Thoracic videoassisted surgery (VATS) is usually performed under general anesthesia (GA), muscle relaxation, special airway management and one lung mechanical ventilation. Lately, some studies show, that at least some of VATS procedures can be performed equally safe without GA, rough double lumen tubes (DLT) and perserving spontaneous ventilation. Non-intubated techniques are considered as a step to quick recovery and early discharge after thoracic surgery. In the following explanation we are going to discuss the pathophysiology of open pneumothorax and spontaneous breathing that must be taken into account, options for early recovery and economic costs of non-intubated procedures.
Key words: Nonintubated VATS, rebreathing, mediastinal shift
Main pulmonary pathophysiologic changes that occur are decreased lung volumes due to compression of dependent lung with mediastinum and abdominal content. Lung function is decreased, hypoxemia and hypercapnia is expected due to rebreathing wasted air from operating lung, Shunt fraction is increased because of lung collapse. Unsecured airway and unpredictable sedation level can affect the breathing as well.
Despite these changes, hypoxemia and hypercapnea rarely pose a problem during NI-VATS. They are mostly well compensated by hypercapnia induced hyperventilation and supplemental oxygen administration. When hypoxemia or severe hypercapnia do occur, intermittent or continuous assisted face mask ventilation must be considered to alleviate the problem. Hyperventilation anyway, could interferes with surgical performance. Persistent severe hypoxemia or hypercapnia indispensable lead to sudden general anesthesia and airway security without changing the patient position.
Pathophysiologic changes affecting hemodynamics are due to mediastinal shift or oscillation during spontaneous respiration in the lateral decubitus position with an open thorax. During spontaneous breathing, open thorax leads to lung collapse and shifts the mediastinum toward dependent lung. During inspiration the negative pressure in the dependent lung pulls the mediastinum downwards, during expiration the mediastinum returns to its previous position. Hypercapnea due to hypoventilation and rebreathing from the collapsed lung increases cardiac output by sympathetic stimulation and by peripheral vasodilation.
Considering ongoing pathophysiological changes during spontaneous breathing and open thorax, patient’s safety and benefits should be the leading factor deciding about non intubated technique. Short acting anesthetics, monitoring depth of anesthesia and depth of muscle relaxation, possible complete reversal of muscle relaxation, videolaryngoscopes and disposable double lumen tubes with cuff control represent recent anesthesia management for VATS surgery. Post VATS early patients discharge depends more on preoperative lung dysfunction or other possible disabilities than on anesthesia itself.
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