ARTICLE IN BRIEF
✓Peripheral nerve blocks are among the advances being used in military hospitals to treat and prevent chronic pain.
They survived missiles and shrapnel and bombs but lost a piece of themselves in the Iraqi theater. The military estimates that more than 1,000 soldiers have required amputations for destroyed or diseased limbs, but these modern-day soldiers have the benefit of modern-day medicine — and many are arriving home in better shape than their counterparts from other wars, experts say. New treatments to block pain are helping soldiers recover function faster and even prevent disabling phantom limb pain.
“There is a general movement in medicine and even in military medicine that pain actually matters,” said Lieutenant Colonel Chester Buckenmaier III, MD. He directs the Army Regional Anesthesia and Pain Management Initiative at the Walter Reed Army Medical Center in an attempt to transform the military's approach to pain.
Pain management has been frozen in time since General Stonewall Jackson was wounded by his own troops during the Civil War, and he was taken by wagon off the field and given whiskey and morphine to dull his pain, Dr. Buckenmaier said.
“What an infinite blessing,” Jackson said of the treatment, according to Dr. Buckenmaier. Morphine has been the standard to treat wounds in combat ever since, but it comes with a long list of problems.
PAIN AS A DISEASE, NOT A SYMPTOM
Figure. Dr. Chester ...Image Tools
Dr. Buckenmaier is an anesthesiologist who has initiated a pain management strategy that is taking hold in military hospitals and that he hopes will be routine on the battlefield. “It's important to control pain,” he said. “Today, less than 10 percent of wounded soldiers will die, which means that more soldiers are surviving severe wounds. This is the first time in history that pain is thought of as a disease, not as a symptom.”
He is spearheading the use of continuous peripheral nerve block performed immediately after an injury. Since 2003, hundreds of men and women wounded in the Iraq war have received these nerve blocks to control pain. The physicians place the blocks and catheters with special needles and a nerve simulator that helps confirm needle position next to the target nerve.
Bruce Wilhelm was a 21-year-old Army infantry man injured after shrapnel from a rocket-propelled grenade tore through his left calf. When he arrived at a combat support hospital within an hour of the blast on Oct. 7, 2003, Dr. Buckenmaier used a peripheral nerve stimulator to create a continuous lumbar plexus block and another into the sciatic nerve. His pain score went from a 10 to a zero in minutes. The blocks delivered regional doses of local anesthesia for 16 days — and saw him through the initial debridement and five surgical procedures that culminated in an amputation of his damaged calf.
The young man, pain-free throughout the entire experience, remained in the Army for two more years and is now in training for the 2008 Paralympics.
ANESTHESIA CLOSER TO THE NERVES
Dr. Buckenmaier said that there is growing evidence that anesthesia can be delivered close to the nerves surrounding the wounded area and can block pain signals before they are transmitted to the brain. [See “References” box below.] The anesthesia, because it is localized, can be continuous without causing sleepiness. Patients often report feeling no pain, he said. They are also delivering small doses of ketamine, an NMDA-glutamate antagonist that modulates the spinal cord response to pain. Dr. Buckenmaier and his colleagues published a case report about Bruce Wilhelm in Regional Anesthesia and Pain Medicine (2005;30(2):202–205). The military is now training doctors in battle to deliver continuous peripheral nerve block as soon as possible after an injury. The sooner the pain signals are blocked, the better patients fare in dealing with injury. The patient reported only a brief and fleeting sensation of phantom limb pain, he said, adding that he believes that this aggressive response to acute pain may actually alter the story for these patients. “I believe we are preventing chronic pain syndromes,” he added. “But that needs testing.”
Dr. Buckenmaier is involved in a study to analyze the long-term consequences of peripheral nerve blocks versus the standard fare of morphine. Investigators will follow amputation patients to see which ones develop phantom limb pain and how quickly they return to routine activities.
Military doctors are also using ultrasound technology in performing the nerve blocks. Ultrasound allows them to image the nerve while they guide the needle into the target.
Mark P. Jensen, PhD, a professor in the department of rehabilitative medicine at the University of Washington School of Medicine, agrees that early and aggressive pain management is critical in trying to prevent phantom limb pain, a sensation that arises from abnormal signals to the brain. Dr. Jensen co-authored a study in The Journal of Pain that suggests that patients in intense pre-amputation pain are more likely to experience acute post-amputation pain and are also at higher risk for chronic phantom limb pain than those with less pre-amputation pain (2007;8(2):102–109). Dr. Jensen and his colleagues studied 57 patients with leg amputations after traumatic injury. Dr. Jensen said that it is possible to identify patients experiencing intense pre-amputation pain and provide aggressive pain management before and after surgery in an attempt to prevent chronic pain syndromes. Dr. Jensen and his colleagues are testing the benefits of psychological interventions, including cognitive behavior therapy, hypnosis, and neural feedback to help patients alter cerebral brain activity that triggers phantom pain.
INTEGRATED PAIN NETWORKS
The experience of pain is governed by multiple brain regions working in integrated networks. What scientists now appreciate is that how much a person hurts is not a function of the amount of damage but how that information is processed in the brain.
Dr. Jensen explained that primary information about nerve damage comes up through the spinothalamic tract into the thalamus and branches out to the sensory cortex, encoding the location of injury and the quality of the damage.
In addition, it sends out projections to brain regions that control emotional experience (how much should we worry about the injury) and to the frontal cortex, where the experience is placed in context with other events in the person's life. “You can influence how much a person says ‘ouch’ by controlling these networks,” Dr. Jensen said.
There is also a lot of cortical reorganization following an amputation, and that can also affect the experience of phantom limb pain. Vilayanur S. Ramachandran, MD, PhD, director of the Center for Brain and Cognition at the University of California-San Diego, developed a mirror technique to help amputees with phantom limb pain.
The mirror technique and other state-of-the-art treatments are being employed at the new Military Advanced Training Center for Soldier Amputees at Walter Reed. When patients look into a mirror, the reflection of a healthy limb is superimposed onto the amputated limb, fooling the brain into thinking it exists. The pain disappears in about 40 percent of patients, Dr. Ramachandran said.
“Patients have a visual illusion that their phantom has come back,” he explained. “When a patient is asked to clap or carry out a synchronized movement, the cramping and pain go away.” After a month of repeated trials, the phantom limb pain disappears, Dr. Ramachandran said. Several other teams have replicated the finding. They are now conducting similar studies on stroke patients, many of whom have regained movement of their paralyzed arm and strengthened their grip.
Figure. Dr. Vilayanu...Image Tools
Dr. Buckenmaier's next mission is to get an acute pain service up and running on the battlefield. “We have come a long way,” he said, “but we have a lot more to accomplish.” He noted that much of the funding support for the research and training had come through a partnership between the John P. Murtha Neuroscience and Pain Institute, established by Congressman John Murtha of Pennsylvania's 12th district, and Walter Reed Medical Center.