The Impact of Cannabinoids on Methemoglobin Formation and Hemoglobin Oxygen Affinity: An ex-vivo study.

The affinity of hemoglobin (Hb) to oxygen (O2) influences processes of oxygen delivery and extraction at the tissue level. Despite cannabinoids being utilized or ingested in various ways, their possible impact on Hb-O2 affinity has barely been studied. This is an experimental ex-vivo trial. Venous blood samples were drawn from 5 male and 6 female healthy volunteers and subsequently exposed to different cannabinoid types: (delta-9-tetrahydrocannabinol [Δ9-THC], delta-8-tetrahydrocannabinol [Δ8-THC], cannabidiol [CBD]) at different concentrations. Oxygen dissociation curves (ODC) were measured and blood gas analyses were performed for methemoglobin (MetHb) determination. The results revealed no MetHb formation. Besides two statistically significant changes (+1.4mmHg and -0.9mmHg) in the female cohort, following Δ9-THC and Δ8-THC exposure, no further P50 changes could be observed. The study demonstrated an in-vitro effect of selected cannabinoids and dosages on P50 values in female participants, with variations not observed at other dosages, leaving the underlying mechanisms open for debate. MetHb formation, as potential mechanism, was not detected in this study. The precise reasons why changes only occurred at specific dosages remain unclear, indicating a need for further in-vivo research to understand the interaction between cannabinoids and Hb-O2 affinity completely.

Sex Differences in Mountain Bike Accidents in Austria from 2006 to 2018: A Retrospective Analysis.

Woyke, Simon, Anja Hütter, Christopher Rugg, Willi Tröger, Bernd Wallner, Mathias Ströhle, and Peter Paal. Sex differences in mountain bike accidents in Austria from 2006 to 2018: a retrospective analysis. High Alt Med Biol. 25:89-93, 2024. Introduction: Mountain biking is becoming increasingly popular, and mountain bike (MTB) accidents are on the rise. The aim of this study was to assess sex differences in mountain biking accidents in the Austrian Alps. Methods: This retrospective study includes all MTB accidents in Austria from 2006 to 2018. Data were collected by Alpine Police officers and recorded in a national digital registry. Results: The accidents involved 5,095 mountain bikers (81% men and 19% women). The number of MTB accidents rose markedly from 208 in 2006 to 725 in 2018. Men wore a helmet more often than did women (95% vs. 92%; p = 0.001). The most common injury category was "wound/bleeding" for both sexes (men 40% and women 41%). Women were more frequently transported by helicopter or terrestrially (p > 0.001). Conclusion: In the Austrian Alps, the number of MTB accidents more than tripled between 2006 and 2018. Women were involved in only one fifth of all accidents. Sex differences in MTB accidents include (1) women wearing helmets less often, (2) women being less frequently injured, (3) women suffering fewer serious injuries, and (4) women being more frequently transported by helicopter or terrestrially, while men more often did not require transportation.

Shoulder reduction on the scene: current practice and outcome of the Bavarian Mountain Rescue Service-a prospective observational study.

Out-of-hospital reduction of shoulder dislocations using the Campell method is recommended by the International Commission for Alpine Rescue and applied in the Bavarian Mountain Rescue Service (Bergwacht Bayern, BWB) protocols. This prospective observational study includes patients out-of-hospital with suspected shoulder dislocation and treated and evacuated by the BWB. Data were systematically collected using three questionnaires: one completed on-site by the rescuer, the second in hospital by the physician and the third within 28 (8-143) days after the accident by the patient. The suspected diagnosis of shoulder dislocation was confirmed in hospital in 37 (84%) of 44 cases. Concomitant injuries in other body regions were found in eight (16%) of 49 cases and were associated with incorrect diagnosis (p = 0.002). Younger age (p = 0.043) and first shoulder dislocation event (p = 0.038) were associated with a higher success rate for reduction attempts. Out-of-hospital reduction of shoulder dislocations leads to significant pain relief and no poorer long-term outcome. Signs that are associated with successful out-of-hospital reduction (younger age and first event), but also those that are associated with incorrect diagnosis (concomitant injuries) should be considered before trying to reduce shoulder dislocation on site. The considerable rate of incorrect first diagnosis on site should give rise to an intensive discussion around teaching and training for this intervention.Trial registration: This study is registered with the German Registry for Clinical Trials (DRKS00023377).

