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8 Articles in Volume 11, Issue #2
Preventive Therapies for Cluster Headaches
The Pain of Multiple Sclerosis: Is it Real and Is it Treatable?
Antidepressants in the Treatment of Chronic Pain
Genetic Screening for Defects in Opioid Metabolism: Historical Characteristics and Blood Levels
Post-operative Patient-controlled Analgesia in Pediatric Patients
Pharmacogenetics in Pain Care: Consideration of Economic Impediments and Ethical Imperatives
Are Opioids More Harmful Than NSAIDs for Elderly Patients?
How Genetics Can Complicate Pain Treatment

Post-operative Patient-controlled Analgesia in Pediatric Patients

Despite advances in pain management over the past decade, post-operative pain in children continues to be under-treated. When an intravenous line is in place, the delivery of analgesia through patient-controlled anesthesia (PCA) can provide safe, effective, and convenient pain control in this special population.

Throughout the past decade, the field of pediatric pain management has seen numerous advances. Despite these advances, multiple studies have suggested that pain in children continues to be under-treated post-operatively. It is essential to provide pain management to pediatric patients in a manner that will be accepted by children. Ideally, oral analgesic medication should have a flavor that is pleasant to them, and intra-muscular or subcutaneous injections should be avoided if possible. If the child has an intravenous line in place, it is preferable to administer analgesia via that route. The delivery of analgesia through intravenous patient-controlled anesthesia (PCA) provides pain control safely and efficiently, while maintaining patient satisfaction.1 This article provides a summary of current PCA information in pediatric patients.

Pediatric Pain Management Lacking

As noted, clinicians have made numerous advances in the diagnosis and treatment of children with post-operative pain. One advance has been the improvement in the diagnosis of pain through various age-related scales. Quantifying and standardizing pain intensity in children is a difficult task. Although these scales are ubiquitous in modern healthcare, there is continuous scrutiny in regard to their reliability. There has also been significant progress in understanding the physiology of specific pain pathways.2

Although clinicians have gotten better at understanding and diagnosing the cause of pediatric pain, studies have shown that pain management among children falls short of their adult counterparts. Indeed, researchers have found that after children and adults have undergone equivalent surgical procedures, pediatric patients have received a significantly lower relative dosage of opioid analgesia than adults. Pediatric patients were more likely to receive oral, non-opioid analgesia following major surgery, while adult patients were more likely to receive intravenous morphine.2,3

Many theories have attempted to explain the deficiency in pediatric post-operative pain control. One prevailing conjecture is that healthcare professionals are uncertain about age-specific and weight-specific dosing. Drug companies have been reluctant to conduct drug studies in pediatric patients.4 There is an underlying fear that analgesic drugs will produce severe adverse effects in children because of their age and small size.1 These fears can be alleviated by adhering to strict dosing protocols as well as diligent assessment and documentation of side effects.

Previous misconceptions have led to insufficiency in pain management in children. One of the main fallacies is the belief that children suffer less pain than adults.5 However, it has been documented that humans begin to feel pain early in intrauterine life.6 Unfortunately, if the child is not evaluated appropriately and frequently, healthcare workers may overlook the child’s pain. To adequately manage pain in children, it is imperative to assess pain with age-appropriate scales.

The Joint Commission has recently mandated that hospitals perform a systematic pain assessment on all patients and that they require a protocol for pain management.4,7

Special consideration must be given to pediatric patients regarding post-operative pain management. Often, the intense, acute pain of surgery goes unrecognized and undiagnosed in children, which leads to significant suffering.8 Therefore, it is important to identify post-operative pain in children and to provide appropriate analgesic treatment.

In the majority of cases, post-operative pain is most severe the first few daysafter a procedure but graduallyimproves over time. Thus, it is essential to manage pain carefully during this period.

In the majority of cases, post-operative pain is most severe the first few days after a procedure but gradually improves over time. Thus, it is essential to manage pain carefully during this period.

Pain treated insufficiently will cause the child significant stress, which will stimulate a hormonal response. It may also alter nociception by magnifying the pain pathway and may produce a chronic effect.1 Both of these factors can delay the child’s recovery.

Uncontrolled post-operative pain can produce long-term psychological effects on a child. It can elicit fear and suffering and substantially hinder the quality of life for both patients and their families. It is, therefore, the responsibility of healthcare workers to recognize pain and to provide sufficient analgesia to expedite recovery and allow the child to resume their daily activities.

Properties of Patient-Controlled Analgesia

Patient-controlled analgesia has significantly improved post-operative pain management.9 It is a method of pain control in which the patient self-administers medication by pressing a demand button connected to a pump. The medication is administered immediately, usually through an intravenous line, with the expectation that the patient will feel instantaneous relief. In children, PCA can initially be used at approximately 6 years old.2 The device requires that the child understands the relationship between pressing a button and receiving analgesia. It is also necessary for the patient to be awake and physically able to press the button attached to the pump.

