Evaluating the Efficacy of Chronic Galantamine on Sustained Attention and Cholinergic Neurotransmission in A Pre-Clinical Model of Traumatic Brain Injury.

Cholinergic disruptions underlie attentional deficits following traumatic brain injury (TBI). Yet, drugs specifically targeting acetylcholinesterase (AChE) inhibition have yielded mixed outcomes. Therefore, we hypothesized that galantamine (GAL), a dual-action competitive AChE inhibitor and α7 nicotinic acetylcholine receptor (nAChR) positive allosteric modulator, provided chronically after injury, will attenuate TBI-induced deficits of sustained attention and enhance ACh efflux in the medial prefrontal cortex (mPFC), as assessed by in vivo microdialysis. In Experiment 1, adult male rats (n = 10-15/group) trained in the 3-choice serial reaction time (3-CSRT) test were randomly assigned to controlled cortical impact (CCI) or sham surgery and administered GAL (0.5, 2.0, or 5.0 mg/kg; i.p.) or saline vehicle (VEH; 1 mL/kg; i.p) beginning 24-h post-surgery and once daily thereafter for 27 days. Measures of sustained attention and distractibility were assessed on post-operative days 21-25 in the 3-CSRT, following which cortical lesion volume and basal forebrain cholinergic cells were quantified on day 27. In Experiment 2, adult male rats (n = 3-4/group) received a CCI and 24 h later administered (i.p.) one of the three doses of GAL or VEH for 21 days to quantify the dose-dependent effect of GAL on in vivo ACh efflux in the mPFC. Two weeks after the CCI, a guide cannula was implanted in the right mPFC. On post-surgery day 21, baseline and post-injection dialysate samples were collected in a temporally matched manner with the cohort undergoing behavior. ACh levels were analyzed using reverse phase high-performance liquid chromatography (HPLC) coupled to an electrochemical detector. Cortical lesion volume was quantified on day 22. The data were subjected to ANOVA, with repeated measures where appropriate, followed by Newman-Keuls post hoc analyses. All TBI groups displayed impaired sustained attention versus the pooled SHAM controls (p's < 0.05). Moreover, the highest dose of GAL (5.0 mg/kg) exacerbated attentional deficits relative to VEH and the two lower doses of GAL (p's < 0.05). TBI significantly reduced cholinergic cells in the right basal forebrain, regardless of treatment condition, versus SHAM (p < 0.05). In vivo microdialysis revealed no differences in basal ACh in the mPFC; however, GAL (5.0 mg/kg) significantly increased ACh efflux 30 min following injection compared to the VEH and the other GAL (0.5 and 2.0 mg/kg) treated groups (p's < 0.05). In both experiments, there were no differences in cortical lesion volume across treatment groups (p's > 0.05). In summary, albeit the higher dose of GAL increased ACh release, it did not improve measures of sustained attention or histopathological markers, thereby partially supporting the hypothesis and providing the impetus for further investigations into alternative cholinergic pharmacotherapies such as nAChR positive allosteric modulators.

Efficacy of a music-based intervention in a preclinical model of traumatic brain injury: An initial foray into a novel and non-pharmacological rehabilitative therapy.

Traumatic brain injury (TBI) causes neurobehavioral and cognitive impairments that negatively impact life quality for millions of individuals. Because of its pernicious effects, numerous pharmacological interventions have been evaluated to attenuate the TBI-induced deficits or to reinstate function. While many such pharmacotherapies have conferred benefits in the laboratory, successful translation to the clinic has yet to be achieved. Given the individual, medical, and societal burden of TBI, there is an urgent need for alternative approaches to attenuate TBI sequelae and promote recovery. Music based interventions (MBIs) may hold untapped potential for improving neurobehavioral and cognitive recovery after TBI as data in normal, non-TBI, rats show plasticity and augmented cognition. Hence, the aim of this study was to test the hypothesis that providing a MBI to adult rats after TBI would improve cognition, neurobehavior, and histological endpoints. Adult male rats received a moderate-to-severe controlled cortical impact injury (2.8 mm impact at 4 m/s) or sham surgery (n = 10-12 per group) and 24 h later were randomized to classical Music or No Music (i.e., ambient room noise) for 3 h/day from 19:00 to 22:00 h for 30 days (last day of behavior). Motor (beam-walk), cognitive (acquisition of spatial learning and memory), anxiety-like behavior (open field), coping (shock probe defensive burying), as well as histopathology (lesion volume), neuroplasticity (BDNF), and neuroinflammation (Iba1, and CD163) were assessed. The data showed that the MBI improved motor, cognitive, and anxiety-like behavior vs. No Music (p's < 0.05). Music also reduced cortical lesion volume and activated microglia but increased resting microglia and hippocampal BDNF expression. These findings support the hypothesis and provide a compelling impetus for additional preclinical studies utilizing MBIs as a potential efficacious rehabilitative therapy for TBI.

