Tox Flashcards
What is the pathomechanisms of CO poisoning?
CO has greater affinity to hemes than oxygen, which decreases O2 binding capacity and thereby tissue delivery
Displaces NO from surface hemoproteins. NO then reacts with ROS to produce ONOO-
- Activates platelets
- Activates neutrophils
- Inhibits mitochondrial function
What does the X axis and the Y axis measure in the oxyhemoglobin dissociation curve respectively?
Partial pressure of oxygen (X) and oxygen saturation (Y)
How will the oxyhemoglobin dissociation curve shift in CO poinsoning?
To the left.
Through the irriversible binding of CO to the hemes and the allosteric change that goes with it, the affinity and saturation for oxygen will go up
What is the main cause of CO poisoning?
Fire-related smoke inhalation
Which patients will have increased baseline COHb levels?
Normal: 3%
Smokers: 10-15%
COPD patients (even non smokers, the mechanism is unclear): Increased
What allosteric change happens to the other three hemes of a hemoglobin molecule afterthe binding of a CO molecule?
The ability of the other three oxygen binding sites to off-load oxygen to peripheral tissues is greatly diminished
What is the halflife of CO? Room air, high-flow oxygen and 100% hyperbaric oxygen
Room air: 250-300 min
High flow oxygen: 90 min
100% hyperbaric oxygen: 30 min
Clinical representation of CO poisoning?
Highly variable and largely nonspesific!
- Headache (most common)
- General symptoms (malaise, nausea, dizziness)
- Neurologic symptoms (from confusion to coma)
- .Myocardial injury
- Delayed Neuropsychiatric syndrome (DNS)
What is DNS?
Delayed neuropsychiatric syndrome
- Develops in 40% of patients with significant CO exposure
- Characterized by cognitive deficits, personality changes, movement disorders and focal neurological deficits
- Generally diagnosed within 20 days after poisoning (but can arise 3-240 days after recovery)
Diagnosis of CO poisoning?
- Based on history and physical examination
- Elevated COHb level measured by cooximetry of blood gas sample
Uwaga! Treatment with hydroxycobalamin may interfere with measurement of COHb
Which three tests might be a good idea after diagnosing CO intoxication?
ECG
-If it shows signs of schemia or a history of cardiac disease, check biomarkers
CT of head
- Rule out other causes of neurologic decompensation
- Hemorrhagic infarction of globus pallidus (and rarely deep white matter)
Psychiatric assessment
-Determination of suicidality
What is the only absolute contraindication for hyperbaric oxygen therapy (HBO)?
Untreated pneumothorax
What is the most common cause of CN poisoning?
Domestic fires
Can also be liberated during combustion of products containing carbon and nitrogen
Which medical drug is toxic through GI exposure, but not IV, because of released HCN?
Amygdalin (antineoplastic agent)
- Derived from apricot and peach kernels
- Intestinalβ-D-glucosidase digests amygdalin, releasing HCN
Which drug used for hypertensive emergencies contains 5 cyanide groups per molecule?
Sodium nitroprusside