Mixing studies during intracarotid artery infusions in an in vitro model

Sporadic instances of retinal damage and of focal brain toxicity have been observed following intracarotid artery infusions of chemotherapeutic agents (such as BCNU and cis-platinum) for the treatment of glioblastomas. The episodic nature of these toxicities is consistent with the possibility that the drug solutions were streaming from the catheter tip and, therefore, were not well mixed or not uniformly distributed in all branches distal to the catheter tip location. To test this hypothesis, an in vitro system was fabricated which included a transparent model of the human carotid artery and its major branches. These were furnished with pulsatile flow of a blood simulant. Dye solutions infused at several infusion rates through various types of catheters in both supraophthalmic and infraophthalmic positions were monitored and recorded on videotape and photographic film. The effluent streams from distal branches of the model were collected, and the relative concentrations of dye in each branch were determined spectrophotometrically. The results indicate that infusate streaming occurs at low infusion rates. In some cases, the concentration in a given branch can be at least five times the expected concentration. Similar occurrences of streaming in vivo could cause focal toxicity. Methods to improve mixing should be used during intra-arterial administration of drugs; these include increasing the infusion rates and improving catheter tip design.