Caseworker Cultural Mediator Involvement in Neurocritical Care for Patients and Families With Non-English Language Preference: A Quality Improvement Project.

Objective To describe Harborview Medical Center's experience with the involvement of caseworker cultural mediators (CCM) for patients requiring neurocritical care. Methods Using univariate and multivariate analysis (model adjusted for age, Glasgow Coma Scale score (GCS), Sequential Organ Failure Assessment (SOFA) Scores, mechanical ventilation, transition to comfort measures only (CMO), and death by neurologic criteria), we examined CCM team members' involvement in the care of Amharic/Cambodian/Khmer/Somali/Spanish/Vietnamese patients admitted to our neurocritical care service between 2014-2022, factors associated with CCM utilization, and changes in CCM utilization after a QI initiative was implemented in 2020 to encourage healthcare providers to consult the CCM team. Results Compared to eligible patients (n=827) who did not receive CCM referral, patients with CCM involvement (n=121) were younger (49 [interquartile range, IQR 38,63] vs. 56 [IQR 42,68] years, p = 0.002), had greater illness severity (admission GCS 8.5 [IQR 3,14] vs. 14 [IQR 7,15], p < 0.001, SOFA scores (5 [IQR 2,8] vs. 4 [IQR2,6], p = 0.007), and more frequently required mechanical ventilation (67% vs. 40%, odds ratio, OR 3.07, 95% CI 2.06,4.64), with higher all-cause mortality (20% vs. 12%, RR 1.83, 95% CI 1.09, 2.95), and with a higher rate of transition to CMO (11.6% vs. 6.2%, OR 2.00, 95% CI 1.03;3.66). The CCM QI initiative was independently associated with increased CCM involvement (aOR 4.22, 95% CI [2.32;7.66]). Overall, 4/10 attempts made by CCMs to reach out to the family to provide support were declined by the family. CCMs reported providing cultural/emotional support (n=96, 79%), end-of-life counseling (n=16, 13%), conflict mediation (n=15, 12.4%), and facilitating goals of care meetings (n=4, 3.3%). Conclusions Among eligible patients, CCM consultations appeared to occur in patients with higher disease severity. Our QI initiative increased CCM involvement.

Sustained attention performance deficits in the three-choice serial reaction time task in male and female rats after experimental brain trauma.

Impaired attention is central to the cognitive deficits associated with long-term sequelae for many traumatic brain injury (TBI) survivors. Assessing complex sustained attention post-TBI is clinically-relevant and may provide reliable avenues towards developing therapeutic and rehabilitation targets in both males and females. We hypothesized that rats subjected to a moderate TBI will exhibit attentional deficits seen as reduced accuracy and increased distractibility in an operant 3-choice serial reaction time task (3-CSRT), designed as an analogue of the clinical continuous performance test. Upon reaching baseline of 70% accuracy at the 300 ms cue, adult male and female Sprague-Dawley rats were subjected to a controlled cortical impact (2.8 mm deformation at 4 m/s) or sham injury over the right parietal cortex. After two weeks of recovery, they were retested on the 3-CSRT for ten days. Dependent measures include percent accuracy (overall and for each of the three cue ports), percent omissions, as well as latency to instrumental poke and retrieve reward. Results demonstrate that both males and females displayed reduced percent accuracy and increased omissions when re-tested post-TBI on 3-CSRT compared to Sham rats and to their own pre-insult baseline (p's < 0.05). Performance accuracy was impaired consistently throughout the ten days of post-surgery re-testing, suggesting pronounced and long-lasting dysfunction in sustained attention processes. Deficits were specifically more pronounced when the cue was pseudorandomly presented in the left-side cue port (p < 0.05), mirroring clinical hemispatial neglect. These data demonstrate significant and persistent complex attention impairments in both sexes after TBI, rendering identifying efficient therapies for cognitive recovery as pivotal.

