Patient Controlled Analgesia - Essay Example

Patient Controlled Analgesia 2006 No pain management method exists today that eases postoperative pain 100% of the time. Compared to 10years ago, on the other hand, patients at present can be made enormously comfortable with fewer side effects. Anaesthesiologists have pioneered advances in pain management, including better understanding of pain pathways, newer drugs and drug combinations as well as more effective pain-relief techniques such as Patient Controlled Analgesia (PCA). PCA has contributed to providing patients with better postoperative pain relief. Recently, PCA has become one of the most widely used techniques for pain relief after major surgery. PCA is a pain-control system where a patient can treat patient's own pain rather than wait for a nurse to give more medication (Rapp SE, Ready LB, Greer BE. 1989). This was first introduced in 1970 into obstetric practise where the patient simply controlled the administration of i.v. pethidine by operation of a spring loaded clamp on an infusion set! In a way, it mimics the use of the PCA 50:50 nitrous oxide/oxygen gas mixture (Entonox). Patient Controlled Analgesia refers to a particular type of breakthrough dosing used when a predetermined parenteral drug dose is injected following the push of a button. In reality not all PCA breakthrough doses are controlled or administered by patients, who may be physically or mentally impaired. Clinicians or families may administer the breakthrough dose in such cases, which is still often (erroneously) called the PCA dose. Thus, in practice parenteral breakthrough doses, when programmed by a pump are often referred to as PCA doses, regardless of who administers the dose. In a general sense, patient-controlled analgesia refers to a process where patients can determine when and how much medication they receive, regardless of analgesic technique. On the other hand, the term is more commonly used to describe a method of pain relief which uses disposable or electronic infusion devices and allows patients to self-administer analgesic drugs, usually intravenous (i.v.) opioids, as required. Patient-controlled analgesia produces a modest improvement in pain relief over a 24 hour period compared with conventional analgesia. It is preferred by patients, and is not associated with additional side effects. For many patients, mainly those having major abdominal surgery, PCA offers the greatest pain relief and the most flexibility. A PCA device consists of a pump, a reservoir to hold the drug and a handset with a button that administers a dose of drug when activated by the patient. Patient receives pain medication by pressing a button permitting the patient to take control of the pain. This eases the anxious waiting for pain relief and the peaks of pain (Macintyre PE, Runciman WB, Webb RK. 1990). Patient controlled analgesia is widely used for postoperative pain relief in both children and adults. Unfortunately, postoperative pain control is often the last concern discussed with patients even though it can become the major concern after the operation is performed. Most patients are more worried concerning the potential surgery and anaesthetic complications prior to surgery, than they are with pain control after surgery. Therefore, patients are often overshadowed by the patient's anxiety regarding the procedure Postoperative pain management actually starts preoperatively. The anaesthesiologists and surgeon will decide on a plan prior to the surgery. A major deciding factor with regard to choosing an appropriate plan will depend on whether the patient is to be discharged the same day (day surgery) or will be admitted after surgery. With right preoperative teaching and encouragement, children as young as 6 to 7 years of age can independently use the PCA pump to provide good postoperative pain relief (Kluger and Owen H. 1990). Children between the ages of 4 and 6, though, generally require encouragement from the parents and nursing staff to push the button before anticipated painful movements or procedures. Even with encouragement, the failure rate among 4 and 5 year olds with PCA appears quite high. For younger children, NCA has recently gained popularity to permit small titrated dosing of opioids for infants and children unable to use the PCA button. Patient-controlled analgesia is one of the newer techniques for pain management. It was developed in reaction to the large number of unsatisfied postoperative patients suffering from moderate to severe pain despite the availability of potent analgesic drugs. With PCA, patients are permitted to self-administer small analgesic doses into a running intravenous infusion, intramuscularly, subcutaneously or even into the spinal space. Clinical experience soon established that individual variability in pain intensity and analgesic needs was extremely large. Psychological factors seem to be as important as the surgical trauma. Opioid consumption is usually higher than with conventional regimens, but without serious side effects. Although patients generally prefer self-control, pain relief is not necessarily better than with well-conducted conventional techniques. In addition to routine clinical pain management, PCA has proven its importance in research, for instance, for pain measurement, to determine predictors of postoperative pain, to evaluate