Quantitative and qualitative investigation of shunt failure in an in vitro hemorrhagic hydrocephalus model

Previous studies on posthemorrhagic hydrocephalus (PHH) reported notable shunt failure rates as high as 45.1% within the first six months of placement. Using the Automated, In Vitro Model for Hydrocephalus Research (AIMS), we investigated the impact of CSF-like diluted blood solution on ventricular catheters and external ventricular drains (EVD) using quantitative (flow and pressure measurements) and qualitative (real-time brightfield video capture) methods.

The shunt failure criteria were set at greater than or equal to 30 ${cmH}_{2}O$ such that the experiment was manually terminated if pressure surpassed 30 ${cmH}_{2}O$ differential pressure at any point within 24 h. To investigate our hypotheses, shunt failure was investigated in nine groups of catheters (n = 4 per group). Saline was utilized to dilute heparinized whole porcine blood to prepare blood-saline solutions at two concentrations of 0.05 and 0.5 volume percent (v/v%). The bulk input flow rate was set at 0.3 $\frac{mL}{\min }$ for all samples except where the flow rate was intentionally varied. The rate of pressure increase (pressurization rate) was used in all statistical analyses.

Over 500 h of data were gathered without leaks or ruptures. There was a statistically significant difference in the pressurization rate across blood concentration groups (P = 0.005). All the barium-impregnated and antibiotic-impregnated catheters reached 30 ${cmH}_{2}O$ threshold at 0.5% concentration. A statistically significant difference was observed in the pressurization rate (P = 0.029). A more pronounced difference was observed between the antibiotic-impregnated ventricular catheters and antibiotic-impregnated EVDs. All four EVDs completed the 24-hour experiment and did not reach the pressure threshold (P = 0.029).

A direct relationship was observed between blood concentration and the pressurization rate, such that shunts and EVDs that were exposed to higher concentrations of blood consistently reached 30 ${cmH}_{2}O$ threshold while the samples in the low-concentration groups did not. In contrast, a reverse relationship was observed between bulk flow rate and pressurization rate, such that the samples exposed to 0.5% at 0.7 $\frac{mL}{\min }$ had a significantly smaller pressurization rate than samples exposed to 0.5% at 0.3 $\frac{mL}{\min }$ (P = 0.029). These findings highlight the role of clot formation in PHH shunt obstruction and suggest avenues for improved catheter design or clinical management.