Acute and Critical Care

Review Article

Pulmonary
Optimal oxygenation in the intensive care unit: what recent trials do—and do not—tell us: Masaji Nishimura; Acute Crit Care. 2026;41(3):480-492. Published online May 13, 2026; DOI: https://doi.org/10.4266/acc.000312

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Abstract PDF: Oxygen therapy is one of the most widely used interventions in critical care. Numerous observational studies and randomized controlled trials (RCTs) have evaluated conservative versus liberal oxygenation strategies, yet their results remain inconsistent, a pattern commonly observed in large clinical trials across multiple fields. Recent advances in intensive care unit practices further complicate the interpretation of prior findings, highlighting the need for a clearer framework to interpret oxygenation targets. This narrative review summarizes major observational studies, RCTs, and meta-analyses evaluating oxygenation strategies in critically ill patients. We examine variation in study designs, target and achieved oxygenation levels, and evolving critical care practices. Physiological principles, including oxygen delivery, oxygen utilization, and the oxyhemoglobin dissociation curve, are applied to interpret current evidence and define clinically meaningful safety margins, while acknowledging the limitations of interpreting heterogeneous trial and meta-analytic results. Recent RCTs have found relatively small differences in oxygenation between study groups; both conservative and liberal oxygenation targets are generally within a safe physiological range. However, evidence from the LOCO2 trial indicates excessively low targets may be harmful, suggesting a safer lower limit of approximately peripheral oxygen saturation (SpO2) 92%–93%. Retrospective studies indicate acceptable outcomes with arterial oxygen partial pressure (PaO2) values up to approximately 120 mm Hg. Because the upper portion of the oxyhemoglobin dissociation curve is flat, SpO2 cannot reliably detect hyperoxemia. Rather than determining the superiority of conservative or liberal oxygenation strategies, current evidence supports defining a practical therapeutic window. For most critically ill patients, an SpO2 range of 92–97% likely represents a safe and clinically meaningful target.

Original Article

Infection
Prognostic value of novel indices combining Shock Index, Reverse Shock Index, age, and oxygen saturation for predicting mortality in COVID-19 patients in Iran at emergency department triage: a cross-sectional study: Mehdi Torabi, Atefe Noroozpour, Neda Naeemi Bafghi, Moghaddameh Mirzaee; Acute Crit Care. 2025;40(3):425-434. Published online August 29, 2025; DOI: https://doi.org/10.4266/acc.005040

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Background
The objective of the study was to investigate the role of the Shock Index (SI), the Reverse Shock Index (RSI) along with oxygen saturation in predicting mortality in coronavirus disease 2019 (COVID-19).
Methods
This cross-sectional study was conducted at an academic hospital over a period of 6 months and involved patients over the age of 18 who had been diagnosed with COVID-19 via positive polymerase chain reaction tests. The data were recorded anonymously using a checklist. The study focused on indices such as the SI and RSI, both alone and in conjunction with age and oxygen saturation, to predict hospital mortality. Statistical analysis was conducted using SPSS software.
Results
The study involved 500 COVID-19 patients with a 14.4% mortality rate. Key differences were found between survival and mortality groups in terms of age, vital signs except diastolic blood pressure, length of stay, and a series of laboratory tests. Logistic regression showed gender, oxygen saturation, hemoglobin, direct bilirubin, lactate dehydrogenase, D-dimer, and Age SI/oxygen saturation (SpO2) and RSI×SpO2/Age indices significantly associated with hospital mortality. Receiver operating characteristic analysis indicated Age SI/SpO2 and RSI×SpO2/Age as effective mortality predictors, exhibiting an area under the curve of 0.80 and achieving a sensitivity, specificity, and accuracy of over 70%.
Conclusions
The combination of SI, the RSI along with hypoxia, and age has been identified as a potentially more significant role in ruling out hospital mortality in COVID-19 patients than vital signs alone, given the established role of hypoxia as a major risk factor in such cases.

Citations

Citations to this article as recorded by

Refining Oxygen-Carrying Capacity Metrics in Assessing Mortality Risk from Pneumonia in Children
Deepti M. Sati, Vanashri Dhananjay Shinde, Chhaya Agarwal
The Journal of Pediatrics.2026; 297: 115224. CrossRef

Review Articles

Surgery
Clinical applications of blood gas analysis: a comparative review of arterial and venous blood gas monitoring in critical care: Gyeo Ra Lee; Acute Crit Care. 2025;40(2):153-159. Published online May 30, 2025; DOI: https://doi.org/10.4266/acc.000900

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Abstract PDF

Blood gas analysis is an essential diagnostic tool used for assessing acid-base balance, ventilation, and oxygenation in critically ill patients. Arterial blood gas analysis (ABGA) remains the gold standard, primarily due to its accuracy in measuring oxygenation. Venous blood gas analysis (VBGA), in contrast, serves as a less invasive alternative and is particularly useful for evaluating acid-base status and metabolic function. Important parameters such as oxygen saturation of central venous blood (ScvO₂) and venous-to-arterial carbon dioxide pressure difference (∆pv-aCO₂) provide critical insights into hemodynamic status, cardiac output, and tissue perfusion. Although VBGA cannot replace ABGA for the precise assessment of oxygenation, it remains a valuable tool in clinical scenarios involving hemodynamic monitoring, shock management, and critical care decision-making.

