Systemic Venous Air Emboli After Emergent Hyperbaric Therapy for Carbon Monoxide Poisoning

Background

Carbon monoxide (CO) poisoning is a common cause of visits to the Emergency Department (ED) and can show various clinical presentations, from mild headache and dizziness to altered mentality. Emergency physicians should suspect CO intoxication after obtaining a thorough history of exposure to CO. There has been controversy over the use of hyperbaric oxygen therapy (HBOT) for CO poisoning; however, HBOT is the recommended measure for CO poisoning to prevent neurologic sequelae [1–4]. Possible complications of HBOT include baro-trauma, seizure, and myopia. However, in terms of the adverse effects of HBOT, a case of venous air emboli caused by HBOT for treating CO intoxication has not been reported.

This case showed multiple systemic venous air emboli on computed tomography (CT) scans, while the patient had dizziness, abdominal pain, and leg pains after HBOT. A venous air embolism is a rare condition that could result in significant harm to vital organs. It usually occurs due to iatrogenic sources, such as central venous catheter insertion, neurosurgery, and other invasive procedures [5–8]. Herein, we present the case of venous air emboli, a possible complication of HBOT, in the treatment of CO poisoning in the ED.

Case Report

An 82-year-old woman came to the ED after inhalation of fumes at the scene of a house fire. She felt dizzy and nauseous after the accident. Also, she had a headache when she was admitted to the ED. Her blood pressure was 150/80 mmHg, and her pulse rate was 82 beats per min. Her respiration was regular, with 16 breaths per min. The arterial blood gas analysis showed no signs of hypoxia, and the CO hemoglobin level was in the reference range (0.6%). Because we considered her symptoms to be a condition of CO poisoning, she underwent HBOT (100 min, 2.4 ATA, ascent of 1 m/min). During the protocol, there was no sign of distress. After the completion of the HBOT, the patient wanted to go home. However, she started to have light dizziness, chest discomfort, abdominal pain, and pain in both legs. The systolic arterial pressure decreased from 150 to 90 mmHg and the diastolic pressure decreased from 80 to 50 mmHg. She had tachypnea, with 25 to 30 breaths per min. Chest and abdominal CT scans showed multiple air emboli in her venous systems, including both femoral veins through the inferior vena cava and portal venous system (Figure 1). Fortunately, there were no air emboli in the pulmonary artery. We closely monitored her vital and neurologic signs and decided to use a different hyperbaric oxygen protocol (100 min, 2.4 ATA, ascent of 0.5 m/min), which had twice the ascent time as the previous protocol. On a CT scan after the protocol, the air emboli in the venous system were shown to have totally disappeared, and her symptoms were fully resolved (Figure 2). She could not have HBOT immediately when the air emboli were confirmed on the CT scans because she refused to undergo HBOT and was showing agitation. Collaborating support with a psychiatrist was needed, and then she underwent another HBOT.

Discussion

To the best of our knowledge, symptomatic multiple venous air after HBOT has not been reported in the literature. A vascular air embolism is usually caused by iatrogenic sources, such as surgery, catheterization, and trauma [5,9–12]. The entry of air into the circulatory system needs a pressure gradient and a path through the vasculature. The impact of vascular air emboli on the body system is different depending on the site of the emboli, the volume of air, and other conditions [13]. Some cases could be devastating if emboli block a critical area, such as the lung, heart, or brain. For decades, HBOT has been the best strategy for these cases [10,14,15].

Air emboli possibly occur as a type of decompression illness, a well-explained hazard of diving. Decompression illness is a rare condition related to self-contained underwater breathing apparatus (SCUBA) diving. The rapid change of ambient pressure causes air bubbles, which cause various clinical conditions [16–18]. Theoretically, the physiological changes of a patient in a hyperbaric chamber may be similar to the physiology of decompression illness in divers. Decompression illness starts with the formation and increase in size of air bubbles when the rate of pressure reduction exceeds the rate of inert gas washout in the tissues [19]. In this case, the occurrence of venous air after the use of a hyperbaric oxygen chamber could be regarded as a result of decompressed matter.

CO poisoning can be elusive at the time of presentation in the ED. Household fumes, especially, can have chemicals that mimic the clinical features of those from CO. For example, patients with cyanide poisoning present similarly to those poisoned by CO. Accordingly, emergency physicians should consider other causes when they determine the diagnosis.

Managing CO poisoning in the emergency setting can be challenging for the staff of the ED. An optimal HBOT protocol for CO poisoning has not yet been validated [3]. However, Costanza et al [20] suggest an integrated somatic-psychiatric protocol to prevent possible adverse effects of urgent HBOT in patients with intentional CO poisoning. The present case shows the possibility of causing decompression illness with urgent HBOT.

Conclusions

To the best of our knowledge, this is the first case of multiple systemic venous air bubbles after emergent HBOT. HBOT is the treatment of choice when physicians encounter CO poisoning in the ED. However, the hyperbaric chamber can be hazardous environment for patients of CO poisoning, as they are usually agitated and stressed from the event, whether it was by an intentional or accidental cause. Physicians should be aware of any complications of HBOT when treating patients who need HBOT in the emergent setting. Although decompression illness followed HBOT is extremely rare, it should not be ignored by emergency physicians.