The incidence and types of acid-base imbalance for critically ill patients in emergency

Objective: To explore the incidence and types of acid-base imbalance or disorder (ABD) for critically ill patients in emergency room. Methods: Clinical data of all critically ill patients managed in the resuscitation room were collected prospectively during the period from 1st December 2008 to 31st March 2009. Arterial and venous blood samples were taken simultaneously for blood gas analyses and serum electrolytes. Acid-base homeostasis or imbalance was judged according to the criteria. Results: A total of 766 cases were collected and the incidence of ABD was 97.3% (N=745). Simple acid-base disorder (SABD) was present in 149 cases (20.0%). Dual acid-base disorder (DABD) was present in 525 patients (70.5%) while triple acid-base disorder (TABD) was found in 71 patients (9.5%). After calculating the anion gap (AG), the incidence of metabolic acidosis increased from 72.2% (N=538) to 91.0% (N=678) and the rate of missed diagnosis for metabolic acidosis was 20.6% (140 out of 678 cases). Meanwhile, the incidence of TABD increased from 1.6% (N=12) to 9.5% (N=71) and the rate of missed diagnosis for TABD was 83.1% (59 out of 71 cases). Similar phenomenon was observed when potential bicarbonate was calculated. The incidence of TABD increased from 1.1% (N=8) to 9.5% (N=71) and the rate of missed diagnosis of TABD was 88.7% (63 out of 71 cases). Patients with TABD (77.9 +/- 10.7 years old) were older (P<0.01) than the groups of SABD and DABD. APACHE II scores and the incidence of multiple organ dysfunction syndrome (MODS) were significantly higher among TABD patients. Mortality of patients with TABD on the first, second, third and seventh days were 14.1%, 23.9%, 26.8% and 38.0% respectively and were significantly higher than SABD and DABD. Conclusion: The incidence of ABD in our group of critically ill patients was 97.3%. The commonest type of ABD was DABD. Calculating AG and potential bicarbonate could help us to uncover metabolic acidosis and TABD in time. Patients with TABD had a poorer prognosis. Age and APACHE II scores were key factors closely related to TABD. (Hong Kong j.emerg.med. 2012;19:13-17)