What Is Regional Analgesia?

Patient controlled analgesia (PCA) is a kind of pain management technology that is set by the medical staff in advance according to the patient's pain level and physical condition, and then sets the dose of analgesic drugs, which is then "self-managed" by the patient.

Patient controlled analgesia

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Patient controlled analgesia (PCA) is a kind of pain management technology that is set by the medical staff in advance according to the patient's pain level and physical condition, and then sets the dose of analgesic drugs, which is then "self-managed" by the patient.

Chinese name

Patient controlled analgesia

Foreign name

Patient controlled analgesia

Short name

PCA

Category

Analgesic

Purpose

Alleviate patient suffering

Advantages

Good analgesic effect

Patient controlled analgesia (PCA) is a kind of pain management technology that is set by the medical staff in advance according to the patient's pain level and physical condition, and then sets the dose of analgesic drugs, which is then "self-managed" by the patient.

PCA is a new type of analgesic drug delivery device. The patient wears an infusion control device. When he realizes the pain, he injects an analgesic drug into the body through the controller to achieve the purpose of pain relief. PCA is a better method for modern pain treatment and an important method for postoperative pain treatment.

Compared with traditional intramuscular analgesics, PCA has obvious advantages:

During the analgesic treatment, the peak blood concentration of the analgesic drug is low, the fluctuation of the blood concentration is small, the incidence of respiratory depression is low, and the side effects of excessive sedation during the analgesic treatment are reduced;
Good analgesic effect;
PCA can overcome the individual differences in pharmacokinetics and pharmacodynamics of analgesics and achieve on-demand administration;
Reduce the time waiting for medical staff to deal with patients' pain;
reduce the incidence of postoperative complications;
Improve the satisfaction rate of patients and their families with medical quality;
Reduce the workload of medical staff.

Loading dose: Loading dose (LD) refers to the first dose of PCA when PCA is started. The purpose of the load is to allow the patient to quickly reach the minimum effective analgesic concentration (MEAC) required for analgesia, allowing the patient to quickly eliminate pain. The load is usually administered by a medical staff. The injection rate of the load needs to be controlled to avoid too high a rapid injection concentration and transient blood concentration. The LD and LD pumping speed of a drug are determined by its pharmacological properties. The calculation formula is as follows: load amount = minimum effective analgesic concentration × initial distribution volume.

Single administration dose: The single administration dose (Bolus) refers to the additional drug dose when the patient's pain does not disappear or the pain recurs. The purpose is to maintain a certain blood concentration without excessive sedation. Bolus is the primary means by which PCA overcomes individual differences in analgesics. Depending on the degree of pain and the patient's sedation, adjust the dose of 25-50% each time. Bolus increases the blood drug concentration by the Bolus dose divided by the initial volume of drug distribution. Bolus size is one of the important parameters that determines the effectiveness of PCA pain treatment. If the dose of Bolus is too high, the blood concentration is too high, and the chance of side effects will increase; if the dose is too small, the number of medications will be increased, and the patient's compliance with PCA will be reduced.

(3) Lockout time: Lockout time (LT) refers to the interval between two single doses of the PCA device. Lock time is one of the security protection methods of PCA. The purpose of the lock time is to prevent re-administration of patients who have not responded to the previous single dose, and to prevent overdose poisoning. The lock time is determined by the onset speed of the drug and the route of PCA administration. The time it takes for the responding drug to reach a sufficient analgesic concentration at the site of action. For example, the locking time for patient-controlled analgesia in morphine vein patients is usually 5-15 minutes, and the locking time for patient-controlled analgesia in epidural patients is 10-30 minutes.

Continuous infusion rate: The purpose of continuous infusion rate or background infusion rate is to maintain a relatively stable blood concentration and reduce the number of medication orders. The steady-state blood drug concentration at a constant rate infusion is equal to the pumping rate divided by the drug clearance rate. The theoretical minimum pumping rate of PCA is equal to the product of CI and MEAC.

Maximum dosage: Maximum dosage is another safety protection device of PCA. There are 1-hour limit and 4-hour limit. The purpose is to draw attention to and limit situations that exceed the average dose. The setting of the maximum dose should vary from person to person. Such as morphine 0.4-5.25mg.h-1, fentanyl 0.15-0.18mg.h-1.

According to the patient's condition and the preferences of the medical staff, the PCA administration modes are divided into:

PCA alone: The patient is completely self-controlled. When the patient is in pain, the PCA control device is pressed and a single dose is given.

Background infusion + single dose: based on continuous infusion of a certain drug, the patient increases a single dose in pain;

(3) Load amount + background infusion + single dose: when the patient is in pain, first give a load to the patient to quickly eliminate the pain, and then continuously inject a certain drug, and the patient will increase a single dose when the pain;

Continuous infusion rate: Infusion of drugs at a constant rate, not PCA in the true sense, can only be considered as a way of administering analgesics.

According to the different administration routes of PCA, it can be divided into: epidural patient-controlled analgesia, intravenous patient-controlled analgesia, nerve plexus patient-controlled analgesia, and subcutaneous patient-controlled analgesia.

