WEEK 9 Flashcards
What is the terminology used to describe a part of a CXR that is too black/black in the wrong place? What pathology does this suggest?
Increased translucency
- air (gas)
- loss of tissue density
What is the terminology used to describe a part of a CXR that is too white/white in the wrong place? What pathology does this suggest?
Opacification
- fluid
- increased tissue e.g. lymphadenopathy (at hilum)
If part of a CXR is really, really white or very radio opaque, what could this suggest?
Think HARDWARE
- pacemaker
- endotracheal tube
- nasogastric tube
- sternal wiring
- prosthetic heart valves
- CVP line
- chest drain
When describing any abnormality, how do you explain WHERE said abnormality is?
Using ZONES (upper, middle and lower) Also specify if left or right sided abnormality
What is consolidation?
Replacement of normal air space gas with fluid/solid material
If a normal airspace is filled with (i) pus (ii) blood (iii) fluid (iv) cells (v) protein, what disease(s) could this suggest?
(i) infection (pneumonia)
(ii) pulmonary haemorrhage
(iii) pulmonary oedema, drowned lung
(iv) lung cancer
(v) alveolar proteinosis
What is atelectasis? (also can be referred to as collapse but the former is preferred)
Reduction in inflation of all or part of the lung
What on a CXR would make you suspect atelectasis? (HINT: there’s 6 things)
Volume loss Displacement of trachea Displacement of diaphragm Displacement of lung fissures Compensatory over inflation of non collapsed lung Crowding of vessels and bronchi
What are the causes of a deviated trachea (i) towards pathology (ii) away from pathology?
(i) pneumonectomy/lobectomy, lobar collapse
(ii) tension pneumothorax, (massive) pleural effusion, or any mass effect.
What does the ABCDE mneumonic stand for with regards to abnormalities seen on a CXR of a pt with pulmonary oedema?
A - alveolar oedema (bat wings) B - kerley B lines C - cardiomegaly D - upper lobe diversion E - pleural effusions
What is pneumoperitoneum?
When there is significant air underneath the peritoneum of the diaphragm
What does air in the soft tissues suggest?
Subcutaneous emphysema
What are the hidden areas when examining a CXR?
Apices
Behind the heart
Mediastinum: widening, adenopathy, mediastinal emphysema
But remember the hilum too!
What condition pushes the trachea away, has increased opacity, is dull to percuss on examination and decreases vocal resonance?
Pleural effusion
What is the pKa for carbonic acid/bicarbonate?
6.1
Describe a Davenport Diagram
pH<7.35 = acidosis
pH>7.45 = alkalosis
AB shows plasma pH changes as CO2 changes
CD shows plasma pH change when non-volatile acid (lactic acid, those derived from phosphate etc) is added/removed (static PCO2)
NOTE: volatile acid = CO2 based
What are the causes fo acid base disturbances?
increased CO2
Decreased CO2
Increased non-volatile acid/decreased base
Decreased non-volatile acid/increased base
What type of disorder is it if the primary change is to (i) CO2 levels (ii) bicarbonate?
(i) respiratory disorders
(ii) metabolic disorders
What is (i) acidosis (ii) alkalosis caused by?
(i) rise in PCO2, fall in HCO3-
(ii) fall in PCO2, rise in HCO3-
What are the 2 ways the lungs and kidneys try to return any disturbances to normal (i.e. compensation)?
- Respiratory system alters ventilation - immediate response
- Kidneys alter excretion of bicarbonate - takes 2-3 days
What are the various causes of respiratory acidosis?
COPD Blocked airway - foreign body/tumour Lung collapse Injury to chest wall Drugs reducing respirator y drive e.g. morphine, general anaesthetics, barbituates
What is the 2 compensations done for respiratory acidosis?
An increase in PCO2 causes increase in H+ so plasma HCO3- levels increase to compensate for increased H+
Renal - increased HCO3- reabsorption and increased HCO3- production, raising pH to normal
Respiratory acidosis results form an increase in PCO2 which is caused by what 2 things?
- Hypoventilation (less CO2 being blown away)
2. V/Q mismatch
Respiratory alkalosis results from a decrease in PCO2 generally caused by what?
Alveolar hyperventilation
- more CO2 being blown away
Decrease in H+ and therefore rise in pH
What renal compensation is done for respiratory alkalosis?
reduced HCO3- reabsorption and reduced HCO3- production
- thus plasma HCO3- levels falls fall, compensating for lower H+, moving pH back towards normal
What are the causes of respiratory alkalosis?
