Study group discussion: Amyloid

Does anyone have awesome things for amylodosis pathology?

Another concept you must understand is that the protein deposits in tissues depending upon where it was derived from.

For example, amyloid from immunoglobulins deposit in tissues of mesodermal origin like kidneys, heart, muscle, tongue.

When it's due to chronic inflammatory disease, it involves parenchymal organs like liver adrenals and pancreas.

Good concept.

Review question! Which amyloid protein is associated with Alzheimers disease?

Beta amyloid

Yes!

And why are patients with downs syndrome more susceptible to early Alzheimers?

Extra chromosome 21 which means extra copy of the presilline gene, I think.

Absolutely right!

Great.

Never knew that!

Oh oh one more!

Which condition is associated with amyloid deposition in the thyroid gland?

Are we talking about the medullary thyroid carcinoma?

Yep. The amyloid deposits are derived from calcitonin in that condition!

Which is the one in patients on dialysis?

Beta micro globulin?
B2 - microglobulin is seen in dialysis associated amyloid.
Derived from the MHC class 1 protein.

Yes. It's because the beta micro globulin is not filtered from the dialysis membrane.

Excellent stuff.

Study group discussion: Bone tumors

Osteoclastoma is a giant cell tumor, right?

And these giant cells can be differentiated from other giant cells on the basis of the number of nucleoli present?

 Yo

These giant cells will have about a 100 nucleoli

Osteogenic sarcoma is osteosarcoma. it is a malignant tumor

 names are confusing
 Osteosarcoma, osteoblastoma, osteoclastoma
 The other two are benign?

GCT(osteoclastoma) is a special variant bone tumor
Does not come under either benign or malignant
 Based on number of giant celss an osteoclastoma is loosely classified from typical to aggressive to malignant
 More giant cells and less stroma its benign, less giant cells more stroma its aggressive.

Osteoblastoma is a rare primary neoplasm of bone, categorized as a benign bone tumor that is closely related to osteoid osteoma. It differs from osteoid osteoma in its ability to grow larger than 2.0 cm in diameter and its aggressive behavior in bone.

Turner's syndrome mnemonic

Turner's syndrome mnemonic

Cystic hygroma, webbed neck: You can't turn your neck because of it.

Aortic coarction: Aorta takes a sharp turn.

Some toxicology mnemonics

Acetaminophen toxicity is treated with N acetyl cyteine.
Mnemonic: ACETaminophen ACETyl cysteine!

Ethylene glycol is metabolized to oxalic acid. Ethylene glycol is found in anti freeze.
Mnemonic: Freeze your EGO.
Anti freeze
Ethylene Glycol
Oxalic acid

Methanol is metabolized to formic acid by alcohol dehydrogenase which causes visual disturbances. It is treated with fomepizole.
Mnemonic: There's more to me (FoMEpizol) than what meets (Methanol) the eye (Blindness).

Study group discussion: Diagnostic tests for pulmonary embolism

What is the commonest sign on ecg for PE?

Nonspecific ST changes?
Nope.

SQ3 T3 something like that?
Nope.

Most common sign is sinus tachycardia. Most specific is S1q3t3 pattern..Positive only in 20-30% cases.

Ohhh!! Nice question.

Ooh.. We tend to forget common ones when looking out for rare signs!

What is the screening test for PE?

Screening test is d-dimer. If d-dimer is negative you virtually exclude the diagnosis of PE.

Which is the most specific diagnostic test for pulmonary embolism?

Pulmonary angiography.

Depends if the person is low risk or high risk! CT angiography is done though.

Which is the most preferred test for PE?

Spiral CT is preferred next to know location, size and blah blah.

What about VQ scan?

That's done if the patient is allergic to contrast.
Or has kidney failure.
Or CT isn't available.
Or the patient is pregnant.

In our hospital setting angiography would key since most patients can't afford CT.

Oh. But its invasive..and can be very harmful. It's only preferred when you are planning for thrombectomy..Or as a last resort to diagnose PE if all the other test are negative but d-dimer is positive.

Well money for a CT can feed a peasants family for a year.

True.

Venous doppler is preferred when CT or V/Q are inconclusive.

Whats d-dimer?
The clot thingy. It interlocks fibrin strands.

It is released from the thrombus.

Fibrin is non specific for clots
Because it is elevated in some other conditions as well. So d dimer to the rescue!
*Fibrin degradation products are.

Study group discussion: Management of ARDS

Anyone over here who knows the management of ARDS?

PEEP

Positive end expiratory pressure and 100% oxygen.

It's like during expiration your alveoli collapse, especially in ARDS since their surfactant is gone, so to prevent that collapse you give a bout of positive pressure at the end of expiration.
I don't know how they generate it but this is the mechanism!

Aah.

PEEP is continuous flow generated at certain fixed pressure that stops the alveoli from collapsing during the expiration. Pressure usually kept around 5

So the pressure is kept continuous during the whole time?

Yeah it's continuous during the both inspiration and expiration!

Umm then why is it called "End expiratory"?

That's a very good question actually. Don't know exactly why it's named that way!

