The Effects of Acetazolamide on Exercise Performance at Sea Level and in Hypoxic Environments: A Review.

Lowlanders rapidly ascending to high altitude (>2500 m) often develop acute mountain sickness (AMS). While acclimatization is the most effective method of reducing symptoms of AMS (ie, headache, fatigue, nausea, gastrointestinal distress, etc.), it may take several days to become fully acclimated. Prophylactic use of acetazolamide (AZ), a carbonic anhydrase inhibitor, has become a popular alternative to staged acclimatization because it can be a less time-consuming method of reducing symptoms of AMS. While numerous studies have shown the effectiveness of AZ in mitigating the symptoms of AMS, a review of the existing literature regarding the effects of AZ on submaximal and maximal exercise performance at sea level and at altitude has not been performed. Literature search identified 17 peer reviewed articles examining the effects of AZ on exercise performance both at sea level and at altitude, as well as the associated side effects of prophylactic AZ use for the attenuation of AMS. This review finds that AZ treated cohorts experience a reduction in time to exhaustion during both submaximal and maximal exercise performance at sea level. At altitude, AZ treated cohorts' recorded widely variable submaximal and maximal exercise performance. At sea level, AZ impairs submaximal and maximal exercise performance. Due to the wide variation of findings of previously published studies, the effects of AZ on submaximal and maximal exercise performance at altitude remain unknown.

Enhancement of Cricothyroidotomy Education Using a Novel Technique: Cadaver Autografting.

BACKGROUND: Cricothyroidotomy is a lifesaving procedure required in up to 2% of emergent airways. Emergency medicine training programs frequently instruct this procedure via cadaver training, but cadaver cost and availability limit the opportunity for all trainees to perform the critical initial skin incision. Cadaver autografting is a novel way to simulate all steps of the procedure. OBJECTIVE: Our aim was to determine whether the technique of autografting cadaver tissue improves the experience of cricothyroidotomy simulation education for emergency medicine trainees. The investigators hypothesized that autografted cadaver tissue would be a useful adjunct. METHODS: In this prospective crossover study, volunteers were randomized to first perform cricothyroidotomy on previously incised native neck tissue or on autografted tissue, and then vice versa. The autograft consisted of cadaver iliotibial band covered with lateral thigh skin and subcutaneous tissue to simulate cricothyroid membrane and native anterior neck anatomy. Volunteer emergency medicine residents and sub-interns were included. Twenty-seven residents and nine students participated. Outcomes were evaluated via Likert scale. RESULTS: Thirty of 36 (83%) participants agreed or strongly agreed that they preferred cadaver autografting to the previously incised native tissue. Thirty-two of 36 (89%) agreed or strongly agreed that cadaver autografting was useful vs. 23 of 36 (64%) who answered similarly regarding previously incised native tissue (p = 0.001). Twenty-six of 36 (72%) were more comfortable with cricothyroidotomy in the emergency department after using cadaver autografting vs. 19 of 36 (53%) after using the native tissue (p = 0.003). CONCLUSIONS: Autografted cadaver tissue while simulating cricothyroidotomy was perceived to be a useful adjunct by the majority of participating emergency medicine trainees.

The emergent evaluation and treatment of hand injuries.

The hand is especially prone to traumatic injury. Some sources indicate that injuries to the hand account for somewhere between 10% and 30% of patients treated in emergency care settings. Fractures are the most common injury, followed by tendon injury, then skin lesions. Because the mechanism of injury often results in damage to multiple tissue structures, a detailed history and evaluation are vital to properly identifying and managing these injuries. This article provides the emergency physician with tools to identify and manage orthopedic injuries to the hand.

Emergency physician evaluation of a novel surgical cricothyroidotomy tool in simulated combat and clinical environments.

