Patient-Controlled Analgesia (PCA) has become an acceptable and highly effective means of relieving post-operative pain. PCA is a medication-dispensing unit equipped with a pump attached to an intravenous line, which is inserted into a blood vessel in the patient's hand or arm (Figure III-59). By means of a simple push button mechanism, the patient is allowed to self-administer doses of pain relieving medication (narcotic) on an 'as need' basis. Prior to release from the hospital, the patient is weaned from the PCA and given oral medication to control pain. Before surgery, the anesthesiologist and/or doctor will discuss postoperative pain and how it can be controlled. Patients who are given options feel more confident, comfortable, and reassured about their surgical outcomes.
Patient-controlled analgesia is a technique of parenteral drug administration in which the patient controls a pump that delivers bolus doses of an analgesic, delivery rate and the physician presets a lock-out time. Use of a patient-controlled analgesia device allows the patient to titrate the opioid dose to his/her individual needs. The rational for use of such a pump is the fact that every patient has a different level of pain intensity and need of analgesics in the postoperative period. Fixed amounts of opioids often result in under- or even an overdose of the narcotic analgesic. Since the patient by himself is more able to tell when he needs a drug for alleviation of pain, the technique of "patient-controlled analgesia" seems a rational approach in order to have a content and pain-free individual. By pressing a button two times
a fixed dose of a solution containing the opioid will be delivered via a motorpump into his vein, permitting a reliable, fast and individual titration according to his/her need (Figure III-60). A prerequisite for such a procedure is a computerized small "on-demand" machine, connected to an intravenous line, whereby the medical personnel can preprogram the dose, the lock-out time and the interval.
Absolute contraindications for such an "on-demand" device are a respiratory insufficiency or a pre-existing hypovolemia. A relative contraindication exists in the
Figure 111-60. Principle of patient-controlled analgesia (PCA) using an on-demand system. By the push of a button the preset dose of a narcotic analgesic is released into an intravenous line. This results in more constant blood plasma levels and a continuous occupation of opioid binding sites avoiding the conventional heights and lows of plasma concentrations with intramuscular dosing
Figure 111-60. Principle of patient-controlled analgesia (PCA) using an on-demand system. By the push of a button the preset dose of a narcotic analgesic is released into an intravenous line. This results in more constant blood plasma levels and a continuous occupation of opioid binding sites avoiding the conventional heights and lows of plasma concentrations with intramuscular dosing elderly patient population, who is not able to operate an on-demand device . Although there has been much controversy on the mechanical malfunctions and the use of an on-demand system that patient care will be neglected, that machine malfunction had led to an overdose with respiratory arrest, a patient lying in bed with severe pain in spite of him pressing the button, or visitors changing the setting of the machinery [190, 191, 192], this technique has made its way into the PACU being used by a number of institutions, thus reducing staff hours and manning of the ward with experienced personnel, which eventually reduces overhead costs.
A constant low-dose background infusion during "on-demand analgesia" for alleviation of postoperative pain has no advantages over the pure "on-demand" technique . However, similar as in any other chronic pain therapy, patient-controlled analgesia does not have to be administered via an IV line. Similar beneficial results were attained with a subcutaneous on-demand system, because there is a nearly 100% bioavailability, while at the same time reducing possible complications of an IV line. The PCA can be used effectively to evaluate the efficacy of various opioid ligands in postoperative pain relief. In a double-blind controlled study design in patients following gynecological operations, similar to other short-acting opioid analgesics such as fentanyl and alfentanil, analgesics with a long duration of action, however, with a much lesser potency, were also able to sufficiently obtund postoperative pain (Figure III-61).
Before starting to use a PCA device several questions have to be answered, all of which relate to the clinical utility of an on-demand system:
1. Choose the optimal narcotic.
2. Determine the concentration of the opioid in the reservoir.
3. Choose a lock-out time where the patient is unable to retrieve the opioid.
4. Determine the dose of the bolus.
5. Make the decision if a basal-infusion rate is necessary.
As there is no real advantage of one opioid analgesic over the other, one should use the agent with the most experience. The short-acting opioids such as alfentanil, fentanyl, sufentanil and remifentanil, although having a sufficient potency, are more difficult to titrate in a PCA setting. It is because of this drawback that these agents are not recommended for PCA use. Aside from the selection of the appropriate agent, it is of utmost importance to choose the right bolus dose in order to have a satisfactory analgesic effect when using PCA. While small doses result in insufficient pain relief, too large doses might result in severe side effects, especially respiratory impairment. The bolus-dose, therefore, should have a quantity where the patient senses pain relief, however at the same time does not experience any side effects (Table III-18). In summary, the advantages of PCA are:
1. The patients feel less apprehensive about pain following surgery because they know they have control in their hand by simply pushing a button.
