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Matthew J. Martin, MD; Elizabeth FitzSullivan, BS; Ali Salim, MD; Thomas V. Berne, MD; Shirin Towfigh, MD

Arch Surg. 2005;140:745-751.

Hypothesis  Serum bicarbonate (HCO₃) measurement may accurately and reliably be substituted for the arterial base deficit (BD) assay in the surgical intensive care unit (ICU).

Design  Retrospective criterion standard analysis.

Setting  Surgical ICU in a tertiary care facility.

Patients  Consecutive sample of non–trauma-related surgical ICU admissions from January 1996 to January 2004 with simultaneously obtained serum HCO₃ and arterial BD levels.

Main Outcome Measures  Correlation between HCO₃ and BD at admission and during the ICU stay; predictive value of serum HCO₃ for significant metabolic acidosis and ICU mortality.

Results  The study included 2291 patients with 26 063 sets of paired laboratory data. The mean ± SD age was 52 ± 16 years and mean ICU stay was 5.8 ± 9.8 days. There were 174 ICU deaths (8%). Serum HCO₃ levels showed significant correlation with arterial BD levels both at admission (r = 0.85, R² = 0.72, P<.001) and throughout the ICU stay (r = 0.88, R² = 0.77, P<.001). Serum HCO₃ reliably predicted the presence of significant metabolic acidosis (BD > 5) with an area under the receiver operating characteristic curve (AUC) of 0.93 at admission and 0.95 overall (both P<.001), outperforming pH (AUC, 0.80), anion gap (AUC, 0.70), and lactate (AUC, 0.70). The admission serum HCO₃ level predicted ICU mortality as accurately as the admission arterial BD (AUCs of 0.68 and 0.70, respectively) and more accurately than either admission pH or anion gap.

Conclusions  Serum HCO₃ provides equivalent information to the arterial BD and may be used as an alternative predictive marker or guide to resuscitation. Low HCO₃ levels should prompt immediate metabolic acidosis evaluation and management.

Author Affiliations: Division of Trauma and Surgical Critical Care (Drs Martin and Salim and Ms FitzSullivan) and Division of Emergency Non-Trauma Surgery (Drs Berne and Towfigh), Department of Surgery, Keck School of Medicine, University of Southern California, and the Los Angeles County Hospital + USC Medical Center, Los Angeles.

RELATED LETTERS

Venous Bicarbonate Correlates Linearly With Arterial Base Deficit Only If pH Is Constant
Eugenio Lujan and Red Howard
Arch Surg. 2006;141(1):105.
EXTRACT | FULL TEXT  

Venous Bicarbonate Correlates Linearly With Arterial Base Deficit Only If pH Is Constant—Reply
Matthew J. Martin
Arch Surg. 2006;141(1):105.
EXTRACT | FULL TEXT  

THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Venous Bicarbonate Correlates Linearly With Arterial Base Deficit Only If pH Is Constant
Lujan and Howard
Arch Surg 2006;141:105-105.
FULL TEXT  

Venous Bicarbonate Correlates Linearly With Arterial Base Deficit Only If pH Is Constant--Reply
Martin
Arch Surg 2006;141:105-105.
FULL TEXT