Evaluating tissue hypoxia and the response to fluid administration in septic shock patients: a metabolic cluster analysis.

BACKGROUND: The selection of adequate indicators of tissue hypoxia for guiding the resuscitation process of septic patients is a highly relevant issue. Current guidelines advocate for the use of lactate as sole metabolic marker, which may be markedly limited, and the integration of different variables seems more adequate. In this study, we explored the metabolic profile and its implications in the response to the administration of a fluid challenge in early septic shock patients. METHODS: Observational study including septic shock patients within 24 h of ICU admission, monitored with a cardiac output estimation system, with ongoing resuscitation. Hemodynamic and metabolic variables were measured before and after a fluid challenge (FC). A two-step cluster analysis was used to define the baseline metabolic profile, including lactate, central venous oxygen saturation (ScvO2), central venous-to-arterial carbon dioxide difference (PcvaCO2), and PcvaCO2 corrected by the difference in arterial-to-venous oxygen content (PcvaCO2/CavO2). RESULTS: Seventy-seven fluid challenges were analyzed. Cluster analysis revealed two distinct metabolic profiles at baseline. Cluster A exhibited lower ScvO2, higher PcvaCO2, and lower PcvaCO2/CavO2. Increases in cardiac output (CO) were associated with increases in VO2 exclusively in cluster A. Baseline isolated metabolic variables did not correlate with VO2 response, and changes in ScvO2 and PcvaCO2 were associated to VO2 increase only in cluster A. CONCLUSIONS: In a population of early septic shock patients, two distinct metabolic profiles were identified, suggesting tissue hypoxia or dysoxia. Integrating metabolic variables enhances the ability to detect those patients whose VO2 might increase as results of fluid administration.

The relationship between perioperative central venous oxygen saturation and postoperative complications in highly invasive gastroenterological surgery.

Purpose: Operations for malignant diseases of the bile duct, pancreas, and esophagus are the most invasive gastroenterological surgeries. The frequency of complications after these surgeries is high, which affects the postoperative course and mortality. In patients who undergo these types of surgeries, continuous monitoring of the perioperative central venous oxygen saturation (ScvO2) is possible via a central venous catheter. We aimed to investigate the relationship between continuously monitored perioperative ScvO2 values and postoperative complications. Methods: The medical records of 115 patients who underwent highly invasive gastroenterological surgeries and ScvO2 monitoring from April 2012 to March 2014 were analyzed. Sixty patients met the inclusion criteria, and their ScvO2 levels were continuously monitored perioperatively. The relationship between ScvO2 levels and major postoperative complications, defined as Clavien-Dindo grade ≥ III, was examined using uni- and multivariate analysis. Results: Thirty patients developed major postoperative complications. The adequate cut-off value derived from receiver operating curves of the postoperative average ScvO2 levels for predicting major complications was 75%. Multivariate analysis revealed that low average postoperative ScvO2 levels (p = 0.016) and blood loss ≥ 1000 mL (p = 0.039) were significant predictors of major postoperative complications. Conclusions: Low perioperative ScvO2 values were associated with an increased risk of major postoperative complications. Continuous ScvO2 monitoring will help prevent postoperative complications.

Venoarterial Partial Pressure of Carbon Dioxide Difference: Let's Trend It!

How to cite this article: Ravisankar NR. Venoarterial Partial Pressure of Carbon Dioxide Difference: Let's Trend It! Indian J Crit Care Med 2024;28(4):323-325.

Sleep-stage-dependent alterations in cerebral oxygen metabolism quantified by magnetic resonance.

