Introduction:
Surgical procedures under general anesthesia are full of complications. Severe allergic reactions, cardiac problems, and neurological complications are often associated with major surgical procedures. The collapse of the lung structures or atelectasis is a major lung complication associated with surgery.
What Is Atelectasis?
The partial or complete reversible collapse of the alveoli is known as atelectasis. This causes improper gaseous exchange. The gaseous exchange in the lung takes place through a change in the pressure gradient. Any change in that lead to shifts in the pressure gradient and collapse of the lung structures. The causative factors are:
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Excessive pressure and compression of the lung tissues.
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Absorption of the air in alveoli.
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Improper secretion of the surfactant is responsible for the inappropriate expansion of the lung structures.
The symptoms are:
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Difficulty in breathing.
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Rapid and shallow breathing.
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Chest pain.
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Change in the color of the lips and fingers due to less oxygenation.
What Are the Risk Factors?
Post-surgical atelectasis can be caused by several factors. These are:
Obesity:
Obesity is considered one of the most common risk facts for the development of post-operative atelectasis. Fat accumulation in the abdomen and chest exerted a huge amount of force. This causes displacement of the diaphragm. This alters the intra-thoracic pressure, and pleural pressure is increased. As a result, the extensibility of the lungs and the volume of air remains after the exhalation is reduced. Also, a decrease in transpulmonary pressure is observed in patients with higher body mass indexes.
Age:
The risk of development of atelectasis is increased with increasing age. Patients aged around 50 years tend to develop atelectasis after surgery. Alteration in the pulmonary blood flow and ventilation of the lung is associated with this. Also, it is noted in children below the age of three years. Inadequate development of the chest muscles and supporting structures and immaturity of the lung tissues are responsible for these conditions.
Diaphragmatic Dysfunction:
Diaphragmatic dysfunction is often observed in the case of upper abdominal and thoracic surgery. This is also associated with increased thickness of the diaphragm. These factors are crucial in the development of post-surgical atelectasis.
Intra-abdominal Hypertension:
Abdominal pressure is increased in several conditions. Hematoma (accumulation of blood in the tissues), ascites (collection of fluid in the abdomen), ileus (obstruction of the bowel due to non-mechanical causes), and tumors are associated with increased abdominal pressure. This is responsible for the loss of diaphragmatic tone, increased pleural pressure, and decreased transpulmonary pressure.
Pulmonary Conditions:
Several lung conditions like chronic obstructive pulmonary disorder, pulmonary hypertension, pulmonary edema, and lung fibrosis are associated with the development of post-operative atelectasis. In chronic obstructive pulmonary disorder and lung fibrosis, loss of the permanent recoil of the lung is seen. Also, these conditions are associated with lower ventilation and perfusion ratio (ratio between ventilation of the lung and pulmonary blood flow) is seen. On the other hand, lung infection, pulmonary edema, and pulmonary hypertension are associated with increased lung weight. Also, alterations in the surfactants are associated with the collapse of the lung structures.
Habits:
Oral habits like smoking and the effects of other environmental factors like heavy metals and toxic gases have deleterious effects on lung health. These substances are responsible for the fibrous degeneration of lung tissues. This causes a loss of elasticity in the lung. Also, the amount of surfactant secreted by the lung is reduced in such cases. This increases the chance of the collapse of the lung structures. Also, increased secretion of the airway tract causes obstructing during and after the surgery.
Anesthesia Techniques:
Anesthesia techniques such as inhalation anesthesia or intravenous anesthesia are associated with a greater risk of post-operative atelectasis. In contrast, the chances of developing atelectasis are less with the use of regional anesthesia. Nitrous oxide is lipid soluble. This high lipid solubility is responsible for alveolar gas absorption. Opioids used during anesthesia are responsible for respiratory depression and cough inhibition. Neuro muscular during anesthesia is also responsible for post-operative atelectasis. Neuromuscular blockage may cause compression of the abdomen and thoracic wall. In post-operative cases, this is this may cause respiratory muscle dysfunction and reduced oxygen supply.
Nature of Surgical Procedure:
Surgical procedures like cardiac surgery, such as bypass surgery, are associated with an increased risk of atelectasis. One-lung ventilation during a surgical procedure or minimally invasive abdominal surgical techniques is responsible for post-surgical atelectasis. The increased duration during surgery also increases incidences of lung collapse. Also, a huge amount of blood transfusions during surgery or the use of pneumoperitoneum (use of gas in abdominal surgery) during surgery is associated with the incidence of atelectasis.
What Are the Diagnostic Methods?
The diagnostic procedures are:
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Chest X-ray: In chest radiographs, platelike, horizontal lines can be seen in the affected areas.
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Computed Tomography (CT): Chest CT can also be used to visualize a detailed picture of the lesion. Displacement of the thoracic structures towards the collapsed area can also be seen.
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Magnetic Resonance Imaging (MRI): It can be useful in detecting the cause of atelectasis. The nature of obstruction in the airway passage can be evaluated through it.
What Are the Preventive Measures?
Different techniques can be used to prevent the incidence of post-operative atelectasis. These are:
Preoperative Procedure:
Preoperative procedures are most effective in the reduction of post-operative atelectasis. Cessation of smoking, preoperative physiotherapy, and breathing exercises can be useful in preventing such conditions. Intensive inspiratory muscle training exercises help prevent such conditions in bypass surgery or in abdominal surgical procedures.
Post-operative Analgesia:
The administration of post-operative analgesia can be helpful in the reduction of neuroendocrine stress. Epidural analgesia (anesthesia delivered via catheter) and patient-controlled analgesia are effective enough to reduce post-operative complications.
Perioperative Techniques:
Atraumatic intubation, aspiration of the bronchial secretion, and reinflation of the lung before chest closure can be useful in the prevention of such conditions. Positive end‑expiratory pressure (PEEP) can be used to dring operative procedures or after operation to increase the alveolar pressure sequentially. After the operation, adequate oxygenation in a humid atmosphere is helpful in preventing the drying of the alveoli.
Post-operative Methods:
The incentive spirometer is a simple exercise that can be useful to increase lung function and establish proper ventilation. Continuous positive airway pressure can be utilized to inflate the lungs and prevent the collapse of the alveoli.
Conclusion:
Atelectasis is a serious post-operative complication. Pre-surgical assessment of the patient can be helpful in identifying the risk factors. Also, surgical techniques and types of anesthesia are associated with such conditions. Post-operative analgesia and breathing exercises are useful in preventing such conditions.