Citations

Citations to this article as recorded by

Reference intervals for venous blood gas measurement in a healthy Chinese population
Sheng Jiang, Qian Zhao, Hua Wang, Min Li, Yuanzhu Ou, Weiwei Lin
Clinica Chimica Acta.2027; 592: 121212. CrossRef
Ultrasound guidance versus conventional technique for radial arterial puncture in patients with shock in the emergency department: a randomized controlled trial
Durmus Ali Ersahin, Ismail Erkan Aydin, Tugce Ersahin, Nalan Kozaci
BMC Emergency Medicine.2026;[Epub] CrossRef
Central venous oxygen saturation vs. oxygen extraction ratio in septic shock resuscitation: Which metric is more informative?
Athanasios Chalkias, Konstantina Katsifa, Stavroula Amanetopoulou, Aikaterini Nodarou, Petros Lampropoulos, Ioannis Thiveos, Konstantinos Sakellaridis, Varvara Grammatikopoulou, Athanasios Prekates, Paraskevi Tselioti
Anesthesiology and Perioperative Science.2026;[Epub] CrossRef
Beyond blood pressure: a comprehensive overview of clinical indices in shock and tissue hypoperfusion
Jooyun Kim, Saeyeon Kim, Ji-Hee Lee, Sua Kim
Acute and Critical Care.2026; 41(2): 201. CrossRef
Impacts of inspired oxygen concentration and arterial oxygen tension on venous and tissue oxygen saturation
Kwok Ming Ho
Acute and Critical Care.2026; 41(2): 436. CrossRef
Closing the Gap: Central Venous-to-Paco 2 Difference in Pediatric Shock
Michelle Adu-Darko
Pediatric Critical Care Medicine.2026; 27(7): 899. CrossRef
A population-adaptive decision-support method for ventilator parameter optimization
Xianhui Lian, Tianliang Hu, Songhua Ma, Dedong Ma
Knowledge-Based Systems.2026; 349: 116490. CrossRef
Vertical Displacement Index and Early Treatment-Related Physiological Improvement in Acute Respiratory Failure: An Exploratory Ultrasound-Based Study
Bedriye Müge Sönmez, İlker Şirin, Gülşen Akçay, Murat Özdemir, Necip Gökhan Güner
Advances in Respiratory Medicine.2026; 94(3): 40. CrossRef
Patient characteristics, vital signs and tcpCO2 dynamics significantly influence tcpCO2 accuracy in extremely preterm infants: an observational study
Lena Olivier, Camelia Lauterbach Oprea, André Stollenwerk, Valerie Pfannschmidt, Thorsten Orlikowsky, Mark Schoberer
Frontiers in Pediatrics.2026;[Epub] CrossRef
Essential Data Elements for Laboratory Test Interoperability: An Expert Consensus-Based Framework
Ha Nui Kim, Min-Sun Kim, Sollip Kim, Kuenyoul Park, Eun-Jung Cho, Hyejin Ryu, YeJin Oh, Shinae Yu, John Hoon Rim, Sang-Mi Kim, Geon Park, Jaehyeon Lee, Hyun-Seung Lee, Hyun-Woo Choi, You Kyoung Lee, Jeong Hwan Shin, Sang-Guk Lee, Young Kyung Lee, Jeong-Ye
Annals of Laboratory Medicine.2026; 46(5): 507. CrossRef
Assessing and Enhancing the Interpretation Quality of Arterial Blood Gas Among Junior Doctors
Abubakr Muhammed, Mohaned Altijani Abdalgadir Hamdnaalla, Fakher Aldeen Raft Fakher Aldeen Noman, Ahmed Altayeb Abbas Fadlallah, Mohammed Ali Mohammed Ali, Hanaa Ahmed Khalifa Elamin, Hala Aamir Abdelraouf Ahmed , Ameer Abdallatif Saeed Elkhazin, Hala Ome
Cureus.2025;[Epub] CrossRef
Using zlog in spider charts for fast diagnosis recognition
Johannes Böhm, Johannes Daubitzer, Thorsten M. Smul, Lisa-Maria Meier, Sven Schneider
Journal of Laboratory Medicine.2025; 49(6): 268. CrossRef
Predictive performance of central venous oxygen saturation, lactate, base excess, and alactic base excess for intradialytic hypotension
Angelica J. Luevanos-Aguilera
BMC Nephrology.2025;[Epub] CrossRef