Ever heard of low tidal volume ventilation? Aka lung protective ventilation? Aka baby lung concept?
It's used in managing ARDS. Since many alveoli are fluid filled and the patient effectively will have lesser tidal volume than normal. If we give the normal tidal volume the patent alveoli will burst due to barotrauma!
Inspite of normal tidal volume - 8-12ml/kg, we give 4-6ml/kg body weight for ARDS.

Also, you treat the underlying cause of ARDS.

You even have to restrict fluid overload. That's the other most important point!

Yeah read that too, diuretics are beneficial to some extent. Steroids are of no use.

Yup.

Also NO (Nitrogen oxide) is of no use.

Yeah for ARDS. During the various trails for the treatment of ARDS they observed that increasing the tidal volume lead to worsening most probably due to inflammation due to repeated opening and closing of alveoli with each inspiration and expiration ultimately affecting the structure of alveoli and their ability to perform their job. Low tidal volume along with PEEP significantly reduced the mortality in the patients with ARDS. So that the standard treatment at present.

I read there is other device called high RR..it provides respiratory rate of 15 to 20 cycles per SECOND.

It has a very low tidal volume but..Almost 1-2 ml / kg

Study group discussion: Trial of scar

Can anyone tell me about the "Trial of scar" after C section procedures?
I have heard of trial of labour, not sure if its the same thing!

My searches lead me to trial of labour as well ..I guess they are.

It's especially indicated in cases of borderline cephalopelvic disproportion.

The obstetrician let's the lady go in to labour in a controlled environment. If the labour becomes to stressful and is prolonged unduly, the doctor immediately performs a C section

It's more like given the patient an opportunity to experience normal vaginal delivery.

Same thing i suppose can be applied to scar from previous C section.

You see the chances of rupture of the lower segment scar is highest during labour, so the patient is monitored especially for signs of impending scar rupture

Most common is pain and tenderness over the scar area.

A off topic thing due to c/s delivery a tv series named "the knick", a medicine based serie in the beginning of the 20th century in usa, i recommend it, the changes in surgery, hospitalization, treatments are baby steps, surgeons invent the tools they use, amazing!

Study group discussion: Lateral spinothalamic tract mnemonic

PAin and TEmperature sensation carried by LAteral spinothalamic tract. Mnemonic is "PaTeLa" (which is present knee).

Study group discussion: Urinalysis

Significance of difference findings in urine analysis-
1) WBC in urine - Pyelonephritis
2) RBC - Glomerulonephritis
3) Hyaline cast - No significance
4) Broad waxy cast - CRF
5) Dirty brown/granular cast - Acute tubular necrosis

RBC's may also be present in case of calculi or tumors!

Correct!

"Approach to hematuria"
1) Dipstick - blood positive
Microscopy- RBC negative
It is myoglobinuria.

2) Dipstick - blood positive
Microscopy- RBC positive
It may be kidney pathology or bladder.

In that case if RBC is isomorphic (not distorted) - urinary bladder pathology like stones, cystitis.

If RBC is Dysmorphic - Kidney pathology (When RBC is passing thru tubules shape get distorted)

The dysmorphic RBC are a characteristic of glomerular pathology not tubular.

Study group discussion: Compliance of the lungs

Can anyone simply compliance for me?

Compliance = Change in volume/change in pressure.

So it follows as lungs starting at zero before inspiration. At the end there will be 500mL of air. So 0.5L
The pressure of he lungs starting at -5cm H20 increases to -10cm after expiration.

It would be (Specific compliance)
0.5 L/ (-5cm H20 - (-10cm H20))
= 0.5L/5cm H20 = 0.1 per cm H20

Theres a few types of compliance. Static compliance and dynamic.
Static calculates the periods where here isnt any gas flow. So during the time where there isn't fas flow.
Dynamic calculates the periods of active(!) Inspiration.

But I know nothing about those two calculations.

What is dead space of lungs?

There are two types of dead space-

1.       Anatomical

2.       Physiological

Anatomical dead space is the area included in the first 16 generation of the bronchial tree. Its by virtue of the normal anatomical structure that this area is unable to take part of in the exchange of gases

The physiological dead space is when there is decreased blood supply to a particular part of the lung, but the air entering the same part is normal. Hence there is no exchange of gases. In other words there is an increase in V/Q ratio.

Extra-

Why secondary tuberculosis affects the upper lobe?

There is an entity called ventilation perfusion ratio (V/Q)

meaning the degree of air entering the alveoli of lung and the corresponding pulmonary blood supply to the same. The normal value of the V/Q ratio is 0.8

Pulmonary blood capillaries are a low pressure system, with an average pressure of 25/8 mm of Hg. Out here comes the effect of gravity, pulmonary blood is unable to perfuse the upper lobes that well .

On the other hand, Air when it enters the lungs it enters the upper lobes better than the middle and lower lobes

This fact can be applied to

Study group discussion: Legionella confusion

A few days back, we had a discussion on legionella.

Legionella affects three systems - Lungs, GIT (diarrhoea) and CNS (Altered sensorium, confusion, etc).

Why does it cause CNS symptoms?