Catabolism highly influences ICU-acquired hypernatremia in a mainly trauma and surgical cohort.

PURPOSE: To further analyse causes and effects of ICU-acquired hypernatremia. METHODS: This retrospective, single-centre study, analysed 994 patients regarding ICU-acquired hypernatremia. Non-hypernatremic patients (n = 617) were compared to early-hypernatremic (only before ICU-day 4; n = 87), prolonged-hypernatremic (before and after ICU-day 4; n = 169) and late-hypernatremic patients (only after ICU-day 4; n = 121). Trends in glomerular filtration rate (eGFR), urea-to-creatinine ratio (UCR), fraction of urea in total urine osmolality and urine sodium were compared. Risk factors for i) the development of hypernatremia and ii) mortality were determined. RESULTS: Thirty-eight percent (n = 377) developed ICU-acquired hypernatremia. Specifically in the prolonged- and late-group, decreased eGFRs and urine sodium but increased UCR and fractions of urea in urine osmolality were present. Decreased eGFR was a risk factor for the development of hypernatremia in all groups; disease severity and increased catabolism particularly in the prolonged- and late-hypernatremic group. Increased age, SAPS-III and signs of catabolism but not the development of hypernatremia itself was identified as significant risk factor for mortality. CONCLUSIONS: Late- and prolonged-hypernatremia is highly related to an increased protein metabolism. Besides excessive catabolism, initial disease severity and a decrease in renal function must be considered when confronted with ICU-acquired hypernatremia.

Evaluation of the New SingularityTM Air versus Ambu® Aura GainTM: A Randomized, Crossover Mannequin Study.

Background: This randomised crossover mannequin study aimed to compare the insertion time for the newly developed SingularityTM Air and the Ambu® AuraGainTM. The SingularityTM Air includes a bendable tube in order to allow optimal passform. Methods: Fifty anaesthetists with a minimum of 100 supraglottic airway device insertions were recruited and randomly assigned to start either with the SingularityTM Air or with the Ambu® AuraGainTM. Participants watched a tutorial video the day before the assessment and received a standardized introduction immediately before the assessment. The primary outcome was the time for successful insertion. Secondary parameters were the overall insertion success rate, the numbers of insertion attempts (maximum three), the glottic view through a flexible bronchoscope, and the success rate for gastric tube insertion. Results: Fifty participants were eventually recruited and randomly assigned to insert both devices according to the randomization. The insertion time was 24 s for SingularityTM Air as compared to 20 s for Ambu® AuraGainTM (p < 0.001). Overall insertion rate was 92% for the SingularityTM Air as compared to 100% for the Ambu® AuraGainTM (p could not be derived as one variable is a constant). The primary insertion success rate was better for the Ambu® AuraGainTM than for the SingularityTM Air (94% versus 68%; p: 0.002, respectively). Conclusion: The time for successful insertion and the insertion success rate for the newly developed SingularityTM Air is inferior to that for the Ambu® AuraGainTM.

The effect of desflurane, isoflurane and sevoflurane on the hemoglobin oxygen dissociation curve in human blood samples.

