Nitroglycerin

Here are some facts about nitrates!

The prototype drug is nitroglycerin. Other nitrates are isosorbide mononitrate and isosorbide dinitrate.

Nitroglycerin taken sublingually bypasses the first pass metabolism of liver and acts quickly. That is why, it is preferred in termination of an acute attack of angina where a rapid action is needed.

Nitroglycerin in low doses, causes venodilation, decreasing preload. In higher doses, it causes arterial and venous dilation, causing a decrease in preload and afterload.

Repeated and frequent exposure causes tissue tolerance to nitrates. That is why, nitrate free interval is recommended daily, especially with the use of transdermal patches or ointment.

Side effects of nitroglycerin are headache, postural hypotension and reflex tachycardia.

Supraventricular tachycardia mnemonic

To remember about SVT, all you need to remember is the cause and you know the symptoms and treatment!

Internship diaries: Gamjee roll

Attending, burns ward: Bring the *list of things* and a Gamjee along and come for dressing x patient.

Me: What?! Gamjeee?

*inner me*: Samwise Gamgee :D

Study group discussion: Differentials of wasting of small muscles of the hand

What are causes of wasting of small hand muscles?

The approach is to start with the spinal cord and move towards the muscles.

Spinal cord

Syringomyelia
Cervical spondylitis with compression of c8 root segment
Tumour
Trauma

Anterior horn

Motor neuron disease
Polio
Spinal muscular atrophy

Root lesion

C8 compression

Lower trunk brachial plexus

Thoracic outlet syndrome
Trauma, radiation, infiltration, inflammation

Peripheral nerve

Median and ulnar nerve lesion
Peripheral motor neuropathy

Myopathy

Distal myopathy
Dystrophia myotonica

Trophic disorder

Arthripathies
Ischaemia including vasculitis
Shoulder hand syndrome

That's a long list!

You're right. The most important thing is to remember the categories and some of the more common things listed.

Yup I love the way you listed it out.

Entropy, Enthalpy and Gibbs free energy – The monsters of bioenergetics.

The first law of thermodynamics is very famous. It says, "Energy can neither be created nor be destroyed but is converted from one form to another."

So simple.

But can you explain the second law of thermodynamics? A bit puzzled, aren't you?

It's the very reason I call it the monsters of bioenergetics. Let's convert these monsters into cute little pixies :)

The second law of thermodynamics says, "The entropy of the universe goes on increasing over time."

What is entropy?
Entropy is the degree of randomness.

A solid has closely placed molecules. Hence, the randomness in molecules is less. On the on the other hand, in liquids, the distance between the molecules is more. Hence, they have more randomness and more entropy value.

Melting of ice is a good example which illustrates the second law of thermodynamics. When the ice melts, solid gets converted into it's liquid form. The distance between the molecules increases from solid to liquid and thus, the entropy increases!

Here's an interesting fact: The human body consumes carbohydrates, breaks it down and stores its energy as ATP, which is a high energy molecule. One would argue that storage of such high energy molecule is against the second law, as entropy of the body is not increasing in this reaction. The entropy increases, but in this case, the entropy of the universe increases because we release carbon dioxide into the surrounding!

Since we are on this topic, let's address two more terms - Gibbs free energy and enthalpy!

Gibbs free energy

It is the Gibbs free energy which determines whether the reaction will proceed spontaneously to equilibrium without any input from surrounding.

In a reaction, if reactants are unstable (Having more energy) and the products are stable (Having less energy), then the reaction tends to move forward spontaneously without any input from surrounding.

On the other hand, if reactant is more stable than products then for this reaction to happen there has to some input of energy from surrounding.

Hence, if products have less Gibbs free energy than the reactants (i.e. change in Gibbs free energy is negative) then the reaction is spontaneous/exergonic irrespective of whether it is exothermic or endothermic.

Exergonic reaction - Thermodynamics

If products have more Gibbs free energy than the reactants (i.e. change in Gibbs free energy is positive) then the reaction is non-spontaneous/endergonic.

Endergonic reaction - Thermodynamics

Enthalpy

Enthalpy (H) is a sum of useful energy and non-useful energy. The non-useful part is the Entropy (S) and the useful part is the Gibbs free energy (G).

ΔH = ΔG + TΔS

To summarize all the three terms: 
Entropy: Degree of randomness (Non-useful energy)
Gibbs free energy: Energy available to do work (Useful energy)
Enthalpy: Sum of Entropy and Gibbs free energy!

Written by Komal M. Kadam
Illustrated by Immense Immunology Insight
Related post: How to remember the sign and direction of Gibbs free energy change

How to remember the direction of torsion of testis

Torsion of the right testis occurs in the clockwise direction and left testis occurs in the anticlockwise direction.

Heterophile antibody test, CMV and EBV mnemonic

Hi everyone!

Now - a - days, monospot test is used to diagnose infectious mononucleosis rapidly. 

But heterophile antibody test was used in the past and remembering it is high yield for exams.

Infectious mononucleosis is caused by EBV, which gives a heterophile positive antibody test.

In a minority of cases, infectious mononucleosis is caused by CMV, which gives a heterophile negative antibody test.

How do I remember this?

Mnemonic!

Study group discussion: Tonsils and pharynx review questions

Most common organism causing tonsillitis?
Group B hemolytic streptococcus.

