The lungs are the only organ in the body that receives all the cardiac output, and are also the giant filter through which venous blood must pass throughout the body; they are also an open organ, with alveoli connected to the outside world through all levels of bronchi and trachea. This makes the lungs vulnerable to damage by endogenous and exogenous harmful factors. Preoperative risk factors, surgery, anesthesia, blood transfusion, cardiopulmonary transfer, and other medical measures can cause certain damage to the lungs during the perioperative period, resulting in various perioperative pulmonary comorbidities and, in severe cases, respiratory insufficiency, threatening the life of the patient. Therefore, perioperative lung protection measures, prevention and treatment of perioperative pulmonary complications are very important, and are a powerful guarantee for rapid recovery of surgical patients.
”Rapid rehabilitation surgery” refers to the application of various proven methods to reduce surgical stress and complications before, during and after surgery, and to accelerate the patient’s recovery after surgery, as a synergistic result of a series of effective measures. Rapid rehabilitation surgery must be a multidisciplinary collaborative process that includes not only surgeons, anesthesiologists, rehabilitation therapists, nurses, but also the active participation of patients and their families. More importantly, rapid recovery surgery relies on the integration and good integration of important perioperative therapies. In the case of thoracic surgery, perioperative lung protection is the key to reducing postoperative pulmonary complications.
Common perioperative pulmonary complications and their associated risk factors
I. Common perioperative pulmonary complications
Postoperative pulmonary complications are an important component of the risk of thoracic surgery. In the perioperative period, common pulmonary complications in patients include pulmonary atelectasis, pulmonary edema, pneumonia, bronchitis, bronchospasm, respiratory failure or even ARDS, and exacerbation of underlying chronic lung disease. Postoperative pneumonia is usually nosocomial acquired pneumonia, which has a maximum morbidity and mortality rate of 10% to 30%, and postoperative pulmonary complications result in an average prolonged hospital stay of 1 to 2 weeks. The incidence of perioperative bronchospasm is increased in the presence of concomitant respiratory disease such as chronic obstructive pulmonary disease (COPD). The incidence of intraoperative bronchospasm in patients with a history of asthma is about 10%. The incidence of bronchospasm in patients undergoing thoracic surgery is higher than that of other surgeries.
Risk factors for perioperative pulmonary complications
The main risk factors for pulmonary complications in perioperative patients include factors related to the patient’s underlying condition and surgery-related risk factors.
(A) Risk factors related to the patient’s basic condition
1, smoking: smoking can lead to respiratory cilia oscillation dysfunction and increased secretions. Trials have confirmed that the relative risk of pulmonary complications in smokers is 1.4 to 4.3 times greater than in nonsmokers. Even in patients without chronic lung disease, smoking can increase the risk of pulmonary complications. Quitting smoking for more than 1 week before surgery can reduce the incidence of postoperative complications.
The higher the ASA classification, the greater the risk of postoperative pulmonary complications. Those with preoperative malnutrition and increased pulmonary water due to low plasma protein have a significantly higher chance of developing pulmonary complications.
3. Underlying lung disease: COPD is not an absolute contraindication to any thoracic surgery, but studies have confirmed that patients with COPD have an elevated risk of postoperative pulmonary complications. Pulmonary function tests are the gold standard for COPD diagnosis. For patients with COPD whose symptoms and airflow limitation and exercise tolerance have not been effectively improved, aggressive treatment should be given preoperatively; for patients with elective surgery, if acute exacerbation of COPD occurs, surgery should be postponed.
Some studies have shown that the overall incidence of postoperative complications is higher in patients with asthma than in patients without asthma.
4.Age: As age increases, the lung parenchyma changes, fibrous connective tissue increases, lung elasticity decreases, alveoli collapse, resulting in decreased lung compliance and increased respiratory resistance resulting in decreased pulmonary ventilation and ventilation function.
5, obesity: obese patients in the supine position when the lung compliance is significantly reduced, ventilation / blood flow ratio is out of balance; at the same time, obese patients due to the thoracic vertebrae posterior convexity, lumbar vertebrae anterior convexity, too much fat in the abdomen, diaphragm elevation leads to thorax and its mobility reduced, so there is often hypoxemia and hypercarbia, typical cases can be seen in patients with sleep apnea syndrome.