Increased ventilation, from hypoxic drive in pneumonia, diffuse interstitial lung diseases, high altitude, mechanical ventilation
Hyperventilation - brainstem damage, infection driving fever
What does metabolic acidosis result from?
Excess of H+ in the body, which reduces HCO3 levels.
Respiration is unaffected, therefore PCO2 is initially normal.
How is metabolic acidosis compensated for?
Lower pH detected by PCRs,
=> increase in ventilation which lowers PCO2.
Bicarbonate equation is driven further to the left, lowering H+ and HCO3-
concentration further
Decrease in H+ conc moves pH towards normal
Resp compensation can’t fully correct pH, HCO3 and H+, so excess H+ needs to be removed or HCO3- restored (by slow renal compensation)
What are the causes of metabolic acidosis?
loss of HCO3- e.g. form gut in diarrhoea
Exogenous acid overloading (aspirin overdose), endogenous acid production (ketogenesis)
Failure to secrete H+ e.g. in renal failure
What does metabolic alkalosis result from?
Increase in HCO3- conc or fall in H+
- raising pH
How is metabolic alkalosis compensated for?
increase in pH detected by PCR - decreases ventilation which raises PCO2
Eqn is driven further to the right, increasing H+ and HCO3-
Increase in H+ moves pH towards normal
Resp. compensation is often small - ventilation cannot reduce enough to correct imbalance
Renal response to secrete less H+
What are the causes of metabolic acidosis?
Vomiting - loss of HCl from stomach
Ingestion of alkali substance
Potassium depletion
What are the 3 bacterial cell wall inhibitors?
Beta-lactams
Vancomycin
Bacitracin
- the osmotic pressure in cytoplasm of bacteria is high and membrane doesn’t remain intact when cell wall is damaged
What are the classes of antibiotics active against the cell membrane? Give names examples.
- Beta-lactam and cephalosporin
- pen. G, Fluclox, Tazobactam - Glycopeptide
- vancomycin, teicoplanin - Cyclic peptide
- bacitracin, polymyxin - Phosphonic acids
- fosphomycin - Lipopepides
- daptomycin
What is the (i) target and (ii) mechanism for Beta-lactams and cephalosporins?
(i) penicillin binding proteins
(ii) preventing peptidoglycan crosslinking
What is the (i) target and (ii) mechanism for glycopeptides?
(i) C-terminal D-Ala-D-Ala
(ii) prevents transglycolation and transpeptidation
What is the (i) target and (ii) mechanism for cyclic peptides?
(i) C55 - isoprenyl pyrophosphate
(ii) prevents carriage of building-blocks of peptidoglycan cell wall outside fo the inner cel membrane
What is the (i) target and (ii) mechanism for phosphonic acids?
(i) murA protein
9ii) inhibits first stage of peptidoglycan synthesis
What is the (i) target and (ii) mechanism for lipopepides?
(i) cell wall stress stimulation
(ii) calcium-dependent membrane depolarisation
What is the difference between penicillin G and V?
G is only administered parentally but V can be given orally
Give examples of B lactamase resistant penicillins, what spectrum do they target?
Methicillin, oxacillin, cloxacillin, dicloxacillin, naficillin
- same spectrum as ordinary penicillins
Give examples of B lactamase resistant penicillins, what spectrum do they target?
Methicillin, oxacillin, cloxacillin, dicloxacillin, naficillin
- same spectrum as ordinary penicillins
Give examples of broad spectrum penicillins.
Ampicillin and amoxicillin
- same as G and V but also beta lactamase free strains of H.influenzae, N.gonorrhoeae, E.coli, salmonella, sinusitis
Give examples of extended spectrum penicillins
Carbenicillin, ticaracillin, azlocillin, piperacillin
- covers borad spectrum bacteria plus pseudomonas aeruginosa
What is the structure and function of carbapenems?
Broad spectrum (more so than penicillins and cephalosporins)
Resistant to typical beta-lactamases as they bind to them, which acetylates it => inactive
Active against both Gram +ve and -ve bacteria and anaerobes but poorly active against MRSA
- it is NOT active against bacterial without a cell wall
What are the different beta-lactamase inhibitors?
