Pain Medicine

KEY POINTS 1. The excitatory amino acids glutamate and aspartate are the key excitatory neurotransmitters in the somatosensory system. 2. The four types of excitatory amino acid receptors are the NMDA, AMPA, kainite, and metabotropic receptors. 3. GABA and glycine are the key inhibitory neurotransmitters. Substance P is the key excitatory neuropeptide in the somatosensory system. 4. The enkephalins and somatostatin are the key inhibitory neuropeptides in the somatosensory system.

KEY POINTS 1. Psychological evaluations for pain and disability typically include psychological testing and an interview. 2. Key domains for assessment include pain-related disability, negative affect, pain-related cognitions, coping strategies, psychopathology, and substance use. 3. Multidimensional instruments offer the potential of assessing selected key domains as well as social factors. 4. When interventional pain therapy is being considered, it is advisable to obtain a specialized psyc

KEY POINTS 1. Somatoform disorders involve somatic complaints that cannot be explained by any general medical or neurologic condition, the effects of a substance, or a culturally sanctioned behavior. 2. Somatization disorder is a polysymptomatic entity beginning before 30 years of age, extending over a period of years, and is characterized by a constellation of pain, gastrointestinal, sexual, and pseudoneurologic symptoms. 3. Undifferentiated somatoform disorder involves one or more physical

KEY POINTS 1. Electrophysiologic studies are very sensitive indicators of central and peripheral nervous system involvement but do not indicate underlying disease. 2. EMG/NCV studies can identify the anatomic site of injury, the type of neurons or fibers involved, the nature of the pathologic alteration, and severity of injury. 3. In QST, cold threshold measures Ad fiber function, whereas warmth, heat pain, and cold pain thresholds reflect the function of C-fibers. 4. SSEPs provide a quantit

KEY POINTS 1. Disability is a vaguely defined term that describes the inability to perform specific tasks or functions. 2. Impairment is an objective loss of function due to an injury or disease process. 3. Pain specialists require an understanding of disability terminology to provide objective ongoing or independent assessments of pain patients with disabilities and impairments

KEY POINTS 1. With an informed and cautious approach, opioids may be safe and effective for treating moderate to severe pain of both malignant and nonmalignant origin. 2. Clinicians who choose to offer chronic opioid therapies must formulate rational and individualized regimens according to strategies such as those described by the FSMB and the APS/AAPM consensus guidelines. 3 Safe opioid therapy requires a program for continuous and close observation of analgesia and possible adverse effects

1. The risk-benefit profile of long-term opioids should be carefully weighed in regard to risks for misuse or addiction, endocrine deficiencies, medical comorbidities such as sleep-disordered breathing, and the development of heightened pain sensitivity. 2. Every clinician who provides opioids should be familiar with risk factors for opioid misuse or addiction, screen patients accordingly, and set a level of clinical monitoring and reassessment appropriate to the degree of risk, which may cha

1. In neuropathic pain, there is altered processing and changes in central modulation. These include pathologic activity in injured nerves (resulting in hyperexcitability, spontaneous and evoked pain), loss of C-fibers, sprouting of the large fibers in the outer laminas of the dorsal horn where the nociceptive-specific neurons are located (resulting in allodynia), and increased activity in the sympathetic nervous system. 2. Some of the molecular changes in neuropathic pain include the accumulat

1. NSAIDs are antihyperalgesic compounds with antiinflammatory activity determined by their ability to decrease prostaglandin formation through inhibition of COX following tissue injury. 2. There are two major isoforms of COX. COX-1 is largely constitutive and is responsible for the production of prostaglandins involved in homeostatic processes in the stomach (gastric protection), lung, and kidney, and in platelet aggregation. COX-2 is an inducible form created in the presence of inflammation,

1. Pain relief after local anesthetic blockade does not reliably predict successful neurodestructive surgery, that is, long-lasting analgesia without deafferentation pain. 2. Prognostic local anesthetic blocks may be used to evaluate patients for neurolytic block. A negative response to blockade may be extremely valuable in preventing an unnecessary neurodestructive procedure. 3. Relief of neuropathic pain with intravenous lidocaine appears to predict potential responders to oral mexiletine t

