Anesthesiologists need to use various drugs to maintain a certain anesthesia state, and at the same time ensure the safety of patients during the whole operation and provide safe and painless operation conditions. However, patients and operations vary widely, and there may still be some unexpected situations, some of which are likely to endanger life safety.
1. Reflux, aspiration and aspiration pneumonia
Vomiting or reflux under anesthesia may lead to serious consequences, and aspiration of stomach contents may even lead to serious pulmonary complications such as acute respiratory obstruction, which is one of the important causes of death of patients under general anesthesia at present. The degree of acute lung injury caused by aspiration of patients is directly related to the physical and chemical properties (such as pH, fat fragments and their size), capacity and bacterial contamination of gastric contents inhaled by aspiration.
Clinical manifestations of aspiration include acute respiratory obstruction, Mendelssohn syndrome, aspiration atelectasis and aspiration pneumonia. Prevention of aspiration is mainly aimed at the causes of aspiration and lung injury:
(1) decrease gastric contents and increase the pH value of gastric juice;
(2) Reduce the intra-gastric pressure below the resistance of the lower esophageal sphincter;
(3) Protecting the airway, especially when the airway protective reflex disappears or weakens, is more important. The key to treat aspiration is to find out and take effective measures in time to avoid airway obstruction and asphyxia and alleviate acute lung injury. Specific measures include airway reconstruction, bronchial irrigation, correction of hypoxemia, hormones, bronchoscopy, antibiotics and other supportive therapies.
In order to reduce the possibility of reflux aspiration, surgical patients often need to fast water before operation, generally fasting for 6 ~ 8 hours, drinking water for 4 hours, and children can control it in 2 hours.
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During the recovery period of general anesthesia, most patients are sleepy, quiet or slightly disoriented, and their brain functions gradually return to normal, but some patients still have great emotional fluctuations, which are manifested as uncontrollable crying and restlessness. The emergence of restlessness is related to medication before and during operation, and postoperative pain may be an important factor causing restlessness.
3. Delayed recovery after general anesthesia
After stopping general anesthesia, patients can generally wake up within 60 ~ 90 minutes, and their memory of instructions, orientation and preoperative memory can be restored. If the consciousness is still not very clear after this time limit, it can be considered that the awakening after general anesthesia is delayed. The common causes of delayed recovery after general anesthesia are prolonged drug action time, old age, systemic metabolic diseases of patients, central nervous system injury and so on.
4. Postoperative nausea and vomiting
Postoperative nausea and vomiting (PONV) is a very common problem after general anesthesia, which brings discomfort to patients and affects their rest. Its incidence rate is 20% ~ 30%. The incidence of female and inhalation anesthesia is relatively high. Risk factors include:
(1) Patients with early pregnancy, diabetes, anxiety and other inducing factors;
(2) Increased gastric capacity
(3) Anesthetic drugs and methods General anesthesia is more common than regional anesthesia; Nitrous oxide, ketamine and neostigmine are the most commonly used drugs.
(4) Common surgical sites and methods, such as ovarian and cervical dilatation, laparoscopic surgery, strabismus correction, middle ear surgery, etc.
(5) Opioid drugs, hypotension and plenty of drinking water are used for postoperative pain. The stimulation of gastrointestinal decompression catheter also often causes vomiting. Only patients with obvious tendency to develop PONV should consider taking drugs, and preventive drugs are generally not needed. The main drugs are butylbenzene, phenothiazine, gastric motility drugs, anticholinergic drugs, antihistamines, serotonin antagonists and so on.
4. Bronchial spasm
Acute bronchospasm can occur during anesthesia and after operation, which is characterized by spasmodic contraction of bronchial smooth muscle, airway stenosis, sudden increase of airway resistance, and difficulty in exhaling and breathing, leading to severe hypoxia and CO2 accumulation. If it is not relieved immediately, the patient will not only have hemodynamic changes, but even have arrhythmia and cardiac arrest because of the inability to effectively ventilate.
The causes of bronchospasm are airway hyperresponsiveness, nerve reflex related to anesthesia operation, local stimulation such as tracheal intubation, application of anesthetics, muscle relaxants or other drugs with excitatory vagus nerve to increase airway secretion and promote histamine release. Among them, local stimulation such as tracheal intubation is the most common cause of airway spasm during anesthesia induction. Patients with chronic respiratory inflammation, smoking or bronchial asthma have a high incidence, so drugs that can induce bronchospasm should be avoided during anesthesia. Choosing local anesthetics to perfectly anesthetize the surface of throat and trachea and block airway reflex can prevent bronchospasm induced by stimulating airway. The treatment of bronchospasm includes: defining the inducement and eliminating the stimulating factors; If the anesthesia is too shallow, it should be deepened; Mask oxygen, assist or control breathing when necessary; Intravenous infusion of corticosteroids, aminophylline, etc. It may be better to use two drugs at the same time.
5. Hypoxemia and insufficient ventilation
Respiratory complications are still one of the main reasons for delaying postoperative rehabilitation and threatening patients' lives after general anesthesia. The most common causes of airway obstruction after general anesthesia are incomplete recovery of consciousness and pharyngeal obstruction caused by falling tongue. Laryngeal obstruction can be caused by laryngeal spasm or direct airway injury. The most effective way to treat glossoptosis is that the patient's head leans back, and at the same time the mandible and lower incisors bite the upper incisors. According to the patient's different body positions, make appropriate adjustments to achieve complete airway patency. If the above manual treatment fails to relieve the obstruction, nasopharynx or oropharynx airway should be inserted. However, when the entrance pharyngeal airway is inserted, it may induce nausea, vomiting and even laryngeal spasm, which should be closely observed. Very few patients need to be intubated again.
