Hyperbaric O2 seizures: Treatment

Hyperbaric oxygen therapy (HBO) is an adjunctive therapy used to treat a number of specific conditions, including acute venous or arterial gas embolism (to reduce the gas bubble size), severe carbon monoxide or cyanide poisoning, to improve wound healing (non-healing ulcers, skin grafts, etc), decompression sickness, and acute traumatic or ischemic injuries (crush, compartment syndrome, etc). The theory behind HBO revolves around Henry’s Law, which states that at a constant temperature and at equilibrium, the amount of gas that dissolves in a liquid is directly proportional to its partial pressure. At sea level, i.e. 1 atm, the dissolved plasma oxygen concentration is 0.3 mL/dL, whereas hyperbaric oxygen delivered at 3 atm results in a dissolved plasma oxygen concentration of 6 mL/dL.

Complications related to HBO therapy include barotrauma (middle ear, sinus, pulmonary), pulmonary oxygen toxicity, reversible myopia, and CNS oxygen toxicity (i.e. seizures). Seizures are quite rare, and studies reporting incidence are inconsistent, ranging from 1 in 50,000 to 1 in 600 patients.^1,3 Patients at greatest risk are those with prior history of seizures or head trauma as well as those receiving glucocorticoids, insulin, thyroid replacement, and sympathomimetic medications.2 The risk is increased when patients are exposed to HBO greater than 90-120 minutes and when using pressures of 2.8-3 atm.2 In other words, the greatest risk is with long, sustained treatment sessions (without short intervals of room air) and using near maximal pressures.

Management of CNS oxygen toxicity seizures is terminating the HBO therapy session, decreasing the FiO₂ to 0.21, giving anticonvulsant therapy, and ultimately supportive care.²