cough cough WHEEZE

A patient in the middle of an asthma attack, has respiratory alkalosis.

In respiratory alkalosis, ABG  values are:

 

pH 7.40

pCO2<40 (due to the rapid breathing rate that expels CO2)

elevated pO2 

(remember, with asthma it's problem getting the air OUT, hence the expiratory wheeze)

The work of breathing during an asthma attack is increased to overcome the constricted airways leading to an increase in lactic acid in the respiratory muscles.

Intubation is usually avoided in asthmatics, but cannot be avoided if the breathing muscles are exhausted. This "tiring out" is seen on ABG when the pH begins to normalize because this "normal" pH is a sign that the patient is unable to remove CO2 and lactic acid is building up. 

So let's say, you have an asthmatic patient, having an asthma attack and his pH is 7.39 (usually considered normal), it is a ominous sign that the patient is going into respiratory failure.

INTUBATE! 

*of course, i must mention: if the pH normalizes because you have administered treatment, it means the treatment is adequate and there's no need to stick a tube down your patient's throat. the 'normal-abnormal pH rule' (i just coined that term...hee) only applies if the patient presents to the ER, with acute asthma, but ABG shows a normal pH.

cough cough

isoniazid (INH) should never be prescribed as a monotherapy for TB (unless the patient has a positive PPD, but a negative CXR = no clinical manifestation of TB) because it can induce resistance via these two mechanisms:

• decrease bacterial expression of catalase peroxidase enzyme for INH inactivation once the drug enters the bacterial cell AND
• modification of protein target binding site of INH

 a mnemonic for remembering first line antiTB drugs:

If you forget your TB drugs, you'll die and might need a PRIEST
Pyrazinamide
Rifampin
Isoniazid (INH)
Ethambutol
STreptomycin

the dirt on anticoagulants

Warfarin

Indication:

• afib
• mechanical valves
• DVT/PE

Overdose:

• bleeding to death: administer fresh frozen plasma (FFP) stat and give vit K (takes some days to work)
• only elevated INR (no active bleeding): hold coumadin, and give vit K if INR dangerously high

What's good about it?

• can be given as oral tabs (patient not subjected to shots all the time)
• CHEAP!

What's bad?

• takes a couple of days to reach a therapeutic level
• hard to reverse
• hard to regulate

Really bad stuff to watch out for:

• Warfarin skin necrosis (happens because protein c and s are the first to go, leaving factors 10, 9, 7, and 2 unopposed = proclotting phenomenon)

Heparin

Indication:

• DVT/PE (occurred in hospital)
• acute MI
• non-hemorrhagic stroke
• DIC

Overdose:

• bleeding to death = administer protamine sulfate!
• increased PTT = stop heparin 

Good:

• rapid action
• easy to monitor
• easy to reverse
• pregnant woman can use it

Bad:

• IV/SC only
• have to administer often (8 hours and with minimal gaps between administration to prevent thrombus formation [system overreacts in absence of heparin])
• variable response to same dose

Worse than bad:

• heparin induced thrombocytopenia (HIT): platelets drop down about 50% in a few days (<50,000). absolutely NO HEPARIN PRODUCTS
• thrombosis (arterial or wacky venous thrombosis)
• treat HIT by withholding ALL heparin products, argatroban, lepirudin. not even enoxaparin can be administered coz can cause HIT 5% of time.

Enoxaparin

Uses:

• acute MI
• DVT/PE
• pregnant women with DVT

Overdose:

• Active bleeding give FFP and stop treatment with drug

Why good?

• pregnant women can use it
• longer t1/2
• no monitoring (dose according to weight and get results)

Why bad?