We sought to investigate the performance of a novel cricothyroidotomy CRIC device compared to the traditional surgical in both simulated combat environments and the emergency department (ED) setting. Twenty U.S. Army staff and resident emergency medicine physicians were randomized to device and simulated setting order and performed cricothyroidotomies in the standard manner and with the CRIC device via the TraumaMan surgical simulator in three simulated settings: the ED, a day combat environment, and a night combat environment. Differences in procedural completion for the two methods in different settings were compared by two-tailed paired t-tests. The occurrence of major and minor procedural complications and questions presented as 5-point Likert scales to describe participants' preferences of cricothyroidotomy methods were compared by chi2 analysis. Time to incision, time to procedural completion, and rate of major and minor complications were not significantly different between the standard surgical method and the CRIC device (p > 0.05). In the simulated ED setting, 60% of participants preferred the standard surgical method (95% confidence interval: 38.5-81.5), whereas in the simulated combat settings, 50% of participants preferred each device (95% confidence interval: 28.1-71.9). In our population, we observed similar operator performance characteristics and physician preferences between the 2 methods in all simulated cricothyroidotomy settings.

Use of handheld sonar to locate a missing diver.

OBJECTIVE: The purpose of this study was to investigate whether a handheld sonar device significantly reduces the mean time needed to locate a missing diver. METHODS: This institutional review board approved, prospective, crossover study used a voluntary convenience sample of 10 scuba divers. Participants conducted both a standard and modified search to locate a simulated missing diver. The standard search utilized a conventional search pattern starting at the point where the missing diver (simulated) was last seen. The modified search used a sonar beacon to augment the search. For each search method, successful completion of the search was defined as locating the missing diver within 40 minutes. RESULTS: Twenty total dives were completed. Using a standard search pattern, the missing diver was found by only 1 diver (10%), taking 18 minutes and 45 seconds. In the sonar-assisted search group, the missing diver was found by all 10 participants (100%), taking an average of 2 minutes and 47 seconds (SD 1 minute, 20 seconds). Using the nonparametric related samples Wilcoxon signed rank test, actual times between the sonar group and the standard group were significant (P < .01). Using paired samples t tests, the sonar group's self-assessed confidence increased significantly after using the sonar (P < .001), whereas the standard group decreased in confidence (not statistically significant, P = .111). CONCLUSIONS: Handheld sonar significantly reduces the mean duration to locate a missing diver as well as increasing users' confidence in their ability to find a missing diver when compared with standard search techniques.

Is point-of-care ultrasound accurate and useful in the hands of military medical technicians? A review of the literature.

Over the past decade, point-of-care ultrasound (US) use by nonphysician providers has grown substantially. The purpose of this article is to (1) summarize the literature evaluating military medics' facility at US, (2) more clearly define the potential utility of military prehospital US technology, and (3) lay a pathway for future research of military prehospital US. The authors performed a keyword search using multiple search engines. Each author independently reviewed the search results and evaluated the literature for inclusion. Of 30 studies identified, five studies met inclusion criteria. The applications included evaluation of cardiac activity, pneumothorax evaluation, and fracture evaluation. Additionally, a descriptive study demonstrated distribution of US exam types during practical use by Army Special Forces Medical Sergeants. No studies evaluated retention of skills over prolonged periods. Multiple studies demonstrate the feasibility of training military medics in US. Even under austere conditions, the majority of studies conclude that medic can perform US with a high degree of accuracy. Lessons learned from these studies tend to support continued use of US in out-of-hospital settings and exploration of the optimal curriculum to introduce this skill.

Lemierre syndrome complicating otitis externa: case report and literature review.

BACKGROUND: Septic thrombophlebitis of the internal jugular vein, known as Lemierre syndrome, is a rare disorder usually caused by Fusobacterium necrophorum, a Gram-negative anaerobic organism that normally inhabits the oropharynx. Lemierre syndrome usually follows primary oropharyngeal infections and affects previously healthy adolescents and young adults in a characteristic manner, often with fatal results if left untreated. There have been a significantly increasing number of reported cases of Lemierre syndrome, possibly reflecting the trend to withhold antibiotics for initially uncomplicated oropharyngeal infections. OBJECTIVES: We hope to alert the reader to a potentially fatal disease process that has recently been increasingly identified, by reporting a unique manifestation of Lemierre syndrome, and by reviewing the current literature. CASE REPORT: A 19-year-old woman presented to our Emergency Department with a chief complaint of fever, ear pain, and generalized weakness. She was noted to be in septic shock, with left neck erythema and swelling. A computed tomography scan showed thrombosis of the left internal jugular vein (IJV), which was later excised. She recovered after a course of intravenous and oral antibiotics. CONCLUSION: Septic thrombophlebitis of the IJV is associated with multiple sources and organisms. This case is unique in both the organism (Peptococcus anaerobius) and the source (otitis externa). This disease process must be identified early and aggressively treated to avoid significant morbidity and mortality.

