ABG: Opioid effect

Opioid consumption produces a respiratory acidosis (accumulation of CO₂). Chronic opioid users may excrete Cl- (classically thought of as “retaining bicarbonate” although in reality is is the loss of the strong anion that matters from a pH perspective, see the work of Kellum J re: strong ion difference and its relationship to pH) in an effort to compensate and will therefore exhibit an elevated serum [HCO3-].

For rules on expected compensation and additional information, see Acid Base link on this page.