6, long-term bed rest: long-term bed rest can lead to atrophy of the mucosa and glands of the upper respiratory tract, weakening the warming and humidification of the inhaled gas, which can damage the defense function of the lower respiratory tract; atrophy of the lymph glands of the pharynx, the airway immune function is reduced, so that the self-barrier function of the respiratory tract is reduced; respiratory muscle strength is reduced, making the cough weak, small airway narrow and easy to collapse, resulting in the retention of secretions; degeneration of the mucosa of the pharynx. The mucous membrane of the pharynx degenerates, the sensation is dulled, and the swallowing reflex decreases with age, making it easy for bacteria in the throat to be inhaled or choked into the lower respiratory tract causing pneumonia. Long-term bed rest can also lead to the two lungs after the base of the drop edema and drop pneumonia.
7, diabetes: research has shown that lung tissue is also a target organ of diabetes damage. The older the patient with type 2 diabetes, the longer the disease duration, and the more microvascular complications, the greater the likelihood that pulmonary diffusion will be impaired. In addition, diabetes affects the local defense function of the lungs. The airway defense reflexes and mucociliary clearance are reduced in patients with diabetes mellitus combined with autonomic neuropathy. Diabetes mellitus is an independent risk factor for lower respiratory tract infections and the severity of these infections.
(ii) Surgical-related risk factors
1. Surgical site: Chest and upper abdominal surgery are the most important surgery-related risk factors. Studies have shown that the degree of influence of surgical site on pulmonary infection is in the following order: cranial > thoracic > upper abdomen > lower abdomen > other.
2, anesthesia: the type of anesthesia, drug selection, and operation method are all surgery-related risk factors. General anesthesia tracheal intubation can destroy the respiratory barrier and even induce bronchospasm; diaphragm elevation and reduced functional residual air volume (FRC) can lead to pulmonary atelectasis; mechanical positive pressure ventilation can lead to the disappearance of negative pressure in the thoracic cavity, increased physiological nullification and shunt, improper mechanical ventilation can lead to pulmonary air pressure injury, mostly seen in large tidal volume, high airway pressure mechanical ventilation; prolonged inhalation of high oxygen concentration can lead to pulmonary expansion insufficiency; Inhaled anesthetics can attenuate the pulmonary hypoxic pulmonary vasoconstrictor response, alter the ventilation/blood flow ratio, and reduce alveolar surface active substances, which can seriously affect patients’ intraoperative lung function and increase the incidence of postoperative pulmonary comorbidities; opioid analgesics in anesthetic drugs (such as fentanyl, pethidine hydrochloride, morphine hydrochloride, etc.) have an inhibitory effect on the respiratory center, especially in pediatric surgical patients; residual effects of muscle relaxants Can lead to reduced ventilation, affecting respiratory function; intravenous anesthetics have a certain inhibitory effect on the circulation and respiratory system.
3, surgical operation: after the opening of the chest, the side of the chest cavity is open, the lung pulling expansion due to negative intrathoracic pressure disappears, resulting in alveolar atrophy, alveolar ventilation area is sharply reduced (even reduced by about 50%), while the pulmonary circulation resistance increases. Intraoperative damage to the chest wall, bronchi and lung tissue results in weakened respiratory motion; excessive squeezing or pulling of lung tissue damages healthy lung tissue. Open thoracotomy can limit the respiratory motion amplitude due to chest wall softening, phrenic nerve injury, pleural effusion and gas accumulation, pain, and tight dressing wrapping, which affects the patient’s ventilatory function and induces bronchospasm.
4.Operation time: The lungs may be squeezed and twisted for a long time during the operation, and there are different degrees of pulmonary edema in the lung tissue on the open side, which affects the gas exchange in the alveoli. The risk of pulmonary complications is higher when the operation lasts >3h.
5. Fluid balance: During thoracic surgery, the overall blood loss may be small, but the risk of large blood loss potentially occurs in a short period of time; the surgical operation may compress or pull the heart and large blood vessels in the thoracic cavity, which interferes with the circulation. In addition, improper control of intraoperative rehydration amount and rehydration speed leads to: excessive fluid intake, increased pulmonary water or even pulmonary edema, resulting in diffusion disorders and hypoxia; too little fluid output, dry airway, difficult sputum excretion by airway cilia, sputum obstruction or even pulmonary atelectasis.
