Tuesday, September 26, 2006

Poisoning in MRCP(II)

Poisoning in MRCP (II)-Salicylates

In the second serial of this topic- poisoning in MRCP, I am going to talk about salicylates poisoning. It is an important topic in MRCP Part 1 and 2 as well as in your clinical practice. The reason is simple, salicylates can be obtained easily because it can be found in aspirin .You certainly know many patients are on aspirin if you go to ward everyday and at one time, some doctors even suggested to put aspirin in our tap water!


Before we discuss common presentations of a patient with salicylates poisoning, we must know the pathophysiology of salicylates overdose. Salicylates stimulate the respiratory centre initially and cause respiratory alkalosis. However, salicylates also interfere with carbohydrate metabolism and lead to accumulation of lactic acid and lead to metabolic acidosis.

Symptoms of Toxicity ( ASPIRIM)

Acute renal failure- symptoms of acute renal failure
Salicylism- deafness, tinnitus, vomitting
Pulmonary edema or cerebral edema (confusion)
Increased temperature
Respiratory alkalosis- hyperpnoea
GI disturbances and haemorrahge
Metabolic acidosis

Signs of toxicity

Air hunger ( due to metabolic acidosis)
Hyperpnoea ( due to respiratory alkalosis)
Remember that initially, there is respiratory alkalosis but later patient will have metabolic acidosis

Interactions

Increases anticoagulation effect
Low dose of aspirin precipitates gout

Treatment

Gastric lavage
Forced alkaline diuresis
Haemodialysis is indicated in severe cases

Hope you know how to answer your MRCP questions about salicylates after this post!

Saturday, September 23, 2006

Common Mistakes Candidates Make in MRCP

Common Mistakes Candidates Make in MRCP

OK, today I am not going talk about medicine but I would like to highlight to you a few common mistakes candidates make when preparing for thier MRCP,

1) I need at least one year or even more to prepare for MRCP Part1 and 2, but the fact is if you have a proper plan to study, you only need 5-6 months to cover every important topic.

2) I need to study a lot of books to know every fact, but the truth is you only need to stick to one good medical book. The trick is to do as many BOF as possible so that you know your weakness. Spend more time on your weak topics!

3) I need to take long leave to study their books. Medicine is always best learned beside your patients. If you see a SLE case today, go back and learn everything about SLE and find all BOFs about SLE and answer them!

4) I need to sit many times to pass the exam. You only need one attempt to pass MRCP if you prepare early and build up your confidence.

5) I must pay to get BOFs from the net, but the fact is there are a lot of sites out there which provide your free BOFs, just visit these sites and answer all these questions.

6) I must be very smart to pass MRCP, not quite, all my friends who pass their MRCP actually were not smart students when they were in medical schools.

Tuesday, September 19, 2006

Poisoning in MRCP(1)

Poisoning in MRCP(1)-Lithium

For those who recently sat for thier Part 1, good luck to all of you and hope for the best!You can do it!
" There is always hope !"

My friend sat for his MRCP Part 1 in Singapore recently. He said that questions asked in MRCP are getting more difficult to answer now. I would like to talk about poisoning today. There are a few important subtopics you must remember when learn about common drugs which are asked in MRCP.

1) Common symptoms and signs when there is poisoning.
2) Possible antidotes.
3) Drugs interactions
4) Whether the drug can be cleared by dialysis ( very important fact to remember!)

Today, I am going to talk about Lithium. If I can still remember, this drug was asked in my MRCP Part 1 in 2003.

Introduction:

Lithium is used as mood stabilizer and can be used as a treatment for acute mania/hypomania. It has a narrow therapeutic range ( <1mmol).>Symptoms for toxicity (LITHIUM!!)

- Loose motion
-Impaired vision
-Tremor
-Hypothyroidism symptoms
-Increased thirst ( polydypsia)
-Urine output increased ( polyuria)
-Muscle weakness/metallic taste

Signs for toxicity

-hyper-reflexia
- ataxia/dysarthria
-Confusion/fits

Interactions

NSAID, Thiazide, Phenothiazide, pheytoin and methyldopa increase lithium toxicity

Treatment

No specific antidotes but dialysis may be indicated!

Wednesday, September 13, 2006

Lung Cancer in MRCP

Lung cancer in MRCP

Lung cancer ( bronchial carcinoma) is a very popular topic in MRCP exam. The reason is quite simple, lung cancer is always among the top three cancer killer in males throughout the world. Cigarette is thought to be the major cause of lung cancer. There are a few important facts about lung cancer you must know,


1) There are 5 major subtypes of lung cancer

OSLAA
- Oat cell ( small cell), squamous cell, Large cell , adenocarcinoma and alveolar cell carcinoma.
Small cell lung cancer is usually the commonest type you will see in your clinical practice. Other subtypes can be put under as non-small cell lung carcinoma.

