Mnemonics and basics of ECG interpretation

Hello !! 

Many people think ECG interpretation is hard i will take you through the basics of it.

To understand how to interpret the ECG you must first understand the basics which is out of the scope of this scope.

To interpret an ECG the following are the most important:

1. Understanding the basics 

2. Systematic approach for interpretation

SOME BASICS

ECG WAVEFORMS

- What do the waves represent ?

Adapted from: https://meds.queensu.ca/central/assets/modules/ts-ecg/waves_and_complexes.jpg

WAVES AND INTERVALS PICTORIAL REPRESENTATION

Adapted from: https://ecgwaves.com/topic/ecg-normal-p-wave-qrs-complex-st-segment-t-wave-j-point/

- What do the boxes represent ? 

Each small box in the ECG paper is 1 mm = 0.1 mV = 0.04 secs

Each large box in the ECG paper is  5mm = 0.5 mV = 0.20 secs (0.04 X 5)

Adapted from: ECG interpretation made incredibly easy —5th ed 

SYSTEMATIC INTERPRETATION

1. Heart rhythm

- Use paper and pencil/pen method for determination of the heart rythm

 

Adapted from: ECG interpretation made incredibly easy —5th ed 

- Determine whether it is a sinus rhythm ? (in which each QRS complex is preceded by a p wave)

- Determine whether the rhythm is regular or not:

- Types of rhythms:

a. Regularly regular rhythm: In a normal individual

b. Regularly irregular rhythm: Sinus arrhythmia

c. Irregular irregular rhythm: Atrial fibrillation

2. Heart Rate

- Atrial rate : between 2 P waves

- Ventricular rate : between 2 R waves

- Can be calculated depending on whether the rhythm is regular or irregular

- If the rhythm is regular the following methods can be used:

a.  300 method

In this take 300 divided by number of large boxes between 2 R waves

Example: If the number of boxes between 2 R waves is 3 then the Rate would be 300/3 = 100 beats/min.

b. 1500 method

In this take 1500 divided by the number of small boxes between 2 R waves

Example: If the number of boxes between 2 R waves is 14 then the Rate would be 1500/14 = 107 beats/min.

c. Rapid estimation method

Use this only if the rhythm is regular

Using the number of large boxes between R waves or P waves as a guide, you can rapidly estimate ventricular or atrial rates by memorizing the sequence “300, 150, 100, 75, 60, 50.”

For an Irregular rythm:
- Use the rythm strip / Lead II and count the number of R waves in 6 seconds (30 large boxes ) and multiply by 10.

3. Cardiac Axis

- Determined using lead I and II / aVF

- Determine the cardiac axis : the easiest way is to use the thumb rule

- Left thumb represents lead 1

- Right thumb represents lead 2 or lead aVF

- Mnemonics for the causes of axis deviation RAD RALPH the LAD from the VILLA

RAD - Right axis deviation causes

R- Right ventricular hypertrophy

A- Anterolateral MI

LPH- Left posterior hemiblock

LAD - Left axis deviation

V- Ventricular tachycardia

I- Inferior MI

L- Left ventricular hypertrophy

LA- Left Anterior fascicular block

4. Evaluate P wave

- P waves should be upright in leads I and II, inverted in aVR

- Are p waves present before every QRS complex? if yes; sinus rhythm

- P waves may be absent in; atrial fibrillation

- Normal P wave : <0.10 sec (2.5 small boxes)

- Common Abnormalities of P wave

Bifid/notched P waves (p mitrale) : Left atrial enlargement - classically due to mitral stenosis

Peaked P waves (p pulmonale) : Right atrial enlargement - due to Pulmonary Hypertension

5. Duration of PR interval

- The PR interval is the time from the onset of the P wave to the start of the QRS complex 

- It reflects conduction through the AV node

- Normal duration : 3-5 small boxes (0.12 to 0.20 secs)

- Determine if the duration is normal

- Common abnormalities of PR interval

a. Can be prolonged in: AV block

b. Can be short in: Pre-excitation syndromes e.g in Wolff-Parkinson-White syndrome; which involve the presence of an accessory pathway connecting the atria and ventricles.The accessory pathway conducts impulses faster than normal, producing a short PR interval.

