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//SURGICAL ACCESS TO THORACIC VISCERA

SURGICAL ACCESS TO THORACIC VISCERA

Thoracocentesis (pleural aspiration)

Thoracocentesis or pleural aspiration is an essential step in the assessment of pleural effusions. A chest radiograph will confirm the location and extent of the effusion and clinical examination will identify the best position for aspiration: the posterior midscapular line is a common site. The skin of the desired interspace is cleaned and anaesthetized, and the aspiration needle is inserted at the lower margin of the interspace. The needle is not inserted in the middle of the interspace because the intercostal vessels run along the middle of the interspace posteriorly, and from the axilla forwards onto the anterior chest wall they are protected only by the lower border of the rib. After appropriate local analgesia has been applied, the needle is carefully advanced in a perpendicular direction in the lower portion of the interspace until it enters the pleural space. More complex or small effusions should be aspirated under ultrasound guidance.

Needle thoracocentesis

Needle thoracocentesis is performed in patients in whom a life-threatening tension pneumothorax is suspected. A needle is inserted into the second intercostal space in the midclavicular line on the side of the tension pneumothorax, with the patient in an upright position. A sudden escape of air is heard when the needle enters the parietal pleura. A chest tube must be inserted after this procedure.

Chest drain insertion

The insertion site for a chest drain is usually the fifth intercostal space, just anterior to the midaxillary line on the affected side. A 2 cm horizontal incision is followed by blunt dissection through the subcutaneous tissues to the top of the rib. The parietal pleura is punctured with the tip of a clamp and a gloved finger inserted into the pleural space to free up any adhesions. The chest drain (thoracostomy tube) is then inserted into the pleural space and attached to an underwater sealed container placed below the level of the lungs: the water level rises and falls in the tube with ventilation.

Pericardiocentesis

Pericardiocentesis is performed to aspirate a pericardial effusion or, in an emergency, to decompress a cardiac tamponade, where pressure from blood in the pericardial space prevents the heart chambers from filling during the cardiac cycle, and seriously impairs cardiac output.

Pericardial puncture can be performed in either the fifth or sixth left intercostal space near the sternum (to avoid the internal thoracic artery), or at the left costoxiphoid angle. The needle is passed 1–2 cm to the left of the costoxiphoid angle at 45° to the skin, and then up and backwards towards the tip of the scapula until it enters the pericardial sac.

Placement of electrocardiograph leads

The 12-lead electrocardiograph (ECG) provides three-dimensional information on the electrical activity of the heart. The limb leads provide information about the electrical activity in the frontal plane. They are placed on the left and right wrists, and the left foot, with the right foot acting as a neutral grounding point. The chest leads provide information about the electrical activity in the horizontal plane. They are placed as follows: V1, right fourth intercostal space, parasternal position; V2, left fourth intercostal space, parasternal position; V3, midpoint of V2 and V4 on the left; V4, fifth intercostal space, midclavicular line on the left; V5, fifth intercostal space, anterior axillary line on the left; V6, fifth intercostal space, midaxillary line on the left.

Thoracotomy incisions

Thoracotomy incisions may be posterolateral, anterolateral or involve a transverse thoracosternotomy.

Posterolateral

A posterolateral incision is most commonly used in thoracic surgery for unilateral pulmonary resections, bullectomy, unilateral lung volume reduction surgery, chest wall resection and oesophageal surgery (Fry 2000). The patient is placed in a lateral decubitus position with adequate support of the elbow, axilla and knee with padding. The standard approach is via an incision from the anterior axillary line which curves about 4 cm below the tip of the scapula and then vertically between the posterior midline and medial edge of the scapula. The incision is usually extended to the level of the spine of scapula. Overall, the incision forms an S-shape in the fifth intercostal space. The sixth or seventh intercostal space is used in oesophageal surgery.

The lower portions of trapezius and latissimus dorsi are divided. Serratus anterior is retracted, and may be divided in a high thoracotomy. The costal muscle and pleura are dissected along the inferior margin of the intercostal space to avoid damaging the neurovascular bundle. A small section of rib is removed at the costovertebral angle to reduce the risk of fracture, particularly in patients older than 40 years. This technique provides good access to the thoracic contents; the main problem is postoperative pain as a consequence of intraoperative musculoskeletal traction.

Anterolateral

Using an anterolateral approach, the patient is placed in the supine position with their arms by their sides. A roll is placed vertically under the back and hips so as to raise the operative side by approximately 45°. The incision is from the midaxillary line over the fifth intercostal space along the inframammary fold, and curves upwards parasternally. The pectoral muscles are divided, and subsequent access to the thorax is similar to that used in the posterolateral approach. However, access is limited, and may be improved by dividing costal cartilages.

‘Clam shell’

The transverse thoracosternotomy is known as the ‘clam shell’ incision. It provides excellent exposure to both sides of the chest and is therefore used in bilateral lung transplantation and in lung volume reduction surgery with bilateral lung resections. The patient is placed in the supine position with a roll vertically along the upper thoracic spine. Bilateral anterolateral incisions are made in the inframammary fold, and the sternum is transected. This allows the upper portion of the thorax to be displaced upwards with a rib-spreader, hence the name clam shell. The main disadvantage of the clam shell procedure is the need to transect the sternum: even after careful repair with sternal wires, there is a risk of sternal instability.

Sternotomy

Sternotomy is commonly needed in cardiac surgery. The patient is placed in the supine position with both arms extended by the side. A vertical incision is made in the midline from the suprasternal notch to a point just below the xiphoid process. The tissues around the manubrium and the xiphoid process are mobilized. The pectoral fascia in the midline is incised and the sternum is split and its two edges retracted. The sternum is closed using interosseous wire sutures.

Axillary thoracotomy

The patient is placed in the lateral decubitus position, with arms abducted at 90° and supported on an arm rest. The incision is based along the desired intercostal space, which, for upper thoracic lesions, is the second or third space. Latissimus dorsi is elevated and retracted, whereas serratus anterior is divided in the direction of its fibres. The anterior aspect of serratus anterior is divided to expose the intercostal muscles, which are divided in turn. The overall size of the incision is limited and it provides good access to the upper thorax. Postoperative pain is less than with some other approaches, but the long thoracic nerve (nerve of Bell) may be damaged if serratus anterior is divided too posteriorly.

Thoracoscopic access

Occasionally, video-assisted thoracoscopic surgery is required to assess the mediastinum. The thoracoscope is usually introduced via the fifth intercostal space in the midclavicular line, with additional ports at the third and sixth intercostal spaces to assess the anterior mediastinum. To assess the posterior mediastinum, the thoracoscope is inserted into the seventh intercostal space in the midclavicular line.

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