The pathophysiological changes caused by thoracotomy are far more obvious than those in other sites. Elderly patients are generally accompanied by heart and lung function impairments, which greatly increases the difficulty of anesthesia management. According to the latest national survey on the causes of death of residents, lung cancer has surpassed liver cancer as the leading cause of death from malignant tumors in China. For elderly lung cancer patients with early diagnosis and no contraindications, surgery is still an important treatment. For elderly thoracic surgery patients, preanesthesia assessment, preparation, and perioperative management are closely related to postoperative outcomes. This article reviews the progress of perioperative anesthetic management in elderly patients undergoing thoracotomy.

 

1. Physiological changes in the elderly's breathing and circulatory system

 

1.1 Respiratory changes and complications

 

Changes in the elderly's respiratory system and comorbidities have important implications for anesthesia management. The degenerative changes in the structure and physiological function of the elderly's respiratory system occur, manifested as reduced lung volume, decreased pulmonary ventilation, and increased probability of upper airway obstruction. In terms of lung function, forced expiratory volume in one second (FEV1) and forced vital capacity (FVC) were progressively reduced, residual air volume was increased; the number of capillaries in the alveolar wall and blood perfusion in the tube were decreased. The gas exchange area is reduced and the lung ventilation function is reduced.

 

In the lower respiratory tract, bronchial mucosa epithelium atrophy with hypersecretion, some lumen narrowing, increased airflow resistance prone to breathless dyspnea, increased the probability of perioperative infection in elderly patients. In the lower respiratory tract, atrophy of the pharyngeal mucosa and pharyngeal lymphoid tissue results in enlarged pharyngeal cavity, thinning of the mucous membrane of the larynx, reflexes of the mucocutaneous sensation and epiglottis defense. If combined with changes in the central nervous system (stroke, Parkinson's disease, etc.) will also reduce this defensive reflex. Therefore, it is difficult for some elderly patients to leave the ventilator after surgery. With the physiological changes of the respiratory system, the elderly often have respiratory diseases. The history of smoking as an important factor affecting thoracic surgery and anesthesia needs our attention.

 

Chronic bronchitis occurs in 50% of patients undergoing smoking, and chronic obstructive pulmonary disease (COPD) occurs in 15%. Cigarette smoking changes the structure and function of the airway epithelium, showing decreased mucociliary clearance, narrowing of small airways, and thickening of the tracheal mucosa. As a result, airflow restriction and FEV1 decrease. These can affect the oxygen uptake and transport of the lungs and reduce the ventilatory function reserve. At the same time, there was a significant increase in the incidence of cough, hypoxemia, throat, bronchospasm, apnea, and restlessness in patients with a history of smoking. All of these increase the risk of anesthesia in elderly patients with chest surgery.

 

1.2 Circulatory System Changes and Combined Diseases

 

The physiological structure and function of the elderly circulatory system have changed significantly. Left and right ventricle volume reduction, intimal non-uniform thickening, conduction system degeneration (transduction block, arrhythmia), heart valve changes (calcification, insufficiency), decreased wall contractility and myocardial and coronary amyloid deposits ( Coronary atherosclerotic heart disease (cardiac atherosclerotic heart disease) leads to a decline in cardiac function and a decrease in cardiac reserve in elderly patients; degenerative changes in large arteries result in a decrease in elasticity, resulting in a common simple systolic hypertension in elderly patients; a decrease in venous pressure and a capillary metabolic rate The decrease resulted in insufficient oxygen supply to the tissues. Although the above-mentioned changes and comorbidities can provide blood supply and oxygen supply to the myocardium and various organs through the compensatory mechanism in daily life, their functional changes and reserve capacity decline under the attack of anesthesia and surgery have become a threat to the perioperative safety of elderly patients. Important factors.

