, the anticoagulation control technology was improved, which made it possible to extend the use of cardiopulmonary bypass technology. In 1971, J Donald hill and his team performed the first successful long-term ECMO life support operation. After 1972, ECMO was used for circulatory failure.
In 1975, Bartlett et al. Of the University of Michigan Medical School successfully used ECMO to treat a newborn with persistent fetal circulation for the first time.
In 1980, Bartlett led and established the world's first ECMO center. Subsequently, more than 100 ECMO centers have been established around the world. Bartlett is known as the "father of ECMO" for his leading R & D and outstanding contribution to ECMO promotion.
2.1.3. ECMO is mainly used in critical patients to give time to heart and lung
In recent years, the clinical indications of ECMO have been expanding, including cardiogenic shock, severe acute respiratory failure and severe circulatory failure
1. Serious cardiogenic shock caused by various reasons, such as after cardiac surgery, myocardial infarction, cardiomyopathy, myocarditis, cardiac arrest, cardiac transplantation, etc;
2. Severe acute respiratory failure caused by various reasons, such as severe ARDS, asthma status, transition to lung transplantation, primary graft failure after lung transplantation, diffuse alveolar hemorrhage, pulmonary hypertension crisis, pulmonary embolism, severe bronchopleural fistula, etc;
3. Severe circulatory failure caused by various reasons, such as septic shock, frostbite, large area severe burn, drug poisoning, CO poisoning, drowning, severe trauma, etc.
According to the statistical data, the majority of Chinese ECMO patients are adults, followed by children, with the least number of newborns. Compared with the global elso (International Organization for extracorporeal life support), the number of children and newborns is less, which is still the most important in the future development of ECMO in China. In the indications, ECMO is used for respiratory and cardiac indications The proportion of ECMO is the highest. In all kinds of patients, the proportion of both is more than 80%, which is the main clinical support scenario of ECMO.
In terms of patients' prognosis, the in-hospital survival rate of patients with different populations and indications is basically consistent with the global elso data, indicating that the survival rate of ECMO patients in China is basically consistent with the international level.
2.1.4. ECMO has many complications, so it is necessary to establish a professional ECMO treatment center
Patients receiving ECMO circulatory assistance are usually in critical condition. In addition, ECMO is a high consumption, high trauma and advanced life support mode, during which there may be many complications, including bleeding, infection and nervous system complications.
1. Bleeding: during the period of ECMO assistance, the blood is in a continuous hypercoagulable state, and the incidence of thromboembolism is as high as 20%. Despite the current use of heparin coated loops, anticoagulation is still required during ECMO assistance. Heparin is the most commonly used anticoagulant during ECMO, but it also increases the risk of bleeding. It has been reported that the incidence of bleeding is 12% - 52%, mainly in PCs patients. Hemorrhage is common in the incision or the intubation site of ECMO, but intracranial hemorrhage is more serious, even endangering the life of patients. In rare cases, heparin induced thrombocytopenia with thrombosis (HITT) may occur.
2. Infection: infection during ECMO assisted period is also one of the common complications. The incidence of nosocomial infection in ECMO assisted patients is 9% ~ 65%. Long term ECMO assistance is the most important risk factor of infection.
3. Nervous system complications: in patients with circulatory failure or Ca, there was cerebral ischemia and anoxia injury before receiving ECMO assistance, and ECMO assistance brought about reperfusion attack. During the period of ECMO, heparin anticoagulation, low level of coagulation factor and large fluctuation of blood pressure may increase the complications of nervous system. Neurological complications during ECMO assisted period include four main categories: brain death, cerebral infarction, intracranial hemorrhage and epilepsy. The incidence rate is over 15%, and ECPR patients are higher.
ECMO is a high-risk, complex and traumatic treatment method, which is generally only considered for patients with severe cardiopulmonary failure who fail in conventional treatment and whose expected mortality is more than 80%. Because ECMO is very critical to treat patients, in order to ensure the success rate of ECMO assistance, the proposal of developing adult extracorporeal membrane oxygenation project in China published by Chinese critical emergency medicine suggests that the establishment of ECMO treatment center may be a better model