6, analgesia: (1) imperfect analgesia: pain affects patients’ sleep and rest, leading to fatigue and decreased physical strength; at the same time, it makes patients afraid to breathe deeply and cough hard, which is not conducive to the discharge of respiratory secretions and can lead to pulmonary insufficiency and pneumonia. (2) Excessive analgesia: Patients are drowsy, have reduced respiratory sensitivity, have a weakened cough reflex, and are prone to aspiration when vomiting occurs.
Strategies and measures for perioperative pulmonary protection
The purpose of perioperative pulmonary protection is to maintain lung function and prevent pulmonary complications, so that patients can safely pass through the perioperative period and safeguard the surgical outcome. Therefore, perioperative pulmonary protection measures should begin preoperatively and continue throughout the intraoperative and postoperative periods.
I. Preoperative evaluation
(A) Careful medical history questioning
The preoperative history should be reviewed in detail to understand the diagnosis and treatment of the disease. In particular, the following points should be noted.
1. whether the cough is chronic, the nature of the cough and the diurnal changes.
2. Understand the coughing sputum, including the volume, color and viscosity of sputum, whether it is easy to cough up, and whether changing the position helps to excrete sputum; whether there is blood in the sputum, and if there is hemoptysis, understand the amount of hemoptysis. Learn whether there is a history of frequent coughing up yellow pus sputum with foul smell.
3. The nature of dyspnea (inspiratory, expiratory, mixed), and whether dyspnea occurs at rest. If there is, it suggests poor cardiopulmonary compensation and poor tolerance of anesthesia and surgery.
4.Smoking history: For smokers, the daily smoking amount, years of smoking, and the time to stop smoking before surgery should be known.
5.Disease triggering and remitting factors: such as whether the asthma patient has specific allergens.
6. Treatment history: antibiotics, bronchodilators, and glucocorticoid application, including the specific dosage usage, and the patient’s reaction to the drugs.
(B) Detailed physical examination
1, body shape and appearance: obese, scoliosis patients are prone to pulmonary atelectasis and hypoxemia due to reduced lung volume (FRC, total lung volume) and decreased lung compliance; malnourished, hyperemic patients have weak respiratory muscle strength, decreased immunity, and are prone to co-infection. Observe whether there is cyanosis in the mouth, lips and nail bed. COPD patients may have barrel-shaped chest; if there is chest wall asymmetry, there may be pneumothorax, pleural effusion or solid lung changes.
2, respiratory condition: respiratory rate > 25 times / min is the early manifestation of respiratory failure; expiratory effort suggests airway obstruction; with the diaphragm and intercostal muscle load increases, the role of auxiliary respiratory muscles is enhanced; the presence of paradoxical breathing suggests diaphragm paralysis or severe dysfunction.
3, chest auscultation: The importance of chest auscultation should be especially emphasized. Patients with obstructive lung disease have prolonged expiratory phase and low breath sounds.
4.Pulmonary percussion: the percussion of emphysema is over clear sound; the percussion of solid lung changes is turbid sound.
5.Other: In patients with combined pulmonary hypertension, pulmonary heart disease, and right heart insufficiency, there may be jugular venous anger, hepatocervical reflux sign (+), and splitting of heart sounds may be heard on cardiac auscultation.
(C) Preoperative pulmonary function assessment
Pulmonary function tests help to understand the nature and severity of lung disease and whether the lesions are reversible, predict the efficacy of surgery and the occurrence of postoperative pulmonary complications, and help in the selection of the type and extent of chest surgery. Pulmonary function tests need to be routinely performed in patients undergoing open-heart surgery and in non-open-heart surgery patients aged >60 years with lung disease and a history of smoking.
(D) Laboratory tests and auxiliary examinations
1, routine blood tests: in addition to the general significance, hemoglobin > 160 g/L and hematocrit > 60%, if there are no special circumstances (such as true erythrocytosis, etc.), often suggest chronic hypoxia.
2, blood urea nitrogen: blood urea nitrogen >7.5 mmol/L can be used as a risk factor to predict postoperative pulmonary complications.
3, serum serum protein: Studies have shown that low levels of serum serum protein (30-39 g/L) are an important predictor of postoperative pulmonary complications, and serum serum protein <35 g/L is the most effective and patient-relevant predictor of postoperative pulmonary complications.
4. Chest X-ray: Preoperative frontal and lateral chest X-ray should be routinely performed. The presence of tracheal deviation, barrel chest or stenosis, airway obstruction, etc. is an important guide for the choice of anesthesia.
