The initial assessment of acid-base status is usually based on the measurement of total CO₂ concentration ([TCO₂]) in venous blood, a surrogate for [HCO₃^–]. Previously, we posited that the reference limits of serum [TCO₂] in current use are too wide. Based on studies on the acid-base composition of normal subjects, we suggested that the reference limits of serum [TCO₂] at sea level be set at 23–30 mEq/L. To validate this proposal, we queried the University of California at Los Angeles (UCLA’s) Integrated Clinical and Research Data Repository, a database containing information on 4.5 million patients seen at UCLA from 2006 to the present. Criteria for inclusion included adults (18–40 years of age), who were free of disorders that could affect acid-base balance, were not taking medications that could affect acid-base balance, and were seen for a routine medical examination or immunization in the outpatient setting. The number of individuals who met the inclusion criteria (52% female and 48% male) was 28,480, with a mean age of 28.9 ± 5.1 years. The mean serum [TCO₂] level was slightly higher in males than females, 26.6 ± 2.16 mEq/L vs. 25.0 ± 2.11 mEq/L (p < 0.05). Ninety-one percent of patient values were within the proposed 23–30 mEq/L range and 61.7% were within the 24–27 mEq/L range. These findings validate our proposal that the reference range of serum [TCO₂] in venous blood at sea level be narrowed to 23–30 mEq/L. Subjects with serum [TCO₂] outside this range might require assessment with a venous blood gas to exclude the presence of clinically important acid-base disorders.

Immigration has been associated with crime. Whether immigrants are more involved than native-born persons in violent crime, in general, and in homicide, in particular, is less clear. The authors addressed the latter question by examining the 9,442 homicides from 1990 to 1994 in Los Angeles County. To avoid attributing to nativity the risk associated with age, gender, and ethnicity, population structure differences of the two groups were taken into account. Immigrants are at slightly higher risk of becoming a homicide victim than native-born persons. Offense rates are difficult to interpret because in 42.3% of the homicides, no suspect was identified; using data from known suspects, U.S.-born persons are 1.29 times more likely than foreign-born persons to commit homicide. The nature of the homicides of immigrants and by immigrants are, with some exceptions, substantially similar to the homicides of and by natives. More and better data are needed to inform policy.