From the Guidelines
Central nervous system (CNS) toxicity from high oxygen concentrations typically manifests as seizures, visual changes, nausea, dizziness, anxiety, confusion, and behavioral changes, and management includes immediate reduction of oxygen concentration to the lowest level that maintains adequate tissue oxygenation, typically aiming for SpO2 of 88-92% rather than 100%. These symptoms occur because hyperoxia causes vasoconstriction and increased oxidative stress in the brain, leading to neuronal damage. The signs and management of CNS toxicity in patients receiving high concentrations of oxygen (O2) are crucial to prevent long-term neurocognitive dysfunction.
Some key points to consider in the management of CNS toxicity from high oxygen concentrations include:
- Limiting exposure to high oxygen concentrations (>60%) to the shortest duration necessary
- Using the lowest effective FiO2
- Implementing oxygen breaks when possible during prolonged therapy
- Close monitoring of arterial blood gases
- Supportive care for specific symptoms, such as standard anticonvulsant therapy for seizures
- Regular neurological assessments for early detection of CNS toxicity signs in patients receiving high-concentration oxygen therapy
Patients with certain conditions, such as COPD, may be more susceptible to oxygen toxicity and require even more careful titration 1. The goal of hyperbaric oxygen treatment is the prevention of long-term and permanent neurocognitive dysfunction, not enhancement of short-term survival rates 1.
In cases of carbon monoxide poisoning, hyperbaric oxygen therapy may be beneficial in reducing long-term sequelae, but its role remains controversial 1. The available data suggest that hyperbaric oxygen therapy may be helpful in treatment of acute carbon monoxide poisoning in patients with severe toxicity, with a low incidence of severe side effects 1.
Overall, the management of CNS toxicity from high oxygen concentrations requires careful consideration of the potential risks and benefits of oxygen therapy, as well as close monitoring and supportive care to prevent long-term neurocognitive dysfunction.
From the Research
Central Nervous System Oxygen Toxicity
The central nervous system (CNS) is susceptible to oxygen toxicity when exposed to high concentrations of oxygen, which can lead to a range of symptoms and complications.
- CNS oxygen toxicity can occur during hyperbaric oxygen therapy, with an incidence rate of 0.03% to 0.06% per treatment session 2, 3.
- The risk of CNS oxygen toxicity is influenced by various factors, including the duration and pressure of oxygen exposure, as well as individual susceptibility factors such as medical comorbidities and medication use 4, 3.
Signs and Symptoms of CNS Oxygen Toxicity
The signs and symptoms of CNS oxygen toxicity can vary, but may include:
- Non-convulsive symptoms such as nausea, vomiting, and fatigue 5
- Convulsive symptoms such as seizures, which can be tonic-clonic in nature 2, 6
- Cardio-respiratory abnormalities, including hyperoxic hyperventilation 5
- Loss of consciousness and postictal cardiogenic pulmonary edema in severe cases 5
Management of CNS Oxygen Toxicity
The management of CNS oxygen toxicity typically involves:
- Immediate removal from the hyperbaric oxygen environment 2, 3
- Administration of oxygen at a lower concentration to prevent further toxicity 6
- Monitoring for seizures and other complications, and provision of supportive care as needed 4, 5
- Identification and management of underlying risk factors, such as medical comorbidities and medication use 4