Desflurane, isoflurane and sevoflurane, three halogenated ethers, are commonly used inhaled anesthetics, both in the operating room and in the intensive care unit (ICU). The potency and dosage of these drugs is expressed by the MAC value (minimum alveolar concentration). Their interaction with hemoglobin and its affinity for oxygen, best described by the oxygen dissociation curve (ODC), has already been investigated, with conflicting results. Altered by many factors, the ODC can be shifted to the left or to the right, therefore increasing or decreasing hemoglobin oxygen (Hb-O2) affinity. In venous blood samples of 22 healthy participants (11 female, 11 male) ODC were measured with a high-throughput method in vitro. Blood samples were either exposed to control or to three different concentrations of desflurane, isoflurane or sevoflurane prior to and during measurements (low, medium and high corresponding to MAC 0.5, MAC 1.0 and MAC 2.0). With increasing concentrations from control to medium, desflurane and isoflurane significantly decreased Hb-O2 affinity by shifting the ODC to the right (p = 0.016 and p < 0.001) but sevoflurane showed no effects. When further increasing concentrations from medium to high, all three inhaled anesthetics shifted the ODC back to the left (p < 0.001). Comparing only controls to high concentrations, a significant increase in Hb-O2 affinity for desflurane (p = 0.005) and sevoflurane (p < 0.001) was detected. Our study shows a varying effect at different doses of inhaled anesthetics on Hb-O2 affinity. While the underlying mechanisms remain unclear, these results show an effect which needs to be further investigated to determine if patients undergoing anesthesia may potentially benefit or get disadvantage from this slightly increased (e.g. impaired pulmonary oxygen uptake), or decreased Hb-O2 affinity (e.g. arterial vascular disease).Trial registration: This study is registered with clinicaltrials.gov (NCT04612270).

The impact of nebulized epoprostenol and iloprost on hemoglobin oxygen affinity: an ex vivo experiment.

Inhalational prostacyclins act as strong vasodilators, potentially improving oxygenation by reducing shunt fraction and ventilation-perfusion mismatch. As prostacyclin receptors are known to be present on human erythrocytes, possible direct effects on hemoglobin oxygen transport were further explored by examining the sole in vitro influence of prostacyclins on hemoglobin oxygen (Hb-O2) affinity. Venous blood samples from 20 healthy volunteers were exposed in vitro to supramaximal doses of epoprostenol, iloprost, and compared with control. By high-throughput measurements, hemoglobin oxygen dissociation curves (ODCs) were derived. Hb-O2 affinity, expressed by P50 and Hill coefficient, was determined and analyzed for three subgroups: males (n = 10), females not taking oral contraceptives (n = 4), and females taking oral contraceptives (n = 6). Epoprostenol significantly decreased P50 in all (males, females without contraceptives, and females taking oral contraceptives) [27.5 (26.4-28.6) mmHg (control) vs. 24.2 (22.7-25.3) mmHg; P < 0.001. median (interquartile range, IQR)] thereby increasing Hb-O2 affinity. Inversely, iloprost only showed significant effects in females taking oral contraceptives where P50 was markedly increased and therefore Hb-O2 affinity decreased [28.4 (27.9-28.9) mmHg (control) vs. 34.4 (32.2-36.0) mmHg; P < 0.001]. Prostacyclin-receptor stimulation and subsequent cAMP-mediated ATP release from erythrocytes are discussed as a possible underlying mechanism for the effect of epoprostenol on Hb-O2 affinity. The reason for the sex hormone-modified iloprost effect remains unclear. Being aware of potentially differing effects on Hb-O2 affinity might help select the right prostacyclin (epoprostenol vs. iloprost) depending on the patient and the underlying disease (e.g., acute respiratory distress syndrome vs. peripheral arterial disease).

Analgesia in pediatric trauma patients in physician-staffed Austrian helicopter rescue: a 12-year registry analysis.