5.Electrocardiogram: Those with obvious pulmonary dysfunction may have electrocardiogram changes, such as right deviation of electrical axis, pulmonary P wave, right ventricular hypertrophy and right bundle branch conduction block, which may suggest pulmonary hypertension and pulmonary heart disease. Those with myocardial ischemia and cardiac enlargement can be estimated to have poor tolerance to anesthetic drugs.
6, blood gas analysis: blood gas analysis is a valuable index to evaluate pulmonary function, which can reflect the ventilation, acid-base balance, oxygenation status and hemoglobin content of the body, thus reflecting the severity of the patient’s lungs and disease and the urgency of the disease process. A blood gas analysis is necessary in the presence of severe lung disease, and a PaCO2 > 45 mmHg (1 mmHg = 0.133 kPa) is associated with a significant increase in postoperative pulmonary complications.
II. Preoperative preparation
(A) Routine preparation
1. Quit smoking or smoking ban: For long-term smokers, they should quit smoking as much as possible before surgery, and the earlier the better. It is very difficult to quit smoking clinically, but it is best to quit smoking 1-2 weeks before surgery in order to reduce airway secretions and improve ventilation.
2. Respiratory exercise: Instruct patients to perform respiratory exercise. When chest breathing is no longer effective in increasing pulmonary ventilation, deep and slow abdominal breathing should be practiced. Respiratory exercise, autonomous deep breathing, coughing and other means can help discharge secretions and increase lung capacity, and reduce the incidence of postoperative pulmonary complications.
3.Nutritional support: improve the general nutritional status, and actively correct severe anemia and water-electrolyte imbalance caused by long-term malnutrition and protein depletion.
4.Other: In cases of combined hypertension, coronary atherosclerotic heart disease, diabetes mellitus, arrhythmia, conduction block, liver and kidney insufficiency, we should consult the corresponding departments for comprehensive treatment and actively create conditions for surgery. In case of combined pleural effusion, if the amount of effusion is large and affects FRC, thoracentesis to release fluid or placement of drainage device is feasible. In case of tension pneumothorax, closed chest drainage should be placed and the drainage tube should not be removed 24h before general anesthesia.
(B) Respiratory tract preparation
1.Clean respiratory tract: Before thoracic surgery, the patient’s respiratory tract should be kept open and the secretions in the respiratory tract should be removed in a timely manner. At present, the main drugs used for respiratory tract cleaning are mucus secretion promoting drugs and mucus dissolving drugs. The efficacy of mucus secretion promoting drugs (ammonium chloride) is difficult to be sure, especially when the sputum is thick and almost ineffective; mucus dissolving drugs are represented by amiloride, which is the effective product of bromoxyn in the body, and can promote the dissolution of mucus sputum, reduce the adhesion of sputum and cilia, and increase the discharge of respiratory secretions. In addition, fluid infusion, nebulized inhalation to wet the airway, nebulized bronchodilator, postural drainage and chest and back tapping are all beneficial to the discharge of respiratory secretions.
2.Relief of airway spasm: bronchospasm is one of the most common complications during the perioperative anesthesia period. Especially during the period of surgical anesthesia, once the patient has severe bronchospasm, if not handled in time, it can lead to severe hypoxia and CO2 accumulation, and even life-threatening. Bronchospasm can be induced by anesthetic drugs and tracheal intubation during surgery, and the mortality rate can be as high as 70%.
In acute asthma attacks, any elective surgery should be postponed until the asthma is effectively controlled when the bronchospasm has not been eliminated. Preoperative application of bronchodilators (e.g. ipratropium bromide) can significantly reduce pulmonary resistance, improve pulmonary compliance, and prevent the occurrence of bronchospasm. In addition, for elderly, COPD and asthmatic patients, preoperative application of rapid-acting bronchodilators is beneficial to improve basal lung function and improve patients’ oxygen saturation, which can further improve the quality of preoperative preparation.
(iii) Anti-infection
For acute upper respiratory tract infection, elective surgery should be performed after the treatment has improved. For those with large amount of sputum, surgery should be performed 1-2 weeks after sputum reduction. For those with combined chronic respiratory diseases, antibiotics should be routinely applied 3 d before surgery in order to prevent and control pulmonary infections. The pathogenic microorganisms of pulmonary infections include bacteria, fungi and viruses, and the rational application of antibiotic therapy is the key.
