Background: Focal cerebral hypothermia via intracarotid cold saline infusion (CSI) is an emerging therapy for acute stroke. Systems of cold saline delivery tested in humans have been thermally inefficient and failed to achieve target cortical temperatures. We applied a set of thermodynamic enhancements to improve thermal efficiency of CSI systems.
Methods: We replicated the previously described CSI system composed of a cold saline bag (4°C), connected to a 5-Fr diagnostic angiographic catheter immersed in a model of aortic counterflow at 37°C and infusing at a rate of 33 cc/min. Three adjustments were introduced to the system: catheter insulation via a shuttle catheter, higher catheter flow rate (50 cc/min) and external cooling of the system. Those were collectively labeled Cold Preservation via External Cooling, Insulation and Supplemented flow (Cold-PRECISE). We compared the standard system with Cold-PRECISE and with each adjustment separately. Primary outcome was temperatures collected at tubing outlet, catheter tip and the estimated perfusate temperature. We used ANCOVA to compare primary outcomes adjusting for potential confounders.
Results: Individual system adjustments improved thermal efficiency at all primary endpoints (Table 1).
Compared to standard CSI, insulation and higher flow rate reduced perfusate temperatures by 0.33 and 1.96°C respectively (p <0.001). External cooling reduced tubing outlet by 8.95°C (p 0.03) but had no statistically significant impact on perfusate temperature. The collective implementation of system adjustments had a synergistic effect with catheter tip and perfusate temperatures of 19.57 ± 0.34 and 29.87 ± 0.13 vs 27.13 ± 0.13 and 34.43 ± 0.05 respectively (p <0.001).
Conclusion: Cold-PRECISE system preserved coldness of locally infused saline, achieving perfusate temperatures that are estimated to meet target cortical temperatures. The clinical efficacy of this system should be evaluated in future clinical trials.