6. Duration of the QRS complex

- Normal duration : 2-3 small boxes (0.08-0.12 secs)

- Determine if the duration is normal

- Are all QRS complexes of same size and shape ?

- Does a QRS complex appear after every p wave ? if not consider an AV block (second degree AV block); in which the PR-interval progressively gets longer until a QRS is dropped and only the p-wave is present

- Common abnormalities of QRS complex

a. QRS deflections; Exaggerated QRS deflections indicate ventricular hypertrophy 

- The voltage criteria for left ventricular hypertrophy are fulflled when the sum of the S and R wave deflections in leads V1 and V6 exceeds 35 mm (3.5 mV) ( 7 large boxes )

- Right ventricular hypertrophy causes tall R waves in the right ventricular leads (V1 and V2)

- Diminished QRS deflections occur when pericardial effusion or obesity electrically insulates the heart

b. Narrow QRS complex morphology (<0.08 secs)

- Atrial flutter

- Junctional tachycardia

- Note : normal sinus rhythm also has a narrow QRS complex morphology

c. Broad/wide complex QRS complex morphology (>0.12 secs)

- Bundle branch block (BBBB) : LBBB or RBBB

- Hypokalemia

- Poisoning with sodium-channel blocking agents (e.g. tricyclic antidepressants) - remember this also gives you a dominant R wave in lead avR.

7. ST segment

- The ST segment is the flat, isoelectric section of the ECG between the end of the S wave and the beginning of the T wave.

- It represents the interval between ventricular depolarization and re polarization.

- The most important cause of ST segment abnormality (elevation or depression) is myocardial ischemia or infarction.

The causes of ST elevation can be remembered using the mnemonic ELEVATION

Electrolyte abnormalities

Left bundle branch block

Aneurysm of left ventricle

Ventricular hypertrophy

Arrhythmia disease (Brugada syndrome, ventricular tachycardia)

Takotsubo/Treatment (iatrogenic pericarditis)

Injury (myocardial infarction/ischaemia or cardiac contusion)

Osborne waves (hypothermia or hypocalcemia)

Non-atherosclerotic (vasospasm or Prinzmetal’s angina)

The causes of ST depression can be remembered using the mnemonic DEPRESSED ST

Drooping valve (MVP)

Enlargement of LV with strain

Potassium loss (hypokalemia)

Reciprocal ST- depression (in I/W AMI)

Embolism in lungs (pulmonary embolism)

Subendocardial ischemia

Subendocardial infarct

Encephalon haemorrhage (intracranial haemorrhage)

Dilated cardiomyopathy

Shock

Toxicity of digoxin, quinidine

8. Evaluate T wave

It represents ventricular repolarisation

NB: 

Upright in all leads except aVR and V1

Amplitude <5mm (5 small boxes) in limb leads, <15mm (3 large boxes) in precordial leads

- Are T waves present ?

- Do they have normal shape ?

- Do they have normal amplitude?

- Do they have same deflection as QRS complexes ?

- Common T wave abnormalities

a. Inverted T wave

- Can be remembered by the mnemonic INVERT

Ischemia, raised ICP

Normality [esp. young, black]

Ventricular hypertrophy

Ectopic foci [e.g. calcified plaques], classic pulmonary Embolism 

RBBB, LBBB

Treatments [digoxin]

b. Tall/peaked T waves

- Classically seen in Hyperkalemia

c. Hyperacute T waves

- Seen in early stages of ST elevation MI (STEMI)

d. Biphasic T waves

-Ischaemic T waves go up then down

-Hypokalaemic T waves go down then up

e. Flat T wave

- Ischaemia

- Hypokalemia

9. Determine the duration of the QT interval

QT interval : is the time from the start of the Q wave to the end of the T wave. It represents the time taken for ventricular depolarisation and repolarisation, effectively the period of ventricular systole from ventricular isovolumetric contraction to isovolumetric relaxation

- QT interval is inversely proportional to heart rate i.e as the HR increases the QTi decreases and vice versa

- The QT interval should be measured in either lead II or V5-6

- Determine if the QT interval is normal ? (normal = 0.36 to 0.44 secs = 9-11 small boxes)

- Corrected QT interval (QTc)