1. Ablative techniques have been used for many decades to control intractable pain. While they continue to have some well-defined indications, they have largely been replaced by neurostimulation procedures. 2. The results of ablative procedures for pain tend to be highly variable, with a substantial proportion of patients obtaining relief early and then experiencing recurrence of pain. 3. Ablative procedures such as cordotomy may be useful in treating pain of malignant origin, given the limite

KEY POINTS 1. Pain management is the first step in restoration of function. Functional improvement is not always synonymous with alleviation of pain. 2. Physical modalities (ultrasound, hot packs, etc.) may be of benefit in acute pain situations. Chronic use of these interventions should be discouraged. 3. Exercise treatment is a helpful adjunct in treating patients with all types of pain disorders. Exercise programs should include flexibility, muscle strengthening, and aerobic exercise. 4.

KEY POINTS 1. AP and related techniques trigger a sequence of events that involves the release of endogenous opioid-like substances, monoamine neurotransmitters (e.g., serotonin and norepinephrine), expression of c-fos in CNS, and potential reversal of neuroplasticity in animal models. 2. EA of 2 Hz accelerates the release of enkephalin, beta-endorphin, and endomorphin, while EA of 100 Hz selectively increases the release of dynorphin. 3. PENS and AP-like TENS may present potential applicati

KEY POINTS 1. Pain is the most common complaint seen in the emergency department. The emergency physician must ensure that patients in pain are treated with appropriate analgesics as soon as is feasible. 2. With modern diagnostic modalities, such as CT scanning, there is no reason to withhold pain medications for patients with abdominal pain. The goal is to reduce the pain for patients while they are undergoing diagnostic evaluation. Oversedation should be avoided to enable reliable physical

1. Postoperative pain results from peripheral and central sensitization. 2. The NMDA receptor responds to glutamate, an excitatory amino acid. 3. The concept of preemptive analgesia is the perception that therapies can be applied prior to a noxious event in order to prevent or reduce the magnitude and duration of postinjury pain and/or the development of chronic pain. 4. The concept of preventive analgesia is using antinociceptive treatment to cover the entire period of highintensity noxiou

KEY POINTS 1. Most of the randomized studies on perioperative intravenous (IV) ketamine infusion showed beneficial effects. The surgeries studied included abdominal, gynecologic, or spine surgery. 2. Ketamine IV infusion appears not to be beneficial when total IV anesthesia is the technique of intraoperative anesthesia. 3. The addition of a ketamine infusion in patients who had patient-controlled epidural analgesia resulted in less opioid requirement and probably a lower incidence of chroni

KEY POINTS 1. Patient-controlled analgesia is a programmable delivery system by which patients self-administer predetermined doses of analgesic medication at the push of a button. PCA can optimize drug delivery and improve satisfaction by enabling patients to titrate analgesia. 2. Safe use of PCA requires the patient to control analgesic delivery. Increasing plasma concentrations of opioid usually cause sedation prior to causing clinically significant respiratory depression. Sedation usually

KEY POINTS 1. The pharmacologic properties of IT opioids reflect the extent of the hydro- versus lipophilicity of the specific opioid: lipophilic opioids (fentanyl and sufentanil) have a shorter onset and duration of action, whereas hydrophilic duration of action (and certain side effects such as delayed respiratory depression). 2. Like opioids administered by other routes, IT opioids may result in widely recognized opioid-related side effects such as nausea, vomiting, pruritus, sedation, and

KEY POINTS 1. As is seen with intrathecal opioids, the pharmacologic properties of epidurally administered opioids reflect the extent of the hydro- versus lipophilicity of the specific opioid: lipophilic opioids (fentanyl and sufentanil) have a shorter onset and duration of action whereas hydrophilic opioids (morphine, hydromorphone) have a delayed onset and prolonged duration of action (and certain side effects such as delayed respiratory depression). 2. Epidural opioids exhibit the same sid

KEY POINTS 1. Anatomic and physiologic differences in neonates and young infants necessitate lower doses of epidural local anesthetics and intravenous opioids up to 4 to 6 months of life. 2. Behavioral or physiologic measures of pain intensity are available for infants and children unable to selfreport their pain. 3. Aspirin is not routinely used for postoperative pain control in children because of an association with Reyes syndrome, a potentially fatal hepatoencephalopathy. 4. Epidural ana

