10. Cyanosis

Question 1

What is cyanosis?

Answer 1

Blue or purple appearance of the skin or mucous membranes

Question 2

What two processes typically cause cyanosis?

Answer 2

In adequate oxygenated blood containing deoxygenated hemoglobin
Presence of abnormal haemoglobin forms, which are unable to bind oxygen or supply, adequate oxygen to tissue and organs

Question 3

What is the typical threshold of haemoglobin to note cyanosis on physical exam (the amount of desaturated or un oxygenated haemoglobin in the circulating capillary blood is elevated to?)

Answer 3

50

Question 4

Why do patients with anaemia exhibit stenosis at lower arterial, partial pressure of oxygen and oxygen saturation level those with normal haemoglobin

Answer 4

Because cyanosis is not solely caused by percentage of the saturated, total haemoglobin mass or decreased amount of oxy haemoglobin

Question 5

List for primary causes of hypoxaemia

Answer 5

Ventilation perfusion mismatch
Hypo ventilation
Diffusion levitation.
Low levels of inspired oxygen

Question 6

What does a high ventilation perfusion ratio indicate?

Answer 6

Increase dead space.
Where is a low ventilation to perfusion ratio indicates a right to left shunt

Question 7

Name three examples of high ventilation, perfusion ratio mismatch

Answer 7

Pulmonary embolism
Emphysema
Pulmonary hypertension

Question 8

Name four causes of low ventilation, perfusion ratio

Answer 8

Asthma
Pneumonia.
ARDS
Pulmonary oedema

Can also have anatomic and congenital heart disease and Peyton duck arteriosus

Question 9

Name two causes of diffusion levitation, causing hypoxia

Answer 9

COPD.
Interstitial, pulmonary fibrosis

Question 10

How does methaemoglobin alter the normal iron in hemoglobin?

Answer 10

Normally haemoglobin has iron in the reduced Ferst FE +2, which normally and readily binds oxyhemoglobin, reverting to the Ferris state when oxygen is released

Haemoglobin can cause oxidative stress, which then causes the iron molecule to be oxidized into the fate, FE 3+

FE 3+ binding sites have higher affinity for oxygen and shift the curve to the left, further resulting in tissue hypoxia and subsequent lactate production

Question 11

How much of the total haemoglobin has to be met haemoglobin in order to see cyanosis

Answer 11

10 to 25% of total

Question 12

Matt haemoglobin is primarily reduced to ferrous FE 2+ haemoglobin by what enzyme in red blood cells?

Answer 12

NADH cytochrome B5 reductase

Question 13

What does a shift to the right of the oxy haemoglobin curve mean?

Answer 13

Favours oxygen delivery to the tissue so it a given PO two, haemoglobin saturation drops and oxygen is released

Question 14

What factors shift the oxygen haemoglobin dissociation curve to the right?

Answer 14

A decrease in pH more acidosis
Two, three – BPG increase.
Increase in temperature

Question 15

What four factors will shift the haemoglobin oxygen association curve to the left, favouring oxygen binding

Answer 15

An increase in pH, alkalosis.
A decrease into, three – BPG.
A decrease in temperature temperature.
An increase in met haemoglobin or SF haemoglobin

Question 16

For Med hemoglobin, NADPH reductase uses what two things to reduce met haemoglobin to Ferris hemoglobin?

Answer 16

Glue on
G6PD

Question 17

Why is methylene blue helpful in methemoglobin?

Answer 17

It acts to accelerate the second pathway in which met haemoglobin is reduced to Feres, haemoglobin through an ADH reductase, using glutathione and G6PD

Question 18

How does one usually get acquired methaemoglobinMia and what is usually this the result of?

Answer 18

Methaemoglobin production exceeds the capacity of NADH reductase activity
Usually, a drug reaction: local anesthetics, nitroglycerin, metoclopramide, Phenazopyridine

Question 19

For main categories of common causes of met haemoglobinEmia

Answer 19

Hereditary.
Acquired:
– medication’s

Chemical agents
paediatric cases

Question 20

Name eight medication’s in which can cause met haemoglobinEmia

Answer 20

Amyl nitrate
Plastics, including cyclophosphamide
Dap zone.
Local anesthetics, including benzocaine and lidocaine
Medical provide
Nitroglycerin
Nitroprusside
Quinones
Rasburicase
Sulfonamides: sulfamethoxazole

Question 21

Name five chemical agents that can cause methaemoglobinEmia

Answer 21

Fire by heat induced denaturation.
Food, high nitrates.
Napthalene - mothballs
Nitrous gases in Ark welders
Wellwater
Silver nitrate

Question 22

Key questions on history to ask in a presentation of cyanosis

Answer 22

Associated symptoms
Onset, duration, time of day of symptoms, previous episodes
Precipitating factors
Personal or family, history of heart, disease, particularly congenital, hypercoagulable states, haematologic disease
History of exposure to chemicals
Drug history

Question 23

Areas of Central cyanosis

Answer 23

Perioral.
Oral mucosa
Conjunctiva

Question 24

Why might interpretation of pulse oximetry be difficult in the setting of cyanosis?