Limb Tourniquet Holding Location: Model Results Fail to Translate to Human Results.

BACKGROUND: During strap pulling, how limb tourniquet sliding is prevented affects secured pressure achievement. Data from model setups indicated moving the Tactical Ratcheting Medical Tourniquet (Tac RMT; m2 inc.) holding loop location could be advantageous regarding strap-pulling pressure achievement. METHODS: Self- and buddy-strap pull applications to the arm and mid-thigh were done with the commercially available Tac RMT with the holding loop adjacent to the strap redirect buckle (NEAR) and with a modified Tac RMT with the holding loop moved to the far end of the toothed ladder from the redirect (FAR). Arm applications had the strap redirect buckle on the lateral aspect of the arm. Thigh applications had the strap redirect buckle on the lateral aspect and included applications with the strap's free end pulled downward and applications with the strap free end pulled upward. Buddy- arm and thigh pull-upward applications with FAR allowed a nonstandard technique of including thumb assistance of the strap into the redirect. RESULTS: With standard technique, five of six pairs had lower FAR secured pressures (median difference, 16mmHg). When thumb assistance was used, four of five NEAR-FAR pairs had higher FAR secured pressures (median difference, 40mmHg). The thumb strap feeding technique was neither simple nor obvious. CONCLUSIONS: Moving the holding loop location is unlikely to be advantageous for Tac RMT actual applications. Model setup findings need to be checked with applications by humans to humans.

Pressure Responses of Tourniquet Practice Models to Calibrated Force Applications.

BACKGROUND: Tourniquet training sometimes involves models, and a certification process is expected to use something other than human limbs; therefore, investigating model- and limb-pressure responses to force application is important. METHODS: Pressure response to force was collected for a 3.8cm-wide nonelastic strap and a 10.1cm-wide elastic strap placed over 14 objects. Each object was suspended; an inflated neonatal blood pressure cuff was placed atop the object with the strap over the bladder; and strap ends were connected below with 4.54kg weights attached at 20-second intervals to 27.24kg. RESULTS: Pressure-response curves differed by strap, thigh aspect (medial, lateral, ventral, dorsal; n = 2 subjects; p < .0001); subject (medial thigh; n = 3 subjects; p < .0001); and object (thighs; small and large pool noodles ± central metal rod, foam yoga roller, coffee can, 20% ballistic gel cylinder [Gel; Clear Ballistics; clearballistics.com] with central metal tubing, rolled pair of 5mm yoga mats ± central metal rod, hemorrhage-control training thigh [Z-Medica], sand-filled training manikin limb [Drumm Emergency Solutions]; p < .0001). Compliance, circumference, support techniques, and surface interactions, especially with the 10.1cm-wide elastic strap, affected pressure responses: smaller circumference, lower compliance, and lower surface coefficient of friction were associated with higher pressure/force applied. CONCLUSIONS: Different objects have different pressure-response curves. This may be important to acquisition and retention of limb tourniquet skills and is important for systems for certifying tourniquets.

Experimental and Theoretical Study of the Electronic Structures of Lanthanide Indium Perovskites LnInO3.

Ternary lanthanide indium oxides LnInO3 (Ln = La, Pr, Nd, Sm) were synthesized by high-temperature solid-state reaction and characterized by X-ray powder diffraction. Rietveld refinement of the powder patterns showed the LnInO3 materials to be orthorhombic perovskites belonging to the space group Pnma, based on almost-regular InO6 octahedra and highly distorted LnO12 polyhedra. Experimental structural data were compared with results from density functional theory (DFT) calculations employing a hybrid Hamiltonian. Valence region X-ray photoelectron and K-shell X-ray emission and absorption spectra of the LnInO3 compounds were simulated with the aid of the DFT calculations. Photoionization of lanthanide 4f orbitals gives rise to a complex final-state multiplet structure in the valence region for the 4f n compounds PrInO3, NdInO3, and SmInO3, and the overall photoemission spectral profiles were shown to be a superposition of final-state 4f n-1 terms onto the cross-section weighted partial densities of states from the other orbitals. The occupied 4f states are stabilized in moving across the series Pr-Nd-Sm. Band gaps were measured using diffuse reflectance spectroscopy. These results demonstrated that the band gap of LaInO3 is 4.32 eV, in agreement with DFT calculations. This is significantly larger than a band gap of 2.2 eV first proposed in 1967 and based on the idea that In 4d states lie above the top of the O 2p valence band. However, both DFT and X-ray spectroscopy show that In 4d is a shallow core level located well below the bottom of the valence band. Band gaps greater than 4 eV were observed for NdInO3 and SmInO3, but a lower gap of 3.6 eV for PrInO3 was shown to arise from the occupied Pr 4f states lying above the main O 2p valence band.

