Early detection and simplified management of obstructed Hickman and Broviac catheters

Thrombotic occlusion of Hickman and Broviac central venous catheters is a serious obstacle to their long-term use. Because resistance to flow (R) through a catheter of lumen radius, r, is proportional to 1/r4, we hypothesized that measurement of R would provide an objective and sensitive monitor for partial occlusions. Our measurements showed that median R at a flow of 17 mL/min was 0.7 cmH2O/mL/min in normally functioning Hickman catheters, and 4.1 cmH2O/mL/min in Broviac catheters. In obstructed catheters, which by subjective standards resisted flushing or blood withdrawal, median R was 3.0 cmH2O/mL/min for Hickman and 5.6 cmH2O/mL/min for Broviac catheters, representing significant increases. In a series of obstructed lines in which urokinase was administered, R decreased from 7.7 to 4.5 in Hickman catheters and from 5.6 to 4.2 in obstructed Broviac catheters. The elevated resistance in Hickman catheters after urokinase suggested that residual catheter obstruction was present even though catheter function returned to normal. Elevated R was seen with abnormal venograms in seven of 13 patients. Four patients had normal R values and abnormal venograms, and two patients had elevated R values with normal venograms. Measurement of resistance in Hickman and Broviac catheters provides a simple technique that can supplement or replace venography in the serial assessment and treatment of partial obstruction.