In CO poisoning all of the following clinical features are seen, EXCEPT:

Carbon monoxide (CO) is a colourless, odorless, tasteless, and non irritating gas produced by the incomplete combustion of any carbon-containing material. CO binds to hemoglobin with an affinity 250 times that of oxygen, resulting in reduced oxyhemoglobin saturation and decreased blood oxygen-carrying capacity. CO may also directly inhibit cytochrome oxidase, fuher disrupting cellular function, and it is known to bind to myoglobin, possibly contributing to impaired myocardial contractility. Symptoms of intoxication are predominantly in organs with high oxygen consumption, such as the brain and hea. The majority of patients describe headache, dizziness, and nausea. Patients with coronary disease may experience angina or myocardial infarction. With more severe exposures, impaired thinking, syncope, coma, convulsions, cardiac arrhythmias, hypotension, and death may occur. Cerebral edema (swelling of the brain) is also a common result of severe carbon monoxide poisoning. Survivors of serious poisoning may experience numerous ove neurologic sequelae consistent with a hypoxic-ischemic insult, ranging from gross deficits such as parkinsonism and a persistent vegetative state to subtler personality and memory disorders. Cyanosis is not seen in CO poisoning. Ref: Olson K.R. (2012). Chapter 44. Carbon Monoxide. In K.R. Olson (Ed), Poisoning & Drug Overdose, 6e.