Sustained low efficiency dialysis should not be interrupted for performing transpulmonary thermodilution measurements

Treatment of multiple organ failure frequently requires enhanced hemodynamic monitoring. When renal replacement is indicated, it remains unclear whether transpulmonary thermodilution (TPTD) measurements are influenced by renal replacement therapy (RRT) and whether RRT should be paused for TPTD measurements. Our aim was therefore to investigate the effect of pausing RRT on TPTD results in two dialysis catheter locations.

In total, 62 TPTD measurements in 24 patients (APACHE: 32 ± 7 [mean ± standard deviation (SD)]) were performed using the PiCCO™ system (Pulsion, Germany). Patients were treated with sustained low efficiency dialysis (SLED; Genius™ system, Fresenius, Germany) as RRT. Measurements were taken during ongoing hemodialysis (HD, HDO), during paused HD (HDP) and immediately after termination of HD and blood restitution (HDT). Dialysis catheters were placed either in the superior vena cava (SVC, 19 times) or in the inferior vena cava (IVC, 5 times). Statistical analysis was performed to assess the effects of the measurement setting, SLED (blood flow rate) and the catheter location, on cardiac index (CI), global end-diastolic volume index (GEDVI) and extravascular lung water index (EVLWI) as measured by TPTD. Multilevel models were used for the analysis due to the triplicate measurements and due to 12 out of 19 SVC and 2 out of 5 IVC patients having more than one TPTD measured.

CI and GEDVI were significantly higher at time point HDP compared to both HDO and HDT. In contrast, values for EVLWI were lower at HDP when compared to HDO and HDT. These findings were independent of the site of dialysis catheter insertion and blood flow rate.

PiCCO™ measurements assessed at paused SLED significantly deviate from ongoing and terminated SLED. Therefore, the dialysis system should not be paused for measurements. TPTD measurements in patients with PiCCO monitoring seem sufficiently reliable during ongoing SLED as well as after its termination. An effect of dialysis catheter location (SVC vs IVC) and blood flow rate on PiCCO™ measurements could not be shown.