A key function of sleep is to provide a regular period of reduced brain metabolism, which is critical for maintenance of healthy brain function. The purpose of this work was to quantify the sleep-stage-dependent changes in brain energetics in terms of cerebral metabolic rate of oxygen (CMRO2 ) as a function of sleep stage using quantitative magnetic resonance imaging (MRI) with concurrent electroencephalography (EEG) during sleep in the scanner. Twenty-two young and older subjects with regular sleep hygiene and Pittsburgh Sleep Quality Index (PSQI) in the normal range were recruited for the study. Cerebral blood flow (CBF) and venous oxygen saturation (SvO2 ) were obtained simultaneously at 3 Tesla field strength and 2.7-s temporal resolution during an 80-min time series using OxFlow, an in-house developed imaging sequence. The method yields whole-brain CMRO2 in absolute physiologic units via Fick's Principle. Nineteen subjects yielded evaluable data free of subject motion artifacts. Among these subjects, 10 achieved slow-wave (N3) sleep, 16 achieved N2 sleep, and 19 achieved N1 sleep while undergoing the MRI protocol during scanning. Mean CMRO2 was 98 ± 7(µmol min-1 )/100 g awake, declining progressively toward deepest sleep stage: 94 ± 10.8 (N1), 91 ± 11.4 (N2), and 76 ± 9.0 µmol min-1 /100 g (N3), with each level differing significantly from the wake state. The technology described is able to quantify cerebral oxygen metabolism in absolute physiologic units along with non-REM sleep stage, indicating brain oxygen consumption to be closely associated with depth of sleep, with deeper sleep stages exhibiting progressively lower CMRO2 levels.

Quantification of whole-organ individual and bilateral renal metabolic rate of oxygen.

PURPOSE: Renal metabolic rate of oxygen (rMRO2 ) is a potentially important biomarker of kidney function. The key parameters for rMRO2 quantification include blood flow rate (BFR) and venous oxygen saturation (SvO2 ) in a draining vessel. Previous approaches to quantify renal metabolism have focused on the single organ. Here, both kidneys are considered as one unit to quantify bilateral rMRO2 . A pulse sequence to facilitate bilateral rMRO2 quantification is introduced. METHODS: To quantify bilateral rMRO2 , measurements of BFR and SvO2 are made along the inferior vena cava (IVC) at suprarenal and infrarenal locations. From the continuity equation, these four parameters can be related to derive an expression for bilateral rMRO2 . The recently reported K-MOTIVE pulse sequence was implemented at four locations: left kidney, right kidney, suprarenal IVC, and infrarenal IVC. A dual-band variant of K-MOTIVE (db-K-MOTIVE) was developed by incorporating simultaneous-multi-slice imaging principles. The sequence simultaneously measures BFR and SvO2 at suprarenal and infrarenal locations in a single pass of 21 s, yielding bilateral rMRO2 . RESULTS: SvO2 and BFR are higher in suprarenal versus infrarenal IVC, and the renal veins are highly oxygenated (SvO2 >90%). Bilateral rMRO2 quantified in 10 healthy subjects (8 M, 30 ± 8 y) was found to be 291 ± 247 and 349 ± 300 (µmolO2 /min)/100 g, derived from K-MOTIVE and db-K-MOTIVE, respectively. In comparison, total rMRO2 from combining left and right was 329 ± 273 (µmolO2 /min)/100 g. CONCLUSION: The present work demonstrates that bilateral rMRO2 quantification is feasible with fair reproducibility and physiological plausibility. The indirect method is a promising approach to compute bilateral rMRO2 when individual rMRO2 quantification is difficult.

Unresponsive Low Mixed Venous Oxygen Saturation During Early Intensive Care Unit Stay is Associated With Increased Risk of Organ Dysfunction After Cardiac Surgery: A Single-Center Retrospective Study.

