Thymine DNA glycosylase is essential for active DNA demethylation by linked deamination-base excision repair.

DNA methylation is a major epigenetic mechanism for gene silencing. Whereas methyltransferases mediate cytosine methylation, it is less clear how unmethylated regions in mammalian genomes are protected from de novo methylation and whether an active demethylating activity is involved. Here, we show that either knockout or catalytic inactivation of the DNA repair enzyme thymine DNA glycosylase (TDG) leads to embryonic lethality in mice. TDG is necessary for recruiting p300 to retinoic acid (RA)-regulated promoters, protection of CpG islands from hypermethylation, and active demethylation of tissue-specific developmentally and hormonally regulated promoters and enhancers. TDG interacts with the deaminase AID and the damage response protein GADD45a. These findings highlight a dual role for TDG in promoting proper epigenetic states during development and suggest a two-step mechanism for DNA demethylation in mammals, whereby 5-methylcytosine and 5-hydroxymethylcytosine are first deaminated by AID to thymine and 5-hydroxymethyluracil, respectively, followed by TDG-mediated thymine and 5-hydroxymethyluracil excision repair.

Potentially inappropriate medication prescribing in the elderly: Is the Beers Criteria relevant in the Emergency Department today?

STUDY OBJECTIVE: To investigate the frequency of Beers Criteria (BC) medication and opioid use in patients age 65 years and older arriving in the Emergency Department. METHODS: We performed a retrospective observational study of a convenience sample of 400 patients, age 65 years and older, arriving to and discharged solely from the Emergency Department. We examined 400 sequential patient charts with visit dates April-July 2017, for the presence of a Beers Criteria medication or opioid prescription. We also examined each chart for nine specific chief complaints, including return visits and subsequent admissions. RESULTS: Of the 400 patients included in this study, 304 patients (76%; 95% confidence interval [CI] 72% to 80%) had at least 1 prescription at the index ED visit for an "avoid" or "use with caution" Beers Criteria medication. Of these patients, 194 (64%; 95% CI 58% to 69%) had ≥2 Beers medication prescriptions and 122 patients (40%; 95% CI 35% to 46%) had ≥3 Beers medication prescriptions. We found no difference in the number of patients with a chief complaint of interest between the BC medication list (28%) and lacking a BC medication (29%) (p-value = 1). No patients returned in the next 7 days for a medication-related complaint. CONCLUSION: The results of this study call into question the routine application of lists without high-quality evidence to critique the prescribing of certain medications. Further patient-oriented study of the relevance of the Beers Criteria list, especially in light of the changed face of medication profiles and populations, is called for.

Targeting proprotein convertases in furin-rich lung cancer cells results in decreased in vitro and in vivo growth.

Proprotein convertases (PCs) are serine proteases with an active role in the post-translational processing of numerous inactive proteins to active proteins including many substrates of paramount importance in cancer development and progression. Furin (PCSKC3), a well-studied member of this family, is overexpressed in numerous human and experimental malignancies. In the present communication, we treated two furin-overexpressing non-small cell carcinoma (NSCLC) cell lines (Calu-6 and HOP-62) with the PC inhibitor CMK (Decanoyl-Arg-Val-Lys-Arg-chloromethylketone). This resulted in a diminished IGF-1R processing and a simultaneous decrease in cell proliferation of two NSCLC lines. Similarly, growth of subcutaneous xenografts of both cell lines, were partially inhibited by an in vivo treatment with the same drug. These observations point to a potential role of PC inhibitors in cancer therapy. © 2016 Wiley Periodicals, Inc.

Correlation of Left Atrial Appendage Ejection Velocities with the CHADS2 and CHA2DS2-VASc Scores.

