Evaluation of using VBG instead of ABG in asthma exacerbation

Background- Arterial blood gas (ABG) is the gold standard for blood gas analysis. In asthma exacerbation severity evaluation, ABG is important; however, it is somehow difficult and potentially dangerous. Using venous blood gas (VBG) sampling is easier for less expert personnel, with minimal damage for patient. In this research, we want to compare ABG & VBG indexes in asthma exacerbation.

Method-This prospective diagnostic study was done with convenience sampling of 50 admitted children, 36 boys and 14 girls, between 3 and 6 years (mean 4.18) in pediatric emergency ward in Shariati hospital in Isfahan with asthma exacerbation during 2009 spring. They were normotensive and their temperature between 36-38.5. ABG sampling as routine in asthma management and VBG sampling along other venous tests were done without any excessive cost for patient. For both ABG and VBG test, we used an AVL compact1 analyzer few minutes after sampling. For data analysis, we utilized SPSS ver. 14.

Results-From 17 patient with PO₂< 60 in ABG, 100% had PO₂<60 in VBG.For 26 patients with PO₂>60, 80.77% had PO₂>60 in VBG and for seven with normal PO₂ in ABG 57.14% had normal value in VBG. For relationship between PO₂ in ABG and VBG P-value was 0.04.

From nine patients with PCO₂ > 45 in ABG, 66.67% had PCO₂ >45 in VBG.For 22 patients with PCO₂<45 in ABG, 63.4% had PCO₂<45 in VBG and from 19 patient with normal PCO₂ in ABG 100% had normal PCO₂ in VBG (P-value=0.004).

For O₂Sat. from nine patients with<91% in ABG, 100% had O₂Sat.<91 in VBG. From 31 patients with O2Sat. between 91-95 in ABG, 25.81% had O₂Sat. in same range in VBG. None of 10 patients with O₂Sat.>95 in ABG didn't have same in VBG. (P-value=0.005)        

For BE average arterial BE-2.3+/- 1.08 with range -5.6 to -1.1 and for venous BE average      -2.6+/-1.073 with range from-4.7 to-1.3 detected. Average arterial and venous BE was 0.03=/-1.46. (P-value=0.16)

Conclusion- There is strong regression between PO₂, PCO2 and O₂Sat.values in ABG and VBG samples so it suggests that VBG use instead of ABG in special situations in asthma exacerbations.