Limb Position Change Affects Tourniquet Pressure.

BACKGROUND: Limb position changes are likely during transport from injury location to definitive care. This study investigated passive limb position change effects on tourniquet pressure and occlusion. METHODS: Triplicate buddy-applied OMNA® Marine Tourniquet applications to Doppler-based occlusion were done to sitting and laying supine mid-thigh (n=5) and sitting mid-arm (n=3). Tourniqueted limb positions were bent/straight/bent and straight/bent/straight (randomized first position order, 5 seconds/position, pressure every 0.1 second, two-way repeated measures ANOVA). RESULTS: Sitting thigh occlusion pressures leg bent were higher than straight (median, minimum-maximum; 328, 307-403mmHg versus 312, 295-387mmHg, p = .013). In each recipient, the pressure change for each position change for each limb had p < .003. In each recipient, when sitting, leg bent to straight increased pressure (326, 276-415mmHg to 371, 308-427mmHg bent first and 275, 233-354mmHg to 311, 241-353mmHg straight first), and straight to bent decreased pressure (371, 308-427mmHg to 301, 262-388mmHg bent first and 312, 265-395mmHg to 275, 233-354mmHg straight first). When laying, position changes from leg bent first resulted in pressure changes in each recipient but not in the same directions in each recipient. From laying leg straight first, in each recipient changing to bent increased the pressure (295, 210-366mmHg to 328, 255-376mmHg) and to straight decreased the pressure (328, 255-376 mmHg to 259, 210-333 mmHg). Sitting arm bent occlusion pressures were lower than straight (230, 228-252mmHg versus 256, 250-287mmHg, p = .026). Arm position changes resulted in pressure changes in each recipient but not in the same directions in each recipient. Changes in pressure trace character (presence or absence of rhythmically pulsatile traces) and Doppler-based occlusion were consistent with limb position-induced changes in tourniquet pressure (each p ≤ .001 leg, p = .071 arm traces, and p = .188 arm occlusion). CONCLUSIONS: Passive limb position changes can cause significant changes in tourniquet pressure. Therefore, tourniquet adequacy should be reassessed after any limb position change.

OMNA Marine Tourniquet Self-Application.

BACKGROUND: The OMNA Marine Tourniquet is a 5.1cm-wide, simple redirect buckle, hoop-and-loop secured, ratcheting tourniquet designed for storage and use in marine environments. This study evaluated self-application effectiveness and pressures. METHODS: Triplicate secured, occlusion, and completion pressures were measured during 60 subjects pulling down or up thigh applications and nondominant, single-handed arm applications. Arm pressure measurements required circumferences =30cm. RESULTS: Thirty-one subjects had arm circumferences ≥30cm. All 540 applications were effective; 376 of 453 applications had known secured pressures >150mmHg (89 of 93 arm). Thigh down versus up pulling directions were not different (secured, occlusion, and completion pressures and ladder tooth advances). Occlusion pressures were 348mmHg (275-521mmHg) for combined thighs and 285mmHg (211-372mmHg) for arms. Completion pressures were 414mmHg (320-588mmHg) for combined thighs and 344mmHg (261-404mmHg) for arms. Correlations between secured pressures and occlusion ladder tooth advances (clicks) were r2 = 0.44 for combined thighs and 0.68 for arms. Correlations between occlusion pressures and occlusion clicks were poor (r2 = 0.24, P < .0001 for combined thighs and r2 = 0.027, P = .38 for arms). CONCLUSIONS: The OMNA Marine Tourniquet can be self-applied effectively, including one-handed applications. Occlusion and completion pressures are similar to reported 3.8cm-wide Ratcheting Medical Tourniquet pressures.

Clothing Effects on Limb Tourniquet Application.

