The importance of osmolality in hydrophilic urethral catheters: a crossover study

The longterm use of clean intermittent self catheterisation as an option for bladder management in the care of spinal cord injury patients has shown the possible risk of urethral trauma and chronic infections being developed over time. The basic properties of the catheters being used need to be evaluated. In this crossover study of 14 male spinal cord injury patients, two commercial hydrophilic catheters were compared, as to the maximum friction force during the removal of the catheters after bladder emptying. The friction force, measured by a dynamometer twice daily, showed significant lower values for LoFric (0.87/0.84 N) than for EsiCath/Conveen (1.38/1.27 N). Sticking to the urethral epithelium was reported three times (two patients) with the LoFric catheter, and 42 times (nine patients) with the EasiCath catheter. Osmolality of the outer layer of the catheters was measured using a freezing-point reduction technique. The greater than 10 times higher osmolality (approximately 900 mOsm/kg) of the Lofric catheter may explain the results.