-- Due to the variations of the heart rate : The corrected QT interval estimates the QT interval at a heart rate of 60 bpm.
-- The following formula can be used to calculate the QTC = QT interval / √ RR interval (Bazzet's formula) 
-- RR interval = 60/Heart rate
-- Note: there are many formulas which can be used for calculation of but this is probably the easiest one.
-- QTc is prolonged if > 0.44 secs in men or > 0.46 secs in women

-- QTc > 500 is associated with increased risk of torsades de pointes

- Causes of prolonged QTc > 0.44 secs

Hypokalaemia

Hypomagnesaemia

Hypocalcaemia

Hypothermia

Myocardial ischemia

Post-cardiac arrest

Raised intracranial pressure

Congenital long QT syndrome

Drugs - quinidine, amiodarone, TCA's

- Causes of a short QTc < 0.36 secs

Hyperkalemia

Hypercalcaemia

Congenital short QT syndrome

Digoxin effect

The End !!

Please note that this is not everything that you need to know , and this article doesn't cover everything about the ECG, it just covers the basics and the most common abnormalities that can be found on an ECG.

But for sure ! It has just enough information which can help anyone understand and interpret and ECG.

Mohammad Farouq,

Final year medical student, MUHAS.

MCQ Mnemonic Series: Apple jelly nodules

#ENT

#Dermatology
Apple jelly nodules on nasal septum are seen in :

Options:
A) Leprosy

B) Syphilis

C) Lupus vulgaris

D) Wegner’s granulomatosis

✍✍✍✍

LLuPPus vulgaris
aPPLLe jelly nodules
{Luppal ~ Apple)

By
Dr. Shubham Patidar

Letters of Recommendation [LORs] 101

The letters of recommendation are very important for the residency application process. All the programs require a minimum of three and a maximum of four letters of recommendation for a complete application. So, I thought I will put together all the information needed to know about Letters of Recommendation[LORs].

DISCLAIMER: Long post!!

1. How important are LORs?

LORs are compulsory while applying for a residency program. Most of the programs require at least three LORs for a complete application.

2. Do all the LORs need to be from the states?

It is good to have all the LORs from the clinical experience from the states. But, a few programs require a letter from the department head of your med school. In such cases, you need to submit one from your med school.

If you don’t have all the LORs from the states, try to get at least two. Its easier for the program director to believe if someone from the same country says that you are well versed with the system than from someone who is outside the country.

But is there not anyone who matched without any letters from the states? There are!! But there are many terms and conditions involved like stellar scores, strong contacts etc. So, to be on the safe side it's better to apply with letters written by someone in the states.

3. What is the difference between a waived LOR and non-waived LOR?

Waived LOR is uploaded by the LOR writer or someone on his behalf and it by default means you never saw the letter.

Non-Waived LOR is uploaded by you or the letter writer. It means that you have seen the letter and know the contents.

Waived LORs are supposed to carry more value than non-waived. But, if you believe that a non- waived LOR is stronger than a different waived LOR you have, definitely use the strong one.

Value: strong waived LOR> strong Non-waived LOR> weak waived LOR>weak Non-waived LOR.

4. How do I send a request/upload a LOR into the ERAS?

There is a tab for LORs on ERAS. Follow the instructions and it gives a printable form to send to the LOR author to upload the letter. You can also send the request directly via ERAS to the author. It has step by step process on how to upload a LOR.

Remember the author should have an AMA account to upload.

5. When do I ask for a LOR?

Usually in the last week or last day of your rotation. Ask your author for a feedback first and assess what he/she feels about you and then ask for a LOR.

Example:

“Hi doctor, it has been a pleasure working with you. I would like to take any feedback you have for me regarding my performance”

“I will be applying for so and so residency this year, will you be comfortable in writing a strong LOR for me?”

If they say yes, ask them if they are comfortable uploading it to ERAS and if they are familiar with it. 

Tell them you will send the ERAS request form once the application season starts. If they are not, offer to help them upload the letter explaining to them the importance of a waived LOR.

Never push them to do what they are not comfortable with. Be polite.

6. My LOR author offered me to write my own LOR, what do I do?

Never leave such an opportunity. It means that the mentor trusts you to write a letter. This is an opportunity to write a strong LOR. Try to include the following in the LOR:

      

    A) Start with how the author knows you and how long he/she worked with you.

