Normal saline wound dressing - is it really normal?

Gauze swabs soaked in normal saline are frequently used as dressing on open wounds. Their exact mechanism of action is not known. This study was desig ned to assess the hypothesis that normal saline dressings act in part as an osmotic dressing. Ten patients had skin ulcers (n = 10) dressed with norma l saline soaked sponges. Acting as controls (n = 10) identical sponges were placed upon intact skin. The sponge fluid osmolarity and electrolyte conce ntrations were serially assayed to test our hypothesis. In the control grou p, the osmolarity, sodium and chloride concentrations increased with time a s a result of evaporation, altering it from an isotonic to a hypertonic dre ssing. However in the ulcer group, the osmolarity, sodium and chloride conc entrations in the sponge fluid remained relatively isotonic with time. This result is statistically significant (P < 0.05). We postulate that, as a re sult of evaporation, the sponge dressing increases its tonicity. This draws fluid from the wound into the dressing so that a dynamic equilibrium occur s and the sponge dressing regains isotonicity. The dressing remains functio nal provided that the wound fluid is absorbed freely from the wound. This p rocess is terminated when either the dressing completely absorbs the wound fluid or the dressing dries out. The latter often occurs prematurely in a c ontaminated wound or in a wound where exudate forms a non-permeable barrier which prevents osmosis and allows the remaining water in the dressing to e vaporate completely This correlates with the observation in clinical practi ce that for maximum efficacy the dressing should be changed regularly (C) 2 000 The British Association of Plastic Surgeons.