BACKGROUND: In patients with atrial fibrillation or flutter, a left atrial appendage ejection velocity measured via transesophageal echocardiography equal to or less than 40 cm/sec has been shown to correlate with an increased risk of developing left atrial appendage thrombus while velocities greater than 40 cm/sec are at lower risk. The CHADS2 and CHA2DS2-VASc scores calculated from clinical variables have been developed to risk stratify patients with atrial fibrillation/flutter in regard to the need for anticoagulation. This study was designed to assess whether a relationship exists between left atrial appendage ejection velocities and the respective CHADS2 and CHA2DS2-VASc scores, and whether this relationship is affected by the presence of atrial fibrillation or atrial flutter. METHODS: A retrospective chart review was performed on patients in the last 5 years who had undergone a transesophageal echocardiogram in which LAA velocity was measured. Once these patients were identified, relevant clinical information allowing for the calculation of the CHADS2 and CHA2DS2-VASc scores was also extracted from the medical record. RESULTS: Data from a total of 151 patients were included in the study. A statistically significant correlation between LAA velocity and CHADS2 score (P = 0.942) or between LAA velocity and CHA2DS2-VASc scores (P = 0.723) was not found. CONCLUSIONS: We could not identify a relationship between either the CHADS2 or CHA2DS2-VASc scores and LAA velocities. This was true regardless of whether patients were in sinus rhythm or AF at the time of the TEE. While reduced LAA velocities increase the risk of LAA thrombus, the development of stroke in patients with AF is secondary to a complex interplay of multiple clinical variables.

Occlusion Pressures of Tactical Pneumatic Tourniquet 2".

BACKGROUND: The Tactical Pneumatic Tournqiuet 2" (TPT2, 5.1cm-wide deflated) allows total average applied pressure measurement, which should be useful toward development of emergency-use limb tourniquet certification devices. METHODS: The TPT2 hand bulb was replaced with stopcocks and syringes, allowing filling with continuous pressure measurement. Forearm and mid-thigh applications involved two sets of five Doppler-based pulse gone/return pairs. Second set pulse gones were chosen a priori for occlusion pressures (preliminary work indicated greater consistency in second sets). RESULTS: All 68 forearms occluded (30 female, 38 male, median circumference 17.8cm, range 14.6-23.5cm; median second set of pulse gone tourniquet pressures 176mmHg, range 128-282mmHg). Fifty-five thighs occluded (median circumference 54.3cm, range 41.6-62.4cm; median systolic pressure 126mmHg, range 102-142mmHg; median second set of pulse gone pressures 574mmHg, range 274-1158mmHg). Thirteen thigh applications were stopped without occlusion because of concerning pressures combined with no indication of imminent occlusion and difficulties forcing more air into the TPT2 (3 female, 10 male, peak pressures from 958-1377mmHg, median 1220mmHg, p<.0001 versus occluded thighs; median circumference 63.3cm, range 55.0-72.9cm, p<.0001 versus occluded thighs; median systolic pressure 126mmHg, range 120-173mmHg, p<.019 versus occluded thighs). Thigh TPT2 impression widths on five subjects after occlusion were as follows: 3.5cm, occlusion 274mmHg; 2.8cm, occlusion 348mmHg; 2.9cm, occlusion 500mmHg; 2.8cm, occlusion 782mmHg; 2.7cm, occlusion 1114mmHg. CONCLUSIONS: Though probably useful to tourniquet certification, the required pressures for thigh occlusion make the TPT2 undesirable for any clinical use, emergency or otherwise.

The cumulative effect of multiple critical care protocols on length of stay in a geriatric trauma population.

The elderly individuals are the most rapidly growing cohort within the US population, and a corresponding increase is being seen in elderly trauma patients. Elderly patients are more likely to have a hospital length of stay (LOS) in excess of 10 days. They account for 60% of total ICU days. Length of stay is frequently used as a proxy measure for improvement in injury outcomes, changes in quality of care, and hospital outcomes. Patient care protocols are typically created from evidence-based guidelines that serve to reduce variation in care from patient to patient. Patient care protocols have been found to positively impact patient care with reduced duration of mechanical ventilation, shorter LOS in the ICU and shorter overall hospitalization time, reduced mortality, and reduced health care costs. The following study was designed to assess the impact of the implementation of 4 patient care protocols within an elderly trauma population. We hypothesized that the implementation of these protocols would have a beneficial impact on patient care that could be measured by a decrease in hospital LOS. An archival, retrospective pretest/posttest study was performed on elderly trauma patients. The new protocols helped guide practical changes in care that resulted in a 32% decrease in LOS for our elderly trauma patients which exceeds the 25% decrease found in other studies. Additionally, the "Other" category for each variable was less frequently used in the post-protocol phase than in the pre-protocol phase, suggesting a spillover effect on the level of detail recorded in the patient chart. With less variation in practices in the post-protocol phase, Injury Severity score, and admission systolic blood pressure emerged as significant predictors of LOS.

