Characteristics of the condition of patients with pheochromocytoma
1. Pheochromocytoma is a tumor of the adrenal medulla, characterized by paroxysmal unstable hypertension. The adrenal medulla is like a giant sympathetic nerve endings, which normally releases normal amounts of catecholamines into the bloodstream and acts on the corresponding receptors in organs throughout the body. Once the tumor turns into a tumor, the tumor continues to release large amounts of catecholamines, prompting the sympathetic nerves to be in a constant state of hyperexcitability, which can lead to a series of corresponding signs and symptoms. If the tumor mainly releases epinephrine, the signs include elevated blood pressure, large pulse pressure, tachycardia, arrhythmia and elevated blood sugar; if the tumor mainly releases norepinephrine, the main manifestation is elevated blood pressure.
2. Persistent hypertension caused by long-term release of large amounts of catecholamines can lead to damage to tissues and organs throughout the body, with myocardial involvement being the most important, with myocardial fibrous degeneration appearing at an early stage and myocardial cells being replaced by histiocytes and loose connective tissue at a later stage, with the lesions mainly invading the left ventricle.
3. Hypertension caused by pheochromocytoma can be divided into three categories.
(1) Paroxysmal hypertensive episodes, accounting for 30%-50%. The attacks are accompanied by severe headache, palpitations, shortness of breath, precordial pain, nausea, vomiting, increased body temperature, increased blood glucose, and increased blood and urine catecholamines. The attack is often terminated with profuse sweating and extreme weakness.
(2) Persistent hypertension without paroxysmal episodes, with symptoms such as headache, excessive sweating, tremors, and weakness.
(3) On top of persistent hypertension, the blood pressure fluctuates greatly.
Pre-anesthesia preparation for patients with pheochromocytoma
1, control of hypertension preoperative need to apply adrenergic blocking drugs for adequate preparation.
(1) Application of benzylamine or rigitine (α-adrenergic blocking drug).
(1) When there is obvious hypertension, systolic blood pressure is higher than 150 mmHg, diastolic blood pressure is higher than 110 mmHg, benzylamine can be used, the initial amount of 40 mg/day, orally, in increments of 10-20 mg per day, up to 200 mg/day in severe cases. (Or 25 mg/day of Riljadin orally, followed by 3-5 mg of Riljadin intramuscularly 1-2 h before surgery.) Prevent upright hypotension during the drug administration.
② For rapid control of paroxysmal episodes of severe hypertension, Riljadin 1-5 mg (added to 250 ml of fluid intravenously) can be administered along with Phenobarbital. After 1-2 days of application, the drip can be stopped as the blood pressure decreases.
(2) The application of Jinan or Esmolol (β-adrenergic blocking drug): β-adrenergic blocking drug generally can not be used alone, only after the application of α-blocking drugs to see the effect of the application is allowed, otherwise it may cause strong systemic vasoconstriction, and lead to severe hypertensive crisis and heart failure. Therefore, it is only applicable to the application of α-adrenergic blocking drugs and complicated by tachycardia, or when the patient is combined with severe tachycardia or atrial tachycardia.
2. Supplemental blood volume is often associated with erythrocytosis and hematocrit >50% in these patients. Because the blood vessels are often in a highly constricted state, a large amount of plasma is lost, prompting the organism to be in a low blood volume state. Therefore, it is important to emphasize the need to supplement the blood volume deficit before and during surgery.
3, for long-term persistent hypertension with underlying congestive heart failure or myocarditis, digitalis analogues and diuretics can be given.
4.Pre-operative enema preparation should be avoided because of the risk of inducing hypertensive episodes, and can be replaced with a liquid diet and laxatives.
5. Pre-anesthetic medication can be pethidine 50-75 mg, promethazine 25 mg and scopolamine 0.3 mg intramuscularly. Atropine should not be used.
Anesthesia for patients with pheochromocytoma
1. Selection of anesthetics
(1) General anesthetics: N2O, sodium thiopental, tranquilizers, isoproterenol, fentanyl, anflurane, isoflurane, etc. are available.
(2) muscarinic drugs: available pancuronium, atracurium, vincristine, etc. Use succinylcholine sparingly, avoid the barrel arrow poison, and prohibit triiodamine phenol.
2.Anesthesia method selection
(1) Inhalation compound anesthesia: rapid induction of endotracheal intubation, inhalation of Anflurane (or isoflurane)-N2O-O2, compound inotropic drugs, narcotic analgesics to maintain general anesthesia. To control hypertension, vasodilators (e.g. sodium nitroprusside) can be administered intravenously;
Can also be injected into the epidural cavity after general anesthesia, low concentration of local anesthetics to block sympathetic nerves, dilation of peripheral blood vessels to produce hypotensive effect, effective in controlling intraoperative hypertensive episodes. (Specific method: before general anesthesia, perform a thoracic 9-10 epidural puncture tube, and inject 15-20 ml of 0.5%-0.8% lidocaine at a time 10 min before cutting the peritoneum; when the blood pressure rises during the operation, it can be injected again as needed.