    B) Try to give examples to the positive features described. Ex: Don’t say this student is punctual, say something like he/she always arrived before time and left only after the work is done. It will show you are punctual and committed.

    C) Put in strong adjectives. Ex: Rather than hardworking say very hardworking.

Keep a proforma in handy. Some authors might ask proforma. Try to personalize as much as you can.

7. I did a lot of rotations and have a lot of LORs, which ones do I use?

This usually happens with repeat applicants. First of all, use the LORs which you feel are the strongest. If you believe that all of them are strong enough, use the LORs specifically from the same region as the program. Ex: If you are applying to programs in Michigan, and if you happen to have a LOR written by someone in Michigan-use it.

If any your LORs are from people in higher positions like PD, APD, Chairman and are strong LORs- use them.

8. How do I get my LORs from the previous year?

Just buy the token and login into your ERAS account, LORs would have been transferred.

9. I have a LOR from a specialty different from what I am applying for, Is it useful?

Yes! Although it is better to have a LOR from the same specialty, it is not bad to have LOR from a different specialty.

Any LOR is better than no LOR. But make sure that LOR doesn’t say that you are interested in a specialty different from the one you are applying to. Or ask your LOR author to mention your dedication to the specialty you are applying for.

Ex: If a pediatrics author is writing LOR for IM application, Ask them to mention you are dedicated for IM and not to mention you like peds.

10. How useful are the letters of reference?

Letters of reference are written by a physician who you didn’t work with but know you personally. This is a gray area. It worked for some people and some consider it useless.

                                                                                                                                       

TIPS:

1. Use google to find proformas online. Don’t copy paste but try to understand the format.

2. Try to send it to people who matched, they might help you make corrections and make it stronger.

3. Authors might not upload the same LOR you gave them. Remember, they have the liberty to change-they are the authors.

4. If someone offers you to write a LOR after September, ask them to write it and take it by hand to interviews and give it to the PDs. Most PDs will e interested in reading them and will appreciate the effort taken by your mentor. It is a bigggg plus.

5. If your rotations happened well before application season, stay in touch with your mentor through Emails, tell them about your progress. Once the application season begins, remind them of the LOR.

6. ERAS takes a maximum of two weeks to process the LOR during peak times. So, keep that in mind. Don’t keep them not uploaded till the last minute.

7.If your author is not uploading the LOR on time send them Emails with subject “gentle reminder” beginning July 15^th and tell them they have to upload by September 1^st or else you might not be able to apply for residency. Remember they are very very busy.

This whole information is through personal experience and from questions I usually find online. Hope this compilation helps. Feel free to ask questions or contribute to this. 😊

Give as you live <3

Much love <3

-Hyndavi

How to choose which residency programs to apply to?

Match season is coming and everyone is asking: What programs should I apply to :D ?
Well, there is no magical answer for this and each applicant has his/her own situation.

Below are some sources that may help in gathering some info about programs:

1- www.Matcharesident.com

This paid (79$) website provides a list of programs that you are eligible to apply to after filling the following requirements: USMLE scores, Visa Status, AMG or IMG, time since graduation, having US clinical experience or not and of course the specialty you are applying for.
It gives you a list of the programs, arranged alphabetically according to state with USMLEs and year of graduation cut-offs in addition to “IMG-friendliness” of the program among many other factors.

2- ERAS (Electronic Residency Application Service)

ERAS itself will show you all the programs available but without any filters, so you will need to check the website of each program individually to avoid applying for nothing. For example, ERAS won’t stop you from applying to a program in California even if you don’t have a PTAL - which is a requirement for all California programs.
Keep in mind is ERAS is the place where you apply to programs, so regardless of any source you use to create your list, ERAS is the final destination to choose programs from.

3- Website of each program

One of the most reliable ways to know about a program is to check the website itself. You ll find the info you need mostly under the name/title/tab of: Prospective Applicants or How to Apply and sometimes in the FAQ section.
Unfortunately, some programs websites are deficient and not organized or not even accessible. In this case, you ll have to use the other sources mentioned in this post to get the info you want.

4- FRIEDA (Fellowship and Residency Electronic Interactive Database)

FRIEDA is an online database of all graduate medical education programs in the United States that are accredited by the Accreditation Council for Graduate Medical Education
Click here to access FRIEDA or just search FRIEDA on Google. Make an account and enjoy searching. You can use filters like: states, visa sponsorship..etc.

