Tox Flashcards

1
Q

What is the pathomechanisms of CO poisoning?

A

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
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2
Q

What does the X axis and the Y axis measure in the oxyhemoglobin dissociation curve respectively?

A

Partial pressure of oxygen (X) and oxygen saturation (Y)

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3
Q

How will the oxyhemoglobin dissociation curve shift in CO poinsoning?

A

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

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4
Q

What is the main cause of CO poisoning?

A

Fire-related smoke inhalation

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5
Q

Which patients will have increased baseline COHb levels?

A

Normal: 3%
Smokers: 10-15%
COPD patients (even non smokers, the mechanism is unclear): Increased

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6
Q

What allosteric change happens to the other three hemes of a hemoglobin molecule afterthe binding of a CO molecule?

A

The ability of the other three oxygen binding sites to off-load oxygen to peripheral tissues is greatly diminished

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7
Q

What is the halflife of CO? Room air, high-flow oxygen and 100% hyperbaric oxygen

A

Room air: 250-300 min
High flow oxygen: 90 min
100% hyperbaric oxygen: 30 min

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8
Q

Clinical representation of CO poisoning?

A

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)
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9
Q

What is DNS?

A

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)
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10
Q

Diagnosis of CO poisoning?

A
  • 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

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11
Q

Which three tests might be a good idea after diagnosing CO intoxication?

A

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

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12
Q

What is the only absolute contraindication for hyperbaric oxygen therapy (HBO)?

A

Untreated pneumothorax

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13
Q

What is the most common cause of CN poisoning?

A

Domestic fires

Can also be liberated during combustion of products containing carbon and nitrogen

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14
Q

Which medical drug is toxic through GI exposure, but not IV, because of released HCN?

A

Amygdalin (antineoplastic agent)

  • Derived from apricot and peach kernels
  • Intestinalβ-D-glucosidase digests amygdalin, releasing HCN
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15
Q

Which drug used for hypertensive emergencies contains 5 cyanide groups per molecule?

A

Sodium nitroprusside

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16
Q

Explain the main pathophysiology behind CN poisoning

A

CN avidly binds to the final enzyme of the elctron transport chain, ceasing oxydative phosphorylation and leading to anaerobic metabolism and acidosis

17
Q

What are the mainly affected systems in CN poinsoning?

A

Cardiovascular and CNS

18
Q

Which organs/systems are affected by CN poisoning?

A

Pretty much every organ (Nervous, cardiovascular, respiratory, GI, skin, renal, hepatic, muscles

19
Q

In a patient with cyanide poisoning, what shade of red will the blood be and why?

A

Bright red

  • Decreased utilization of oxygen
  • High venous hemoglobin concentration
20
Q

Will a patient with cyanide poisoning appear cyanotic? Why?

A

No

Because of the bright red color of the blood from high venous oxyhemoglobin levels

21
Q

Which two main factors decide the symptoms of CN poisoning?

A

Severety and route of poisoning

22
Q

Which part of the nervous system is particularly sensitive to CN toxicity?

A

Basal ganglia

23
Q

Which neurological disease may be developed after CN poisoning?

A

Delayed onset parkinsonism or other neurologic sequalae

24
Q

What is tobacco amblyopia?

A
  • Progressive vision loss
  • Predominantly in male smokers
  • May result form inherent inability to detoxify the cyanide in tobacco
  • Symptoms may reverse after smoking cessation or hydroxycobalamin administration
25
Q

How do you diagnose CN poisoning?

A

Based on history and clinical presentation