• EXPENSIVE!
• SC
• HIT
• needs dose adjustment if patient hasRF

Pulmonary Hypertension (PHT)

PHT can be caused by:

1. HYPOXIA due to a pulmonary disease
   
   • hypoxia causes changes in the endothelial cells of the pulmonary arteries (PA) causing an increase in vascular resistance
   • COPD is the MCC of hypoxic vasoconstriction of the PA
2. VOLUME OVERLOAD due to a decompensated cardiac disorder
   
   • an increase in LA volume (MI, valvular heart disease, CHF) causes an increase in PA pressure
3. IDIOPATHIC dysfunction of the endothelium cells = primary pulmonary HT
   • increase in thickness of the vascular wall (apoptosis dysfunction)
   • decrease in production of prostacyclin and NO 
    

Pulmonary HT can cause RV hypertrophy and because the RV has less compensatory capability, RVF can develop rapidly (cor pulmonale). So you can expect symptoms such as:

• dyspnoea on exertion
• distended neck veins
• chest pain
• increase intensity of P2 and paradoxical splitting of S2
• holosystolic tricuspid insufficiency murmur (due to dilation of the AV ostium) that increases with inspiration (remember the mnemonic: rIght = increase at Inspiration).
• hepatomegaly 
• peripheral edema

a, b, c of achalasia

achalasia: absence of relaxation.
both liquid and solids dysphagia.
barium swallow will show bird peak.
treat with botulinum toxin or balloon dilation (pneumatic dilation).
calcium channel blockers is another treatment option.
chaga’s disease may cause secondary achalasia.
achalasia is associated with an increased risk of esophageal carcinoma.
complication: reflux of food so, don't forget aspiration syndrome!

gold standard investigation to diagnose is manometry showing failure of the LES to relax, as well as the absence of peristaltic waves in the upper esophagus.
perform an endoscopy to rule out malignancy.

let's talk immunodeficiencies

you're on your peds round today. first patient on the roll has a gene defect where he can't make myeoloperoxidase and this is the cause of his recurrent infections. do you know why myeloperoxidase is essential? what mechanism does this boy lack and therefor is susceptible to infections?

his immune cells can't engage in respiratory bursts. myeloperoxidase catalyzes the conversion of H2O2 and chloride ions into hypochlorus acid, which is 50 times more potent at killing microbes than H2O2 alone. so the boy's neutrophils are weakened.

next patient to come in: he's just like the previous patient...has recurrent infections, BUT this time the defect is in microtubules and phagocytosis. he has severe gingivitis and oral mucosa ulceration and albinism.

your patient has CHEDIAK HIGASHI disease (not too common, but we are talking immunodeficiencies today). kid will have strep and staph infections. you prescribe acyclovir (which i know, is an antiviral...but acyclovir boosts recovery and fights off viruses). the globins you'd later transfuse will deal with the strep and staph. remember: mouth stuff, recurrent infections, hypopigmentation: chediak higashi!

right then. you want your coffee break, but another patient gets sent to you. he has recurrent bronchopulmonary infections (bacterial), thymus aplasia, telengiectasias, growth retardation and you noticed when he walked in, he sort of waddled more than walk.

kid has? *drum roll*

ATAXIA TELEANGECTASIA! both B and T cells aren't functioning. his alpha fetoproteins will ALWAYS be high. keyword here: ataxia (waddling).

you beg the nurse to let you off, but she's already got the patient into the room. this time you got a little dude, 2 years old. you look at the chart and see that he has had lots of bacterial and fungal infections and his mum says the white stuff has come again. what does the kid have? what is the white stuff the mum's talking about?

little dude has severe combined immunodeficiency aka SCID. the white stuff is candida. kid will have IL-2 deficiency. you must start TMP-SMX prophylaxis for pneumocystis carinii (it's called something else now...change in nomenclature...pneumocystis jiroveci!) coz kids with SCID usually die from this infection.

so, you think you'd sneak out for that coffee, but you prolly know the story by now. yet another kid walks in with an immunodeficiency. the kid has increased reflexes, you think his face looks abnormal, you notice he has a congenital heart disease, labs says he's hypocalcemic and CXR shows no thymus...where did it go?! 

the child has DiGeorge's disease aka thymic aplasia. his 3rd and 4th arch failed to developed. problem with parathyroid gland as well...hence hypocalcemia.

you stretch, thinking you've had enough of kids with immunodeficiencies but your day has only just begun. another kid comes in with his mum. he has recurrent otitis media, eczema and thrombocytopenia from strep pneumonia. his IgM is low and he bleeds easily. what's the Dx?

