Effects of extracorporeal CO2 removal on gas exchange and ventilator settings: a systematic review and meta-analysis.

PURPOSE: A systematic review and meta-analysis to evaluate the impact of extracorporeal carbon dioxide removal (ECCO2R) on gas exchange and respiratory settings in critically ill adults with respiratory failure. METHODS: We conducted a comprehensive database search, including observational studies and randomized controlled trials (RCTs) from January 2000 to March 2022, targeting adult ICU patients undergoing ECCO2R. Primary outcomes were changes in gas exchange and ventilator settings 24 h after ECCO2R initiation, estimated as mean of differences, or proportions for adverse events (AEs); with subgroup analyses for disease indication and technology. Across RCTs, we assessed mortality, length of stay, ventilation days, and AEs as mean differences or odds ratios. RESULTS: A total of 49 studies encompassing 1672 patients were included. ECCO2R was associated with a significant decrease in PaCO2, plateau pressure, and tidal volume and an increase in pH across all patient groups, at an overall 19% adverse event rate. In ARDS and lung transplant patients, the PaO2/FiO2 ratio increased significantly while ventilator settings were variable. "Higher extraction" systems reduced PaCO2 and respiratory rate more efficiently. The three available RCTs did not demonstrate an effect on mortality, but a significantly longer ICU and hospital stay associated with ECCO2R. CONCLUSIONS: ECCO2R effectively reduces PaCO2 and acidosis allowing for less invasive ventilation. "Higher extraction" systems may be more efficient to achieve this goal. However, as RCTs have not shown a mortality benefit but increase AEs, ECCO2R's effects on clinical outcome remain unclear. Future studies should target patient groups that may benefit from ECCO2R. PROSPERO Registration No: CRD 42020154110 (on January 24, 2021).

PaCO2 is nonlinearly associated with NIV failure in patients with hypoxemic respiratory failure.

OBJECTIVE: To explore the association between PaCO2 and noninvasive ventilation (NIV) failure in patients with hypoxemic respiratory failure. METHODS: A retrospective study was performed in a respiratory ICU of a teaching hospital. Patients admitted to ICU between 2011 and 2019 were screened. We enrolled the patients with hypoxemic respiratory failure. However, patients who used NIV due to acute-on-chronic respiratory failure or heart failure were excluded. Data before the use of NIV were collected. Requirement of intubation was defined as NIV failure. RESULTS: A total of 1029 patients were enrolled in final analysis. The rate of NIV failure was 45% (461/1029). A nonlinear relationship between PaCO2 and NIV failure was found by restricted cubic splines (p = 0.03). The inflection point was 32 mmHg. The rate of NIV failure was 42% (224/535) in patients with PaCO2 >32 mmHg. However, it increased to 48% (237/494) in those with PaCO2 ≤ 32 mmHg. The crude and adjusted hazard ratio (HR) for NIV failure was 1.36 (95%CI:1.13-1.64) and 1.23(1.01-1.49), respectively, if the patients with PaCO2 >32 mmHg were set as reference. In patients with PaCO2 ≤ 32 mmHg, one unit increment of PaCO2 was associated with 5% reduction of NIV failure. However, it did not associate with NIV failure in patients with PaCO2 >32 mmHg. CONCLUSIONS: PaCO2 and NIV failure was nonlinear relationship. The inflection point was 32 mmHg. Below the inflection point, lower PaCO2 was associated with higher NIV failure. However, it did not associate with NIV failure above this point.

Perioperative Evaluation of Arterial and Venous Whole Blood in the Lamb (Ovis aries) Fontan Model.

Whole blood analysis can evaluate numerous parameters, including pH, pCO2, pO2, HCO3 - , base excess, glucose, electrolytes, lactate, blood urea nitrogen, creatinine, bilirubin, and hemoglobin. This valuable tool enables clinicians to make more informed decisions about patient care. However, the current body of literature describing perioperative whole blood analysis in Dorset sheep (Ovis aries) is small, so clinicians lack adequate information to guide their decision-making when evaluating test results. We evaluated arterial and venous whole blood pH, bicarbonate, pCO2, lactate, creatinine, and blood urea nitrogen before and for the first 24 hours after surgery in 2 cohorts of male and female Ovis arie s undergoing one of 2 major cardiovascular procedures, a Single-Stage Fontan or an inferior vena cava to pulmonary artery extracardiac conduit implantation (IP-ECC). The cohort undergoing a Single-Stage Fontan, which is the more complex procedure, exhibited greater deviation from baseline measurements than did the cohort undergoing the IP-ECC for lactate, bicarbonate, and creatinine. The cohort undergoing the IP-ECC showed no significant deviation from baseline for any parameters, potentially indicating a better safety margin than expected when compared with the Single-Stage Fontan. Together, these results indicate the clinical value of arterial and venous whole blood measurements in perioperative management of sheep and can provide a reference for clinicians managing sheep after significant cardiovascular procedures.