2) There are three main complications of lung cancer

The complications can be either it is due to local spread of the disease, distant metastasis or paraneoplastic syndrome. Remember that Para-neoplasic complication is frequently asked in MRCP! The most popular question asked is about Eaton-Lambert syndrome!

3) Absolute contraindications for surgical intervention are presence of distant metastasis, malignant pleural effusion, FEV1<0.8ll,other>

Clinical presentations

Classical symptoms include loss of weight, loss of appetite, cough, haemoptysis or symptoms due to underlying Para- neoplastic syndromes.

Physical signs

The physical signs can be divided according to type of complication as mentioned above.

Local spread of disease- pleural effusion, recurrent laryngeal nerve palsy ( hoarseness of voice) , superior vena cava obstruction

Distant metastasis- bony tenderness, hepatosplenomegaly

Paraneoplastic syndrome- Cushing’s syndrome, clubbing+/- hypertrophic pulmonary osteoarthropathy. (HPA)

Paraneoplastic syndrome

There are a few main presentations that you must always remember,

a) Endocrine

SIADH, Ectopic ACTH ( especially in small cell)
Hypercalcaemia- ( in squamous cell)
Carcinoid-like syndrome…… etc, etc ( Make sure your remember these four!)

b) Neurology
Remember Eaton- Lambert(EL) and how to differentiate from Myasthenia gravis.
Remember that in EL syndrome,
- usually affect proximal limbs and trunks, ocular and bulbar rarely affected
- hyporeflexia
- repeated muscle contraction may lead to increased muscle strength
( Source: Oxford Handbook of clinical medicine)


c) others- HPA, clubbing, some very rare skin lesions ( occasionally asked in MRCP PART 1 such as Erythema gyratum repens, dermatomyositis, acanthosis nigricans)

Investigations
The most important investigation- CXR but definite diagnosis may only be made after bronchoscopy, lymph node biopsy or even CT-guided biopsy.

Treatment

Small cell is usually not operable on presentation, chemotherapy may be useful
For non- small cell cancer, surgical resection if possible

Sunday, September 10, 2006

Cardiac catheterization in MRCP

Cardiac catheterization in MRCP

I found questions about cardiac catheterization are always very challenging in MRCP Part 2 exam. When I sat for my Part 2 three years ago, they would usually show you the pressure and saturation from a cardiac catheterization and ask you what the underlying cardiac lesion is, however, I notice that recently they have switched the way of asking this type of question. They prefer to give you a case with important physical signs and ask you to choose the correct cardiac catheterization results.

Anyway, start form basic first, remember the normal and pressure of each cardiac chamber as below,

Left heart
Aorta-------120/80 ( pressure)---------98% (saturation)
LV----------150/5-10------------------98%
LA--------------------------------------98%

Right heart
RA------------0-8 (mean pressure)-----74%
RV-----------15-30/0-8----------------74%
PA-----------15-30/3-12---------------74%
SVC-------------------------------------74%
IVC-------------------------------------70%
PCWP--------1-10 ( mean)

There are two main groups of questions in MRCP, either a saturation or pressure problem, we would talk about saturation problem first today.
I would give you a few examples and explain to you the underlying cardiac lesions,

Case 1:

---------------Pressure mmHg --Saturation%
Right heart
SVC ------------------5-------------- 72
RA -------------------6-------------- 76
RV----------------- 25/0-5 ----------76
PA -----------------25/10----------- 77

Left heart
LV ---------------140/0-12---------- 97
Aorta --------------140/75 -----------97

You notice that the saturation at the superior vena cava is 72% and increases to 76%, if you remember your anatomy, blood from SVC would go to right atrium (RA) and the saturation should be the same ( see above image again), therefore , there must be presence of mixture of blood from more oxygenated blood from left atrium and right atrium. Yes, you are right, the diagnosis is atrial septal defect!

Case 2:

----------------Pressure (mmHg) ----Oxygen saturation (%)
SVC--------------- - ---------------------72
RA ------------------7--------------------72
RV----------------- 50/12----------------86
PCWP-------------- 16 ------------------- -
LV -----------------90/12----------------96
Aorta ---------------100/50---------------97

This question is easy, you notice there is a sudden increase in oxygen saturation from RA to RV, therefore, there must be mixture of blood over RV and LV, the diagnosis is Ventricular septal defect( VSD).