he has XLR wiskott-aldrich syndrome! there's a tendency to get infections from capsulated bugs like strep pneumonia (have you read my post on capsulated bugs? if you haven't, here it is). kid will have LOW IgM, HIGH IgA (which sort of makes up for the low IgM so he's not as bad as the kid with SCID...all he needs is amoxicillin or ceftriaxone). so remember: attacks from capsulated bugs, BLEEDING, otitis media, eczema = wiskott-aldrich syndrome.

you thought you hit gold for getting all those Dx right, but another kid comes in. you grumble, but you remember you took the oath and sold your soul to saving lives (doesn't that just warm you up inside?), so you grab the patients chart and go see her. yeah, let's make this kid a female one, aight. you palpate her lymph nodes and notice she has lymphadenopathy. her liver is palpable too (hepatomegaly). she's tiny for her age (growth retardation) and looks like she has chronic skin infections. you suspect something's up with her phagocytes (hint! hint!) and sent her sputum for culture. it comes back positive for Aspergillus. you know for sure now, that she has?

CHRONIC GRANULOMATOUS DISEASE! granulomas are the skin stuff she has (recurrent skin infections) and key points: Aspergillosis and phagocyte deficiency!

you say goodbye to the little girl and just as she leaves, a guy pushes his kid in. "doctor! my kid has wiskott-aldrich syndrome!". you cock your eyebrow at him, get a little annoyed everyone has access to webMD and google, but don't show this to him of course (ethics!). the dad goes on to explain that he was talking to this lady in the waiting room and her kid was diagnosed with wiskott-aldrich syndrome and he has the same symptoms as the dude's son. of course you can't take the dad's word for it and proceed to examine the kid yourself. you find that he has recurrent infections yes, diarrhea sometimes. has low IgG. and his B cells lack CD19. does he have wiskott-aldrich?

nope. kid has Bruton's agammaglobulinemia (aka X-linked agammaglbulinemia...X-linked meaning boys are affected more often). very similiar to wiskott-aldrich (also X-linked), BUT remember the key point for wiskott aldrich was BLEEDING! this kid doesn't have that. he has a problem with his B cells, coz he has a defect in the Bruton's tyrosine kinase gene (Btk gene) which means he has a defect in B cells developement (they can't mature). kid has the same susceptibility to encapsulated organisms (seriously, read that post on capsulated bacteria! it will help you), with recurrent otitis media, eczema and other bacterial infections. treatment would just be transfusing Igs.

so you give yourself a pat on the back, crick your neck muscles and are about to call it a day, but the nurse promises you, 'just one more!', so you be the good guy (or gal) and say, 'bring it on!'. this kid comes in. just like the others, he has recurrent infections, BUT his are limited to sinopulmonary infections (bacterial). he's older than most of the other kids you saw today and is pretty asymptomatic otherwise. oh, and he tells you, he almost always has diarrhea. i've technically just given you the diagnosis. what is it?

IgA deficiency. his IgG and neutrophils would be normal, but he has a problem with local immunity (nasopharynx and small intestine, remember please that IgA's found in these places). 

TADA. what a day, eh? are you rocking internal medicine or what? =)

Jarisch-Herxheimer Rxn

You get a 30 year old female patient, with classic presentation of secondary syphillis (condyloma lata, mucuous patches in mouth), whom you treat with IM penicillin.

Six hours later, the woman is back, feverish, complaining of chills, malaise, headaches and myalgia. You check and find that she's tachycardic and mildly hypotensive.

what do you do?

NOTHING :) Yeap, you read that right. Nothing.

Your patient is just experiencing the Jarisch-Herxheimer reaction, which consists of fever, chills, mild hypotension, headache, and increase in intensity of mucucutaneous lesions 2 hours after initiating treatment of syphillis with penicillin. These symptoms usually subside within 12-24 hours without any treatment.

This reaction occurs in 50% of patients being treated for primary syphillis and 90% of patients with secondary syphillis.

