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Abstract: FR-PO628

Pseudohypobicarbonatemia Induced by Severe Hypertriglyceridemia

Session Information

Category: Fluid and Electrolytes

  • 902 Fluid and Electrolytes: Clinical

Authors

  • Varghese, Vipin, University of Queensland - Ochsner Clinical School, New Orleans, Louisiana, United States
  • Velez, Juan Carlos Q., University of Queensland - Ochsner Clinical School, New Orleans, Louisiana, United States
Background

Reports of falsely low serum carbon dioxide (sCO2) concentration, i.e., pseudohypobicarbonatemia (psHypoHCO3-) in patients with severe hypertriglyceridemia (hyperTG) have emerged. This phenomenon results from lipid interference in some spectrophotometric analyzers. Our aim was to assess the magnitude and implications of psHypoHCO3- in a tertiary care hospital.

Methods

We searched for cases of serum triglycerides (TG) > 1000 mg/dL with a concomitant (measured <24 hrs apart) sCO2, between 2017 and 2018. We extracted those with sCO2 ≤ 12 mEq/L to focus on the more clinically relevant cases. Each measured sCO2 was compared with the calculated bicarbonate (HCO3-) from an arterial blood gas (ABG) obtained within 6 hrs of the venous blood draw. PsHypoHCO3- was defined as: erroneous HCO3- (eHCO3-) gap = (calculated HCO3- - measured sCO2) > 5 mEq/L.

Results

We identified 1698 events (652 patients) of TG > 1000 mg/dL and a sCO2 measured on the same day. TG inversely correlated with sCO2 (R=-0.38, p=0.00001). We found 179 events (59 patients) with sCO2 < 12 mEq/L. In 104 of those, an ABG was either not available or performed > 6 hrs apart from the venous blood draw. The remaining 75 events included 30 instances (11 patients) of true hypobicarbonatemia and 45 instances (24 patients) of psHypoHCO3-. Among those with psHypoHCO3-, the median values of sCO2, calculated HCO3-, anion gap and eHCO3- gap were 8 (<5 – 12), 20 (10 - 28), 21 (15 – 29) and 13 (5 – 19) mEq/L, respectively, whereas the median pH was 7.37 (7.14 - 7.56). True metabolic acidosis was either absent (42%) or spuriously magnified (58%). TG directly correlated with the eHCO3- gap (R=0.59, p=0.00004). Acute pancreatitis (56%) and diabetic ketoacidosis (38%) were the most common concomitant disorders but they did not fully account for the eHCO3- gap in the psHypoHCO3- cases. Additionally, unnecessary HCO3- therapy was initiated in 16% and serum lactate was measured in 80% of the psHypoHCO3- events (lactate was normal in 72%).

Conclusion

Severe hyperTG can lead to spuriously low sCO2. The degree of hyperTG correlates with the magnitude of PsHypoHCO3-. Clinicians and laboratory personnel should be aware of this phenomenon to prevent incorrect interpretation of acid-base status and medical mismanagement.