Thoracic surgery
Introduction
In its broadest sense non-cardiac thoracic surgery covers the diagnosis and management of all non-cardiac disease within the chest. However, the practice varies between countries. For example, in the UK, unlike North America, most oesophageal disease is no longer managed by thoracic surgeons but by gastroenterologists and upper GI surgeons. This chapter will review the management of benign and malignant conditions of the chest and mediastinal disorders that are commonly managed by UK thoracic surgeons. The principles of oesophageal surgery are covered in Chapter 22 and chest trauma in Chapter 15.
Investigative techniques
Imaging: Chest X-ray, computerised tomography (CT), magnetic resonance imaging, ultrasound (US) and synchronized CT-positron emission tomography are the most commonly used modalities. Chest X-ray is useful as a ‘baseline’ and also for early post-procedure follow-up. CT provides the best anatomical information and is used for preoperative planning and for follow-up. low radiation-dose protocols protocols are being explored for lung cancer screening. Early evidence suggests that screening certain groups may lead to longer survival and this may become common practice. MRI is most useful to study soft tissues, and in particular in malignancy, to determine the extent of chest wall invasion, diaphragm invasion and for spread of cancers to the liver or brain.
Lung function tests: Lung function tests give a detailed portrait of the physiological effects of individual chest diseases and can track changes over time or as a result of treatment. When surgery is contemplated, lung function tests help assess the patient’s capacity to withstand chest wall incision or lung resection. They include:
• Measurement of air flow into and out of the alveoli, i.e. FEV1, FVC, peak air flow, total lung capacity, alveolar ventilation
• Measurement of gas diffusion across the alveolar–capillary interface, usually involving measuring rates of carbon monoxide diffusion
• Assessing the amount of dead space by calculating the residual volume and total lung capacity
• Assessing exercise capacity, e.g. by the 6 minute walk test or by formal cardiopulmonary exercise testing
Bronchoscopy: Flexible bronchoscopy can be performed with minimal or no sedation and topical local anaesthesia. It is possible to examine as far as segmental bronchi, obtain small biopsies and clear secretions.
Pleural aspiration and percutaneous biopsy: Aspiration of pleural effusions for cytological examination can be performed using a standard wide-bore needle and syringe. Blind pleural biopsy is now discouraged because of its relatively low yield rate and high complication rate. Many thoracic masses are amenable to percutaneous biopsy under US or CT guidance, although thoracoscopy or direct surgical cut-down to the lesion has the best yield.
Video-mediastinoscopy: A mediastinoscope is used to biopsy paratracheal and subcarinal lymph nodes. The instrument is a rigid tube incorporating fibreoptic light guides; it is inserted via a skin incision above the suprasternal notch and passed caudally along the plane of the pretracheal fascia (see Fig. 31.1a and b). The route passes close to the azygos vein, superior vena cava, innominate artery, arch of the aorta, pulmonary artery and the recurrent laryngeal nerves posterolaterally on each side. These structures and the oesophagus are at risk of damage and, although rare, this must be explained to the patient. Mediastinoscopy gives access to the mediastinum except for the subaortic fossa (below the aortic arch and often containing lymph nodes). Access to this area is obtained by anterior mediastinotomy or video-assisted thoracic surgery.
Thoracoscopy: This is the thoracic equivalent of laparoscopy and is sometimes known as video-assisted thoracoscopic surgery or VATS. It is usually performed under general anaesthesia but basic procedures use local anaesthesia with sedation. Instruments for viewing and operating are inserted through small incisions in the chest wall.
Anterior mediastinotomy: Anterior mediastinotomy (see Fig. 31.1c), a form of mini-thoracotomy, may be used to obtain biopsies from anterior mediastinal lesions, e.g. thymic tumours. The approach can be left or right of the sternum, either intercostally or with costal cartilage resection. Left anterior mediastinotomy affords good access for biopsy of subaortic fossa masses. Increasingly, VATS is the preferred method of accessing these sites.
Therapeutic procedures
Principles of tracheostomy: A tracheostomy (see Figs 31.2, 31.3) is an artificial opening into the trachea to provide a secure airway when the pharyngeal airway or larynx needs to be bypassed. With time, an epithelialised fistula develops between the skin and trachea which allows tracheostomy tubes to be changed and the airways cleaned with ease. In many units ‘percutaneous tracheostomy’ is performed using a ‘Seldinger-type’ technique. However, the technique of ‘open’ tracheostomy should be understood by most surgeons.
Fig. 31.3 Tracheostomy
(a) Disposable tracheostomy tube. Note the distal balloon which is inflated via the small tube to provide a snug fit inside the trachea.
(b) Patient being ventilated via an elective tracheostomy after cardiac surgery
Indications for tracheostomy include:
• Permanent functional obstruction of the upper airway, e.g. carcinoma of larynx
• Temporary or potential upper airway obstruction, e.g. facial fractures, major head and neck operations or injuries
• Long-term ventilatory support, where prolonged endotracheal intubation would otherwise be likely to cause permanent laryngeal damage and prevent swallowing and speech. Tracheostomy also provides continuous access to the lower airways for bronchial aspiration and toilet
Tracheostomy should be a planned procedure performed in the operating room under general anaesthesia. It is not an emergency procedure for patients with upper airway obstruction. For these, endotracheal intubation or cricothyroidotomy (see Fig. 31.4) should be used.
Fig. 31.4 Cricothyroidotomy
(a) In a dire emergency, this life-saving procedure can be rapidly employed to gain time. (b) Modern mini-cricothyroidotomy can be performed percutaneously by making a small incision through the cricothyroid membrane and progressively dilating it with graduated dilators before insertion of a specially constructed small-diameter tube, e.g. Minitrach or Quicktrach. These are used in accident victims and often in intensive care units
Complications of tracheostomy:
• Haemorrhage caused by erosion of the innominate (brachiocephalic) artery or vein
• Tracheo-oesophageal fistula, particularly where a nasogastric tube is in place
• Displacement of the tracheostomy tube may occur before the desired ‘fistula’ becomes established, making it difficult to reintubate the trachea
• Tracheal stenosis, usually the result of prolonged use of a high-pressure cuff (now rare due to the introduction of low-pressure cuffs)
Thoracotomy
All thoracotomies are now devised to spare at least some muscles from being divided.
Posterolateral thoracotomy: Posterolateral thoracotomy is the standard approach for lung and oesophageal resections as well as for surgery of the descending aorta. Generally a curved incision passes below the inferior angle of the scapula, latissimus dorsi is divided and the chest is entered through the bed of the (unresected) fifth or sixth rib. If necessary, the incision can be extended into the abdomen (thoraco-abdominal incision), e.g. for oesophago-gastrectomy or thoraco-abdominal aortic aneurysm.
Lateral thoracotomy: Lateral thoracotomy involves an incision extending between anterior and posterior axillary lines.
Median sternotomy: Median sternotomy or ‘sternal split’ gives wide access to the heart and the entire anterior mediastinum including the great vessels. It is the standard incision for cardiac surgery as well as for excision of thymic lesions and large retrosternal parathyroid tumours and, occasionally, resection of a goitre with massive retrosternal extension.