Evaluation of CO2 removal rate of ECCO2R for a renal replacement therapy platform in an experimental setting.

BACKGROUND: A critical parameter of extracorporeal CO2 removal (ECCO2R) applications is the CO2 removal rate (VCO2). Low-flow venovenous extracorporeal support with large-size membrane lung remains undefined. This study aimed to evaluate the VCO2 of a low-flow ECCO2R with large-size membrane lung using a renal replacement therapy platform in an experimental animal model. METHODS: Twelve healthy pigs were placed under mechanical ventilation and connected to an ECCO2R-CRRT system (surface area = 1.8 m2; OMNIset®, BBraun, Germany). Respiratory settings were reduced to induce two degrees of hypercapnia. VCO2 was recorded under different combinations of PaCO2 (50-69 or 70-89 mm Hg), extracorporeal blood flow (ECBF; 200 or 350 mL/min), and gas flow (4, 6, or 10 L/min). RESULTS: VCO2 increased with ECBF at all three gas flow rates. In severe hypercapnia, the increase in sweep gas flow from 4 to 10 L/min increased VCO2 from 86.38 ± 7.08 to 96.50 ± 8.71 mL/min at an ECBF of 350 mL/min, whereas at ECBF of 200 mL/min, any increase was less effective. But in mild hypercapnia, the increase in sweep gas flow result in significantly increased VCO2 at two ECBF. VCO2 increased with PaCO2 from 50-69 to 70-89 mm Hg at an ECBF of 350 mL/min, but not at ECBF of 200 mL/min. Post-membrane lung PCO2 levels were similar for different levels of premembrane lung PCO2 (p = 0.08), highlighting the gas exchange diffusion efficacy of the membrane lung in gas exchange diffusion. In severe hypercapnia, the reduction of PaCO2 elevated from 11.5% to 19.6% with ECBF increase only at a high gas flow of 10 L/min (p < 0.05) and increase of gas flow significantly reduced PaCO2 only at a high ECBF of 350 mL/min (p < 0.05). CONCLUSIONS: Low-flow venovenous extracorporeal ECCO2R-CRRT with large-size membrane lung is more efficient with the increase of ECBF, sweep gas flow rate, and the degree of hypercapnia. The influence of sweep gas flow on VCO2 depends on the ECBF and degree of hypercapnia. Higher ECBF and gas flow should be chosen to reverse severe hypercapnia.

Retrospective Validation of a Computerized Physiologic Equation to Predict Minute Ventilation Needs in Critically Ill Children.

OBJECTIVES: Mechanical ventilation (MV) is pervasive among critically ill children. We sought to validate a computerized physiologic equation to predict minute ventilation requirements in children and test its performance against clinician actions in an in silico trial. DESIGN: Retrospective, electronic medical record linkage, cohort study. SETTING: Quaternary PICU. PATIENTS: Patients undergoing invasive MV, serial arterial blood gas (ABG) analysis within 1-6 hours, and pharmacologic neuromuscular blockade (NMB). MEASUREMENTS AND MAIN RESULTS: ABG values were filtered to those occurring during periods of NMB. Simultaneous ABG and minute ventilation data were linked to predict serial Pa co2 and pH values using previously published physiologic equations. There were 15,121 included ABGs across 500 encounters among 484 patients, with a median (interquartile range [IQR]) of 20 (10-43) ABGs per encounter at a duration of 3.6 (2.1-4.2) hours. The median (IQR) Pa co2 prediction error was 0.00 (-3.07 to 3.00) mm Hg. In Bland-Altman analysis, the mean error was -0.10 mm Hg (95% CI, -0.21 to 0.01 mm Hg). A nested, in silico trial of ABGs meeting criteria for weaning (respiratory alkalosis) or escalation (respiratory acidosis), compared the performance of recommended ventilator changes versus clinician decisions. There were 1,499 of 15,121 ABGs (9.9%) among 278 of 644 (43.2%) encounters included in the trial. Calculated predictions were favorable to clinician actions in 1124 of 1499 ABGs (75.0%), equivalent to clinician choices in 26 of 1499 ABGs (1.7%), and worse than clinician decisions in 349 of 1499 ABGs (23.3%). Calculated recommendations were favorable to clinician decisions in sensitivity analyses limiting respiratory rate, analyzing only when clinicians made changes, excluding asthma, and excluding acute respiratory distress syndrome. CONCLUSIONS: A computerized equation to predict minute ventilation requirements outperformed clinicians' ventilator adjustments in 75% of ABGs from critically ill children in this retrospective analysis. Prospective validation studies are needed.