A blinded, randomized, palatability study comparing variations of 2 popular field water disinfection tablets.

OBJECTIVE: Halogen-based water disinfection tablets may render an unpleasant taste to treated water. Proposed safe additives such as ascorbic acid may reduce this objectionable taste. We compared the palatability of 2 field water disinfectants: iodine-based tetraglycine hydroperiodide (TGHP) and chlorine-based chlorine dioxide (CD) both with and without the concomitant use of an ascorbic acid taste neutralizer. METHODS: Blinded participants randomly sampled 5 different distilled water samples containing combinations of disinfectant tablets and ascorbic acid: 1) water; 2) water with TGHP; 3) water with CD; 4) water with TGHP plus ascorbic acid; and 5) water with CD plus ascorbic acid. Participants rated beverage taste via a 100 mm visual analogue scale (VAS) and ranked the samples from "most pleasant" to "least pleasant." RESULTS: Sixty participants evaluated the samples. On the VAS, water with TGHP tasted worst and water with CD tasted second worst. Water with TGHP plus ascorbic acid, water alone, and water with CD plus ascorbic acid measured similarly as significantly best tasting. Water with TGHP was ranked by 58% as "least pleasant" tasting, while water with TGHP and ascorbic acid was ranked by 40% as "most pleasant" tasting. CONCLUSIONS: Participants found halogen-based disinfected water significantly less palatable prior to the addition of ascorbic acid. Addition of ascorbic acid to treated water created a beverage of similar preference to distilled water. These results may increase compliance with the use of disinfecting tablets by increasing the palatability of drinking water made potable via addition of ascorbic acid to halogen-based chemical disinfection.

10% Povidone-iodine may be a practical field water disinfectant.

OBJECTIVE: A paucity of data exists regarding the use of iodophores such as povidone-iodine (PVI) to disinfect water. We sought to determine a practical minimal disinfecting concentration of 10% PVI over different contact times and temperatures when added to water inoculated with E. coli. METHODS: 1:100, 1:1,000, and 1:10,000 dilutions of 10% PVI were created. Escherichia coli was exposed to these dilutions for 5, 15, and 30 minutes at 10, 20, and 30°C. Bactericidal activity was neutralized with 0.5% sodium thiosulfate. Mean viable colony forming units (CFUs) was determined after triplicate plating on Luria-bertani agar and 24 hours of incubation at 37°C. Effective bactericidal activity was defined as a 5-log reduction. RESULTS: Of the 200,000 E. coli plated, no CFUs were observed after exposure to the 1:100 dilution. After 5 minutes of contact time with the 1:1,000 dilution, at 10°C CFUs were too numerous to count (TNTC), at 20°C the mean CFU count was 92 (standard error ±11), and at 30°C the mean CFU count was 25 (standard error ±8). No CFUs were observed after 15 minutes of exposure to the 1:1,000 dilution across experimental temperatures. The 1:10,000 dilution always yielded CFU growth that was TNTC. CONCLUSIONS: The lowest disinfecting concentration of 10% PVI was the 1:1,000 dilution at 15 minutes of contact time. This supports the use of PVI for water disinfection against E. coli, the organism most commonly responsible for traveler's diarrhea. Further studies may assess its effectiveness against more virulent water borne pathogens.

Emergency department presentation of a rare neurological disorder.

The treatment and disposition of patients with neurological disorders is commonplace in the emergency setting, but atypical and uncommon presentations can prove to be especially challenging. In this article we discuss the case of a 31-year-old woman who presented with a rare disorder known as opsoclonus myoclonus syndrome (OMS). OMS is characterized by involuntary, multidirectional movement of the eyes, myoclonus, and truncal ataxia. The etiology is thought to be autoimmune, and is most commonly associated with encephalitis or paraneoplastic syndrome. After an 8-day hospital course, which included several different treatment modalities including plasmapheresis, the patient was discharged after making a complete recovery. Unusual presentations such as the one described in this article illustrate the point that it is crucial to have a systematic approach that can be applied to identify and treat potentially life-threatening neurological conditions.