Case 3:

-------------------Pressure (mmHg)------ Oxygen saturation (%)
IVC -------------------------------------------60
RA ---------------------20---------------------66
RV--------------------- 100/20---------------- 67
PA ---------------------100/30---------------- 67
LV ----------------------100/10 ---------------70
Aorta-------------------- 105/80---------------70

This case is more complicated, however, stay calm, apply basic principles. You notice that there is an increase of oxygen saturation form IVC to RA ( sounds like it is an atrial septal defect). However, you notice that RV’s pressure is high and even equals to that of LV’s. Another abnormality you notice is the saturation of LV and aorta is low ( as compared to more than 95% in normal subjects). So…… the diagnosis is Eisenmenger’s syndrome secondary to ASD.

Case 4:

----------------------------Pressure (mmHg) --------Oxygen saturation (%)
Superior vena cava ----------------------------------------77
RA -----------------------------6--------------------------78
RV -------------------------------------------------------- 78
PA ---------------------------50/20----------------------- 86
PCWP--------------------------16-----------------------------
LV--------------------------120/11------------------------96
Aorta------------------------- 130/60----------------------97

This case is simple, you notice there is high pressure present over Pulmonary artery with sudden increase in oxygen saturation, therefore mixture of blood must be present over the pulmonary artery. Yes, you are right, you are dealing with Patent Ductus arteriousus.

Ok, that is enough for today, we have learn about cardiac lesions that give you abnormal oxygen saturation during cardiac catheterization, I would talk more about valvular heart lesions that give your abnormal pressure during cardiac catheterization in future posts.

Friday, September 08, 2006

Paget’s disease of bone in MRCP

Paget's disease of bone

Disease of unknown origin. There is increased bone turnover due to an increase in bone osteoclast activity , which leads to increased osteoblast activity. Increased bone remodeling leads to bone enlargement, deformity and weakness.





Clinical presentations

Usually bone pain, bone deformity and deafness

Physical signs

You may notice bone deformity and warm bones. Rare in patients less than 40 years old. Rare as well in tropical countries.

Investigations

I notice that a lot of candidates have problems interpreting Calcium, phosphate, ALP in various conditions, I find this the following table useful,

Bone disease calcium Phosphate ALP
Paget’s Normal Normal ^^
Myeloma ^/Normal Normal unless fracture
Osteomalacia down down ^
Osteoporosis Normal Normal normal
Bone metastasis ^ ^/ normal ^

( It is even more confusing for hyperparathyroidism, I would cover that in future post)

Remember that level of ALP reflects osteoblast activity, therefore, if there is no new bone formation, ALP level would not be raised. This also explains ALP is high in growing children! On the other hand, level of urinary hydroxyproline reflects osteoclast activity, when there is breakdown of bone, the level would be raised.

Diagnosis

Based on typical x-ray appearance and raised AP with normal Calcium and phosphate

Coarse trabeculation and bony expansion

Complications

Nerve/ cord compression
Osteogenic sarcoma
Heart failure ( high output)

Treatment

Bisphosphonates is the treatment of choice. It inhibits bone resorption ( osteoclast activity) . It is also used in management of hypercalciamia especially in bone metastasis and osteporosis!

Tips for MRCP

Remember that patients with Paget's disease always have a raised ALP with normal calcium and phosphate !

Sunday, September 03, 2006

Genetics in MRCP

Today I am going to tell you a few genetics conditions which are commonly asked in your MRCP PART 1.

1) Autosomal dominant inheritance
- generally ‘ structural-type’ disorders

a) adult polycystic kidney disease
b) myotonic dystrophy
c) Elers-Danlos and Marfan’s syndrome
d) Hereditary haemorrhagic telangiectasia
e) Huntingtons chorea
f) Intestinal polyposis
g) Neurofibromatosis
h) Otesogenesis imperfecta
i) Tuberous sclerosis

2) Autosomal Recessive inheritance
- generally ‘metabolic type’ disorders

a) Infantile polycystic kidney
b) Alfa1-antitrpsin deficiency
c) Cystic fibrosis
d) Most inborn errors of metabolism ( galactosaemia, glycogen storage diseases etc)
e) Haemoglonbinopathies ( sickle cell disease and thalassaemias)
f) Wilson’s disease
g) Friedreich’s ataxia

3) Sex-linked dominant inheritance

a) Vitamin D risistnact rickets

4) Sex-linked recessive inheritance

a) G6PD deficiency
b) Haemophilia A and B
c) Lesch-Nyhan syndrome
d) Immunodeficinecies- agammagobulinaemia

However, there are a few types of muscular dystrophies you should remember,

Duchenne - X linked recessive
Becker -X linked recessive
Limb girdle -Autosomal recessive
Facio-scapulo-humerol -Autosomal dominant

Tips for MRCP

Remember how to interpret a family tree, it is the commonest way how genetics of above disoredrs are asked in MRCP!