BACKGROUND: Sometimes tourniquets are applied over clothing. This study explored clothing effects on pressures and application process. METHODS: Generation 7 Combat Application Tourniquets (C-A-T7), Generation 3 SOF® Tactical Tourniquets-Wide (SOFTTW), Tactical Ratcheting Medical Tourniquets (Tac RMT), and Stretch Wrap And Tuck Tourniquets (SWATT) were used with different clothing conditions (Bare, Scrubs, Uniform, Tights) mid-thigh and on models (ballistic gel and yoga mats). RESULTS: Clothing affected pressure responses to controlled force applications (weight hangs, n=5 thighs and models, nonlinear curve fitting, p < .05). On models, clothing affected secured pressures by altering surface interactions (medians: Gel Bare C-A-T7 247mmHg, SOFTTW 99mmHg, Tac RMT 101mmHg versus Gel Clothing C-A-T7 331mmHg, SOFTTW 170mmHg, Tac RMT 148mmHg; Mats Bare C-A-T7 246mmHg, SOFTTW 121mmHg, Tac RMT 99mmHg versus Mats Clothing C-A-T7 278mmHg, SOFTTW 145mmHg, Tac RMT 138mmHg). On thighs, clothing did not significantly influence secured pressures (n=15 kneeling appliers, n=15 standing appliers) or occlusion and completion pressures (n=15). Eleven of 15 appliers reported securing on clothing as most difficult. Fourteen of 15 reported complete applications on clothing as most difficult. CONCLUSIONS: Clothing will not necessarily affect tourniquet pressures. Surface to tourniquet interactions affect the ease of strap sliding, so concern should still exist as to whether applications over clothing are dislodged in a distal direction more easily than applications on skin.

Characterizing a System for Measuring Limb Tourniquet Pressures.

BACKGROUND: Pressure is an important variable in emergency use limb tourniquet science. This study characterizes one system for measuring tourniquet-applied pressure. METHODS: A neonatal blood pressure cuff bladder was inflated to target pressures over atmospheric. Unconstrained or constrained within 1-inch tubular polyester webbing, the neonatal cuff was placed in a 500mL Erlenmeyer flask. A 3-hole stopper provided connections to flask interior (chamber) and bladder pressure sensors and a 60mL syringe for altering chamber pressure: atmospheric to >1500mmHg absolute to atmospheric. RESULTS: Within a finite range of chamber pressures, the neonatal cuffbased system accurately indicates applied pressure (minimum and maximum 95% confidence interval linear regression slopes of 0.9871 to 0.9953 and y-intercepts of -0.1144 to 2.157). The visually defined linear response ranges for bladder inflation pressures were as follows for unconstrained/ constrained: 100 to 400mmHg unconstrained/450mmHg constrained for 10mmHg, 150 unconstrained/100 constrained to 450mmHg for 12mmHg, 150 to 500mmHg for 15mmHg, 150 to 500mmHg unconstrained/550mmHg constrained for 18mmHg, 150 to 550mmHg for 21mmHg. Below the linear response range, the inflated bladder system indicated higher pressures than chamber pressures. Above the linear response range, the system indicated progressively lower pressures than chamber pressures. CONCLUSIONS: Within the linear response range, the bladder pressure accurately indicates surface-applied pressure.

Review: Getting Tourniquets Right = Getting Tourniquets Tight.

Tourniquet application to stop limb bleeding is conceptually simple, but optimal application technique matters, generally requires training, and is more likely with objective measures of correct application technique. Evidence of problems with application techniques, knowledge, and training can be ascertained from January 2007 to August 2018 PubMed peer-reviewed papers and in Stop The Bleed-related videos. Available data indicates optimal technique when not under fire involves application directly on skin. For nonelastic tourniquets, optimal application technique includes pulling the strap tangential to the limb at the redirect buckle (parallel to the limb-encircling strap entering the redirect buckle). Before engaging the mechanical advantage tightening system, the secured strap should exert at least 150mmHg inward, and skin indentation should be visible. For Combat Application Tourniquets, optimal technique includes the slot in the windlass rod parallel to the stabilization plate during the single 180° turn that should be sufficient for achieving arterial occlusion, which involves visible skin indentation and pressures of 250mmHg to 428mmHg on normotensive adult thighs. Appropriate pressures on manikins and isolated-limb simulations depend on how the under-tourniquet pressure response of each compares to the under-tourniquet pressure response of human limbs for matching tourniquet-force applications. Lack of such data is one of several concerns with manikin and isolated-limb simulation use. Regardless of model or human limb use, pictures and videos purporting to show proper tourniquet application techniques should show optimal tourniquet application techniques and properly applied, arterially occlusive limb tourniquets. Ideally, objective measures of correct tourniquet application technique would be included.