BACKGROUND: As pediatric patients are typically rare among helicopter emergency medical systems (HEMS), children might be at risk for oligo-analgesia due to the rescuer's lack of experience and the fear of side effects. METHODS: In this retrospective analysis, data was obtained from the ÖAMTC HEMS digital database including 14 physician staffed helicopter bases in Austria over a 12-year timeframe. Primary missions involving pediatric trauma patients (< 15 years) not mechanically ventilated on-site were included. Analgesia was assessed and compared between the age groups 0-5, 6-10 and 11-14 years. RESULTS: Of all flight missions, 8.2% were dedicated to children < 15 years. Analgetic drugs were administered in 31.4% of all primary missions (3874 of 12,324), wherefrom 2885 were injured and non-ventilated (0-5 yrs.: n = 443; 6-10 yrs.: n = 902; 11-14 yrs.: n = 1540). The majority of these patients (> 75%) suffered moderate to severe pain, justifying immediate analgesia. HEMS physicians typically chose a monotherapy with an opioid (n = 1277; 44.3%) or Esketamine (n = 1187; 41.1%) followed by the combination of both (n = 324; 11.2%). Opioid use increased (37.2% to 63.4%) and Esketamine use decreased (66.1% to 48.3%) in children < 6 vs. > 10 years. Esketamine was more often administered in extremity (57.3%) than in head (41.5%) or spine injuries (32.3%). An intravenous access was less often established in children < 6 years (74.3% vs. 90.8%; p < 0.001). Despite the use of potent analgesics, 396 missions (13.7%) were performed without technical monitoring. Particularly regarding patient data at handover in hospital, merely < 10% of all missions featured complete documentation. Therefore, sufficient evaluation of the efficacy of pain relief was not possible. Yet, by means of respiratory measures required during transport, severe side effects such as respiratory insufficiency, were barely noted. CONCLUSIONS: In the physician-staffed HEMS setting, pediatric trauma patients liberally receive opioids and Esketamine for analgesia. With regard to severe respiratory insufficiency during transport, the application of these potent analgesics seems safe.

Dose- and Sex-Dependent Changes in Hemoglobin Oxygen Affinity by the Micronutrient 5-Hydroxymethylfurfural and α-Ketoglutaric Acid.

5-Hydroxymethylfurfural (5-HMF) is known to increase hemoglobin oxygen affinity (Hb-O2 affinity) and to induce a left shift of the oxygen dissociation curve (ODC). It is under investigation as a therapeutic agent in sickle cell anemia and in conditions where pulmonary oxygen uptake is deteriorated or limited (e.g., various clinical conditions or altitude exposure). The combination of 5-HMF and α-ketoglutaric acid (αKG) is commercially available as a nutritional supplement. To further elucidate dose effects, ODCs were measured in vitro in venous whole blood samples of 20 healthy volunteers (10 female and 10 male) after the addition of three different doses of 5-HMF, αKG and the combination of both. Linear regression analysis revealed a strong dose-dependent increase in Hb-O2 affinity for 5-HMF (R2 = 0.887; p < 0.001) and the commercially available combination with αKG (R2 = 0.882; p < 0.001). αKG alone increased Hb-O2 affinity as well but to a lower extent. Both the combination (5-HMF + αKG) and 5-HMF alone exerted different P50 and Hill coefficient responses overall and between sexes, with more pronounced effects in females. With increasing Hb-O2 affinity, the sigmoidal shape of the ODC was better preserved by the combination of 5-HMF and αKG than by 5-HMF alone. Concerning the therapeutic effects of 5-HMF, this study emphasizes the importance of adequate dosing in various physiological and clinical conditions, where a left-shifted ODC might be beneficial. By preserving the sigmoidal shape of the ODC, the combination of 5-HMF and αKG at low (both sexes) and medium (males only) doses might be able to better maintain efficient oxygen transport, particularly by mitigating potentially deteriorated oxygen unloading in the tissue. However, expanding knowledge on the interaction between 5-HMF and Hb-O2 affinity in vitro necessitates further investigations in vivo to additionally assess pharmacokinetic mechanisms.

High-throughput determination of oxygen dissociation curves in a microplate reader-A novel, quantitative approach.

In vitro determination of the hemoglobin oxygen dissociation curve (ODC) requires highly elaborate, specialized, and costly technical equipment. In addition, there is a lack of methods that combine reliable ODC recordings with high throughput in small blood samples for routine analysis. We here introduce a modified, commercial 96-well plate with an integrated unidirectional gas flow system specifically adapted for use in fluorescence microplate readers. Up to 92 samples of whole or hemolyzed, buffered or unbuffered blood, including appropriate controls or internal standard hemoglobin solutions, can be analyzed within ~25 min. Oxygen saturation is measured in each well with dual wavelength spectroscopy, and oxygen partial pressure using fluorescence lifetime of commercial oxygen sensors at the in- and outlet ports of the gas-flow system. Precision and accuracy of this method have been determined and were compared with those of a standard method. We further present two applications that exemplarily highlight the usefulness and impact of this novel approach for clinical diagnostics or basic research.

