How common are blood acid–base disturbances in critically ill emergency patients, and can extra calculations reveal missed complex cases?

Details

This prospective observational study aimed to determine the incidence and types of acid–base disorder (ABD) among critically ill emergency patients. Clinical data were collected from patients in a resuscitation room from December 1, 2008, to March 31, 2009. Both arterial and venous blood samples were collected for simultaneous arterial blood gas analysis and serum electrolyte testing, and the patients’ acid–base disorders were analyzed.

Of 766 cases, 745 (97.3%) had an ABD. Among those 745 cases, 149 (20.0%) had a simple acid–base disorder (SABD), 525 (70.5%) had a dual acid–base disorder (DABD), and 71 (9.5%) had a triple acid–base disorder (TABD).

After calculation of the anion gap (AG), the number of identified TABD cases increased from 12 to 71; the reported missed-diagnosis rate was 83.1% (59 cases). After calculation of potential HCO3−, the number increased from 8 to 71; the reported missed-diagnosis rate was 88.7% (63 cases).

Patients with TABD were older, at 77.9 ± 10.7 years, than patients in both the SABD and DABD groups (P < 0.01). Their APACHE II score (25.9 ± 7.1) and incidence of multiple organ dysfunction syndrome (MODS; 22.5%) were also higher than in those two groups (P < 0.01). Mortality in the TABD group on days 1, 2, 3, and 7 was 14.1%, 23.9%, 26.8%, and 38.0%, respectively, significantly higher than in the SABD and DABD groups (P < 0.05 or P < 0.01).

The authors concluded that ABD occurred in 97.3% of the cases and that calculating AG and potential HCO3− could help identify metabolic acidosis and TABD. They identified age and APACHE II score as key factors associated with poor prognosis in patients with TABD.

Keywords: Acid–base disorder; Anion gap; Potential HCO3−; Triple acid–base disorder.