Sarah R. Williams

Acetazolamide fails to decrease pulmonary artery pressure at high altitude in partially acclimatized humans.

In this randomized, double-blind placebo controlled trial our objectives were to determine if acetazolamide is capable of preventing high altitude pulmonary edema (HAPE) in trekkers traveling between 4250 m (Pheriche)\4350 m (Dingboche) and 5000 m (Lobuje) in Nepal; to determine if acetazolamide decreases pulmonary artery systolic pressures (PASP) at high altitude; and to determine if there is an association with PASP and signs and symptoms of HAPE. Participants received either acetazolamide 250 mg PO BID or placebo at Pheriche\Dingboche and were reassessed in Lobuje. The Lake Louise Consensus Criteria were used for the diagnosis of HAPE, and cardiac ultrasonography was used to measure the velocity of tricuspid regurgitation and estimate PASP. Complete measurements were performed on 339 of the 364 subjects (164 in the placebo group, 175 in the acetazolamide group). No cases of HAPE were observed in either study group nor were differences in the signs and symptoms of HAPE found between the two groups. Mean PASP values did not differ significantly between the acetazolamide and placebo groups (31.3 and 32.6 mmHg, respectively). An increasing number of signs and symptoms of HAPE was associated with elevated PASP (p < 0.01). The efficacy of acetazolamide against acute mountain sickness, however, was significant with a 21.9% incidence in the placebo group compared to 10.2 % in the acetazolamide group (p < 0.01). Given the lack of cases of HAPE in either group, we can draw no conclusions about the efficacy of acetazolamide in preventing HAPE, but the absence of effect on PASP suggests that any effect may be minor possibly owing to partial acclimatization during the trek up to 4200 m.

PITFALLS IN THE USE OF OCULAR ULTRASOUND FOR EVALUATION OF ACUTE VISION LOSS

BACKGROUND Retinal detachment is a true medical emergency. It is a time-critical, vision-threatening disease often first evaluated in the Emergency Department (ED). Diagnosis can be extremely challenging and confused with other ocular pathology. Several entities can mimic retinal detachment, including posterior vitreous detachment and vitreous hemorrhage. Ocular ultrasound can assist the emergency physician in evaluating intraocular pathology, and it is especially useful in situations where fundoscopic examination is technically difficult or impossible. Accurate and rapid diagnosis of retinal detachment can lead to urgent consultation and increase the likelihood of timely vision-sparing treatment. OBJECTIVES This case demonstrates both the utility of ocular ultrasound in the accurate and timely diagnosis of retinal detachment and potential pitfalls in the evaluation of intraocular pathology in the ED. CASE REPORT A 38-year-old woman presented with acute onset of bilateral visual loss that was concerning for retinal detachment. Rapid evaluation of the intraocular space was performed using bedside ocular ultrasound. Bedside ocular ultrasound correctly diagnosed retinal detachment in the right eye. Posterior vitreous detachment in the left eye was incorrectly diagnosed as retinal detachment. CONCLUSION This case illustrates the importance of bedside ocular ultrasound and highlights some of the pitfalls that can occur when evaluating for retinal detachment. Following is a discussion regarding methods to distinguish retinal detachment from vitreous hemorrhage and posterior vitreous detachment.

Optic Nerve Sheath Diameter Increase on Ascent to High Altitude: Correlation With Acute Mountain Sickness.

Elevated optic nerve sheath diameter on sonography is known to correlate with increased intracranial pressure and is observed in acute mountain sickness. This study aimed to determine whether optic nerve sheath diameter changes on ascent to high altitude are associated with acute mountain sickness incidence.

