CHAPTER 17 Pain Management in the Head and Neck Patient
Pain Defined
The International Association for the Study of Pain defines pain as “an unpleasant sensory and emotional experience associated with actual or potential tissue damage or described in terms of such damage.”1 Pain can be broadly categorized as either acute or chronic. Acute pain is a predicted response to a noxious mechanical, thermal, or chemical stimulus such as trauma or surgery. It is for an acute period of time and is often responsive to appropriately adjusted analgesics.2 Pain is defined as “chronic” when it persists for at least 3 to 6 months or lasts longer than the time in which healing would normally occur.2
Measurement of Pain
Evaluation of pain in an accurate and reliable way is a critical component of patient assessment. The visual analog pain scale and verbal numeric scales are frequently used as pain assessment tools. The visual analog pain scale is usually presented as a 10-cm line anchored by the verbal descriptors “no pain” and “worst imaginable pain.” Both of these scales have been shown to have high sensitivity in the measurement of pain intensity, a reflection of their ability to detect change.3
Inadequate assessment of pain, lending to inadequate provision of pain relief, is a prevalent barrier to pain management in cognitively impaired adults with either acute or chronic pain. For some cognitively impaired adults, scales such as the Faces Pain Scale Revised (FPS-R), Verbal Descriptor Scale (VDS), Numeric Rating Scale (NRS), and Iowa Pain Thermometer (IPT) can be used and have been shown to have low failure rates and high preference evaluations.4 Evaluation of pain in the severely cognitively impaired patient may be challenging. For the nonverbal patient, observation of behavior is the best approach for pain assessment.5
Pain assessment is especially difficult in children with cognitive impairment. The Face, Legs, Activity, Cry, Consolability (FLACC) tool assigns a value of 0 to 2 for each variable, for a total FLACC score of 0 to 10. This tool has been shown to facilitate reliable and valid observational pain assessment in children with cognitive impairment who cannot report their own pain.6 It uses pediatric nurses’ clinical judgment to determine analgesic choice based on their determination of the score.7 The FLACC pain assessment tool is also appropriate for preverbal children experiencing pain.7
Acute Pain Management
Epidemiology
Approximately 72 million surgical procedures are performed in the United States annually, 3.5 million (4.9%) of which are related to the ear-nose-throat (ENT) specialty. Three million (86%) otolaryngologic procedures are performed in an ambulatory setting. The growth of ambulatory surgery has represented one of the most significant recent changes in surgical practice.8
Patient Satisfaction
Potential benefits of providing adequate postoperative pain relief include improved patient comfort, increased recovery speed, reduced postoperative morbidity, and shorter hospital stay.9,10 Poorly controlled postoperative pain increases morbidity and mortality, and decreases quality of life.11
Factors contributing to patient satisfaction with postoperative pain management include how seriously the medical staff takes the complaint of pain, the frequency of breakthrough pain episodes, and actual pain intensity. Patient dissatisfaction is increased if a request for analgesics is followed by inadequate pain treatment. There is not a direct correlation between pain intensity and patient satisfaction. For example, patients who have the opportunity for self-administration of analgesics, as with PCA, report a feeling of autonomy and security, and improved satisfaction compared with those treated with as-needed nurse-administered analgesia.12 Health care provider knowledge regarding dosing and duration of action of opioids also impacts the quality of postoperative pain management.13 Therefore, patients treated with standardized pain management by an acute pain service are more likely to report being satisfied with their postoperative pain management.14
When evaluating the desirability of the outcome of postoperative pain management, patients place similar importance on analgesic efficacy and the type and severity of the side effects experienced. Common side effects of opioid therapy include sedation, respiratory depression, nausea or vomiting, mental confusion or dizziness, mood change, nightmares or hallucinations, and sleep disorders. Additionally, when comparing intravenous (IV) PCA in the hospital to oral opioids in the hospital versus oral opioids at home, the site of delivery, as well as mode of delivery for opioid administration appear to be of less importance to patients than pain relief and side effects. Patient variability is high regarding willingness to trade pain efficacy for different or milder side effects. These factors may assist with selecting pain treatments that match the patient’s needs, thereby improving compliance and patient satisfaction, if pain treatment plans are individualized to each patient and clinical setting.15