Best Tourniquet Holding and Strap Pulling Technique.

BACKGROUND: Appropriate strap pressure before tightening-system use is an important aspect of nonelastic, limb tourniquet application. METHODS: Using different two-handed techniques, the strap of the Generation 7 Combat Application Tourniquet (C-A-T7), Tactical Ratcheting Medical Tourniquet (Tac RMT), Tactical Mechanical Tourniquet (TMT), Parabelt, and Generation 3 SOF® Tactical Tourniquet-Wide (SOFTTW) was secured mid-thigh by 20 appliers blinded to pressure data and around a thigh-sized ballistic gel cylinder by gravity and 23.06kg. RESULTS: Pulling only outward (90° to strap entering buckle) achieved the lowest secured pressures on thighs and gel. For appliers, the best holding location was above the buckle, and the best strap-pulling direction was tangential to the thigh or gel (0° to strap entering buckle). Preceding tangential pulling with outward pulling resulted in higher secured pressures on the gel but did not aid appliers. Appliers generally did not reach secured pressures achievable for their strength. Of 80 thigh applications per tourniquet, 77 C-A-T7, 41 Tac RMT, 35 TMT, 16 Parabelt, and 10 SOFTTW applications had secured pressures greater than 100mmHg. CONCLUSIONS: The default for best tourniquet strap-application technique is to hold above the buckle and pull the strap tangential to the limb at the buckle. Additionally, neither strength nor experience guarantees desirable strap pressures in the absence of pressure knowledge.

Masimo Perfusion Index Versus Doppler for Tourniquet Effectiveness Monitoring.

BACKGROUND: In addition to a plethysmograph, Masimo pulse oximeters display a Perfusion Index (PI) value. This study investigated the possible usefulness of PI for monitoring limb tourniquet arterial occlusion. METHODS: Tactical Ratcheting Medical Tourniquets were applied to the thighs of 15 subjects. Tightening ended at one ratchet-tooth advance beyond Doppler- indicated occlusion. The times and pressures of Doppler and PI signal absences and returns were recorded. RESULTS: Intermittent PI signal error occurred in 149 of 450 runs (PI, 33% versus Doppler, 0%; p < .0001). PI signal loss lagged Doppler-indicated occlusion by 19 ± 15 seconds (mean ± standard deviation, p < .0001). PI Signal Return lagged tourniquet release by 13 ± 7 seconds (Doppler Signal Return took 1 ± 1 seconds following tourniquet release; p < .0001). PI failed to detect early Doppler audible pulse return in 30 of 39 occurrences. CONCLUSION: The PI available on Masimo pulse oximeters is not appropriate for monitoring limb tourniquet effectiveness.

From Pull to Pressure: Effects of Tourniquet Buckles and Straps.

BACKGROUND: Limb tourniquet pressures > 100 mmHg before tightening system use eases achieving arterial occlusion, minimizes tightening system problems, and probably minimizes discomfort. This study examined effects of buckle and strap features on converting pulling force to strap pressure. STUDY DESIGN: Twenty-two buckle and strap combinations were evaluated using a thigh-diameter, ballistic gel cylinder and 3 thighs. Weights of 14.11, 27.60, and 41.11 kg provided pulling force. The contribution of buckle movement was evaluated: all buckles on gel and 12 on thighs allowed limited vertical movement, 12 on gel and 4 on thighs held static. RESULTS: Force conversion patterns per combination were similar on gel and thighs, including greatest force conversion with some buckle movement allowed. Smooth, round redirect buckles without engagement of a strap-securing mechanism had the best conversions of pulling force to tourniquet pressure; 2 achieved arterially occlusive pressures, neither commercially available. Among hook-and-loop secured tourniquets and threaded for self-securing tourniquets, the Generation 7 Combat Application Tourniquet (C-A-T7) and the Tactical Ratcheting Medical Tourniquet (Tac RMT) had the best conversions of pull to pressure (thigh applications/each weight, mean ± SD: C-A-T7 91 ± 11, 164 ± 30, 228 ± 34 mmHg; Tac RMT 82 ± 13, 150 ± 16, 222 ± 17 mmHg). Other Ratcheting Medical Tourniquets with the same buckle but different strap fabrics performed less well. Even lower pressures occurred with the Tactical Mechanical Tourniquet, the Special Operations Forces Tactical Tourniquet, the Parabelt, and the SAM XT Extremity Tourniquet (165 ± 11, 178 ± 13, 131 ± 14, and 106 ± 14 mmHg, all at 41.11 kg, respectively). CONCLUSIONS: Buckle design and strap fabric affect the conversion of pulling force to tourniquet strap pressure. Low-friction, smooth, round redirects allow the best conversion.

