The Effects of Opioids for Postoperative Pain Management

 By: Chad Adams

Introduction

Pain management can be simple or it can be complex, depending on what type of pain the individual has. It is extremely important to know and understand what type of pain the patient is experiencing, because this will be what one will base their treatment choices off of. Patients may complain of aches, stiffness, numbness, burning and other discomforting sensation. A clinician would customize a treatment program based on the patient symptoms, reflexes, and ROM.

 Different types of treatment programs such as:

  1. Therapeutic exercises
  2.  Transcutaneous electrical stimulation
  3.  Manual techniques
  4.  Administration of analgesics
  5. NSAIDS
  6. Narcotic medications
  7. Muscle relaxors
  8. Antidepressants
  9. Surgically implanted electrotherapy
  10. 10.  Injections

Before surgery, the patient will have a plastic tube inserted into his/her vein in their hand or arm to give them fluids, anesthetics, antibiotics or pain medications. After surgery, the doctor may keep this intravenous catheter in place to administer pain medication while the patient is in the hospital or outpatient recovery. There are specific types of pain meds that are usually injected into the IV at regular intervals and most often they are called opioids. The equipment at the hospital (Patient Controlled Analgesia System), where the patient can push a button for the fixed dose, has built-in safeguards to prevent them from overdosing. There is another way to make sure that the patient is giving his/her self  the right amount of dosage is when there is more medication in your blood stream you tend to become sleepy, possibly too sleepy to push the button; therefore, when they awaken from their sleep they can safely administer more of the drug. The “golden standard” of pain medication for post surgical management is morphine. The purpose of this article is to state whether or not it is more beneficial to the patient to be administered opioids for pain management post surgery and whether its effects are positive or negative.

What is Pain

            Development of Pain Theories

The concept of pain first was analyzed at the time of Aristotle. The word pain comes from the Latin word poena meaning penalty or punishment. As Aristotle studied pain he had come up with a theory (Aristotelian Theory) he found that this was more of a feeling then a sensation it was classified as a “passion of the soul”12. Aristotelian Theory attributed pain to excessive stimuli arising from the skin and conveyed by the blood to the heart where pain is experienced.  Aristotle’s Theory lasted for two millennia even though his theory was somewhat correct, towards the end of the nineteenth century the work of Muller and Von Frey12 contributed to a more in-depth look to the scientific properties of pain. 

In the 1840s Muller hypothesized that the sensation depends on the property of the neuroreceptor that is stimulated as well as the area of the brain in which the nerve terminates. Fifty years after Muller published his hypothesis, Frey posted that reception of pain is due to the presence of receptors in recently discovered free nerve endings.

 After all of the research over the years from Aristotle to Frey there have been three different theories that have arisen over the years these theories consist of Specificity Theory, Pattern Theory, and Gate Control Theory.

 Briefly, the Specificity Theory proposed that nociceptors, activated by mechanical deformation, chemical stimuli, or extremes in temperature, generate pain impulses carried by A-delta and C-fibers in peripheral nerves to the spinal cord. “Pain management continues to be a challenge in the care of patients in hospital environments. Contributing to this is the nature of the subjective experience of pain itself” 2. The Pattern Theory explains that the stimulus entering the spinal cord through the dorsal ganglia effects an activation of the “T-cell” in the dorsal horn, which transmits an impulse to the brainstem and cerebral cortex. These two former theories were combined to create the Gate Control Theory that is well-known today. The Gate Control Theory of Pain states: “pain due to noxious stimulus transmitted through peripheral fibers [is] subject to the interplay between three spinal cord systems, which in turn could be modified centrally” 12.

Types of Pain

The term nociceptive pain is used to describe pain that is the direct and immediate result of tissue assault. Somatic pain will arise from bony tissue, joint, muscle, skin or even connective tissue. Somatic pain is usually well localized in one area, and it throbs and aches tremendously. A type of pain that can result from a damage process to a hollow viscus or from an obstruction that typically causes cramping and poorly localized pain is known as visceral pain. There are two other types of pain and they are referred to as neuropathic pain and chronic pain. “Neuropathic pain is caused by a problem with either the nerves or the processing of nerve impulses in the CNS” 3.