Sonographic Identification of Tube Thoracostomy Study (SITTS): Confirmation of Intrathoracic Placement

Introduction Thoracostomy tubes (TT) are commonly placed in the management of surgical, emergency, and trauma patients and chest radiographs (CXR) and computed tomography (CT) are performed to confirm placement. Ultrasound (US) has not previously been used as a means to confirm intrathoracic placement of chest tubes. This study involves a novel application of US to demonstrate chest tubes passing through the pleural line, thus confirming intrathoracic placement. Methods This was an observational proof-of-concept study using a convenience sample of patients with TTs at a tertiary-care university hospital. Bedside US was performed by the primary investigator using first the low-frequency (5–1 MHz) followed by the high-frequency (10–5 MHz) transducers, in both 2-dimensional gray-scale and M-modes in a uniform manner. The TTs were identified in transverse and longitudinal views by starting at the skin entry point and scanning to where the TT passed the pleural line, entering the intrathoracic region. All US images were reviewed by US fellowship-trained emergency physicians. CXRs and CTs were used as the standard for confirmation of TT placement. Results Seventeen patients with a total of 21 TTs were enrolled. TTs were visualized entering the intrathoracic space in 100% of cases. They were subjectively best visualized with the high-frequency (10–5 MHz) linear transducer. Sixteen TTs were evaluated using M-mode. TTs produced a distinct pattern on M-mode. Conclusion Bedside US can visualize the TT and its entrance into the thoracic cavity and it can distinguish it from the pleural line by a characteristic M-mode pattern. This is best visualized with the high-frequency (10–5 MHz) linear transducer.

Development and evaluation of standardized narrative cases depicting the general surgery professionalism milestones.

Purpose Residency programs now are required to use educational milestones, which has led to the need for new methods of assessment. The literature suggests that narrative cases are a promising tool to track residents’ progress. This study demonstrates the process for developing and evaluating narrative cases representing the five levels of the professionalism milestones. Method In 2013, the authors identified 28 behaviors in the Accreditation Council for Graduate Medical Education general surgery professionalism milestones. They modified previously published narrative cases to fit these behaviors. To evaluate the quality of these cases, the authors developed a 28-item, five-point scale instrument, which 29 interdisciplinary faculty completed. The authors compared the faculty ratings by narrative case and specialty with the authors’ initial rankings of the cases by milestone level. They used t tests and analysis of variance to compare mean scores across specialties. Results The authors developed 10 narrative cases, 2 for each of the 5 milestone levels. Each case contained at least 20 of the 28 behaviors identified in the milestones. Mean faculty ratings matched the milestone levels. Reliability was good (G coefficient = 0.86, phi coefficient = 0.85), indicating consistency in raters’ ability to determine the proper milestone level for each case. Conclusions The authors demonstrate a process for using specialty-specific milestones to develop narrative cases that map to a spectrum of professionalism behaviors. This process can be applied to other competencies and specialties to facilitate faculty awareness of resident performance descriptors and provide a frame of reference for milestones assessment.

Regional vs Systemic Antivenom Administration in the Treatment of Snake Venom Poisoning in a Rabbit Model: A Pilot Study ☆