Implementation of a rib fracture triage protocol in elderly trauma patients.

Elderly patients are highly susceptible to rib fractures after trauma. The use of a clinical pathway to determine resource allocation for patients with rib fractures has resulted in positive treatment outcomes. This retrospective study assessed the efficacy of a triage protocol involving trauma services on hospital length of stay in elderly patients with fractured ribs. Patients who had 3 or more ribs fractured experienced a statistically significant reduction in hospital length of stay after protocol implementation. We conclude that elderly patients with 3 or more rib fractures should be systematically referred to a trauma specialist.

Assessment of the implementation of a protocol to reduce ventilator-associated pneumonia in intensive care unit trauma patients.

Ventilator-associated pneumonia (VAP) is the primary hospital-acquired infection contracted by critically ill patients who receive mechanical ventilation. This retrospective study evaluated the efficacy of a multifaceted VAP prevention protocol in an adult trauma population. Ventilator-associated pneumonia was defined according to the National Healthcare Safety Network (2009) criteria. The number of days to onset of VAP in the postprotocol period was longer than the preprotocol period despite a concomitant increase in the number of mechanical ventilation days.

Effects of Tourniquet Features on Application Processes.

BACKGROUND: We investigated emergency-use limb tourniquet design features effects on application processes (this paper) and times to complete those processes (companion paper). METHODS: Sixty-four appliers watched training videos and then each applied all eight tourniquets: Combat Application Tourniquet Generation 7 (CAT7), SOF™ Tactical Tourniquet-Wide Generation 3 (SOFTTW3), SOF™ Tactical Tourniquet-Wide Generation 5 (SOFTTW5), Tactical Mechanical Tourniquet (TMT), OMNA Marine Tourniquet (OMT), X8T tourniquet (X8T), Tactical Ratcheting Medical Tourniquet (Tac RMT), and RapidStop™ Tourniquet (RST). Application processes were scored from videos. RESULTS: Thirty-three appliers had no prior tourniquet experience. All 512 applications were placed proximal to the recipient's simulated distal thigh injury. Thirty-one appliers (13 with no experience) had 66 problem-free applications (18 by no experience appliers). Tightening-system mechanical problems were more frequent with windlass rod systems (26 losing hold of the rod, 27 redoing rod turns, and 58 struggling to secure the rod) versus ratchet systems (3 tooth skips and 16 advance failures). Thirty-five appliers (21 with no experience) had 68 applications (45 by no experience appliers) with an audible Doppler pulse when stating "Done"; causes involved premature stopping (53), inadequate strap pull (1 SOFTTW3, 1 RST), strap/redirect understanding problem (1 SOFTTW5, 1 X8T, 4 Tac RMT, 1 RST), tightening-system understanding problem (2 CAT7, 1 SOFTTW3, 1 TMT, 1 RST), and physical inability to secure (1 SOFTTW3). Fifty-three appliers (32 no experience) had 109 applications (64 by no experience appliers) not correctly secured. Six involved strap/redirect understanding problems: 4 Tac RMT, 1 X8T, 1 SOFTTW5; 103 involved improper securing of non-self-securing design features: 47 CAT7 (8 strap, 45 rod), 31 TMT (17 strap, 19 rod), 22 OMT (strap), and 3 SOFTTW3 (rod). CONCLUSION: Self-securing systems have process advantages. Because most emergent tourniquet recipients require transport, we believe tourniquet security is a critical design aspect. Decisions regarding tourniquet choices may become very different when both occlusion and tourniquet security are considered.