Bioelectrical Impedance Vector Analysis: A Valuable Tool to Monitor Daily Body Hydration Dynamics at Altitude.

Bioelectrical impedance vector analysis (BIVA) is a method used to estimate variation in body hydration. We assessed the potential of BIVA for monitoring daily body hydration fluctuations in nine healthy, normally active males under matching normoxic (NX) and hypobaric hypoxic (HH) experimental conditions. Furthermore, we aimed to investigate whether changes in BIVA may correspond with the development of acute mountain sickness (AMS). Subjects were exposed in a hypobaric chamber to both NX (corresponding to an altitude of 262 m) and HH conditions corresponding to an altitude of 3500 m during two four-day sojourns within which food, water intake and physical activity were controlled. Bioimpedance and body weight measurements were performed three times a day and medical symptoms were assessed every morning using the Lake Louise score (LLS). Total body water (TBW) was also assessed on the last day of both sojourns using the deuterium dilution technique. We detected circadian changes in vector length, indicating circadian body water variations that did not differ between NX and HH conditions (ANOVA effects: time: p = 0.018, eta2 = 0.149; interaction: p = 0.214, eta2 = 0.083; condition: p = 0.920, eta2 = 0.001). Even though none of the subjects developed AMS, four subjects showed clinical symptoms according to the LLS during the first 24 hours of HH conditions. These subjects showed a pronounced (Cohen's d: 1.09), yet not statistically significant (p = 0.206) decrease in phase angle 6 hours after exposure, which may indicate fluid shift from the intracellular to the extracellular compartment. At the end of each sojourn, vector length correlated with deuterium dilution TBW "gold standard" measurements (linear regression: NX: p = 0.002 and r2 = 0.756, HH: p < 0.001 and r2 = 0.84). BIVA can be considered a valuable method for monitoring body hydration changes at altitude. Whether such changes are related to the development of clinical symptoms associated with AMS, as indicated in the present investigation, must be confirmed in future studies.

Plasma volume contraction reduces atrial natriuretic peptide after four days of hypobaric hypoxia exposure.

We investigated whether low arterial oxygen tension ([Formula: see text]) or hypoxia-induced plasma volume (PV) contraction, which reduces central blood volume (BV) and atrial distension, explain reduction in circulating atrial natriuretic peptide (ANP) after prolonged hypoxic exposure. Ten healthy males were exposed for 4 days to hypobaric hypoxia corresponding to an altitude of 3,500 m. PV changes were determined by carbon monoxide rebreathing. Venous plasma concentrations of midregional proANP (MR-proANP) were measured before and at the end of the exposure. At the latter time point, the measurement was repeated after 1) restoration of [Formula: see text] by breathing a hyperoxic gas mixture for 30 min and 2) restoration of BV by fluid infusion. Correspondingly, left ventricular end-diastolic volume (LVEDV), left atrial area (LAA), and right atrial area (RAA) were determined by ultrasound before exposure and both before and after fluid infusion at the end of the exposure. Hypoxic exposure reduced MR-proANP from 37.9 ± 18.5 to 24.5 ± 10.3 pmol/L (P = 0.034), LVEDV from 107.4 ± 33.5 to 91.6 ± 26.3 mL (P = 0.005), LAA from 15.8 ± 4.9 to 13.3 ± 4.2 cm2 (P = 0.007), and RAA from 16.2 ± 3.1 to 14.3 ± 3.5 cm2 (P = 0.001). Hyperoxic breathing did not affect MR-proANP (24.8 ± 12.3 pmol/L, P = 0.890). Conversely, fluid infusion restored LVEDV, LAA, and RAA to near-baseline values (108.0 ± 29.3 mL, 17.2 ± 5.7 cm2, and 17.2 ± 3.1 cm2, respectively, P > 0.05 vs. baseline) and increased MR-proANP to 29.5 ± 13.3 pmol/L (P = 0.010 vs. preinfusion and P = 0.182 vs. baseline). These findings support that ANP reduction in hypoxia is at least partially attributed to plasma volume contraction, whereas reduced [Formula: see text] does not seem to contribute.

