FC 025ACID BASE DISORDERS IN COVID-19
Authors: Alfano Gaetano , Ferrari Annachiara , Fontana Francesco , Mori Giacomo , Magistroni Riccardo , Guaraldi Giovanni , Cappelli Gianni 
Published: May 2021

Abstract

Background and Aims
Acid-base disorders are common in severely ill patients and reflect the severity of the underlying pathologic process. The incidence and effects of acid-base derangement in COVID-19 patients have been poorly evaluated until now. Tropism of the virus for the lungs and kidneys may theoretically lead to frequent acid-base alterations due to pneumonia and kidney injury, respectively. To verify the derangement of acid-base disorders in COVID-19, we investigated the distribution and the impact of acid-base disorders on the survival of symptomatic patients with a diagnosis of COVID-19.

Method
We retrospectively collected data from electronic charts of all COVID-19 patients hospitalized at the University Hospital of Modena from 4 March to 20 June 2020.
Arterial blood gas (ABG) analysis was required to monitor pulmonary gas exchange and acid-base status. A pH of less than 7.37 was categorized as acidemia and a pH of more than 7.42 was categorized as alkalemia.
211 patients were included in the study population. In patients with multiple ABG analyses, we selected only the first measurement.

Results
The estimated mean age of the population was 64.7 ±15,3 years with a high predominance of males (71.6%). Half of the population referred dyspnea and 61.4% at physical examination. Most patients (82.6%) were on oxygen therapy when ABG analysis was performed. Overall, ABG analyses revealed acute respiratory compromise manifesting with a low arterial partial pressure of oxygen (P02, 70.2±25.1 mmHg), oxygen saturation (SO2, 92%) and a mild reduction of PO2/FiO2 ratio (231±129).
Acid-base disturbance was found in the 79.7% of the patients, and contrary to our expectation, metabolic alkalosis (33.6%) was the main alteration followed by respiratory alkalosis (30.3%), combined alkalosis (9.4%) respiratory acidosis (3.3%) metabolic acidosis (2.8%) and other compensated acid-base disturbances (3.6%). ANOVA with post hoc Tukey, revealed statistically significant differences in age, sex, serum level of K, Na, bicarbonate, creatinine of PCO2, PO2/FiO2 ratio, CKD, symptoms (caught, diarrhea) and fatality rate among groups.
Metabolic acidosis was associated with death (HR=8.2; CI 95%, 1,93-32,39; P&lt;0.004), after adjustment for lung injury (PaO2/FiO2 ratio) tissue hypoperfusion (lactate) and renal involvement (estimated as GFR&lt; 60 ml/min or development of acute kidney injury), Pathological pH (alkalosis or acidosis), variations of PCO2 or hypobicarbonatemia were not associated with mortality in our study population. Metabolic acidosis occurred in patients with a mean creatinine of 4.5±4.5 mg/dl. Notably, 33.3% of patients were on hemodialysis, 33.3% developed COVID-19-associated acute kidney injury and 33.3% had a GFR &lt;60 ml/min. Patients with metabolic acidosis had the highest death-fatality rate (100%) after 7±5.6 days from admission, 50% died of acute respiratory distress syndrome and 50% of septic shock.

Conclusion
In conclusion, all kinds of acid-base alterations were found in patients with COVID-19. Metabolic and respiratory alkalosis were the most common acid-base disorders, whereas metabolic acidosis was the only acid-base disturbance associate with poor outcome in our cohort of patients.