Do you think CO2 from a CBG is just as good as an ABG for assessing ventilation???

mrRT

Capillary and arterial blood gases in hemorrhagic shock: A comparative study.

Laboratory Investigation

Pediatric Critical Care Medicine. 3(4):375-377, October 2002.
Ueta, Ikuya MD; Jacobs, Brian R. MD
Abstract:
Objectives: To determine whether capillary blood gas samples accurately reflect the information obtained from arterial blood gas samples in a porcine hemorrhagic shock model.

Design: Randomized prospective study.

Setting: Animal research laboratory at a children's hospital.

Subjects: Fifteen adult Yorkshire pigs.

Interventions: Tracheally intubated, ventilated, and anesthetized pigs were randomly assigned to either a control group (n = 10) or a hemorrhagic shock group (n = 5). After instrumentation, the hemorrhagic shock group underwent a 40-mL/kg hemorrhage over 2 hrs, while the control group did not. Animals were then monitored over a 3-hr period.

Measurements and Main Results: Simultaneous arterial blood gas and capillary blood gas samples were obtained from each animal by using standardized technique. Capillary blood gas pH accurately predicted arterial blood gas pH in both control and hemorrhagic shock groups (r = .94, p < .01, and r = .78, p < .01, respectively). Bland-Altman analysis revealed a mean difference between arterial blood gas pH and capillary blood gas pH of 0.016 (95% limit of agreement, +/-0.037) in the control group vs. a mean difference between arterial blood gas pH and capillary blood gas pH of 0.075 (95% limit of agreement, +/-0.142) in the hemorrhagic shock group. Capillary blood gas Pco2 accurately predicted arterial blood gas Pco2 in the control group but not in the hemorrhagic shock group (r = .80, p < .01, and r = .13, p = .41, respectively). By Bland-Altman analysis, the mean difference between arterial blood gas Pco2 and capillary blood gas Pco2 was 3.9, with a 95% limit of agreement of +/-3.61 in the control group. In the hemorrhagic shock group, the mean difference between arterial blood gas Pco2 and capillary blood gas Pco2 was 11.7 with a 95% limit of agreement of +/-38.8. Hemorrhagic shock group capillary blood gas samples significantly overestimated Pco2 ([DELTA] = 11.7, p < .01) and underestimated pH ([DELTA] = 0.075, p < .01) compared with arterial blood gas samples.

Conclusions: Capillary blood gas samples are poor predictors of Pco2 and pH in porcine hemorrhagic shock. These findings should be taken into account when capillary blood gas samples are used in the monitoring and management of subjects diagnosed with shock.


Capillary blood gases in a pediatric intensive care unit.

Pediatric Critical Care

Critical Care Medicine. 28(1):224-226, January 2000.
Escalante-Kanashiro, Raffo MD; Tantalean-Da-Fieno, Jose MD
Abstract:
Objective: To determine if samples obtained from arterial and capillary sources are comparable in children with diverse pathologic conditions during their stay in a pediatric intensive care unit.

Study Design: Prospective, descriptive study in patients admitted to a multidisciplinary pediatric intensive care unit.

Interventions: Seventy-five simultaneous paired samples (arterial and capillary) were obtained from patients with different degrees of capillary reperfusion, hemodynamic stability, blood pressure, and temperature. Both samples were analyzed <=5 mins after collection.

Measurements and Main Results: The average correlations between arterial and capillary samples were 0.87 for pH, 0.86 for CO2, and 0.65 for oxygen. Neither poor perfusion nor low temperature altered the correlation for pH or CO2. The only condition that significantly affected the correlation was hypotension.

Conclusion: Capillary blood sampling is a useful alternative to gasometric evaluation of critically ill children, even in the presence of hypothermia or hypoperfusion, provided that hypotension is not present.

Just a couple of quick abstracts on CBG's vs ABG's. I personally think CBG can show ventilation but not accuratly show oxygenation.

Thank you!
I was just wondering since we only use CBGs to evaluate ventilation in our pts. I was a little nervous about relying on CBGs only, but it sounds like this is an accurate measurement of ventilation compared to ABGS.

mrRT