Opioid Addiction versus Tolerance
A barrier to effective management of postoperative pain is the concern that opioid use will result in addiction. Approximately 10% of patients report preoperative or postoperative fear of addiction from postoperative analgesics. Physician or patient fear of opioid addiction in the acute postoperative setting may prevent needed treatment of pain. Tolerance is loss or reduction in the normal response to a drug over time. In contrast, addiction is characterized by behaviors including impaired control over drug use, compulsive use, continued use despite harm, and craving.16 In the absence of history of addiction, it is rare to develop opioid addiction in the context of acute pain treatment.17
Patient-Controlled Analgesia
Parenteral administration of opioid analgesics via IV PCA is commonly used in the immediate postoperative setting. PCA benefits potentially include improved pain control and patient satisfaction, as well as improved nursing satisfaction and efficiency.18 The degree of pain relief achievable and the amount of analgesic used with PCA, relative to conventional methods of administration (intramuscular, subcutaneous, oral, continuous, IV intermittent), is variable. Patients who are not satisfied with PCA therapy may either fear opioid overdose or addiction.19,20 It is reasonable to assume that provision of analgesics in a dose and interval tailored to an individual’s specific needs would result in good outcomes regardless of the specific technique used. The choice of opioid should be made based on the patient’s clinical history and drug availability. Choice of opioid used with PCA does not appear to affect patient satisfaction.21
Using PCA opioids to control pain may be complicated by nausea and vomiting, pruritus, respiratory depression, sedation, confusion, urinary retention, and drug-induced ileus. These adverse effects are characteristic of opioid receptor agonists administered by any route or method of delivery. Comparing the incidence of respiratory depression with PCA and conventional opioid analgesia administration is difficult to study. This is in part due to difficulty in defining an incident of respirator depression as well as the low incidence of occurrence with a resulting need for a large number of patients to show a significant difference.22 It should be noted that after IV administration, morphine slowly crosses the blood-brain barrier, resulting in delayed onset of analgesic and ventilatory depressant effects. This necessitates added caution when morphine is used for PCA, particularly in the setting of renal insufficiency, which prolongs morphine elimination.23,24
To use PCA opioid for pain control, choices must be made regarding selection of drug, demand (bolus) dose, time interval (frequency), and whether to use a basal (continuous) setting and the maximum dose allowed. Table 17-1 lists equianalgesic doses of commonly used opioid analgesics. The typical starting dose for IV PCA would be 1 mg morphine or 0.5 mg hydromorphone, with a 10-minute lockout interval between doses, and no basal infusion. Meperidine is not recommended due to risk of central nervous system toxicity from its metabolite normeperidine.25 A lockout period helps prevent overdosage caused by overzealous demands for more analgesia. The lockout time should be long enough for the previous dose to have an effect. In view of the high intrinsic potency of fentanyl, it may be reasonable to use a longer lockout period. Regular review is needed in every case to ensure that pain relief is safe and adequate.
Basal (continuous) infusion of opioid, in addition to intermittent PCA bolus doses, is rarely indicated for acute pain in opioid-naïve patients. Use of a basal opioid infusion does not decrease the number of patient-activated PCA opioid doses, so the total dose of opioid is increased.26 Opioid basal infusion increases risk of opioid adverse effects, including respiratory depression. In our practice, we seldom use a basal opioid infusion except when using PCA in patients with chronic pain and opioid tolerance. For example, if a patient on long-term oral opioid therapy for chronic pain requires surgery (and will not be able to take usual oral medication for some period), a basal opioid infusion may be used to administer opioid equivalent to the chronic opioid dose, with supplemental PCA bolus opioid titrated to control acute pain.
