Vein Can Often Replace Artery for Blood Gas Analysis

By Will Boggs MD

September 08, 2020

NEW YORK (Reuters Health) - Venous sampling for blood-gas analysis, which is less painful than arterial sampling, should be the preferred approach as long as knowledge of the partial pressure of oxygen (PaO2) or precise lactate level isn't mandatory, according to the authors of an open-label randomized study.

Dr. Damien Roux of Hopital Louis-Mourier, in Montmorency, and the University of Paris, France, and colleagues compared venous and arterial sampling in terms of pain at the time of blood draw in the emergency department in their study of 113 patients with normal pulse oximetry while breathing room air.

Patients reported their pain within three minutes of the blood draw using a visual analog scale that ranged from 0 mm (absence of pain) to 100 mm (worst pain imaginable).

The mean maximal pain reported was significantly lower among those undergoing venous blood sampling (22.6 mm) than among those undergoing arterial blood sampling (40.5 mm), the researchers report in the Emergency Medicine Journal.

Rates of success on the first sampling attempt did not differ significantly between venous (91%) and arterial (80%) sampling groups (P=0.073). But blood sampling for venous blood gas was more frequently assessed by the nurse as easy (69% vs. 44%, P=0.02).

Physician satisfaction with the usefulness of the information from the blood gas did not differ between the groups.

"We believe venous blood gas should be the standard of care when blood gas analysis is required in emergency departments," the authors conclude. "Arterial blood gas sampling should be reserved for situations where knowledge of the partial pressure of oxygen or precise lactate level is mandatory."

Dr. Hadi Mirfazaelian of Tehran University of Medical Sciences, who earlier reported that a vapocoolant spray did not reduce the pain of arterial puncture, told Reuters Health by email, "The most important point for me is that patients at risk of hypoxia were excluded. This leaves us with patients who underwent sampling for acid-base problem diagnosis."

"I am still waiting for studies that support replacing arterial blood gas with pulse oximeter plus venous blood gas," he added.

Dr. Roux did not respond to a request for comments.

SOURCE: Emergency Medicine Journal, online August 5, 2020.