The prevalence of pain varies by dx, stage of disease, and setting of care. Approximately 1/3 of patients with cancer experience pain at the time of diagnosis, while 2/3 with metastatic disease report pain. Less is known about the prevalence of pain in those with diagnoses other than cancer.
Pain is described by the World Health Organization as a “multidimensional phenomenon with sensory, physiological, cognitive, affective, behavioral and spiritual components.” Pain is a complex biopsychosocial phenomenon, an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in these terms. (Pain is whatever the patient says it is.)
Types of Pain:
- Visceral pain 内脏疼痛
- Associated with the internal organs
- Generally has a poorly defined area. It is also capable referring pain to other remote locations away from the area of injury.
- It is described as a squeezing or cramping, a deep ache within the internal organs.
- The patient may complain of a generalized “sick” feeling or have nausea and vomiting.
- Visceral pain generally responds well to treatment with opioids.
- Neuropathic pain 神经病痛 – results from injury to the nervous system
- Can result from cancer cells compressing the nerves or spinal cord, from actual cancerous invasion into the nerves or spinal cord, or from chemical damage to the nerves caused by chemotherapy and radiation.
- Other causes include diabetes- and alcohol-related damage, trauma, neuralgias, or other illnesses affecting the neural path either centrally or peripherally.
- When the nerves become damaged, they are unable to carry accurate information. This results in more severe, distinct pain messages. The nerves may also relay pain messages long after the original cause of the pain is resolved.
- It can be described as sharp, burning, shooting, shocking, tingling, or electrical in nature. It may travel the length of the nerve path from the spine to a distal body part such as a hand, or down the buttocks to a foot.
- NSAIDs and opioids are generally ineffective against neuropathic pain, though adjuvants may enhance the therapeutic effect of opioids. Nerve blocks may also be used.
- Somatic pain 躯体疼痛- refers to messages from pain receptors located in the cutaneous or musculoskeletal tissues.
- When the pain occurs within the musculoskeletal tissue, it is referred to as deep somatic pain.
- Metastasizing cancers commonly cause deep somatic pain.
- Deep somatic pain is generally described as a dull, throbbing ache that is well focused on the area of trauma.
- It is responds well to opioids.
- Surface pain refers to pain concentrated in the dermis and cutaneous layers such as that caused by a surgical incision. Surface somatic pain is also directly focused on the injury. It is frequently described as sharper than deep somatic pain. It may also present as a burning or pricking sensation.
- When the pain occurs within the musculoskeletal tissue, it is referred to as deep somatic pain.
- Nociceptors- Nociceptive Pain
Concepts related to pain medication and pain management:
For mild to moderate pain, patients may take acetaminophen combined with an NSAID, such as ibuprofen, on a regularly scheduled basis or as needed (PRN) at the onset of pain or when pain is anticipated (such as before a dressing change). However, for severe chronic pain, long-acting opioid pain medications, such as time-released MS Contin, Duragesic, and OxyContin, should be given on a regular basis around the clock because these medications help to not only control but to prevent pain. The patient should not skip a dose when free of pain because this makes control more difficult when the pain recurs. In addition to time-scheduled medications, the patient may need short-acting supplementary medications, such as Percocet, to take on a PRN basis. When taking short-acting medications, the patient should take the medication at the onset of pain, before anticipated pain or at onset of increased pain if taking long-acting pain medication as well rather than waiting until the pain is severe because the goal should always be to keep the patient as comfortable as possible.
Opioids are a neccessity in hospice care. A common fear of patients when dying is not the fear of the unknown, like most would think, but instead it is not wanting to die in pain. Being able to allow patients to make the transition as comfortably as possible is one of the most valued aspects of hospice. In theory, opioid doses can be continually titrated upwards in accordance with a patient’s tolerance. There is no maximum dosage for opioids. A Cochrance review of 62 pain management studies in cancer patients showed an average daily dose of 100-250MG of morphine, with a range between 25-2000MG. Some institutions have a maximum dosage of morphine set at 6000MG a day for cancer patients, although most clinicians will typically try other methods of pain relief before going this high. On way to monitor dosage amoutns, and how much the patient typically needs of a medication, is to give PRN orders for the same drug that you are starting.
