Anesthesia preparation
(A) Patients undergoing elective surgery
1. About cardiovascular medication
Preoperative adjustments should be made to the medications commonly used by cardiac patients. Anti-arrhythmics and anti-hypertensives should continue to be used until the day of surgery. Sudden discontinuation of adrenergic receptor blockers, centrally acting antihypertensives (methyldopa, colistin), nitroglycerin or calcium channel blockers can cause myocardial ischemia, hypertensive accidents and arrhythmias. Therefore, in principle, none of them can be discontinued casually, while making the symptoms improve, myocardial ischemia and arrhythmia improve, and controlling blood pressure below 160/110mmHg.
2.Maintain water and electrolytes
Balanced cardiac patients are prone to hypokalemia due to diuretics or limited feeding, so attention should be paid to potassium supplementation before surgery to maintain blood potassium above 3 or 5 mmol/L.
(II) Patients with acute surgery
Some of the above preparations should be completed as much as possible, while ECG, blood gas and electrolyte examination should be performed in a limited time to deal with arrhythmia (e.g. rapid atrial fibrillation) or heart failure, commonly used such as deacetyl trichothecene C (cidilan) to support cardiac function and correct water and electrolyte disorders, especially hypokalemia should be corrected.
Anesthesia selection and application
(A) Intra-vertebral block
At present, it is generally accepted that intrathecal block is superior to general anesthesia for non-cardiac surgery in cardiac patients. Patients with intradural block (including epidural anesthesia, lumbar anesthesia and sacral block) basically remain awake, and the incidence of reoccurrence of myocardial infarction in patients who have had myocardial infarction under subarachnoid block (lumbar anesthesia) is less than 1%, while the incidence of myocardial infarction under general anesthesia is 2%-8%. The reason for this may be that intralesional anesthesia has less impact on cardiopulmonary function and provides good postoperative analgesia. Sacral anesthesia has no significant effect on circulatory dynamics, and the block is fully adaptable to anal and perineal area surgery and cystoscopy.
Subarachnoid block, if the block plane is not properly controlled, it has a great impact on hemodynamics and can cause a sharp drop in blood pressure, which is dangerous for cardiac patients, so it is only suitable for perineal, anal and lower extremity surgery, and the plane must be controlled around T10, but the subarachnoid block uses a small amount of drugs, and the complete block is its advantage. Continuous epidural block can be divided into small amounts of local anesthetic solution injected through the catheter, the scope of block can be properly controlled, and the effect on blood pressure is more moderate. Continuous epidural block can also be used for cesarean delivery in advanced pregnancies with preeclampsia. The catheter can be retained for postoperative analgesia, which has a definite effect and helps to reduce postoperative cardiac and pulmonary complications.
(II) General anesthesia
For patients with severe disease, poor cardiac function reserve, complex surgery, intraoperative hemodynamic instability and expected lengthy surgery are advocated to use endotracheal general anesthesia, which can maintain an open airway, effective oxygenation and ventilation, the ideal induction of general anesthesia should be rapid, smooth and non-exciting, without excessive excitation or inhibition of the sympathetic and parasympathetic nervous system, minimizing the impact on hemodynamic. . Anesthesiologists are familiar with the effects of anesthetic anesthetics on circulatory function, and the main principles are to avoid anesthetic-induced myocardial depression.
①Inhaled anesthetics increase with MAC, which can slow down the heart rate, reduce myocardial contractility, and decrease cardiac output.
② intravenous anesthetics such as isoproterenol, which decreases peripheral resistance, increases heart rate and decreases myocardial contractility, imipramine, which decreases blood pressure and peripheral resistance, ketamine, which excites sympathetic nerves, increases heart rate and blood pressure, and thus increases oxygen consumption, etomidate with 0,2~0,3mg/kg induction dose, the changes of heart rate, peripheral resistance and cardiac blood volume are not obvious.
Pancuronium bromide increases heart rate, but when combined with fentanyl, heart rate and blood pressure can be kept stable. Succinylcholine can cause arrhythmia, and atracurium 2~3 times ED95 can increase heart rate, while no significant change in heart rate was observed with vecuronium bromide or cis-atracurium. In addition, in order to moderate the stress response to tracheal intubation, appropriate amount of fentanyl 2~5μg/kg, or esmolol 0,25~0,5mg/kg, or labetalol 5mg, and lidocaine 1mg/kg can be added as needed to prevent tachycardia and elevated blood pressure.
Anesthesia can be maintained by static inhalation compound anesthesia, adjusting the appropriate depth of anesthesia, and the concentration of inhaled general anesthetic generally does not exceed 1MAC, so as not to cause myocardial depression. There is no evidence about isoflurane causing coronary artery steal, and isoflurane or sevoflurane is generally the better choice. Meanwhile, isoproterenol can be infused intermittently or continuously to maintain a certain depth of anesthesia while keeping hemodynamic stability.