KEY POINTS 1. Chronic pain after surgery is common. 2. Risk factors include patients with preexisting pain, psychosocial factors, age, gender, and possibly genetic susceptibility. 3. CPSP can be prevented using good surgical technique (avoiding nerve damage and using minimally invasive techniques) and aggressive multimodal analgesia starting immediately prior to surgery. 4. Future strategies should include more consistent use of multimodal analgesia across surgical populations and screenin

KEY POINTS 1. Pain is frequent during pregnancy and lactation. Many women suffer from pelvic girdle pain and back pain. 2. Physiologic changes during pregnancy may alter drug pharmacokinetics and pharmacodynamics. 3. Most drugs cross the placenta and cross into breast milk. 4. Drug effects on the fetus may be direct or indirect (effect on the mother). 5. Efforts should be made to minimize maternal exposure to drugs during pregnancy and lactation. 6. Possible adverse effects of in utero dr

KEY POINTS 1. The incidence of migraines in females increases into the early forties. 2. Consuming more than about 400 mg of caffeine per day can predispose to chronic migraines. 3. Basilar migraine can present with mental status changes. 4. Vasoconstrictor drugs, such as triptans, are contraindicated in basilar migraine. 5. Analgesic overuse (use of analgesics 10 or more days per month) can lead to chronic daily migraine. 6. The trigeminal autonomic cephalalgias include cluster, hemicr

KEY POINTS POSTDURAL PUNCTURE HEADACHE 1. The crucial components of PDPH are a history of dural/ arachnoid puncture and a postural bilateral headache on examination. 2. The occurrence of headache after dural/arachnoid puncture is not directly related to the amount of CSF leaked or the subarachnoid pressure. The headache may be secondary to a sudden alteration in CSF volume and subsequent cerebral vasodilatation. 3. Concomitant intracranial pathology may be present in patients with PDPH. The

KEY POINTS 1. Cervicogenic headache is referred pain from cervical structures innervated by the upper three cervical nerves. 2. The diagnostic criteria of cervicogenic headache, according to the International Headache Society, include the following: (1) pain referred from a source in the neck, (2) evidence of a disorder within the cervical spine or soft tissues of the neck as a cause of the headache, (3) abolition of the headache following a diagnostic block, and (4) resolution of the pain

KEY POINTS 1. Diagnosis guides management; an algorithmic approach is necessary to treat patients with headache and facial pain. Accurate diagnosis requires knowledge of the ICHD-2 criteria, and stepwise elimination of primary and secondary headaches. 2. Red flags in the history and physical examination require further investigation. 3. Treatment centers on preventive and abortive strategies. The appropriate timing for interventional treatment needs to be measured against the severity of th

KEY POINTS 1. Epidural steroid injections are indicated in patients with lumbosacral radiculopathy. The beneficial effect of the steroids is secondary to its anti-inflammatory effect and specific antinociceptive effect. The antiinflammatory effect is probably related to inhibition of phospholipase A2. Local application of methylprednisolone inhibits the transmission of impulses through the C-fibers but not in the Ab fibers. 2. Epidural steroids are more effective in patients with acute lumb

KEY POINTS 1. Sacroiliac joint pain can be caused by intra- and extraarticular causes. 2. Several tests confirm the diagnosis of SI joint syndrome. An analgesic response to an SI joint injection is the most accurate means to diagnose a painful SI joint complex. 3. Corticosteroid injections may provide short or intermediate-term relief in well-selected patients but evidence for long-term benefit is mainly anecdotal. 4. There is moderate evidence supporting RF denervation to treat pain arising

KEY POINTS 1. Myofascial pain syndrome is a type of regional soft tissue pain syndrome involving muscles of the trunk and extremities. 2. Although myofascial pain may generalize, it remains distinct from fibromyalgia. 3. Hyperirritable loci of trigger points have been found to contain vasoactive mediators, algogenic neurotransmitters, and inflammatory mediators. 4. Excessive acetylcholine leakage has been hypothesized to contribute to dysfunctional motor end plates, creating the sustained