Effects of Tourniquet Features on Application Processes Times.

BACKGROUND: We investigated emergency-use limb tourniquet design features effects on application processes (companion paper) and times to complete those processes (this paper). METHODS: Sixty-four appliers watched training videos then each applied all eight tourniquets: Combat Application Tour- niquet Generation 7 (CAT7), SOF™ Tactical Tourniquet-Wide Generation 3 (SOFTTW3), SOF™ Tactical Tourniquet-Wide Generation 5 (SOFTTW5), Tactical Mechanical Tourniquet (TMT), OMNA Marine Tourniquet (OMT), X8T-Tourniquet (X8T), Tactical Ratcheting Medical Tourniquet (Tac RMT), and RapidStop Tourniquet (RST). Application processes times were captured from videos. RESULTS: From "Go" to "touch tightening system" was fastest with clips and self-securing redirect buckles and without strap/redirect application process problems (n, median seconds: CAT7 n=23, 26.89; SOFTTW3 n=11, 20.95; SOFTTW5 n=16, 20.53; TMT n=5, 26.61; OMT n=12, 25.94; X8T n=3, 18.44; Tac RMT n=15, 30.59; RST n=7, 22.80). From "touch tightening system" to "last occlusion" was fastest with windlass rod systems when there were no tightening system understanding or mechanical problems (seconds: CAT7 n=48, 4.21; SOFTTW3 n=47, 5.99; SOFTTW5 n=44, 4.65; TMT n=38, 6.21; OMT n=51, 6.22; X8T n=48, 7.59; Tac RMT n=52, 8.44; RST n=40, 8.02). For occluded, tightening system secure applications, from "touch tightening system" to "Done" was fastest with self-securing tightening systems tightening from a tight strap (occluded, secure time in seconds from a tight strap: CAT7 n=17, 14.47; SOFTTW3 n=22, 10.91; SOFTTW5 n=38, 9.19; TMT n=14, 11.42; OMT n=44, 7.01; X8T n=12 9.82; Tac RMT n=20, 6.45; RST n=23, 8.64). CONCLUSIONS: Suboptimal processes in- crease application times. Optimal design features for fast, occlusive, secure tourniquet applications are self-securing strap/ redirect systems with an easily identified and easily used clip and self-securing tightening systems.

Assessing guidelines for the discontinuation of prehospital peripheral intravenous catheters.

Insertion of prehospital peripheral intravenous (PIV) catheters frequently occurs under suboptimal conditions. Timely replacement of prehospital PIV catheters may minimize the risk of inhospital catheter-related infections. Inconsistent recommendations exist concerning when prehospital PIV catheters should be replaced. The following study assessed compliance with hospital order sets for the discontinuation of prehospital PIV catheters in trauma patients and their associated complications. Results revealed 33.62% compliance with the trauma order set and 66.38% compliance with the hospital order set. Less than 1% of patients exhibited an associated complication. Guidelines for replacement of prehospital PIV catheters should focus less on time since insertion and more on patient factors.

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.

Driving with undiagnosed obstructive sleep apnea (OSA): High prevalence of OSA risk in drivers who experienced a motor vehicle crash.