OBJECTIVE To develop a model that compares 2 different routes of antivenom administration (standard intravenous [IV] administration vs regional administration below a tourniquet) to assess their ability to limit muscle necrosis in a rabbit model of rattlesnake venom poisoning. METHODS New Zealand white rabbits were randomly assigned to 4 groups. All animals underwent general anesthesia and were then injected intramuscularly (IM) with a sublethal dose of western diamond-back rattlesnake (Crotalus atrox) venom in the right thigh and a similar volume of normal saline (NS) control in the left thigh. Thirty minutes later, standard treatment group animals (n = 4) received 1 vial of reconstituted Antivenin (Crotalidae) Polyvalent (ACP) and 10 mL of NS through an ear vein. Experimental treatment group animals (n = 4) had their lower extremities exsanguinated and isolated by arterial tourniquets. One vial of ACP was then given through a distal IV in the envenomed extremity, and 10 mL of NS was given through an IV in the sham extremity. Tourniquets were removed 30 minutes later. Positive control group animals (n = 2) similarly had their lower extremities exsanguinated and isolated by tourniquets. They then received 10 mL of NS through distal IVs in each lower extremity. Tourniquets were again removed after 30 minutes. Negative control group animals (n = 2) received 2 doses of NS only (10 mL each) through an ear vein. Serum creatinine phosphokinase (CPK) levels were drawn at baseline and 48 hours following venom injection. At 48 hours, the animals were injected with technetium pyrophosphate. Two hours later, they were euthanized, and the lower extremities were scanned to determine levels of radionucleotide uptake in envenomed muscles compared to contralateral sham-injected muscles. The anterior thigh muscle groups were then removed, fixed, stained, sectioned, and analyzed in a blinded fashion by a veterinary pathologist for muscle necrosis grading. RESULTS There was no evidence of statistically significant differences in changes in serum CPK levels (from baseline to 48 hours), technetium pyrophosphate uptake ratios (right leg/left leg), or muscle necrosis indices in any 2-group analysis. CONCLUSIONS Results of this pilot study do not suggest any beneficial effect of ACP, in the dose and routes used, in limiting local muscle necrosis following IM rattlesnake venom poisoning in the rabbit model.

Prehospital Evaluation of Effusion, Pneumothorax, and Standstill (PEEPS): Point-of-care Ultrasound in Emergency Medical Services.

Introduction In the United States, there are limited studies regarding use of prehospital ultrasound (US) by emergency medical service (EMS) providers. Field diagnosis of life-threatening conditions using US could be of great utility. This study assesses the ability of EMS providers and students to accurately interpret heart and lung US images. Methods We tested certified emergency medical technicians (EMT-B) and paramedics (EMT-P) as well as EMT-B and EMT-P students enrolled in prehospital training programs within two California counties. Participants completed a pre-test of sonographic imaging of normal findings and three pathologic findings: pericardial effusion, pneumothorax, and cardiac standstill. A focused one-hour lecture on emergency US imaging followed. Post-tests were given to all EMS providers immediately following the lecture and to a subgroup one week later. Results We enrolled 57 prehospital providers (19 EMT-B students, 16 EMT-P students, 18 certified EMT-B, and 4 certified EMT-P). The mean pre-test score was 65.2%±12.7% with mean immediate post-test score of 91.1%±7.9% (95% CI [22%–30%], p<0.001). Scores significantly improved for all three pathologic findings. Nineteen subjects took the one-week post-test. Their mean score remained significantly higher: pre-test 65.8%±10.7%; immediate post-test 90.5%±7.0% (95% CI [19%–31%], p<0.001), one-week post-test 93.1%±8.3% (95% CI [21%–34%], p<0.001). Conclusion Using a small sample of EMS providers and students, this study shows the potential feasibility for educating prehospital providers to accurately identify images of pericardial effusion, pneumothorax, and cardiac standstill after a focused lecture.

D-dimer is not elevated in asymptomatic high altitude climbers after descent to 5340 m: the Mount Everest Deep Venous Thrombosis Study (Ev-DVT).

We performed this study to determine the prevalence of elevated D-dimer, a marker for deep venous thrombosis (DVT), in asymptomatic high altitude climbers. On-site personnel enrolled a convenience sample of climbers at Mt. Everest Base Camp (Nepal), elevation 5340 m (17,500 ft), during a single spring climbing season. Subjects were enrolled after descent to base camp from higher elevation. The subjects completed a questionnaire to evaluate their risk factors for DVT. We then performed a D-dimer test in asymptomatic individuals. If the D-dimer test was negative, DVT was considered ruled out. Ultrasound was available to perform lower-extremity compression ultrasounds to evaluate for DVT in case the D-dimer was positive. We enrolled 76 high altitude climbers. None had a positive D-dimer test. The absence of positive D-dimer tests suggests a low prevalence of DVT in asymptomatic high altitude climbers.

