The importance of osmolality for intermittent catheterization of the urethra

The urethral trauma after catheterization with intermittent catheters was studied histologically using unconscious rabbits.

The study was performed at Astra Hässle, Mölndal, Sweden.

Fifteen rabbits were randomized into five groups (three rabbits in each group), one control group and four groups catheterized with four different LoFric catheters (Astra Tech, Mölndal, Sweden): (1) control (not catheterized); (2) salt coated (i.e. high osmolality catheters) with drainage eyes; (3) without salt (i.e. low osmolality catheters) and with eyes; (4) with salt coating but without drainage eyes; and (5) without neither salt coating nor drainage eyes. The urethral injuries were evaluated using a four graded histological scale.

The results showed that salt coated LoFric catheters gave less urethral trauma than LoFric catheters without salt. This was also supported by the significantly lower removal friction measured during withdrawal of the high osmolality catheters. No significant differences either in removal friction or in urethral trauma could be observed between LoFric catheters with or without drainage eyes.

It may be concluded that osmolality is one important factor (there might be others, like e.g. water binding ability) when comparing different hydrophilic catheters, in regards to removal friction and urethral trauma. Furthermore it is suggested that there is no difference in urethral trauma between catheters with eyes or without eyes. To minimize the risk of urethral trauma, high osmolality catheters are recommended, especially when the catheterization times are a few minutes or more.