5- Doximity

Doximity is an online social networking service for U.S. clinicians. You can create an account and see programs in different specialties arranged according to research output or reputation and US news ranking.

6- Already made lists

You ll find many lists circulating around the internet. You may use them too but an advise it to double check them and make sure that they are uptodate since programs policies may change over the years.


7- Asking seniors

Seniors may help and give you a more detailed insight about programs and states. Ask them :)
==
Tips:
> In order to apply to California programs, you need what is so-called: a PTAL ( Postgraduate-Training Accreditation Letter). For more information, click here.

> The situation may be different in different specialties. For instance, Peds has less than 200 programs which means searching will need less time and effort than IM which has 400+ progs!

> It is good to use more than one source. You can use matcharesident list in addition to checking ERAS and the website of each program. Matcharesident may rarely miss a program and sometimes programs show up late in ERAS.

> Search well and specify some good time to search programs. This is a very important decision that may affect the rest of your life :D

> Apply to all programs in a particular geographical location if you have a strong family tie and you REALLY want to match there. DO NOT MISS OUT ON ANY PROGRAM IN THAT CITY/STATE.

Wishing you a good Match season everyone :)

-Murad

MCQ Mnemonics Series: Age for organ donation

Minimum age required for consent to donate organs as per transplantation of human organ act:

16
18✔
21
no limit

Don *ate* *et* *eighteen* *etin*

Shubham Pathidar

SON 101

Statement of Need [SON]

1. What is the SON?

This is a document issued by the Ministry of Health[MOH] which states that they are lacking physicians in the required specialty and thus need more trained physicians. It also mentions that the concerned person signed a bond with the government that the person will return to his/her country after the required training within 2 months and will stay for at least 2 years or pay 5lakh rupees.

2. Who should apply for it?

Everyone applying for J1 -exchange visitor visa for residency must apply. People requiring H1b need not. It is also not required for J1-research scholar visa.

3. Where can I get the application form for SON?

You can get it from the ministry of health website here http://www.cgisf.org/page/display/292/236

4. What should all be included with the application form?

             a)Completed application form [ANNEX A, C, and D]

             b)Surety Bond [ANNEX I].

             c)Contract or offer letter.

             d)Copy of your passport.

             e)Copy of Visa if living out of the country.

5. How do I make the surety bond?

Surety bond should be made on a 100rs nonjudicial stamp paper. The format is in the application form. You can fill it out in the word format and print it out. Only the first page should be the stamp paper, Rest can be A4 sheets or judicial yellow pages without a stamp. It doesn’t matter how many pages it comes until you have everything in the bond. All the pages must be notarized and also be signed by you and your sureties.

6. How do I send it?

Via speed post or courier. Anyway, should be fine. Send it through something with a tracking number so that you know when it reaches. The following is the address:

Under Secretary (IC)

International Cooperation SectionMinistry of Health and Family Welfare(Department of Health & Family Welfare)Room No. 514, 'A' WingNirman Bhavan, New Delhi 110 011, India
x

7. I applied, what do I do now?

Call them after 2 working days from the time your application reaches @ Phone: (011-91-11) 2306-3068/2306-1945 or email @ soic-mohfw@nic.in and ask for your application number. They are pretty responsive to both but more to the calls. Also, ask them for the time frame of when it will be signed. The applications are numbered in the sequence they receive and are processed in the same sequence.

8. Should I personally go to submit or collect the form?

You can personally go in if you stay near Delhi. For submitting if you go, you save a couple of days which might not make much of a difference. Once the SONs are issued they are sent out in bulk and you will not have a tracking number. So, while collecting, when you collect it by hand you can send it to ECFMG from there itself you can save a week at least.

Do not forget to inform them if you are collecting by hand so that they keep your SON aside rather than posting it.

When you go to MOH, go to the gate 5 Nirman Bhawan, get a pass made[don’t forget your ID and tell them you are there for SON] and go and collect from ‘A’wing - Room No:514.

9. How do I send it to ECFMG?

MOH gives your SON in a sealed envelope which should be sent unopened to ECFMG. They also provide you with a copy and a letter stating that they gave your SON.

If you received it by post, you can open the main envelope inside which will be a smaller envelope with seal.

