Dyshemoglobinemias

Question 1

Name four places CO binds in the body.

Answer 1

1. binds Hgb - shifts oxygen dissociation curve, decreases 2,3-BPG
2. binds myoglobin - myocardial tox.
3. binds mitochondrial cytochrome oxidase - inhibits cellular respiration
4. displaces NO from platelets - forms peroxynitrites

Question 2

Which symptoms of acute CO effects are mild, moderate, severe?
chest pain, SOB on exertion, HA, coma, seizures, dysrhythmias, N/V, blurred vision, tachycardia, tachypnea, MI, ischemia, hypotension, dizziness, nyonecrosis, ataxia, cognitive deficits, skin bullae

Answer 2

mild - HA, N/V, dizziness
moderate - chest pain, blurred vision, SOB on exertion, tachycardia, tachypnea, cognitive deficits, myonecrosis, ataxia
severe - seizures, coma, dysrhythmias, hypotension, MI, ischemia, skin bullae

Question 3

What are the late/chronic effects of CO?

Answer 3

cognitive dysfunction, dementia, psychosis, amnesia, parkinsonism, apraxia, peripheral neuropathy, incontinence

Question 4

How long after CO exposure will late effects manifest?

Answer 4

2-40 days later

Question 5

What is believed to be the theory behind late CO effects?

Answer 5

reperfusion injury - delayed lipid peroxidation

Question 6

Who is at greatest risk for late CO effects? Adult or child? Associated acute symptoms?

Answer 6

adult over 30 who had a loss of consciousness

Question 7

How will pulse ox read in CO poisoning?

Answer 7

falsely normal - carboxyHgb read as oxyHgb

Question 8

How will an ABG read in CO poisoning?

Answer 8

co-oximeter - appropriate

calculation - falsely normal because pO2 normal

Question 9

What is the appropriate treatment for CO poisoning?

Answer 9

ABCs (airway, breathing, circulations)
oxygen - shortens CO T1/2
consider hyperbaric O2 - shortens CO T1/2 further; prevents lipid peroxidation and neurologic sequelae

Question 10

When are people exposed to cyanide?

Answer 10

jewelers, electroplating (mucus membrane or po exposure)

mostly - house fires

Question 11

How does CN cause toxicity?

Answer 11

binds cytochrome A3 in ETC - no ATP!!

Question 12

How does a CN patient differ from CO poisoning?

Answer 12

won’t be responding to supportive care, ABCs

lactate >10 associated with CN poisoning

Question 13

What are the two components of the antidote for CN?

Answer 13

sodium thiosulfate and hydroxocobalamin (Vit B12a)

Question 14

What is the MOA of sodium thiosulfate in CN poisoning?

Answer 14

enhances normal metabolism of CN through rhodenase enzyme

Question 15

What is the MOA of hydroxocobalamin in CN poisoning?

Answer 15

binds with cyanide to make cyanocobalamin (Vit B12)

Question 16

When should CN antidote be given?

Answer 16

any smoke inhalation victim not responding to supportive care and O2 therapy;
and any intentional CN exposure

Question 17

What is methemoglobin?

Answer 17

heme iron is oxidized to ferric (Fe+3) form

Question 18

What four ways is methemoglobin normally reduced back to normal? Which one can be exploited for therapeutic use?

Answer 18

1. NADH met-Hb Reductase
2. Ascorbate
3. Glutathione
4. NADPH met-Hb Reductase - can be increased with methylene blue

Question 19

What drugs and toxins lead to methemoglobin production?

Answer 19

Drugs - nitrites, nitrates in infants, sulfonamides, phenazopyridine, dapsone, local anesthetics

Toxins - nitrites, nitrates in infants, aniline dye, potassium chlorate, diarrheal illness in infants (makes nitrites)

Question 20

How does methemoglobin cause toxicity?

Answer 20

shifts O2 dissociation curve left - less willing to give up O2 in tissues

Question 21

Match the percent met-Hb to the symptoms:
0-10, 10-20, 20-50, >50, >70

apparent cyanosis; coma and death; dizziness, fatigue, HA, exertional SOB; asymptomatic; lethargy/stupor

Answer 21

0-10 asymptomatic
10-20 apparent cyanosis
20-50 dizziness, fatigue, HA, exertional SOB
>50 lethargy/stupor
>70 coma and death

Question 22

What is the antidote for methemoglobin?

Answer 22

methylene blue

Question 23

What’s the MOA for methylene blue in treating methemoglobinemia?

Answer 23

cofactor for NADPH reductase; gains electrons and donates them to methemoglobin

Question 24

What is the indication for using methylene blue?

Answer 24

met-Hb >20-30% or symptoms

Question 25

Side effects of methylene blue?

Answer 25

hemolytic anemia, pain at injection site, higher doses can cause dyspnea, restlessness, tremor, precordial pain, apprehension

Question 26

What are the possible reasons for someone to not respond to methylene blue treatment?

Answer 26

hemoglobin M disease; G6PD deficiency (lack generation of NADPH); CL salts inactivating G6PD; sulfhemoglobinemia; wrong diagnosis

Question 27

What will the pulse ox of someone with methemoglobinemia look like?

Answer 27

Fall rapidly into the high 80s

Question 28

ABG results of patient with methemoglobinemia?

Answer 28

co-oximeter - appropriate

calculation - falsely normal because pO2 not affected

Question 29

Is sulfhemoglobinemia more or less dangerous than methemoglobinemia?

Answer 29

more benign - doesn’t cause cyanosis as easily

treatment is supportive only