drug interactions and the concept of pre-emptive analgesia, or for pharmacokinetic designs. PCA has been extremely important in order to change the mind of physicians and nursing staff with respect to individual pain management strategies. Intravenous administration is the preferred route for postoperative opioid therapy when the patient cannot take oral medications. When intravenous access is problematic, sublingual and rectal routes should be considered as alternatives to traditional intramuscular or subcutaneous injections. All routes other than intravenous require a lag time for absorption of the drug into the circulation. Additionally, repeated injections with associated pain and trauma may deter some patients, especially children, from requesting pain medication. Continuous administration of low doses of opioids intravenously or transdermally and intermittent delivery across the buccal mucosa are relatively new but apparently effective methods to administer opioids postoperatively. Further experience is needed to define the clinical roles of these innovative methods in relation to more well-established methods. Pain has been officially described as an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage. It is essential to distinguish between pain perception threshold which is somewhat constant approximately 44-45 deg. C applied to the skin is recognised as painful by most subjects and the pain tolerance threshold which is the maximum amount of pain that the subject is prepared to tolerate and is very variable. It is the latter that is most important in the patient's perception and attitude to pain, and thus whether he or she will seek treatment. Unstable pain changes rapidly up and down. Opioids require frequent adjustment. Rapidly lessening pain may be seen in most acute pain syndromes, in which pain naturally decreases over time. Pain following surgery or trauma is usually of this nature. Chronic pain, such as is found in many cancers, may also rapidly decrease in certain situations, such as when a painful focal metastasis is radiated. When pain is quickly increasing or decreasing, appropriate opioid therapy requires less reliance on basal opioid doses and more on PCA doses. In the extreme, most surgeons treat postoperative pain entirely with PCA doses. Such therapy has the advantage of minimizing the chance of opioid excess that would result from unnecessary amounts being administered to a patient with lessening pain and a decreasing need for opioids. Excessive reliance on PCA dosing risks making the patient overly dependent on pushing the PCA button on time. Such patients may state that pain is well controlled while awake, but when they fall asleep and thus cannot push the button patients may suddenly awaken in pain and play catch-up with PCA doses. Sleep is thus disturbed, which is an impediment to healing. Some of the more recent studies comparing PCA with conventional methods of opioid analgesia, administered as intermittent i.m., subcutaneous and i.v. injections, or by continuous infusion, have produced contradictory results. Some show significantly better analgesia with PCA and others report no difference. Colwell and Morris (1995) noted better analgesia after i.m. morphine. However, PCA bolus doses used in their study were small, 0.25 or 0.5 mg morphine, while patients in the i.m. group could receive up to 15 mg morphine every 3 h if required. Sample sizes in many of these studies are small and difference, or lack of difference, could be difficult to detect. Given the continuing popularity of PCA, these results could be seen as surprising. However, it is possible, if analgesia can truly be given 'on demand', with doses and appropriate dose intervals tailored to the individual patient, that good results can be obtained regardless of analgesic technique. The rationale of PCA is that an improvement in analgesic efficacy is obtained by allowing the patient rather than the nurse to manage analgesic requirements. Although the availability of custom made apparatus, with in-built safety features, have increased the popularity and applicability of the technique, the cost of the apparatus remains prohibitive. The normal route of administration is i.v., but the i.m., s.c. and epidural routes are also used. The patient must be given clear instructions on how to use the apparatus for maximal benefit. To avoid inadvertent toxicity, the following parameters must be correctly pre-set by the operator: Dose and concentration of opioid used is set-up in the machine, this allows calculation and storage of doses administered to the patient; Demand dose administered (for example 15 mg. for i.v. pethidine); Lockout interval is the interval from an administered dose until the next dose is given by the machine, despite patient requests (for example 9 minutes for pethidine). This prevents repeated doses at short intervals and thus limits toxicity but also the amount of drug the patient can receive; Maximum hourly or 4 hourly dose (for example 50 mg. hr-1 for pethidine); and Background infusion of opioid, if required. This may be fixed or interactively adjusted according to the frequency of patient demands. Electronic and disposable infusion devices are both used in the provision of PCA. Each type has two components a reservoir and a patient-control module. Although equipment-related PCA complications are