Respiratory Part 2 Flashcards
Explain what TB is?
- Tuberculosis is a bacterial infection by mycobacterium tuberculosis which are bacilli
- Although most commonly TB symptoms are in the lungs TB can affect all systems
- TB does not gram stain because the bacteria has a waxy coating
- Infection of TB is by inhalation
7 groups who are at higher risk of TB infection?
- Known contact with active TB
- Immigrants from areas of high TB prevalence
- People with relatives or close contacts from countries with a high rate of TB
- Immunocompromised individuals e.g. HIV, those on immunosuppressive medication
- Homeless
- PWID
- Alcoholics
Describe primary infection with TB?
- Primary infection occurs in those who have not been previously exposed to TB or vaccinated against it
- A small Ghon focus at the periphery of the lung is the site of infection and there is lymphatic spread to the hilar lymph nodes, some caseous masses may form
- In most patients the lesions undergo fibrosis or calcification and heal
- Spread however can occur
Side note: unclear whether you can entirely clear TB from your body after initial infection or if everyone who gets TB goes on to develop latent TB
Describe and explain 4 types of TB?
- Active TB – active infection in various areas within the body
- Latent TB – immune system encapsulates sites of infection and stops progression – no symptoms but bacteria remain (can remain for years) and can be reactivated
- Secondary TB – this is when latent TB reactivates, this only occurs if immunocompromised in some way e.g. elderly, HIV, alcoholic, diabetic, immunosuppressant medication
- Miliary TB – occurs when the immune system is unable to control the disease and it is disseminated and severe
What is a ghon focus?
a lesion in the lung that is the site of primary TB infection, they are usually subpleural and predominantly in upper or middle lobe
Presentation of active TB?
- Productive cough (sometimes haemoptysis)
- Weight loss
- Fever
- Night sweats (red flag symptom for TB)
- Loads of symptoms of TB at other sites
Describe the 2 screening tests for immune response to TB?
- Mantoux test – inject tuberculin (TB proteins) into skin, look for reaction after 72 hours – test will be positive in someone with BCG vaccine, active or latent TB
- Interferon gamma release assay (IGRA) – blood test looking to see if WBC release interferon gamma in response to TB antigens – this is not affected by BCG vaccine and if positive means latent or active TB
- Mantoux test is generally done first and then if that is positive you get the IGRA test
- Those who have a positive Mantoux and IGRA should be assessed for symptoms of active TB and go on to have a CXR to check
Appearance of TB on chest xray?
- Primary TB– patchy consolidation, pleural effusions, hilar lymphadenopathy
- Reactivated – patchy or nodular consolidation with cavitation
- Disseminated – miliary TB- millet seeds distributed throughout the lung fields
Staining for TB?
- Ziehl Neelsen staining is traditionally used on sputum samples – it stains acid fast bacilli – i.e. mycobacterium bright red against a blue background
- Auramine staining is a newer fluorescent dye that is more sensitive
- These stains can be used on direct smear or on paraffin sections or cultures that have taken time to grow
- Direct smear testing will provide rapid results but you need a higher bacterial load to see results so it won’t pick up everyone
Describe cultures for TB?
Taking cultures allows you to test for resistance however they can take months to grow so treatment is usually started before results are back
also allows you to identify subtypes
Can take:
1. Sputum samples – if patient producing sputum this is easy if not may need to do bronchoalveolar lavage (during bronchoscopy saline solution put through bronchoscope to wash airways and catch a fluid sample)
2. Blood cultures – need special TB blood culture bottle for this
3. Lymph node aspiration/ biopsy
Biopsy for TB shows?
caseating granulomas
Investigation overview for TB?
Pathology - caseating granulomas
Microbiology
Stain for AFB - presence of mycobacterium
PCR/ NAAT - specific for TB and can also show if rifampicin resistant TB but can pick up dead bacteria
culture - for acuity and further sensitivities - culture takes weeks
Describe management other than drug treatment that should be done in TB?
- Overall management involves informing public health and contact tracing
- Anyone with active TB needs isolated to avoid spread until established on treatment (usually 2 weeks)
- Those with TB should also be tested for HIV, Hepatitis B and C
Describe treatment of latent TB?
