8. Cardiothoracic Flashcards

Question

20. You are comparing pressure– volume curves in asthmatic patients during an acute asthma attack and comparing it with healthy subjects. Which of the following observed differences is the best indicator of the increased work of breathing in the patients with asthma? A. Larger hysteresis loop B. Longer expiratory time C. Pressure– volume curve starts at a higher end- expiratory pressure D. Slope of the inspiratory limb is initially less steep E. Tidal volume is smalle

Answer 1

A. Larger hysteresis loop

Answer 2

Dilated cardiomyopathy results in impaired ventricular function secondary to progressive dilatation. Patients present with symptoms of chronic heart failure, embolic events, or arrhythmias.

Answer 3

The important anaesthetic management aims are to maintain sinus rhythm, avoid tachycardia, and reduce or avoid increases in afterload. Cautious fluid management is important and should be goal directed. Preload should be maintained especially in the presence of elevated left ventricular end diastolic pressure, but fluid overload should be avoided

Answer 4

Pacemakers are coded as per a standard international system. 1. The first letter denotes chamber paced (V, ventricle; A, atrium; D, dual). 2. The second is chamber sensed (V, A, D) 3. The third is the mode of response (T, triggered; I, inhibited; D, dual). 4. The fourth letter denotes any programmable functions. 5. The fifth letter refers to special antitachycardia factors.

Answer 5

A. An FEV 1 of 1.1 L

Answer 6

A preoperative FEV1 of >1.5 L generally indicates suitability for lobectomy. Less than this would require further investigation and may preclude surgery. If qualitative lung function tests confirm a predicted postoperative FEV1 ≥40% and a predicted postoperative TLCO ≥40%, it would be safe to proceed to surgery

Answer 7

Arterial PaCO2 ≥6 kPa does not appear to be an independent predictor of poor outcome. Oxygen saturation ≤90% has been associated with an increased risk of complications.

Answer 8

The transplanted heart has no autonomic innervation and the resting heart rate will sit around 100 bpm due to loss of vagal tone. This denervation also alters the pharmacological response to some commonly used anaesthetic drugs. Vagolytics such as atropine and glycopyrrolate have no effect on a denervated heart. Metaraminol would not treat the bradycardia

Answer 9

Ephedrine, adrenaline (epinephrine), and isoprenaline could all be used to give positive chronotropy but they should be used cautiously as there may be an exaggerated response. Adenosine also demonstrates denervation hypersensitivity and should be used in smaller doses.

Answer 10

Wherever possible, use should be made of synergistic, balanced, multimodal analgesia. Thoracotomy is notoriously painful postoperatively and creates a challenging acute postoperative pain management issue. Additionally, good acute pain management in thoracotomy may reduce the incidence of chronic neuropathic pain. The decision as to which technique to use for a particular patient is usually a matter of the anaesthetist’s preference and local unit practices.

Answer 11

Regional and neuraxial methods have obvious advantages but are associated with patchy coverage and a significant failure rate. Some afferent routes will not be blocked by the techniques described above (for example diaphragmatic irritation via the phrenic nerve) and many patients will also have chest drains inserted.

Answer 12

If additional systemic analgesics can be administered, global analgesia will be improved. Regular paracetamol, NSAIDs where appropriate, parenteral or oral opioids are good choices in addition to a regional technique, embracing the doctrine of balanced multimodal analgesia

Answer 13

The patient can be assumed to have a secondary spontaneous pneumothorax due to his age >50 years and significant smoking history. However, the pneumothorax is small based on the chest X-ray measurement and there are no obvious signs of current respiratory compromise. Therefore, an initial attempt can be made at aspirating air with a 16–18G cannula. The volume should be less than 2.5 L and the attempt at aspiration should abruptly cease indicating an expanded lung with no ongoing air leaks. A follow- up chest X- ray should demonstrate an improvement in pneumothorax size (<1 cm), otherwise a chest drain will subsequently be required

Answer 14

If a secondary pneumothorax is larger (>2 cm) or the patient is breathless, then chest drain insertion is the correct initial action. All patients with a secondary pneumothorax should be admitted, commenced on oxygen therapy, and observed for 24 hours.

Answer 15

Changes in airway pressures occur commonly during thoracic procedures. The clue as to their cause is often related to the most recent intervention. This should be considered as well as general differential diagnoses. In this case the patient has just been turned onto their side and even slight movement of the endotracheal tube can change airway pressures significantly if, for example, the tube moves further into a main bronchus or occludes a lobar bronchus. Positioning of the tube should be reconfirmed each time the patient position is changed.

Answer 16

Auscultation of the chest may reveal areas without air entry or reduced air entry but this is less reliable due to transmitted sounds and ambient noise in theatre. If the patient is thought to be coughing, then suctioning of mucous and ensuring adequate muscle relaxation would be relevant. The capnography trace may confirm an obstructive pattern of air flow but may also be normal. It does not help to identify the cause of the problem.

Answer 17

The work of breathing is the work required to move the lungs both in inspiration and in expiration. During inspiration the work is to overcome airway resistance and during expiration it is to overcome compliance. On a pressure–volume curve the work of breathing is best indicated by the area within the hysteresis loop. Hysteresis means that the curves in inspiration and expiration are different

Answer 18

In obstructive ventilation disorders such as asthma, more work is needed to overcome the flow resistance, particularly if positive intrapleural pressures are generated in expiration and this will be reflected in a larger hysteresis loop on the curve

8. Cardiothoracic Flashcards

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