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Background Geoeconomic variations in epidemiology, the practice of ventilation, and outcome in invasively ventilated intensive care unit (ICU) patients without acute respiratory distress syndrome (ARDS) remain unexplored. In this analysis we aim to address these gaps using individual patient data of four large observational studies. MethodsIn this pooled analysis we harmonised individual patient data from the ERICC, LUNG SAFE, PRoVENT, and PRoVENT-iMiC prospective observational studies, which were conducted from June, 2011, to December, 2018, in 534 ICUs in 54 countries. We used the 2016 World Bank classification to define two geoeconomic regions: middleincome countries (MICs) and high-income countries (HICs). ARDS was defined according to the Berlin criteria. Descriptive statistics were used to compare patients in MICs versus HICs. The primary outcome was the use of low tidal volume ventilation (LTVV) for the first 3 days of mechanical ventilation. Secondary outcomes were key ventilation parameters (tidal volume size, positive end-expiratory pressure, fraction of inspired oxygen, peak pressure, plateau pressure, driving pressure, and respiratory rate), patient characteristics, the risk for and actual development of acute respiratory distress syndrome after the first day of ventilation, duration of ventilation, ICU length of stay, and ICU mortality. Findings Of the 7608 patients included in the original studies, this analysis included 3852 patients without ARDS, of whom 2345 were from MICs and 1507 were from HICs. Patients in MICs were younger, shorter and with a slightly lower body-mass index, more often had diabetes and active cancer, but less often chronic obstructive pulmonary disease and heart failure than patients from HICs. Sequential organ failure assessment scores were similar in MICs and HICs. Use of LTVV in MICs and HICs was comparable (42•4% vs 44•2%; absolute difference -1•69 [-9•58 to 6•11] p=0•67; data available in 3174 [82%] of 3852 patients). The median applied positive end expiratory pressure was lower in MICs than in HICs (5 [IQR 5-8] vs 6 [5-8] cm H 2 O; p=0•0011). ICU mortality was higher in MICs than in HICs (30•5% vs 19•9%; p=0•0004; adjusted effect 16•41% [95% CI 9•52-23•52]; p<0•0001) and was inversely associated with gross domestic product (adjusted odds ratio for a US$10 000 increase per capita 0•80 [95% CI 0•75-0•86]; p<0•0001).Interpretation Despite similar disease severity and ventilation management, ICU mortality in patients without ARDS is higher in MICs than in HICs, with a strong association with country-level economic status.

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47ÖZ Bu derleme magnezyumun pek çok kullanım alanına ek olarak kritik hastada enflamasyon sürecine etkisi, immün sisteme olan katkısını göstermeyi amaçlamıştır. Magnezyum insan vücudunda ekstrasellüler alanda dördüncü sırada, intrasellüler olarak da ikinci olarak en sık bulunan katyonu olup; nükleik asit ve protein sentezi gibi birçok temel reaksiyonda enzim kofaktörü olarak rol alması, hücre membran stabilizasyonunu sağlaması gibi görevleri göz önüne alındığında son derece önemli bir elementtir. Diğer pek çok elektrolite kıyasla en önemli özelliği immün sisteme ve canlı immünitesine olan etkisidir. Yoğun bakımda yatan immünosüpresif ya da immünokompetan olan her grup hastada magnezyum eksikliği desteklenmeli ve pek çok yararına ek olarak magnezyumun immmün sisteme katkısı akılda tutulmalıdır. Anahtar Kelimeler: Magnezyum, immünite, inflamasyon ABSTRACT This review aims to demonstrate the relation between magnesium and the immune system and their effect on inflammatory process in the critical patient, in addition to many other clinical uses of magnesium. Magnesium is the fourth most commonly found cation in the extracellular space in the human body and the second most common cation in the cell. Magnesium is an extremely important element when considering its role as an enzyme cofactor in many basic reactions, such as nucleic acid, protein synthesis and cell membrane stabilization. The most important features compared to other electrolytes is its effect on the immune system and living immunity. For each group of immunosuppressive or immunocompenent patients in intensive care unit, magnesium deficiency should be supported and in addition to other clinical benefits, the contribution of magnesium to the immune system should be kept in mind.

The aim of the current study was to evaluate the relationship of intrapulmonary shunt with FiO 2 alterations in patients treated with mechanical ventilation in intensive care unit for extrapulmonary disorders. Also, we aimed to assess the role of correlation between shunt ratio and PaO 2 /FiO 2 , PaO 2 /PAO 2 , P(A-a) O 2 values in determining the treatment strategies. Methods: Twenty patients between ages of 19 and 75 years, requiring mechanical ventilation were enrolled into the study. We excluded two patients due to congestive heart failure and two patients due to acute respiratory distress syndrome (ARDS). Shunt fraction, P(A-a)O 2 , PaO 2 /FiO 2 , PaO 2 /PAO 2 values were calculated at each FiO 2 level for each patient. Results: The lowest median shunt value was measured at FiO 2 : 0.3 There was a significant correlation between shunt values at FiO 2 0.5 and 0.7 (r=0.850). The highest mean value of P(A-a)O 2 was measured at FiO 2 : 1 (382.91±106.46), and the lowest value of P(A-a)O 2 was measured at FiO 2 : 0.21 (38.64±16.97). PaO 2 /FiO 2 and PaO 2 /PAO 2 ratios measured at FiO 2 : 0.3 and 0.5 were found to be statistically significant. Conclusion: In this study, we have shown increased shunt fraction at FiO 2 : 1 level. Different oxygenation indices and shunt measurements give us important and useful knowledge about the patients' current condition.