Chronic pain is usually from overuse injuries and can last up to several months to several years if not taken care of properly. ”The two most common reasons for chronic pain are arthritis and back pain. “In one-half of cases the pain is not sufficient to cause significant disability, but in 16% it is regarded as severe and causes major limitations of function” 3. Chronic pain persists despite the fact that the injury has healed. The pain receptor signals remain active in the nervous system for weeks, months, or years. Some of the physiological effects of chronic pain include tense muscles, limited mobility, a lack of energy, and changes in appetite. “It has been estimated that 14 percent of people suffer limitation of activity due to chronic pain, with 9 percent experiencing major limitations in their activities” 12. Some of the emotional effects are depression, anger, anxiety, and fear of re-injury. If a person is not careful, the fear may hinder the person from returning to normal work on extracurricular activities. Most of the pain complaints from “chronic pain are: headache, low back pain, cancer pain, arthritis pain neurogenic pain and psychogenic pain” 1. Acute pain often serves a useful physiologic purpose, signaling the presence of a potentially serious disturbance in homeostasis. Persistence of acute pain, however, does not only result in increasing discomfort but is also associated with the onset of a number of physiological responses.

Treatment Options

The most common therapy used to control pain is drug therapy and the most common drugs used are opioids.  The reason opioids are used instead of a simple aspirin or acetaminophen is because those drugs may not touch the pain level. Opioids may also be chosen for use if one cannot take other types of pain medicine. It is essential that careful effort be made to determine the origin of the pain. A comprehensive description of the pain will aid in allowing an assessment as to its seriousness as well as the need for medical intervention. “Pain caused predominately by specific organ system pathology may often be best treated with analgesics only in the acute stages to provide immediate relief” 12.

 

Opioids

            History of Opioids

For generations, people have been using opium for its mind altering effects more than any drug other than alcohol. Opium is extracted from poppy seeds also known as “paper somniforum”. Opium was also used with alcohol to treat almost everything and anything that resembled a disease. In the early 1800’s, morphine became a derivative of opium and since then has been the most effective treatment for severe pain.

          Categories of Opioids

There are two categories of opioids; mild and major. Mild opioids consist of Codeine, Hydrocodone, and Oxycodone. The reason that they are considered mild opioids is because they are distributed in combination with low analgesic efficacy drugs such as aspirin and acetaminophen. The toxicity of acetaminophen and aspirin limits the dose of opioids that can be administered daily.  Major opioids consist of Morphine, Meperidine (Demerol), Hydromorphone, Fentanyl, and Methadone. The pharmacological effects of opioids are as follows: sedation, anxiolysis, drowsiness, lethargy, apathy, cognitive impairment, and sense of tranquility. There are other physiological effects of opioids such as: depression of respiration rate; which is the main cause of death from opioid overdose.

When combining opioids with alcohol, this is dangerous to the body. Opioids can also be used as a cough suppressant and another characteristic is a pupillary constriction in the presence of analgesics. Side effects include: nausea and vomiting where the stimulation of receptors in an area of the medulla called the chemoreceptor trigger zone causes nausea and vomiting. Gastrointestinal symptoms occur as well because opioids relieve diarrhea. They can also release histamines causing itching or more severe allergic reactions including bronchoconstriction. Opioids are known to affect the white blood cell function and immune function which is essential when trying to recover from an injury or surgery.

There are three opioid receptors Mu, Kappa, and Delta. The Delta receptor is not entirely understood but could possibly regulate the Mu receptor. There are two types of Mu receptors and they are as follows: Mu-1; which is located outside the spinal cord and is responsible for interpretation of pain. Mu-2 is located throughout the CNS and it is responsible for respiratory depression, spinal analgesia, physical dependence, and euphoria. Kappa receptors are only modest in analgesia and there is little to no respiratory depression or dependence. With kappa receptors there is a likely chance to experiencing dysphoric effects. “Opioids which are both agonists and antagonists may precipitate withdrawal symptoms in patients dependent on other opioids. They should not be used in combination with pure agonist opioids and are not usually considered suitable for the management of chronic pain” 1.

