Acid base disorders in patients with COVID-19

Acid-base derangement has been poorly described in patients with coronavirus disease 2019 (COVID-19). Considering the high prevalence of pneumonia and kidneys injury in COVID-19, frequent acid-base alterations are expected in patients admitted with SARS-Cov-2 infection. The study aimed to assess the prevalence of acid-base disorders in symptomatic patients with a diagnosis of COVID-19.

The retrospective study enrolled COVID-19 patients hospitalized at the University Hospital of Modena from 4 March to 20 June 2020. Baseline arterial blood gas (ABG) analysis was collected in 211 patients. In subjects with multiple ABG analysis, we selected only the first measurement. A pH of less than 7.37 was categorized as acidemia and a pH of more than 7.43 was categorized as alkalemia.

ABG analyses revealed a low arterial partial pressure of oxygen (PO₂, 70.2 ± 25.1 mmHg), oxygen saturation (SO₂, 92%) and a mild reduction of PO₂/FiO₂ ratio (231 ± 129). Acid-base alterations were found in 79.7% of the patient. 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%). All six patients with metabolic acidosis died at the end of the follow-up.

Variations of pH occurred in the majority (79.7%) of patients admitted with COVID-19. The patients experienced all the type of acid-base disorders, notably metabolic and respiratory alkalosis were the most common alterations in this group of patients.