Arterial Blood gas (ABG) is useful in assessing ventilatory and metabolic status of a patient in Intensive care unit (ICU). In this study we determined the utility of sequential ABG in ICU.
Prospective observational study. Patients admitted to ICU during 9/22/07–10/19/07 who had 2 or more ABG in 24 hours period were enrolled. Demographics, data from ABG and management changes done after ABG were noted. ABG was part of daily investigations (Routine) or Physician-ordered was noted. ABG was scored 1 to 4 in increasing order of utility. Data was analyzed to find determinants of utility of ABG.
Forty-five patients from 24 to 88 years age were included. Four hundred ABG were given utility scores. 1) ABG and Age: Age 24 to 43 years had an average of 5.6 ABG per patient. Age 84+ years had 11.5 ABG per patient. The correlation coefficient was significant at p < 0.05. The rank correlation was 41% (p < 0.01). Physician ABG vs. Routine ABG: 26% of the Routine ABG had utility score 1 and did not provide significant benefit to the patient. 20% of Physician ABG had utility score 4. Acidosis Management: 144 ABG were ordered for patients with acidosis (pH < 7.3). Out of these, 81% were Physician ABG. 67% of these ABG had a utility score of 3 or 4. Marginal Utility of ABG: The marginal utility of ABG decreases as number per patient increase; 89% of all first ABG had utility of 3 or 4. The utility reduced there after. The negative correlation is p≪. 01. An alternate measure of correlation is p≪0.01.
Older patients get more ABG with decreasing marginal utility as more tests are done. ICU physicians order a large number of ABG done for acidosis: 67% of them had high utility scores. 26% of routine ABG had low utility.
This suggests a need to individualize routine ABG in older patients, especially if they have a prolonged ICU stay.
Seema Agarwal, No Financial Disclosure Information; No Product/Research Disclosure Information