Article of the month – August 2020

Management of Challenging Cardiopulmonary Bypass Separation

Authors: Monaco F, Di Prima AL, Kim JH, Plamondon MJ, Yavorovskiy A, Likhvantsev V, Lomivorotov V, Hajjar LA, Landoni G, Riha H, Farag AMGA, Gazivoda G, Silva FS, Lei C, Bradic N, El-Tahan MR, Bukamal NAR, Sun L, Wang CY.

DOI: doi: 10.1053/j.jvca.2020.02.038.

Published: J Cardiothorac Vasc Anesth. 2020 Jun;34(6):1622-1635.

URL: https://www.jcvaonline.com/article/S1053-0770(20)30196-8/pdf

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Article Description:

• There are no current guidelines on the management of complex separation from CPB
• The present review aimed is to describe the most common scenarios associated with complex CPB separation, and to suggest management strategies adopting pharmacologic agents and mechanical circulatory support (MCS).  
• The routine management strategies of complex CPB separation of 17 large cardiac centers from 14 countries in 5 continents have been described.

Summary:

• The difficult CPB separation can be defined as the need of at least 2 inotropes or vasopressors to successfully accomplish the separation from CPB. A very difficult wean-off CPB occurs when the first weaning process fails, or the patient requires a mechanical device to be separated from CPB.
• The Vasoactive and Inotropic Score (VIS) can be used for decision making in patients with complex CPB separation. There are 3 possible categories of CPB separation according to VIS values: <10 is “easy”; 10 to 30 is “difficult”, >30 is “complex”, and in the latter case an MCS such as an intra-aortic balloon pump (IABP) is usually added to the inotropic support.
• Predictors for difficult separation from the CPB include age, previous myocardial infarction, low ejection fraction, mitral surgery, previous cardiac surgery, and long partial thromboplastin time and CPB duration.  
• Patients with anticipated difficult CPB separation can receive a pre-emptive pharmacologic (e.g. vasopressors, levosimendan or phosphodiesterase 3 inhibitors) or MCS (e.g. IABP).
• Caution should be exercised for control of the heart rate and rhythm and treating the atrioventricular conduction abnormalities and persistent ST elevation following aortic-cross clamp release.
• TEE is the cornerstone of diagnosis for complex CPB separation causes.
• Vasoplegic syndrome, defined as low MAP <50 mmHg or SPB <85 mmHg), low SVR (<600-800 dynes s cm⁻⁵, or SVRI <1800 dyne s cm⁻⁵ m²), normal or high CI >2.5 L min m²), normal or reduced CVP < 10 mmHg and PAOP <10 mmHg), and by an increased need for vasopressors (0.2-0.5 µg/kg/min of norepinephrine with normal intravascular volume), is around 9% after cardiac surgery.
• The therapeutic options for vasoplegic syndrome include using a vasoactive drug (eg, norepinephrine, phenylephrine, or vasopressin), transfusion to correct Hb level of at least 9 g/dL and administrating epinephrine, steroids, methylene blue, hydroxocobalamin, angiotensin II, and diphenhydramine.
• Acute RV failure after CPB could be diagnosed with high CVP in the context of an enlarged RV (a right mid-cavity diameter greater than 42 mm and a longitudinal diameter greater than 92 mm) with depressed contractility. TEE characteristics include (1) a TAPSE < 16 mm, (2) S’ wave at the TDI < 10 cm/sec, (3) right FAC < 30% or a decrease of 20% compared with the baseline, and (4) assessment of the RV geometry.
• Therapeutic interventions in RV dysfunction aim to optimize the preload, gas exchange and oxygenation, reduce the afterload, and improve the contractility.
• The vast majority of centers use dobutamine or epinephrine (with or without norepinephrine according to BP values) and less frequently nitroglycerine, dopamine, and vasopressin are considered therapeutic options for impaired RV function in the absence of pulmonary hypertension. MCS including IABP, R-IMPELLA, and VA-ECMO are reserved as the last option.
• If RV failure is associated with pulmonary hypertension, inodilators and/or inhaled nitric oxide are widely applied on top of catecholamines.
• In the case of severe pulmonary hypertension, the use of inhalational nitric oxide and iloprost would be helpful.
• Attention should be paid for preload optimization in case of post-CPB acute LV failure using either fluid challenge or diuretics.
• Therapeutic interventions for the acute LV systolic failure include using inotropes (e.g. epinephrine +/- norepinephrine, levosimendan (in case of elevated SVRI) and MCS including IABP, IMPELLA, VA-ECMO, or LVAD.
• LV diastolic failure might get benefit from avoidance of dyssynchrony from biventricular pacing and using calcium antagonists and inodilators.

Conclusion:

• CPB separation is a progressive transition from full MCS to spontaneous heart activity.
• A standardized approach for CPB separation that focuses on simple hemodynamic targets under TEE assessment along with a therapy involving vasopressors, inotropes, vasodilators, and eventually MCS devices can potentially improve outcomes.