Slide Presentations: Tuesday, October 25, 2011 |

Minding the Gap: A Comparison of the Albumin-Lactate-Phosphate Corrected Anion Gap (ALPCAG) to the Strong Ion Gap (SIG) FREE TO VIEW

Laurence Busse, MD; Lakhmir Chawla, MD; Rohan Panchamia, BS; Daisi Choi, BA; Ehsan Nobakht, MD; Ermira Brasha-Mitchell, MD; Michael Seneff, MD
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George Washington University, Washington, DC

Chest. 2011;140(4_MeetingAbstracts):1012A. doi:10.1378/chest.1112095
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PURPOSE: We sought to determine if the albumin-and-lactate-corrected anion gap (ALCAG) or the albumin-lactate-phosphate corrected anion gap (ALPCAG) could more easily approximate the strong ion gap (SIG), without the cumbersome calculation required for the SIG.

METHODS: We screened all patients admitted to the ICU of George Washington University over a 12-month period for those who had a simultaneously drawn electrolyte panel, albumin, mineral panel and blood gas with lactate. We then calculated AG, albumin corrected anion gap (ACAG), ALCAG, ALPCAG and the SIG. Demographic and relevant clinical data were also collected. These values were tested by Pearson correlation and Bland-Altman assessment.

RESULTS: 199 consecutive patients met the inclusion/exclusion criteria. The mean AG, ACAG, ALCAG, ALPCAG, and SIG were 7.3 ± 5.4, 12.1 ± 5.2, 13.6 ± 4.2, 7.5 ± 4.3, and 7.2 ± 3.7, respectively. ALPCAG and ALCAG were highly correlated with the SIG (0.831, p < 0.001 and 0.863, p < 0.001 respectively), and outperformed the AG, and ACAG (0.68, 0.69, respectively) with respect to correlation to the SIG. In Bland-Altman analysis, the ALPCAG more closely approximated the SIG with an ALPCAG-SIG difference of 1.4 ± 1.1 mmol/L.

CONCLUSIONS: The ALPCAG more accurately reflected the true value of the SIG. Since the ALPCAG is easily calculated, the ALPCAG can be used to make a primary assessment of the SIG with fewer variables, and without the need for a programmable calculator or blood gas. If the ALPCAG is abnormal, a formal calculation of the SIG should be undertaken in order to completely assess the acid-base status of a patient.

CLINICAL IMPLICATIONS: Critically ill patients often have complex acid-base disorders that would benefit from measurement of the SIG, but this done infrequently, in part due to the cumbersome nature of Stewart Approach. The ALPCAG is an easy-to-use to calculation with a value that appears to closely reflect the true value of the SIG. Use of the ALPCAG may assist in improving the more complete assessment of acid-base disorders in critically ill patients.

DISCLOSURE: The following authors have nothing to disclose: Laurence Busse, Lakhmir Chawla, Rohan Panchamia, Daisi Choi, Ehsan Nobakht, Ermira Brasha-Mitchell, Michael Seneff

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