(2) Epidural anesthesia: It can also be used, but it is easy to cause extreme discomfort to the patient during the sudden rise and fall of blood pressure during the operation and needs to be lifted by the application of adjuvants.
Intraoperative blood pressure control for pheochromocytoma patients
1. This is one of the most critical treatment measures of surgical anesthesia for pheochromocytoma. During the exploration and separation of the tumor, there is often a sudden rise in blood pressure, with systolic blood pressure reaching 200-280 mmHg or even higher. Once the peripheral vessels of the tumor are severed, a sudden drop in blood pressure often occurs, even if it cannot be measured. This rise and fall in blood pressure during surgery must be actively controlled during anesthetic management.
(1) Before anesthesia, use the cuff puncture needle to open two venous accesses, one for infusion of blood and the other as a route for blood pressure control.
(2) The anesthesiologist must keep close contact with the surgeon, continuously monitor the changes of blood pressure and pulse rate, keep abreast of the progress of surgical tumor separation, and strive to closely cooperate with the process of sudden rise and fall of blood pressure of surgery, so as to obtain the best effect of lowering and raising blood pressure.
2.Blood pressure lowering When exploring and separating tumor, blood pressure often rises suddenly, if it exceeds 20% of the original blood pressure level, then blood pressure lowering should be started immediately. The method of blood pressure lowering (except the above-mentioned compound epidural injection of low concentration of lidocaine), commonly used vasodilator drugs (such as sodium nitroprusside, Rigeltijn, etc.) intravenous drip to lower blood pressure, the drip rate first slow, according to the effect of lowering blood pressure at any time to adjust the drip rate.
If the lowering of blood pressure is not ideal, a single additional Ridgatine 3-5 mg, or a single additional nitroprusside 1-3 mg intravenous slow injection.
The ideal degree of blood pressure lowering is
Lowering to 20%-30% of the original maximum elevated blood pressure level is sufficient. It is very important not to implement a lack of supplementation plan because of high blood pressure.
3.Boosting blood pressure When the surrounding tissues and blood vessels of the tumor are all cut off, the blood pressure often drops suddenly and dramatically, therefore, all antihypertensive measures must be stopped 30 seconds in advance, and sufficient fluid must be given, and norepinephrine should be injected intravenously at a slow rate (1mg in 500 ml of liquid, starting from 10 drops/min and increasing or decreasing the drip rate according to the blood pressure at any time) to boost the blood pressure rapidly.
The drip rate and duration of norepinephrine drip depend on the patient’s preoperative phenylephrine preparation and intraoperative blood volume replenishment. If the preoperative preparation is satisfactory and the intraoperative volume is adequate, only a slow and short titration is usually required; otherwise, it is often necessary to continue the titration for several hours to ten hours or longer to normalize the vascular tone. Once blood pressure has risen and stabilized, the titration rate should be gradually reduced as soon as possible until norepinephrine is completely discontinued.
Other treatments in anesthesia for pheochromocytoma patients
1.Strive to operate the tumor smoothly and gently, and minimize squeezing and pulling to reduce the triggering factors of hypertension.
2. Avoid hypoxia and carbon dioxide accumulation during anesthesia, because both of them increase the secretion of catecholamines in the tumor, especially when carbon dioxide accumulation is easy to complicate serious arrhythmias, such as ventricular tachycardia and even ventricular fibrillation.
3. The amount of blood transfusion and rehydration should be larger than the amount of blood loss. Before cutting off the last blood vessel of the tumor, the blood volume should be expanded appropriately, which can significantly reduce the amount of norepinephrine.
4. Intraoperative continuous monitoring of blood pressure, heart rate, heart rhythm, electrocardiogram, peripheral circulation and SpO2, PetCO2, etc. is required routinely. If ventricular tachycardia or frequent premature ventricular contractions occur, vigilance should be raised and can be treated with intravenous slow injection of lidocaine 1-2mg/kg. Acute heart failure is not uncommon, and rapid digitalis preparations are available if necessary.
5.If both adrenal glands are surgically removed, or if persistent hypotension occurs after surgery, treatment with adrenocorticosteroids should be considered.
6. In patients with pheochromocytoma not diagnosed preoperatively and who have been dissected for an “abdominal mass”, the anesthetic protocol described above is also applicable, but the risks are multiplied by the lack of a rigorous preoperative preparation. The anesthesia must be handled with extra care and caution; the patient’s family must be talked to again to obtain understanding and consent, and sign off on the problem of increased anesthesia risk.