Perioperative Considerations for Older Adults
The number of surgical patients older than 65 years of age is increasing, with the fastest growing segment being those older than age 85 years. Due to increased prevalence of comorbidities, older adults have increased risk for postoperative complications and surgical mortality, mainly due to cardiac and pulmonary dysfunction.27 Primary concerns regard perioperative effects on cardiac, pulmonary, cerebral, and cognitive function. Postoperative opioid requirements decrease with increasing age, due to age-related changes in the metabolism and clearance of these analgesics.28 Effective analgesia promotes early ambulation, shortened hospital stay, and reduced health care costs.29 Barriers to adequate pain control in older adults include concerns about drug overdose, adverse effects, and addiction. Also, the increased prevalence of abnormal mental status in older adults complicates perioperative care, including pain management, in this group.30
Perioperative Considerations for Patients Receiving Chronic Opioid Therapy
Surgical patients may vary greatly in their intraoperative and postoperative opioid requirements. Patients with a history of chronic opioid use often become opioid tolerant, creating a situation where standard treatment dosages and strategies may be ineffective. Patients with a history of chronic opioid consumption should be expected to require more opioid medication postoperatively than opioid naïve patients. Because tolerance develops to opioid adverse effects, opioid tolerant persons may experience fewer side effects, such as nausea, pruritus, and sedation. Despite receiving appropriately titrated, increased doses of opioid for acute pain, patients with a history of chronic opioid use tend to report higher pain scores.31
Considerations for NSAID Use for Postoperative Pain
The use of NSAIDs after surgery, such as tonsillectomy, is controversial. NSAIDs play an important role as adjuvant analgesic agents to opioids, and may improve pain control and/or reduce opioid requirements (and thereby reduce opioid adverse effects). Potential complications of NSAID use include postoperative hemorrhage secondary to impairment of platelet function, renal insufficiency, and acute gastric ulceration. Postoperative hemorrhage is a particular concern following tonsillectomy, with an incidence of 1.5% to 5%, with delayed hemorrhage (>24 hours) being more common than primary hemorrhage (<24 hours).32 A recent study of pediatric patients undergoing tonsillectomy and adenoidectomy revealed no difference in postoperative bleeding rate in patients provided perioperative ibuprofen versus control, concluding that ibuprofen is not contraindicated in this setting and should be used in the control of postoperative pain if it is indicated.33 Although post-tonsillectomy hemorrhage is a severe complication, if further research supports that NSAID use does not increase the risk of hemorrhage in this setting, more widespread use of NSAIDs would be indicated to improve postoperative pain control.
Preemptive Analgesia
Preemptive analgesia is pain treatment given before tissue injury to prevent establishment of altered central processing of afferent input from sites of injury, and thereby prevent development of pain hypersensitivity. Preemptive analgesia may reduce the magnitude and duration of postoperative pain. Emphasizing the importance of measures to reduce postoperative pain is the observation that patients with high intensity of acute postoperative pain scores demonstrate a higher risk of developing a chronic pain state.34 Preemptive analgesia can be established with local infiltration of incision sites, peripheral nerve block, or central neuraxial blockade.
Examination of preincisional and postincisional analgesic medication regimens reveals mixed results. Pharmacologic agents, such as NSAIDs, opioids, N-methyl-D-aspartate (NMDA) antagonists, and α2-receptor antagonists are effective at synergistically decreasing postoperative pain.35 However, preemptive administration of these pharmacologic agents is not of increased analgesic benefit when compared with postincisional administration.34 Gabapentin, which has been used extensively in the treatment of neuropathic pain, is a useful adjunct for the management of postoperative pain.36
Preemptive administration of peripheral local anesthetics does appear to offer an advantage over postincisional administration. Peripheral afferent neuronal signaling, which occurs during surgery, produces central nervous system excitability. When done before initiating surgery, wound infiltration with bupivacaine, in comparison to saline, has been shown to reduce plasma β-endorphin levels significantly in the first 48 hours postoperatively, indicating blockade of nociceptor input by the local anesthetic. When preincisional local anesthetic is used, lower reported pain scores and decreased self-administered pain medications by patients is also observed.37 Preincisional infiltration of local anesthetic and general anesthesia for pediatric tonsillectomy reduces post-tonsillectomy pain and provides a more rapid return to activity compared with use of general anesthesia alone.38
Perioperative Regional Anesthesia
Perioperative regional anesthetic techniques may allow for superior postoperative pain control compared with the use of systemic opioids and adjuvant pain medications alone, but regional anesthesia is not used widely for otolaryngologic surgery. Regional anesthesia is a potentially important therapy in otolaryngology because it may provide superior pain control, enhanced recovery, and earlier discharge, as in other areas of surgical practice.39 Examples of head and neck procedures for which regional blocks can be used, perhaps in conjunction with general anesthesia, include myringotomy and tympanostomy procedures, sinus surgery, facial plastic surgery, thyroidectomy, and parathyroidectomy.40