OBJECTIVES: The aim of the study was to determine if unresponsive mixed venous oxygen saturation (SvO2) values during early postoperative hours are associated with postoperative organ dysfunction. DESIGN: A single-center retrospective observational study. SETTING: A university hospital. PARTICIPANTS: A total of 6,282 adult patients requiring cardiac surgery who underwent surgery in a University Hospital from 2007 to 2020. INTERVENTIONS: A pulmonary artery catheter was used to gather SvO2 samples after surgery at admission to the intensive care unit (ICU) and 4 hours later. For the analysis, patients were divided into 4 groups according to their SvO2 values. The rate of organ dysfunctions categorized according to the SOFA score was then studied among these subgroups. MEASUREMENTS AND MAIN RESULTS: The crude mortality rate for the cohort at 1 year was 4.3%. Multiple organ dysfunction syndrome (MODS) was present in 33.0% of patients in the early postoperative phase. During the 4-hour initial treatment period, 43% of the 931 patients with low SvO2 on admission responded to goal-directed therapy to increase SvO2 >60%; whereas, in 57% of the 931 patients, the low SvO2 was sustained. According to the adjusted logistic regression analyses, the odds ratio for MODS (4.23 [95% CI 3.41-5.25]), renal- replacement therapy (4.97 [95% CI 3.28-7.52]), time on a ventilator (2.34 [95% CI 2.17-2.52]), and vasoactive-inotropic score >30 (3.62 [95% CI 2.96-4.43]) were the highest in the group with sustained low SvO2. CONCLUSIONS: Patients with SvO2 <60% at ICU admission and 4 hours later had the greatest risk of postoperative MODS. Responsiveness to a goal-directed therapy protocol targeting maintaining or increasing SvO2 ≥60% at and after ICU admission may be beneficial.

Evaluation of markers of cerebral oxygenation and metabolism in patients undergoing clipping of cerebral aneurysm under total intravenous anesthesia versus inhalational anesthesia: A prospective randomized trial (COM-IVIN trial).

INTRODUCTION: Anesthetic goals in patients undergoing clipping of cerebral aneurysm include maintenance of cerebral blood flow, oxygenation, and metabolism to avoid cerebral ischemia and maintenance of hemodynamic stability. We intend to study the influence of anesthetic agents on the outcome of aneurysmal subarachnoid hemorrhage (SAH). MATERIALS AND METHODS: This is a prospective, randomized, parallel, single-center pilot trial approved by the Institutional Ethics Committee and is prospectively registered with the Clinical Trial Registry of India. Patients with aneurysmal SAH (aSAH) admitted to our institution for surgical clipping, fulfilling the trial inclusion criteria, will be randomized in a 1:1 allocation ratio utilizing a computerized random allocation sequence to receive either total intravenous anesthesia (n = 25) or inhalational anesthesia (n = 25). Our primary objective is to study the effects of these anesthetic techniques on cerebral oxygenation and metabolism in patients with aSAH. Our secondary objective is to evaluate the impact of these anesthetic techniques on the incidence of delayed cerebral ischemia and long-term patient outcomes in patients with aSAH. The Modified Rankin Score and Glasgow Outcome Scale (GOS) at discharge and 3 months following hospital discharge will be evaluated. An observer blinded to the study intervention will assess the outcome measures. DISCUSSION: This study will provide more insight as to which is the ideal anesthetic agent that offers a better neurophysiological profile regarding intraoperative cerebral oxygenation and metabolism, thereby contributing to better postoperative outcomes in aSAH patients.

Impact of hypotension and global hypoperfusion in postoperative delirium: a pilot study in older adults undergoing open colon surgery / Impacto da hipotensão e hipoperfusão global sobre o delírio pós-operatório: um estudo piloto com idosos submetidos à cirurgia aberta do cólon

Abstract Background: Post-operative delirium is a serious complication in patients undergoing major abdominal surgery. It remains unclear whether peri-operative hemodynamic and perfusion variables affect the risk for postoperative delirium. The objective of this pilot study was to evaluate the association between perfusion and hemodynamics peri-operative with the appearance of post-operative delirium. Methods: Prospective cohort study of adults 60 years or older undergoing elective open colon surgery. Multimodal hemodynamic and perfusion variables were monitored, including central venous oxygenation (ScvO2), lactate levels, and non-invasive cerebral oxygenation (rSO2), according to a standard anesthesia protocol. Fisher's exact test or Student's t-test were used to compare patients who developed post-operative delirium with those who did not (p < 0.05). Results: We studied 28 patients, age 73 ± 7 years, 60.7% female. Two patients developed post-operative delirium (7.1%). These two patients had fewer years of education than those without delirium (p = 0.031). None of the peri-operative blood pressure variables were associated with incidence of post-operative delirium. In terms of perfusion parameters, postoperative ScvO2 was lower in the delirium than the non-delirium group, without reaching statistical significance (65 ± 10% vs. 74 ± 5%; p = 0.08), but the delta-ScvO2 (the difference between means post-operative and intra-operative) was associated with post-operative delirium (p = 0.043). Post-operative lactate and rSO2 variables were not associated with delirium. Conclusions: Our pilot study suggests an association between delta ScvO2 and post-operative delirium, and a tendency to lower post-operative ScvO2 in patients who developed delirium. Further studies are necessary to elucidate this association.