Answer 24

Pulse ox symmetry measures light absorption of oxy, haemoglobin and deoxy haemoglobin using two light wavelengths, 660 which is red and 940 which is in infrared. The ratio of these two readings is the basis of the pulse ox calculation.

Standard pulse oximeter assume the absence, abnormal haemoglobin such as carboxy, haemoglobin or met haemoglobin. As such, haemoglobin absorbs well at both wavelengths, resulting in saturation readings of approximately 85% regardless of what the actual PAO2 or SA02 will be.

Question 25

Physical exam components, when assessing for cyanosis

Answer 25

Vitals: with caveat of methaemoglobin and carboxyhemoglobin, when assessing the pulse oximetry
HEENT
Cardio pulmonary

Question 26

Ancillary testing for general cyanosis

Answer 26

CBC
D dimer considering low suspicion of PE
Arterial blood gas

Question 27

If a patient with met, haemoglobin has peripheral blood dropped on a weight sheet, what will you see?

Answer 27

Typically no colour change of a chocolate brown and color.
Normally, when blood is exposed to 100% oxygen turns bright red

Question 28

Why are the PaO2 and SAO two levels of an arterial blood gas helpful to determine for met hemoglobin?

Answer 28

The PAO two and the SAO to themselves may be normal and met haemoglobin as the partial pressure of oxygen dissolved in the blood should not be affected. The oxygen saturation gap is the difference between the calculated theoretical, haemoglobin saturation on blood, gas analysis, and that measured by pulse, oximetry and elevated gap is strongly suggestive of met haemoglobin anemia.

Therefore should order carbon monoxide oximetry measurement

Question 29

Trial of oxygen in cyanosis: lack of improvement versus improvement suggest which?

Answer 29

In peripheral cyanosis improvement of oxygen suggests global under perfusion versus lack of improvement, suggests a focal vascular occlusion, secondary to environmental exposure, arterial, thrombus, or embolism or raynaud

Central disease, increase in oxygen improvement suggests hypoxaemia due to a diffusion impairment, hypo ventilation, or or VQ mismatch. If they do not improve, suggest a right to left shunt from pulmonary consolidation or congenital heart disease.

Question 30

Critical diagnosis of cyanosis differential

Answer 30

Acute cardiovascular and respiratory compromise – heart failure, ACS, hypovolemia, or cardiogenic shock, respiratory failure, upper area obstruction, massive PE, decompensation and a patient with known congenital heart disease or pre-existing lung disease, such as pulmonary fibrosis or COPD

Question 31

Emergent diagnosis of cyanosis

Answer 31

Met haemoglobinaemia
Sulfhaemoglobin anaemia
Polycythemia, including polycythemia, vera, secondary from an inappropriate increase in a erythropoietin, congenital heart disease, cigarette smoking, high altitude exposure
Raynaud

Question 32

How to manage a patient with peripheral cyanosis

Answer 32

Oxygen and check pulse of affected extremity
Determine likely vascular, insufficiency, or compromised cardiac output if they improve on oxygen or not
Differential diagnosis of vascular insufficiency includes basos spasm, or arterial, embolism or thrombosis

Compromised cardiac output shock includes hypovolemia, sepsis, cardiogenic shock, treat accordingly

Question 33

Treatment of central cyanosis

Answer 33

ABC’s, give oxygen
If they have respiratory distress and or an abnormal chest x-ray, then consider pneumothorax, airway obstruction, ARDS, pulmonary right to left shunt

No respiratory distress, consider cyanic disease, met, hemoglobin, anaemia or sulphur

Abnormal, cardiac pulmonary edema, consider heart failure

If there’s an infiltrate, consider pneumonia

If there’s no infiltrate, consider or spasm and treat accordingly

Question 34

MethaemoglobinEmia and sulfhemaglobinemia basics

Answer 34

One. Decontamination if there’s a contentious exposure
Two. A symptomatic and met haemoglobin level less than 20% weight vs symptomatic hypoxia or met haemoglobin level greater than 30% treat with oxygen and methylene Blue one to 2 mg per kilogram IV over five minutes
If symptoms continue or they continue to have levels greater than 30% a repeat dose of 1 mg per kilogram can be given

Question 35

Contraindications for methylene blue

Answer 35

Patients with G6PD deficiency as it can result in massive hemolysis, can use a sorbic acid instead

Teratogen in pregnant patients

Question 36

If a patient has an elevated met haemoglobin level and does not respond to methylene blue consider what diagnosis? How do you treat this?

Answer 36

Sulfhemaglobinemia

Irreversible for the life of the erythroid, no known antidote.
Supportive in removing the cause of agent

Question 37

Patient have polycythaemia what’s the treatment?

Answer 37

Phlebotomy.
Expansion with isotonic crystal Lloyd to achieve a haematocrit of 45%
Referral to haematology

Question 38

When do patients with methemoglobinemia need to be admitted?

Answer 38

Symptomatic
Met haemoglobin level greater than 15%
Treated with methylene blue