The trigeminal nerve, the fifth cranial nerve, supplies sensory innervation to the face as well as motor function to the muscles of mastication. It originates at the gasserian ganglion, also referred to as the semilunar ganglion, and is composed of three major branches: ophthalmic (V1) and maxillary (V2), sensory nerves, and mandibular (V3). Branches of the trigeminal nerve are potential targets for multiple regional anesthetic techniques.41
The ophthalmic division (V1) enters the orbit through the superior orbital fissure and branches into the supraorbital and supratrochlear nerves as well as the nasociliary nerve. The nasociliary branch carries sensory input to the mucous membrane of the nasal cavity as well as the frontal, sphenoidal, and ethmoidal sinuses. Although blockade of the ophthalmic division of the trigeminal nerve can be useful in sinus surgery, its proximity to vascular structures and other nerves requires a high level experience for its performance due to the increased risk of complications.42
The maxillary nerve (V2), called the infraorbital nerve once it reaches the infraorbital fossa, emerges from the infraorbital foramen. Branches of the nerve provide sensory innervation to the lower eyelid and upper lip, the teeth and gums, the nasal mucosa, the palate, and roof of the mouth. The infraorbital nerve also combines with the nasociliary branch of V1 to supply the maxillary, ethmoid, and sphenoid sinuses, as well as the nasal mucosa. The infraorbital foramen is located in a line between the pupil and the corner of the mouth just below the infraorbital rim.42 The foramen can be approached from an intraoral approach and an extraoral approach.42
Nerve innervation of the palate is mainly derived from sphenopalatine branches of the maxillary nerve, which are distributed to the roof of the mouth, soft palate, tonsil, and membrane lining of the nasal cavity. The three main divisions of the nerve, the anterior, middle, and posterior branches, supply the gums and glands of the hard palate, the uvula, the tonsils, and the soft palate.41
Mandibular (V3) nerve blocks performed before bilateral mandibular osteotomy for oropharyngeal carcinoma surgery decreases both intraoperative and postoperative opioid consumption.43 A branch of the mandibular nerve, the mental nerve, emerges at the mental foramen and communicates with the facial nerve. It emerges from the mental foramen, providing sensory input from the skin of the chin and mucous membrane of the lower lip. Blockade of the mental nerve is useful for surgery involving the lower lip and skin of the chin.41
The auricular branch of the vagus nerve joins the posterior auricular nerve, and innervates the skin of posterior auricula and external acoustic meatus. This nerve gives sensory innervation to the external auditory meatus and inferior portion of the tympanic membrane, making its blockade useful for myringotomy and tympanostomy procedures. The nerve passes through the tympanomastoid fissure, between the temporal bone and mastoid process. Blockade of the nerve can be performed by pulling the tragus forward and injecting local anesthetic posterior to the tragus.41
The cervical plexus is formed by the ventral rami of cervical nerves 1 through 4. The lesser occipital, the great auricular, the transverse cervical, and the supraclavicular nerves comprise the branches of the cervical plexus. Superficial cervical plexus block is useful for tympanomastoid surgery, otoplasty, and cochlear implant, or bilateral nerve block can be used for thyroidectomy.44
In some instances, cervical epidural anesthesia can be useful for neck surgery, where it has been described as a primary anesthetic technique for thyroidectomy.45 Cervical epidural anesthesia typically results in blockade of the superficial cervical plexus (C1-C4) and brachial plexus (C5-T2). Hemodynamics and respiratory rate must be closely monitored because hypotension and ventilatory failure can develop. Epidural analgesia and general anesthesia can be combined to minimize postoperative complications and improve postoperative pain control. A meta-analysis of eight trials comparing preemptive versus postincisional continuous epidural regimens in thoracic and abdominal surgeries concluded that epidural analgesia significantly decreased postoperative pain, but no overall improvement in pain relief was observed with preemptive continuous epidural analgesia when compared with epidural infusion initiated postoperatively.34 Only limited data are available regarding the perioperative use of epidurals in otolaryngology, and the efficacy of epidural analgesia for acute pain control in this setting needs further evaluation.
Chronic Pain
Chronic pain is one of the leading causes of health care consumption and worker disability in the developed world.46,47 Uncontrolled postoperative pain can negatively impact surgical recovery and may persist beyond wound healing due to induced changes in the central nervous system.48 It is important not only to treat pain effectively in the postoperative period, but also to be vigilant for the development of chronic pain afterward.49,50 Chronic pain should be treated with analgesics and other therapies as needed. When chronic pain persists, referral to a pain management specialist may be appropriate.