Resumo Justificativa: O delírio pós-operatório é uma complicação séria em pacientes submetidos à cirurgia abdominal de grande porte. Ainda não está claro se as variáveis hemodinâmicas e de perfusão no período perioperatório afetam o risco de delírio pós-operatório. O objetivo deste estudo piloto foi avaliar a associação entre perfusão e hemodinâmica no perioperatório com o surgimento de delírio pós-operatório. Métodos: Estudo prospectivo de coorte de adultos com 60 anos ou mais, submetidos à cirurgia eletiva aberta do cólon. As variáveis multimodais de hemodinâmica e perfusão foram monitoradas, inclusive oxigenação venosa central (ScvO2), níveis de lactato e oxigenação cerebral não invasiva (rSO2), de acordo com um protocolo-padrão de anestesia. O teste exato de Fisher ou o teste t de Student foram usados para comparar os pacientes que desenvolveram delírio pós-operatório com aqueles que não desenvolveram p < 0,05. Resultados: Avaliamos 28 pacientes, 73 ± 7 anos, 60,7% do sexo feminino. Dois pacientes desenvolveram delírio pós-operatório (7,1%). Esses dois pacientes tinham menos anos de escolaridade do que aqueles sem delírio pós-operatório (p = 0,031). Nenhuma das variáveis de pressão arterial no perioperatório foi associada à incidência de delírio. Quanto aos parâmetros de perfusão, ScvO2 foi menor no grupo que apresentou delírio pós-operatório do que no grupo que não apresentou delírio, sem atingir significância estatística (65 ± 10% vs. 74 ± 5%; p = 0,08), mas o delta-ScvO2 (a diferença entre as médias no pós-operatório e intraoperatório) foi associado ao delírio (p = 0,043). As variáveis de lactato e rSO2 no pós-operatório não foram associadas ao delírio. Conclusões: Nosso estudo piloto sugere uma associação entre delta-ScvO2 e delírio e uma tendência à diminuição da ScvO2 no pós-operatório de pacientes com delírio. Estudos adicionais são necessários para elucidar essa associação.

Influence of perfusion status on central and mixed venous oxygen saturation in septic patients / Influência do status perfusional nas saturações venosas de oxigênio central e mista em pacientes sépticos

Abstract Background and objectives Although there is controversy regarding the role of venous oxygen saturation in the initial resuscitation of septic patients with hypoperfusion these markers are still widely used. This study aimed to evaluate the correlation and concordance between central (SvcO2) and mixed (SvO2) oxygen saturation in septic shock patients with or without hypoperfusion in addition to the impact of these differences in patient conduction. Methods Patients with septic shock were monitored with pulmonary artery catheter and the following subgroups of hypoperfusion were analyzed: 1) lactate > 28 mg.dL-1; 2) base excess ≤ -5 mmol.L-1; 3) venoarterial CO2 gradient > 6 mmHg; 4) SvO2 < 65%; 5) SvcO2 < 70%; 6) lactate > 28 mg.dL-1 and SvO2 < 70%; 7) lactate > 28 mg.dL-1 and SvcO2 < 75%. Results Seventy-seven samples from 24 patients were included. There was only a moderate correlation between SvO2 and SvcO2 (r = 0.72, p = 0.0001) and there was no good concordance between these variables (7.35% bias and 95% concordance limits of -3.0% to 17.7%). Subgroup analysis according to the presence of hypoperfusion showed no differences in concordance between variables. There was discordance regarding clinical management in 13.8% (n = 9) of the cases. Conclusions There is a moderate correlation between SvO2 and SvcO2; however, the concordance between them is inadequate. It was not possible to demonstrate that the presence of hypoperfusion alters the concordance between SvO2 and SvcO2. The use of SvO2 instead of SvcO2 may lead to changes in clinical management in a small but clinically relevant portion of patients.

