The “Tube-In-Tube” Circuit

Abstract

Purpose: To conceive a method to deliver cold blood cardioplegia in neonates and young infants. Description: The “tube-in-tube” circuit consists of a 3-mm line (bloodline) which is inserted inside a 1/2 -in tube where cold water flows continuously (waterline). This circuit includes a filling volume of 18 mL of static prime and 15 mL for the collecting line (pump raceway). Several temperature samples were taken at different blood flows from 20 to 100 mL/min. Evaluation: Temperatures (in°C) at the needle tip were significantly lower when using the tube-in-tube cooling circuit if compared to standard cardioplegia circuit at flows up to 60 mL/min. Conclusions: The tube-in-tube circuit proved to be an effective strategy for low-flow cardioplegia delivery (<60 ml/min), which is particularly useful in neonates and young infants; the lower is the flow, the better is the cooling effect on the cardioplegia.