Pain Management (also see Chapter 72 and Chapter 73 )

Trauma patients present significant pain management challenges to the clinician because of multiple sites of injury, protracted episodes of care, complicating psychological and emotional issues, and frequently, previous or

TABLE 63-17 -- Criteria for operating room or postanesthesia care unit extubation of trauma patients

Mental Status

Resolution of intoxication

Able to follow commands

Noncombative

Pain adequately controlled

Airway Anatomy and Reflexes

Appropriate cough and gag

Ability to protect airway from aspiration

No excessive airway edema or instability

Respiratory Mechanics

Adequate tidal volume and respiratory rate

Normal motor strength

Required FIO2 < 0.50

Systemic Stability

Adequately resuscitated (see above)

Small likelihood of urgent return to the operating room

Normothermic, without signs of sepsis

ongoing substance abuse. As with pain management practice in other disease states, trauma patients are frequently undertreated, which can be a significant source of dissatisfaction. Because trauma patients run the gamut of physiology from healthy young athletes to the debilitated elderly, an anesthesiologist providing pain management for trauma patients must be prepared for a wide range of needs.

Pain in general and pain from traumatic injury in particular are self-perpetuating phenomena. Increased receptor number and activity in response to an ongoing painful stimulus lead to a "wind-up" of pain over time.^[220] Successful analgesia requires interruption of receptor upregulation as soon as possible after injury, with maintenance of relief thereafter. Early or even preemptive treatment of pain has been shown to greatly reduce analgesic requirements over time.^[221] Individual patients will have widely variant requirements for pain medications, so induction of analgesia must be carefully titrated, ideally in a closely monitored environment such as the PACU. Rapidly acting intravenous agents administered in small doses at frequent intervals until pain relief is achieved are recommended so that the practitioner can determine the patient's basal requirement for analgesic medications. Hypotension developing in response to the appropriate administration of analgesics most commonly indicates hypovolemia and should lead to an investigation for occult hemorrhage while further resuscitation occurs.

The need for analgesic medication and the duration of analgesic therapy will be minimized if a comprehensive emotional support system is available to the patient. Trauma, because of its unexpected nature, carries with it a strongly negative psychological overlay that can have a profound effect on how anatomically based pain is perceived by the brain^[222] and on how the patient reacts. After an injury the patient may have legal, financial, and family-based concerns, without the ability to immediately address them. The availability of counselors—religious, financial, or legal—who can help the patient and family

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The need for analgesic medication is also influenced by the schedule of physical therapy prescribed for the patient. In general, the more active a patient can be after traumatic injury, the lower the risk of pulmonary complications, venous thrombosis, and decubitus ulcers. Though painful in the short term, the sooner the patient is mobilized, the lower the analgesic requirements in the long-term. Early mobilization demonstrates to the patient the "path to recovery" and contributes to an improved emotional state. One of the goals of analgesia, therefore, is the provision of adequate medication to facilitate physical therapy, without so sedating patients that they are unable to participate.

The choice of medications should follow the World Health Organization recommendations for "stair step" therapy,^[224] beginning with the safest drugs and titrating each agent upward until the recommended maximum dose is reached before adding a new agent. In acutely traumatized patients, therapy will begin with a maximal dose of acetaminophen, then include a nonsteroidal anti-inflammatory drug (NSAID), then a short-acting narcotic, and then a long-acting narcotic. Acetaminophen is very well tolerated by most patients in doses up to 3 to 4 g/day, but it should be avoided in patients with hepatic or renal failure. NSAID therapy begins with ketorolac by injection during the perioperative period, transitions to oral agents when gastrointestinal function is restored, and should then continue on a regular basis until the patient's pain is completely resolved. NSAIDs may cause gastrointestinal upset, gastritis, and ulceration and should be taken with food whenever possible. Prophylaxis against peptic ulceration is indicated in most trauma patients in any case and can help reduce the potential for gastrointestinal distress from NSAIDs. Short-acting oral narcotics work within 30 minutes of ingestion and provide relief for 3 to 4 hours. Many popular commercial preparations combine short-acting narcotics with acetaminophen for ease of use; the recommended dose of these drugs will typically provide the maximum recommended dose of acetaminophen. If additional analgesia is required, the noncombined form of the narcotic can be titrated upward, although this is usually an indication to start or increase the dose of a long-acting preparation. Long-acting narcotics include oral methadone, sustained-release preparations of morphine, and transdermal fentanyl. Approximately 80% of the patient's narcotic requirement should be administered in the form of long-acting medications, with short-acting preparations available to treat episodes of breakthrough pain.^[225]