 

2. Preoperative evaluation and preparation

 

The decline in the body's ability to regulate the elderly patients, for the anesthesia and surgical trauma adaptation and affordability decline, if there is more than a fatal threat to the above complications, we need to carefully assess the patient's heart, lung function and comorbidities before surgery and Disposal, strict grasp of anesthesia indications, and development of individualized anesthesia programs ensure maximum perioperative patient safety.

 

For respiratory evaluation, studies have shown that elderly patients with a BMI of >24 kg/m2, a smoking index of >400, and poor lung function and nutritional status have an increased risk of postoperative pulmonary complications. For patients with a history of smoking, smoking cessation or nicotine replacement therapy 6 weeks before surgery can reduce the incidence of perioperative complications. For patients with COPD, the type, duration, and treatment of the disease should be carefully queried. Preoperative pulmonary function FEV1, <600 ml, FEV1% ≤ 50%, vital capacity (VC) ≤ 1700 ml, FEV1/VC ≤ 32% ~ 58%, partial pressure of oxygen (PaO2) ≤60 mmHg (1 mmHg=0.133 kPa) or peak expiratory flow rate (PEFR)≤82 L/min, suggesting that patients are prone to postoperative hypophyseal pneumonia, pulmonary atelectasis, and respiratory failure may occur .

 

For the assessment of the circulatory system, it is important to distinguish the type of heart disease, determine the heart function, and master the state of oxygen supply to the heart. The methionine (MET) evaluation, revised cardiac risk index (RCRI) and Goldman's heart risk index are all important evaluation indicators. If MET<4, Goldman's cumulative score reaches grade III/IV, or RCRI meets or exceeds 3 criteria, the surgical risk is greater and sufficient preoperative preparation is required to improve cardiac and general conditions to improve Anesthesia and surgical safety H1.

 

3. Intraoperative anesthesia management

 

3.1 Intraoperative infusion and circulation management

 

In elderly patients, the ability to adjust body fluids is reduced. Therefore, attention should be paid to the management of the amount of fluid in the operation. Thoracic surgery anesthesia using goal-directed fluid therapy (GDFT) rehydration programs can benefit patients more. A large sample study confirmed that the use of GDFI "allows the patient to limit intraoperative and intraoperative fluid input to 1 to 2 ml kg-1 h-1, which can significantly reduce pulmonary edema, postoperative acute lung injury / acute respiratory distress The incidence of syndrome, at the same time during surgery should be closely observed whether the patient's hypoperfusion phenomenon, such as the emergence of timely application of vasoactive drugs to maintain the stability of the circulation to prevent hypoperfusion injury organs and acute kidney injury.

 

Functional changes and degeneration of the circulatory system in elderly patients result in poor tolerance for hemodynamic changes. The anesthetic drugs' myocardial inhibition and surgical anesthesia stress may cause or aggravate the dysfunction of the vital organs of the elderly patients. Therefore, maintaining the stability of the intraoperative circulation has an important influence on its prognosis. Studies have confirmed that the application of anesthesia depth monitoring in elderly anesthesia for thoracic surgery helps to maintain the stability of the patient's circulation and reduce the amount of anesthetic drugs, shorten postoperative recovery time, and reduce the probability of complications during anesthesia. For elderly patients with cardiovascular disease, anesthesia depth monitoring is even more important. In addition, for elderly patients, we should pay attention to and reasonably apply vasoactive drugs to maintain the hemodynamic stability.

 

3.2 Narcotic drugs

 

The distribution volume of plasma in the elderly decreased, compared to younger and middle-aged patients, the same dose of anesthetic drug concentrations in the plasma and cerebrospinal fluid increased, resulting in older patients with increased sensitivity to anesthetic drugs. Therefore, attention should be paid to the changes in the pharmacokinetics and pharmacodynamics of anesthetic drugs in elderly patients with thoracic diseases. Accurately calculate the dose of anesthetic drugs so as to avoid excessive inhibition of cardiac function and fluctuations in hemodynamics. Monitoring the depth of anesthesia during the operation can avoid the deep anesthesia and reduce the use of vasoactive drugs. At the same time, it can avoid intraoperative awareness caused by insufficient dosage of anesthetic drugs, and can shorten the recovery time of patients and recovery time in the PACU. On the other hand, patients with thoracic surgery often use one lung ventilation (OLV) to control the breathing, resulting in damage to alveolar cells and release of inflammatory factors.

