Page 73 - JSOM Spring 2018

Successful Use of Ketamine as a Prehospital Analgesic by
Pararescuemen During Operation Enduring Freedom

Our Experience and Literature Review

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Regan Lyon, MD ; Chris Schwan, MD *; Joseph Zeal, MD ; Chetan Kharod, MD ;
Brian Staak, EMT P ; Chris Petersen, EMT P ; Stephen Rush, MD 7
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ABSTRACT
Effective analgesia is a crucial part of the care and resuscita- chronic pain control, and procedural sedation. In the United
tion of a traumatically injured patient. These secondary effects States, only the racemic mixture of ketamine is available,
of pain may increase morbidity and mortality in the acutely which contains both the S(+) and R(–) enantiomers.
injured patient. When ketamine is administered appropriately
in the clinical setting, it can provide analgesia, anxiolysis, and Ketamine is typically administered intravenously at doses
amnesia for patients with less respiratory depression and hy- between 1mg/kg and 2mg/kg for procedural sedation and
potension than equivalent doses of opioid analgesics. between 0.1mg/kg and 0.6mg/kg for analgesia. 3,7–10 At sub-
anesthetic doses, ketamine maintains its analgesic properties
Keywords: ketamine; analgesia; pain; opioids; prehospital while having little effect on airway reflexes, respiratory drive,
analgesic; Pararescuemen; Operation Enduring Freedom and cardiovascular stability. 7–9
Because of ketamine’s wide therapeutic window and desir-
able clinical effects, it continues to be recommended by the
Introduction
Committee on Tactical Combat Casualty Care Guidelines.
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Effective analgesia is a crucial part of the care and resuscita- However, the literature on the prehospital use of ketamine is
tion of a traumatically injured patient. Poorly controlled acute limited.
pain adversely affects oxygenation by increasing dead-space
ventilation and by releasing chemical triggers that cause a sys- In 2011, efforts to improve upon prehospital opioid analgesia
temic inflammatory response. These secondary effects of pain were initiated concurrently with discussions with the British
may increase morbidity and mortality in the acutely injured Medical Emergency Response Teams (MERTs) who were us-
patient. 1,2 ing ketamine, US Air Force (USAF) Pararescuemen (PJs) were
authorized to begin using ketamine as a prehospital analgesic
Compared with traditional opioid medications that exert ef- for traumatic pain.
fects on the opioid receptors, ketamine hydrochloride acts as
an N-methyl-d-aspartate (NMDA)-receptor noncompetitive In this process improvement study, we reviewed the USAF PJs’
antagonist. This drug exerts its effect by “disconnecting” the prehospital experience with ketamine administered in a tacti-
thalamocortical and limbic systems, effectively dissociating cal setting to study the analgesic efficacy and safety for pa-
the central nervous system from outside stimuli (e.g., pain, tients during tactical evacuation (TACEVAC).
sight, sound). In essence, the mind is disconnected from the
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incoming pain signals from the body. Ketamine has lesser ef- Methods
fects through its direct action at δ opioid and augmentation of
μ opioid receptor function. When administered appropriately This performance improvement project was approved by the
in the clinical setting, it can provide analgesia, anxiolysis, and Air Force Research Oversight and Compliance Division insti-
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amnesia for patients. Ketamine delivers these desired effects tutional review board.
with less respiratory depression and hypotension than equiva-
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lent doses of opioid analgesics. In addition, recent studies During a deployment to Afghanistan in the summer of 2013,
have shown that ketamine has protective antiinflammatory a USAF pararescue flight surgeon conducted a process im-
properties, which may be beneficial in the setting of acute provement initiative that prospectively surveyed the analgesic
trauma. efficacy of prehospital ketamine administered by PJs during
Operation Enduring Freedom (OEF). Though the initial data
US Food and Drug Administration approval for ketamine use included all patients who received ketamine, for the purposes
includes induction of anesthesia and maintenance of anesthe- of this study, only those who received it for analgesia were in-
sia; however, the medication is used commonly at subanes- cluded. Ketamine dosed specifically for sedation and/or rapid
thetic doses for off-label purposes such as acute pain control, sequence intubation (RSI) was excluded.

*Address correspondence to christopher.schwan@gmail.com
1 Maj Lyon is with US Air Force Medical Corps, Hurlburt Field, FL. Maj Schwan is with the US Air Force Medical Corps, Jacksonville, FL. Dr
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Zeal is with US Air Force Pararescue, Tampa, FL. Col Kharod is with the US AF Medical Corps, San Antonio, TX. Mr Staak is with US Air
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Force Pararescue. Mr Petersen is with US Air Force Pararescue, Westhampton Beach, NY. Dr Rush is with US Air Force Pararescue, Westhamp-
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ton Beach, NY.
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