Narcotic preparations are the last line of oral analgesic therapy because they have a narrow therapeutic margin and a substantial potential for addiction and abuse. All narcotics are dose-dependent respiratory depressants, and too rapid administration or unanticipated systemic accumulation can lead to respiratory arrest. Agonist-antagonist narcotics reduce this risk but do not provide adequate relief for most seriously injured patients. The potential for addiction and abuse of narcotics after their appropriate prescription for treatment of traumatic pain is controversial. Any patient taking a long-acting narcotic preparation will become physiologically dependent on the drug, so it must be tapered off as healing occurs and pain subsides (e.g., a reduction in morphine dose of 15 mg every other day until weaned completely off), or symptoms of narcotic withdrawal will occur. The development of an addiction that persists beyond the need for analgesic medication is the result of complex genetic and emotional issues and is difficult to predict prospectively. The anesthesiologist should be aware of the potential for addiction to occur and be prepared to offer appropriate treatment, including referral to a substance abuse specialist, should addiction develop.

The gastrointestinal tract is the preferred route of administration for analgesic medication because it offers gradual and predictable absorption. A patient who is nil per os (NPO) must usually be managed with intravenous medication. Morphine, fentanyl, and hydromorphone are common choices; meperidine should be avoided because of the potential for accumulation of active metabolites and the development of seizures.^[226] The preferred route of intravenous administration is by a patient-controlled analgesia infusion device (PCA) that allows for immediate delivery and self-titration of pain medication. Clinical studies have shown that analgesic requirements are lower and patient satisfaction higher with PCA than with medications titrated and administered by the nursing staff.^[227] Overdosing is extremely rare because of the self-regulating nature of the device; as analgesia is achieved, the patient will typically become somnolent and stop taking additional doses. Transition from PCA to oral medication is usually straightforward because the patient's requirement for analgesics will have been established; a day of overlapping oral and PCA therapy is recommended to ease the transition.

Neuropathic pain arises after direct injury to a major sensory nerve and is common after spinal cord trauma, traumatic amputations, and major crush injuries. Neuropathic pain is characterized by burning, intermittent electrical shocks, and dysesthesia in the affected dermatomal distribution. It is important to identify neuropathic pain because it responds poorly to the analgesics used for somatic pain. This diagnosis should be considered whenever pain control is poor or the patient has a rising requirement for medications unexplained by the anatomic injuries. First-line therapy for neuropathic pain has been revolutionized by the widespread use of gabapentin, an antiepileptic drug with very strong specificity for this problem.^[228] Gabapentin therapy is typically initiated at a dose of 200 mg three times daily with daily titration upward to a maximum of 2 to 3 g/day. If neuropathic pain persists, selective regional anesthesia or analgesia may be indicated in an effort to "break the cycle" of spinal cord receptor recruitment.^[229]

Regional analgesia provided through an epidural or brachial catheter should be considered for any trauma

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The use of adjuvant sedative and anxiolytic medications is common in the trauma population, but the potential for polypharmacy complications must be recognized. One physician only, ideally the anesthesia pain consultant, should have the responsibility for all sedating medications given for any purpose so that appropriate titration and patient monitoring can take place. A particularly common and problematic issue is raised by a patient with painful injuries who also requires prophylaxis for delirum tremens because of a history of alcohol abuse. Benzodiazepine administration on a fixed schedule is indicated for this condition, but it may produce oversedation and respiratory arrest when combined with narcotics administered for analgesia. Any patient receiving benzodiazepines "around the clock" should be closely monitored for signs of increasing sedation and the dose decreased or withheld in response.