Interestingly, this reaction also occurs after treatment of other spirochetal diseases (eg: relapsing fever caused by Borrelia recurrentis). It is thought that this symptom complex is produced by release of treponemal lipopolysaccharides.

So, the next time you get a patient that comes in with these symtpoms after you tried treating them for syph, don't panic! You did nothing wrong.

*of course don't brush off your patient's symptoms if they include: diffuse rash, wheals, angioedema, wheezing, because don't forget: penicillin can cause allergies in individuals sensitive to it!!

mnemonics

Drugs with zero order kinetics :
Just remember this mnemonic - Constantly aspiring to phone Ethan.

Constantly - zero order kinetics
Aspiring - Aspirin
to Phone - Phenytoin
Ethan - Ethanol

cerebellar signs :
DANISH
D - dysdiadochokinesia
A - Ataxia
N - Nystagmus
I - Intention tremor
S - Speech ( slurred speech)
H - Hypotonic

Want to differentiate negative cocci N. meningitides and N. gonorrhoea with cultures?
The sugar fermentation test brings you....
N. Gonorrhoea ferments Glucose only
N. Meningitides ferments Maltose as well

cyanide toxicity

• causes
• infusion with nitroprusside
• smoke inhalation (MCC)
• effects
• inhibits cytochrome oxidase (cytochrome a/a3) of the electron transport chain
• NOT cytochrome C!!!!!!!! (commonly mistaken)
• blocks the use of oxygen → tissue hypoxia and death
• signs & symptoms
• bitter almond-scented breath
• agonal respiration (seen at cerebral ischemia, hypoxia or anoxia = shallow, slow irregular breathing accompanied by irregular pauses)
• nausea and headache
• treatment
• amyl and sodium nitrite
• produces methemoglobin (metHb)
• metHb sucks up cyanide from the mitochondria
• iron in metHb (Fe3+) has stronger affinity for cyanide than cytochrome oxidase’s iron
• results in formation of cyanomethemoglobin
• sodium thiosulfate
• converts cyanomethemoglobin into:
• thiocyanate
• less toxic & easier to excrete than cyanomethemoglobin
• methemoglobin
• methemoglobinemia is treated with methylene blue

got milk?

hypomagnesemia can cause hypocalcemia since magnesium is necessary for the production of PTH.

adrenal cortex

the three layers for the adrenal cortex can be remembered using the sequence: GFR.

to remember what each layer produces, remember: salt, sugar, sex...it gets sweeter the deeper you go (G: mineralocorticoids, F: corticosteroids, R: sex hormones) .

the Glomerularis layer is stimulated by RAT (renin-angiotensin). F&R are both stimulated by ACTH.

key point: estrogen causes GROWTH.

• estrogen comes from: ovaries, adrenal cortex, and placenta.
• estrogen causes closure of the growth plates, which is the reason why women are shorter than men. so if a young girl presents with signs of early puberty, you must treat that to prevent her from being too short.
• a really high FSH means that estrogen is low and the FSH is trying to stimulate the ovaries to produce more estrogen. a high FSH is an indicator of menopause or ovarian failure.
• estrogen stimulates the growth of breasts, so too much of it is associated with breast cancer. in men diagnosed with cirrhosis, the liver cannot metabolize estrogen so this leads to gynecomastia and spiderangiomatas.
• estrogen also induces the growth of the endometrium. again, too much of it can lead to endometrial carcinoma.
• it increases albumin production in liver, so in a pregnant woman, the increased albumin binds more thyroid hormone, increasing the total T4. free thyroid hormone however remains the same.
• it also increase coagulation factors production in the liver, leading to increased clotting.

Wasn't Me!

So a patient presents with persistent pain at the tip of his shoulder. Quite possibly, he slept on it, and you tell him that it'll go away. Spot a flaw?


There's a possibility that your patient'll come back with an acute abdomen.


The sensory innervation of the shoulder is from the supraclavicular nerves, which have their roots at C3 and C4.

Sound familiar? C3 & C4 (Along with C5) are the roots of the phrenic nerves, which are mixed nerves. There's usually nothing interesting sensory going on in the diaphragm, but in case of any nearby pathology that causes diaphragmatic irritation : stomach, gall bladder, spleen etc, the sensory impulses of irritation from the diaphragm are interpreted as pain in the shoulder because they share the same roots.