Cardiology/Infection
How Do I Integrate Hemodynamic Variables When Managing Septic Shock?: Olfa Hamzaoui, Jean-Louis Teboul; Korean J Crit Care Med. 2016;31(4):265-275. Published online November 30, 2016; DOI: https://doi.org/10.4266/kjccm.2016.00927

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Abstract PDF

Hemodynamic management of sepsis-induced circulatory failure is complex since this pathological state includes multiple cardiovascular derangements that can vary from patient to patient according to the degree of hypovolemia, of vascular tone depression, of myocardial depression and of microvascular dysfunction. The treatment of the sepsis-induced circulatory failure is thus not univocal and should be adapted on an individual basis. As physical examination is insufficient to obtain a comprehensive picture of the hemodynamic status, numerous hemodynamic variables more or less invasively collected, have been proposed to well assess the severity of each component of the circulatory failure and to monitor the response to therapy. In this article, we first describe the hemodynamic variables, which are the most relevant to be used, emphasizing on their physiological meaning, their validation and their limitations in patients with septic shock. We then proposed a general approach for managing patients with septic shock by describing the logical steps that need to be followed in order to select and deliver the most appropriate therapies. This therapeutic approach is essentially based on knowledge of physiology, of pathophysiology of sepsis, and of published data from clinical studies that addressed the issue of hemodynamic management of septic shock.

Citations

Citations to this article as recorded by

Enhancement in Performance of Septic Shock Prediction Using National Early Warning Score, Initial Triage Information, and Machine Learning Analysis
Hyoungju Yun, Jeong Ho Park, Dong Hyun Choi, Sang Do Shin, Myoung-jin Jang, Hyoun-Joong Kong, Suk Wha Kim
The Journal of Emergency Medicine.2021; 61(1): 1. CrossRef

Original Article

Prognostic Factors for Mortality in Emergency Department Patients with Hypotension: Deuk Hyun Park, Young Rock Ha, Young Sik Kim, Tae Yong Shin, Sung Han Oh, Sung Sil Choi, Suk Young No; Korean J Crit Care Med. 2011;26(2):57-63.; DOI: https://doi.org/10.4266/kjccm.2011.26.2.57

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Abstract PDF

BACKGROUND
This study was performed to analyze the effects of differences between initial and follow up amounts of central venous oxygen saturation (Scvo2), lactate, anion gap (AG), and corrected anion gap (CAG).
METHODS
Patients with systolic blood pressure that was lower than 90 mmHg participated in this study. Along with Arterial Blood Gas Analysis (ABGA), the amounts of electrolytes, albumin, and Scvo2 were initially checked and then re-checked four hours later. The patients were divided into two groups, which were survived and expired, and the differences in initial and final values were compared in both groups. RESULTS: Out of a total of 36 patients, 29 patients survived and 7 patients died. The data showed almost no difference in mean age, mean arterial pressure, heart rate, respiratory rate, and body temperature between two groups. Comparing the initial amount, there was a statistically significant variation in lactate. Comparing the final values, lactate, AG, and CAG varied significantly. However, for both groups, the differences between the initial and final values were not significant. The area under curve (AUC) of follow up lactate and follow up CAG was 0.89 and 0.88. AUC of ED-APACHEII and original ICU APACHEII was 0.74 and 0.96.
CONCLUSIONS
There was no prognostic effect of Scvo2, lactate, AG, and CAG in hypotensive patients. The initial and final values of lactate and CAG were good prognostic factors for the expired group.

Citations

Citations to this article as recorded by

Death below 2 g/dL of Hemoglobin Concentrations: As an Independent Predictor of Death
Sun Young Park, Sung Hyun Kang, Sang Hoon Park, Hea Rim Jeon, Mun Gyu Kim, Se Jin Lee
Soonchunhyang Medical Science.2013; 19(1): 45. CrossRef
Analysis of Prognostic Factors Early in Emergency Department (ED) and Late in Intensive Care Unit (ICU) of the Critically Ill Patients Admitted in the ICU via ED
Ru-Bi Jeong, Jung-Hwan An, Hyun-Min Jun, Sung-Min Jeong, Tae-Yong Shin, Young-Sik Kim, Young-Rock Ha
Korean Journal of Critical Care Medicine.2012; 27(4): 237. CrossRef

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