Changes in arterial pH do not explain the reductions in ionised calcium observed during COVID-19 infection.

BACKGROUND: Hypocalcaemia predicts coronavirus disease 2019 (COVID-19) severity and mortality. We hypothesized an association between respiratory alkalosis secondary to hypoxia and low ionised calcium (iCa) concentration in patients with COVID-19. METHODS: Arterial blood gas samples taken from January 2019 to March 2021 were retrospectively matched with infection status. Principal components regression was undertaken to determine the correlation between pH, partial pressure arterial oxygen (PaO2), partial pressure arterial carbon dioxide (PaCO2), and iCa. RESULTS: We included 4056 patients (300 COVID-19 detected, 19 influenza detected), corresponding to 5960 arterial blood samples. The COVID-19 detected group had a statistically significantly lower iCa, PaO2 and PaCO2, and more alkalotic pH than infection-free groups. The influenza group had a lower iCa and PaCO2, higher PaO2, and a more alkalotic pH than infection-free groups, but these differences were non-significant. Principal components regression revealed that pH, PaCO2, and PaO2 explain just 2.72 % of the variance in iCa. An increase in pH by 1 unit was associated with an iCa reduction of 0.141 â€‹mmol/L (p â€‹< â€‹0.0001). CONCLUSION: Reduction in iCa concentration in patients with COVID-19 is not associated with pH derangement. Influenza infection was associated with a minor reduction in iCa in our small sample, a hitherto unreported finding, although statistical significance was not demonstrated.

Venous-to-arterial carbon-dioxide tension difference as a useful predictor of patient prognosis after major surgery.

PURPOSE: Change in venous-to-arterial carbon dioxide partial pressure difference[P(v-a)CO2] could be a useful marker to assess tissue perfusion status. Herein, we assessed the predictive values of postoperative P(v-a)CO2 measurements for mortality in critically ill patients after major surgery. The correlation between P(v-a)CO2 values and other conventional parameters of patient prognosis was also evaluated. METHODS: Patients admitted to the intensive care unit(ICU) after abdominal surgery were enrolled. Arterial and venous blood gas analyses were performed within 1 h(T0) and after 24 h(T1) of admission to the ICU, respectively. The relationship between P(v-a)CO2 levels at T1 and other conventional parameters were assessed using a Bland-Altman plot. Logistic regression analysis was performed to examine the predisposing factors of mortality after surgery. RESULTS: A total of 231 patients were finally analyzed. We divided the participants into the high PvaCO2 group[P(v-a)CO2 ≥ 8.6] and the low PvaCO2 group[P(v-a)CO2 < 8.6]. Seven-day-, 28-day, and in-hospital mortality were significantly higher in the high PvaCO2 group than in the low PvaCO2 group. There was significant agreement between P(v-a)CO2 values at T1 and APACHE II scores, lactate levels at T1 and total SOFA scores at T1. In multivariate logistic analysis, an increased P(v-a)CO2 value at T1 was the only significant risk factor of 7-day mortality after surgery. [odds ratio:1.341, 95%confidence interval: 1.050-1.714, p=0.019]. CONCLUSION: P(v-a)CO2 measurements could be not only a significant predictor of postoperative prognosis, but also a useful surveillance parameter to maintain tissue perfusion after abdominal surgery in patients with a potential risk of fatal complication-related tissue hypoperfusion.

The effect of high-flow nasal oxygen flow rate on gas exchange in apnoeic patients: a randomised controlled trial.