Introgression among three rockfish species (Sebastes spp.) in the Salish Sea, northeast Pacific Ocean.

Interspecific hybridization is often seen as a major conservation issue, potentially threatening endangered species and decreasing biodiversity. In natural populations, the conservation implications of hybridization depends on both on anthropogenic factors and the evolutionary processes maintaining the hybrid zone. However, the timeline and patterns of hybridization in the hybrid zone are often not known. Therefore, species conservation becomes a concern when recent anthropogenic changes influence hybridization and not if hybridization is part of a long-term process. Here, we use sequence data from one mitochondrial gene, three nuclear introns and one nuclear exon to estimate the direction, geographic extent, frequency and possible timeline of hybridization between three rockfish species (Sebastes auriculatus, S. caurinus, S. maliger) in the Salish Sea, Washington, USA. We show that (i) introgression occurred much more frequently in the Salish Sea than on the outer coast, (ii) introgression was highly asymmetrical from S. maliger into the other two species, (iii) almost 40% of individuals in the Salish Sea were hybrids, with frequency of hybrids increasing with isolation from the coast, and (iv) all hybrids were later generation backcrosses rather than F1 hybrids. Our results suggest long-standing low-level hybridization rather than recent onset of interbreeding because of human induced environmental change, possibly facilitated by specific environmental conditions in the sub-basins of the Salish Sea, and by differences in population sizes during recolonization of the area after the last glaciation. This rockfish hybrid system, with asymmetrical introgression and the maintenance of parental species, may prove useful to study both mechanisms that maintain species boundaries and that facilitate speciation in the presence of rapid environmental change.

Effects of Distance Between Paired Tourniquets.

BACKGROUND: In practice, the distance between paired tourniquets varies with unknown effects. METHODS: Ratcheting Medical Tourniquets were applied to both thighs of 15 subjects distally (fixed location) and proximally (0, 2, 4, 8, 12cm gap widths, randomized block). Applications were pair, single distal, single appropriate proximal. Tightening ended one-ratchet tooth advance past Doppler-indicated occlusion. Pairs had alternating tightening starting distal. RESULTS: Occlusion pressures were higher for: each single than respective individual pair tourniquet, each pair distal than respective pair proximal, and each single distal than respective single proximal (all p < .0001). Despite thigh circumference increasing proximally, occlusion pressures were lower with proximal tourniquet involvement (pair or single, p < .0001). Occlusion losses before 120 seconds occurred most frequently with pairs (0cm 4, 2cm 4, 4cm 6, 8cm 7, 12cm 5 for 26 of 150), in increasing frequency with increasingly proximal singles (0cm 0, 2cm 1, 4cm 1, 8cm 2, 12cm 6 for 10 of 150, p < .0001 for trend), and least with single distal (2 of 150, p < .0001). Paired tourniquets required fewer ratchet advances per tourniquet (pair distal 5 ± 1, pair proximal 4 ± 1, single distal 6 ± 1, single proximal 6 ± 1). Final ratchet tooth advancement pressure increases (mmHg) were greatest for singles (distal 61 ± 10, proximal 0cm 53 ± 7, 2cm 51 ± 9, 4cm 50 ± 7, 8cm 45 ± 7, 12cm 36 ± 7) and least in pairs (distal 41 ± 8, proximal 32 ± 7) with progressively less pair interaction as distance increased (pressure change for the pair tourniquet not directly advanced: 0cm 13 ± 4, 2cm 10 ± 4, 4cm 6 ± 3, 8cm 1 ± 2, 12cm -1 ± 2). CONCLUSIONS: Occlusion pressures are lower for paired than single tourniquets despite variable intertourniquet distances. Very proximal placement has a pressure advantage; however, pairs and very proximal locations may be less likely to maintain occlusion. Increasingly proximal placements also increase tissue at risk; therefore, distal placements and minimal intertourniquet distances should still be recommended.

