What complications are related to placing the patient in the lateral decubitus position?
Pulmonary resection is usually performed with the patient in the lateral decubitus position. The operative lung is placed in the nondependent location. Cardiopulmonary complications of the lateral decubitus position depend mostly on the patient’s preoperative condition.
The patient should be well anesthetized and paralyzed before turning them on their side, to prevent coughing, hypertension, and tachycardia. Blood pooling in the dependent portion of the body may lead to hypotension. Flexing the table exacerbates pooling and hypotension. The dependent lung is well perfused, and the nondependent lung is poorly perfused, which is due to gravitational effects on the distribution of pulmonary blood flow.
In an awake spontaneously breathing patient the depend-ent lung is better ventilated than the nondependent lung, which is due to more efficient contraction of the dependent hemidiaphragm. Greater curve (stretch) is present in the dependent diaphragm, which is due to abdominal contents pushing cephalad. In the anesthetized and paralyzed patient, most of the ventilation is distributed to the nondependent lung, while perfusion remains preferentially diverted to the dependent lung, creating a ventilation– perfusion mismatch. Reduction of lung volume that is due to induction of anes-thesia moves the nondependent lung to a more compliant portion of the pressure–volume curve. With paralysis of the diaphragm, the abdominal contents impede movement of the dependent lung to a greater extent than the nondepen-dent lung. Opening the chest further improves the compli-ance of the nondependent lung, thereby improving its ventilation. Downward pressure from the mediastinum, and pressure from lying on the lateral chest wall, exacerbate impaired dependent lung compliance and ventilation. Rolls beneath the hips and lower axilla lift the chest wall off the table and improve dependent lung ventilation.
Complications Associated with the Lateral Decubitus Position for Thoracic Surgery
· Coughing, tachycardia, and hypertension during turn into lateral decubitus position
· Hypotension from blood pooling in dependent portions
· V/Q mismatching leading to hypoxemia
· Interstitial pulmonary edema of the dependent lung (down-lung syndrome)
· Brachial plexus and peroneal nerve injuries
· Monocular blindness
· Outer ear ischemia
· Axillary artery compression
Maintaining the lateral decubitus position for a long time leads to transudation of fluid in the dependent lung, causing interstitial pulmonary edema. This is called down-lung syndrome. Administrations of large amounts of intra-venous fluid increase left atrial pressure and leads to further transudation of fluid.
Peripheral nerve injuries from pressure or stretching may also occur. Padding the lower extremities and placing a low axillary roll help prevent injury to the peroneal nerve and brachial plexus. The dependent eye should remain clear of head supports, and the dependent ear pinna should not be folded over. An arterial catheter in the dependent arm allows for constant monitoring for excessive pressure on the dependent axillary artery.