 

Studies have shown that inhalation of human anesthetics (such as desflurane, sevoflurane, etc.) can reduce the immune response to the respiratory system by reducing the secretion of inflammation-related cytokines. Intravenous anesthesia with propofol-dominated total anesthesia can increase the secretion of inflammation-related cytokines and the accumulation of granulocytes in the alveoli. Recent studies have confirmed that halogen-based inhaled anesthetics can reduce the release of alveolar inflammatory mediators in thoracic anesthesia, and inhibit airway inflammation by regulating granulocyte aggregation and activation of neutrophils. effect. Some scholars believe that general anesthesia combined with thoracic epidural anesthesia and paravertebral block is favorable for early extubation in elderly patients with chest surgery and facilitate postoperative epidural analgesia.

 

3.3 Respiratory management

 

3.3.1 OLV

 

For patients with thoracic surgery, in order to facilitate the operation of the affected lung and reduce the probability of infection on the contralateral lung and tumor dissemination, intraoperative double-lumen endotracheal tube or occluded tube is used to separate the bilateral lungs and implement OLV. OLV itself will increase the mechanical pressure of the contralateral alveolar cells to make it over-expand and increase the pressure in the alveolar capillaries. This leads to pulmonary ventilation damage and osmotic pulmonary edema, leukocyte accumulation, cytokine release, and neutrophil-mediated lung tissue injury. On the other hand, OLV leads to reduced lung ventilation, reduced ventilation area, and a decrease in ventilation/flow ratio in the lower lobe of complete supraconjugation lateral organ compression ventilation, which increases intraoperative hypoxemia. The incidence of oxygen and hypercapnia. In recent years, advances in the development and monitoring of pulmonary isolation technology have enabled us to detect hypoxemia early and to alleviate intraoperative hypoxemia and hypercapnia by optimizing oxygen supply to ventilated lungs and applying positive continuous pressure ventilation to affected lungs. Anemia. However, respiratory management in chest surgery is still a difficult problem for anesthesiologists.

 

3.3.2 Lung reexpansion technique and positive end expiratory pressure (PEEP)

 

The relative increase in tidal volume during OLV increases the mechanical dilation of the contralateral alveoli, making it easy to damage the alveolar epithelium and vascular endothelium by excessive traction. At the same time, due to the compression of the lateral abdominal organs, the end-expiratory volume at the time of OLV decreases and the alveolus collapses easily. Frequent cyclical opening and closing of the alveoli during mechanical ventilation results in a large loss of pulmonary surfactant, and shear forces between collapsed and open alveoli can lead to lung injury, which can cause atelectasis and pulmonary edema. Performing lung resuscitation and adding PEEP during OLV can effectively reduce alveolar damage, improve oxygenation, and reduce the incidence of atelectasis. Some studies have confirmed the application of pulmonary reexpansion techniques: pressure control ventilation mode, airway pressure = 30 cmH2O (1 cmH2O = 0.098 kPa) combined with small tidal volume and PEEP (5 cmH2O) can guarantee good oxygenation, and reduce lung failure by 60% Zhang happens.

 

3.3.3 Tidal Volume Setting of OLV

 

Several studies have confirmed that high-tidal volume ventilation (tidal volume ≥10 ml/kg) during OLV can cause hyperventilation of the ventilated lung, increase pulmonary vascular resistance, flow blood to the non-ventilated side of the lung, increase hypoxemia, increase the circumference Lung injury during surgery. Reduce intraoperative tidal volume and alveolar pressure can reduce mechanical damage, and can reduce the release of cytokines such as TNF-α, plasma soluble intercellular adhesion molecule-1 and other cytokines, reduce lung immune response, and play an important role in the perioperative period. Protective effects.

