Effect of inline filtration of intravenous infusions on the incidence of thrombophlebitis.

The effect of inline filtration on the incidence of infusion phlebitis was examined in a community hospital. Two general surgical units, comparable in their patient populations, were studied during a one-month period. On one unit, an extension set with a 45 micrometer filter was attached to every i.v. catheter; no inline filtration was instituted on the second unit. The use or nonuse of a filter was not blinded. The filter was replaced every 24 hours or sooner if blockage occurred. A total of 49 patients (107 i.v.s) were studied in the group with filters and 40 patients (84 i.v.s) without filters. Phlebitis was graded on a scale of 0 to 4. The proportion of patients with phlebitis in the filter group was 86%; in the no-filter group, 75%. In the filter group, 67% of the catheterizations ended in phlebitis; in the no-filter group, 63%. Upon first catheterization, phlebitis developed in 63% of the filter group and 58% of the no-filter group. None of these differences was significant (p = 0.05). There was also no significant difference between the two groups in the severity of phlebitis and the incidence of phlebitis following the administration of irritating solutions containing cephalothin sodium or potassium chloride. Based on this study, the value of inline filtration in routine clinical conditions appears to be questionable.