Resumo Justificativa e objetivos Embora haja controvérsias sobre o papel das saturações venosas de oxigênio na ressuscitação inicial do paciente séptico com hipoperfusão, esses marcadores são ainda bastante usados. Este estudo procurou avaliar a correlação e a concordância entre as saturações venosas central (SvcO2) e mista (SvO2) de oxigênio em pacientes com choque séptico, na presença ou não de hipoperfusão, além do impacto dessas diferenças na condução clínica do paciente. Métodos Foram incluídos pacientes com choque séptico monitorados com cateter de artéria pulmonar e analisados os seguintes subgrupos de hipoperfusão: 1) Lactato > 28 mg.dL-1; 2) Excesso de bases ≤ -5 mmoL.L-1; 3) Gradiente venoarterial de CO2 > 6 mmHg; 4) SvO2 < 65%; 5) SvcO2 < 70%; 6) Lactato > 28 mg.dL-1 e SvO2 < 70%; 7) Lactato > 28 mg.dL-1 e SvcO2 < 75%. Resultados Foram incluídas 70 amostras de 24 pacientes. Houve apenas correlação moderada entre SvO2 e SvcO2 (r = 0,72; p = 0,0001) e não houve boa concordância entre essas variáveis (viés de 7,35% e limites de concordância de 95% de -3,0%-17,7%). A análise dos subgrupos de acordo com a presença de hipoperfusão não mostrou diferenças na concordância entre as variáveis. Houve discordância na conduta clínica em 13,8% dos casos (n = 9). Conclusões Existe correlação moderada entre SvO2 e SvcO2, entretanto a concordância entre elas é inadequada. Não foi possível demonstrar que a presença de hipoperfusão altera a concordância entre a entre SvO2 e SvcO2. O uso da SvO2 em vez da SvcO2 pode levar a alterações na conduta clínica numa parcela pequena, porém clinicamente relevante, dos pacientes.

La saturación venosa central de oxígeno es un factor predictor de mortalidad en el paciente con choque séptico / Central venous oxygen saturation is a predictor of mortality in patients with septic shock

Objetivo: determinar si la saturación venosa central de oxigeno inicial (SvCO2) anormal (alta o baja) es un factor predictor de mortalidad en los pacientes con choque séptico que ingresan al área critica de emergencia del hospital "Carlos Andrade Marín". Diseño y lugar: estudio analítico, observacional, prospectivo sobre una cohorte de pacientes que ingresaron al área crítica de emergencia de este hospital. Pacientes: 107 sujetos ingresaron en los meses de junio a septiembre del 2015, con seguimiento para la mortalidad a 28 días. Medidas y resultados: se midió la SvcO2 inicial a través de un catéter venoso central al momento del diagnóstico de choque. La mortalidad a los 28 días fue de 46,2%. Solo los valores de APACHE II (OR:1,11; IC: 1,04 a 1,19 p=< 0,01); la asistencia ventilatoria mecánica (OR:0,19; IC: 0,05 a 0,62, p=<0,01) tuvieron un valor estadístico significativo en regresión logística. APACHE II fue el factor individual más importante, en el modelo CART, el pH arterial y procalcitonina fueron útiles. Conclusiones: la saturación venosa central de O2 inicial (SvcO2) anormal alta o baja no mostró tener utilidad para predecir mortalidad a los 28 días. La medición de la SvcO2 es un método simple que refleja de manera indirecta la oxigenación tisular. El APACHE II es un predictor independiente de mortalidad a 28 días y la ventilación mecánica tuvo una relación inversa con la mortalidad. (AU)

