Acute Respiratory 486/12 Flashcards
- COPD precipitations
Common precipitants of exacerbations of COPD include: • infection (60–80% of exacerbations) – common bacterial causes include Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis. Common viral causes include influenza, parainfluenza, coronaviruses and rhinoviruses • non-infectious causes (20–40%) are due to heart failure, pulmonary embolism, pneumothorax and non-pulmonary infections • precipitating and environmental factors such as cold air, air pollution, allergens, ongoing smoking and non-adherence to prescribed medication.
- COPD investigations
Inx COPD - spirometry - ECG - CXR (looking for potential complications; pneumothorax, pneumonia or heart failure) - Inx may not be needed if clinical history and examination suggests infective cause
- COPD Initial Rx infective exacerbation-
- short-acting bronchodilators (inhaled beta 2 agonists such as salbutamol or terbutaline) - oral corticosteroids; the recommended dose of prednisolone is 30–50 mg daily for 7–14 days (without tapering) - oral antibiotics; five days of therapy with either doxycycline 100 mg twice daily or amoxycillin 500 mg 8 hourly is recommended.2 Macrolide antibiotics are often ineffective, and are likely interact with warfarin leading to a significantly elevated international normalised ratio (INR).
- COPD Rx Severe exacerbation at home, then in hospital
- ambulance - continue bronchodilators inhaled or nebuliser until ambulance arrives –> IV steroids –> O2 via nasal prongs most effective –> blood gases, ECG, CXR –> spirometry not in acute setting –> admission Specific therapy in the emergency department would include titrated oxygen therapy (aiming for oxygen saturations (SaO2) of 90–92%, inhaled bronchodilators, corticosteroids and antibiotics. The dose and route of administration of these medications are guided by the severity of illness. Non-invasive ventilation is useful in the setting of acute respiratory acidosis, and has been shown to reduce mortality and the need for intubation. It often leads to rapid clinical improvement. Occasionally, intubation and ventilation may be required if non-invasive ventilation is ineffective or contraindicated.
- PE
Symptoms - pleuritic chest pain - SOB - syncope Ddx - cardiac causes (acute ischaemia, arrhythmia, pulmonary oedema and pericarditis) and - respiratory causes (pleural effusion, pneumonia and pneumothorax).
- PE INx
- CXR - ECG - Bloods; FBC, EUC (creatine for contrast) - D -dimer if low pretest probability - ventilation/ perfusion (VQ) scan or a CT pulmonary angiogram (CTPA). A VQ scan uses lower doses of radiation (approximately 1.3 mSv), and is therefore preferred in younger patients. However, there is a significant possibility of a non-diagnostic scan, which would necessitate further testing, particularly in patients with a history of COPD or an abnormal initial CXR. A CTPA is more sensitive and cost-effective than VQ scanning, however, risks include contrast reactions, renal impairment and a much higher radiation exposure (estimated to be 8–10 mSv). The latter is an important consideration in young women, where breast tissues receive a significant radiation dose.
- PE pre test probability
The simplified Wells score (Table 1) is recommended in the draft National Institute of Clinical Effectiveness (NICE) guidelines
- PE Rx
Hospital admission and treatment with subcutaneous low molecular weight heparin (LMWH).
Warfarin is likely to be commenced, and the LMWH continued until her INR is in the target range of 2–3
Recently, alternative oral anticoagulants such as rivaroxaban and dabigatran have been trialled in patients with PE with promising results.
At this stage, neither drug is listed on the pharmaceutical benefits scheme for this indication.
Other trials are aiming to identify a group of patients with PE who may be safely treated as outpatients.
- PE and pregnancy
Plasma D-dimer is more likely to be elevated in pregnancy than in the non-pregnant state. However, a negative D-dimer is still useful
in a patient with low pre-test probability for PE, as further testing
is not necessary. An elevated D-dimer should prompt lower limb ultrasonography, which may demonstrate a reason for anticoagulation without the use of ionising radiation.
If an ultrasound of the lower limbs reveals no thrombus and a PE still needs to be excluded, then definitive imaging (VQ or CTPA) should occur. The estimated radiation absorbed by the fetus depends on the modality chosen and gestational age
Appropriate initial chest imaging should be either a CTPA or perfusion-only lung scanning.
If a PE is confirmed, then LMWH is recommended in the pregnant patient. Warfarin is not recommended during the first or third trimesters, and caution should be used if given in the second trimester. Anticoagulation should be continued for 3 months after delivery, and warfarin is safe in breastfeeding.
- CAP Assessing severity
It is important to assess the severity of pneumonia in order to
make a decision on appropriate treatment and the need for hospital admission. Consider the patient’s age, comorbidities, vital signs and the presence of clinical manifestations of organ system failure.
