Management of Acute Pain in Amputation

Joel Castellanos

Christopher Reid

John J. Finneran

Introduction

Amputation is a common procedure with ˜185 000 people undergoing amputations annually in the United States alone. Adequate pain management can be difficult with patients who have undergone amputations because of the extent of tissue injury altering the perception not only at the peripheral level but also at the central level as well. The combination of direct tissue (peripheral nerves, soft tissue, and bone) injury as well as central sensitization results in a varied nociceptive and neuropathic pain presentation that requires a multimodal and individualized treatment protocol for optimal pain management.

Epidemiology

Amputees Per Year

Every year, ˜185 000 people undergo amputations in the United States.¹ The main causes of lower extremity amputations are vascular disease (including diabetes and peripheral arterial disease) and trauma, which when combined account for almost 98% of amputations. Cancer follows these two causes as the third leading cause of lower extremity amputations. Trauma accounts for the overwhelming majority of upper limb amputations (77%) followed by congenital limb deformities and cancer (6%).¹

Total Amputees

There are currently ˜2 million people who are living with an amputation in the United States. Most patients suffer from postoperative residual limb pain, and ˜10% of patients having persistent limb pain.² In the postoperative period, incidence of phantom sensation is 84% and 90% at 6 months. The incidence of phantom limb pain is higher in patients undergoing an upper extremity amputation compared to a lower extremity amputation.² A study done in the Netherlands in upper limb amputees found significant associations between phantom limb pain and phantom sensations as well as between phantom pain and residual limb pain.³

Classification of Postamputee Pain

Residual Limb Pain

Residual limb pain, or “stump pain,” refers to pain in the remaining parts of the amputated extremity. The residual limb pain can be accompanied by hyperalgesia, an increased sensitivity
to painful stimulus, and/or allodynia, pain elicited from nonpainful stimuli. There are several possible etiologies of residual limb pain, which will be covered in this section.

Postoperative pain

Immediately after an amputation, postsurgical wound pain is most prevalent. The pain is often described as constant, aching, throbbing pain with associated erythema and edema; this reflects the postsurgical inflammatory process that is occurring. This pain is primarily a nociceptive process; however, it can coexist with neuropathic pain processes as well.

In general, acute postoperative pain gradually dissipates over 14-21 days. In some patients, this pain transforms into a persistent residual limb pain. This occurs in ˜10% of patients.² This transition from acute to chronic pain in the residual limb can occur for a variety of reasons. These include infection, vascular claudication secondary to inadequate blood supply; wound failure; heterotopic ossification; seroma, hematoma, or neuroma formation; and/or poorly fitting prosthesis.

Infection

Infection is not uncommon after amputation, especially in patients who are undergoing amputation secondary to vascular complications. Risk factors for infection after an amputation include below vs above knee amputation, presence of diabetes or vascular disease, and poor nutrition status.⁴ Differentiating infection from routine postoperative inflammation can be difficult, but the presence of worsening pain, purulent exudate, wound failure, and prolonged erythema and edema are clinical signs that suggest infection. Uncontrolled residual limb infections can quickly become life-threatening with the development of sepsis and requirement for debridement, surgical revision, and potentially loss of more residual limb to preserve life. Following complete blood count, inflammatory markers (eg, erythrocyte sedimentation rate and C-reactive protein levels), blood and wound cultures, and imaging should also be used to help differentiate postoperative inflammation from developing infection.

Neuroma

After a peripheral nerve is injured through trauma, ischemia, or transection, an inflammatory response occurs. Although the exact pathophysiology of neuroma formation is not well understood, neuroma formation occurs as the proximally cut nerve ends are inhibited from reconnecting to their distal end organs by scarring and fascicular escape.⁵ A neuroma develops from uncontrolled axonal growth and is intertwined with support cells such as myofibroblasts, Schwann cells, and endothelial cells. Up to 60% of patients who⁶ have suffered a peripheral nerve injury may develop a painful neuroma.

Phantom limb pain

Phantom limb pain is a neuropathic pain that occurs in 45%-85% of patients who undergo amputation.⁴,⁷ The pain is located in the area of the limb that is no longer present and may become a disabling condition in many patients. The exact pathophysiology of phantom limb pain is yet to be discovered but likely is caused by a combination of damage to the peripheral nerves as well as maladaptive neuroplasticity of the spinal cord and somatosensory cortex.

Management of Postamputation Pain

Optimal pain control is best achieved through multimodal analgesia. This concept was originated by Kehlet and Dahl for postoperative pain control, but now is the underpinning of both acute and chronic pain management.⁸ This approach may consist of interventional approaches and/or infusions targeted neuraxial or peripherally, medications of differing classes, physical therapy, and other adjunct treatment approaches.

Presurgical Counseling and Pain Psychology, Rehab Counseling

Undergoing an amputation has a profound effect on not only a persons’ function but also psychosocial status. When able, presurgical amputation counseling by certified prosthetist or physiatrist to help set reasonable postoperative expectations regarding pain as well as postoperative timeline to prosthesis. In the case of traumatic or unplanned amputation, these issues should also be addressed postoperatively. Pain psychology consultation should be in place as well provide the patient coping mechanisms to help manage pain as well as to help with adjustment to limb loss.⁹

Postoperative Pain Management

Acute postoperative management of patient undergoing an amputation surgery begins with intravenous patient-controlled analgesia. This allows patients to titrate the dose of opioid medication, typically fentanyl or hydromorphone, to adequate pain control. As acute postsurgical inflammation begins to subside, calculating the daily oral morphine equivalents required for adequate pain control through the intravenous patient-controlled analgesia can be converted to oral opioids. Oral opioids can be supplemented with neuropathic pain medications such as anticonvulsants (gabapentin, pregabalin, valproate) and antidepressants (amitriptyline, nortriptyline, duloxetine). Modalities can also be used to help with pain control. These include ice, heat, soft tissue mobilization, and transcutaneous electrical nerve stimulation. Physical therapy and occupational therapy can also help with pain control with progressive mobility, motor imagery, and mirror box therapy, which has been shown to help with both residual and phantom limb pain.¹⁰

Regional Anesthesia

Postoperatively, amputee patients have both peripherally and centrally acting pain processes caused by nociceptive pain input from the site of surgery as well as the dissonance between the physical body and the still existing motor and sensory cortex of that respective limb that was amputated.¹¹ Regional anesthesia may interfere with the propagation of the peripheral painful stimuli to the brain and therefore is a potential prophylactic and therapeutic modality.¹²

Various regional anesthesia techniques have been studied for the treatment of pain related to amputation surgery. An early tenet was the use of epidural analgesia preoperatively. This modality initially was found to decrease phantom limb pain incidence, but the effect has proven to be inconsistent.¹³ The use of epidural analgesia does have utility in improved pain control in the acute postoperative phase. A recent study examined the effect of preemptive epidural anesthesia (bupivacaine and fentanyl) 48 hours prior to surgery, intraoperative epidural anesthesia, and postoperative epidural analgesia for 48 hours after surgery. This long duration epidural analgesia reduced the incidence of phantom limb pain at 6 months.¹⁴

Only gold members can continue reading. Log In or Register to continue