 

OLV tends to increase respiratory rate due to reduced tidal volume, but it should not cause hyperventilation. Studies have confirmed that intraoperative hyperventilation (pressure of arterial carbon dioxide (PaCO2) <30 mmHg] can reduce cerebral perfusion and oxygenation, and is associated with postoperative cognitive impairment. On the contrary, maintaining a slightly higher PaCO2 (40-50 mmHg) during surgery can increase brain tissue perfusion and oxygenation. Controlled tidal volume ventilation (tidal volume = 5 to 8 ml/kg) for elderly thoracic surgery patients while maintaining PaCO2 (40–50 mmHg) and a small airway pressure can effectively reduce intrapulmonary shunts and maintain effective oxygen Together, and reduce the incidence of perioperative respiratory complications.

 

3.4 Body temperature management

 

Perioperative hypothermia is a common complication in patients undergoing thoracic surgery, especially in patients undergoing senile surgery. This is due to a decrease in muscle atrophy and decline in metabolic capacity as a result of aging, resulting in decreased ability to produce heat. For patients undergoing thoracic epidural anesthesia and paravertebral block, the anesthetic blockade of thermosensory sensory nerves reduces the body's ability to perceive changes in its own body temperature, while raising the threshold of its own heat-generating activation, making it hypothermia. The phenomenon is more obvious. Perioperative low body temperature can lead to a series of complications, including perioperative bleeding tendency, increased myocardial ischemia, decreased drug metabolism, prolonged postoperative recovery of anesthesia, poor wound healing, and increased probability of infection. Therefore, it is very important to maintain the stability of body temperature in elderly patients with thoracic surgery.

 

4. Postoperative management and analgesia

 

4.1 Anesthesia Recovery Period

 

In the early post-surgery period, even if the patient has recovered consciousness, the remaining anesthetic drugs in the body have not been completely metabolized, and the protective reflex has not completely recovered, making the incidence of respiratory and circulatory complications increased during this period. Studies have shown that the abnormal rate of circulatory system in patients with PACU is 7.3%, mainly due to various causes of hypertension and bradycardia; and the incidence of respiratory complications is 4.6%, mainly the incidence of hypoxemia Higher. In elderly patients, due to reduced respiratory function, there is a physiological potential for hypoxemia; release of inflammatory mediators during surgery, increased capillary permeability, impaired lung diffusion, and pure oxygen in anaesthesia are all hypoxic after surgery. The cause of the disease. In elderly patients after pneumonectomy and ASA grade III or higher, the incidence of postoperative hypoxia increased significantly.

 

Prevention of postoperative hypoxemia occurs during the operation should minimize the time of anesthesia, the condition allows to reduce the proportion of pneumonectomy. If hypoxemia occurs, judge the cause promptly, observe the patient's respiratory status, and auscultate the breath sounds. For upper airway obstruction due to common tongue fallback and other factors, the patient can be placed in the entrance pharynx or nasopharyngeal airway and increase the inhaled oxygen concentration. Patients with refractory hypoxemia caused by pulmonary edema and other factors should fully evaluate the state of the patient. If the concentration of inhaled oxygen is increased, if not relieved, auxiliary positive pressure ventilation may be considered. In addition, care should be taken to prevent the occurrence of venous thrombosis. Specific measures include massaging the lower limbs. Increase activity, wear elastic stockings and apply low molecular weight heparin.

 

4.2 Postoperative analgesia

 

Poor lung function reserve in the elderly, coupled with surgical incision pain after chest surgery makes patients afraid to take a deep breath, prone to cause pulmonary infection and even respiratory failure. Postoperative adequate analgesia is beneficial to early cough and sputum discharge, improve lung function, reduce postoperative complications, and shorten hospital stay. Currently advocates postoperative multimodal analgesia, intravenous analgesia is mainly opioids and nonsteroidal drugs.