35 DUNN method versus weight based formulae to estimate umbilical arterial and venous catheters position

Abstract

Abstract Background Umbilical arterial catheters (UAC) and umbilical venous catheters (UVC) are frequently used in infants admitted to neonatal intensive care units (NICU). Dunn method (DM) was used in our NICU to calculate length of insertion of UAC/UVC until July 2018, before the adoption of the weight-based formulae (WBF). Objectives Our primary objective was to compare both methods in regards to correct position of UAC/UVC on first attempt. As a secondary objective we assessed the correlation between the tip position of catheters in anteroposterior radiographies (APR) and lateral radiographies (LatR). Design/Methods This is a retrospective cohort study of infants with UAC/UVC inserted in the NICU from 2017-2019. Charts were reviewed for demographic data and catheters position in APR and LatR. The position was considered appropriate if the tip was between thoracic vertebral level (Th)6 and Th9 on APR for UAC and at Th8-Th9 on APR for UVC. Length of insertion of catheters was calculated via DM in one group and WBF in the other. Secondarily, we compared position of catheters on APR and LatR. For statistical analysis we used t student test for continuous data, Chi square test for categorical data and Pearson r for coefficient of correlation(r). Results Among 462 infants with UAC/UVC placed, demographic characteristics in both groups were similar (Table 1). There was a good correlation between APR and LatR for the assessment of UVC and UAC position. Appropriate position on first attempt for UAC was 60% (49/82) with Dunn method and 66% (74/112) with WBF (p=0.67). Appropriate position on first attempt in UVC insertion beyond liver was 36% (46/127) using Dunn method and 43% (67/157) with WBF (p=0.47). Rate of low positioned UVC was significantly lower using WBF compared to Dunn method: 3%(5/157) vs 9% (11/127), (p=0.04). Position of catheters on APR and LatR were well correlated for UVC (n=146, r=0.87, p<0.001) and UAC (n=62, r=0.82, p<0.001). Conclusion No difference was observed for appropriate position of UAC and UVC on first attempt using DM versus WBF. There was significantly less low positioned UVCs with WBF.