Caudal Edge of the Liver in the Right Upper Quadrant (RUQ) View Is the Most Sensitive Area for Free Fluid on the FAST Exam.

Introduction The focused assessment with sonography in trauma (FAST) exam is a critical diagnostic test for intraperitoneal free fluid (FF). Current teaching is that fluid accumulates first in Morison’s pouch. The goal of this study was to evaluate the “sub-quadrants” of traditional FAST views to determine the most sensitive areas for FF accumulation. Methods We analyzed a retrospective cohort of all adult trauma patients who had a recorded FAST exam by emergency physicians at a Level I trauma center from January 2012 – June 2013. Ultrasound fellowship-trained faculty with three emergency medicine residents reviewed all FAST exams. We excluded studies if they were incomplete, of poor image quality, or with incorrect medical record information. Positive studies were assessed for FF localization, comparing the traditional abdominal views and on a sub-quadrant basis: right upper quadrant (RUQ)1 - hepato-diaphragmatic; RUQ2 - Morison’s pouch; RUQ3 - caudal liver edge and superior paracolic gutter; left upper quadrant (LUQ)1 - splenic-diaphragmatic; LUQ2 - spleno-renal; LUQ3 – around inferior pole of kidney; suprapubic area (SP)1 - bilateral to bladder; SP2 - posterior to bladder; SP3 – posterior to uterus (females). FAST results were confirmed by chart review of computed tomography results or operative findings. Results Of the included 1,008 scans, 48 (4.8%) were positive. The RUQ was the most positive view with 32/48 (66.7%) positive. In the RUQ sub-quadrant analysis, the most positive view was the RUQ3 with 30/32 (93.8%) positive. Conclusion The RUQ is most sensitive for FF assessment, with the superior paracolic gutter area around the caudal liver edge (RUQ3) being the most positive sub-quadrant within the RUQ.

Change in Intraocular Pressure During Point-of-Care Ultrasound

Introduction Point-of-care ocular ultrasound (US) is a valuable tool for the evaluation of traumatic ocular injuries. Conventionally, any maneuver that may increase intraocular pressure (IOP) is relatively contraindicated in the setting of globe rupture. Some authors have cautioned against the use of US in these scenarios because of a theoretical concern that an US examination may cause or exacerbate the extrusion of intraocular contents. This study set out to investigate whether ocular US affects IOP. The secondary objective was to validate the intraocular pressure measurements obtained with the Diaton® as compared with standard applanation techniques (the Tono-Pen®). Methods We enrolled a convenience sample of healthy adult volunteers. We obtained the baseline IOP for each patient by using a transpalpebral tonometer. Ocular US was then performed on each subject using a high-frequency linear array transducer, and a second IOP was obtained during the US examination. A third IOP measurement was obtained following the completion of the US examination. To validate transpalpebral measurement, a subset of subjects also underwent traditional transcorneal applanation tonometry prior to the US examination as a baseline measurement. In a subset of 10 patients, we obtained baseline pre-ultrasound IOP measurements with the Diaton® and Tono-Pen®, and then compared them. Results The study included 40 subjects. IOP values during ocular US examination were slightly greater than baseline (average +1.8mmHg, p=0.01). Post-US examination IOP values were not significantly different than baseline (average −0.15mmHg, p=0.42). In a subset of 10 subjects, IOP values were not significantly different between transpalpebral and transcorneal tonometry (average +0.03mmHg, p=0.07). Conclusion In healthy volunteer subjects, point-of-care ocular US causes a small and transient increase in IOP. We also showed no difference between the Diaton® and Tono-Pen® methods of IOP measurement. Overall, the resulting change in IOP with US transducer placement is considerably less than the mean diurnal variation in healthy subjects, or pressure generated by physical examination, and is therefore unlikely to be clinically significant. However, it is important to take caution when performing ocular ultrasound, since it is unclear what the change in IOP would be in patients with ocular trauma.