There's 3 classes of beta-lactamases (A, B and C) Clavulanic acid and salbactam = strong class A inhibitors NOT B and C
What is an alternative approach to the use of beta-lactamase-resistant antibiotics?
the co-administration of beta-lactamase inhibitors with a beta-lactam antibiotic
What are cephalosporins? What conditions are they used to treat? Give examples.
Cefalexin, cefurtaxime, cefotaxime, cefadroxil
Basically same as penicillins hence why they are often used as alternatives.
There are fewer of them and they are classed by generation
used against septicaemia, pneumonia, meningitis, biliary tract infections, UTIs, sinusitis
What is vancomycin? What is its MoA? What is it used to treat?
Glycopeptide
It binds to the peptide chain of the peptidoglycan. It interferes with the elongation of the peptidoglycan backbone
It’s a very specific interaction with D-Ala-D-Ala which explains the minimal development of resistance
MRSA and resistant streptococci and enterococci
What is bacitracin? What is its MoA? What is it used to treat?
Polypeptide that is bactericidal
It interferes with the dephosphorylation of the lipid carrier which moves the early cell wall components through the membrane
Ointment to treat skin and eye infections by streptococci and staphylococci
What are the 2 types of bacterial folate antagonists? What is their MoA?
Sulphonamides and Trimethoprim
- inhibit folate pathway in bacteria = selective toxicity target
Sulphonamides act on PABA
Trimethoprim acts on dihydrofolic acid
What are the therapeutic uses of sulphonamides and trimethoprim?
T - community UTIs
Can be combined to treat toxoplasmosis - Co-trimoxazole
Used in combo with other drugs for opportunistic infections in AIDS pts e.g. pneumonia
Name 2 examples of macrolides. What are they used for? What is their MoA?
Used as penicillin alternative. Active against mycoplasma Chlamydia Legionella, used in management of community acquired lower resp tract infection
Active against:
- H.influenzae, corynebacterium (diptheria), camphylobacter (diarrhoea), chlamydia trachomatis, toxoplasma gondii (in pregnancy)
Also against helicobacter pylorii in combo with other agents
What are the adverse events/ side effects of (i) erythromycin (ii) clindamycin?
(i) Mild gut disturbances, hypersensitivity reactions, transient hearing disturbances and rarely cholestatic jaundice
(ii) Mild GI disturbances but pseudomembranous colitis can occur and can be fatal
What is the lincosamide class of clindamycin active against? What is it used to target/treat?
Active against gram +ve cocci including staphylococci, and a wide range of anaerobic species including bacteroides species
Used in eye drops for staphylococcal conjuctivitis
In combo against anaerobic sepsis and necrotising fasciitis, for staph infection of joints and bones
What are aminoglycosides used to treat? What side effects can occur?
They are reserved for treatment of serious infections
- enterobacteriaceae and pseudomonas (septicaemia and serious UTIs)
- hospital acquired pneumonia, resp and intra-abdominal infections due to pseudomonas
- brucellosis, yersinia pestis (plague)
Side Effects: renal toxicity due to damage of kidney tubules. Ototoxicity which can result in vertigo, ataxia and loss of balance as well as auditory disturbances (deafness). Neuromuscular block if drug is given with a neuromuscular blocker
What are the pharmacokinetics of aminoglycosides? (HINT: there’s 4 points)
- Polar agent confined to ECF
- Doesn’t cross BBB
- Excreted by kidney
- Must be administered IV
When should you be cautious about the use of aminoglycosides?
elderly, renal failure, severe sepsis which is causing acute renal failure
What are the uses of tetracyclines?
Rickettsial, mycoplasma and chlamydial infections, brucellosis, cholera, plague and Lyme disease
Tigecycline used in resistant gram -ve infection
Used in COPD and chronic acne
What are the side effects of tetracyclines?
Gut upsets Hepatic and renal dysfunction Photosensitivity Binding to bone and teeth causing staining, dental hypoplasia and bone deformities Vestibular toxicity (dizzy and nausea)
When is chloramphenicol used?
Limited to indications for serious infections when no other drug is suitable (because of its low risk of aplastic anaemia)
indications = meningitis and brain abscess
What is topoisomerase IV?
Tetrameric enzyme of 2 ParC and 2 ParE sub-units
Involved in chromosomal partitioning as it catalyses ATP dependent relaxation of negatively and positively supercoiled DNA and unknotting of un-nicked duplex DNA