Patient-controlled analgesia allows for a pre-determined dose of a specific analgesic medication to be dispensed through a sophisticated machine that the healthcare provider has previously programmed. Pre-determined variables are set through the PCA pump to establish the essential safety limits for the analgesia medication. The variables include an initial loading dose, a demand bolus dose, a lockout interval, background infusion rate, and 1-hour or 4-hour limits.9 (See Table.)

In addition to PCA pumps, many pain practitioners have advocated the use of a background infusion. A background infusion is a continuous rate of analgesia given regardless of the patient pressing the demand button. Continuous background infusion is generally reserved for patients with opioid tolerance due to a chronic pre-existing painful condition, such as malignancy. This subset of patients usually requires a higher baseline of opioid to reach their analgesic threshold.

Table. Variables of Patient-Controlled Analgesia

Initial loading dose

Provides preliminary pain relief in the post-operative setting; it is optimal that this dose is administered early.9 The initial loading dose titrates the medication to an analgesic level with the intention of preventing pain before it becomes severe.

Demand bolus dose

Analgesia is delivered when the patient presses the button to activate the machine. The pump is programmed to administer a specific amount of medication that will alleviate current pain without causing harm through unwarranted side effects.

Lockout interval

A determined length of time between administrations of the demand boluses when the machine will not deliver analgesia even if the button is pressed; this is an inherent safety mechanism of the machine that prohibits an overdose of medication.

Background infusion

Addition of a background infusion rate to the demand dose

Time limits

One-hour or 4-hour limit setting allows only a specific amount of analgesia to be administered during that time interval. The goal of these limits is to provide a further safety mechanism prohibiting an overdose of medication and limiting side effects.

 

There is debate, however, about the use of continuous background infusion because of the risk of severe sedation.10 Patients receiving a continuous background infusion need to be closely monitored for side effects. This is especially true in children, where continuous infusion of medication while the child is sleeping could mask the signs of sedation. Patient-controlled analgesia without a background infusion requires the child to be awake and coherent to push the demand button for analgesia, thus limiting the risk of sedation.

Advantages of PCA

Patient-controlled analgesia has advantages over traditional around-the-clock analgesia because it offers a consistent level of pain control. For example, in the traditional form of analgesia, an order of morphine at 0.1 mg/kg given every 4 hours will provide the patient with an initial high peak of analgesia followed by low troughs when approaching the fourth hour. The higher dose of morphine may heighten the peak enough to exceed the threshold for side effects. The low troughs leave the patient in pain, awaiting the next dose.

The advantage of PCA is that it eliminates the high peaks and low troughs by allowing the patient to press the demand bolus button when they begin to feel pain. For example, an order may be written for a demand bolus dose of 0.025 mg/kg with a 6-minute lockout interval. If the patient continues to have pain after receiving the first bolus, they can press the demand button again after 6 minutes to receive another dose. After 2 bolus doses they would have received a dosage of 0.05 mg/kg of morphine, which is considerably less when compared with the peak seen in the traditional around-the-clock method. If the pain returns within the next hour, the patient can press the demand button again and receive another demand bolus without the need to wait until 4 hours have passed.

All children receiving intravenous PCA should be monitored for pain control regularly. An age-appropriate pain assessment should be performed and documented to evaluate the efficacy of the analgesia provided. The effectiveness of PCA pain control can also be assessed by recording the number of times the patient attempts to receive the demand bolus and comparing that to the actual demand boluses delivered. If the patient is demanding more analgesia than allowed during the lockout interval, this may be a sign that their pain is not sufficiently controlled. If the patient continues to have pain after exceeding their limit in demands, a rescue clinician-approved bolus dose may be given for relief. If this is required often, it may be necessary to increase the dose, decrease the lockout interval, or change the type of medication provided through the PCA.

Pharmacology for PCA

The primary determination of which analgesic drug to administer is always preceded by a clinical assessment of the patient. It is necessary to weigh the risks and benefits for all analgesics on an individual basis. Opioids are commonly used with intravenous PCA for post-operative pain control in children.

Morphine is one of the most studied opioids provided by PCA. Morphine is metabolized by the liver and produces morphine-6-glucuronide, which binds to µ-receptor sites, thereby providing an analgesic effect. The µ1-receptor is responsible for the analgesic effect of morphine and the µ2-receptor is responsible for adverse effects, such as respiratory depression. The metabolites of morphine undergo renal excretion and can accumulate in patients with renal impairment. The accumulation of metabolites can cause severe side effects of the drug even when small doses are used.9

Hydromorphone is an opioid similar to morphine that is often administered through PCA. It is approximately 5 times more potent than morphine and is frequently used in patients with renal failure because the metabolites do not accumulate as they do with morphine.7

Another frequently used opioid for the control of post-operative pain in children is fentanyl, which is approximately 70 to 100 times more potent than morphine when given as a single dose. When administered through a continuous infusion, fentanyl is approximately 30 to 50 times more potent than morphine.7 It is typically used with PCA because of its fast-acting qualities. Fentanyl has a quick onset of action due to lipid solubility and can easily cross the blood-brain barrier. However, it has a shorter duration of action than morphine caused by re-distribution into body tissues.