Analgesia in adult trauma patients in physician-staffed Austrian helicopter rescue: a 12-year registry analysis.

BACKGROUND: Sufficient analgesia is an obligation, but oligoanalgesia (NRS> 3) is frequently observed prehospitally. Potent analgesics may cause severe adverse events. Thus, analgesia in the helicopter emergency medical service (HEMS) setting is challenging. Adequacy, efficacy and administration safety of potent analgesics pertaining to injured patients in HEMS were analysed. METHODS: Observational study evaluating data from 14 year-round physician-staffed helicopter bases in Austria in a 12-year timeframe. RESULTS: Overall, 47,985 (34.3%) patients received analgesics, 26,059 of whom were adult patients, injured and not mechanically ventilated on site. Main drugs administered were opioids (n=20,051; 76.9%), esketamine (n=9082; 34.9%), metamizole (n=798; 3.1%) and NSAIDs (n=483; 1.9%). Monotherapy with opioids or esketamine was the most common regimen (n=21,743; 83.4%), while opioids together with esketamine (n= 3591; 13.8%) or metamizole (n=369; 1.4%) were the most common combinations. Females received opioids less frequently than did males (n=6038; 74.5% vs. n=14,013; 78.1%; p< 0.001). Pain relief was often sufficient (> 95%), but females more often had moderate to severe pain on arrival in hospital (n=34; 5.0% vs. n=59; 3.2%; p=0.043). Administration of potent analgesics was safe, as indicated by MEES, SpO2 and respiratory rates. On 10% of all missions, clinical patient assessment was deemed sufficient by HEMS physicians and monitoring was spared. CONCLUSIONS: Opioids and esketamine alone or in combination were the analgesics of choice in physician-staffed HEMS in Austria. Analgesia was often sufficient, but females more than males suffered from oligoanalgesia on hospital arrival. Administration safety was high, justifying liberal use of potent analgesics in physician-staffed HEMS.

Effects of Carbon Dioxide and Temperature on the Oxygen-Hemoglobin Dissociation Curve of Human Blood: Implications for Avalanche Victims.

Completely avalanche-buried patients are frequently exposed to a combination of hypoxia and hypercapnia with a risk of normothermic cardiac arrest. Patients with a long burial time and an air pocket are exposed to a combination of hypoxia, hypercapnia, and hypothermia which may lead to the development of the "triple H syndrome". This specific combination has several pathophysiological implications, particularly on the cardiovascular system and oxygen transport (oxygen supply and oxygen consumption). To examine the effects on hemoglobin oxygen affinity, we investigated venous blood samples from 15 female and 15 male healthy subjects. In a factorial design of four different carbon dioxide partial pressure (PCO2) levels (20, 40, 60, and 80 mmHg) and five different temperature levels (13.7°C, 23°C, 30°C, 37°C, and 42°C), 30 unbuffered whole blood samples were analyzed in a newly developed in vitro method for high-throughput oxygen dissociation curve (ODC) measurements. P50s, Hill coefficients, CO2-Bohr coefficients, and temperature coefficients were analyzed using a linear mixed model (LMM). Mean P50 at baseline (37°C, 40 mmHg PCO2) was 27.1 ± 2.6 mmHg. Both CO2-Bohr (p < 0.001) and temperature coefficients (p < 0.001) had a significant effect on P50. The absolute CO2 effect was still pronounced at normothermic and febrile temperatures, whereas at low temperatures, the relative CO2 effect (expressed by CO2-Bohr coefficient; p < 0.001, interaction) was increased. The larger impact of PCO2 on oxygen affinity at low temperature may be caused by the competition of 2,3-BPG with PCO2 and the exothermic binding characteristic of 2,3-BPG. In a model of an avalanche burial, based on published data of CO2 levels and cooling rates, we calculated the resulting P50 for this specific condition based on the here-reported PCO2 and temperature effect on ODC. Depending on the degree of hypercapnia and hypothermia, a potentially beneficial increase in hemoglobin oxygen affinity in the hypoxic condition might ensue.