Most common artery which bleeds in tonsillectomy?
Facial artery. 

Paratonsillar vein also known as?
Denise brown vein.

What is facial artery also known as?
Artery of tonsillar hemorrhage.

Why is cleft palate a contraindication to tonsillectomy?

The tonsil is situated at the anterior end of oropharynx. So if the person already has cleft palate and you remove the tonsil.. You are removing an extra support to the palate. This can lead to velopharyngeal insufficiency, that is, nasal voice (rhinolaila aperta) and nasal regurgitation.

15 year old boy presents with recurrent epistaxis which can't be controlled by adrenaline douches. Diagnosis?

Nasopharyngeal fibroma.

Why adrenaline ain't working?
Vessels here are just endothelium lined with no muscle coat.

What are the parts of pharynx?

Oroparynx, nasopharynx and laryngopharynx.

70 year old guy comes with right upper lateral lymph node enlargement. On further questioning, he complains of recent onset reduced hearing on right side. Diagnosis?

Nasopharyngeal carcinoma.

Virus causing NPC?

EBV

What's the pathogenesis of hearing loss in nasopharyngeal carcinoma?

NPC arises from the fossa of rosenmuller.. It's the most common site of origin.  

This, if you remember, is just behind the nasal opening of eustachian tube. So due to blockage of ET.. You get serous otitis media. Which is the cause for deafness. 

While examining a newborn, you notice that there is a mass in the nasopharynx. What is the rationale for checking neural tube defects in such a patient?

Nasopharyngeal bursa represents the embryonic attachment of notochord. So if you see a mass in a newborn in the nasopharynx, the baby maybe suffering from a occult NTD.

A patient comes to you.. He has trismus, fever, and a swelling which is pushing the tonsil medially. Diagnosis? Past history: Molar extraction a few days back.

It's parapharyngeal abscess.

Study group discussion: Refsums disease

Ataxia + Ichthyosis + Retinitis pigmentosa  + Don't drink milk.

Associated with which inherited autosomal recessive condition?

Refsums disease.

It's a rare AR disease.. The signs and symptoms of Refsum disease result from the abnormal buildup of a type of fatty acid called phytanic acid. This substance is obtained from the diet, particularly from beef and dairy products. It is normally broken down through a process called alpha-oxidation, which occurs in cell structures called peroxisomes.

Milk, cabbage etc. contain phytanic acid. That's why, they should be avoided.

Study group discussion: Pathophysiology of liquefactive and coagulative necrosis in hypoxia

Why does hypoxia in the brain cause liquefactive necrosis? And why does hypoxia cause coagulative necrosis in all other tissues?

Let's take it step by step!

What's the basis of coagulative necrosis in hypoxia? How does it appear?

The framework and architecture of the cells is maintained.

The reason is - In hypoxia, there is early reduction of ATP. Hence, there is a switch to anaerobic pathways. Increased lactic acid production causes a decrease in pH which results in the inactivation of even the proteolytic enzymes.

The organelles dissolve to some extent, but as the pH increases, enzymes are inactivated, leaving behind the framework.

So.. Why is there no coagulative necrosis in the brain?

There is no anaerobic metabolism in the brain. Hence, no lactic acid to stop the proteolytic enzymes.

Also, in brain there is no supporting matrix. It is all neurons and supporting cells.
In other words,there are no acellular substances. Whereas in other tissues, there is an acellular supporting matrix.

When hypoxia strikes, everything dies in brain.
Hence, liquefactive. In other tissues, the ECM maintains the structure a little bit.

Cool concept. Made me go woah.

Interesting fact: It has been established that casseous necrosis is not necrosis per say, but it is mass apoptosis of macrophages. Robbins mentions it as necroapoptosis.

Study group experience #16

Temporal arteritis
Polymyalgia rheumatica and polymyositis
Headache in brain tumor 

Dua's membrane

Artery of Percheron
Pseudoganglion 

Differentials of epistaxis 

MAC deficiency in Waterhouse Friedreichson syndrome 

Fluoride bulb and glycolysis 

Vitamin K overdose and deficiency 
Vitamins and renal stones 

Diabetes and ACE inhibitors

Anti-epileptic drugs
Pathological basis of drugs used in the treatment of Alzheimers disease 
Side effects of cyclophosphamide

Facies in medicine 
Hutchinson's in medicine 
Physics in Medicine 
Alcoholic liver disease, hepatic encephalopathy and stigmata

How to determine which hemisphere is dominant 
REM Sleep Behavior Disorder and Parkinson's disease 

Signs in acute appendicitis 
Infantile hernia 

Serial interval and communicable period 

Pleural tap

Oxytocin

Clinical tips for pediatric rotations

Dirty mnemonics

We have 100 members in all 3 groups so we made group 4 :D

I can no longer keep up with the discussions (Internship is draining me T_T)

For this reason, all Whatsapp chats will not be published on the blog, only some :)

Thanks for the tumblr fanmail (:

-IkaN

Study group discussion: Diabetes and ACE inhibitors

Question: Which of the following drug is best for reducing proteinuria in a diabetic patient?
A. Metoprolol
B. Perindopril
C. Chlorthiazide
D. Clonidine

Study group discussion: Dirty mnemonics

*During a random discussion on Krebs*

There's a mnemonic for the entire sequence in Krebs! It's kinda inappropriate.