Nekoliko važnih problema epiduralnog bloka

Epidural block has been discovered by the pioneers of anesthesiology for more than 100 years and has made great contributions to the development of anesthesiology. It is also the most commonly used anesthesia method in domestic primary hospitals. Its advantages of simple operation and low cost are irreplaceable for general anesthesia. Due to the pursuit of economic benefits and the one-sided emphasis on "general anesthesia rate", the frequency of epidural blocks used in tertiary hospitals has gradually decreased. With the development of modern anesthesiology, the use of foreign nerve blocks is increasing, and epidural block has also given new content. 1. Anatomical and Blocked Nerves The anatomy of the spine and spinal canal varies considerably from segment to segment. The ligaments in the lumbosacral segment are well developed, and become weaker as they go up. Closely related to epidural puncture are the supraspinous ligament, interspinous ligament, sacrospinal aponeurosis, intertransverse ligament, and ligamentum flavum. The intertransverse ligament is absent in the neck, cord-like in the chest, and membranous in the waist. The spinal nerves in the spinal canal mainly have anterior and posterior roots. The anterior root is the thicker motor nerve, and the posterior root is the sensory nerve, including the body surface sensory nerve, sympathetic nerve, sacral parasympathetic nerve, and all visceral sensory nerves except the vagus nerve. The nerves that can be blocked by an epidural block are the anterior and posterior roots of the spinal nerves. The former is a motor nerve, which produces muscle relaxation; the latter includes surface sensory afferents, sympathetic preganglionic fibers, part of visceral sensory afferents, and sacral parasympathetic afferents. 2. Epidural success rate Over the years, anesthesiologists in some hospitals have been troubled by the failure rate of epidural punctures when they perform epidural blocks. In general, epidural puncture should be successful unless there is severe ossification of the ligamentum flavum. There are no more than two methods for epidural puncture: one is to puncture the ligamentum flavum with a "breakthrough" by holding a needle, and the saline syringe can be easily injected into the epidural space; After puncturing the ligamentum flavum, connect the saline syringe and pressurize it. If the injection is blocked, continue to pressurize. At the same time, the needle is advanced, and the saline is suddenly and easily injected, indicating that it has entered the epidural space. Obviously, the former has a certain failure rate because: the needle tip does not touch the ligamentum flavum, and saline can be easily injected into the soft tissue, and piercing the ligamentum flavum does not necessarily have an obvious "breakthrough"; The ligaments are thin, and there is a "breakthrough" after puncturing, which often gives the puncture an illusion. The second method is a process of pressurizing the syringe—saline cannot be injected under continuous pressure—advance the needle—saline is suddenly and easily injected. As long as the needle does not enter the ligamentum flavum, pressurizing the syringe cannot maintain the pressure in the syringe. Pressure, the ligamentum flavum is thick, and saline cannot be injected after the needle enters the ligamentum flavum. After breaking through the ligamentum flavum and entering the epidural space, saline can be easily injected. The success rate of epidural puncture can reach 100 percent . Although the sacrospinal aponeurosis and the intertransverse ligament are punctured, there is a "breakthrough", but the two are weak, and the needle bevel cannot be completely buried in them, so it is impossible to maintain the pressure by pressurizing the saline in the syringe. 3. Epidural block medication Lidocaine and tetracaine mixtures have played a huge role in clinical anesthesia for many years and are still used in many hospitals today. In recent years, the use of 0.25 percent -0.375 percent bupivacaine in the upper thoracic segment and 0.5 percent -0.75 percent bupivacaine in the lower thoracic, abdominal, and lumbar epidural block is more common. It is characterized by wide block plane and exact muscle relaxation. The previously controversial cardiotoxicity does not occur frequently. From the point of view of clinical effect and economy, bupivacaine has great value. Injection method: should be individualized. The test dose is generally the dose of spinal anesthesia. After confirming that the catheter has not entered the subarachnoid space, the additional dose of local anesthetic should be larger. In the past, 3-5ml is likely to cause incomplete muscle relaxation, because the supine anterior root motor is higher and the epidural space is high. In large patients, a small volume of local anesthetic spreads quickly to the head and tail, and it is not easy to block the higher anterior root. Taking 0.5 percent bupivacaine as an example, the test dose (spinal anesthesia dose) is 3ml, 7ml and 10ml. Re-injection of normal saline 5-10ml can further spread the block plane. Ropivacaine, lidocaine carbonate, etc. are expensive, and have no advantage in terms of efficacy and toxicity. 