Cardiothoracics Flashcards
- What interventional (non-pharmaceutical) options are there for treating chronic (not acute) coronary artery insufficiency
Coronary artery insufficiency occurs due to insufficient blood flow through one or more coronary arteries and is almost always due to atherosclerotic disease.
Coronary artery insufficiency can be managed conservatively via medical management or by intervention if indicated.
Indications include:
- intolerance to medical therapy
AND
- patients in categories believed to have better prognosis after intervention than medical treatment. Such patients have increased risk of adverse cardiovascular event due to diseased vessels and/or LV dysfunction.
The interventional options for treating chronic artery insufficiency include:
- Percutaneous Coronary Intervention (PCI)
- Coronary Artery Bypass Grafting (CABG)
PCI is preferred for single vessel diseases and is achieved under local anaesthetic by passing a catheter and guidewire from femoral or radial artery through the stenotic coronary artery.
A balloon is then inflated to achieve patency of the vessel and a bare metal or drug eluting stent may be placed.
In patients with multi-vessel disease, stenosis of Left Main Coronary Artery and diabetes, CABG has been demonstrated to be superior to PCI.
Bypass of arterial occlusion is achieved with grafting of the saphenous vein or internal thoracic artery. The saphenous vein is attached proximally to the ascending aorta and to the coronary artery distal to the site of occlusion. The internal thoracic artery remains attached to the subclavian artery, and is attached distally to the coronary arteries. A combination of saphenous vein and Internal Thoracic Artery is used where the saphenous bypasses the LAD and ITA bypasses the other vessels.
- What are the indications for a pneumonectomy in a patient who has been found to have a primary non-small cell lung cancer?
Primary lung cancers are classified into small cell lung cancer (SCLC) and non-small cell lung cancer (NSCLC).
SCLC is usually treated non-surgically due to the very high risk of metastasis and better responsiveness to chemoradiotherapy than NSCLC.
NSCLC is further classified into three main types:
Squamous cell carcinoma
Adenocarcinoma
Large cell carcinoma
Surgical management is indicated for patients:
o With stage I or II NSCLC and selected few with stage IIIa with :
- Disease limited to one lung
- No nodal involvement or some ipsilateral nodal involvement
- No distant metastasis
AND those that are Medically fit for operation with an adequate pulmonary function and without any other serious comorbidities
Pneumonectomy is a resection of the whole lung and is performed less commonly than lobectomy.
Pneumonectomy is indicated for a central tumour involving the distal main stem bronchus, or involvement of ipsilateral hilar lymph nodes that are otherwise not resectable.
- What are the principles of a heart lung bypass perfusion circuit (machine)?
The heart lung bypass perfusion circuit temporarily replaces the function of the heart and lungs during surgery to maintain systemic circulation and oxygenation of the blood. It is commonly used in cardiac surgery to provide a bloodless, stable surgical field.
Preparation involves:
- high-dose heparin anticoagulation
- priming the bypass circuit with crystalloid, heparin and mannitol
- administration of cardioplegic solution
AND
- reducing the patients systolic BP just before aortic cannulation
The procedure involves draining blood from a canula in the RA and diverting it through the venous line and into the venous reservoir.
The arterial pump then withdraws blood from the reservoir and passes it through a membrane oxygenator, a heat exchanger and a filter before returning the blood via the arteria canula into the ascending aorta.
Coming of the bypass:
- temperature, blood pressure and electrolytes are ensured to be back in physiological range and anticoagulation is reversed with protamine sulphate.
- What are the advantages and disadvantages of using a mechanical valve to replace an aortic or mitral valve, rather than a tissue valve?
In general, both types of replacement valves work very well. But there are pros and cons with each one.
Mechanical valves are made from a special type of carbon or titanium and other sturdy materials. The material allows for greater durability, availabilty and a lower risk of infective endocarditis.
However, they are thrombogenic and requires lifelong anticoagulation with Warfarin.
Furthermore, haemolytic anaemia occurs more frequently than bio valves and if endocarditis does develop the mechanical valve needs to be replaced.
Tissue valves, which are made from animal tissue, typically last about 10-15 years and are not as durable as mechanical valves due to leaflet degeneration, calcification, endocarditis and so patients are more likely to undergo replacement surgery.
They also present with higher rates of infection but endocarditis may be treated with antibiotic therapy.
hey have a reduced risk of thromboembolism and a reduced need for anticoagulation and so there is a decreased bleeding risk.
- What are the indications for surgery in a patient who has been stabbed in the chest?
Indications can include:
- a diagnosis of cardiac tamponade that requires definitive management
- significant haemorrhage that is unlikely to stop without surgical intervention. This includes a chest tube drainage of a haemothorax of more than 1-1.5L initial loss or more than 200mL/ hour for more than 2 hours.
- persistent air leak in a pneumothorax
- tracheobronchial injury with a massive air leak present throughout respiration
- laceration to greater vessels
- cardiac injuries
- haemoperitoneum