So explore the possibility of referred pain, specially if your patient presents with an inexplicable pain in an innocuous area, that's rather suspicious!

Duodenum: Lengths of Parts

Counting 1 to 4 but staggered:

1st part: 2 inches
2nd part: 3 inches
3rd part: 4 inches
4th part: 1 inch

"Some Nasty Killers Have Some Capsule Protection":

that's the mnemonic for bacterias that have capsules:

Streptococcus pneumoniae
Neisseria meningitidis
Klebsiella pnemoniae
Haemophilus influenzae
Salmonella typhi
Cryptococcus neoformans
Pseudomanas aeruginosa

you're prolly thinking...great, i'll just memorize this for the exam then. this is where i show you, that it's also important for you as a diagnostician to remember something as minute as which bacteria is capsulated:

say, you get a patient who is asplenic, or has IgG/C3b/ macrophage deficiency. your patient is at an increased risk for infections from the above bugs because they lack what it takes to kill with encapsulated organisms. so is someone who doesn't have a functional spleen (sickle cell) or a person with Bruton's agammaglobulinemia.

the capsule is a virulence factor for the above organisms and can induce and immune response and the formation of antibodies against it. which means vaccines can also be made against the capsule for bugs such as Pneumococci, Meningococci and H. influenzae type b.

now, how do we know that these bugs are capsulated to begin with? these organisms test positive for the Quellung reaction, where anticapsular antibody binds to the organism's capsule causing it to swell and become more visible, especially under the microscope.

so remember: "Some Nasty Killers Have Some Capsule Protection".

petting pets

infections you get from a cat/dog's bite, scratch, and urine.

bite: Pasteurella multicidas
scratch: Bartonella henselae
urine: Leptospira interrogans

plugged

did you know that while a fetus floats around in utero, it makes poop?

this poop, is called MECONIUM. unlike normal poop however, meconium, is odorless and is blackish in colour, viscous and sticky like tar, and almost sterile as it is largely made up of stuff the fetus ingested, e.g epithelial cells, amniotic fluid, mucus and lanugo (which btw is fetal hair...also seen in teratomas). 


normally, it is stored in the fetus's intestines and excreted postpartum. sometimes it is expelled into the amniotic fluid or during labour (i suppose when this happens, the fetus is literally scared shitless about coming out into the world...hee~).

if a newborn fails to poop out its meconium within 48 hours, you should immediately be worried about two things: Hirschsprung's disease and cystic fibrosis.

Hirschsprung's disease is a condition where the enteric plexus ganglions are absent causing a lack of peristalsis, which leads to obstruction and then dilation of the colon up to the formation of megacolon.

in cystic fibrosis, the meconium is thickened and it congests the lumen of the intestines, a condition known as meconium ileus. this is often the first sign of cystic fibrosis.

the area proximal to the area of obstruction caused by meconium is distended and the infant will present with a distended stomach and vomiting.

a negative digital rectum pretty much confirms Hirschsprung's disease. mind you, it can also be a sign that the baby did poop out something, but you just missed it...so you would need to assess then whether or not the baby is excreting normal poop now that it has started being fed milk and if that's a negative as well, along with the other symptoms mentioned above, you'll need to first work on emptying the baby's obstructed bowel and then getting a confirmatory biopsy and referring the case to a surgeon.

for cystic fibrosis, the parent may complain that the infant tastes 'salty' when they kiss its skin. however, only 20% of cases of cystic fibrosis present at infancy with meconium ileus. most of the time, the symptoms appear later on in childhood, with respiratory problems and symptoms of malabsorbtion.

Fail!

Ejection fraction is a quantitative measurement of systolic efficiency calculated by the formula:


SV/EDV %


where SV = EDV-ESV.


The quantitative measurement of diastolic efficiency is called injection fraction.


