Comparison of the effects of ketamine and morphine on performance of representative military tasks.

BACKGROUND: When providing care under combat or hostile conditions, it may be necessary for a casualty to remain engaged in military tasks after being wounded. Prehospital care under other remote, austere conditions may be similar, whereby an individual may be forced to continue purposeful actions despite traumatic injury. Given the adverse side-effect profile of intramuscular (i.m.) morphine, alternative analgesics and routes of administration are of interest. Ketamine may be of value in this capacity. OBJECTIVES: To delineate performance decrements in basic soldier tasks comparing the effects of the standard battlefield analgesic (10 mg i.m. morphine) with 25 mg i.m. ketamine. METHODS: Representative military skills and risk propensity were tested in 48 healthy volunteers without pain stimuli in a double-blind, placebo-controlled, crossover design. RESULTS: Overall, participants reported more symptoms associated with ketamine vs. morphine and placebo, chiefly dizziness, poor concentration, and feelings of happiness. Performance decrements on ketamine, when present, manifested as slower performance times rather than procedural errors. CONCLUSIONS: Participants were more symptomatic with ketamine, yet the soldier skills were largely resistant to performance decrements, suggesting that a trained task skill (autonomous phase) remains somewhat resilient to the drugged state at this dosage. The performance decrements with ketamine may represent the subjects' adoption of a cautious posture, as suggested by risk propensity testing whereby the subject is aware of impairment, trading speed for preservation of task accuracy. These results will help to inform the casualty care community regarding appropriate use of ketamine as an alternative or opioid-sparing battlefield analgesic.

Evaluation of the Military Functional Assessment Program: Preliminary Assessment of the Construct Validity Using an Archived Database of Clinical Data.

BACKGROUND: Several important factors must be considered when deciding to return a soldier to duty after a traumatic brain injury (TBI). Premature return increases risk for not only second-impact syndrome during the acute phase but also permanent changes from repetitive concussions. Thus, there is a critical need for return-to-duty (RTD) assessment criteria that encompass the spectrum of injury and disease experienced by US soldiers, particularly TBI. OBJECTIVES: To provide evidence-based standards to eventually serve as criteria for operational competence and performance of a soldier after injury. Specifically, the relationships between clinical assessments and novel military-specific tasks were evaluated. METHOD: Exploratory analyses (including nonparametric tests and Spearman rank correlations) of an archived database. PARTICIPANTS: A total of 79 patients with TBI who participated in an RTD assessment program at a US Army rehabilitation and recovery center. MAIN MEASURES: Military Functional Assessment Program (to determine a soldier's operational competence and performance after TBI) tasks; Dizziness Handicap Inventory; Dynamic Visual Acuity (vestibular function); Sensory Organization Test (postural control); Repeatable Battery for the Assessment of Neuropsychological Status (neuropsychological screening test); Beck Depression Inventory-II; Beck Anxiety Inventory; Comprehensive Trail Making Test (visual search and sequencing); posttraumatic stress disorder checklist military version; Alcohol Use Disorders Identification Test; Epworth Sleepiness Scale; Patient Health Questionnaire; and Military Acute Concussion Evaluation. RESULTS: Selected military operational assessment tasks correlated significantly with clinical measures of vestibular function, psychological well-being, and cognitive function. Differences on occupational therapy assessments, a concussion screening tool, and a self-report health questionnaire were seen between those who passed and those who failed the RTD assessment. Specifically, those who passed the RTD assessment scored more favorably on these clinical assessments. CONCLUSIONS: This study demonstrated convergent validity between Military Functional Assessment Program tasks and clinical assessment scores. The Military Functional Assessment Program shows promise for augmenting decision making related to RTD and soldier skills. Additional research is needed to determine the effectiveness of this program in predicting RTD success.

Tactile cues in continuous operations: a preliminary study.

INTRODUCTION: Research has shown that tactile displays are an effective tool for augmenting spatial orientation and situation awareness information provided to aircraft operators. The tactile situation awareness system (TSAS) has been shown to improve flight performance in conditions of degraded visual environments and to safely maintain performance during hover over moving targets. The potential for the user to adapt and habituate to the stimulus of tactile display systems has not yet been investigated. METHODS: Four UH-60 current, rated aviators (all male) participated in the pilot study. Subjects completed four consecutive iterations of a 3-h flight profile consisting of 10 maneuvers, totaling 12 h of continuous flight. Flight performance, tactor information, responses to a discomfort questionnaire, and ratings of fatigue symptoms were recorded. RESULTS: The independent variable in all analyses was session (four levels). The results showed that performance per maneuver and proportion of stimulus cues (measure of response to cues) per maneuver were consistent across sessions using independent-samples Kruskal-Wallis tests. DISCUSSION: The findings of this preliminary assessment support the use of tactile displays (consistent with parameters of TSAS) in continuous operations since performance and proportion of stimulus cues presented was consistent over a period of 12 h. In conclusion, the system will require further experimental testing, but these preliminary findings do not suggest performance or response to be affected by any adaptation or habituation to the stimulus.