Anesthesia selection
The ideal anesthesia method and drug selection principles are: less respiratory and circulatory disturbances; good sedation, analgesia and muscle relaxation; satisfactory blockage of adverse surgical reflexes; fast recovery from postoperative awakening; and few complications. The effective solution to the respiratory and circulatory disturbance caused by dissection is endotracheal intubation and the application of inotropic drugs to control breathing, so general thoracic surgery are used for general anesthesia.
IV. Intraoperative management
1, shorten the anesthesia and operating time: choose the incision (such as transverse incision) and simple and practical operation style that has little effect on the strength of abdominal muscle and light postoperative pain.
2, the surgical operation advocates minimally invasive: anesthesia intubation should be as non-invasive as possible. Surgery should be performed to protect lung tissue as much as possible, avoiding excessive pulling, squeezing and twisting of lung tissue, and tightly stopping bleeding during surgery. When lung cancer patients undergo lung resection, two major principles must be observed: maximum removal of tumor and maximum preservation of lung tissue. Thoracic integrity should be ensured, especially in the management of severe thoracic trauma and large resections of chest tumors and chest wall tissues. The integrity of the recurrent laryngeal nerve and vocal cords should be protected; bilateral recurrent laryngeal nerve injury will lead to serious consequences. Protect the phrenic nerve and diaphragm integrity; prevent phrenic nerve injury and diaphragmatic hernia from occurring. Timely detection and management of tension pneumothorax and related post-thoracic surgery complications (such as hemothorax, celiac disease, pulmonary embolism, etc.).
3.Ensure airway patency and maintain adequate ventilation: ensuring airway patency is the most important aspect of thoracic surgery anesthesia, so that adequate oxygen supply and good CO2 expulsion can be achieved. However, PaCO2 <35mmHg for a long time should be avoided, otherwise it may cause cerebral vasospasm and insufficient blood supply.
4.Maintain circulatory stability: avoid excessive high or low blood pressure, prevent cardiac arrhythmia, and correct shock in a timely manner.
5, standardize intraoperative infusion: ensure at least two intravenous access: one access can rapidly transfuse blood and fluids; one access can monitor central venous pressure and give cardiovascular active drugs. The total amount of rehydration should be limited and the infusion rate per unit time should be controlled so as not to overload the circulation and lead to intraoperative or postoperative pulmonary edema and heart failure.
6. Others: handle negative venous pressure carefully to prevent air embolism; for those who need long-term indwelling gastric tube for decompression, it is advisable to make a gastrostomy instead to avoid affecting cough and sputum; handle fracture gently to avoid fat embolism; for those who have a higher possibility of postoperative pulmonary infection, the abdominal incision should be reduced and sutured to prevent splitting. Intraoperative application of bronchodilator can prevent bronchospasm.
V. Postoperative treatment
1. Keep the respiratory tract unobstructed: encourage patients to actively cough, breathe deeply, pat the chest wall, combine with postural drainage, and assist patients to expectorate. Powerful expectoration after surgery can make sputum thinner, less viscous and easy to cough up, or accelerate the function of respiratory mucous membrane cilia and improve the function of sputum transfer. Ambroxol is an effective pharmacological treatment to prevent postoperative pulmonary complications (especially pulmonary atelectasis, acute lung injury, hypoxemia, ARDS, etc.), and the dose can be increased appropriately if necessary. Start nebulized inhalation as early as possible to moisten the airway, make secretions easy to discharge, and relieve edema and bronchospasm. Bronchodilators dilate the airway and are combined with expectorant therapy to facilitate sputum expulsion and release edema and bronchospasm. Stimulated spirometry is the main means to prevent mucus plug and prevent postoperative pulmonary atelectasis.
2.Effective analgesia: effective postoperative analgesic measures can promote patients’ early diaphragmatic movement, coughing and sputum excretion, and reduce the complications of pulmonary co-infection that damage lung function. However, the dosage of analgesic drugs should be individualized, especially for elderly patients, and the dosage should be appropriately controlled, and postoperative anesthesia visits should be strengthened to avoid excessive sedation or respiratory depression.
3, other: postoperative nasal catheter oxygen in COPD patients, the flow rate should be <3L/min; maintain the balance of fluid intake and output; take measures to reduce abdominal distension, timely removal of the gastric tube; reasonable application of effective antibiotics.