Study group discussion: Oxytocin

Question: Why does oxytocin cause volume overload?

Answer: It is similar to vasopressin in structure.

Vasopressin and oxytocin are similar in structure. So vasopressin is ADH. It retains water. Which will cause Intravascular volume expansion

There are a lot of compounds which have a similar structure and interesting clinical effects. Here are a few http://medicowesome.blogspot.in/2014/11/hormones-that-have-similar-structure.html

Doubt: Several pharmacology books said that oxytocin may cause hypertension. But Williams obstetrics says that it will cause serious hypotension if given as undiluted iv bolus. I'm confused.

Answer:
Bolus causes hypotension.
Normal infusion causes fluid retention.
Although unlike ergonovine, oxytocin does not produce hypertension.

So don't give bolus is the moral of the story. It can cause Placental hypoperfusion.

Question: How does it cause Placental hypoperfusion?

Answer: If your blood pressure drops, blood supply to all organs will be compromised. Comprehende?
Think of placenta as an organ. So Placental hypoperfusion!

Doubt: Does anyone know why iv bolus of oxytoxin will have adverse effect of hypotension and tachycardia?

Answer: In high doses... Oxytocin has vasodilator action which produces hypotension and reflex tachycardia.

From what I read, oxytocin decreases venous return and systemic vascular resistance. So that'll cause a compensatory tachycardia.

Source: http://www.ncbi.nlm.nih.gov/pubmed/18513945

Study group discussion: Hutchinson's in medicine

Hutchinson's triad:
Seen in congenital syphilis. Includes -
1) Interstitial keratitis
2) Hutchinson's teeth (which are notched incisors)
3) Vestibular deafness

Hutchinson's Sign: Seen in Herpes Zoster Ophthalmicus.. Which says if the nose is involved, then the eyes have to be involved too.. Since they both are supplied by the Nasocilliary nerve.

Hutchinson's Pupil:
Seen in concussion injuries to brain (usually associated with the subdural hemorrhage).
The ipsilateral pupil is initially miotic... Then it becomes myriadtic due to raised IOP... Then as the IOP further  increases, the contralateral pupil also dilates... So we have bilateral dilated pupils not reacting to light. This is an indication for immediate cerebral decompression.

Hutchinson's mask:
A sensation often associated with tabes dorsalis in which the face feels as if it is covered with a mask or cobwebs.

Hutchinson's facies:
The peculiar facial expression produced by the
drooping eyelids and motionless eyes in external
ophthalmoplegia.

Study group discussion: Facies in medicine

Mitral facies - Malar erythema.

Hippocratic facies - Acute peritonitis.

Typhoid facies - Severe malaria.

Adenoid facies - Adenoids.

Chipmunk facies - Malar prominence, in Thalassemia.

Hepatic facies - liver failure.

Leonine facies - coarse features, leprosy.

Facies leprosa - Falling of teeth and nasal bridge depression in leprosy.

Mask face - Parkinsonism.

Cushing's face - Moon like round.

Hutchinson's facies - The peculiar facial expression produced by the
drooping eyelids and motionless eyes in external ophthalmoplegia.

Study group discussion: Anti-epileptic drugs

Carbemazepine is contraindicated in which type of seizure?

During pregnancy, eclampsia and absence seizures.

Which anti eplielptic drug is contraindicated in pregnancy?

All of them.

Which antiepileptics can be used in pregnancy?

Sodium valproate, lamotrigine and lavatriacetram are safe in pregnancy.

Pregnant lady with epilepsy well controlled on sodium valproate wants to get pregnant. What will you do?

You do not switch the drug. Valproate has a dose dependent side effect on the fetus. You will try tapering down the dose. The main word is well controlled.

If while tapering the dose, she starts having seizures you switch to a safer drug.

Study group discussion: MAC deficiency in Waterhouse Friedreichson syndrome

Waterhouse Friedrichson syndrome has which immune component deficient?

MAC
C5-C9

And infections with what organisms are the especially susceptible to?

Gonorrhoea also?

No, just meningococcal

And just neisseria? Ideally, shouldn't there be increased susceptibility to all gram -ve organisms?

It is caused due to haemorrhage in adrenal gland. Waterhouse is not just a primarily immune complex deficient state. It is a manifestation of systemic infection due to meningococcal meningitis

Umm. My book says that patients with meningococcemia who develop Waterhouse..... Are generally MAC deficient.

There isn't susceptibility to other gram negatives because membrane attack complex is a defense against bacteria which can survive intracellularly.
So basically, extracellular lysis by MAC is effective in killing only Neisseria species.

You're susceptible to N. meningitis only because Neisseria gonorrhea has an outer membrane protein. MAC interacts with it and fails to insert in the bacterial membrane.

And then E. Coli and Salmonella have long polysaccharide chains in cell wall and these side chains prevent the insertion of MAC into bacterial membrane.

So MAC is good at killing only one thing - N. meningitidis and the deficiency will predispose you to this one infection only!

If you're talking about an infection that hemorrhages into the adrenals - it has to get really out of control to do that. And MAC deficient patients can't control their Neisseria infections leading to Water House Friedreichson syndrome. So the book is fair in saying those who develop WHFS due to meningococcal infections are usually MAC deficient.

