MO002: Are there Differences in the Results of the Venous Blood Gas Test According to the Origin of the Sample?
Authors: María Paloma Flores Paloma , María Eugenia Palacios Gómez , Nuria García Pablos , Manuel David Sánchez Martos , Javier Ramírez Santos , Francisco Javier Gonzalez Martinez 
Published: May 2022

Abstract

BACKGROUND AND AIMS
Currently, hospital haemodialysis units present a high percentage of patients with central venous catheters as the preferred access for haemodialysis treatment, compared with arteriovenous fistula. In most cases, this situation is derived from the characteristics of the patients in these units: patients with high comorbidity, vascular exhaustion and age, among others. For this reason, in the face of a large population with these characteristics, we decided to assess whether there were differences in the blood gas values obtained depending on the place of origin of the sample extraction: from the catheter itself or from the peripheral line.

OBJECTIVES
Estimate if there are differences in the results obtained in venous blood gases extracted from a venous catheter compared with those obtained through peripheral venipuncture.

METHOD
Two simultaneous cohort studies were carried out to assess the analytical results of venous blood gas according to whether the origin of the sample was from a central venous catheter or fistula, and a second study that compared the results of patients with central venous catheters to those obtained peripherally on the same day and time.
The sample consisted of 104 patients undergoing renal replacement treatment in the Haemodialysis Unit of Torrecardenas Hospital in Almería.
Hypothesis:
(1) There are differences between blood gases obtained from patients with AVF and vascular catheter.
(2) There are differences between the blood gases of the patients depending on whether they are extracted from a vascular catheter or peripheral venipuncture.
In the first case, a hypothesis contrast test was carried out to compare the means in independent samples. To verify the second hypothesis, a comparison of means for paired samples was made, for the gasometric results depending on whether they came from a catheter or peripheral puncture. IBM's SPSS software was used to manage these data.

RESULTS
Of the 104 patients, there were 68 men (65.38%) and 36 women (34.62%) with a mean age of 63.83 years. Permanent catheter bearers in 49.03% of cases (51 patients). Six patients were excluded from whom no valid sample was obtained.
The test carried out did not show significance for the first hypothesis raised, and differences in blood gas measurements between patients with AVF and vascular catheter could not be accepted.
The difference between the pH, pHCO3 and pCO2 of the blood gases was significant depending on whether they came from a vascular catheter or peripheral venipuncture.

CONCLUSION
Given the data obtained, we can conclude that there are no differences in the analytical results of the samples obtained from the catheter or from the fistula, which both represent a reliable method when obtaining the samples in these patients, eliminating traumatic venipuncture. However, significant differences were found within the same subjects depending on whether the sample was obtained.