Many studies propose implementing a poly-pharmacology approach to pain management in children. In this approach, non-opioid analgesia is provided regularly, and opioid PCA is reserved for breakthrough pain. Acetaminophen and non-steroidal anti-inflammatory drugs (NSAIDs) are valuable options in the poly-pharmacology approach to pain management with PCA.11 This approach is considered to have a synergistic effect on pain control.1 It has the ability to decrease both the necessity for demand boluses and the overall consumption of opioids, thereby decreasing the risk for potentially serious side effects.2,11

Adverse Effects in Children

Although post-operative use of PCA in children is widely accepted, it is not without risk. The side effects of PCA are directly related to the use of opioids. The symptoms include nausea, vomiting, pruritus, urinary retention, constipation, sedation, and respiratory depression. The type of surgical procedure, anesthesia administered, and level of anxiety may increase the likelihood of developing side effects.9 Side effects can exacerbate suffering in the patient, highlighting the importance of aggressive treatment.

Some of the most common side effects in patients receiving opioid PCA are nausea and vomiting. They’re caused by an agonist effect at the opioid receptors in the chemoreceptor trigger area. Ondansetron is frequently used to treat post-operative nausea and vomiting. It works as an antagonist at the 5-HT3 receptor. Metoclopramide is also frequently used to treat nausea and vomiting, although it has certain side effects, including extra-pyramidal symptoms.7

Opioid analgesia has been known to cause constipation in some patients. Stool softeners and stimulant laxatives have been beneficial in the treatment of opioid-induced constipation. It is important to rule out obstruction as a cause of their symptoms.

Pruritus induced by opioids can be successfully treated with diphenhydramine. The side effects of anti-histamines are urinary retention, constipation, and sedation that may intensify the side effects produced by the opioid. Low doses of naloxone have been shown to decrease pruritus by acting as an antagonist at the µ-receptor binding site.7

One of the most serious adverse effects of PCA is respiratory depression. Changes in respiratory rate and oxygen saturation are an alarming sign. Patients receiving background infusion, PCA by proxy, or sedatives are at an increased risk of developing respiratory depression.9 It’s important to anticipate this scenario and have a protocol for the management of respiratory depression prepared. Some institutions recommend having a standing order for naloxone and oxygen supplementation.

Monitoring post-operative patients for side effects is essential. Vital signs and pain and sedation assessment should be measured regularly for all patients receiving PCA. Opioid naïve patients receiving continuous infusion or receiving PCA by proxy should be monitored with particular concern. As with all pediatric medications, careful dosing calculations should be made to avoid error.

PCA by Proxy

There is a considerable debate about using PCA by proxy. PCA is inherently safe because it requires the patient to push the button and administer analgesia. If the patient is sedated, they will not be able to push the button to receive an opioid bolus and their systemic levels of the drug will decrease further from the side effect threshold. PCA by proxy eliminates this inherent safety aspect of PCA, therefore requiring exceptional prudence.

PCA by proxy is generally reserved for younger patients or those with cognitive disabilities who are not able to use the PCA device on their own. In these cases, a nurse or parent triggers the PCA pump to provide a demand bolus dose to the patient in pain. For this method to work efficiently, the caregiver must recognize the signs of increased pain in the patient. If the patient is able to talk, an age-appropriate pain scale should be used. However, if the patient is non-verbal, pain associated behaviors should be assessed. Pain associated behaviors include crying, facial expressions, and body movements.2 Nursing staff members may have had previous training in pain assessment in pediatric patients, while parents most likely have not. It is crucial to provide pain assessment education to the caregiver and instructions on when to administer medications with the PCA pump. Well-intentioned caregivers may cause harm by administering analgesia while the patient is sleeping or not in pain. These pre-emptive doses put the patient at risk of sedation, respiratory depression—even death.12

A study by Voepel-Lewis et al12 found that patients receiving PCA and patients receiving PCA by proxy had equal frequency of pain, sedation, and respiration assessment. The researchers found that patients who had a proxy had lower pain scores than the patients receiving PCA on their own. The rate of sedation was equal among both groups. The patients administering PCA were more likely to have side effects that were resolved by providing supplemental oxygen and lowering the opioid dose. However, PCA by proxy patients were more likely to have severe respiratory events that required naloxone or endotracheal intubation. It is important to note that patients receiving PCA by proxy tended to have more co-morbid conditions in comparison to those receiving PCA alone.

Conclusion

Post-operative pain management in pediatrics has improved in recent years. Patient-controlled analgesia has contributed to the improvement of pain control in children. It has been shown to be safe and effective in children and is a valuable option to consider when treating post-operative pain in pediatric patients.

 

Last updated on: November 26, 2012
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