2. The physician determines the amount (dosage) based on the patient's weight to prevent an overdose.
3. A narcotic addiction can be avoided because the drug is taken on a short-term controlled basis.
4. The pain relief is available around the clock. There is no need to wait for a nurse to deliver pain medication.
5. The medication does not need to be swallowed or injected.
6. The PCA unit is 'programmed' to control the dosage. The unit 'locks out' if the dosing frequency is exceeded.
Metamizole Nefopam Tramadol Pethidine Morphine Pentazocine Piritramide Alfentanil Buprenorphine Fentanyl
Metamizole Nefopam Tramadol Pethidine Morphine Pentazocine Piritramide Alfentanil Buprenorphine Fentanyl
Figure 111-61. Mean pain scores in patients following abdominal hysterectomy using a patient on-demand system for pain control with different agents. Note that a peripheral acting agent (metamizole) results in the least pain relief, while patients having access to a narcotic analgesic like, alfentanil fentanyl and buprenorphine were able to titrate their pain
7. The patient is assured they are receiving the correct medication and dose prescribed by their physician.
8. The doses are smaller and available more frequently, which helps prevent sleepiness and weakness.
9. Pain is more consistently controlled.
10. A dosing at regular intervals reduces the overall amount of medication needed to control pain.
11. Prior to expected activity (e.g. physical therapy, getting out of bed) the patient can self-dose to control pain during movement.
12. Most adults and children can use PCA. Overall, PCA can help patients to a quicker recovery.
13. Patients who are given control over their pain ambulate sooner, which promotes circulation and healing.
Opioids On-Demand, Without Use of a PCA System
If, however, one wants to achieve sufficient postoperative analgesia without the use of an additional mechanical device, the opioid has to be administered when the patient develops an increase in pain and demands the first dose. Followed by the immediate and intravenous titration of the analgesic until significant alleviation using a non-rating scale such as VAS < 3.0 (visual analogue scale where 0 denotes no pain and 10 reflects unbearable pain). Between titration, every 10th minute VAS is evaluated, in order not to overdose but at the same time administer the proper and individual quantity for pain relief. By use of the intravenous route of administration, the fastest way of the opioid agent is chosen in order to reach the specific receptor sites in the CNS. This results in an analgesic effect within minutes, and at the same time, give the medical personnel an objective sign when to stop or consider a second or even a third dose.
Such procedure is safe since because once the patient still experiences pain after the opoid medication, respiratory depression will not to be expected.
The most effective antagonist of opioid-related respiratory impairment is a nociceptive stimulus
Individual non-verbal pain rating (using a non rating scale between 0 and 10) is a necessity in order to document sufficient pain relief in the patient's chart. In addition, subtle vegetative signs of sufficient/insufficient pain relief are recorded at fixed intervals:
• Heart rate, which increases with pain
• Blood pressure, which increases with pain
• Respiratory rate, which also increases if the patient has pain
• Perspiration, a definite sign of insufficient analgesia.
Once the individual dose has been established in the PACU, this amount is recommended for use in the ward at an interval, which closely matches with the half-life of the agent. Using this practice, time-contingent dosing is possible, thus avoiding breakthrough pain, which otherwise would result in a delay of recovery and impose an unnecessary stress reaction in the patient. The individual opioid requirement in the PACU can be used to determine future analgesic requirement on the ward. A Canadian group conclusively demonstrated, that when morphine is titrated intravenously (3-6 mg) to a VAS below 3.0 in the PACU, 2.2 times of that dose is needed every 4 h in order efficient to obtain sufficient postoperative analgesia in the majority of patients .
The necessary dose of an opioid differs in each patient, it therefore should be titrated to effect. Depending on the individual dose in the PACU a recommendation is given for future treatment in the ward
In summary there are several points, which have to be considered in order to attain a sufficient post-operative pain therapy:
1. Consider individual dosing a necessity.
2. Discuss with the patients the different modalities of postoperative analgesia during the premedicaton visit.
3. Give sufficient doses of a medium to potent opioid when necessary.
4. Establish a close surveillance of efficacy during dosing intervals for adapting to patients need.
5. Regularly record pain VAS, and any potential side effects.
6. Consider a multimodal approach (i.e. COX2 inhibitor such as parecoxib plus an opioid, or ketamine plus an opioid, or a regional technique plus an opioid).
7. Immediately start with a potent opioid after upper abdominal operation or after thoracotomy, because postoperative pain will be intense.
8. Never mix a pure ^-type ligand like morphine, or hydromorphone with a mixed narcotic analgesic such as butorphanol or nalbuphine.
For medium type of pain, especially in the elderly patient population the combination of a fixed dose of tramadol together with an NSAID and an antiemetic, clinically has demonstrated an advantage.
First, there is a negligible respiratory depressive effect; second, analgesia is potentiated by the simultaneous use of a peripherally acting analgesic; third, the emetic effect of the opioid is counteracted by the additional antiemetic. And lastly, there is little consequence on the otherwise brittle cardiovascular system, which after the use of potent opioids may induce hypotension This combination of an infusion of 500 cc of Ringers with tramadol consists of:
• 25 mg trifluopromazine
Following an initial bolus dose of 100 cc of the solution, this is followed by a steady drip of 2ml/h via an infusion pump  resulting in a total dose of 18mg/h of tramadol and 200mg/h of the NSAID.
Presently there is no ideal opioid for postoperative pain therapy; therefore a multimodal approach is advocated resulting in dose-reduction of each agent, thus avoiding potential side effects
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