A prospective analysis of the treatment of friction blisters with 2-octylcyanoacrylate.

Early military investigations of blister treatment using tissue adhesives have shown promise, finding that these agents provide pain relief, prevent infection, and allow continuation of recruit training. A trial was conducted to compare a 2-octylcyanoacrylate treatment with military standard therapy. Patients were recruited during foot evaluation at the end of a 10-km military road march. Seventy-five patients were screened, and 51 were enrolled. Twenty-six patients received 2-octylcyanoacrylate and 25 received standard treatment. A total of 80 blisters were treated (40 in each group). The mean (SD) blister size in the 2-octylcyanoacrylate group was 12.7 (6.2) mm and in the standard group was 12.0 (5.7) mm. There were no statistically significant differences in any of the baseline variables. Baseline and repeated-measures visual analog scale scores demonstrated no statistically significant differences in initial or repeat pain scores. Both groups showed a similar change across time, with a nonsignificant trend toward improvement in the standard therapy group at 10 min (28.5 versus 24.9) and in the 2-octylcyanoacrylate group at 3 days (42.9 versus 50.1). Mean Likert scores were similar, indicating no difference in patient satisfaction. Time to resumption of normal activity was similar, with one patient in each group unable to return to activity at the time of follow-up. There was a trend toward an increased proportion of patients in the 2-octylcyanoacrylate group who were able to return to normal activity within 48 hours, but this did not reach statistical significance. 2-Octylcyanoacrylate was associated with a greater degree of procedural discomfort. No infected blisters were noted in either group.

Treatment of imported fire ant stings with mitigator sting and bite treatment--a randomized control study.

OBJECTIVE: To evaluate the efficacy of the commercially available product Mitigator Sting and Bite Treatment in reducing the pain after imported fire ant stings. METHODS: Twenty-four volunteer subjects were exposed to imported fire ant stings on both fore-arms. The subjects received Mitigator paste on 1 arm and calamine lotion on the opposite arm, in a blinded manner, from 90 seconds to 10 minutes after exposure. Subjects recorded pain on a 100-mm visual analog scale 60 seconds, 20 minutes, and 3 days after exposure. A 2-tailed paired t test was used to compare the difference in reduction of pain over time between the Mitigator-treated arms and the calamine-treated arms. RESULTS: At 60 seconds, the mean visual analog scale pain score was 23.9 mm for the Mitigator group and 24.5 mm for the calamine group. At 20 minutes, the mean score was 7.6 mm (delta = 16.3) for the Mitigator group and 12.7 mm (delta = 11.8) for the calamine group. At 3 days, the mean score was 2.4 mm (delta = 21.5) for the Mitigator group and 2.9 mm (delta = 21.6) for the calamine group. There was no significant difference between groups for change in visual analog scale pain score at 60 seconds, 20 minutes (P = .256), or 3 days (P = .64). CONCLUSIONS: There was no significant difference in pain relief between calamine and Mitigator for imported fire ant stings.

A poly(propylene glycol-co-fumaric acid) based bone graft extender for lumbar spinal fusion: in vivo assessment in a rabbit model.

STUDY DESIGN: An animal model of posterolateral intertransverse process lumbar spinal fusion compared fusion rates amongst autologous bone (group 1), a porous, bioabsorbable, scaffold based on the biopolymer, poly(propylene glycol-co-fumaric acid) (PPF) (group 2), and a combination of autograft and the bioabsorbable scaffold (group 3). OBJECTIVES: To evaluate the feasibility of augmenting spinal fusion with an osteoconductive and bioabsorbable scaffold as an alternative or as an adjunct, i.e., an extender, to autograft. SUMMARY OF BACKGROUND DATA: There is little preclinical data on applications of bioabsorable bone graft extenders in spinal fusion. METHODS: New Zealand White rabbits underwent single-level lumbar posterolateral intertransverse process fusion. Animals were treated with one of three materials: autologous bone (group 1), a bioabsorable material based on PPF (group 2), and the PPF biopolymer scaffold with autologous bone graft (group 3). Animals were evaluated at 6 weeks, and fusion was evaluated by manual palpation, and radiographic, histologic, and histomorphometric analyses. RESULTS: Radiographic and manual palpation showed evidence of fusion in all three groups. Histomorphometric measurement of bone ingrowth showed the highest quantity of new bone in group 3 (91%), followed by group 1 (72%) and group 2 (53%). CONCLUSIONS: Results of this study suggested that osteoconductive bioabsorbable scaffolds prepared from PPF might be used as an autograft extender when applied as an adjunct to spinal fusion.