- These patients don’t necessarily need treatment and are not contagious
- However, it is recommended due to risk of developing active TB later in life if/ when they may become immunocompromised
- Treatment of latent TB involves isoniazid and rifampicin for 3 months and isoniazid for a further 3 months
Describe treatment of active TB?
- 2RIPE4RI
- 2 months of rifampicin, isoniazid, pyranzamide and ethambutol, 4 months of only rifampicin and isoniazid
Describe all the side effects of TB drugs?
- Rifampicin turns body secretion orange/ pink, it is also a potent inducer of cytochrome P450 meaning it reduces the effectiveness of a number of drugs including the COCP
- Isoniazid causes peripheral neuropathy and should be co-prescribed with pyridoxine (vitamin B6)
- Pyranzamide can cause hyperuricaemia and gout
- Ethambutol can cause colour blindness and reduced visual acuity
- Rifampicin, isoniazid and pyranzamide are all associated with hepatotoxicity
- Redandorange-picin, isonumbizid, eye-thambutol, pyranzamide (p for painful joints)
What TB drug turns body secretions orange/ pink?
rifampicin
What should isoniazid be co-prescribed with and why?
pyridoxine (vitamin B6) - because isoniazid causes peripheral neuropathy and this reduces risk of this developing
What TB drug can cause gout?
pyranzamide
What TB drug can cause colour blindness and reduced visual acuity?
ethambutol
List the 3 TB drugs associated with hepatotoxicity?
rifampicin, isoniazid and pyranzamide
List the components of Virchows triad?
- The three main factors leading to thrombus are known as virchows triad: alteration of blood flow (stasis), changes in the composition of blood (hypercoagulability) and endothelial damage
Explain what a pulmonary embolism is?
- Blood clot that forms in the pulmonary arteries usually as a result of a DVT in the legs that has embolised
- Once in the pulmonary artery flow to the lung tissue is blocked and there is also strain put on the right side of the heart due to this blockage
- This can cause ischaemia and infarction of lung tissue
List 9 risk factors for VTE?
- Immobility
- Recent surgery
- Long haul flights
- Pregnancy
- Oestrogen therapy e.g. HRT or COCP
- Malignancy
- Polycythaemia
- SLE and other inflammatory conditions
- Thrombophilias e.g. anti-phospholipid syndrome, factor V Leiden, protein C deficiency, protein S deficiency etc.
Describe presentation of PE?
DVT: swelling in one leg, throbbing or cramping pain, red or darkened skin, swollen veins
PE:
* Symptoms can be very non-specific
* Sudden onset shortness of breath is most common symptom
* Cough
* Pleuritic chest pain
* Haemoptysis
* Hypoxia
* Tachycardia and tachypnoea
* Low grade fever
Note: pleuritic chest pain and haemoptysis are generally only present when infarction has occurred
Explain initially how you would go about making a diagnosis of a PE?
- History
- Examination – low grade fever, hypotension (sign of right heart strain), tachycardia, tachypnoea, pleural rub (squeaking or grating caused by ischaemic lung tissue coming in contact with the pleura), hypoxia, evidence of DVT
- CXR – want to rule out other potential causes of these symptoms as DVT is very non-specific
- NICE recommend at this point you should then go on to do a Wells score which essentially gives you result of either PE likely or PE unlikely
What is the most common ECG finding of a PE? What is the classical ECG finding?
most common finding is a sinus tachycardia but the classic finding is S1Q3T3 – a large S wave in lead 1, a Q wave in lead 3 and an inverted T wave in lead 3 indicate acute right heart strain
Describe what you do if PE likely/ unlikely on Wells score?
PE likely on Wells Score (more than 4):
* https://www.nice.org.uk/guidance/ng158/chapter/Recommendations#diagnosis-and-initial-management
* offer CTPA immediately, if not possible do a V/Q scan
PE unlikely on Well Score (4 points or less) :
* Offer a d-dimer test
* Only if d-dimer positive should then do a CTPA, if negative consider an alternative diagnosis
* d-dimers are 95% sensitive but not very specific, i.e. if d-dimer is negative that can exclude a PE but if it is positive it does not diagnose it
Initial management of PE?