High-flow nasal oxygen can be administered at induction of anaesthesia for the purposes of pre-oxygenation and apnoeic oxygenation. This intervention is claimed to enhance carbon dioxide elimination during apnoea, but the extent to which this occurs remains poorly quantified. The optimal nasal oxygen flow rate for gas exchange is also unknown. In this study, 114 patients received pre-oxygenation with high-flow nasal oxygen at 50 l.min-1. At the onset of apnoea, patients were allocated randomly to receive one of three nasal oxygen flow rates: 0 l.min-1; 70 l.min-1; or 120 l.min-1. After 4 minutes of apnoea, all oxygen delivery was ceased, tracheal intubation was performed, and oxygen delivery was recommenced when SpO2 was 92%. Mean (SD) PaCO2 rise during the first minute of apnoea was 1.39 (0.39) kPa, 1.41 (0.29) kPa, and 1.26 (0.38) kPa in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, respectively; p = 0.16. During the second, third and fourth minutes of apnoea, mean (SD) rates of rise in PaCO2 were 0.34 (0.08) kPa.min-1, 0.36 (0.06) kPa.min-1 and 0.37 (0.07) kPa.min-1 in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, respectively; p = 0.17. After 4 minutes of apnoea, median (IQR [range]) arterial oxygen partial pressures in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups were 24.5 (18.6-31.4 [12.3-48.3]) kPa; 36.6 (28.1-43.8 [9.8-56.9]) kPa; and 37.6 (26.5-45.4 [11.0-56.6]) kPa, respectively; p < 0.001. Median (IQR [range]) times to desaturate to 92% after the onset of apnoea in the 0 l.min-1, 70 l.min-1 and 120 l.min-1 groups, were 412 (347-509 [190-796]) s; 533 (467-641 [192-958]) s; and 531 (462-681 [326-1007]) s, respectively; p < 0.001. In conclusion, the rate of carbon dioxide accumulation in arterial blood did not differ significantly between apnoeic patients who received high-flow nasal oxygen and those who did not.

PCO 2 Gradient Between Inlet and Outlet Blood of Extracorporeal Respiratory Support Is a Reliable Marker of CO 2 Elimination.

Our objective was to assess the relationship between the pre-/post-oxygenator gradient of the partial pressure of carbon dioxide (∆ EC PCO 2 ; dissolved form) and CO 2 elimination under extracorporeal respiratory support. All patients who were treated with veno-venous extracorporeal membrane oxygenation and high-flow extracorporeal CO 2 removal in our intensive care unit over 18 months were included. Pre-/post-oxygenator blood gases were collected every 12 h and CO 2 elimination was calculated for each pair of samples (pre-/post-oxygenator total carbon dioxide content in blood [ ct CO 2 ] × pump flow [extracorporeal pump flow {Q EC }]). The relationship between ∆ EC PCO 2 and CO 2 elimination, as well as the origin of CO 2 removed. Eighteen patients were analyzed (24 oxygenators and 293 datasets). Each additional unit of ∆ EC PCO 2 × Q EC was associated with an increase in CO 2 elimination of 5.2 ml (95% confidence interval [CI], 4.7-5.6 ml; p < 0.001). Each reduction of 1 ml STPD/dl of CO 2 across the oxygenator was associated with a reduction of 0.63 ml STPD/dl (95% CI, 0.60-0.66) of CO 2 combined with water, 0.08 ml STPD/dl (95% CI, 0.07-0.09) of dissolved CO 2 , and 0.29 ml STPD/dl (95% CI, 0.27-0.31) of CO 2 in erythrocytes. The pre-/post-oxygenator PCO 2 gradient under extracorporeal respiratory support is thus linearly associated with CO 2 elimination; however, most of the CO 2 removed comes from combined CO 2 in plasma, generating bicarbonate.

Establishment of a reference interval for total carbon dioxide using indirect methods in Chinese populations living in high-altitude areas: A retrospective real-world analysis.