KEY POINTS 1. Fibromyalgia can be considered a discrete condition as well as a construct to help explain how/why individuals have multifocal pain and other somatic symptoms in spite of the lack of nociceptive input (i.e., peripheral damage/inflammation) that adequately accounts for the pain. 2. The primary abnormality identified to date in FM and related pain syndromes is an increased gain or volume control in CNS pain processing (i.e., secondary hyperalgesia/allodynia). 3. It is likely that

KEY POINTS 1. Herpes zoster (shingles) is caused by reactivation of the varicella-zoster virus (VZV), which establishes latency in sensory ganglia after primary infection (chicken pox). 2. The characteristic unilateral dermatomal vesicular rash of herpes zoster heals within 2 to 4 weeks and is accompanied by pain in the majority of patients. 3. Older age is associated with an increased risk of herpes zoster because of an age-associated decline in VZVspecific cell-mediated immunity. 4. Antivi

KEY POINTS 1. Central pain states are common sequelae of SCI and stroke. 2. Pathophysiology of central pain is not understood. 3. Alterations in several neurotransmitters occur, including glutamate, GABA, norepinephrine. 4. Involvement of the spinothalamocortical pathway is strongly supported by animal models, but the precise pathway in humans is unknown. 5. The three components of central pain (steady dysesthetic, intermittent neuralgic, and evoked) must all be treated. In central pain o

KEY POINTS 1. Chronic pelvic pain (CPP) usually persists for more than 6 months. Even after a thorough evaluation, the etiology of the pain may remain obscure, and inconsistency remains in the pathology of various disorders and pain. 2. The prevalence of female pelvic pain is estimated to be one in seven women of reproductive age. Internationally, the prevalence of CPP is equivalent to that of asthma, back pain, or migraine. 3. Both diagnosis and management of these patients require good in

KEY POINTS 1. Neuropathic pain arises from disorders of the peripheral nervous system. Although there are many etiologies of peripheral neuropathy, not all of which always produce pain, the most prominent and common is diabetic neuropathy. 2. Many mechanisms have been proposed for the pain that occurs in peripheral neuropathic states. They can be categorized into peripheral and central. Peripheral mechanisms proposed include: formation of ectopic foci, formation of ephapses (unlikely), rele

KEY POINTS 1. The Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials (IMMPACT) group recently recommended outcome domains and measurement tools for research on pediatric acute and chronic pain. 2. The management of complex regional pain syndrome includes physical therapy, regional blocks, pharmacological management, and psychological interventions. 3. Several characteristics of headache suggest a pathological or more serious etiology. 4. The management of headache in

KEY POINTS 1. Neurostimulation mechanisms of analgesia are poorly understood, but it appears to interrupt transmission of nociceptive signaling via interneural inhibition at the substantia gelatinosa and modulation of spinal cord neurotransmitters. Neurostimulation is effective for many neuropathic pain conditions but careful patient selection with a multidisciplinary perspective is valuable to ensure higher rates of successful implantation. 2. There are multiple choices for leads and power g

KEY POINTS 1. Peripheral nerve stimulation systems can be trialed prior to permanent implantation with an ultrasoundguided placement. 2. The long-term safety of permanent implants of percutaneous electrodes is not yet known with certainty. 3. Although percutaneous ultrasound-guided PNS is similar to peripheral nerve catheter placement for perioperative nerve blockade, the larger size of the needle and potential areas of placement are quite different. These differences mandate a very strict an

KEY POINTS 1. Intraspinal therapy restricts drug effects to regions associated with the source of the nociceptive input. 2. Morphine and hydromorphone are well suited for intrathecal use in view of their hydrophilicity and slow absorption from the cerebrospinal fluid. Morphine, hydromorphone, and ziconotide are the first-line agents in intrathecal drug therapy. The inclusion of ziconotide as a first line drug is secondary to the randomized, double-blind placebo-controlled studies showing its

