Extracorporeal membrane oxygenation
|Extracorporeal membrane oxygenation|
In intensive care medicine, extracorporeal membrane oxygenation (ECMO) or extracorporeal life support (ECLS) is an extracorporeal technique of providing both cardiac and respiratory support to patients whose heart and lungs are unable to provide an adequate amount of gas exchange to sustain life. This intervention has mostly been used on pediatric patients, but it is seeing more use in adult patients with cardiac and respiratory failure. ECMO works by removing blood from the persons body and artificially removing the carbon dioxide and oxygenating red blood cells. Generally it is only used in the later treatment of a person with heart or lung failure as it is solely a life-sustaining intervention.
- 1 Types
- 2 Outcomes
- 3 Indications
- 4 Contraindications
- 5 Initiation
- 6 Maintenance
- 7 Weaning and discontinuing
- 8 Complications
- 9 Current findings
- 10 References
There are several forms of ECMO, the two most common of which are the veno-arterial (VA) and veno-venous (VV). In both modalities, blood drained from the venous system is oxygenated outside of the body. In VA ECMO, this blood is returned to the arterial system and in VV ECMO the blood is returned to the venous system. In VV ECMO, no cardiac support is provided.
In veno-arterial ECMO – a venous cannula is usually placed in the right common femoral vein for extraction and an arterial cannula is usually placed into the right femoral artery for infusion. The tip of the femoral venous cannula should be maintained near the junction of the inferior vena cava and right atrium, while the tip of the femoral arterial cannula is maintained in the iliac artery. In adults accessing the femoral artery is preferred because the insertion is simpler. Central VA ECMO may be used if cardiopulmonary bypass has already been established (with cannulae in the right atrium and ascending aorta)
In veno-venous ECMO cannulae are usually placed in the right common femoral vein for drainage and right internal jugular vein for infusion. Alternatively, a dual lumen catheter is inserted into the right internal jugular vein, draining blood from the superior and inferior vena cavae and returning it to the right atrium.
With acute respiratory failure use of ECMO has been shown to improve survival rates. Survival rates from 50—70 percent have been reported in observational and uncontrolled clinical trials. The survival rates reported are better than historical survival rates. In the United Kingdom, respiratory (VV) ECMO is concentrated in designated ECMO centres to ensure top quality care.
Guidelines that describe the indications and practice of ECMO are published by the Extracorporeal Life Support Organization (ELSO). Criteria for the initiation of ECMO include acute severe cardiac or pulmonary failure that is potentially reversible and unresponsive to conventional management. Examples of clinical situations that may prompt the initiation of ECMO include the following:
- Hypoxemic respiratory failure with a ratio of arterial oxygen tension to fraction of inspired oxygen (PaO2/FiO2) of <100 mmHg despite optimization of the ventilator settings, including the Fraction of Inspired Oxygen (FiO2), positive end-expiratory pressure (PEEP), and inspiratory to expiratory (I:E) ratio
- Hypercapnic respiratory failure with an arterial pH <7.20
- Refractory cardiogenic shock
- Cardiac arrest
- Failure to wean from cardiopulmonary bypass after cardiac surgery
- As a bridge to either cardiac transplantation or placement of a ventricular assist device
Most contraindications are relative, balancing the risks of the procedure (including the risk of using valuable resources that could be used for others) vs. the potential benefits. The relative contraindications are:
- Conditions incompatible with normal life if the patient recovers
- Preexisting conditions that affect the quality of life (CNS status, end stage malignancy, risk of systemic bleeding with anticoagulation)
- Age and size of patient
- Futility: patients that are too sick, have been on conventional therapy too long, or have a fatal diagnosis.
ECMO should be performed only by clinicians with training and experience in its initiation, maintenance, and discontinuation. Once it has been decided that ECMO will be initiated, the patient is anticoagulated with intravenous heparin and then the cannulae are inserted. ECMO support is initiated once the cannulae are connected to the appropriate limbs of the ECMO circuit.
Cannulae are usually placed percutaneously by the Seldinger technique. The largest cannulas that can be placed in the vessels are used in order to maximise flow and minimise pressures bernoulli equation
ECMO required for complications of cardiac surgery can be placed directly into the appropriate chambers of the heart or great vessels.
Following cannulation, the patient is connected to the ECMO circuit and the blood flow is increased until respiratory and hemodynamic status is stable.
Once the initial respiratory and hemodynamic goals have been achieved, the blood flow is maintained at that rate. Frequent assessment and adjustments are facilitated by continuous venous oximetry, which directly measures the oxyhemoglobin saturation of the blood in the venous limb of the ECMO circuit.
VV ECMO is typically used for respiratory failure, while VA ECMO is used for cardiac failure. There are unique considerations for each type of ECMO, which influence management.
Near-maximum flow rates are usually desired during VV ECMO to optimize oxygen delivery. In contrast, the flow rate used during VA ECMO must be high enough to provide adequate perfusion pressure and venous oxyhemoglobin saturation (measured on drainage blood) but low enough to provide sufficient preload to maintain left ventricular output.