Objective: Obstructive sleep apnea (OSA) is a risk factor for motor vehicle crashes (MVC), and patients with diagnosed OSA have a higher likelihood of being involved in a traffic accident. OSA, however, is often underdiagnosed in the general population. The purpose of this study was to assess the risk of undiagnosed OSA among hospitalized patients involved in MVCs.Methods: This is a prospective, observational pilot study of adult trauma patients admitted to a Level 1 trauma center after being the driver in a MVC. Patients were administered the STOP-Bang to assess risk of OSA and were asked questions about the circumstances of the MVC. Patients with a STOP-Bang score 5-8 were considered to be at high risk for OSA. Differences between variables were assessed using independent t-tests and chi-square.Results: Eighty patients participated in the study, and 26% (n = 21) were considered to be at high risk for OSA based on the STOP-Bang score. Compared to patients at low and intermediate risk, patients at high risk for OSA were significantly older (p < .001), had longer hospitalization (p = .06), and were less likely to discharge home from the hospital (p = .01). Patients at moderate and high risk had higher rates of hospital readmission within 1 year of discharge, when compared to the low risk group. Eighty-four percent of all crashes involved a single occupant (driver) in the vehicle, 58% involved only a single vehicle, and 40% occurred on a rural road. There were no significant differences between risk groups for number of vehicles involved in the accident, location of the accident, or number of vehicle occupants.Conclusions: Results of this pilot study suggest that more than one-quarter of drivers hospitalized after motor vehicle crashes were at high risk for OSA. Diagnosed or undiagnosed OSA is a significant public health concern and an established risk factor for motor vehicle accidents. Standardized screening for risk of sleep apnea should be considered by primary care physicians when guiding patients on health and behavior decisions, particularly in regards to driving and road safety.

Exploring Representation of Diverse Samples in fMRI Studies Conducted in Patients With Cardiac-Related Chronic Illness: A Focused Systematic Review.

Introduction/Purpose: Cardiovascular disease (CVD) is the leading cause of death worldwide, and in the United States alone, CVD causes nearly 840,000 deaths annually. Using functional magnetic resonance imaging (fMRI), a tool to assess brain activity, researchers have identified some brain-behavior connections and predicted several self-management behaviors. The purpose of this study was to examine the sample characteristics of individuals with CVD who participated in fMRI studies. Methods: A literature search was conducted in PubMed, CINAHL, and Scopus. No date or language restrictions were applied and research methodology filters were used. In October 2017, 1659 titles and abstracts were identified. Inclusion criteria were: (1) utilized an empirical study design, (2) used fMRI to assess brain activity, and (3) focused on patients with CVD-related chronic illness. Articles were excluded if they: were theory or opinion articles, focused on mental or neuropathic illness, included non-human samples, or were not written in English. After duplicates were removed (230), 1,429 titles and abstracts were reviewed based on inclusion criteria; 1,243 abstracts were then excluded. A total of 186 studies were reviewed in their entirety; after additional review, 142 were further excluded for not meeting the inclusion criteria. Forty-four articles met criteria and were included in the final review. An evidence table was created to capture the demographics of each study sample. Results: Ninety eight percent of the studies did not report the racial or ethnic composition of their sample. Most studies (66%) contained more men than women. Mean age ranged from 38 to 78 years; 77% reported mean age ≥50 years. The most frequently studied CVD was stroke (86%), while hypertension was studied the least (2%). Conclusion: Understanding brain-behavior relationships can help researchers and practitioners tailor interventions to meet specific patient needs. These findings suggest that additional studies are needed that focus on populations historically underrepresented in fMRI research. Researchers should thoughtfully consider diversity and purposefully sample groups by including individuals that are: women, from diverse backgrounds, younger, and diagnosed with a variety of CVD-related illnesses. Identifying and addressing these gaps by studying more representative samples will help healthcare providers reduce disparities and tailor interventions for all CVD populations.

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.

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.

A collaborative program to increase adult pneumococcal vaccination rates among a high-risk patient population receiving care at urgent care clinics.

OBJECTIVE: We report a project that utilized pharmacy students to increase pneumococcal vaccination rates in patients aged 19-64 years with high-risk medical conditions within urgent care clinics. The study also sought to better identify the number of patients previously vaccinated for pneumococcal disease. A total of 1,178 patients were considered eligible for pneumococcal vaccination during the study period, 287 (24.4%) of whom were determined to be previously vaccinated through chart assessment or patient interview. Of the remaining 891 patients, chart documentation of pneumococcal vaccination administered at the time of the urgent care visit was present for 96 patients (10.7%) in the intervention clinics compared with 6 patients in 2 control clinics who received the usual standard of care (P < .0001).

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.