I. Local anesthetic drugs Local anesthetics can treat postoperative analgesia through local infiltration of surgical incision, single or continuous block of regional plexus and peripheral nerve trunk, and single or continuous block method in the spinal canal. 1, postoperative analgesia commonly used local anesthetics and characteristics Bupivacaine: is a slow-acting, long-acting amide local anesthetic, mainly used for infiltration anesthesia, peripheral nerve block and intravertebral block. Levobupivacaine: the efficacy of bupivacaine is comparable to that of bupivacaine, the use, the use of the same dose, but less toxic side effects. Ropivacaine: It is an amide-type local anesthetic with similar onset and maintenance time as bupivacaine, but the motor nerve block is lighter and shorter in duration and weaker in intensity. The recommended maximum dosage of the above local anesthetics is shown in Table 5. 2. Postoperative analgesic methods of local anesthetics A. Local infiltration: simple and easy, applicable to all kinds of surgery. Long-acting local anesthetic infiltration is injected subcutaneously into the incision before the surgical suture. Can also be local incision subcutaneous buried tube after continuous pumping of local anesthetics. B. Peripheral nerve block: It is suitable for postoperative analgesia in the area innervated by the corresponding nerve plexus or nerve trunk, such as intercostal nerve block, upper limb nerve block (brachial plexus), paravertebral nerve block, and lower limb nerve block. However, attention should be paid to problems such as displacement and dislodgement of the indwelling tube, and bruising of the patient after motor block. C. Epidural drug delivery: Continuous drug delivery through the epidural catheter placed through the sacral fissure or interspinous. It is suitable for thoracic, abdominal and lower extremity surgery. The advantage is that it does not affect the sanity and observation of the condition, and does not affect motor and other sensory functions. The addition of opioids to local anesthetics can not only achieve the synergistic effect of analgesia, but also reduce the side effects of both types of drugs and mitigate the occurrence of motor block, which is the most commonly used combination. It is suitable for moderate to severe postoperative pain. Local anesthetics such as low-concentration ropivacaine or bupivacaine are commonly used in combination with fentanyl, sufentanil, morphine, bupropion and other drugs. (Table 6) Post-epidural analgesia (PCEA) is recognized as the best postoperative analgesic method today, but there are still complications and it should be used after a thorough assessment of the patient, especially the patient’s pain threshold sensitivity and previous drug use. Opioids and tramadol Opioids are the most widely used potent analgesics, and the drugs used for postoperative analgesia are morphine, fentanyl and sufentanil. 1. Commonly used opioids A. Morphine: the most widely used opioid, can be taken subcutaneously, orally, epidurally, intrathecally, intramuscularly, intravenously, transrectally and so on. Dosage recommendation ① Oral neonatal: 80μg/(kg? 4-6h); children: 200-500μg(/kg? 4h) ② Intravenous and subcutaneous Starting dose (titrated according to the response) Single dose: 25μg/kg for neonates; 50μg/kg for children Continuous infusion: 10-40μg/(kg? h) ③ Patient-controlled analgesia (PCA) Shock dose. 10～20μg/kg, lock time: 5～10min, background dose: 0～4μg/(kg? h) ④ Nurse-controlled analgesia (NCA) Shock dose: 10～20μg/kg, lock time: 20～30min, background dose: 0～20μg/kg? h (not used for less than 5kg). B. Hydromorphone: It is a strong opioid analgesic with lighter side effects than morphine, and is widely used for pediatric postoperative analgesia and chronic pain treatment. Dose recommendation: ① oral: 40-80μg/(kg?4h) ② intravenous and subcutaneous starting dose (according to the response titration): single dose: weight <50kg: 10-20μg/kg starting continuous infusion: 2-8μg/(kg?h) C. Diacetylmorphine: more potent than morphine, higher fat solubility, faster onset and longer duration opioid analgesic, can be It can be administered subcutaneously, orally, epidurally, intrathecally, intramuscularly, intravenously, etc. Dose recommendation: ① Oral: Age >1 year: 100-200μg/(kg?4h) ② Intravenous and subcutaneous starting dose (titrated according to the response): Single dose: Neonatal: 10-25μg/kg to start; Children: 25-100μg/kg to start Continuous infusion: 2.5-25μg/(kg?h) ③ Intranasal: 100μg/kg mixed with 0.2ml sterile saline ml of sterile saline into one nasal cavity. D. Codeine and dihydrocodeine: weaker effect than morphine, commonly used in the treatment of mild to moderate pain and in combination with NSAID or p-acetaminophen. They can be administered orally, intramuscularly or rectally, but not intravenously, as this can produce severe hypotension. Dose recommendation ① Codeine: oral, intramuscular injection or rectal administration 0.5-1 mg/(kg?4-6h) (high caution is required for repeated use in neonates) ② Dihydrocodeine: oral, intramuscular injection Age > 1 year: 0.5-1 mg/(kg?4-6h) E. Fentanyl: a strong analgesic, more lipophilic than morphine, with faster onset and shorter duration of action because of its lipophilic nature. It can be used through the skin and mucous membrane. It can be administered in small doses for analgesia after surgery. The use of neonates should