Since most patients are fluid-overloaded when ECMO is initiated, aggressive diuresis is warranted once the patient is stable on ECMO. Ultrafiltration can be easily added to the ECMO circuit if patients are unable to produce sufficient urine for diuresis.
Left ventricular monitoring
Weaning and discontinuing
For patients with respiratory failure, improvements in radiographic appearance, pulmonary compliance, and arterial oxyhemoglobin saturation indicate that the patient may be ready to be taken off of ECMO support. For patients with cardiac failure, enhanced aortic pulsatility correlates with improved left ventricular output and indicates that the patient may be ready to be taken off of ECMO support. Once the decision has been made to discontinue ECMO, the cannulae are removed.
Veno-venous ECMO liberation trial
VV ECMO trials are performed by eliminating all countercurrent sweep gas through the oxygenator. Extracorporeal blood flow remains constant, but gas transfer does not occur. Patients are observed for several hours, during which the ventilator settings that are necessary to maintain adequate oxygenation and ventilation off ECMO are determined as indicated by arterial and venous blood gas results.
Veno-arterial ECMO liberation trial
VA ECMO trials require temporary clamping of both the drainage and infusion lines, while allowing the ECMO circuit to circulate through a bridge between the arterial and venous limbs. This prevents thrombosis of stagnant blood within the ECMO circuit. In addition, the arterial and venous lines should be flushed continuously with heparinized saline or intermittently with heparinized blood from the circuit. In general, VA ECMO trials are shorter in duration than VV ECMO trials because of the higher risk of thrombus formation
A common consequence in ECMO-treated adults is neurological injury, which may include subarachnoid hemorrhage, ischemic watershed infarctions, hypoxic-ischemic encephalopathy, unexplained coma, and brain death. Bleeding occurs in 30 to 40 percent of patients receiving ECMO and can be life-threatening. It is due to both the necessary continuous heparin infusion and platelet dysfunction. Meticulous surgical technique, maintaining platelet counts greater than 100,000/mm3, and maintaining the target ACT reduce the likelihood of bleeding.Heparin-induced thrombocytopenia (HIT) is increasingly common among patients receiving ECMO. When HIT is suspected, the heparin infusion is usually replaced by a non-heparin anticoagulant. There is retrograde blood flow in the descending aorta whenever the femoral artery and vein are used for VA ECMO. Stasis of the blood can occur if left ventricular output is not maintained, which may result in thrombosis. ECMO has yet to have proven survival benefit in adults with acute respiratory distress syndrome (ARDS). In VA ECMO, patients whose cardiac function does not recover sufficiently to be weaned from ECMO may be bridged to a ventricular assist device (VAD) or transplant. A variety of complications can occur during cannulation, including vessel perforation with hemorrhage, arterial dissection, distal ischemia, and incorrect location (e.g., venous cannula within the artery), but these events occur highly infrequently.
In infants aged less than 34 weeks of gestation, several physiologic systems are not well-developed, especially the cerebral vasculature and germinal matrix, resulting in high sensitivity to slight changes in pH, PaO2, and intracranial pressure. Preterm infants are at unacceptably high risk for intraventricular hemorrhage (IVH) if administered ECMO at a gestational age less than 32 weeks. Also later, given the risk of IVH, it has become standard practice to ultrasound the brain prior to administering ECMO.
A recent study showed that a factor XIIa inhibitory antibody provides thromboprotection in extracorporeal circulation without increasing bleeding risk. Experiments on neonatal animals showed that ECMO treatment can lead to apoptosis of enterocytes, damage of the intestinal mucosal barrier and bacterial translocation. This might explain greater severity of systemic inflammatory response syndrome in neonates. ECMO has also seen its use on cadavers as being able to increase the viability rate of transplanted organs.
- Van Meurs, Krisa; Lally, Kevin; Zwischenberger, Joseph B.; Peek, Giles, eds. (2005). ECMO: Extracorporeal Cardiopulmonary Support in Critical Care. Ann Arbor: Extracorporeal Life Support Organization. ISBN 978-0-9656756-2-8.[page needed]
- Madershahian, Navid; Nagib, Ragi; Wippermann, Jens; Strauch, Justus; Wahlers, Thorsten (2006). "A Simple Technique of Distal Limb Perfusion During Prolonged Femoro-Femoral Cannulation". Journal of Cardiac Surgery 21 (2): 168–9. doi:10.1111/j.1540-8191.2006.00201.x. PMID 16492278.
- Wang, Dongfang; Zhou, Xiaoqin; Liu, Xiaojun; Sidor, Bill; Lynch, James; Zwischenberger, Joseph B. (2008). "Wang-Zwische Double Lumen Cannula—Toward a Percutaneous and Ambulatory Paracorporeal Artificial Lung". ASAIO Journal 54 (6): 606–11. doi:10.1097/MAT.0b013e31818c69ab. PMID 19033774.
- Peek, GJ; Moore, HM; Moore, N; Sosnowski, AW; Firmin, RK (1997). "Extracorporeal membrane oxygenation for adult respiratory failure". Chest 112 (3): 759–64. doi:10.1378/chest.112.3.759. PMID 9315812.
