Development of a Miniaturized Heart-Lung Machine For Neonates with Congenital Heart Defect
Predominantly standard adult Heart Lung Machines (HLMs) are used for paediatric cardiac surgery, only with individually downsized components. Downsizing is limited, e.g. by the required gas exchange surface, the tubing between the components, etc. In order to diminish known complications related to cardiopulmonary bypass (e.g. inflammatory reaction and capillary leak syndrome) we developed a new miniaturized heart lung machine (MiniHLM) for neonates, with significantly reduced priming volume and blood contact surface by integration of all major system components in one single device. The concepts could already be successfully proved in a first series of animal studies.
In particular, a rotary blood pump with reusable drive unit is centrically integrated into an oxygenator with 0.36 m2 gas exchange surface. The cardiotomy reservoir with integrated heat exchanger is directly connected to the pump inlet. Thus, tubing is only necessary between patient and MiniHLM (venous and arterial). This tubing is kept to a minimum length by placement of the MiniHLM directly at the operation table (figure 1).
A total priming volume of 103 ml could be achieved for the entire extracorporeal circuit (incl. a/v line), in contrast to the currently smallest commercially available device with 213 ml.
Clinically demanded blood flow rates of up to 700 ml/min at pressure drops of up to 250 mmHg could be easily achieved by the pump in an in-vitro setup simulating the clinical application.
In-vitro oxygenation tests proved a sufficient gas exchange rate for CO2 and Oxygen.
In animal experiments with female New Zealand white rabbits (n = 13; 4.1 ± 1 kg) the MiniHLM guaranteed both a sufficient gas exchange and an adequate blood flow. 12 rabbits could successfully be weaned off after 1 hour of aortic clamp time.
The first in-vitro and in-vivo-tests fully validate the concept of the MiniHLM. Its low priming volume and blood contact surface may significantly reduce complications during heart surgery in neonates.