Cardiovascular Disease |

Cardiac Determinants of Flow Limitation in ECMO in a Porcine Model FREE TO VIEW

Steven Keller, MD; Sarah Fink; Henry Halperin, MD; Muz Zviman, MD
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National Institutes of Health, Bethesda, MD

Chest. 2015;148(4_MeetingAbstracts):46A. doi:10.1378/chest.2278853
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SESSION TITLE: Advances in Cardiac Disease

SESSION TYPE: Original Investigation Slide

PRESENTED ON: Monday, October 26, 2015 at 04:30 PM - 05:30 PM

PURPOSE: VA ECMO has been described in the resuscitation of patients in sudden cardiac arrest. Limiting its use is the needed expertise to place large bore cannulae for vascular access to ensure adequate blood flow. Decreased cannulae size results in higher pressures needed to generate equivalent flows which in turn induce vessel collapse as pressures increase. We hypothesize that the state of cardiac contraction influences maximum obtainable withdrawal rates and that higher withdrawal rates are obtainable during cardiac arrest.

METHODS: Three 50 kg adult pigs were intubated and sedated with inhaled isoflurane. Pressure in the aortic arch and right atrium was measured with Millar catheters with coronary perfusion pressure calculated as the difference. A 15 Fr 18 cm long Medtronic arterial cannula was inserted into the femoral artery of each pig. A 15 Fr, 17 Fr, or 21 Fr 50 cm long Medtronic venous cannula was placed in the femoral vein to the level of the diaphragm in each pig. ECMO was initiated with a Medtronic centrifugal pump and Maquet Quadrox adult oxygenator. Flow measurements performed at a series of pump speeds until suction events resulted in flow cessation. A pacing wire was inserted into the right ventricle. Measurements were performed with the animals in three different cardiac states: (1) normal sinus rhythm; (2) paced at a rate of 240 beats per min; (3) cardiac arrest secondary to hypoxemia induced by ventilation with 100% nitrogen gas.

RESULTS: Rapid pacing resulted in minimal cardiac output as demonstrated by the lack of aortic pressure deflections and was used to simulate a rapidly reversible state in which the heart did not work against the ECMO circuit. The 15 Fr withdrawal cannula experienced suction events at low pump speeds during sinus rhythm but was able to support flow rates of 40 to 70 ml/kg/min during both rapid pacing and cardiac arrest. The 17 Fr and 21 Fr venous withdrawal cannulae were able to support a flow rate of 40 ml/kg/min during sinus rhythm until experiencing suction events at higher pump speeds. The larger cannulae supported flows comparable to the smaller cannula during paced and arrest states.

CONCLUSIONS: Smaller ECMO venous cannulae are able to sustain adequate venous withdrawal to maintain flow rates of 50 to 70 ml/kg/min in a porcine model of cardiac arrest but can supply only minimal support during normal cardiac function.

CLINICAL IMPLICATIONS: The successful use of smaller vascular cannulae may lead to wider use of ECMO for use in supporting patients in cardiac arrest.

DISCLOSURE: The following authors have nothing to disclose: Steven Keller, Sarah Fink, Henry Halperin, Muz Zviman

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