less common than operator-related or drug-related problems, device design and malfunction may affect analgesic efficacy and patient safety. Problems may also arise with PCA-related consumables. Disposable PCA devices typically deliver 0.5 ml with each patient demand, take about 6 min for the patient-control module to refill from a reservoir, and deliver no more than 0.5 ml every 6 min, should the demand button be depressed continuously. Efficacy and side effects may be comparable with the electronic devices. However, as the device delivers a fixed volume with each demand, the amount of drug delivered in each bolus can only be altered by changing the concentration of drug in the reservoir. In addition, the opioid in the reservoir is much more easily accessible than that in locked electronic infusion devices. Few significant problems as a result of malfunction have been identified. One of the more potentially serious episodes is that where the absence of an 'O' ring allowed unrestricted flow of opioid from the reservoir. Fortunately, this was noticed before the device was attached to the patient. Electronic PCA devices allow more flexibility in the timing and amount of dose delivered. They can also be programmed to deliver a constant background infusion. They are designed to be 'tamper proof', so that access to the drug without using the key is impossible, at least unless the pump is damaged in the attempt. However, successful access has been achieved without machine breakage unpublished observations. Reports of problems related to the use of electronic PCA devices seem to be more common, although that may reflect usage patterns. These devices should 'fail safe' if any corruption to the program occurs. Reports in the literature describe 'fail safe' electrical corruption of the pump program as a result of disconnection from, or reconnection to, mains power. In some instances, however, the machines did not 'fail safe' (Notcutt and Morgan RJ. 1990). This led to spontaneously triggered bolus doses (Notcutt and Morgan RJ. 1990) or uncontrolled delivery of the entire syringe contents. Modifications to both hardware and software appear to have overcome these problems in later machines, although a report of repeated spontaneous triggering was published recently. Patient-related factors, including age, psychological characteristics, concurrent disorders, opioid dependency, and inappropriateness of PCA use, may have a significant influence on the safety and efficacy of PCA. Although very young and very old patients may be less likely to manage PCA successfully, PCA should not be withheld simply on the basis of age. Children as young as 4 yr old to patients in their late 90s have been reported to use PCA effectively. The successful use of PCA requires reasonably normal cognitive function and patients who have pre-operative evidence of dementia or become confused post-operatively more likely in the elderly patient are not suitable candidates for PCA. Post-operative PCA opioid requirements in adults are known to decrease as patient age increases, and it has, therefore, been suggested that a lower PCA bolus dose is prescribed for elderly patients. Concurrent use of a background infusion is contraindicated in these patients, if they are opioid-naive. The subjective experience of pain is dependent on a number of factors, including patients' psychological characteristics. These include state anxiety a transitory state which varies in intensity and over time, and is associated with specific situations involving threat, trait anxiety a personality disposition which is relatively stable over time, neuroticism, and coping style. These characteristics may affect how well patients make use of PCA and, therefore, its effectiveness, and should be taken into account when patients are considered for this form of pain relief. PCA, without a background infusion, has been used safely and effectively for pain relief after abdominal surgery in morbidly obese patients, up to 40% of who may have OSA. If patients are known to have OSA, more intensive monitoring and judicious use of PCA have been suggested. Patients with a history of opioid consumption whether legally prescribed or illegally obtained before admission to hospital may be dependent on these drugs that is they will exhibit signs of withdrawal if the drug is suddenly stopped or antagonized and may show signs of tolerance to both their analgesic effects and side effects. Rapp and colleagues, (1995) compared PCA use after surgery in opioid-tolerant patients, patients with cancer pain, chronic non-cancer pain, and those with an opioid addiction, and in opioid-naive control patients. They concluded that patients with previous exposure to opioids were likely to have higher opioid requirements; total doses averaged three times those of opioid-naive patients, higher pain scores, and fewer emetic and pruritic symptoms. Surprisingly, sedation scores were higher in the opioid-tolerant patients. Although patients in this group were much more likely to be given concurrent anxiolytics, the authors state that this did not correlate with increased sedation. This suggests that if opioid doses can be rapidly increased to levels significantly in excess of pre-admission basal doses, over sedation a better clinical indicator of early respiratory depression than a decrease in respiratory rate may