Abstract

Introduction: Carbon Monoxide (CO) is a toxic, clear, colorless and tasteless gas.CO binds to hemoglobin with an affinity 200 to 250 times greater than that of oxygen. Exposure to CO is a serious health concern because individuals can be severely or fatally poisoned before even realizing that they have been exposed. Patients who survive acute poisoning are at risk of delayed neurologic sequelae.

Case Description: Three male patients presented to emergency department after being found unconscious in a car. They were 45, 52 and 13 years of age respectively. Car engine was running and air conditioner was on. There was no evidence of associated convulsion, tongue bite, urinary incontinence, vomiting or trauma. Pupils were normal in size, reacting to light. Plantar responses were flexor bilaterally and other systemic examinations were normal.

Follow-up: Arterial blood gas (ABG) was done. Co-oximetry revealed carboxyhemoglobin (COHb) level was raised in all 3 of them. Oxygen supplementation was started with a non-rebreather mask (NRM) at 15L/min. They were all admitted in ICU. Their consciousness level improved gradually. Repeat ABG after 5 hours showed significantly reduced COHb level. Two of them had raised Troponin-I level. Echocardiography and ECG were within normal limit. All of them took discharge on the following morning.

Discussion: Car exhaust fumes can contain up to 8% of carbon monoxide in enclosed spaces and is a very potent source of both accidental and suicidal cause of carbon monoxide poisoning 1.Toxicities result from impaired release of oxygen at the tissue level, causing cellular hypoxia and possibly direct CO mediated damage at the cellular level. Carboxyhemoglobin levels can be measured in either venous or arterial blood. Normal carboxyhemoglobin level is less than 5% but may be as high as 10% in smokers. CO poisoning can present with a wide spectrum of clinical manifestations. These ranges from mild symptoms, including dizziness or headache, to very severe intoxications, which may result in coma, shock, or death 2.Treatment includes immediate removal of the victim from the exposure and administration of high-flow or 100% oxygen by a nonrebreather reservoir oxygen-mask3.Hyperbaric oxygen therapy shortens the half-life of carboxyhemoglobin to 15 to 30 minutes compared with 40 to 80 minutes when patients breathe 100% oxygen.

Conclusion: Clinicians should suspect CO poisoning in cases of patients found in an unconscious state from an enclosed space. A high index of suspicion, early recognition and management can result in a favorable outcome. There is no specific antidote for this poisoning but high flow oxygen therapy is life-saving.

Correspondence: Dr. Ejaj Uddin Ahmed, Specialist, Critical Care Medicine, United Hospital Limited, Dhaka..