Regarding assessment of a patient presenting to the emergency department (ED) with undifferentiated dyspnoea, which ONE of the following statements is TRUE?
Answer: D: Differentiating the cause for dyspnoea in a patient presenting to the ED can be challenging because both congestive cardiac failure and pulmonary conditions such as COPD may coexist, especially in the elderly population. Contrary to popular belief, symptoms such as dyspnoea on exertion, orthopnoea, paroxysmal nocturnal dyspnoea and leg oedema have a low positive likelihood ratio (LR) for the diagnosis of congestive cardiac failure (CCF). Previous history of coronary artery disease raises our suspicion but does not help in the diagnosis. In contrast, third heart sound (gallop) found on examination, pulmonary venous congestion and interstitial oedema found on the CXR have high positive LRs therefore strongly support the diagnosis of CCF. Furthermore, clinical gestalt, raised jugular venous pressure (JVP) or hepatojugular reflex on examination, and presence of alveolar oedema on CXR are helpful in the diagnosis. Cardiomegaly found on the CXR may not be helpful.
Hypercapnoea (defined as PaCO2 >45 mm Hg) is the result of pulmonary hypoventilation due to a variety of causes. Hypercapnoea, both in its acute and chronic states, is associated with increased HCO3 production albeit due to different mechanisms. However, in the acute state the serum HCO3 level is normal, and in the chronic state, which starts after the first 6–12 hours of hypercapnoea the HCO3 level is often raised. In acute respiratory acidosis caused by hypercapnoea, the H+ ions are buffered by the intracellular proteins. The HCO3 produced in this process raises the serum HCO3 by 1 mmol/L for every 10 mm Hg rise in PaCO2 level in hypercapnoea (1:10 rise). In other words, this serum HCO3 rise is minimal in acute respiratory acidosis. In contrast, in chronic respiratory acidosis due to chronic hypercapnoea, as a means of buffering acid, renal retention of HCO3 occurs. In this process serum HCO3 raises by 3.5 mmol/L for every 10 mm Hg rise in PaCO2 (3.5:10 rise). These figures can be used to differentiate acute from chronic hypercapnoea and to identify acute-on-chronic hypercapnoea in clinical practice.
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Venous blood gas (VBG) analysis is increasingly being used in the place of arterial blood gas (ABG) analysis in the ED.
Which ONE of the following statements is TRUE regarding its use?
Answer: C: Blood gas analysis is performed in the ED mainly to assess:
ABG sampling is notorious for producing significant pain to the patient and repeat sampling requires repeated needle punctures or insertion of an arterial line. Arterial sampling is not without serious complications – occasionally arterial injury and thrombosis may occur. In contrast, venous sampling is much easier to perform and has other technical advantages.
Currently available evidence suggests venous pH, HCO3 level and base excess to have sufficient agreement with the same arterial parameters in patients in most clinical situations such as diabetic ketoacidosis. However, there is no data to confirm that this level of agreement is maintained in shock states, cardiac arrest and mixed acid–base disorders and therefore VBG should not be used in these states.
The mean difference between venous and arterial pH varies between 0.02 and 0.035 pH units. Currently available evidence shows that the agreement between the venous and arterial PCO2 to be poor. Venous PCO2 is not a substitute for arterial PCO2 in clinical situations such as acute exacerbations of COPD and asthma. An ABG should be done in these patients to detect hypercapnoeic respiratory failure.
Reference:
The chest X-ray (CXR) of a 65-year-old female smoker presenting to the ED with a history of recent onset worsening dyspnoea reveals a moderately large left-sided pleural effusion.
In determining the cause of this pleural effusion, which ONE of the following statements is TRUE?
Answer: D: A patient with a newly diagnosed pleural effusion should be carefully assessed to determine the cause of the effusion. As a first step in the ED, a careful history, physical examination and investigations should be performed to differentiate pleural effusion into one of either exudate or transudate.
Transudative causes include:
Exudative causes include:
A diagnostic thoracocentesis should be performed and pleural fluid should be tested for protein and LDH levels. Exudative pleural fluid will fulfill at least one of the following Light’s criteria. The vast majority of the transudative effusions will not fulfil any of these criteria:
The presence of transudative effusion will usually mean the patient requires treatment of the underlying condition, but exudative pleural fluid should be tested further for white cell count and differential, glucose level, microscopy, culture/sensitivity and cytology to establish the underlying cause. Overall, the most common cause of pleural effusion is heart failure in which isolated right-sided effusions are more common than left-sided effusions. Often the effusions are bilateral. When effusions are not bilateral, when there is a significant difference in effusion sizes and when heart failure diagnosis is unclear, diagnostic thoracocentesis should be considered to rule out other potential causes.
Empyema is a grossly purulent effusion and it is often loculated and pleuraly based. This is visible in the CXR as a pleuraly based collection. PE is often overlooked as a cause of an effusion. During patient assessment this should be carefully considered, especially in patients with small pleural effusions.
Regarding life-threatening massive haemoptysis in an elderly patient, which ONE of the following statements is TRUE?
Answer: D: Haemoptysis can originate from both bronchial vessels (systemic circulation) and from alveolar capillaries (pulmonary circulation). About 90% of massive haemoptysis originate from bronchial arteries. Rapid and large haemorrhage caused by the systemic arterial pressure can drown the patient before any chance of clearance of the airway. Therefore, the cause of death in massive haemorrhage is usually due to asphyxia rather than exsanguination. Although some practitioners will position the patient with the bleeding side down to prevent blood from going in to the non-bleeding lung, this can be detrimental to the patient as it worsens ventilation perfusion mismatch. Usually, the non-bleeding lung is intubated to prevent blood entering in to that lung. Selective intubation of a non-bleeding right lung can be easily attempted in the ED by advancing the ETT to the right main bronchus.
This will occlude the bronchus to the right upper lobe and ventilate the right middle and lower lobes. Successful selective intubation of the left lung may require considerable skills. A 90-degree rotational method using a size 7 mm endotracheal tube (ETT) after passing through the cords can be tried in the ED to enter either the right or left side. The success rate is described at 94% for the right side and 72% for left side. Double lumen tubes require fiber optic method.
Regarding a patient presenting to the ED with haemoptysis, which ONE of the following statements is TRUE?
Answer: C: CXR abnormalities can be identified in the majority of patients who present with haemoptysis due to lung malignancy.
PE is a common cause of haemoptysis; however, it usually does not cause severe haemoptysis. The chance of identifying the bleeding lesion is highest if the bronchoscopy is performed within the first 48 hours. When associated with right upper lobe collapse, it is usually due to a lung malignancy.
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