Abstract
The views expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Department of the Navy, Department of Defense, or the United States Government.
We are military service members. This work was prepared as part of our official duties. Title 17 U.S.C. 105 provides that “Copyright protection under this title is not available for any work of the United States Government.” Title 17 U.S.C. 101 defines a United States Government work as a work prepared by a military service member or employee of the United States Government as part of that person's official duties.
To the Editor:
We read the recently published clinical practice guidelines (CPG) entitled “Wilderness Medical Society Clinical Practice Guidelines for the Treatment of Acute Pain in Austere Environments: 2024 Update.” 1 We appreciate the work done by Fink et al and appreciate the work of the Wilderness Medical Society to help provide CPGs related to austere medical care.
As military anesthesiologists, we train to face the unique challenge of providing effective acute pain management in austere environments. These environments, characterized by limited resources and harsh conditions, are a frequent reality for deployed medical personnel. The recently published guideline excludes “pain management in the military setting” due to assumed greater resources and evacuation options. This presents an incomplete picture. While robust medical support exists in some operational situations, numerous military deployments involve significant resource constraints. These limitations mirror the definition of “austere environments” that was provided in this article. We would argue that the authors should at least consider the current recommendations in the CPG published by the Joint Trauma System (JTS) on the treatment of pain and sedation during prolonged field care. 2 Indeed, the authors purport to exclude recommendations from the military setting but then go on to selectively cite military examples of combat pill packs, transmucosal fentanyl, and methoxyflurane.
Acute pain in an austere environment can be challenging for various reasons, as described in the article. There certainly is a wide range of injuries and intensity of pain requiring a wide scope of medications and treatments to fully address the dynamic nature of acute pain. Figure 1 in the authors’ article demonstrates the relationship between risk and the need for monitoring compared with the intensity of pain and potential treatment options. We disagree with listing regional anesthesia as the highest risk/greatest need for monitoring. We would consider regional anesthesia to be helpful in resource-limited environments and safer than many of the other interventions, including opioids, ketamine, and inhaled nitrous oxide.
Opioids are a very effective tool for acute pain. That said, when treating severe pain with opioids, high doses are required, and this puts the patient at risk for respiratory depression, including both hypoventilation and apnea. In a minimally monitored setting, the risk of respiratory depression can be significant, and consideration of alternative methods should be considered safer.3,4 Ketamine induces significantly less respiratory depression, though patients with obstructive sleep apnea may still develop hypoventilation when exposed to ketamine. 5 Ketamine and opioids are controlled substances in the United States and many other countries. There may be legal concerns with the administration of these substances in foreign countries, as well as by some providers in certain settings (for example, administering controlled substances to a patient on a group hike).
Similarly, nitrous oxide may have significant challenges in austere environments. We use extreme caution in administering nitrous oxide to trauma patients due to a variety of risks. One risk in particular is accumulation in gas-filled spaces in the body, as discussed in the article. This has the potential to induce tension physiology in a preexisting pneumothorax or pneumocephalus, both of which may be difficult to diagnose and treat in the austere setting.
The benefits of regional anesthesia in the austere setting far outweigh the risks. It can provide profound—complete or near complete—analgesia for severely wounded individuals. This can be reasonably achieved without mind-altering substances, thus leaving the patient able to contribute to tasks in a resource-limited environment, such as using a radio, helping treat other patients, or walking out of an environment under their own motive power.
The article states that “nerve blocks may also hamper self-rescue or render a limb unusable for hours.” In traumatically injured patients with an injury that is severe enough to cause severe pain, the likelihood of self-rescue and continued limb use is exceptionally low. When compared with opioids or ketamine for similar pain relief, self-rescue and rescue assistance are much more likely in a patient treated with regional anesthesia.
Regional anesthesia can safely and easily be performed in austere environments.6,7 The authors described a potential risk of local anesthetic systemic toxicity (LAST). LAST has a reported incidence of 0.1% of all blocks, with only 20% of those having serious side effects. 8 When compared to the incidence of side effects of opioids, with up to 34% of patients experiencing minor side effects and 0.1–2% experiencing major side effects, 9 local anesthesia may represent a safer option.
We feel that regional anesthesia carries less risk for the treatment of severe pain than opioids, ketamine, and nitrous oxide. We agree that regional anesthesia should be performed by trained and experienced physicians and be performed with the required safety equipment (including ultrasound). Treatment of LAST involves administration of 20% lipid emulsion (Intralipid 20%, Baxter International Inc, Deerfield, IL, USA), which is rarely available in austere settings (we similarly believe that administration of large doses of opioids can only be safely performed when naloxone is readily available). That said, the practice of restricting local anesthetic doses to submaximal levels will serve to greatly mitigate this risk.
While no randomized controlled trials exist to substantiate our claim regarding the safety of regional anesthesia in an austere environment, the authors’ collective experiences in treating acute pain in austere environments across the world lead us to prefer regional anesthesia for severe pain in resource-limited environments—particularly in the setting of prolonged field care.
