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Background: CO2 narcosis, often induced by injudicious use of oxygen and opioids, may result in ICU admission, intubation and additional costs. The development is insidious. Currently, there is no method for early detection.
Methods: A retrospective cohort study of patients with hypercapnia admitted between June 2013 and June 2016 to a single hospital was performed. Presence of pre-defined CO2 narcosis was determined on chart review by agreement of two reviewers. Patients were divided into derivation and validation groups, and a scoring system for prediction of CO2 narcosis was developed and verified.
Results: 607 patients with significant hypercapnia (PaCO2>50 mmHg) were identified, and 188 were determined to have CO2 narcosis. Initial serum bicarbonate, use of supplemental oxygen, use of opioids, and BMI were found to be independent predictors. A CO2 narcosis scoring system (0-7 points) was developed in the derivation group and then verified. The scoring system stratified patients into low risk (0-2 points, 0% likelihood), intermediate risk (3-4 points, 11-27% likelihood) and high risk (5-7 points, 52-100% likelihood). Patients with CO2 narcosis have a higher probability of ICU admission, intubation and prolonged hospital stay. Judicious use of oxygen and opioids, and early interventions based on this risk stratification scheme, might prevent this condition.
Conclusion: This CO2 narcosis scoring system might be useful for prediction and risk stratification of CO2 narcosis.