Surveillance for jugular venous thrombosis in astronauts.

BACKGROUND: Thrombosis of the left internal jugular vein in an astronaut aboard the International Space Station was recently described, incidentally discovered during a research study of blood flow in neck veins in microgravity. Given this event, and the high incidence of flow abnormalities, the National Aeronautics and Space Administration (NASA) instituted an occupational surveillance program to evaluate astronauts for venous thrombosis. METHODS: Duplex ultrasound of the bilateral internal jugular veins was conducted on all NASA astronauts terrestrially, and at three points during spaceflight. Respiratory maneuvers were performed. Images were analyzed for thrombosis and certain hemodynamic characteristics, including peak velocity and degree of echogenicity. RESULTS: Eleven astronauts were evaluated with matching terrestrial and in-flight ultrasounds. No thrombosis was detected. Compared to terrestrial ultrasound measurements, in-flight peak velocity was reduced and lowest in the left. Six of 11 astronauts had mild-moderate echogenicity in the left internal jugular vein during spaceflight, but none had more than mild echogenicity in the right internal jugular vein. Two astronauts developed retrograde blood flow in the left internal jugular vein. CONCLUSION: Abnormal flow characteristics in microgravity, most prominent in the left internal jugular vein, may signal an increased risk for thrombus formation in some individuals.

The effect of microgravity on the human venous system and blood coagulation: a systematic review.

NEW FINDINGS: What is the central question of this study? Recently, an internal jugular venous thrombus was identified during spaceflight: does microgravity induce venous and/or coagulation pathophysiology, and thus an increased risk of venous thromboembolism (VTE)? What is the main finding and its importance? Whilst data are limited, this systematic review suggests that microgravity and its analogues may induce an enhanced coagulation state due to venous changes most prominent in the cephalad venous system, as a consequence of changes in venous flow, distension, pressures, endothelial damage and possibly hypercoagulability in microgravity and its analogues. However, whether such changes precipitate an increased VTE risk in spaceflight remains to be determined. ABSTRACT: Recently, an internal jugular venous thrombus was identified during spaceflight, but whether microgravity induces venous and/or coagulation pathophysiology, and thus, an increased risk of venous thromboembolism (VTE) is unclear. Therefore, a systematic (Cochrane compliant) review was performed of venous system or coagulation parameters in actual spaceflight (microgravity) or ground-based analogues in PubMed, MEDLINE, Ovid EMBASE, Cochrane Library, European Space Agency, National Aeronautics and Space Administration, and Deutsches Zentrum für Luft-und Raumfahrt databases. Seven-hundred and eight articles were retrieved, of which 26 were included for evaluation with 21 evaluating venous, and five coagulation parameters. Nine articles contained spaceflight data, whereas the rest reported ground-based analogue data. There is substantial variability in study design, objectives and outcomes. Yet, data suggested cephalad venous system dilatation, increased venous pressures and decreased/reversed flow in microgravity. Increased fibrinogen levels, presence of thrombin generation markers and endothelial damage were also reported. Limited human venous and coagulation system data exist in spaceflight, or its analogues. Nevertheless, data suggest spaceflight may induce an enhanced coagulation state in the cephalad venous system, as a consequence of changes in venous flow, distension, pressures, endothelial damage and possibly hypercoagulability. Whether such changes precipitate an increased VTE risk in spaceflight remains to be determined.

MANAGEMENT OF DIABETES DURING AIR TRAVEL: A SYSTEMATIC LITERATURE REVIEW OF CURRENT RECOMMENDATIONS AND THEIR SUPPORTING EVIDENCE.

OBJECTIVE: Individuals with diabetes are increasingly seeking pretravel advice, but updated professional recommendations remain scant. We performed a systematic review on diabetes management during air travel to summarize current recommendations, assess supporting evidence, and identify areas of future research. METHODS: A systematic review of the English literature on diabetes management during air travel was undertaken utilizing PubMed and MEDLINE. Publications regarding general travel advice; adjustment of insulin and noninsulin therapies; and the use of insulin pumps, glucometers and subcutaneous glucose sensors at altitude were included. Gathered information was used to create an updated summary of glucose-lowering medication adjustment during air travel. RESULTS: Sixty-one publications were identified, most providing expert opinion and few offering primary data (47 expert opinion, 2 observational studies, 2 case reports, 10 device studies). General travel advice was uniform, with increasing attention to preflight security. Indications for oral antihyperglycemic therapy adjustments varied. There were few recommendations on contemporary agents and on nonhypoglycemic adverse events. There was little consensus on insulin adjustment protocols, many antedating current insulin formulations. Most publications advocated adjusting insulin pump time settings after arrival; however, there was disagreement on timing and rate adjustments. Glucometers and subcutaneous glucose sensors were reported to be less accurate at altitude, but not to an extent that would preclude their clinical use. CONCLUSION: Recommendations for diabetes management during air travel vary significantly and are mostly based on expert opinion. Data from systematic investigation on glucose-lowering medication adjustment protocols may support the development of a future consensus statement. ABBREVIATIONS: CSII = continuous subcutaneous insulin infusion (device) DPP-4 = dipeptidyl peptidase 4 EGA = error grid analysis GDH = glucose dehydrogenase GOX = glucose oxidase GLP1 = glucagon-like peptide-1 NPH = neutral protamine Hagedorn SGLT2 = sodium-glucose cotransporter-2.

Do not fear the Framingham: Practical application to properly evaluate and modify cardiovascular risk in commercial divers.

