BLOOD RECIRCULATION IN TEMPORARY CENTRAL CATHETERS FOR ACUTE HEMODIALYSIS

The low-flow method has been shown as a reliable evaluation of access recirculation. Few data is available on temporary central catheter blo od recirculation; results of 2% and 4% have been reported in subclavia n, 10% in 24 cm long femoral, and 18% in 15 cm long femoral catheters, mostly in indwelling catheters for chronic hemodialysis. The purpose of this prospective study was to evaluate blood recirculation in a lar ger number of recently inserted temporary intravenous catheters for ac ute hemodialysis, comparing subclavian and femoral sites. Fifty blood recirculation measurements were performed in 38 different temporary ce ntral venous dialysis catheters inserted in thirty-one critically ill patients from medical and surgical intensive care units presenting acu te renal failure supported by intermittent hemodialysis. All the cathe ters used were well-functioning 11.5 French dual lumen Quinton of 13.5 or 19.5 cm length. Catheters presenting mechanical dysfunction, which did not allow a blood flow rate of 300 ml/min or for which lines had to be reversed were excluded from the analysis. Access blood recircula tion was measured shortly after catheter insertion according to the lo w flow method applied after the first 30 minutes of hemodialysis at a blood flow rate of 300 ml/min. Mean blood recirculation for the 50 mea surements was 10.3 +/- 9.2%. It was significantly higher in the 26 fem oral catheters than in the 24 subclavian catheters, reaching respectiv e means of 16.1 +/- 9.1% and 4.1 +/- 3.6% (p = 0.0001). Blood recircul ation rate was not different between 13.5 cm and 19.5 cm long subclavi an catheters (3.0 +/- 2.6%, n = 13, versus 5.4 +/- 4.3%, n = 11, respe ctively), but was significantly higher in 13.5 cm than in 19.5 cm long femoral catheters (22.8 +/- 9.1%, n = 9, versus 12.6 +/- 6.9%, n = 17 ) (p = 0.004). Blood recirculation was measured on two separate occasi ons in 12 catheters randomly selected (5 femoral and 7 subclavian cath eters); the obtained results were reproducible with a mean difference of only 2.1 +/- 1.8% between the two measurements and a correlation of 0.96. The mean time elapsed between catheter insertion and recirculat ion assessment was 2.2 +/- 3.1 days and was similar for femoral and su bclavian catheters. No correlation was found between the percentage of recirculation and the arterial and venous resistances recorded during dialysis session or with the time from catheter insertion. Mean urea reduction ratio (URR) for the 50 dialysis sessions was 57.8 +/- 13.0%. It was significantly higher for sessions performed with subclavian th an with femoral catheters (62.5 +/- 10.9%, n = 24, versus 54.5 +/- 14. 2%, n = 26) (p = 0.03). In conclusion, the expected blood recirculatio n in well-functioning and recently inserted temporary dialysis cathete rs is under 5% for subclavian, over 12% in 19.5 cm femoral, and over 2 2% in shorter 13.5 cm femoral catheters at a blood flow rate of 300 ml /min. The consequently reduced dialysis efficiency with femoral cathet ers is another factor to be considered in the choice of a site for tem porary dialysis catheter insertion in acute renal failure patients, pa rticularly when dialysis dose delivery is a priority, such as intoxica tion cases treated by extracorporeal therapy.