Various scoring systems can also be used to assess the severity of pneumonia and include the Pneumonia Severity Index (PSI)16 (this uses information such as the patient’s age, comorbidities, vital signs and blood tests), CURB-65 (this uses information such as presence of confusion, urea level, respiratory rate, blood pressure and
age >65 years), CRB-65 (this uses similar information to CURB with the exception of urea),17 and SMART-COP18
- CAP severity
It is important to assess the severity of pneumonia in order to
make a decision on appropriate treatment and the need for hospital admission. Consider the patient’s age, comorbidities, vital signs and the presence of clinical manifestations of organ system failure.
There is no evidence supporting one scoring system over another. None can replace clinical assessment. Care must be taken when using scoring systems with younger patients. Severely ill patients requiring ICU care do not need scoring systems. Patients classified in a higher risk group are those with comorbidities and who are more likely to have an atypical presentation and worse outcomes.19
- CAP Inx
- A CXR should be performed in all patients with presumed pneumonia.
- Oxygen saturation and
- investigations for the causal pathogen should also be done. This may include sputum gram stain and culture, and blood cultures in patients who require hospital admission. - - Arterial blood gases should be done on severely ill patients.
Other investigations may be appropriate depending on the clinical circumstances. These include
- sputum for mycobacterium tuberculosis,
- urine antigen testing for pneumococcus,
- upper respiratory tract samples for polymerasechain reaction for respiratory tract viruses,and
- serological tests can be performed for Legionella spp. or mycoplasma pneumoniae if epidemiological reasons exist. Haematology and electrolytes may also be appropriate.
- CAP Guidelines for treatment
You could use Therapeutic Guidelines: Antibiotic.
The British Thoracic Society (BTS), American Thoracic Society and the Infectious Diseases Society also publish guidelines (see Resources).
Hospitals will also have local protocols depending on local epidemiological conditions.
- CAP Symp Rx
- A patient with CAP should be advised to rest and drink plenty of fluids.
- Oral analgesia, such as paracetamol or NSAIDS, can be used for chest pain. Smoking cessation advice should also be offered to all patients who smoke.
- Review a patient with CAP at 24–48 hours in order to detect patients who are deteriorating despite treatment.
- CAP causative organisms
Streptococcus pneumoniae, mycoplasma pneumoniae and respiratory viruses are the most common aetiological agents for CAP in Australia.
Atypical pneumonia (about one in five cases of CAP) is caused by organisms such as mycoplasma pneumoniae, chlamydia pneumoniae and Legionella spp. In one study, over 30% of culture positive CAP had co-infection with either a virus or atypical pathogen. The real figure is likely to be higher.
- CAP ABx choice
There are several antibiotic guidelines for CAP. For patients managed as an outpatient, Therapeutic Guidelines: Antibiotic recommends the following:
amoxycillin 1 gm 8 hourly for 5–7 days OR
doxycycline 200 mg for the first dose then 100 mg doxycycline daily for a further 5 days OR
clarithromycin 250 mg 12 hourly for 5–7 days.
Antibiotics should be given as soon as the diagnosis is confirmed.
Macrolides have been proven to markedly reduce mortality in CAP and hospital acquired pneumonia. They are anti-inflammatory, cause less cell lysis and are active against mycoplasma and even some viruses. There is evidence that narrow spectrum therapy with a penicillin and macrolide or doxycycline is as effective as broader spectrum regimens such as cephalosporins and fluoroquinolones, even in severe pneumonia.
Patients should be reviewed at 24–48 hours and if there is no improvement, combination therapy with amoxycillin plus either doxycycline or clarithromycin may be appropriate.
Broad spectrum antibiotics and antibiotics not conforming with current guidelines risk Clostridium difficile associated diarrhoea and methicillin resistant Staphylococcus aureus (MRSA). They also have significantly higher rates of treatment failure and mortality.
Studies on the aetiology of CAP in Australia show that less than 5% of identifiable pathogens are resistant to standard therapy.
It is recommended that antibiotic therapy should be continued for 5–7 days, and extended depending on response and clinical judgement.
Duration of treatment depends on response.
- CAP immunocompriomised patients
In immunocompromised patients, organisms may be atypical such as Klebsiella pneumoniae, Haemophilus influenzae or Morexella catarrhalis, or typical organisms can present atypically. For example, pneumonia due to Streptococcus pneumoniae may rapidly progress to septic shock, organ dysfunction and death
Pneumonia is 3–4 times more common in patients with diabetes.
Streptococcus pneumoniae and Legionella pneumophillia are associated with much higher mortality and morbidity and Staphylococcus aureus, gram negative Bacilli Mucor and mycobacterium tuberculosis are more commonly isolated.