It is calculated by the formula: (ESV-EDV)/EDV %


The other measure of diastolic efficiency is E/A ratio, which is the ratio between the filling velocity in early diastole(passive) and late diastole(due to atrial contraction - active)

The determination of diastolic efficiency is important in the diagnosis of Diastolic dysfunction or diastolic heart failure, where abnormalities in the compliance of ventricular myocardium and/or abnormalities in the valves might interfere with diastolic filling.

The initial diagnosis of diastolic dysfunction is made if the patient presents with symptoms of heart failure but ventricular function is normal.

one red blood cell too many

rbc mass is the total number of rbc's in entire body in mL/kg body weight.
rbc count is the total number of rbc's per microliter of blood (amount of rbc in a certain volume of blood).


so why is understanding these definitions a big deal?

say for example, you went running today and ended up being volume depleted. your rbc count would increase, because there's a decrease in plasma volume, BUT your rbc mass would be unchanged (no additional synthesis of rbc). this is called a RELATIVE POLYCYTHEMIA (it only looks like there's more rbc per microliter of blood because of the decreased plasma volume).

now, an ABSOLUTE POLYCYTHEMIA, involves an increase in the rbc count as well as an increase in the rbc mass, which can be either a appropriate increase or an inappropriate increase.

when would it be appropriate for the rbc mass to increase? when there is a need for more rbc's to be synthesized because of TISSUE HYPOXIA (lung disease, hypoxemia, COPD, high altitude). erythropoetin is released from the kidneys in response to hypoxia, and it stimulates rbc proliferation in the bone marrow.

but what if there is an increase in the rbc mass, with normal blood gasses (no tissue hypoxia)? this would constitute an INAPPROPRIATE absolute polycythemia. usually it is caused by polycythemia rubra vera, a neoplastic disease of the bone marrow (the stem cells proliferate unchecked).

an inappropriate response can also be caused by an non physiological (excess) production of erythopoetin from a tumor, renal cyst, or renal adenocarcinoma. it could also be due to an exogenous intake of erythropoetin, usually seen in athletes who do this to increase their performance.

so to sum it up: polycythemia can be relative or absolute. relative means you just lost plasma volume, so your rbc count would be increased, but your rbc mass is normal (looks like you have more rbc's, but actually you are just volume depleted, so your rbc count is hemoconcentrated). absolute: is it appropriate? anything that is a hypoxic stimulus for eythropoetin. if there isn't a hypoxic condition (normal blood gasses), then it's an inappropriate increase due to an ectopic production of erythropoetin (from a tumor, cyst, renal cancer) or a myeoloproliferative disorder that causes proliferation of rbc's (polycythemia rubra vera).

SHOCK!

In a state of Hypovolemia (mostly Hypovolemia, but I'd like to think Hypoperfusion due to any cause), perfusion to organs is maintained by 4 mechanisms:

(Life) SA-VER

(1) Sympatho-Adrenal System

(2) Vasopressin

(3) Endogenous digitalis-like factor

(4) Renin-Angiotensin system.


When I originally heard of this mnemonic, it also included for A: Atrial Natriuretic peptide. I didnt think that appropriate, because ANP is secreted in response to Hypervolemia, and acts by decreasing cardiac output. That's hardly going to save any lives.

of pearls & granulomas

Try imagining a pearl as a primitive granuloma

Layers of nacre deposited   (T lymphocytes)

surrounding an area of irritation   (collection of macrophages/giant cells)

in the mantle of an oyster.

To link such a beautiful thing to a... say, caseating granuloma... X_X

Interstitial Lung Disease

Mnemonic CHHAARTS (top of the charts = upper lobe)

C = coalworkers
H = hypersensitivity
H = histiocytosis
A = allergic bronchopulmonary aspergillosis (ABPA)
A = ankylosing spondylitis
R(T) = radiation
S = silicosis

most of these are inhalational,
hence manifestation in the upper lobe,
where V > Q

Mnemonic RAISE (from the bottom = lower lobe)

R = rheumatoid arthritis
A = asbestosis*
I = idiopathic pulmonary fibrosis
S = scleroderma
E = exogenous drugs

mostly systemic,
carried in bloodstream
*exception to the inhalational agent-upper lobe 'rule'