We thank Dr. Omron for his letter regarding our recent article in CHEST (May 2007),1and we certainly agree that our observations regarding changes in baseline strong ion difference (SID) in analbuminemic rats have “practical implications for intensivists who apply physicochemical analysis at the bedside.” However, we are surprised that Dr. Omron has interpreted our comments to suggest that hypoalbuminemia can directly alter SID. Instead, we stated that “we speculate that the normal physiologic response to hypoalbuminemia is to lower the SIDa [apparent SID] ….” Indeed, these physiologic responses, or “secondary physiologic adaptations” as Dr. Omron refers to them, would necessarily involve changes in strong ions most likely via the action of the kidney. Changes in SID are well known to occur as a result of long-term changes in Pco2 but have not been described as a consequence of changes in weak acids such as albumin. Importantly, the metabolic component of acid-base balance, quantified by base excess, comprises both SID and total weak acids2; thus, as opposed to Dr. Omron’s assertion, hypoalbuminemia per se does significantly change the base excess (for every gram-per-deciliter change in albumin level, base excess changes by approximately 3 mEq).,2–3 This has important “practical implications” because if one considers these changes in SID to be “pathologic” instead of “physiologic,” one will be tempted to treat them. Our study did not and could not address therapy but we cannot share Dr. Omron’s certainty that changes in SID in the critically ill should always be treated. Instead, we would only offer the time-honored clinical advice that we should treat patients, their diseases, and symptoms, and not merely numbers.