15
Intraoperative Device Management
After all cannula-to-tubing connections are completed, a clamp is placed on the return tubing of each pump, while all other clamps
are removed from the circuit. Before the outflow clamp is released, the pump set speed (RPM) is increased to at least 1,000 RPM in
order to prevent retrograde flow through the system. The set speed is then gradually increased to reach the desired flow rate. As the set
speed is gradually increased, CPB support can be simultaneously decreased to allow filling of the heart, and then terminated. During
weaning from CPB and initiation of CentriMag system support, the patient must be carefully monitored with hemodynamic monitoring
(usually CVP, PAP and ABP), echocardiography, manual palpation and visual inspection of the heart to ensure that adequate blood
volume is available for the desired flow and to reduce the risk of a suction event. For LVAD support, left atrial pressure should be
maintained between 10 and 15 mmHg in order to avoid suction within the left ventricle and inflow obstruction, which can lead to air
entrainment. For RVAD support, right atrial pressure should also be maintained between 10 and 15 mmHg.
CAUTION: Ensure that air does not enter into the circuit when the tubing is connected to the cannula.
CAUTION: If CPB support is not decreased as the set speed is increased, suction events may occur due to lack of volume.
The desired flow rate can be predetermined by calculating the flow needed to achieve a cardiac index of approximately 2.0-2.2
l/min/m
2
. As the flow is increased, the atria and/or ventricles are monitored for adequate pressure and blood volume. The console
operator continuously monitors the pump flow, RPM, and blood pressure for signs of suction within the circuit. Suction is most likely
when filling pressures are <10 mmHg and is accompanied by fluctuations in flow. When suction is detected, the speed of the pump
must be immediately decreased until the filling pressure and volume are adequate to increase the flow. The system should be
monitored frequently in the operating room when the patient’s chest is open as this is the period of highest risk for suction and air
entrainment.
The central venous pressure, flow rate, total cardiac output, pulmonary capillary wedge pressure, left atrial pressure (valuable, but not
essential) and arterial blood pressure should be monitored frequently as hemodynamic conditions change rapidly during surgery.
Communication of hemodynamic parameters between the surgeon, perfusionist, anesthesiologist, and console operator is vital to safe
support.
Initially, TEE, hemodynamic monitoring, palpation, and direct visualization of the heart will help to determine the volume of blood
available for the circuit and the optimal level of flow. After the chest is closed, the patient can be monitored with conventional
hemodynamic parameters (CVP, PCWP, MAP, LAP, PADP) and TEE to ensure adequate ventricular unloading, and to permit a gradual
increase to a target CI between 2.0 and 2.5 l/min/m
2
, consistent with the patient’s physiologic needs.
CAUTION: After closure of the chest, limited space in the inter-thoracic cavity may cause an observable decrease in flow.
TEE should also be used to rule out the presence of a patent foramen ovale after left ventricular decompression. A previously
undetected PFO may develop when the pump begins to decompress the left heart. If present, a significant defect should be repaired to
prevent right-to-left shunting and the resulting hypoxemia. Unloading of the ventricle(s) during VAD support may also cause atrial or
ventricular collapse, which may be able to be observed or assessed with manual palpation by the surgeon.
CAUTION: During closure of the chest, the CentriMag system flow and the patient’s hemodynamics must be monitored as
cannula position can change, altering flow through the pump.
Guidelines to Prevent Air Entrainment when Initiating Support
Guidelines to prevent air entrainment when initiating support include the following:
1.
Fill the chest with warm normal saline or CO
2
.
2.
Ensure adequate volume in heart chamber when coming off CPB bypass.
3.
Watch the circuit, flow, CVP, MAP and LAP (if monitored) continuously and be prepared to immediately clamp the outflow tubing
if air is observed.
4.
Partially inflate the lungs prior to separation from CPB.
5.
Maintain atrial pressures between 10 and 15 mmHg during surgery.
6.
Place the patient in Trendelenburg position.
7.
Check the heart and aorta for air with TEE.
8.
Increase RPM very slowly while initiating support.
9.
Under-perfuse circulation while the chest is open or patient is being moved.
CAUTION: If an increase in flow is not observed with an increase in set speed, suction may be occurring.
WARNING: If a suction event occurs and is not addressed promptly, there is potential for air entrainment.
Patient Care and Management
Postoperative care with the CentriMag system is similar to other types of mechanical circulatory support. Key principles of care
include hemodynamic stabilization, adequate anticoagulation, and prevention of wound infection. The intravascular volume must be
carefully assessed and controlled. Management of bleeding, and prompt blood product replacement, is essential to stabilization and
recovery. Frequent laboratory assessment of hematology, coagulation, enzymes, and blood chemistry must be used to evaluate end
organ function and to guide therapy.
