Effect of prolonged infusion on vein calibre: a prospective study.

Infusion thrombophlebitis is common and is the principal limitation to intravenous nutrition (IVN) via a peripheral vein, yet its precise pathogenesis is unclear. Prospective observations were performed on patients in whom a hypertonic, acidic, nutritional emulsion was infused via fine-bore polyurethane catheters placed in peripheral veins. B mode ultrasound was used to determine vein calibre and proved to be a useful means for serial examination during intravenous infusion. Contrary to previous reports, no evidence of venospasm was observed. It is suggested that previous evidence of venoconstriction is erroneous and that other mechanisms are responsible for thrombophlebitis.