Effectiveness of Pulse Oximetry Versus Doppler for Tourniquet Monitoring.

BACKGROUND: Pulse oximeters are common and include arterial pulse detection as part of their methodology. The authors investigated the possible usefulness of pulse oximeters for monitoring extremity tourniquet arterial occlusion. METHODS: Tactical Ratcheting Medical Tourniquets were tightened to the least Doppler-determined occluding pressure at mid-thigh or mid-arm locations on one limb at a time on all four limbs of 15 volunteers. A randomized block design was used to determine the placement locations of three pulse oximeter sensors on the relevant digits. The times and pressures of pulsatile signal absences and returns were recorded for 200 seconds, with the tourniquet being tightened only when the Doppler ultrasound and all three pulse oximeters had pulsatile signals present (pulsatile waveform traces for the pulse oximeters). RESULTS: From the first Doppler signal absence to tourniquet release, toe-located pulse oximeters missed Doppler signal presence 41% to 50% of the times (discrete 1-second intervals) and missed 39% to 49% of the pressure points (discrete 1mmHg intervals); fingerlocated pulse oximeters had miss rates of 11% to 15% of the times and 13% to 19% of the pressure points. On toes, the pulse oximeter ranges of sensitivity and specificity for Doppler pulse detection were 71% to 90% and 44% to 51%, and on fingers, the respective ranges were 65% to 77% and 78% to 83%. CONCLUSION: Use of a pulse oximeter to monitor limb tourniquet effectiveness will result in some instances of an undetected weak arterial pulse being present. If a pulse oximeter waveform is obtained from a location distal to a tourniquet, the tourniquet should be tightened. If a pulsatile waveform is not detected, vigilance should be maintained.

Pressures Under 3.8cm, 5.1cm, and Side-by-Side 3.8cm-Wide Tourniquets.

BACKGROUND: Applications of wider tourniquet are expected to occlude arterial flow at lower pressures. We examined pressures under 3.8cm-wide, 5.1cm-wide, and side-by-side-3.8cm-wide nonelastic strap-based tourniquets. METHODS: Ratcheting Medical Tourniquets (RMT) were applied mid-thigh and mid-arm for 120 seconds with Doppler-indicated occlusion. The RMTs were a Single Tactical RMT (3.8cm-wide), a Wide RMT (5.1cm-wide), and Paired Tactical RMTs (7.6cm-total width). Tightening completion was measured at one-tooth advance past arterial occlusion, and paired applications involved alternating tourniquet tightening. RESULTS: All 96 applications on the 16 recipients reached occlusion. Paired tourniquets had the lowest occlusion pressures (ρ < .05). All pressures are given as median mmHg, minimum-maximum mmHg. Thigh application occlusion pressures were Single 256, 219-299; Wide 259, 203-287; Distal of Pair 222, 183-256; and Proximal of Pair 184, 160-236. Arm application occlusion pressures were Single 230, 189-294; Wide 212, 161-258; Distal of Pair 204, 193-254, and Proximal of Pair 168, 148-227. Pressure increases with the final tooth advance were greater for the 2 teeth/cm Wide than for the 2.5 teeth/cm Tacticals (ρ < .05). Thigh final tooth advance pressure increases were Single 40, 33-49; Wide 51, 37-65; Distal of Pair 13, 1-35; and Proximal of Pair 15, 0-30. Arm final tooth advance pressure increases were Single 49, 41-71; Wide 63, 48-77; Distal of Pair 3, 0-14; and Proximal of Pair 23, 2-35. Pressure decreases occurred under all tourniquets over 120 seconds. Thigh pressure decreases were Single 41, 32-75; Wide 43, 28-62; Distal of Pair 25, 16-37; and Proximal of Pair 22, 15-37. Arm pressure decreases were Single 28, 21-43; Wide 26, 16-36; Distal of Pair 16, 12-35; and Proximal of Pair 12, 5-24. Occlusion losses before 120 seconds occurred predominantly on the thigh and with paired applications (ρ < .05). Occlusion losses occurred in six Paired thigh applications, two Single thigh applications, and one Paired arm application. CONCLUSIONS: Side-by-side tourniquets achieve occlusion at lower pressures than single tourniquets. Additionally, pressure decreases under tourniquets over time; so all tourniquet applications require reassessments for continued effectiveness.