- For those with diagnosed PE should start treatment with anticoagulants
- Everyone is also usually given high flow O2 and analgesia
- If no renal impairment, active cancer or haemodynamic instability first line drugs are apixaban or rivaroxaban
- LMWH can be used as alternative as well as edoxaban, dabigatran etc.
- Those who are haemodynamically unstable due to massive PE should be considered for thrombolysis, thrombolysis comes with risk of massive bleeds so should only be used in massive PE, examples include streptokinase, alteplase and Tenecteplase
When may you use thrombolysis in PE? Why do you not use it on everyone?
- Those who are haemodynamically unstable due to massive PE should be considered for thrombolysis, thrombolysis comes with risk of massive bleeds so should only be used in massive PE, examples include streptokinase, alteplase and Tenecteplase
Long term management of PE?
- Anticoagulation should be continued for at least 3 months
- Should perform investigations to determine underlying cause based on history etc. e.g. do they have a malignancy? Do they have a thrombophilia?
- At 3 months (3 to 6 months with active cancer), stop and discuss with patients benefits vs risks of stopping vs continuing
- HERDOO2 score can be used for looking at risks of discontinuing anticoagulation in unprovoked PE
- HAS-BLED score can look at risk of major haemorrhage if stay on anticoagulation
- Generally those with a provoked DVT where factor has now been controlled it is okay to stop anticoagulation and those with unprovoked should be encouraged to stay on anticoagulation
Explain what a pneumothorax is?
- Pneumothorax occurs when air gets into the pleural space separating the lung from the chest wall
- It can occur spontaneously or be due to trauma, medical interventions or lung pathology
Explain what a spontaneous pneumothorax is and classical presentation?
- These generally occur when bullae which are abnormal air pockets that form in the lung rupture
- A primary spontaneous pneumothorax occurs in someone with no underlying condition and these are more common in thin, tall, adolescent males
- Spontaneous pneumothorax is also common in Marfan’s syndrome
Presentation of a pneumothorax?
- Small ones can be asymptomatic
- Acute onset of pleuritic chest pain and SOB
- Hypoxia
- Tachycardia
- Reduced breath sounds on the affected side
- Hyper-resonance
- Deviated trachea away from side of pneumothorax in tension pneumothorax
Management of a pneumothorax?
Primary:
* If pneumothorax < 2cm and the patient is not short of breath then no treatment is required there should just be a follow up CXR
* If the patient is short of breath or the pneumothorax is > 2cm aspiration should be done
* If aspiration fails (patient still short of breath or pneumothorax > 2cm still) then a chest drain should be inserted
Secondary:
* > 2cm or breathless - chest drain, admit
* 1-2 cm in size - aspirate, admit
< 1cm admit, high flow oxygen, observe for 24 hrs
secondary if age > 50 with significant smoking history or evidence of underlying lung disease on exam or CXR
Describe the triangle of safety for inserting a chest drain?
Chest drains should be inserted into the “triangle of safety” – 5th ICS (nipple line), mid axillary line (anterior border of latissimus dorsi), anterior axillary line (lateral border of pectoralis major) – should also make sure you insert just above a rib to avoid hitting a neurovascular bundle (these run beneath each rib)
Explain what a tension pneumothorax is?
- A one way valve forms so air can only move into the chest which results in compression of mediastinal structures and deviation of the trachea away from the involved lung
- Tension pneumothorax is a medical emergency
Management of a tension pneumothorax?
- Emergency management of a tension pneumothorax involves insertion of a large gauge cannula into the pleural cavity via the 2nd or 3rd intercostal space in the midclavicular line of the side of the tension pneumothorax
- Definitive management would be with a chest drain
Explain what pulmonary hypertension is?
- Increased resistance and pressure of blood in the pulmonary arteries – this puts strain on the right side of the heart and also causes back pressure of blood into the venous system
- Variety of causes which can be classified into 5 groups
WHO classification system for pulmonary hypertension?
- Group 1 – idiopathic
- Group 2 – secondary to left heart disease, valvular heart disease or restrictive cardiomyopathy (because left sided heart failure causes backflow into the lungs)
- Group 3 – secondary to chronic lung disease and environmental hypoxaemia
- Group 4 – due to chronic thrombotic disease, embolic disease or both
- Group 5 – miscellaneous, systemic disorders (e.g. SLE), haematological diseases etc.
