Acid-Base Status as an Early Predictor of Delayed Neuropsychiatric Sequelae after Acute Carbon Monoxide Poisoning.

Background: Carbon monoxide toxicity is one of the leading causes of mortality and morbidity worldwide, which is called the "silent killer.” About 15–40% of CO-poisoned patients may experience delayed neurological syndrome (DNS). Accurate identification of patients at risk of developing DNS might be helpful to prevent DNS and allow a follow-up. Aim of the work: The study aimed to investigate acid-base status as a predictor of DNS occurrence after acute CO poisoning. Patients and methods: This study enrolled 50 patients with acute CO poisoning admitted to Tanta Poison Control Center. Collected data included socio-demographics, toxicological history, vital signs, severity, and laboratory investigations. Results: DNS developed in 29 patients (58%). Patients who developed DNS were significantly older with median of 29.0, IQR (22.0- 39.0) and had longer CO exposure with median of 3.0, IQR (1.0-4.0) and presentation delay times with median of 4.75, IQR (2.0-7.0). They also presented with lower GCS scores and a higher frequency of seizures. ABG parameters showed strong predictive value: patients with DNS had significantly lower pH, PaO₂, and HCO₃⁻levels (all p<0.01). ROC analysis showed that pH ≤7.38 had the highest predictive accuracy (AUC=0.842), followed by HCO₃⁻≤18.6 (AUC=0.787) and PaO2≤82 mmHg (AUC=0.763). Conclusion: Arterial blood gas abnormalities, particularly low pH, low HCO₃⁻, and reduced PaO2 are significant predictors of DNS in acute CO poisoning. Metabolic acidosis is strongly associated with DNS development and may serve as a reliable early marker to identify high-risk patients. Early recognition of these parameters may improve monitoring, guide therapeutic decisions, and facilitate proper follow-up to reduce long-term neurological morbidity.