4. Incomplete epidural block, poor muscle relaxation, and lateral block are these problems that often trouble anesthesiologists in clinical practice. Multiple epidural punctures may lead to epidural adhesions and limited diffusion of the local anesthetic, resulting in incomplete block. The catheter can be pulled out a little and then injected with local anesthesia. The main reasons for poor muscle relaxation are: when the patient is in the supine position, the anterior heel (motor branch) of the spinal nerve is high, the posterior root (sensory branch) is low, and the epidural space is large. When the local anesthetic is less, it can spread to the horizontal position, and the sensory nerves are easily blocked but the motor nerves are not blocked, resulting in no pain but poor muscle relaxation. The amount of local anesthetic injected can be increased or the arcuate position can be given. If the epidural catheter is inserted too deep, it can be pierced through the intervertebral foramen. The injection of local anesthetic will block one spinal nerve. If the blocking effect is lateral, the catheter can be pulled out 1-2 cm, and then the local anesthetic can be injected. 5. Epidural block and expansion of blood volume The maintenance of arterial blood pressure mainly depends on the tension generated by cardiac pumping, blood volume and the action of sympathetic vasoconstrictor nerves on the arterial wall. The preganglionic fibers of the sympathetic nerve are located in the dorsal root of the spinal nerve, and local anesthetics for epidural block can simultaneously block the sympathetic nerve and dilate the arteries, resulting in relative hypovolemia. From thoracic 1 to lumbar 3, there are sympathetic nerves and sensory nerves parallel to the posterior root. According to the range of sensory nerve blockade, it can be known which segments are blocked. During chest 1 to chest 6 block, the blood vessels in the heart and lung are not greatly affected by sympathetic nerves, only the skin and muscle blood vessels are dilated, so the upper thoracic epidural block during upper limb, lung and breast surgery does not need to be expanded; During epidural block where the stagnation plane is below thoracic 6, the arteries and blood vessels of abdominal organs are greatly affected by sympathetic nerves and must be expanded, especially for patients with preoperative fasting and preparation of gastrointestinal tract, such as gastrointestinal tract, during epidural injection Should be expanded, 20-30ml/Kg is recommended (1 crystal: 2 colloid). After the block has subsided, it is necessary to prevent excessive volume from increasing the burden on the heart. 6. Epidural block and visceral sensory It is well known that part of the conduction of visceral sensory nerves joins spinal nerves together with autonomic nerves, and epidural can block this part of nerves. A large part is parallel to the vagus nerve, and epidural blocks are not available, so many abdominal surgery visceral pain epidural blocks cannot be satisfied. This is why clinically the anesthesia level is good, but the internal organs are painfully stretched. General anesthesia has a good effect on visceral pain. The traditional fluorine mixture is effective, but not exact. Small doses of chloramine ketone or propofol are more effective. 7. Potential dangers of epidural blocks and sympathetic tone Epidural blocks block sympathetic preganglionic fibers and sacral parasympathetic nerves, but have no effect on the vagus nerve. There is a huge potential risk of causing temporary autonomic tension imbalance, especially epidural blocks with a wide block plane. Especially in the heart, lungs, blood vessels, etc. When the blocking plane reaches the chest 1-4, the cardiac sympathetic nerve is blocked, and the parasympathetic nerve (vagus) tension is relatively large, which is manifested as a slowing of the heart rate. At this time, atropine can only reduce vagal tension, and its effect on increasing heart rate is often not obvious. Drugs that directly excite the sinus node, such as ephedrine and isoproterenol, are used. Sympathetic-parasympathetic imbalance in arterial vessels manifests as relative hypovolemia, which must be expanded. You must be in a supine position when you pass the bed after surgery. Postural changes, severe coughing, and vomiting can lead to further increases in parasympathetic tone, severe hypotension or slowed heartbeat, or even cessation. Clinically, many epidural block accidents occurred at this time. 8. The status of epidural block in combined anesthesia It has been debated for a long time who should be the main player in epidural block combined with general anesthesia. Currently, it is widely accepted that shallow general anesthesia should be used as far as possible under the premise of patient tolerance to the endotracheal tube. Therefore, epidural block should be dominant in epidural block combined with general anesthesia. Epidural block combined with intravenous anesthesia is currently the most used anesthesia method. Epidural block is the main method, and the role of intravenous general anesthesia is to eliminate visceral pain, relieve the tension of the patient, and make the patient fall asleep.

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