A head to head evaluation of 8 biochemical scanning tools for unmeasured ions

Morgan, Thomas J., Anstey, Chris M. and Wolf, Matthew B. (2016) A head to head evaluation of 8 biochemical scanning tools for unmeasured ions. Journal of Clinical Monitoring and Computing, 1-9. doi:10.1007/s10877-016-9861-5

Author Morgan, Thomas J.
Anstey, Chris M.
Wolf, Matthew B.
Title A head to head evaluation of 8 biochemical scanning tools for unmeasured ions
Journal name Journal of Clinical Monitoring and Computing   Check publisher's open access policy
ISSN 1573-2614
Publication date 2016-04-12
Year available 2016
Sub-type Article (original research)
DOI 10.1007/s10877-016-9861-5
Open Access Status Not yet assessed
Start page 1
End page 9
Total pages 9
Place of publication Dordrecht, Netherlands
Publisher Springer Netherlands
Collection year 2017
Language eng
Abstract We aimed to evaluate the sensitivity and specificity of 8 biochemical scanning tools in signalling the presence of unmeasured anions. We used blood gas and biochemical data from 15 patients during and after cardio-pulmonary bypass. Sampling time-points were pre-bypass (T1), 2 min post equilibration with priming fluid containing acetate and gluconate anions (T2), late bypass (T3) and 4 h after surgery (T4). We calculated the anion gap (AG), albumin—corrected anion gap (AGc), whole blood base excess (BE) gap, plasma BE gap, standard BE gap and the strong ion gap (SIG), plus 2 new indices—the unmeasured ion index (UIX) and unmeasured plasma anions according to the interstitial, plasma and erythrocyte acid–base model (IPEua). Total measured plasma concentrations of acetate and gluconate [XA] were proxies for unmeasured plasma anions. [XA] values (mmol/L) were 1.41 (0.87) at T1, 11.73 (3.28) at T2, 4.80 (1.49) at T3 and 1.36 (0.73) at T4. Corresponding [albumin] values (g/L) were 32.3 (2.0), 19.8 (2.6), 21.3 (2.5) and 29.1 (2.3) respectively. Only the AG failed to increase significantly at T2 in response to a mean [XA] surge of >10 mEq/L. At an [XA] threshold of 6 mEq/L, areas under receiver –operator characteristic curves in rank order were IPEua and UIX (0.88 and 0.87 respectively), SIG (0.81), AGc (0.79), standard BE gap (0.77), plasma BE gap (0.71), BE gap (0.70) and AG (0.59). Similar ranking hierarchies applied to positive and negative predictive values. We conclude that during acute hemodilution UIX and IPEua are superior to the anion gap (with and without albumin correction) and 4 other indices as scanning tools for unmeasured anions.
Keyword Biochemical scanning tools
Cardio-pulmonary bypass
IPE model
Unmeasured anions
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

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