- Lewandowski, K.; Rossaint, R.; Pappert, D.; Gerlach, H.; Slama, K.-J.; Weidemann, H.; Frey, D. J. M.; Hoffmann, O.; Keske, U. (1997). "High survival rate in 122 ARDS patients managed according to a clinical algorithm including extracorporeal membrane oxygenation". Intensive Care Medicine 23 (8): 819–35. doi:10.1007/s001340050418. PMID 9310799.
- Hemmila, Mark R.; Rowe, Stephen A.; Boules, Tamer N.; Miskulin, Judiann; McGillicuddy, John W.; Schuerer, Douglas J.; Haft, Jonathan W.; Swaniker, Fresca; Arbabi, Saman (2004). "Extracorporeal Life Support for Severe Acute Respiratory Distress Syndrome in Adults". Annals of Surgery 240 (4): 595–605; discussion 605–7. doi:10.1097/01.sla.0000141159.90676.2d. PMC 1356461. PMID 15383787.
- Brogan, Thomas V.; Thiagarajan, Ravi R.; Rycus, Peter T.; Bartlett, Robert H.; Bratton, Susan L. (2009). "Extracorporeal membrane oxygenation in adults with severe respiratory failure: A multi-center database". Intensive Care Medicine 35 (12): 2105–14. doi:10.1007/s00134-009-1661-7. PMID 19768656.
- Kolla, S; Awad, SS; Rich, PB; Schreiner, RJ; Hirschl, RB; Bartlett, RH (1997). "Extracorporeal life support for 100 adult patients with severe respiratory failure". Annals of surgery 226 (4): 544–64; discussion 565–6. doi:10.1097/00000658-199710000-00015. PMC 1191077. PMID 9351722.
- Rich, PB; Awad, SS; Kolla, S; Annich, G; Schreiner, RJ; Hirschl, RB; Bartlett, RH (1998). "An approach to the treatment of severe adult respiratory failure". Journal of critical care 13 (1): 26–36. doi:10.1016/S0883-9441(98)90026-0. PMID 9556124.
- Ullrich, R; Lorber, C; Röder, G; Urak, G; Faryniak, B; Sladen, RN; Germann, P (1999). "Controlled airway pressure therapy, nitric oxide inhalation, prone position, and extracorporeal membrane oxygenation (ECMO) as components of an integrated approach to ARDS". Anesthesiology 91 (6): 1577–86. doi:10.1097/00000542-199912000-00007. PMID 10598597.
- "General Guidelines for all ECLS Cases" (PDF). Extracorporeal Life Support Organization. Retrieved 2015-04-15.
- Cohen, Gordon; Permut, Lester (2005). "Decision making for mechanical cardiac assist in pediatric cardiac surgery". Seminars in Thoracic and Cardiovascular Surgery: Pediatric Cardiac Surgery Annual 8: 41–50. doi:10.1053/j.pcsu.2005.02.004. PMID 15818357.
- Vural, Kerem M. (2008). "Ventricular assist device applications". Anadolu Kardiyoloji Dergisi 8 (Suppl 2): 117–30. PMID 19028644.
- "Neurological Injury in Adults Treated With Extracorporeal Membrane Oxygenation". doi:10.1001/archneurol.2011.209. Retrieved 2013-08-08.
- Cornell, Timothy; Wyrick, Polly; Fleming, Geoffrey; Pasko, Deborah; Han, Yong; Custer, Joseph; Haft, Jonathan; Annich, Gail (2007). "A Case Series Describing the Use of Argatroban in Patients on Extracorporeal Circulation". ASAIO Journal 53 (4): 460–3. doi:10.1097/MAT.0b013e31805c0d6c. PMID 17667231.
- "Concepts of Neonatal ECMO". The Internet Journal of Perfusionists 1 (2). 2001. doi:10.5580/d9.
- Jobe, Alan H. (2004). "Post-conceptional age and IVH in ECMO patients". The Journal of Pediatrics 145 (2): A2. doi:10.1016/j.jpeds.2004.07.010.
- Larsson M, Rayzman V, Nolte MW et al. (Jan 2014). "A Factor XIIa Inhibitory Antibody Provides Thromboprotection in Extracorporeal Circulation Without Increasing Bleeding Risk.". Sci Transl Med. 6 (222): 222. doi:10.1126/scitranslmed.3006804. PMID 24500405.
- MohanKumar K (Feb 2014). "Intestinal epithelial apoptosis initiates gut mucosal injury during extracorporeal membrane oxygenation in the newborn piglet". Lab Invest. 94 (2): 150–160. doi:10.1038/labinvest.2013.149. PMC 3946757. PMID 24365747.
- Magliocca, JF; Magee, JC; Rowe, SA; Gravel, MT; Chenault Rh, 2nd; Merion, RM; Punch, JD; Bartlett, RH; Hemmila, MR (2005). "Extracorporeal support for organ donation after cardiac death effectively expands the donor pool". The Journal of trauma 58 (6): 1095–101; discussion 1101–2. doi:10.1097/01.ta.0000169949.82778.df. PMID 15995454.