BACKGROUND: Hypoxia leads to different concentrations of the bicarbonate buffer system in Tibetan people. Indirect methods were used to establish the reference interval (RI) for total carbon dioxide (tCO2) based on big data from the adult population of Tibet, a high-altitude area in Western China. METHODS: Anonymous tCO2 test data (n = 442,714) were collected from the People's Hospital of the Tibet Autonomous Region from January 2018, to December 2021. Multiple linear regression and variance component analyses were performed to assess the effects of sex, age, and race on tCO2 levels. Indirect methods, including Hoffmann, Bhattacharya, expectation maximization (EM), kosmic and refineR, were used to calculate the total RI and ethnicity-partitioned RI. RESULTS: A total of 230,821 real-world tCO2 test results were eligible. Sex, age, and race were significantly associated with the tCO2 levels. The total and ethnically-partitioned RIs estimated using the five indirect methods were comparable. The total RI of tCO2 was 14-24 mmol/L (calculated using Hoffmann and refineR) and 15-24 mmol/L (Bhattacharya, EM and kosmic). For Han nationality, the RIs were 14-25 mmol/L (calculated using Hoffmann and Bhattacharya), 16-23 mmol/L (EM), 15-24 mmol/L (kosmic), and 14.2-24.5 mmol/L (refineR). For the Tibetan population, the RIs were 14-24 mmol/L (calculated using Hoffmann and refineR), 15-24 mmol/L (Bhattacharya and kosmic), and 15-23 mmol/L (EM). The established RIs were significantly lower than those living at lower altitudes area (22-29 mmol/L) that was provided by the manufacturer. CONCLUSION: The tCO2 RI of the populations living on the Tibetan Plateau was significantly lower than those at the lower altitudes. The RIs established using indirect methods are suitable for clinical applications in Tibet.

Mild Hypercapnia or Normocapnia after Out-of-Hospital Cardiac Arrest.

BACKGROUND: Guidelines recommend normocapnia for adults with coma who are resuscitated after out-of-hospital cardiac arrest. However, mild hypercapnia increases cerebral blood flow and may improve neurologic outcomes. METHODS: We randomly assigned adults with coma who had been resuscitated after out-of-hospital cardiac arrest of presumed cardiac or unknown cause and admitted to the intensive care unit (ICU) in a 1:1 ratio to either 24 hours of mild hypercapnia (target partial pressure of arterial carbon dioxide [Paco2], 50 to 55 mm Hg) or normocapnia (target Paco2, 35 to 45 mm Hg). The primary outcome was a favorable neurologic outcome, defined as a score of 5 (indicating lower moderate disability) or higher, as assessed with the use of the Glasgow Outcome Scale-Extended (range, 1 [death] to 8, with higher scores indicating better neurologic outcome) at 6 months. Secondary outcomes included death within 6 months. RESULTS: A total of 1700 patients from 63 ICUs in 17 countries were recruited, with 847 patients assigned to targeted mild hypercapnia and 853 to targeted normocapnia. A favorable neurologic outcome at 6 months occurred in 332 of 764 patients (43.5%) in the mild hypercapnia group and in 350 of 784 (44.6%) in the normocapnia group (relative risk, 0.98; 95% confidence interval [CI], 0.87 to 1.11; P = 0.76). Death within 6 months after randomization occurred in 393 of 816 patients (48.2%) in the mild hypercapnia group and in 382 of 832 (45.9%) in the normocapnia group (relative risk, 1.05; 95% CI, 0.94 to 1.16). The incidence of adverse events did not differ significantly between groups. CONCLUSIONS: In patients with coma who were resuscitated after out-of-hospital cardiac arrest, targeted mild hypercapnia did not lead to better neurologic outcomes at 6 months than targeted normocapnia. (Funded by the National Health and Medical Research Council of Australia and others; TAME ClinicalTrials.gov number, NCT03114033.).

Femoral blood gas analysis, another tool to assess hemorrhage severity following trauma: an exploratory prospective study.