- Misuse- use of a medication other than as directed or as indicated: whether willful or unintentional, and whether harm results or not. Examples may include the use of pain medications for sleep rather than pain control; can also include diversion of medications to others for use or sale.
- Addiction– a primary, chronic, neurobiological disease with genetic, psychosocial, environmental factors influencing its development and manifestations. It is characterized by behaviors that include one or more of the following: impaired control over drug use, compulsive use, and continued use despite harm and craving. Addiction represents a state of psychological dependence in which the patient exhibits a behavioral pattern that is characterized by craving for the drug and an overwhelming involvement in obtaining and using the drug for reasons other than pain relief.
- Tolerance– a state of adaptation in which exposure to a drug induces changes that result in a diminution of one or more of the drug’s effects over time.
- Physical dependence– a state of adaptation that is manifested by a drug class-specific withdrawal syndrome that can be produced by abrupt cessation, rapid dose reduction, decreasing blood level of the drug, and/or administration of an antagonist. Physical dependence is the universal, unavoidable altered physiologic adaptation to opioid use that requires continued use of the opioid to avoid that requires continued use of the opioid to avoid withdrawal reactions.
- Signs and symptoms of abstinence syndrome (withdrawal) include anxiety, irritability, lacrimation, rhinorrhea, sweating, nausea, vomiting, diarrhea, abdominal cramps, insomnia, tachycardia, elevated blood pressure, and rarely multifocal myoclonus (multiple sites of mild to severe muscle twitching)
- Opioid pseudoaddiction– iatrogenic syndrome in which patients develop certain behavioral characteristics of psychological dependence as a consequence of inadequate pain treatment. Patients with this syndrome must continually demonstrate their need for analgesics and are often described as difficult patients, chronic complainers, drug seekers, and /or “addicts'” Patients will often resort to bizarre or dramatic behavior (acting out) in an attempt to prove their pain is real so analgesics are provided.
- Double effects-
In addition to the serious psychological harm caused by uncontrolled pain in the palliative care patient, there are several harmful physiologic effects of inadequate treatment of pain.
- Increased heart rate and blood pressure lead to increased metabolic demand and increased myocardial stress.
- Decreased mobility due to inadequate pain relief increases the patient’s risk of pressure ulcers, muscle wasting, and deep venous thrombosis.
- Risk of atelectasis and pneumonia are increased in patients who are breathing shallowly because of uncontrolled chest/chest wall pain.
Excessive sedative effects of pain medications may impair the patient’s ability to interact with loved ones, but this should be managed with medication adjustments or use of psychoactive stimulants. uncontrolled pain does not enhance a patient’s ability to have meaningful interactions with anyone. Finally, adequate pain control should not interfere with management of the patient’s primary disease.
***Methods about non-pharmacologic pain management ***
The application of heat to an area of pain: blood flow, tissue compliance, and muscle fiber relaxation increase in response to the application of a heat source. Heat also results in decreased nerve transmission of pain signals to the brain and spinal cord (via effects on both temperature and pressure receptors), which in turn enhances muscle relaxation and blood flow. Heat may be applied in a variety of ways, most of which are easy to use for both care providers and patients. Options include submersion (of either part of the body or the whole patient) in warm water, radiant heaters, hot packs, heating pads, hot water bottles, or heat wraps. Heat should not usually be applied over areas of decreased sensation because of the risk of burns.
Constipation should be anticipated and proactively treated whenever possible in the palliative care/ hospice patient. This involves regular assessments of the patient’s bowel habits and symptoms (e.g., bloating, abdominal pain, rectal pain) and monitoring for factors that predispose the patient to developing constipation (e.g., opioid therapy, decreased mobility, decreased oral intake). Because constipation is a universal adverse effect of opioid therapy, a bowel regimen should be started empirically with the initiation of opioid analgesics.
A potential side effect of opioids is opioid-induced neurotoxicity (OIN) caused by the accumulation of metabolites. Patients with poor renal function are especially at risk. Antipsychotics such as haloperidol are typically given, along with hydration and opioid reduction. Myoclonus is another side effect of opioid use and caused by metabolite accumulation evidenced by involuntary twitching of muscle groups. Although this looks like seizure activity, but pathologically it is a result from the accumulation of metabolites from opioids, therefore, antiseizure medications are not considered first-line drug for this condition. Benzodiazepines are first-line drug given for this condition.