Formic acid poisoning in a tertiary care center in South India: A 2-year retrospective analysis of clinical profile and predictors of mortality.

Background: Formic acid (FA), a common industrial compound, is used in the coagulation of rubber latex in Kerala, a state in southwestern India. Easy accessibility to FA in this region makes it available to be used for deliberate self-harm. However, the literature on intentional poisoning with FA is limited.

Study Objectives: To determine the patterns of presentation of patients with intentional ingestion of FA and to find the predictors of mortality. A secondary objective was to find the prevalence and predictors of long-term sequelae related to the event.

Methods: We performed a 2-year chart review of patients with acute intentional ingestion of FA. Symptoms, signs, outcomes and complications were recorded, and patients who survived the attempt were followed-up by telephone or personal interview to identify any complications after their discharge from the hospital.

Results: A total of 302 patients with acute formic acid ingestion were identified during the study period. The mortality rate was 35.4% (n = 107). Bowel perforation (n = 39), shock (n = 73), and tracheoesophageal fistula (n = 4) were associated with 100% mortality. Quantity of FA consumed (p < 0.001), consuming undiluted FA (p < 0.001), presenting symptoms of hypotension (p < 0.001), respiratory distress (p < 0.001), severe degree of burns (p = 0.020), hematemesis (p = 0.024), complications like metabolic acidosis (p < 0.001) and acute respiratory distress syndrome (p < 0.001) were found to have significant association with mortality. The prevalence of esophageal stricture (n = 98) was 50.2% among survivors and was the most common long-term sequela among the survivors. Stricture was significantly associated with hematemesis (p < 0.001) and melena (p < 0.001).

Conclusion: This study highlights the magnitude and ill-effects of self-harm caused by a strong corrosive, readily available due to very few restrictions in its distribution. Easy availability of FA needs to be curtailed by enforcing statutory limitations in this part of the world. Patients with hematemesis or melena after FA ingestion may be referred for early dilatation therapy in a setting where emergency endoscopic evaluation of all injured patients is not practical.