BACKGROUND: Veno-arterial carbon dioxide tension difference (ΔPCO2) and mixed venous oxygen saturation (SvO2) have been shown to be markers of the adequacy between cardiac output and metabolic needs in critical care patients. However, they have hardly been assessed in trauma patients. We hypothesized that femoral ΔPCO2 (ΔPCO2 fem) and SvO2 (SvO2 fem) could predict the need for red blood cell (RBC) transfusion following severe trauma. METHODS: We conducted a prospective and observational study in a French level I trauma center. Patients admitted to the trauma room following severe trauma with an Injury Severity Score (ISS) > 15, who had arterial and venous femoral catheters inserted were included. ΔPCO2 fem, SvO2 fem and arterial blood lactate were measured over the first 24 h of admission. Their abilities to predict the transfusion of at least one pack of RBC (pRBCH6) or hemostatic procedure during the first six hours of admission were assessed using receiver operating characteristics curve. RESULTS: 59 trauma patients were included in the study. Median ISS was 26 (22-32). 28 patients (47%) received at least one pRBCH6 and 21 patients (35,6%) had a hemostatic procedure performed during the first six hours of admission. At admission, ΔPCO2 fem was 9.1 ± 6.0 mmHg, SvO2 fem 61.5 ± 21.6% and blood lactate was 2.7 ± 1.9 mmol/l. ΔPCO2 fem was significantly higher (11.6 ± 7.1 mmHg vs. 6.8 ± 3.7 mmHg, P = 0.003) and SvO2 fem was significantly lower (50 ± 23 mmHg vs. 71.8 ± 14.1 mmHg, P < 0.001) in patients who were transfused than in those who were not transfused. Best thresholds to predict pRBCH6 were 8.1 mmHg for ΔPCO2 fem and 63% for SvO2 fem. Best thresholds to predict the need for a hemostatic procedure were 5.9 mmHg for ΔPCO2 fem and 63% for SvO2 fem. Blood lactate was not predictive of pRBCH6 or the need for a hemostatic procedure. CONCLUSION: In severe trauma patients, ΔPCO2 fem and SvO2 fem at admission were predictive for the need of RBC transfusion and hemostatic procedures during the first six hours of management while admission lactate was not. ΔPCO2 fem and SvO2 fem appear thus to be more sensitive to blood loss than blood lactate in trauma patients, which might be of importance to early assess the adequation of tissue blood flow with metabolic needs.

Papel del Delta de PCO2 en la evaluación pronóstica de morbimortalidad en una cohorte de pacientes de un hospital latinoamericano / Role of PCO2 Delta in the Prognostic Evaluation of Morbidity and Mortality in a Cohort of Patients from a Latin American Hospital

Introducción. El shock séptico es la manifestación más grave de sepsis con tasas de letalidad que pueden llegar hasta el 80%. En los últimos años, ha cobrado relevancia la diferencia arteriovenosa de dióxido de carbono, por su implicación teórica en el metabolismo anaerobio y su significado respecto del normal funcionamiento celular. Por lo antes mencionado, creemos necesario realizar un estudio que nos permita establecer la utilidad de la diferencia arteriovenosa de dióxido de carbono en el paciente con shock séptico de la unidad de cuidados intensivos, como medida indirecta de la perfusión tisular y de la utilización de oxígeno por los tejidos, que nos permita establecer un diagnóstico precoz y el pronóstico de los pacientes críticamente enfermos. Métodos. Estudio observacional, descriptivo y transversal. Muestra de veintiocho pacientes adultos. Resultados. Como se ha registrado en otras series, la mayor parte de los pacientes afectados por shock séptico, en nuestro estudio, fueron hombres mayores de 65 años, con al menos una comorbilidad, siendo el principal sitio de infección el respiratorio (67,9%), asociado a una alta tasa de mortalidad (67%). Conclusiones. Los pacientes con diferencia arteriovenosa de PCO2 mayor a 6 mmHg tienen un riesgo aumentado de muerte de 3,2 veces. (AU)

Introduction. Septic shock is the most serious manifestation of sepsis with mortality rates that can reach up to 80%. In recent years, the arteriovenous carbon dioxide difference has gained relevance, due to its theoretical implication in anaerobic metabolism and its significance with respect to normal cell function. Due to the aforementioned, we believe it is necessary to carry out a study that allows us to establish the usefulness of the arteriovenous carbon dioxide difference in the patient with septic shock in the intensive care unit as an indirect measure of tissue perfusion and utilization. of oxygen through the tissues, which allows us to establish an early diagnosis and prognosis of critically ill patients. Methods. Observational, descriptive and cross-sectional study. Sample of 28 adult patients. Results. As has been reported in other series, most of the patients affected by septic shock in our study were men over 65 years of age, with at least one comorbidity, the main site of infection being respiratory (67.9%), associated with a high mortality rate (67%) Conclusions. Patients with an arteriovenous PCO2 difference greater than 6 mmHg have a 3.2-fold increased risk of death. (AU)

Arterial oxygen and carbon dioxide tension and acute brain injury in extracorporeal cardiopulmonary resuscitation patients: Analysis of the extracorporeal life support organization registry.

