OBJECTIVES: To evaluate the base excess response during acute in vivo carbon dioxide changes. DESIGN: Secondary analysis of individual participant data from experimental studies. SETTING: Three experimental studies investigating the effect of acute in vivo respiratory derangements on acid-base variables. SUBJECTS: Eighty-nine (canine and human) carbon dioxide exposures. INTERVENTIONS: Arterial carbon dioxide titration through environmental chambers or mechanical ventilation. MEASUREMENTS AND MAIN RESULTS: For each subject, base excess was calculated using bicarbonate and pH using a fixed buffer power of 16.2. Analyses were performed using linear regression with arterial dioxide (predictor), base excess (outcome), and studies (interaction term). All studies show different baselines and slopes for base excess across carbon dioxide titrations methods. Individual subjects show substantial, and potentially clinically relevant, variations in base excess response across the hypercapnic range. Using a mathematical simulation of 10,000 buffer power coefficients we determined that a coefficient of 12.1 (95% CI, 9.1-15.1) instead of 16.2 facilitates a more conceptually appropriate in vivo base excess equation for general clinical application. CONCLUSIONS: In vivo changes in carbon dioxide leads to changes in base excess that may be clinically relevant for individual patients. A buffer power coefficient of 16.2 may not be appropriate in vivo and needs external validation in a range of clinical settings.

• Klíčová slova
• base deficit, buffer, carbon dioxide, metabolic, respiratory, resuscitation,
• MeSH
• acidobazická rovnováha * fyziologie   MeSH
• dospělí MeSH
• hyperkapnie patofyziologie   metabolismus   MeSH
• koncentrace vodíkových iontů MeSH
• lidé MeSH
• oxid uhličitý * metabolismus   MeSH
• poruchy acidobazické rovnováhy patofyziologie   metabolismus   MeSH
• psi MeSH
• umělé dýchání MeSH
• zvířata MeSH
• Check Tag
• dospělí MeSH
• lidé MeSH
• mužské pohlaví MeSH
• psi MeSH
• ženské pohlaví MeSH
• zvířata MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• oxid uhličitý * MeSH

It is commonly assumed that changes in plasma strong ion difference (SID) result in equal changes in whole blood base excess (BE). However, at varying pH, albumin ionic-binding and transerythrocyte shifts alter the SID of plasma without affecting that of whole blood (SIDwb), i.e., the BE. We hypothesize that, during acidosis, 1) an expected plasma SID (SIDexp) reflecting electrolytes redistribution can be predicted from albumin and hemoglobin's charges, and 2) only deviations in SID from SIDexp reflect changes in SIDwb, and therefore, BE. We equilibrated whole blood of 18 healthy subjects (albumin = 4.8 ± 0.2 g/dL, hemoglobin = 14.2 ± 0.9 g/dL), 18 septic patients with hypoalbuminemia and anemia (albumin = 3.1 ± 0.5 g/dL, hemoglobin = 10.4 ± 0.8 g/dL), and 10 healthy subjects after in vitro-induced isolated anemia (albumin = 5.0 ± 0.2 g/dL, hemoglobin = 7.0 ± 0.9 g/dL) with varying CO2 concentrations (2-20%). Plasma SID increased by 12.7 ± 2.1, 9.3 ± 1.7, and 7.8 ± 1.6 mEq/L, respectively (P < 0.01) and its agreement (bias[limits of agreement]) with SIDexp was strong: 0.5[-1.9; 2.8], 0.9[-0.9; 2.6], and 0.3[-1.4; 2.1] mEq/L, respectively. Separately, we added 7.5 or 15 mEq/L of lactic or hydrochloric acid to whole blood of 10 healthy subjects obtaining BE of -6.6 ± 1.7, -13.4 ± 2.2, -6.8 ± 1.8, and -13.6 ± 2.1 mEq/L, respectively. The agreement between ΔBE and ΔSID was weak (2.6[-1.1; 6.3] mEq/L), worsening with varying CO2 (2-20%): 6.3[-2.7; 15.2] mEq/L. Conversely, ΔSIDwb (the deviation of SID from SIDexp) agreed strongly with ΔBE at both constant and varying CO2: -0.1[-2.0; 1.7], and -0.5[-2.4; 1.5] mEq/L, respectively. We conclude that BE reflects only changes in plasma SID that are not expected from electrolytes redistribution, the latter being predictable from albumin and hemoglobin's charges.NEW & NOTEWORTHY This paper challenges the assumed equivalence between changes in plasma strong ion difference (SID) and whole blood base excess (BE) during in vitro acidosis. We highlight that redistribution of strong ions, in the form of albumin ionic-binding and transerythrocyte shifts, alters SID without affecting BE. We demonstrate that these expected SID alterations are predictable from albumin and hemoglobin's charges, or from the noncarbonic whole blood buffer value, allowing a better interpretation of SID and BE during in vitro acidosis.

• Klíčová slova
• albumin, hemoglobin, noncarbonic whole blood buffer value, plasma strong ion difference, whole blood base excess,
• MeSH
• acidobazická rovnováha MeSH
• acidóza * MeSH
• albuminy škodlivé účinky   MeSH
• anemie * MeSH
• elektrolyty MeSH
• hemoglobiny MeSH
• koncentrace vodíkových iontů MeSH
• lidé MeSH
• oxid uhličitý MeSH
• poruchy acidobazické rovnováhy * MeSH
• Check Tag
• lidé MeSH
• Publikační typ
• časopisecké články MeSH
• Názvy látek
• albuminy MeSH
• elektrolyty MeSH
• hemoglobiny MeSH
• oxid uhličitý MeSH