 

Post-Surgical Pain Medication

            Physiological Effects

Postoperative pain is an expected response and some more than others have pain that is not adequately treated. The management of postoperative pain should begin prior to the surgery during the time a history is taken by either the surgeon or the anesthesiologist. It is most important to ask the patient how they have treated their pain in the past and what worked and what didn’t. Before the surgery, the surgeon should also inform the patient on what is expected to happen after surgery once the anesthesia wears off. In relieving postoperative pain, a patient should be monitored constantly to be certain adequate amount of analgesia is being obtained. “Inadequate analgesia may also be associated with adverse systemic effects. Increased pain may affect deep breathing and cough with the potential for atelectasis, pooling of secretions, and respiratory infections” 12. The use of opioids for post-surgical pain management is most appropriate because they produce a stronger effect than regular pain medications such as aspirin and acetaminophen. Having a stronger effect comes with stronger adverse side effects such as Dysphoria, Delirium, Pruritus, Uticaria, common myths about respiratory depression with Opioid use and management of respiratory depression.

Not only can you have adverse side effects, you can become strongly addicted psychologically, develop a tolerance, and become physically dependant. The characteristics and intensity of withdrawal symptoms vary greatly with specific agent, dosage, intervals between dosage, duration of use, and even one’s psychological state. Patients who have received analgesic doses of narcotics for up to two weeks may be able to discontinue the drug with only mild symptoms, usually not attributed by either patient or physician to withdrawal. In most cases, the majority of complaints are slight irritability and difficulty in sleeping. A few signs and symptoms of withdrawal can be present quite early such as anxiety, which is usually manifested by drug seeking behavior.  Other symptoms can occur up to 8 to 12 hours after the last morphine injection such as: nausea, vomiting, constipation, lightheadedness, dizziness, drowsiness, increased sweating, or dry mouth may occur. Pain, redness, or swelling at the injection site may occur if this medication is given into a muscle or under the skin.

Mild symptoms result from early autonomic hyperactivity, which may increase in intensity over the first day and then stabilize as the syndrome progresses. Some physiological effects during this time are pupillary dilation, loss of appetite, and tremors. If a narcotic has not been administered at 16-18 hours, the patient may fall into a restless, tossing sleep for two to three hours. About 20 hours after the last dose, there is further evidence of withdrawal consisting of marked restlessness, deep breathing, fever, and insomnia.

Opioids can be extremely helpful in the reduction of pain; however the patient must be extremely careful and take precaution to predisposing factors of addiction and tolerance. “It is commonly believed that children may experience a more adverse reaction to opioids and also later down in life they have a more susceptible chance of becoming addicted. Both of these beliefs are incorrect” 12. Whether its children or an elderly person, one should prescribe narcotics appropriately to avoid respiratory depression. To clear any confusion, there is no evidence that appropriate use of opioids in children promotes addiction during adulthood.

Conclusion

In conclusion, pain can be treated with various modalities and therapies. These therapies include: Therapeutic Exercises, Transcutaneous Electrical Stimulation, Manual techniques, Administration of analgesics, NSAIDS, narcotic medications, muscle relaxors, anti-convulsants and antidepressants, radiofrequency, surgically implanted electrotherapy, prolotherapy, and injections. It would be more affective to use opioids than any other therapeutic modality as long as the drug has not been abused. Pain management is still a struggle in hospitals today with attending to the care of patients. The only way that the opioid prescribed will have a good quick affect on the patient is if the opioid itself is used as doctor prescribed. When a doctor prescribes an opioid to control the pain of a patient the dosage that is required by the pharmacist, and the doctor needs to be followed as strictly as possible so no addictions will take place. Even though there is a lot of information about pain management and the affects opioids have on humans, there are still a lot of questions waiting to be answered.

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