BACKGROUND: Acute brain injury (ABI) remains common after extracorporeal cardiopulmonary resuscitation (ECPR). Using a large international multicenter cohort, we investigated the impact of peri-cannulation arterial oxygen (PaO2) and carbon dioxide (PaCO2) on ABI occurrence. METHODS: We retrospectively analyzed adult (≥18 years old) ECPR patients in the Extracorporeal Life Support Organization registry from 1/2009 through 12/2020. Composite ABI included ischemic stroke, intracranial hemorrhage (ICH), seizures, and brain death. The registry collects 2 blood gas data pre- (6 hours) and post- (24 hours) cannulation. Blood gas parameters were classified as: hypoxia (<60mm Hg), normoxia (60-119mm Hg), and mild (120-199mm Hg), moderate (200-299mm Hg), and severe hyperoxia (≥300mm Hg); hypocarbia (<35mm Hg), normocarbia (35-44mm Hg), mild (45-54mm Hg) and severe hypercarbia (≥55mm Hg). Missing values were handled using multiple imputation. Multivariable logistic regression analysis was used to assess the relationship of PaO2 and PaCO2 with ABI. RESULTS: Of 3,125 patients with ECPR intervention (median age=58, 69% male), 488 (16%) experienced ABI (7% ischemic stroke; 3% ICH). In multivariable analysis, on-ECMO moderate (aOR=1.42, 95%CI: 1.02-1.97) and severe hyperoxia (aOR=1.59, 95%CI: 1.20-2.10) were associated with composite ABI. Additionally, severe hyperoxia was associated with ischemic stroke (aOR=1.63, 95%CI: 1.11-2.40), ICH (aOR=1.92, 95%CI: 1.08-3.40), and in-hospital mortality (aOR=1.58, 95%CI: 1.21-2.06). Mild hypercarbia pre-ECMO was protective of composite ABI (aOR=0.61, 95%CI: 0.44-0.84) and ischemic stroke (aOR=0.56, 95%CI: 0.35-0.89). CONCLUSIONS: Early severe hyperoxia (≥300mm Hg) on ECMO was a significant risk factor for ABI and mortality. Careful consideration should be given in early oxygen delivery in ECPR patients who are at risk of reperfusion injury.

Predictors of Prolonged Hospital Stay in Patients with Acute Pulmonary Thromboembolism- A Hospital Based Cohort Study.

AIMS AND OBJECTIVES: Patients with pulmonary thromboembolism (PTE) are commonly admitted to hospital and generally have a prolonged hospital stay in this part of the world. We aimed to determine different clinical and laboratory parameters that are associated with prolonged hospital stay in our set-up and to analyse effectiveness of Pulmonary Embolism Severity Index (PESI) score as a predictor of prolonged hospital stay in patients with PTE. MATERIALS AND METHODS: It was a hospital based observational prospective study. Confirmed cases of PTE defined as patients with evidence of thrombus on CT pulmonary angiogram (CTPA) were included in this study. Depending on the length of hospital stay, patients were divided into two cohorts: Shorter Hospital stay (less than mean i.e., < 10 Days) and Prolonged Hospital stay (longer than mean i.e., ≥ 10 Days). Logistic regression analysis was done to identify predictors of prolonged hospital stay. RESULTS: 150 patients were included in the study with 67 patients (44.67%) having shorter hospital stay (<10 days) and 83 patients (55.33%) having prolonged hospital stay (≥10 days). On multivariate regression analysis, parameters that were found to be statistically significant were hypotension at presentation, decreased level of consciousness, pco2 < 30 mmHg, presence of S1Q3T3 pattern on electrocardiogram (ECG) and high risk PESI (class III-V). CONCLUSION: PESI class can be effectively used to predict prolonged hospital stay in patients with pulmonary embolism. Patients with hypotension at presentation, decreased level of consciousness, pco2 less than 30 mmHg, and S1Q3T3 on ECG are more likely to have prolonged hospital stay in our healthcare setup.

Dynamic oxygenator blood volume during prolonged extracorporeal life support.

