Anesthetic Consideration for Thoracic Surgery - An Insight

Introduction

The term "thoracic surgery" describes the surgical operations carried out inside the thoracic cavity, which includes the heart, lungs, and other nearby tissues. Anesthesiologists play a crucial role in maintaining patient safety and maximizing comfort during thoracic surgery. Due to the unique anatomy and physiological changes connected to the thoracic cavity, there are special anesthetic concerns for thoracic surgery. Careful planning and individualized management for each patient is required due to the closeness of essential organs, including the heart and lungs, as well as the possible influence on respiratory mechanics. Maintaining appropriate oxygenation, ventilation, and hemodynamic stability while lowering the risk of complications are the key objectives of anesthesia during thoracic surgery.

What Is Thoracic Surgery?

Thoracic surgery is any procedure performed on the chest (thorax). The most commonly recognized organ in the chest is probably the heart, but thoracic surgery also involves lung surgery and other procedures. The other organs involved in the surgery are:

• Trachea (windpipe).

• Esophagus (food pipe).

• Chest wall (breast bone, ribs, and their surrounding muscles).

• Mediastinum (space between the lungs).

• Diaphragm (respiratory muscle located below the lungs).

Thoracic surgery can be executed either through open surgery or with minimally invasive techniques. To reach the operative region during open surgery, a wider incision is created in the chest. During minimally invasive surgery, a video camera and specialized surgical tools are put into the chest cavity through tiny incisions. By providing a visual of the surgical site, the camera enables the surgeon to carry out the treatment precisely and accurately. In comparison to open surgery, this precise method often results in less postoperative discomfort, shorter hospital stays, and quicker recovery durations. It also minimizes the stress on surrounding tissues.

What Are the Various Effects of General Anesthesia on Pulmonary Function?

• Respiratory Depression - Reduced airflow and muscular tone brought on by general anesthesia might result in decreased breathing rate and depth. As a result, breathing may become shallow, lungs may not expand as much, and oxygen exchange may be compromised.

• Atelectasis - Atelectasis which is the collapse or partial collapse of lung tissue, can happen as a result of general anesthesia. Reduced lung capacities, a weakened cough reflex, and poor mucociliary clearance under anesthesia can all contribute to atelectasis. It could lead to less ventilation and oxygenation mismatch.

• Functional Residual Capacity (FRC) - The amount of air that remains in the lungs following a typical exhalation known as the FRC can be decreased by general anesthesia. This drop in FRC has the potential to impair lung compliance and raise the risk of airway closure.

• Increased Airway Resistance - An increase in airway resistance brought on by general anesthesia might make breathing more difficult. Patients who already have respiratory problems like asthma or chronic obstructive pulmonary disease (COPD) will experience this impact more strongly.

• Impaired Clearance - The respiratory tract's cilia, which are in charge of removing mucus and debris, might move more slowly or less effectively when under general anesthesia. This may cause secretions to build up in the airways and raise the possibility of postoperative respiratory problems, including pneumonia.

How Does General Anesthesia Affect Pulmonary Function in Patients With Pre-existing Lung Disease?

1) Obstructive Lung Disease:

• This group of diseases includes emphysema (shortness of breath due to lung disease that causes damage to alveoli), bronchitis (inflammation of the bronchial tubes accompanying mucus production), and asthma (excess mucus production resulting in constriction of airways making breathing difficult). In such patients, bronchospasm may be triggered by airway instrumentation, such as during laryngoscopy, bronchoscopy, and intubation. Local anesthetics and vapors may reduce this reaction.

• Although anesthetic vapors are effective bronchodilators, they will hinder the HPV (hypoxic pulmonary vasoconstriction) response.

• When administered to individuals who have bullae (air-filled spaces), nitrous oxide should be avoided since it causes the bullae to inflate or rupture, which can lead to a pneumothorax or tension pneumothorax.

2) Restrictive Lung Disease (RLD):

• It includes interstitial lung disease.

• Similar safety precautions as those for obstructive lung disease patients are followed in the case of RLD patients.

• Patients who already have pulmonary hypertension and cor pulmonale are more likely to develop biventricular cardiac failure as a result of the cardiac depressive effects of anesthetic vapors.

• Patients with anterior mediastinal mass (cancer that begins in the thymus gland) require special attention. In such individuals, complete airway or vascular blockage can occur as a result of loss of muscular tone brought on by anesthesia paralysis.

What Are the Different Types of Anesthesia Equipment Used During Thoracic Surgery?

• Endotracheal Tubes That Provide One-Lung Ventilation - One-lung ventilation involves limiting ventilation to one lung or ventilating one lung while allowing the other to collapse to enable surgical exposure in the thoracic cavity. Lung separation is provided using a double-lumen tube (DLT). DLTs enable suctioning of the non-ventilated lung during surgery and offer effective lung separation.

• Double Lumen Tube Size - The precise science of choosing the right DLT size is not known. DLT is selected for the site opposite the surgical site. Tube size is crucial for the manner of ventilation through the bronchial lumen as a large tube may be challenging to insert and injure the airway. Small tubes can cause leakage.

• Fiberoptic Bronchoscope - To see the vocal cords, the bronchoscope is inserted beneath the epiglottis and down the midline of the tongue.

• Ventilators - Variations in patient disease populations necessitate flexible ventilatory modes (volume cycled; pressure pre-set modes) for ventilation optimization.

• Difficult Airway Passage - When a challenging airway is identified in the operating theater, extubation at the end of the surgery should be done with even greater caution. Removing an endotracheal tube (ETT) is known as extubation, and it is the final step in releasing a patient from a mechanical ventilator.

• Invasive Monitors - Typically, arterial lines are set up in patients. Any patient with postoperative hypotension who is insensitive to fluid boluses (single and large doses of medicine), as well as those with pulmonary hypertension or cor pulmonale (a condition that results in the failure of the right side of the heart. Cor pulmonale may result from persistently high blood pressure in the right ventricle of the heart and the arteries that supply the lung) has to have a pulmonary artery catheter.

Conclusion

In general, anesthetic concerns for thoracic surgery include customizing the anesthesia plan to the patient's needs, maximizing oxygenation and ventilation, successfully controlling pain, preserving hemodynamic stability, and keeping an eye out for any complications. The best outcome for patients having thoracic surgery depends on a thorough approach and strong cooperation between the anesthesia team, surgeon, and other medical specialists.