Study group discussion: Artery of Percheron

*a picture of artery of Percheron was posted in the group on which this discussion took place *

That's vertebral arteries combining to form basilar. And again dividing to posterior cerebral arteries.

This is an anatomical variant.. Any odd thing in the picture?

The supply from the right branch of posterior cerebral artery. That seems odd! If it was normal.. It should have a bilateral supply.

Exactly.
It's called artery of Percheron.

What is special about it?

A rare anatomical variant where the thalamic perforator branch supplies both sides of the midline.

Any occlusion and you'll have bilateral paramedian thalamic infarction.

Ohh.. What would be the symptoms?

Yup.. How would unilateral infarction differ from bilateral?

I can't figure out which structure the artery is supplying!
They're thalamic peduncles. Unilateral you'll have sparing on one side. In Bilateral, the structures below the thalamus will be totally cut off from the structures above.

And symptomatically we are talking depending on which relay centre is affected? Or is there a very specific pure motor, pure sensory stroke we get?

Bilateral paramedian thalamic strokes are typically characterized by a triad of altered mental status, vertical gaze palsy, and memory impairment.

Altered mental status can present anywhere on the spectrum from drowsiness or confusion to hypersomnolence or coma...most probably due to damage to the reticular formation.

Vertical gaze palsy suggests mesencephalic involvement.

Memory deficits mostly are due to damage to the papez circuit. ..Anterior nucleus of thalamus is a part of the Papez circuit.
And also the thalamus acts as a 'search engine' for memories.

I looked up a few parts on the net...

That's awesome!

This is what I found in Harrison - Occlusion of the artery of Percheron produces paresis of upward gaze and drowsiness, and often abulia.

I liked the search engine bit. Nice info!

By the way, a similar sounding condition, 'Purtscher's retinopathy' is associated with acute pancreatitis.

How to remember lobular carcinoma spreads to contralateral breast

Hello! A short sweet post for today :D

Mnemonic: LOBUlar
Located in
Other
Breast
Usually

That's all!

-IkaN

Intravenous dreams

You know you have done too many blood collections when you say stuff like, "Dreams are collapsible, like a vein. So make sure you put needle in a good one."

Study group discussion: Dua's membrane

Cool fact: A new layer of cornea is discovered. It's called the Dua's membrane.

The Dua's Layer lies between the stroma and the descmets.

It's said to be acellular.

It was discovered last year by an Indian opthalmologist, Dr. Harminder Singh Dua.

Related post: Layers of the cornea mnemonic

Study group discussion: Pleural tap

Which muscles are pierced in midaxillary line during pleural tap?
Answer:
- Serratus anterior
- External intercostals
- Internal intercostals
- Intercostalis muscle

What are the boundaries of the safety area that we chose for pleural tap?

Answer:
Anterior - Lateral border of pectoralis major
Lateral - Lateral border of trapezius
Inferior - 5th intercostal space
Superior - Base of axilla

It's also called safe triangle.

Related post: Why is atropine given before procedures like drainage of pleural effusion aka pleural tap?

Staghorn calculus mnemonic

Staghorn calculus mnemonic

I remember the word, "MAPS"

M: Magnesium Ammonium Phosphate Struvite stones

A: Alkaline pH (AlkAline has 2 A's, Acid has just 1 A.)

P: Proteus

S: Splitting organisms (Urea splitting, urease producing organisms)

Staghorn calculus

Study group discussion: Vitamins and renal stones

Question: Which vitamin is indicated in treatment of calcium stones?

Answer: Pyridoxine

And which vitamin is avoided in a patient with history of calcium stones?

Answer: Vitamin C, it will worsen calcium stones.

Why?

Answer: Vitamin C increases oxalate in body. Pyridoxine decreases oxalate level in body.

Extra: Vitamin A deficiency too causes stones. The desquamated epithelium in tubules acts as a nidus for stone formation.

Study group discussion: Signs in acute appendicitis

Most commonly asked appendicitis signs

Aaron’s sign: A referred pain or feeling of distress in the epigastrium or precordial region, on continuous firm pressure over McBurney’s point, in acute appendicitis.

Dieulafoy’s triad: Tenderness, muscular contraction and skin hyperaesthesia at McBurney’s point in appendicitis.

Obturator sign: It refers to presence of hypogastric pain on stretching the obturator internus due to its irritation in the pelvis. This test is performed by passive internal rotation of the flexed rightthigh with the patient supine.

Bastedo’s sign : Pain and tenderness in the right iliac fossa on inflation of the colon with air, in cases of chronic appendicitis.

Psoas sign  : It is positive in retrocecal appendicitis. In this, irritation of the of the psoas muscle gives rise to pain when the patient’s right thigh is extended from the flexed position.

Rovsing’s sign  : Pain at McBurney’s point induced in cases of appendicitis, by pressure exerted over the descending colon

That's a good summary. Thanks!

Study link! Clinical features of acute appendicitis mnemonic
http://medicowesome.blogspot.ae/2014/11/clinical-features-of-acute-appendicitis.html