Battle Tested: Ketamine Proves its Worth on the Front Lines

For more about Ketamine: Read Ketamine’s Troubled Past, Promising Future

A 36-year-old soldier was injured when he stepped on a Victim Operated Improvised Explosive Device (VOIED). His injures included a right lower extremity amputation above the knee, complete degloving of the left posterior leg from the calcaneus to the ischium, shrapnel to the scrotum, and shrapnel to the left forearm. Two tourniquets per leg were required to effectively control hemorrhage. He was awake and relatively calm, with a heart rate of 130, respiratory rate 44, and palpable radial pulse. He did not complain of significant pain until the tourniquets were applied. After addressing all life-threats, an IV was initiated. To control the pain the patient was given 75 mg ketamine and 1 mg midazolam IV. He was immediately sedated and pain free. Upon arrival at the HLZ (hot landing zone – a landing zone in hostile fire), there was a delay in the arrival of the MEDEVAC. About 25 minutes after the initial dose, the patient become more aroused and complained of pain. The ketamine and midazolam were repeated with the same effects. He was handed off to the MEDEVAC team conscious, but sedated and pain free.

Ketamine’s use in the ED as a sedating agent is well established. However, ketamine use as an analgesic agent, rather than anesthetic agent, dates back to the early 1970s, when ketamine was first introduced [15]. Over the past decade, ketamine has been used as an analgesic by US Special Forces and coalition forces in the combined Iraq and Afghanistan campaigns. The need for an effective, safe, easily administered, battlefield analgesic has made ketamine a preferred agent in the combat and austere environment. Ketamine analgesia has been pushed even further forward into the hands of combat medics in the austere environment. Within just a few years, the proven safety and efficacy of ketamine has resulted in its use military-wide.

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Current TCCC guidelines recommend a starting dose of 50mg IM/IN or 20mg IV/IO slow push. Most of the previous literature on its use an analgesic agent have ranged from 0.25-0.5mg/kg of ideal body weight slow push. Anecdotally, most of the untoward events (euphoria, hallucinations, etc.) appear to be infusion rate-dependent. An easy way to avoid some of the rate-dependent side-effects is to put the desired dose of ketamine into a small bag of saline and bolus it over several minutes.

The ideal analgesic agent provides adequate pain relief with a safe therapeutic margin in a wide-variety of patients. Ketamine has been safely used in all ages- from the young pediatric population to the critically-ill elderly patient [1,2]. Inadvertent overdoses of up to 100-fold the intended dose have been documented without sequelae [3].

Ketamine as an analgesic agent has proven its worth when used in combination with other drugs or when used as a solo agent. In combination with opioid medications, the addition of ketamine has an opioid-sparing effect, making it a useful agent in the hospital and prehospital settings [4-8]. A recent randomized controlled trial demonstrated a more rapid onset of analgesic effects from ketamine compared to morphine [9]. Ketamine has become a recommended analgesic agent in the combat environment in Afghanistan due to its safety profile, favorable hemodynamic characteristics in severely injured combat casualties, rapid onset and ease of use. Current Tactical Combat Casualty Care guidelines allow for its use even in the setting of eye trauma and head injuries in which the person is conscious enough to demonstrate the need for analgesia. A recent study evaluating the use of analgesic agents at the point-of-injury found no adverse events from the use of ketamine – even under the harshest conditions with minimal to no monitoring [10]. It is a recommended agent by the Wilderness Medical Society for use in remote environments [11]. Even in the hands of non-physician practitioners it appears safe [12]. Risks associated with ketamine use in the setting of head or eye trauma appear to be supported by nothing more than medical folklore [13,14]. The Regional Emergency Medical Services Council of New York City has recently begun to adopt more wide-spread use of this agent. Based on the military’s experience, ketamine’s use as an analgesic agent in the civilian environment warrants further consideration.

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A key challenge with using ketamine for pain is its classification by the FDA as an anesthetic agent. Using sub-dissociative doses of ketamine for analgesia constitutes an “off-label” use of the drug. Yet drugs we use every day – such as ondansetron – are used off-label in the ED. Certainly if ED providers can safely use opioid analgesic agents, an agent with a much safer track record should be in our arsenal. For ketamine to be accepted as a potential alternative to opioid analgesics in either the civilian EMS or emergency department setting, education of physician, nursing and administrative staff may be required. Gaining a better understating of ketamine and its potential advantages as an analgesic may improve patient care and patient safety.

Photo by The U.S. Army

REFERENCES
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