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undergoing CPB that compared microemboli detection through a transcranial Doppler with and without the use of an arterial line filter [ 5 ]. They found that patients with fewer microemboli detected were significantly less likely to have cognitive impairment after surgery. Data on the use of a dry venous technique is not readily available; however, the use of dry venous lines is not 0 %.
One way to utilize a primed venous line while also reducing hemodilution is by using venous autologous priming( VAP). With VAP, the crystalloid is shuttled into a bag in a controlled manner by displacing it with the patient’ s blood. Utilizing this technique whenever possible is a Class I, Level B recommendation [ 3 ]. While this option reduces both hemodilution and GME production, some patients may not be able to tolerate VAP due to becoming hemodynamically compromised from blood loss during the VAP process. In this instance, utilizing a dry venous technique can reduce hemodilution while keeping the patient hemodynamically stable without the need for administering vasopressors.
While the study by Hudacko and colleagues compared GME production in a dry venous line versus a primed venous line, this study was done on a pediatric circuit with an oxygenator lacking an integrated arterial line filter [ 4 ]. Our study is the first to look at GME production in a dry versus primed venous line with an adult circuit and associated components. This includes the utilization of a modern oxygenator with an integrated arterial line filter. We hypothesized that there would not be a significant difference in GME( post-oxygenator) with the use of a dry venous line compared to a primed venous line upon initiation of CPB. Additionally, we explored the effects of VAVD pressures and CPB initiation techniques on GME variation. If a dry venous technique yields acceptable levels of GME, its use could be another strategy in a multimodal approach to reduce hemodilution. If there is a significant increase in GME levels, this could potentially influence clinical practice and reduce GME reaching patients.
Materials and methods Circuit components
To execute the trials of this study, several considerations and pieces of equipment were necessary. A hypobaric oxygenator was needed to act as the patient, so GME was not recirculated and counted more than once. To construct this hypobaric oxygenator, a LivaNova( London, UK) Inspire 8F was sealed off by applying a sealant to all entrances of the oxygenator besides the blood inlet port, the blood outlet port, and the gas line inlet( which we used to introduce a negative pressure on the oxygenator to pull air). The hypobaric oxygenator was the only makeshift component needed for these trials.
Additional components consisted of a Terumo( Ann Arbor, MI, USA) System 1 heart-lung machine with an arterial roller head, arterial and venous temperature probes, a vacuum pressure line, an arterial pressure line, and tubing clamps. The circuitry used was the LivaNova( London, UK) reservoir and 8F oxygenator, a 3-port manifold, the hypobaric oxygenator, a Medtronic( Dublin, Ireland) reservoir, a vacuum source, and the Emboli Detection and Classification( EDAC) air quantifier
( LUNA Innovations, Blacksburg, VA) with 3 measuring probes.
Pressure lines were used for the pressure transducers, factory shunt lines were used to circulate through the manifold as well as the oxygenator purge, and the main circuitry connecting all of the components was ⅜ inch tubing with luge tubing expanding to ½ inch within the arterial roller head. The hypobaric oxygenator outlet was connected to the venous inlet of the LivaNova reservoir by 6 feet of ½ inch tubing. At the start of the 6 feet of ½ inch venous tubing, a quick-connect attachment was placed to easily drain the venous line for all dry trials. The last component was a small heater-cooler unit connected to the oxygenator. The fluid used in this study was 0.9 % normal saline with 1342 mL for the control prime volume and 1102 mL for the dry venous line prime volume.
To count and quantify GME, the EDAC transducer emits ultrasonic pulses every 1 ms that are reflected by emboli in the blood as they pass through the EDAC connector. The amplitude of the reflected signals is then analyzed to determine bubble size, count, and calculated volume( total embolic load).
Circuit setup The circuit setup emulated a standard bypass configuration, commencing with the LivaNova reservoir. Fluid was drawn through the luge tubing in the arterial roller head and propelled through the LivaNova Inspire 8F oxygenator, with the manifold line open and the purge line closed. The fluid was then pumped through 3 / 8-inch tubing into the hypobaric oxygenator to remove any GME present in the system( Figure 1).
After exiting the hypobaric oxygenator, the fluid was directed through a section of 3 / 8-inch tubing, leading to a ⅜-⅜-⅜ inch Y connector. The fluid was pushed straight through the Y connector past the quick-connect, through a ⅜-½ connector to a 6-foot length of ½-inch tubing back to the venous inlet of the LivaNova reservoir( Figure 1).
On the other port of the ⅜-inch Y connector, a Medtronic reservoir was mounted at the top of the heart-lung machine to simulate patient volume( 1 L) entering the circuit. Temperature probes were positioned at the venous inlet of the LivaNova reservoir and the arterial outlet of the LivaNova 8F oxygenator. The vacuum source was split into two lines, one was connected to the hypobaric oxygenator set at �800 mmHg, while the other line ran to a regulator and into the venous reservoir to maintain controlled negative pressure( Figure 1).
Within the circuit, 3 EDAC sensors were strategically placed. The first was positioned post-LivaNova reservoir and pre-arterial roller head. The second was placed post-LivaNova Inspire 8F oxygenator and pre-hypobaric oxygenator, while the third was positioned post-hypobaric oxygenator( Figure 1).
For volume reset into the Medtronic reservoir, a ⅜-inch line was connected from the cardioplegia port of the oxygenator to the top of the Medtronic reservoir. This line remained clamped during all trials and served solely for resetting volume.
After configuring the circuit, each trial was organized using one of three distinct methods. The control trials featured a fully primed venous line without any negative pressure applied to the reservoir. In the subsequent set of trials, the circuit was primed,