ECFMG address: EVSP/ECFMG, 3624 Market Street, Philadelphia, PA19104 USA.

You can send it through any courier service. DHL at some locations gives a student discount for this and charges around 1500rs. [Especially the one nearest to MOH]. Again, have a tracking number.

10. When does my J1 process start?

As soon as the ECFMG receives your SON they upload it into your documents on OASIS by title Ministry of Health letter within a week. If all the documents are perfect, you will receive a welcome letter within 1 week from then. It usually takes much lesser time than that. Once the welcome letter arrives you can fill in DS 160, pay the SEVIS fee and take an interview date.

TIPS:

   1. Apply for SON ASAP after you get your contract letter. The sooner you apply sooner is the whole process to get the visa.

   2. Read each and every line of application form multiple times and be careful while filling it out.

   3. Don’t forget to put your ECFMG ID in the application form.

   4. Call MOH or ECFMG when in doubt. They are pretty responsive. 

   5. Be patient. This process is time taking. Patience is much needed.

This whole information is through personal experience and from WhatsApp groups. Hope this compilation helps. Feel free to contribute or ask questions. 😊

Give as you live <3

Much love <3

-Hyndavi

Measuring size of OPA and NPA mnemonic

The oropharyngeal and nasopharyngeal airway are temporary airway devices. You need to select an appropriate size before inserting the airway.

Radiology series #1 X-rays 1.0

Hello awesomites!

Today I am starting a new series of posts on radiology. Here I will be mostly dealing with the theory and technical part of radiology which as an undergraduate student we rarely read. Starting off with x-rays in this post and CT, USG, MRI to follow in the consecutive ones!

X-rays

A little bit of history,

X-rays were discovered by W. C. Roentgen in Germany on 8^th nov 1895 and for which he received a Nobel Prize in 1901.

First let us know a few technical terms, collectively known as the ‘exposure factors: 

     1) kVP: kilovolt peak

     It determines the penetration of the x-ray beam through the body. High kVP implies more penetration of the body tissues

     2) mAS: milliampere second

     It determines the amount of blackening of the film. A high mAS will cause more blackening of the film for the same amount of x-rays hitting it.

      3) Contrast: It is the contrast shadow that is produced on the film i.e. white for bone and black for soft tissues. It is influenced mainly by the penetration of the x-rays i.e. the kVP and partly by mAS.

A low kVP (low penetration) means high contrast.

Contrast is proportional to 1/kVP

But,

A low mAS (less blackening) means low contrast.

Contrast is directly proportional to mAS

Let us take up an example,

In obese and heavily built patients, more penetrance is needed so we need to increase the kVP but if we do so by increasing the kVP we are reducing the contrast which is not good.

So to achieve both high contrast and good penetrance, kVP is increased as well as mAS is increased.Increased kVP will take care of the required penetrance while high mAS will ensure good contrast.

The general protocol to increase the contrast is first by reducing the kVP and then if necessary increasing the mAS to desired levels.

That’s all for now, more about the actual working of the x-ray machine and different settings in the next post. Hope you liked it !

Until then,

Keep calm and keep studying

Stay awesome!

-          Ashish G. Gokhale

Facebook: Penicillin

This is answer to one of the questions on chemotherapy posted on medicowesome facebook.
Question is as follow.

Which of the following statement about penicillin G is true

1) It is commonly administered orally.
2) It has a broad spectrum of antibacterial activity.
3) It can be used for the treatment of rate bite fever.
4) Concomitant probenecid decreases it's duration of action.

Answer is 3- It can be used for the treatment of rate bite fever.

Explanation:

Penicillins belongs to the group of Beta-Lactam antibiotics.
These group includes compounds having Beta-Lactam ring in their structure. Apart from penicillin beta-lactam antibiotic group includes following classes:-

Cephalosporins
Monobactams
Carbapenems

You can remember them as
"See PCM"

C(See)-Cephalosporins
P-Penicillin
C-Carbapenems
M-Monobactams

Now, coming to Penicillin G

1) It is not effective orally because of breakdown by acid in the stomach.
Hence, a seprate class of penicillins are introduced which are acid resistant.