Modulation of Hb-O2 affinity to improve hypoxemia in COVID-19 patients.

This opinion paper aims at discussing the potential impact of modulating the Hb-O2 affinity by the nutritional supplement 5-HMF on patients affected by COVID-19. The paper describes the critical role of the oxygen affinity in hypoxemic COVID-19 patients and the potential positive effect of 5-HMF, a compound shown to increase the Hb-O2 affinity.

Regulation of plasma volume in male lowlanders during 4 days of exposure to hypobaric hypoxia equivalent to 3500 m altitude.

KEY POINTS: Acclimatization to hypoxia leads to a reduction in plasma volume (PV) that restores arterial O2 content. Findings from studies investigating the mechanisms underlying this PV contraction have been controversial, possibly as experimental conditions were inadequately controlled. We examined the mechanisms underlying the PV contraction evoked by 4 days of exposure to hypobaric hypoxia (HH) in 11 healthy lowlanders, while strictly controlling water intake, diet, temperature and physical activity. Exposure to HH-induced an ∼10% PV contraction that was accompanied by a reduction in total circulating protein mass, whereas diuretic fluid loss and total body water remained unchanged. Our data support an oncotically driven fluid redistribution from the intra- to the extravascular space, rather than fluid loss, as the mechanism underlying HH-induced PV contraction. ABSTRACT: Extended hypoxic exposure reduces plasma volume (PV). The mechanisms underlying this effect are controversial, possibly as previous studies have been confounded by inconsistent experimental conditions. Here, we investigated the effect of hypobaric hypoxia (HH) on PV in a cross-over study that strictly controlled for diet, water intake, physical activity and temperature. Eleven males completed two 4-day sojourns in a hypobaric chamber, one in normoxia (NX) and one in HH equivalent to 3500 m altitude. PV, urine output, volume-regulating hormones and plasma protein concentration were determined daily. Total body water (TBW) was determined at the end of both sojourns by deuterium dilution. Although PV was 8.1 ± 5.8% lower in HH than in NX after 24 h and remained ∼10% lower thereafter (all P < 0.002), no differences were detected in TBW (P = 0.17) or in 24 h urine volumes (all P > 0.23). Plasma renin activity and circulating aldosterone were suppressed in HH during the first half of the sojourn (all P < 0.05) but thereafter similar to NX, whereas no differences were detected for copeptin between sojourns (all P > 0.05). Markers for atrial natriuretic peptide were higher in HH than NX after 30 min (P = 0.001) but lower during the last 2 days (P < 0.001). While plasma protein concentration was similar between sojourns, total circulating protein mass (TCP) was reduced in HH at the same time points as PV (all P < 0.03). Despite transient hormonal changes favouring increased diuresis, HH did not enhance urine output. Instead, the maintained TBW and reduced TCP support an oncotically driven fluid redistribution into the extravascular compartment as the mechanism underlying PV contraction.

Endothelial function and shear stress in hypobaric hypoxia: time course and impact of plasma volume expansion in men.

