Hydraulic performance of 14-G hemodialysis catheters versus an 8-Fr arterial cannula in a mock 3-kg small-dog cardiopulmonary bypass circuit

Arterial cannulation for cardiopulmonary bypass in small dogs is challenging because small vessel diameters may preclude use of appropriately sized pediatric arterial cannulas. Although off-label use of 14-gauge hemodialysis catheters has been reported, their pressure-flow characteristics under small-dog cardiopulmonary bypass conditions remain unclear. This in vitro study evaluated one 8-French pediatric arterial cannula and six 14-gauge hemodialysis catheter specimens-separate side-hole and sealed specimens at effective lengths of 25, 32, and 38 mm-in a closed-loop mock circuit for a 3-kg small dog. A 34% (w/w) glycerol-water solution (viscosity 2.8 cP at 28°C) served as an approximate Newtonian blood analogue. The Stockert S5 pump flow-rate setting was increased from 50 to 350 mL/min; 50-300 mL/min was prespecified as the primary analysis range and 350 mL/min as exploratory. The reported outlet pressure was recorded 1,000 mm upstream of the test device, while inlet pressure was monitored 300 mm downstream and regulated to 60 mmHg; six technical runs per condition were conducted using the same physical device and circuit setup. Within the primary analysis range, outlet pressure was approximately 136-137 mmHg at 300 mL/min; mean differences for the 14-G specimens versus the 8-French cannula were +0.33 to +0.67 mmHg, with 95% confidence intervals from -1.33 to +2.15 mmHg. At 350 mL/min, outlet pressures were higher for all three side-hole 14-gauge specimens than for the 8-French cannula. At 300 mL/min, outlet pressure was approximately 2-3 mmHg lower for the side-hole specimens than for the sealed specimens across all catheter lengths. Together, these findings indicate small observed circuit-level differences in outlet pressure among tested devices within this standardized mock small-dog cardiopulmonary bypass circuit, but do not establish formal equivalence, device-to-device interchangeability, or clinical validity.