Use of Serum Bicarbonate Measurement in Place of Arterial Base Deficit in the Surgical Intensive Care Unit

Abstract

Hypothesis: Serum bicarbonate (HCO 3) 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 HCO 3 and arterial BD levels. Main Outcome Measures: Correlation between HCO 3 and BD at admission and during the ICU stay; predictive value of serum HCO 3 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 HCO 3 levels showed significant correlation with arterial BD levels both at admission (r=0.85, R 2 =0.72, PϽ.001) and throughout the ICU stay (r=0.88, R 2 =0.77, PϽ.001). Serum HCO 3 reliably predicted the presence of significant metabolic acidosis (BDϾ5) with an area under the receiver operating characteristic curve (AUC) of 0.93 at admission and 0.95 overall (both PϽ.001), outperforming pH (AUC, 0.80), anion gap (AUC, 0.70), and lactate (AUC, 0.70). The admission serum HCO 3 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 HCO 3 provides equivalent information to the arterial BD and may be used as an alternative predictive marker or guide to resuscitation. Low HCO 3 levels should prompt immediate metabolic acidosis evaluation and management.

The effect of pH versus base deficit on organ failure in trauma patients

“…BD is a calculated value, based on measured values of bicarbonate and pH. BD calculations can be affected by concentrations of weak acids, primarily hemoglobin and albumin [9,11,12]. It is well known that albumin, hemoglobin, and other weak acids undergo rapid changes in the injured patient during the first 24 h [12].…”

“…BD calculations can be affected by concentrations of weak acids, primarily hemoglobin and albumin [9,11,12]. It is well known that albumin, hemoglobin, and other weak acids undergo rapid changes in the injured patient during the first 24 h [12]. In contrast, pH is a direct physical measurement, reflecting the competing effects of anaerobic metabolism and compensatory circulating buffers and respiration.…”

Development of the Post Cardiac Surgery (POCAS) prognostic score

“…Traditional hemodynamic markers, such as blood pressure, have been used to guide resuscitation in case of shock. Lactate and bicarbonate have been demonstrated to be metabolic indicators of the severity of shock and related to mortality [15,32,33]. MAP is a key clinical factor in the scoring system and its values can be altered during patient transfer from the operating room to the ICU.…”

Bicarbonate can improve the prognostic value of the MELD score for critically ill patients with cirrhosis

“…The serum HCO 3 level at admission can also predict ICU mortality as accurately as the admission arterial BD and more accurately than either admission pH or the anion gap. 25,26 It is noteworthy that arterial pH is stabilized by excretion or retention of acid or alkali through control of the plasma bicarbonate level by the kidney or the control of PaCO 2 by the central nervous system and respiratory system; and AKI, usually a result of metabolic acidosis, is a common event in critically ill patients with cirrhosis. 27 Serum sodium concentration has been recognized as an important prognostic factor in patients with cirrhosis and is associated with the hepatorenal syndrome, ascites, and death from liver disease.…”