High-altitude exposure typically reduces endothelial function, and this is modulated by hemoconcentration resulting from plasma volume contraction. However, the specific impact of hypobaric hypoxia independent of external factors (e.g., cold, varying altitudes, exercise, diet, and dehydration) on endothelial function is unknown. We examined the temporal changes in blood viscosity, shear stress, and endothelial function and the impact of plasma volume expansion (PVX) during exposure to hypobaric hypoxia while controlling for external factors. Eleven healthy men (25 ± 4 yr, mean ± SD) completed two 4-day chamber visits [normoxia (NX) and hypobaric hypoxia (HH; equivalent altitude, 3,500 m)] in a crossover design. Endothelial function was assessed via flow-mediated dilation in response to transient (reactive hyperemia; RH-FMD) and sustained (progressive handgrip exercise; SS-FMD) increases in shear stress before entering and after 1, 6, 12, 48, and 96 h in the chamber. During HH, endothelial function was also measured on the last day after PVX to preexposure levels (1,140 ± 320 mL balanced crystalloid solution). Blood viscosity and arterial shear stress increased on the first day during HH compared with NX and remained elevated at 48 and 96 h (P < 0.005). RH-FMD did not differ during HH compared with NX and was unaffected by PVX despite reductions in blood viscosity (P < 0.05). The stimulus-response slope of increases in shear stress to vasodilation during SS-FMD was preserved in HH and increased by 44 ± 73% following PVX (P = 0.023). These findings suggest that endothelial function is maintained in HH when other stressors are absent and that PVX improves endothelial function in a shear-stress stimulus-specific manner.NEW & NOTEWORTHY Using a normoxic crossover study design, we examined the impact of hypobaric hypoxia (4 days; altitude equivalent, 3,500 m) and hemoconcentration on blood viscosity, shear stress, and endothelial function. Blood viscosity increased during the hypoxic exposure and was accompanied by elevated resting and exercising arterial shear stress. Flow-mediated dilation stimulated by reactive hyperemia and handgrip exercise was preserved throughout the hypoxic exposure. Plasma volume expansion reversed the hypoxia-associated hemoconcentration and selectively increased handgrip exercise flow-mediated dilation.

Aviation Sports Crashes in the Austrian Mountains: A 10-Year Retrospective Study.

INTRODUCTION: We aimed to describe the epidemiology and injury patterns of aviation sports crashes in the Austrian mountains and identify risk factors. METHODS: In this retrospective cohort study, out-of-hospital data on patients who sustained crashes when participating in aviation sports from January 1, 2006 through December 31, 2015 were assessed. The out-of-hospital data were merged with in-hospital data obtained from Innsbruck Medical University Hospital. RESULTS: A total of 2037 persons were involved in 1856 aviation sports crashes. Data on 126 in-hospital patients were available. Wind and pilot error were the most common causes. Most injuries occurred in paragliders (n=111, 88%). Most commonly, paragliders sustained injuries to the lumbar spine and hang gliders to the thoracic spine. Rescue operations were undertaken mainly by helicopter emergency medical services (n=87, 69%) or combined rescue forces (ground and helicopter, n=100, 79%.). The Injury Severity Score was 15±15, with a peak in patients with isolated injuries of the lower extremities (n=38, 32%) and a second peak in patients with multiple trauma (n=44, 35%). CONCLUSIONS: In the Austrian mountains, wind and pilot errors are the most common causes of aviation crashes. Aviation sports crashes frequently resulted in severe injuries and multiple trauma. The lumbar spine is particularly at risk in paragliders, whereas the thoracic spine is commonly affected in hang gliders. Injuries frequently caused long-term paralysis and limitations in quality of life. To minimize long-term consequences and save lives, skilled and well-equipped teams may be beneficial to provide effective on-site care and safe transportation to a trauma center.

Canyoning Accidents in Austria from 2005 to 2018.

Canyoning has become a popular recreational sport. Nevertheless, little is known about injuries or diseases associated with canyoning. The aim of this study was to examine accident causes, injury patterns, out-of-hospital and in-hospital treatment and outcomes. For this purpose, national out-of-hospital data from the Austrian Alpine Safety Board and regional in-hospital data from Innsbruck Medical University Hospital were analysed for the period from November 1, 2005 to October 31, 2018. Nationally, 471 persons were involved in such accidents; 162 (34.4%) were severely injured, nine of whom died. Jumping (n = 110, 23.4%), rappelling (n = 51, 10.8%), sliding (n = 41, 8.7%) and stumbling (n = 26, 5.5%) were the most common causes of canyoning accidents. A large proportion of injuries were documented for the lower extremities (n = 133, 47.5%), followed by the upper extremities (n = 65, 23.2%) and the spine (n = 44, 15.7%). Death was mainly caused by drowning. Overall mortality was 1.9% (n = 9), and the absolute risk was 0.02 deaths per 1000 hrs of canyoning. Many uninjured persons required evacuation (n = 116, 24.6%), which resulted in a substantial expense and workload for emergency medical services. Increased safety precautions are required to reduce accidents while jumping and rappelling and fatalities caused by drowning.