Study objective: To investigate the effects of streptokinase and deoxyribonuclease (DNase) on the viscosity of pus to assess whether the DNase in the old preparation of streptokinase-streptodornase used intrapleurally to treat empyema was contributing to easier drainage of pus compared with purified streptokinase.
Design: In vitro measurement of pus viscosity.
Patients: Pus from three patients with surgically drained soft tissue abscesses and from six patients with empyema thoracis of varying etiology was studied.
Interventions: Pus samples were incubated with saline solution as control and with streptokinase, streptokinase-streptodornase, human recombinant DNase, and a mixture of streptokinase and DNase in concentrations approximating those achieved in clinical practice.
Results: Purified streptokinase had little effect on pus viscosity, with a mean reduction of 11.1% in the surgical specimens and 1.7% in the empyema samples. Streptokinase-streptodornase reduced viscosity by a mean of 52.8% in the surgical samples and 94.8% in the empyema samples. Human recombinant DNase reduced viscosity by a mean of 32. 79% in surgical samples and 93.4% in empyema samples. Adding streptokinase to human recombinant DNase produced no further reduction in viscosity. Final viscosities in samples treated with DNase were very similar whatever the starting viscosity.
Conclusions: DNase significantly reduces pus viscosity, whereas streptokinase has little or no effect, and in empyema may work simply by breaking down loculations. Clinical studies should be undertaken to see if these in vitro changes produce clinical benefits. The simple viscometer devised for these experiments may also prove useful in other contexts.