(153) Comparing Midline Versus Central Line Venous Pressures: Is This a New Tool in Resuscitation?

Introduction: Midlines (ML) are long peripheral intravenous catheters placed in an upper extremity above the antecubital space via the basilic, cephalic, or brachial veins. These provide safe and comfortable long-term vascular access for critically ill patients. Central venous pressures (CVP) are obtained from central venous catheters (CVC) and are often used as resuscitation parameters. Given the proximity of ML to the axillary vein, we set out to see if the MVP is comparable to the CVP.

Methods: This is a prospective observational study conducted in adult critical care patients. Inclusion criteria were patients with a CVC in the internal jugular or subclavian vein and a ML in an upper extremity as part of their ICU care. Using a standard pressure measuring system, venous pressure measurements were recorded from both catheters every 15 minutes over a 60-minute period. The values were analyzed for skewness and kurtosis to assess if the data were parametric. Means for the continuous measurements were compared using paired t testing. Spearman’s correlation was used to evaluate the monotonic relationship between the paired data. Demographic, clinical, and physiological data points were collected.

Results: In our preliminary analysis, we enrolled a total of 15 patients with 5 pressure measurements taken per patient (n = 75). The average patient age is 57.5 +/- 17.5 years. The mean SOFA and APACHE II scores are 8.7 +/- 3.2 and 19.9 +/- 7.5 respectively. The mean MVP and CVP were 8.4 +/- 5.7 mmHg and 10.1 +/- 5.8 mmHg respectively (p < 0.001). In the Bland Altman analysis, the mean bias was -1.7 +/- 3.4 mmHg with 95% limits of agreement -8.4 to 5.0 mmHg. There was a strong monotonic positive correlation between CVP and MVP values, with a Spearman’s coefficient of 0.81 (p < 0.001).

Conclusions: MVP as a correlate of CVP is an intriguing concept and its clinical utility remains to be seen. Our analysis showed significantly different mean pressures with large 95% limits of agreement. Spearman’s correlation showed a monotonic correlation between MVP and CVP, however, this does not provide information about the linear relationship between the pressures. Currently, our results do not support that MVP is interchangeable with CVP. Further investigation is ongoing.