Objective: to determine the central venous saturation of abnormal initial oxygen (SvCO2) (high or low) as a predictor of mortality in patients with septic shock admitted to the emergency area of Carlos Andrade Marín Hospital. Design and location: this is an analytical, observational, prospective study on a cohort of patients admitted to the critical area of emergency of this health unit. Subjects: 107 patients admitted in the months of June to September 2015, with a mortality follow-up of 28-day. Measurements and results: initial SvcO2 was measured by central venous catheter at the time of shock diagnosis. Mortality at 28 days was 46.2%. Only APACHE II values (OR 1.11, CI 1.04-1.19 p = <0.01) and mechanical ventilation (OR 0.19, CI 0.05-0.62, p = 0.01) had significant statistical value in the logistic regression. APACHE II was the most important single factor, in the CART model arterial pH and procalcitonin were useful. Conclusion: Central venous saturation of abnormal or high initial O2 (SvcO2) was not found to be useful in predicting mortality at 28 days of follow-up. Measurement of SvcO2 is a simple method that indirectly reflects tissue oxygenation. The APACHE II is an independent predictor of mortality at 28 days and the use of mechanical ventilation had an inverse relationship with mortality. (AU)

El tiempo de llene capilar prolongado es predictor de una saturación venosa central de oxígeno disminuida / A prolonged capillary refill is predictor of low central venous oxygen saturation

Introduction: Educational programs in pediatric life support endorse a capillary refill time > 2 s as an indicator of shock. In the emergency room, a barrier to the implementation of an early goal directed therapy, aiming at central venous oxygen saturation (ScvO2) ≥ 70% is the insertion of central venous catheter (CVC). Objective: To establish the predictive value of capillary refill time > 2 s to detect ScvO2 < 70% in children admitted to Intensive Care Units. Patients and Method: Prospective study. We included 48 children admitted in the first 24 hours in ICU with superior vena cava CVC. Simultaneously, we measured ScvO2 and capillary refill time in the heel of upper extremity or toe. Results: There were 75 paired measurements ScvO2 (75,9 ± 8,4%) and capillary refill capillary (1,9 ± 1,0 s). We found an inverse correlation between capillary refill time and ScvO2 (r - 0,58 ). The ROC curve analysis revealed an excellent ability for the capillary fill time > 2 s to predict ScvO2 < 70% (AUC 0,94) (95% CI 0,87-0,98). Conclusions: A prolonged capillary refill time > 2 s, is a predictor of ScvO2 < 70% in children admitted to ICU, which supports the current recommendations. This finding may be relevant in emergency units where the use of CVC is limited and ScvO2 is not available.

Introducción: Programas educativos de reanimación pediátrica establecen que un tiempo de llene capilar > 2 s es un indicador de shock. En unidades de emergencia, una barrera para la implementación de una reanimación precoz guiada por metas, teniendo como objetivo una saturación venosa central de oxígeno (ScvO2) ≥ 70%, es la inserción de un catéter venoso central (CVC). Objetivo: Determinar el valor predictivo de un tiempo de llene capilar > 2 s en la detección de ScvO2 < 70% en niños ingresados a la Unidad de Cuidados Intensivos. Pacientes y Método: Estudio prospectivo. Se incluyeron 48 niños ingresados en las primeras 24 h en UCI con CVC en la vena cava superior. De manera simultánea se determinaron ScvO2 y tiempo de llene capilar en talón o dedo de extremidad superior. Resultados: Se obtuvieron 75 mediciones pareadas de ScvO2 (75,9 ± 8,4%) y llene capilar (1,9 ± 1,0 s), observándose una correlación inversa entre llene capilar y ScvO2 (r = -0,58). El análisis de la curva ROC reveló una excelente capacidad del tiempo de llene capilar > 2 s para predecir una ScvO2 < 70% (AUC = 0,94, IC 95% = 0,87-0,98). Conclusiones: La prolongación del tiempo de llene capilar > 2 s es predictor de ScvO2 < 70% en niños críticamente enfermos. Este hallazgo apoya las recomendaciones actuales y podría ser relevante en unidades de emergencia donde el uso de CVC es limitado y la ScvO2 no está disponible.