Pain Definition and Types
Chronic pain may persist indefinitely, especially when the etiology is unknown or definitive treatment is unavailable. Chronic pain may or may not be associated with a long-term medical illness and appropriate therapy may differ depending upon this distinction. Because of its emotional component, chronic pain is often associated with psychological comorbidities, including depression.51 Whether depression precedes chronic pain or chronic pain precedes depression is controversial and may vary, but the relationship between the two calls for appropriate treatment of both conditions.
Chronic pain is often a source of frustration for many medical professionals because it may be refractory to treatment. Complicating the issue is the concern of opioid addiction or abuse. Seeking drugs for pain relief is not the same as addiction. The American Pain Society defines opioid addiction as “a pattern of compulsive drug use characterized by continued craving for an opioid and the need to use it for effects other than pain relief.” Furthermore, this compulsive craving and seeking of a drug often persists despite known negative consequences. However, the taking of opioids for pain relief does not constitute addiction, regardless of the dose or duration of use. Well-established literature suggests that addiction results from the use of opioids for pain relief in very few patients.52–54
Responding to reports of inadequate pain control in the 1980s, the World Health Organization (WHO) developed a stepwise approach to treatment of cancer pain. The steps of this analgesic ladder advocate choosing analgesics primarily based upon pain intensity. According to the ladder, a patient with mild pain should be started on acetaminophen, aspirin, or one of the NSAIDs. Someone with moderate pain should receive low potency opioids (e.g., codeine, hydrocodone), whereas those with severe pain receive potent opioids (e.g., morphine, hydromorphone). Adjuvant drugs (e.g., tricyclic antidepressants, anticonvulsants) should be added to the primary analgesics at each step of the ladder as needed.55
The WHO approach also provides a five-component framework for administering analgesics. First, oral administration of analgesics is preferred (whenever feasible) because oral administration is effective, inexpensive, and easily adjusted. Second, analgesics should be given on a routine schedule, using immediate-release (IR) formulations and/or sustained-release (SR) preparations, so that pain relief is continuous. Third, the severity of the pain and its responsiveness to medication should dictate which part of the analgesic ladder should be applied. Fourth, analgesics must be appropriately titrated to each patient in order to achieve optimal pain relief. Fifth, one must vigilantly assess the degree of pain relief both before and after implementing a new pain regimen, and carefully monitor for adverse effects.2,55,56
The WHO three-step analgesic ladder has been extensively validated in several studies over the past 20 years and found to be extremely effective in cancer pain management.2,56 In one 10-year prospective study involving more than 2000 patients, 76% of patients reported good pain relief from analgesics prescribed in accordance with the WHO guidelines.2,56 Furthermore, these patients experienced a low rate of analgesic-associated complications. Another study involving 174 patients showed that oral drug therapy successfully managed pain in 89% of patients. Greater than 80% noted their pain to range between “none” and “moderate” with implementation of the WHO guidelines.2,57
Despite the efficacy of the WHO guidelines for cancer pain in general, some patients continue to have uncontrolled pain even with optimal use of systemic analgesics. When cancer pain is not controlled with systemic analgesics, a fourth step should be considered to extend the WHO ladder to encompass interventional pain therapies, such as intrathecal catheters with indwelling pumps,58 and techniques of neural blockade. For head and neck cancers this may include such interventions as trigeminal nerve blockade with local anesthetic or radiofrequency ablation. Other interventions include occipital nerve block, glossopharyngeal block, and sphenopalatine block, depending upon the location of pain.58
Even though the WHO ladder has been validated in cancer pain, it has no such validation in noncancer settings.59 Recently, several guidelines have been proposed for the use of opioids in chronic noncancer pain. These guidelines note that opioid therapy may prove beneficial for some patients and that there exists considerable personal and societal costs of chronic noncancer pain.59,60 In accordance with good medical practice, such guidelines dictate that opioid therapy should be tailored to the individual patient, and many suggest that opioid should only be prescribed after other therapies have failed.61 Opioid treatment should include thorough patient evaluation, careful formulation, and clear documentation of treatment objectives and plans, and periodic follow-up to assess treatment safety, efficacy, and patient compliance. One should carefully consider psychiatric consultation for patients with comorbid psychiatric disorders or substance abuse consultation when there is a high index of suspicion for substance abuse. Further studies are needed to substantiate guidelines for opioid use in chronic noncancer pain and to provide guidance regarding the key issue of patient selection.60–64
Considerable controversy abounds as to whether or not long-term opioid therapy is appropriate in chronic noncancer pain.62,65
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