KEY POINTS 1. Osteoporosis and VCFs are a significant public health concern with high morbidity. 2. Vertebral augmentation is a safe and efficacious procedure for treatment of painful VCFs that fail conservative therapy. 3. Proper technique and vigilance can help avoid serious complications and the procedure should only be performed by those trained and experienced with the procedure. 4. Both kyphoplasty and vertebroplasty are efficacious for pain relief, but recent double-blind, placebo-

KEY POINTS 1. Successful treatment of cancer pain is possible most of the time. 2. The cancer pain syndrome should be determined: nociceptive, neuropathic, or mixed. 3. Cancer pain should be assessed and managed within the dimensions of suffering that a patient and his or her family experience: physical, psychological, social, and spiritual. 4. Daily evaluation includes an assessment of the location, type, temporal profile, and severity of each significant pain. 5. The World Health Organiza

KEY POINTS 1. All physicians, regardless of specialty, are responsible for care of patients with life-threatening illnesses. 2. Assessment of pain and other symptoms at end of life requires knowledge of common syndromes, as well as skill to conduct a thorough history and physical examination, with particular attention to the neurologic evaluation. 3. Complex pain syndromes require novel drug therapies, in addition to standard nonopioid, opioid, and adjuvant analgesics. 4. Adequate pain contr

KEY POINTS 1. Neurolytic blocks of the sympathetic axis are an important adjunct to pharmacologic therapy for the relief of severe visceral pain experienced by cancer patients. The goal of performing these blocks is to maximize the analgesic effect of opioid and nonopioid analgesics while reducing their dosage to alleviate untoward side effects. 2. Neurolytic celiac plexus block for patients with pancreatic cancer pain results in excellent analgesia, reduced opioid utilization, and decreased

KEY POINTS 1. Neurolytic therapy should only be considered after other pain modalities have been exhausted. These therapies are usually reserved for patients with terminal disease. Very clear therapeutic goals and limitations need to be communicated between patient and practitioner. 2. Neurolytics can offer patients the ability to decrease their systemic pain medications that can improve their quality of life and allow them the opportunity to clearly communicate with loved ones during diffi

KEY POINTS 1. The C4 nerve root contributes to about two-thirds of brachial plexuses and shifts the plexus cephalad (prefixed plexus). The T2 nerve root contributes to about one-third of plexuses and shifts the plexus caudad (postfixed plexus). 2. The minimum distances from the skin to the C6 vertebral foramen and to the spinal cord are 23 mm and 35 mm, respectively, implying that inserting a needle for interscalene brachial block to a depth of less than 25 mm may result in nerve root contact

KEY POINTS 1. There were no currently described techniques of brachial plexus block that rely upon blockade at the level of the divisions of the plexus until the advent of US guidance. 2. It has been demonstrated that the capacity of the axillary perivascular sheath is 42 ml. 3. Axillary and infraclavicular blocks of the brachial plexus are appropriate for surgeries of the upper extremity from the elbow to the fingers. 4. Paresthesias occur in up to 40% of cases of axillary perivascular

KEY POINTS 1. When compared to epidural analgesia for thoracotomy, paravertebral blocks with catheters provide equipotent analgesia with a lower incidence of pulmonary complications, hypotension, urinary retention, nausea and vomiting, and failure rate. 2. A single injection of 15 ml in a thoracic paravertebral space can be expected to provide analgesia over 3 to 4.6 dermatomes, with a preferential caudad spread of injectate. 3. Ultrasound imaging usually underestimates the distance to the tr

KEY POINTS 1. The sciatic nerve is the largest nerve in the body and innervates the entire leg below the knee and the foot, except for its medial aspect, which is innervated by the saphenous nerve. Its two divisions, the tibial nerve and the peroneal nerve, while separate entities, are covered by a continuous connective tissue sheath. 2. The sciatic nerve can be blocked at different levels along its entire length as it exits the pelvis at the greater sciatic foramen to its termination in the p

KEY POINTS 1. Some 50% of DVTs after total joint surgery begin intraoperatively; the highest incidence occurs during surgery and the first postoperative day. Almost 75% of DVTs develop within the first 48 hr after surgery. 2. Case reports of intraspinal hematoma after aspirin and NSAIDs had complicating factors such as concomitant administration of other anticoagulant, epidural vascular abnormalities, and technical difficulties. The intake of different antiplatelet medications has been identif