(C) Valvular heart disease
Patients with valvular heart disease undergoing anesthesia for non-cardiac surgery should pay attention to the patient’s preoperative use of diuretics, as induction of anesthesia can result in severe hypotension due to insufficient blood volume. In patients with atrial fibrillation, preoperative digitalis dosage is insufficient, and ventricular rate tachycardia before anesthesia can be added with digoxin 0,125-0,25 mg or deacetyl trichosanthin 0,2 mg by sedation. If the ventricular rate is controlled after verapamil and becomes sinus rhythm, verapamil 0,6-1,2ug/kg/min can be infused as needed to maintain the efficacy.
Immediately before anesthesia, if the patient develops pulmonary edema aura, often related to excessive anxiety, with increased ventricular rate and peripheral vasoconstriction, in addition to the appropriate amount of digitalis, immediately inject morphine 10mg, mask pressure oxygenation, if necessary, nitroglycerin and the above therapeutic drugs. Intraoperative attention should be paid to adjust the amount of blood and fluid transfusion to prevent postoperative pulmonary edema. The risk of anesthesia for mitral valve insufficiency is less than that for mitral stenosis.
The patient is overloaded with left ventricular volume and generally has limited increase in cardiac work. If blood pressure rises and heart rate slows during anesthesia, regurgitant flow increases, so it is advisable to control blood pressure slightly below the original level and heart rate 80-90 bpm to reduce regurgitant flow. With aortic stenosis or insufficiency, the hemodynamic changes are roughly similar to, but often more severe than, mitral stenosis or insufficiency.
However, due to aortic stenosis, impaired left ventricular drainage, left ventricular centripetal hypertrophy, and reduced ventricular compliance, a slight increase in intraventricular volume causes a significant increase in filling pressures, and patients often have myocardial ischemia and inadequate cardiac output. Ventricular arrhythmias are often difficult to treat when they occur during anesthesia and surgery, so extra caution should be exercised. Key points of anesthesia for noncardiac surgery in patients with valvular heart disease are shown in Table 3 and can be used as goals to be achieved during anesthesia.
(iv) Chronic constrictive heart
Pericarditis has restricted cardiac activity, often with reduced cardiac output, low blood pressure, narrow pulse pressure, often with respiratory distress, elevated venous pressure, hepatomegaly, and thoracoabdominal fluid. In severe cases, the constricted pericardium should be resolved before routine elective surgery can be performed. The main risks of anesthesia in patients with chronic constrictive pericarditis are decreased arterial pressure, slowed heart rate and myocardial depression, especially during induction of anesthesia. Of course, if pericardial decompression is performed, attention should be paid to excessive volume load and increased cardiac afterload after decompression, as this can cause cardiac insufficiency and pulmonary edema due to overload of the newly decompressed myocardium.
(E) Atherosclerotic coronary artery
Heart disease (coronary artery disease) is by far the most common case of cardiac patients undergoing non-cardiac surgery, and the commonly used anesthetics and anesthesia methods do not affect the final outcome of surgery in such patients. The key issue is how to apply and reasonably master them, and to have the ability to judge and handle the clinical problems that can occur at any time in a timely and correct manner. The mortality rate of patients with coronary artery disease undergoing non-cardiac surgery is 2-3 times higher than that of general patients. The most common cause is perioperative myocardial infarction, followed by severe arrhythmias and heart failure, and a normal ECG at the time of calm does not negate the existence of this disease. Previously, it was thought that non-cardiac surgery was not advisable within 6 months after myocardial infarction, mainly due to the high chance of recurrence during the perioperative period, and the mortality rate could still reach 50% once recurrence occurred. However, recent clinical data have found that non-cardiac surgery patients with a history of previous myocardial infarction or within 6 months do not necessarily have a significant increase in perioperative cardiac complications and mortality, but are generally considered to have more serious problems after myocardial infarction if they have.
①Multiple myocardial infarctions ;
②Signs and symptoms of heart failure;
③Left ventricular end-diastolic pressure >2,4 kPa (18 mmHg);
④Cardiac index <2,2L/min/m2;
⑤Left ventricular ejection fraction <40%;
⑥Left ventriculogram shows multiple ventricular motility disorders;
⑦ Poor physical performance.
Elective general surgery after myocardial infarction can be delayed until 6 months after infarction; emergency surgery is life-threatening when performed immediately, and comprehensive hemodynamic monitoring should be used to try to maintain stable circulatory dynamics, moderate the stress response and maintain the balance of myocardial oxygen supply and demand; malignant tumors are estimated to be resectable, and surgical procedures can be considered 4-6 weeks after infarction if the patient is low-risk, and in high-risk patients after cardiac catheterization angiography, echocardiography or cardiac nuclear imaging. In high-risk patients, the need for preemptive coronary stenting or coronary artery bridging will be determined after echocardiography, echocardiography or cardiac nuclear examination.