Disturbances of blood-flow velocity in the dorsal veins of the hand after vein cannulation and cannula fixation in the anaesthetised patient.

Modifications of the mean blood-flow velocity in the dorsal veins of the hand were assessed semi-quantitatively with continuous wave (CW) Doppler equipment in 32 anaesthetised patients (17 men and 15 women), 23-78 (median = 56) years of age, before and after venous catheterisation with cannula fixation to the skin. Cannulation of the vein caused a 48% reduction in the mean blood-flow velocity and made it impossible to detect any flow with the equipment used in 22% of the patients. A 10% further reduction in the mean blood-flow velocity and in the number of subjects with undetectable blood flow was observed after fixation of the cannulae. Age, small vein diameter, and hyperventilation (end-tidal carbon dioxide less than or equal to 3.5 volume % appeared to be significant factors reducing blood-flow velocities in the cannulated veins. It is concluded that venous catheterisation and fixation of the cannula induce a significant reduction in the blood-flow velocity.