A very famous mnemonic is: VODKA
V= Penicillin V
O= Oxacillin
D= Dicloxacillin
K= Cloxacillin
A= Ampicillin and Amoxycillin

2) It has short duration of action due to rapid excretion from kidney. To overcome this we do one of the two things
a) Benzathine and procaine groups are added to penicillin G
Benzathine is longest acting penicillin G
b) Probenecid can be administered with penicillins. It inhibits the tubular secretions.

3) Penicillin G has narrow spectrum of antibacterial activity. Several new penicillins with extended spectrum are added. They are as follow.

CAT Action MAP.
C= Carbenicillin
A= Ampicillin
T= Ticarcillin
A= Amoxicillin
M= Mezlocillin
A= Azlocillin
P= Piperacillin

4) It is first choice of drug for:-

Mnemonic: SMARt GV loves yogurt.
S=Syphilis
M=Meningococcal meningitis
A=Actinomycosis
R=Rat bite fever
t
G=Group A and B streptococcal infections
V=Viridian streptococcal endocarditis
L=Leptospirosis
Y=Yaws

Some important points to remember:

1) All drugs having beta lactamse ring are bacteriocidal.
2) They act on PBP(Penicillin binding proteins) present on cell membrane.
3) MRSA occur due to alterations in PBPs, hence no beta lactams are useful against it.

Facebook: TDK, CDK, PAE.

So, this post is about our chemotherapy question posted on facebook page.

Question is as follow

Time dependant killing and prolonged post-antibiotic effect is seen with:

1) Fluoroquinolones.
2) Beta-Lactam antibiotics.
3) Clindamycin.
4) Erythromycin.

Answer is 2- Beta lactam antibiotics

Okay, so let's get started.

Today we will learn about three simple and basic concepts of the chemotherapy.

1) Concentration dependent killing:
The killing effect of a drug is high when ratio of peak concentration to MIC(Minimum inhibitory concentration) is more.

Simplified version:
Suppose drug called as "A" kills a particular bacteria.
Now I am going to put 2 units of this drug in a medium containing that bacteria for 10 minutes. After 10 minutes when I check the medium I still find the living bacteria present. I wait for another 10 minutes. After total 20 minutes I recheck it - I still find living bacteria!

Now, I change the concentration of the drug "A" to 4 units but keeping the time same i.e. 10 minutes. Now, when I check the medium for bacteria after 10 minutes  I find dead bacteria. This means that antibiotic dose of 4 units is needed minimum for killing the bacteria irrespective of the time.

In a nutshell: These drugs need one large dose for their action rather than  multiple small doses

Drugs having CDK:
Mnemonics: CAFe

C=CDK
A= Aminoglycosides
F=Fluoroquinolones

2) Time dependant killing( TDK) :
This means the antimicrobial action depends on the length of time the concentration remains above MIC.

Simplified version:
Let's take the same example.

Now, "2 units" of drug A is kept for 10 minutes in a medium containing particular bacteria. After 10 minutes I check the medium and I find living bacteria. I add 2 units more and I wait for another 10 minutes like I did previously. But this time after total of 20 minutes I find dead bacteria!

Now, I again do this experiment but this time with 4 units of drug A.
I wait for 10 minutes
Result: Living bacteria
I wait for another 10 minutes( Total =20 minutes) without adding any further dose.
Result: Dead bacteria.

In a nutshell: In TDK, multiple doses are preferred over single dose!

Drugs having TDK:
Mnemonics : T.V. Box.

T= TDK
V=Vancomycin
B= Beta-Lactams

3) Post antibiotic effect (PAE):

After an organism is exposed to antibiotic, it's growth stops. When it is put in antibiotic free medium, the growth resume after sometime.
This is called as PAE.

PAE is seen when antibiotic concentration is below MIC.

Drugs showing PAE:
Most of the antimicrobials have long PAE against gram positive bacteria.

Drugs showing PAE against gram negative bacteria:
Mnemonic- CPD(cephalo-pelvic disproportion) nurse.

C= Carbapenems
P= Protein synthesis affecting drugs(Aminoglycosides, chloramphenicol, tetracyclines)
D= DNA synthesis affecting drug ( Quinolones, rifampicin)

N= Negative bacteria

Points to remember:

1) Rifampicin prolongs the PAE of isoniazid.
2) Macrolides and clindamycin also possess time dependent activity. However they are static drugs so we cannot use TDK term for them.