Dimensional stability of the alveolar ridge after implantation of a bioabsorbable bone graft substitute: a radiographic and histomorphometric study in rats.

This study evaluated reconstruction of the alveolar ridge after molar extraction in rats with bioabsorbable bone repair scaffolds. The material was prepared from the unsaturated polyester poly(propylene glycol-co-fumaric acid) (PPF), which may be cured in situ to form a porous scaffold. The intention is to use this material either as a stand-alone bone graft substitute or as an extender to autograft harvested from mandibular reconstruction sites. The bioactivity of the graft substitute was investigated in a rat residual ridge resorption model. PPF bone repair material was injected into the defect site, where it cross-linked in situ in the presence of a hydroxyapatite (HA) filler and effervescent agents. The PPF-based material develops porosity during an in situ cure by generating carbon dioxide during the effervescent reaction of citric acid and sodium bicarbonate. The incorporation of HA promotes osteoconduction within the bone repair scaffold. In this study, bioactivity of the porous scaffold was evaluated as a function of HA particle size (micrometer-sized vs nanometer-sized particles). The maxillary or mandibular molars on the right side were extracted from 96 adult Sprague-Dawley rats. A 2-mm round bur was used to create a uniform trench defect measuring 2 mm in diameter, 2 mm in depth, and 4 mm in length at each extraction site. The defect site was (1) treated with PPF bone repair material containing nanometer-sized HA, (2) treated with PPF material containing micrometer-sized HA, (3) treated with demineralized freeze-dried bone allograft, or (4) left untreated. Rats were sacrificed at 2, 4, 7, and 12 weeks postoperative. Resorption of the residual alveolar ridge was assessed by radiographic outcomes. Bone ingrowth through the defect site was measured by histomorphometric outcomes. Mandibular and maxillary ridge heights increased for all treatments used in this study. There were no clinical indications that addition of either of the PPF bone repair materials retarded hard- or soft-tissue healing of the extraction sites. Although not statistically significant, the mandibular defects treated with PPF containing nanometer-sized HA healed at a faster rate as determined by ridge height and new bone formation measurements when compared with the other treatments. These findings suggest the feasibility of using PPF bone graft substitutes for oral-maxillofacial applications.

An injectable porous poly(propylene glycol-co-fumaric acid) bone repair material as an adjunct for intramedullary fixation.

A bioresorbable bone repair material made from the unsaturated polyester poly(propylene glycol-co-fumaric acid), PPF, was investigated for its potential to act as an adjunct to alleviate the disadvantages associated with wire fixation. The PPF bone repair material is an injectable system that can be delivered to the intramedullary site and crosslinked in the presence of a hydroxylapatite filler and effervescent agents. To test the feasibility of using a bioabsorbable material as an adjunct in fracture fixation, femoral osteotomies were created in two groups of 10 Sprague-Dawley rats. Osteotomies were fixed with a threaded Kirschner wire or stabilized with a Kirshner wire augmented with the PPF bone repair material. The quantity of new bone across the osteotomy site was assessed at 4 weeks postoperatively. Histologic analysis of the healing process revealed enhanced osteoconduction across the osteotomy with the PPF bone repair material. These findings were corroborated by histomorphometric analysis of new bone formation. These findings imply suitability of the PPF bone repair material to act as an adjunct to wire fixation, such as techniques used in hand surgery.

Prediction of resorption rates for composite polylactide/hydroxylapatite internal fixation devices based on initial degradation profiles.