INTRODUCTION: In April 2016 the Association of Diving Contractors International (ADCI) consensus guidelines began recommending annual cardiovascular risk stratification of commercial divers using the Framingham Risk Score (FRS). For those at elevated risk, further testing is recommended. This approach has raised concerns about potential operational and financial impacts. However, the prevalence of elevated cardiovascular risk and need for additional testing among commercial divers is not known. METHODS: Clinical data required to calculate the FRS was abstracted for 190 commercial divers in two cohorts. Population demographics, FRS distribution, contributions of risk factors and effect of interventions on reducing risk-factor burden were assessed. RESULTS: Mean FRS score was 1.68 ± 6.35 points, with 13 divers (6.8%) at intermediate risk and none at high 10-year risk. In these 13 divers, the mean contributions to the FRS were from age (6.5 points), cholesterol (3.1 pts.), smoking (1.3 pts.), highdensity lipoprotein (1 pt.), and systolic blood pressure (0.8 pts). The youngest age group had a significantly higher modifiable risk core than the oldest age group (5.87 vs. 1.2 points, P ⟨ 0.001). All 13 intermediate risk divers could have been reclassified as low-risk with successful treatment of modifiable risk factors. DISCUSSION: The prevalence of elevated cardiovascular risk among commercial divers is low, and treatment of modifiable risk factors could reclassify those at intermediate risk to low risk. Therefore, FRS implementation coupled with intensive risk-reduction strategies for at risk-divers may help improve diver health and prolong the careers of divers while limiting the need for additional testing and adverse operational impact.

Grayscale median analysis of primary stenosis and restenosis after carotid endarterectomy.

BACKGROUND: Several studies have reported that echolucent carotid lesions, as determined by grayscale median (GSM) analysis, are associated with increased perioperative embolic complications during carotid artery stenting (CAS). However, there is limited research of the predictive value of GSM analysis comparing values for primary atherosclerotic lesions in the carotid artery with those for recurrent lesions after carotid endarterectomy (CEA). METHODS: Retrospective data were collected and analyzed from all patients undergoing CAS from November 2005 to August 2010. Available preoperative images amenable to GSM analysis were processed in Adobe Photoshop (version CS4; San Jose, Calif). Statistical analysis included t-test, Fischer exact test, and generation of a receiver operating characteristic curve. RESULTS: With at least 29 days of follow-up, 212 patients underwent 228 CAS procedures. There were 189 stents placed for primary lesions (CAS for primary stenosis group) and 39 stents placed for restenosis after CEA (CAS for restenosis group). GSM analysis was feasible for 47 patients, and the mean GSM was 45.6 (n = 34; 95% confidence interval, ± 8.3) for the primary stenosis group and 20.5 (n = 13; 95% confidence interval, ±9.6) for the restenosis group (P < .01). The mean time from CEA to CAS intervention for the restenosis group was 8.6 years. There was no statistical difference in procedural individual and combined complications of ipsilateral stroke, 30-day stroke, or 30-day mortality between the CAS for primary stenosis group and the CAS for restenosis group. In the primary stenosis group, the mean GSM was lower in those with procedural complications compared with those without complications (15 ± 22 vs 49 ± 8; P = .02). CONCLUSIONS: A low GSM value was associated with increased perioperative risk when CAS was performed for native carotid lesions, but a low GSM value was not associated with higher procedural risk when carotid stenting was performed for carotid stenosis after CEA (restenosis). GSM analysis for restenosis may be altered by the time interval from CEA to restenosis.

Outcomes comparison of HeRO and lower extremity arteriovenous grafts in patients with long-standing renal failure.

OBJECTIVE: The Hemodialysis Reliable Outflow (HeRO) graft is becoming a recognized alternative to lower extremity arteriovenous grafts (LEAVGs) as an option for patients who have exhausted traditional upper extremity access; however, which should be applied preferentially is unclear. METHODS: A retrospective review of LEAVG and HeRO implants from January 2004 to August 2010 was performed. Patient demographics, medical history, procedural data, and outcomes were evaluated. RESULTS: Within the time periods, 60 HeROs were placed in 59 patients and 22 LEAVGs were placed in 21 patients. Demographics were similar between the two groups for many factors; however, the patients who underwent HeRO placement had significantly higher body mass index compared with the LEAVG group. Mean follow-up was 13.9 months for the HeRO group and 11.9 months for the LEAVG group. The HeRO patients underwent a mean of 6.3 previous tunneled dialysis catheter insertions and 3.1 previous AVG/arteriovenous fistula placements. The LEAVG patients underwent placement of a mean of 4.1 previous tunneled dialysis catheters and 2.6 previous AVG/arteriovenous fistulas. The principal difference was the number of interventions to maintain patency, which was 2.21 per year in the HeRO group and 1.17 per year in the AVG group (P = .003) Secondary patency at 6 months was 77% for the HeRO patients and 83% for the LEAVG patients (P = .14). The HeRO and LEAVG groups had no difference in infection rate per 1000 days (0.61 vs 0.71; P = .77) or mortality rate (22% vs 19% respectively; P = .22) at 6 months. CONCLUSIONS: In access challenged patients, LEAVG and HeRO offer similar rates of secondary patency, infection, and all-cause mortality. The LEAVG required fewer interventions to maintain patency, and the HeRO maintains the benefit of utilizing the upper extremity site of venous drainage. In our practice, we prefer the HeRO to LEAVG, especially in patients with peripheral arterial disease and in the obese population, because it preserves lower extremity access options.