Epidural patient-controlled analgesia: Patient controlled epidural analgesia (PCEA) is a drug used in the epidural space using a PCA device. It is mainly used for the treatment of pain in the back of the chest and below. . PCEA has exact analgesic effects and relatively few side effects. Local anesthetics or opioid analgesics are commonly used. The combination of local anesthetics and opioid analgesics (balanced analgesia) can reduce the dosage of each drug, reduce the side effects of the drug, and better inhibit the metabolic and endocrine reactions caused by noxious stimuli. Common PCEA schemes are shown in Table 2-3.
Table 2-3 Commonly used PCEA medication regimen The University of Kentucky Xiangya Hospital Ogawa drug Morphine or (and) bupivacaine fentanyl and bupivacaine buprenorphine 2-3 mg 30-50 g 0.1-0.2 mg
Single dose 0.2 mg 10-30 g 0.05-0.1 mg
Continuous speed 0.4 mg.h-1 15-20g.h-1 0.01-0.02 mg
Lock time 10 min 10-15 min 45-60 min
Note: The doses listed in the table are all narcotic analgesics. Patient-controlled intravenous analgesia: Patient controlled intravenous analgesia (PCIA) is a PCA device administered intravenously, which is easy to operate and widely used , Including narcotic analgesics and non-steroidal analgesics. PCIA has a fast onset of action and a wide range of applications, but it is a systemic drug with high side effects and analgesic effect is inferior to epidural patient-controlled analgesia. When using narcotic analgesics, PCIA has a higher incidence of respiratory depression if background infusion is used. Therefore, this method generally does not require background infusion and only uses a single dose. Common PCIA drugs are shown in Table 2-4.
Table 2-4 PCIA commonly used drugs and parameter settings Drug drug concentration (mg.ml-1) Single dose (mg) Lock time (min)
Morphine 1 0.5-2.0 5-10
Pethidine 10 5-25 5-10
Fentanyl 0.01 0.01-0.02 3-10
Sufentanil 0.002 0.002-0.005 3-10
Alfentanil 0.1 0.1-0.2 5-8
Ketolola LD = 20mg continuous = 4mg.h-1 2 5

(3) Patient-controlled analgesia of nerve plexus: Patient controlled nerve analgesia (PCNA) of nerve plexus is to use PCA device to treat peripheral pain in nerve plexus or peripheral nerve. Commonly used drugs are local anesthetics bupivacaine and ropicaine. You can add an appropriate amount of narcotic analgesics to local anesthetics. For brachial plexus block, 0.125% bupivacaine can be used. PCNA parameters are set as follows: background infusion rate 3-5ml.h-1, single dose 3-5ml, lock time 30-40 minutes, maximum dose 10-15ml .h-1, used for analgesia after upper limb surgery can achieve satisfactory pain results, and this method blocks sympathetic nerves, expands upper limb blood vessels, and can increase the success rate of replantation of severed limbs (broken fingers).

Percutaneous patient-controlled analgesia: Patient controlled subcutaneous analgesia (PCSA) is a subcutaneous analgesia using a PCA device. PCSA has its advantages in patients with difficult venipuncture and patients who need PCA for a long time. It can avoid complications caused by other PCA methods of puncture and catheter indwelling. Compared with PCIA, its analgesic effect and side effects are similar. Commonly used drugs are morphine, buprenorphine, and ketamine. Pethidine has tissue irritation and is not suitable for PCSA. The 22G trocar outer sleeve is usually placed under the local anesthesia at the forearm near the elbow joint, and the PCA device is connected. If morphine is used, the parameters are generally set as follows: the concentration is 5mg.ml-1, and the patient administers 2.5ml per compression. (Morphine 2.5mg), lock time 20 minutes.

PCA is an ideal way to use analgesics, which can individualize analgesics and has a wide range of clinical applications, mainly including the following aspects:

Treatment of postoperative acute pain.

Labor analgesia: Drugs and methods used in obstetric analgesia require harmless to the mother, do not affect the blood flow and contraction of the uterus, and have no effect on the respiratory cycle of the fetus and newborn. Therefore, PCEA is generally used for labor analgesia. Clinically, a mixture of 0.0625% -0.125% bupivacaine plus 2 g.ml-1 fentanyl is used to control the level of anesthesia below 10 levels of the chest. Give a load of about 5ml. After measuring the level of anesthesia, set the background speed to 5ml.h-1, a single dose of 3-5ml, and a lock time of 10-20 minutes. Adjust the dosage of the drug according to the analgesic effect. Pain effect.

(3) Cancer pain treatment: Cancer pain is generally treated according to the WHO three-step analgesic regimen. PCA for cancer pain is one of the last three steps of treatment, and it is suitable for patients with cancer pain who have failed oral morphine. The PCA method mostly uses morphine for PCEA or PCSA. The specific regimen should be determined according to the degree of pain of the patient, the patient's tolerance to narcotic analgesics, and the general state of the patient's body.

Treatment of burn pain: PCIA is mostly used in burn patients. The treatment of burn wounds and dressing changes will increase the degree of pain, and a loading dose should be increased before the operation to reduce pain. Patients with large-area burns generally have complex conditions and change rapidly, and the PCIA protocol should be adjusted in a timely manner.

Treatment of patients with internal medicine pain: It is often used in the treatment of angina pectoris, chest pain caused by myocardial infarction, and sickle cell crisis.

Treatment of traumatic pain: Traumas such as car accidents and trauma often cause patients to be in extreme pain, and patients' pain should be actively controlled under a clear diagnosis of the patient. It can reduce the stress response caused by trauma, encourage patients to cooperate with medical staff, and facilitate examination and treatment.

Pain treatment for pediatric patients.

Other acute pain treatment: PCA can also be used for acute onset of lower back pain, neuralgia, etc. ^[1]