be closely monitored. Dose recommendation: ① Single intravenous injection: 0.5-1.0μg/kg, titrated according to the analgesic effect, reduced in neonates ② Continuous intravenous injection: 0.5-2.5μg/(kg? h) ③ Transdermal administration: 12.5-100μg/h ④ PCA: loading dose: 0.5-1.0μg/kg; background dose: 0.15μg/(kg? h); single shock dose. 0.25ug/kg; lock time 20min; maximum dose: 1~2μg/(kg? h) F. Sufentanil: 7~10 times stronger than fentanyl analgesic effect. It has higher lipid solubility than fentanyl, and can easily cross the blood-brain barrier, with rapid onset of action. Neonatal liver enzyme system is immature, and clearance is greatly influenced by hepatic blood flow (PACU analgesia is particularly good). Dose recommendation: ① single intravenous injection: 0.05-0.1μg/kg, titrated according to analgesic effect ② continuous intravenous infusion: 0.02-0.05μg/(kg? h) ③ PCA: loading dose: 0.05-0.1μg/kg; background dose: 0.03-0.04μg/(kg? h); single shock dose: 0.01μg/kg; lock time 15min; maximum dose: 0.1~0.2μg/(kg? h). When preparing, to prepare at 1.5 to 2μg/kg in 100ml liquid, use 48 hours, background infusion is 2ml/h, single impact dose is 0.5ml. Note: Toxic side effects of opioid drugs Opioid drugs can cause various effects such as nausea and vomiting, pruritus, urinary retention, respiratory depression in various systems of the body. Adverse drug reactions vary in each patient subject to genetic and developmental influences. Therefore, children with postoperative analgesia on such drugs should be appropriately monitored and prepared for the management of adverse reactions. The combined use of non-opioid analgesic drugs can reduce the dose of opioid drugs and the corresponding serious adverse reactions. 2. Tramadol Tramadol is a weak opioid analgesic acting through 5hydroxytryptamine and norepinephrine, which can be administered orally, intravenously, rectally, by continuous infusion, and also as part of PCA. Common side effects include nausea and vomiting, respiratory depression (less common than opioids), excessive sedation and urinary and fecal retention, and seizure-like convulsions can occur with tramadol overdose. Dose recommendation: oral, rectal or intravenous administration: 1 to 2 mg/(kg?4 to 6 h) 3. Comparison of relative efficacy and intravenous continuous infusion doses of opioids (Table 7) 4. Common methods of opioids A. Patient-controlled analgesia (PCA): for children over 5 years of age. Patient-controlled intravenous analgesia (PCIA) is considered to be the best way to administer opioids. The addition of certain doses of anti-emetic drugs such as granisetron to analgesic drugs can prevent the adverse effects of opioids such as nausea and vomiting to a certain extent. The recommended regimen for pediatric self-administered intravenous analgesia (PCIA) is shown in Table 8. B. Nurse- or parent-controlled analgesia (NCA): For children younger than 5 years of age and those who cannot cooperate. Caution: The process of pump withdrawal should be individualized for both PCA and NCA, and the child’s use of PCA should be significantly reduced and the pain score should be low enough to consider pump withdrawal. Non-steroidal anti-inflammatory drugs (NSAID) can be used to maintain analgesia after pump withdrawal. Third, non-steroidal anti-inflammatory drugs (NSAIDs) The effectiveness, especially the safety, of NSAIDs in children has not been systematically verified, so they are not approved for use in children, but there are a large number of reports of NSAIDs-like drugs used for pain treatment in children both at home and abroad, but they are generally not recommended as analgesic drugs for infants under 3 months of age. Aspirin may cause Rael’s syndrome and is not used in children. Ibuprofen is the NSAIDs drug that causes the fewest side effects and has the most evidence for safe use followed by diclofenac and celecoxib, and flurbiprofen ester and parecoxib sodium have both been clinically reported for use in postoperative pediatric analgesia (Table 9). Fourth, acetaminophen can be used as a basic medication for almost all types of postoperative pain due to its low toxic side effects and regular medication at regular intervals. acetaminophen analgesia can be used alone for mild pain and combined with NSAIDs or weak opioids such as codeine for moderate pain. Generally, the drug concentration peaks after 30-60 min of oral administration, and it takes 1~2.5 h to reach the maximum blood concentration after rectal administration; intravenous administration is fast-acting but needs to be input slowly within 15 min. The drug is metabolized in the liver, and the clearance of the drug is low in newborns because of the immaturity of certain enzymes in the liver, while in children aged 2-6 years, the drug is metabolized rapidly because of the relative proportion of the liver. Table 10 lists the recommended doses of acetaminophen for oral and direct soap opera administration, and Table 11 lists the recommended doses of acetaminophen for intravenous administration. V. Multimodal analgesia Commonly used pediatric multimodal analgesic methods include (1) combination of NSAIDS and other drugs such as opioids; (2) combination of local anesthetics with opioids or other types of analgesics; (3) combination of peripheral and central drugs; (4) combination of different analgesic modalities; (5) combination of over-the-counter analgesia and postoperative analgesia.