A 74 y.o. male is brought to the ED after a seizure

The following page came from EMS

What do you suppose happened?

Hint: the CT was normal; the passenger also seized

Our patients had carbon dioxide poisoning.  They both passed out from hypoxia and seized.  This resulted in an MVC at low speed with minor front end damage. They were awake and confused when EMS arrived.  They had been transporting pies from Georgia  for Thanksgiving on dry ice in an SUV with the rear compartment connected to the main vehicle cab.  VBG showed pH of 7.20 and CO2 of 78 on the driver. 

Both recovered and were sent home.

You might have considered carbon MONOXIDE poisoning but since 1975 every vehicle made in the US has a catalytic converter which converts carbon monoxide to CO2 and water.

Carbon dioxide  percentages in room air are .04%.  It is odorless and accumulates near the ground, displacing oxygen. Most deaths are reported in closed spaces that are oxygen deficient like mines and ship holds. It can accumulate and has been reported  to cause deaths in  fermentation tanks, suicide attempts with dry ice, and even volcanic eruptions.  A volcano in 1984 caused a lethal CO2 gas burst from a submerged crater in a deep lake in Cameroun killing 37 people. Carbon dioxide not only causes asphyxia by hypoxia but also acts as a toxic substance .  At high doses it can cause unconsciousness almost instantly and respiratory arrest within one minute in dogs.

The story did not end there.  The driver was called back for  vertebral ectasia with an 8 mm basilar artery and dilated vertebral. He had an enlarged thoracic aorta at 4.4 cm  and was called back for an MRI which showed the same thing as the CTA.  A CT of the chest showed no dissection of the aorta.   Also found were liver cysts, gallstones, and liver fibrosis. It was decided since the pt was asymptomatic no further testing needed to be done. 

Permentier K, Vercammen S, Soetaert S, Schellemans C.  Carbon dioxide poisoning: a literature review of an often forgotten cause of intoxication in the ED. Int Journal of Emergency Medicine 2017;Apr 4.  10:14. PMID : 28378268.

Zaba C, Marcinkowski J, Wojtyla A, et al. Acute collective gas poisoning at work in a manure storage tank. Ann Agric Environ Med.  2011;18(2):448-451.

Sigurdsson H, Devine J, Tchua F, et al. Origin of the lethal gas burst from Lake Monoun, Cameroun. J Volcanol Geoth Res. 1987;31(1-2:1-16.Ikeda N, Takahashi H, Umetsu K, Suzuki T. The course of respiration and circulation in death by carbon dioxide poisoning . Forensic Sci Int. 11989;41:93-99.