Mechanical and physicochemical outcomes were used to predict the resorption rate of polylactide-based internal fixation devices with and without incorporation of an osteoconductive buffer. Devices were degraded in vitro for 1 year. Addition of an osteoconductive buffer to a resorbable polymer internal fixation device controlled the rate of acid generation resulting from polymer hydrolysis. The pH of the physiological buffer remained neutral when it was exposed to the buffered screw, whereas the pH decreased to approximately 3.0 for the polylactide device. Neutralizaton of the acids generated during polymer hydrolysis increased the projected resorption time of the buffered device to 104 weeks in comparison to 71 weeks for a similar screw made from polylactide. In addition, the buffered device retained a higher percentage of its initial flexural strength throughout the course of degradation than the polylactide screw. The flexural strength of the polylactide screw decreased 20% during the first 4 weeks of polymer degradation, whereas the buffered device maintained its initial mechanical properties through 16 weeks of degradation.

Enhanced peripheral nerve regeneration through a poled bioresorbable poly(lactic-co-glycolic acid) guidance channel.

In this study we investigated the effects of materials prepared with electrical poling on neurite outgrowth in vitro and nerve regeneration in vivo. Neuro-2a cells were seeded on poled and unpoled poly(lactic-co-glycolic) (PLGA) films and observed at time periods 24, 48 and 72 h post-seeding. The percentage of cells with neurites and the neurites per cell were quantified using light microscopy. At 48 and 72 h post-seeding, both the number of cells with neurites and the neurites per cell were significantly increased on the poled films compared to those on unpoled films. An established rat sciatic nerve model was used for in vivo studies to assess the effects of PLGA guides, poled for two different periods, on peripheral nerve regeneration. Guides were inserted in rats to bridge a 1.0 cm gap created in the right sciatic nerve. After four weeks, nerves regenerated through poled guides displayed a significant increase in conduction velocity and significantly increased numbers of axons across the guides, as compared to nerves regenerating through an unpoled guidance channel. Electrical poling was shown to promote neurite growth, axon regeneration and the conduction rate of the repaired nerve. We concluded that guides prepared with electrical poling enhance peripheral nerve regeneration.

Solvent-free protein encapsulation within biodegradable polymer foams.

Microporous poly(D,L-lactide-co-glycolide) matrices containing encapsulated proteins were fabricated in a solvent-free manner. Microporous foam was generated by saturating a mixture of polymer and protein particles in supercritical carbon dioxide (SC-CO2), dispersing the protein particles in the polymer melt followed by a rapid evaporation of the CO2 phase. The release rates of protein encapsulated within porous poly(lactide-co-glycolide)(PLGA) constructs produced in SC-CO2 were measured in vitro. Although a substantial amount of protein was released within the first 48 h, results indicated that protein may be dispersed throughout the polymer phase and released over 3 weeks using this solvent-free technique. Basic fibroblast growth factor (bFGF), known to promote angiogenesis in vivo, was encapsulated within the polymer matrix. In addition, retention of biological activity was measured for bFGF encapsulated within PLGA foams. Encapsulated bFGF was released from the porous constructs for up to 10 days in vitro with little loss of biological activity.

Mechanical evaluation of a porous bone graft substitute based on poly(propylene glycol-co-fumaric acid).

A porous, resorbable polymer composite based on poly(propylene glycol-co-fumaric acid) (PPF) was mechanically evaluated in vitro for use as a bone graft substitute and fracture fixative. The test material created a dynamic system capable of initially providing mechanical integrity to bony voids and a degradative mechanism for ingrowth by native bone. The unsaturated polymer, PPF, was crosslinked in the presence of effervescent agents to yield a porous microstructure upon curing. An in vitro degradation study first assessed the temporal mechanical properties of the test material. This research was followed by an ex vivo study using a long-bone osteotomy model to characterize the mechanics of fixation. Results showed the initial compressive strength of the cross-linked PPF system was comparable to cancellous bone. The rate of strength loss was commensurate with the predicted mechanical recovery of healing bone with analogous results in a composite that comprised also 25% (by weight) autograft. Mechanical testing in the long-bone model demonstrated that PPF-based bone-graft substitute increased the flexural strength of K-wire stabilized osteotomies. These results suggest that this type of bone graft substitute may have clinical utility in the stabilization of complex tubular bone fractures.