So-called patient-controlled analgesia (“PCA”) is a modern form of analgesic application based on dosing by the patient himself. The terms “PCA pump” and the colloquial term “pain pump” refer to the same procedure. The PCA enables the patient to administer pain medication individually, adapted to his or her needs, at the touch of a button, without the intervention of the physician or nursing staff. Advantages of this procedure include a reduction in the time to onset of pain relief, greater autonomy with good controllability, and a reduced risk of over- or under-dosing and lower fluctuations in plasma drug levels (concentration of analgesics in the blood). The most common use of PCA is via intravenous administration of opioids (analgesic class to which morphine belongs). There are also options for patient-controlled epidural anesthesia (PCEA), regional spinal anesthesia (PCRA), and the noninvasive method of transdermal (through the skin) PCA. These forms of PCA are discussed below.
Indications (areas of application)
- Postoperative pain therapy – especially after very painful procedures.
- Chronic pain syndromes
- Palliative pain management
- Tumor pain therapy
Contraindications
i. v. PCA
- Hypovolemia (volume deficiency)
- Circulatory instability
- Severe respiratory insufficiency – insufficient function of the respiratory system with inadequate supply of oxygen to the body.
Other contraindications
- Addiction history
- Suicidality (risk of suicide)
- Vigilance disorder – disturbance of consciousness.
- Limited ability to cooperate – patients with unavailable mental comprehension, infants under four years, patients suffering from dementia.
Before surgery
Before the procedure, a detailed medical history must be taken and the patient must be informed about possible complications. The use of the pain pump must be explained to the patient in detail, since its use without complications relies on adequate understanding by the patient.If the pain pump is planned for postoperative pain management, the patient must be informed separately about the procedure and the pain pump preoperatively. When an epidural PCA pump is placed, surgery precedes or is placed during surgery. Consequently, operation-specific preparations should be made, i.e., for example, platelet aggregation inhibitors (blood-thinning medications) must be discontinued approximately 5 days before the operation. This must be checked with the help of a blood test (coagulation parameters). Furthermore, it is recommended that the patient stop nicotine consumption to support wound healing.
The procedure
Patient-controlled analgesia is based on the following principle: a so-called bolus (i.e., administration of the drug within a short time interval to quickly achieve a high level of effect or a rapid onset) of an analgesic (e.g., an opioid or a local anesthetic) is injected by pressing the bolus button by the patient via an electrically controlled pump. Prior to this, the treating anesthesiologist determines the amount of the bolus. He also determines a so-called blocking interval, i.e. a period during which no further bolus can be delivered. In addition, a safety limit is set in the form of a maximum dose. Optionally, this concept can be based on a basal rate (basal dose of the analgesic). The patient can therefore apply the analgesic according to his or her needs, but without the possibility of overdosing. When opioids are administered, a decrease in vigilance (diminished consciousness) sets in quite quickly, so that the patient would no longer be able to administer further medication to himself. This additional protective mechanism also prevents overdose with potential side effects, such as respiratory depression. The use of PCA must be monitored by a physician who is available 24 hours. Strict care must be taken to ensure that the bolus button is not actuated by nursing staff or relatives, as there is a risk of complications in such a case.If PCA is used postoperatively, the setting of the pain pump and the patient’s pain level must be checked and documented before the patient is transferred from the recovery room to the ward. A PCA pump consists of the following technical components:
- Microprocessor – This microprocessor is programmable via a keypad and is connected to a mechanical delivery apparatus for pharmaceutical application.
- Pharmaceutical reservoir – The pharmaceutical reservoir is a lockable chamber that prevents unauthorized removal of the drugs, since, for example, opioids fall under the Narcotics Protection Act and may not be stored freely accessible.
- Bolus button – The bolus button is the element that is pressed by the patient to request analgesic administration.
- Infusion line – Line system that is matched to the pump and connected to, for example, an intravenous indwelling cannula.
- Power supply – Consisting of power supply and battery or accumulator.
- PC connection – This is used to transfer and store the protocol of use, or programming of certain infusion protocols. The statistics thus created can help optimize the therapy plan.
Different application sites or forms of PCA allow a very individualized creation of the pain therapy concept:
- Intravenous PCA – Opioids are administered systemically via an intravenous indwelling cannula. This procedure is commonly used in postoperative pain management.
- Epidural or spinal – In patient-controlled epidural analgesia (PCEA), a local anesthetic with or without an opioid is applied continuously via a pump. This basal rate can be supplemented by the patient’s boluses. The advantage of this procedure is reduced patient vigilance disturbance.
- Peripheral nerve blocks – Patient-controlled regional anesthesia (PCRA) is similar to PCEA, except that the location varies.
- Noninvasive transdermal PCA – Using a technique called transdermal iontopheresis (a physical process that uses a weak direct current to deliver a drug through the skin), the opioid fentanyl can be administered through the skin. Through a small electronic system that is glued to the skin, the active ingredient can be released, also at the touch of a button.
After the operation
After any surgery, close monitoring of the patient is necessary. In addition to surgical follow-up, the patient must also be closely monitored by anesthesia staff to detect potential complications early. Intensive patient monitoring is especially necessary for PCEA and PCRA.
Potential complications
i. v. PCA (opioids).
- Respiratory depression
- Nausea (sickness)
- Pruritus (itching)
- Sedation (anesthesia)
- Urine retention (urinary retention)
PCEA (local anesthetics ± opioids).
- Epidural hematoma – hematoma in the epidural space (site of analgesic application) with compression of the spinal cord.
- Epidural abscess – inflammatory process in the epidural space.
- Hypotension (too low blood pressure)
- Intoxication with local anesthetic
- Nausea (nausea)
- Pruritus (itching)
- Delayed respiratory depression