Hypoxemia is not only a common complication after general anesthesia, but also can lead to serious consequences, even coma and death. Factors that easily lead to hypoxemia after anesthesia are:
(1) Patient age >: 65 years old;
(2) Overweight patients, such as >; 100kg；
(3) General anesthesia is more likely to happen to patients than regional anesthesia;
(4) anesthesia time >; 4 hours;
(5) Abdominal surgery has a more significant effect on respiration than chest surgery, and limb surgery has a smaller effect;
(6) Anesthetic drugs: If benzodiazepines are combined with opioids, thiopental induced anesthesia has a more significant effect on breathing than propofol.
2. Hypoventilation refers to the increase of PaCO2 _ 2 caused by the decrease of alveolar ventilation. The reasons for postoperative insufficient ventilation are:
(1) central respiratory drive is weakened;
(2) insufficient recovery of respiratory muscle function;
(3) CO2 production increased in vivo;
(4) Affected by acute or chronic respiratory diseases.
6. Acute atelectasis
Acute atelectasis refers to the sudden collapse of lung segment, lobe or one side of lung, thus losing ventilation function. Acute atelectasis is one of the serious complications after operation, especially after general anesthesia. Insufficient compensation of respiratory function can cause a large area of acute atelectasis, which causes patients to die due to severe hypoxia.
Risk factors of acute atelectasis: perioperative patients have acute respiratory infection; Acute or chronic airway obstruction, the most common reason after operation is that the airway is blocked by viscous secretions; Chronic tracheitis; Smoking; Obesity; Elderly patients with low vital capacity, such as non-obstructive pulmonary disease, chest malformation, or respiratory muscle disorder or limitation caused by muscle, neuromuscular and nervous system diseases;
7. Hypoventilation syndrome
Patients with central or obstructive sleep apnea syndrome.
Risk factors for postoperative atelectasis include:
(1) There are many respiratory secretions, and the drainage or discharge is not smooth;
(2) Patients undergoing major chest or epigastric surgery;
(3) Pain of surgical incision;
(4) Improper use of analgesics;
(5) Use drugs that inhibit the central nervous system.
8. Hypertension
In the recovery period of general anesthesia, with the disappearance of anesthesia effect, pain and discomfort, as well as the stimulation of sputum aspiration and extubation, it is easy to cause hypertension. Especially in patients with a history of hypertension, and most of them begin within 30 minutes after operation. If antihypertensive drugs are suddenly stopped before operation, the occurrence of hypertension will be more serious. The causes of hypertension include: pain, hypoxemia and hypercapnia, intraoperative volume overload, improper use of pressor, sputum aspiration stimulation, others such as postoperative chills, urinary retention, bladder hyperexpansion, etc.
9. cerebrovascular accident
Most patients had cerebrovascular diseases before, but they had an accidental stroke during anesthesia operation (perioperative period), of which about 80% were due to insufficient blood supply to the cerebral vessels (or too little blood flow), which was called ischemic stroke, and the other 20% belonged to hemorrhagic stroke (such as cerebral hemorrhage and subarachnoid hemorrhage). The range of stroke can be focal, multifocal or diffuse, which reflects the disorder of rapid brain function caused by single or multiple vascular diseases. Old age (over 65 years old), hypertension, diabetes, abducent vascular disease and heart disease (coronary heart disease and atrial fibrillation, etc.). ) are high risk factors of cerebrovascular accident in perioperative period.
During general anesthesia, because the patient is asleep, the monitoring of the patient's consciousness and muscle strength is affected, and the occurrence of stroke may not be detected in time.
10. Malignant high fever
Malignant hyperthermia (MH) is an abnormal hypermetabolic state of skeletal muscle induced by inhalation of powerful volatile anesthetics and succinylcholine. Exhaled CO2 and body temperature suddenly rise, leading to tachycardia and myoglobinuria. MH is mostly white, but it has been reported in different races, indicating that MH has no racial specificity. The incidence of MH in children (115000) was significantly higher than that in adults (1/50000). Children are mostly under the age of 10, and men are more than women. MH is common in congenital diseases, such as idiopathic scoliosis, strabismus, ptosis, umbilical hernia and inguinal hernia. It has also been reported in other surgical diseases. At present, MH is considered as a subclinical myopathy with familial inheritance. The clinical manifestations of MH can be divided into explosive (22%), masseter spasm (22%) and abortion (57%). The explosive type is the most serious, showing sudden hypercapnia and hyperkalemia, rapid arrhythmia, severe hypoxia and acidosis, and the body temperature rises sharply, reaching 45℃ ~ 46℃. Most patients died of refractory arrhythmia and circulatory failure within a few hours.
reference data
1. Zhuang Xinliang Zeng Chen Boluan Modern Anesthesiology Third Edition People's Health Publishing House 2010936-1041.
2. Guo Xiangyang, Luo, China Anesthesiology of Malignant Hyperthermia 200 1, 2 1 (10): 604-606.
3. Luo, Tian, et al. Journal of Clinical Anesthesiology 2012,28 (4): 413-416.