Current methods for identification of oxygenator clotting during prolonged extracorporeal life support include visual inspection, evaluation of oxygenator resistance and oxygen exchange performance, and assessment of clotting-related laboratory parameters. However, these observations do not provide a quantitative assessment of oxygenator clot formation. By measuring changes in the dynamic oxygenator blood volume this study aimed to evaluate the relation to oxygenator resistance and oxygen transfer performance. Sixty-seven oxygenators were studied during adult extracorporeal life support. Oxygenator blood volume, oxygenator resistance, and oxygen transfer efficiency were monitored. Oxygenator blood volume decreased with increasing runtime (r = -0.462; p <0.001). There was a statistically significant, fair negative correlation between oxygenator blood volume and oxygenator resistance (r = -0.476; p<0.001) in all oxygenators, which became stronger analyzing only exchanged oxygenators (r = -0.680; p<0.001) and oxygenators with an oxygenator blood volume <187 mL (r = 0.831; p<0.001). No relevant correlation between oxygenator blood volume and O2 transfer was found. Oxygenator blood volume declined over time and was clearly associated with an increasing oxygenator resistance during prolonged extracorporeal life support, though O2 transfer was less affected.

Cerebrovascular and blood pressure responses during voluntary apneas are larger than rebreathing.

Both voluntary rebreathing (RB) of expired air and voluntary apneas (VA) elicit changes in arterial carbon dioxide and oxygen (CO2 and O2) chemostimuli. These chemostimuli elicit synergistic increases in cerebral blood flow (CBF) and sympathetic nervous system activation, with the latter increasing systemic blood pressure. The extent that simultaneous and inverse changes in arterial CO2 and O2 and associated increases in blood pressure affect the CBF responses during RB versus VAs are unclear. We instrumented 21 healthy participants with a finometer (beat-by-beat mean arterial blood pressure; MAP), transcranial Doppler ultrasound (middle and posterior cerebral artery velocity; MCAv, PCAv) and a mouthpiece with sample line attached to a dual gas analyzer to assess pressure of end-tidal (PET)CO2 and PETO2. Participants performed two protocols: RB and a maximal end-inspiratory VA. A second-by-second stimulus index (SI) was calculated as PETCO2/PETO2 during RB. For VA, where PETCO2 and PETO2 could not be measured throughout, SI values were calculated using interpolated end-tidal gas values before and at the end of the apneas. MAP reactivity (MAPR) was calculated as the slope of the MAP/SI, and cerebrovascular reactivity (CVR) was calculated as the slope of MCAv or PCAv/SI. We found that compared to RB, VA elicited ~ fourfold increases in MAPR slope (P < 0.001), translating to larger anterior and posterior CVR (P ≤ 0.01). However, cerebrovascular conductance (MCAv or PCAv/MAP) was unchanged between interventions (P ≥ 0.2). MAP responses during VAs are larger than those during RB across similar chemostimuli, and differential CVR may be driven by increases in perfusion pressure.

Pre-oxygenation with facemask oxygen vs high-flow nasal oxygen vs high-flow nasal oxygen plus mouthpiece: a randomised controlled trial.

High-flow nasal oxygen used before and during apnoea prolongs time to desaturation at induction of anaesthesia. It is unclear how much oxygenation before apnoea prolongs this time. We randomly allocated 84 participants to 3 minutes of pre-oxygenation by one of three methods: 15 l.min-1 by facemask; 50 l.min-1 by high-flow nasal cannulae only; or 50 l.min-1 by high-flow nasal cannulae plus 15 l.min-1 by mouthpiece. We then anaesthetised and intubated the trachea of 79 participants and waited for oxygen saturation to fall to 92%. Median (IQR [range]) times to desaturate to 92% after pre-oxygenation with facemask oxygen, high-flow nasal oxygen only and high-flow nasal oxygen with mouthpiece, were: 309 (208-417 [107-544]) s; 344 (250-393 [194-585]) s; and 386 (328-498 [182-852]) s, respectively, p = 0.014. Time to desaturation after facemask pre-oxygenation was shorter than after combined nasal and mouthpiece pre-oxygenation, p = 0.006. We could not statistically distinguish high-flow nasal oxygen without mouthpiece from the other two groups for this outcome. Median (IQR [range]) arterial oxygen partial pressure after 3 minutes of pre-oxygenation by facemask, nasal cannulae and nasal cannulae plus mouthpiece, was: 49 (36-61 [24-66]) kPa; 57 (48-62 [30-69]) kPa; and 61 (55-64 [36-72]) kPa, respectively, p = 0.003. Oxygen partial pressure after 3 minutes of pre-oxygenation with nasal and mouthpiece combination was greater than after facemask pre-oxygenation, p = 0.002, and after high-flow nasal oxygen alone, p = 0.016. We did not reject the null hypothesis for the pairwise comparison of facemask pre-oxygenation and high-flow nasal pre-oxygenation, p = 0.14.