Intraspinal anesthesia, also known as "lower body anesthesia". Professional anesthesia refers to the injection of local anesthetic drugs and/or adjunctive drugs into the subarachnoid or epidural space of the spinal canal, blocking the transmission of pain and nociceptive stimuli by the spinal nerve root, and inducing anesthesia in the corresponding area innervated by the nerve root, collectively known as intraspinal anesthesia. According to the location of drug injection, it can be divided into subarachnoid anesthesia (also known as spinal or lumbar anesthesia), epidural block, lumbar epidural combined anesthesia, and sacral block anesthesia.
Due to differences in the infiltration of anesthetics by different nerves, the onset time of nerve fiber blockade varies. The sequence of nerve block anesthesia is usually: sympathetic nerve → cold sensation → temperature sensation → temperature recognition sensation → dull pain sensation → sharp pain sensation → touch sensation → motor nerve (muscle relaxation) → disappearance of proprioceptive sensation. Therefore, patients usually feel a "fever" in the lower limbs or buttocks "at the earliest" after anesthesia, and then numbness, pain, and movement disappear until proprioception disappears (i.e. they cannot feel the presence of the lower limbs). Doctors will ask patients about their different feelings during the anesthesia process at different time points to determine the anesthesia effect, which also requires active cooperation from patients in order to optimize the anesthesia effect.
In addition to pain relief, other spinal anesthesia effects may cause some discomfort to the body. Modern anesthesia monitoring technology is very advanced and will not miss any abnormal changes. At the same time, anesthesiologists will handle them in a timely manner, and some normal "abnormal" reactions will also disappear synchronously after the anesthesia effect disappears.
Due to the blockade of the sympathetic nervous system, the small arteries in the blocked nerve innervation area dilate, resulting in a decrease in peripheral vascular resistance; Venous dilation leads to a decrease in cardiac output, resulting in hypotension. The subjective feeling of the patient is that there is no strength, and the occurrence and magnitude of hypotension are closely related to the size of the blockage range, the patient's overall condition, and the body's compensatory ability. It should be emphasized that hypertensive patients should not take antihypertensive drugs outside of medical advice to avoid the occurrence of stubborn hypotension.
The impact of spinal anesthesia on respiratory function mainly depends on the extent and degree of blockage of abdominal muscles, intercostal muscles, and diaphragm. When most or all of the paralysis has varying degrees of impact on lung ventilation function, patients may feel "struggling to breathe out and insufficient gas". At this time, doctors will perform "nasal mask oxygen therapy" to increase oxygen supply and prevent hypoxia. The feeling of weak breathing will recover after the anesthetic effect disappears.
During spinal anesthesia, the sympathetic nervous system is blocked, the function of the vagus nerve is relatively overactive, gastrointestinal peristalsis is enhanced, and patients may feel nausea, and in severe cases, vomiting. At the same time, surgical traction of the abdominal organs or a decrease in blood pressure, or respiratory fatigue and hypoxia, combined with other factors, can stimulate the vomiting center and cause nausea and vomiting. At this time, the anesthesiologist will administer antiemetic drugs to treat possible causes, such as hypertension, oxygen inhalation, and fluid supplementation.
Headache is a common adverse reaction that may occur after anesthesia surgery, mainly due to anesthesia affecting the circulation of cerebrospinal fluid. Headaches often occur 6-24 hours after anesthesia, with the most severe symptoms occurring 2-3 days later. They generally disappear within 7-14 days, and in some patients, they can last for 1-5 months, but almost all can recover. The preventive measure is for patients to lie flat without pillows for 6-8 hours during anesthesia and after surgery. Mild headaches can disappear on their own after 2-3 days of lying flat. Moderate fluid replacement, caffeine consumption, or low-dose analgesics and sedatives can be used.
Patients undergoing spinal anesthesia generally choose a lateral or sitting position (saddle block), with their back perpendicular to the bed surface and level with the edge of the bed. They should bend their waist backwards as much as possible, resembling an "arched back", to open the gap between the spinous processes for puncture. Firstly, the anesthesiologist will apply pressure (feeling a bit painful or uncomfortable) and touch the patient's spine to locate the puncture point, then disinfect the skin, which will feel a bit cool; There is some pain during puncture, and the patient may feel a piercing sensation when the anesthesia puncture needle passes through each layer of tissue, but don't be nervous. After successful injection of local anesthetics through puncture, anesthesiologists often use "skin pain test" or "cold saline cotton swab" to test the anesthesia block level. Block plane regulation is the most important part of spinal canal block anesthesia, so anesthesiologists require patients to "cooperate" in accurately and quickly measuring the sensory plane to achieve the best anesthesia effect.