occur in patients who are considered to be tolerant to effects of the drugs. Addiction to opioids was initially thought to be a contraindication to the use of PCA, but it is now recognized to be a useful method of providing pain relief. This may be partly because these patients may have high and unpredictable opioid requirements, and partly because it helps to avoid staff/patient confrontations about dose and dose interval. As these patients are more likely to report high pain scores, a functional assessment of pain relief may be required in addition to patient self-reports when determining efficacy of analgesia. Costs involved in the provision of analgesia, including the direct costs of drugs, consumables, equipment, and labour, are important when considering whether or not to use a particular method of pain relief, even if it is more effective. PCA may provide superior analgesia and patient satisfaction; it does so at a higher cost. A comparison of the differences in cost across is difficult as they vary with respect to patient population, organization of PCA management, PCA device involved, drugs administered, and methods used to determine expenses. A significant part of the cost of PCA is the cost of equipment, drugs, and consumables. Nursing time time involved in the provision of analgesia is usually much less compared with conventional forms of pain relief. Therefore, in a busy general hospital ward where the number of appropriately qualified nurses may be limited, it is possible that the use of PCA in some patients may allow more time to attend to other duties, including the more effective provision of other forms of analgesia to patients without PCA. In view of the current need in most countries to control health care costs, a decrease in average length of stay (ALOS) in hospital also has important implications. The safety of PCA depends on an adequate understanding of the technique by the patient and the fact that unauthorized persons do not press the demand button. Over sedation with PCA has followed repeated use at the end of every lockout period, mistaking the PCA handset for the nurse-call button, and family, visitor, or unauthorized nurse-activated demands. Negative aspects about PCA have also been identified, some of which might constrain the use of PCA and, hence, it's effectiveness. Nausea and vomiting are common side effects PCA with opioids. When severe, nausea and vomiting may limit a patient's tolerance of PCA. Giving antiemetics prophylactically has been suggested as a way to prevent PCA-associated nausea and vomiting. Studies have shown that patients utilizing PCA use less overall amounts of medication compared to patients not using PCA. Since the amount of narcotic medication is reduced, side effects such as sleepiness, nausea and itching are also reduced. PCA is also safer than giving patients intermittent large doses (boluses) of narcotic. When PCA is used, there is a three-fold reduction in the incidence of life-threatening respiratory depression, which is a side effect of using opioids. Inadequate pain control, on the other hand, can lead to complications from immobility (because moving is painful) such as pneumonia, deep vein thrombosis (blood clot) or even myocardial infarction from the pain itself. Most often the negative remarks relate to inadequate analgesia and/or the presence of side effects, but some patients also report not trusting the PCA machine, or fearing overdose, or addiction. 22% of patients feared addiction and 30% feared overdose, much higher than the 4 and 11%. However, 43% of patients in the former study did not receive pre-operative education about PCA and 24% received no instruction at all at any time during PCA therapy, whereas all patients in the latter study received education about pain management and PCA prior to surgery. Lack of education was associated with higher pain ratings. PCA can be a very effective and safe method of pain relief and may allow easier individualization of therapy compared with conventional methods of opioid analgesia. However, it is not a 'one size fits all' or a 'set and forget' therapy and original prescriptions may need to be adjusted if maximal benefit is to be given to all patients. Efficacy and safety will also be increased if attention is paid to the factors outlined above. Thus, the success or otherwise of PCA lies in how well it is used. REFERENCE Colwell CW jr, Morris BA. (1995). Patient-controlled analgesia compared with intramuscular injection of analgesics for the management of pain after an orthopaedic procedure. J Bone Joint Surg Am. Kluger MT, Owen H. (1990). Patients' expectations of patient-controlled analgesia. Anaesthesia, 1072-4. Macintyre PE, Runciman WB, Webb RK. (1990). An acute pain service in an Australian teaching hospital : the first year. Med J Australia; 153(7) : 417-421. Notcutt WG, Morgan RJ. (1990). Introducing patient-controlled analgesia for postoperative pain control into a district general hospital. Anaesthesia. Rapp SE, Ready LB, Nessly ML. (1995). Acute pain management in patients with prior opioid consumption: a case-controlled retrospective review. Pain; 61: 195-201. Rapp SE, Ready LB, Greer BE. (1989). Postoperative pain management in gynaecology oncology patients utilizing epidural opiate analgesia and patient-controlled analgesia. Gynaecologic Oncology; 35(3) : 341-344. Read More