CO2 Gap Research Articles

Mixed venous to arterial pCO2-gap is poorly correlated to cardiac index in 1526 pulmonary artery catheter monitored critically ill patients

Abstract Background The CO2 gap is the difference between mixed venous and arterial CO2, and can be estimated by the difference in partial pressure in CO2 (Pv-aCO2 or ∆PCO2). ∆PCO2 is affected by cardiac output (CO), CO2 production and solubility. The central venous-to-arterial CO2 gap has been proposed as a less invasive surrogate for P(v-a)CO2 and has been investigated as a measure of adequacy of resuscitation, and to guide sepsis management. Nevertheless, the CO2-gap as determinant of CO has never been thoroughly investigated in large cohort of critically ill ICU-patients. This study aims to investigate the relationship between ∆PCO2 and cardiac index (CI) in a retrospective cohort of critically ill patients in a large quaternary cardiothoracic intensive care unit. Methods Over 62 months, pulmonary artery catheter monitored critically ill patients were identified and their case files reviewed in retrospect. Extracorporeal membrane oxygenation (ECMO) patients were excluded. P(v-a)CO2 measurements were defined as mixed venous and arterial pCO2 measurements drawn simultaneously or within maximum 30 minutes together with PA-measurements. Correlation coefficients were calculated between P(v-a)CO2 and CI, serum lactate, mixed venous saturations (SvO2), cardiac power index (CPI), inotropic score (IS), central venous pressure (CVP) and minute expiratory volume (MV)(Table 1). We used receiver operator characteristic (ROC) curves to assess the diagnostic performance of P(v-a)CO2 as a surrogate for CI lower than 2,2L/min/m2. Multivariate linear regression analysis was performed with P(v-a)CO2 as an dependent variable. Results 4414 P(v-a)CO2 measurements were identified from 1526 patients. Median P(v-a)CO2 was 0,86 kPa (0,66-1,1) or 6.45 mmHg (4.95-8.25), and mean CI was 2.7l/min/m2 (2.2-3.2). Correlation coefficients of P(v-a)CO2 with the other variables remained poor (> 0,35). The area under the ROC curve for P(v-a)CO2 as a predictor of CI<2.2l/min/m2 was 0.65, p<0.0001 (Fig. 1B). A value of P(v-a)CO2 > 6.9 mmHg was found to have the highest sensitivity and specificity, with a poor performance of 61.21% sensitivity and 62.73% specificity. Conclusion This large retrospective study in 1526 critically ill cardiac ICU-patients did not demonstrate a strong relationship between P(v-a)CO2 and CI, nor with any other hemodynamic variable found in the ICU patient cohort studied (Table 1). This raises scepticism regarding the efficacy of P(v-a)CO2 as a physiological goal in guiding resuscitation and management of this precarious patient group. Therefore, we argue that the PA-catheter remains the cornerstone in assessing critically ill (cardiothoracic) ICU patients.

Pulse index contour continuous cardiac output (PICCO) monitoring in critically ill patients.

Objective: To evaluate the utility of Pulse index Contour Continuous Cardiac Output (PiCCO) monitoring in critically ill patients. Study Design: Cross-sectional study. Setting: Intensive Care Unti of Sindh Institute of Urology and Transplant, Karachi, Pakistan. Period: October 2022 to March 2023. Methods: Patients presenting with various types of shock, requiring high-dose vasopressors or inotropes, and not responding to initial fluid therapy were analyzed. Demographic details, SOFA score, APACHE score, and invasive hemodynamic parameters using the PiCCO system were documented. Results: Out of 142 ICU admissions, 38 patients were included in the study. Most patients were males (73%) with a median age of 39 years. Significant changes were observed in the cardiac index, cardiac performance index, global ejection fraction, and systemic vascular resistance index (SVRI), all with p-values less than 0.05. The interventions included the initiation of inotropes in 22 patients (57.8%), diuretics in 4 patients (10.5%), and intravenous fluids in 19 patients (50%). Additionally, vasopressor doses were adjusted in 18 patients (47.3%). Initially, patients were presumed to have pure septic shock based on CO2 gap, mixed venous saturation, and echocardiographic assessment. However, after applying PiCCO monitoring, the diagnosis was revised to mixed shock in 21 patients (55.2%). Conclusion: PiCCO monitoring appears to be a valuable tool in the ICU for managing patients with complex hemodynamic profiles, facilitating targeted interventions that lead to significant improvements in hemodynamic stability.

CO2 gap changes compared with cardiac output changes in response to intravenous volume expansion and/or vasopressor therapy in septic shock.

The difference in partial pressure of carbon dioxide (PCO2) between mixed or central venous blood and arterial blood, known as the ∆PCO2 or CO2 gap, has demonstrated a strong relationship with cardiac index during septic shock resuscitation. Early monitoring of the ∆PCO2 can help assess the cardiac output (CO) adequacy for tissue perfusion. To investigate the value of ∆PCO2 changes in early septic shock management compared with CO. This observational prospective study included 76 patients diagnosed with septic shock admitted to Cairo University Hospital's Critical Care Department between December 2020 and March 2022. Patients were categorised by initial resuscitation response, initial ∆PCO2 and 28-day mortality. The primary outcome was the relationship between the ∆PCO2 and CO changes before and after initial resuscitation, with secondary outcomes including ICU length of stay (LOS) and 28-day mortality. Peri-resuscitation ∆PCO2 changes predicted a ≥15% change in the cardiac index (CI) (area under the curve (AUC) 0.727; 95% CI 0.614 - 0.840) with 66.7% sensitivity and 62.8% specificity. The optimal ∆PCO2 change cut-off value was <-1.85, corresponding to a <-22% threshold for a 15% cardiac index increase. The PCO2 gap ratio (gap/gap ratio of T1- PCO2 gap to T0 -PCO2 gap) also predicted a ≥15% change in cardiac index (AUC 745; 95% CI 0.634 - 0.855) with 63.6% sensitivity and 79.1% specificity. The optimal CO2 gap/gap ratio cut-off value was <0.71. A significant difference in 28-day mortality was noted based on the gap/gap ratio. Peri-resuscitation ∆PCO2 and the gap/gap ratio are useful non-invasive bedside markers for predicting changes in CO and preload responsiveness. The current study provides an insight to the PCO2 gap changes during and after early resuscitation of septic shock patients, which correlate to cardiac output changes and might also serve as a fluid responsiveness indicator.

Relationship Between the Mixed Venous-to-Arterial Carbon Dioxide Gradient and Cardiac Index in Acute Pulmonary Embolism.

Among patients with acute pulmonary embolism (PE) undergoing mechanical thrombectomy, the cardiac index (CI) is frequently reduced even among those without clinically apparent shock. The purpose of this study was to describe the mixed venous-to-arterial carbon dioxide gradient (CO2 gap), a surrogate of perfusion adequacy, among patients with acute PE undergoing mechanical thrombectomy. This was a single-center retrospective study of consecutive patients with PE undergoing mechanical thrombectomy and simultaneous pulmonary artery catheterization over a 3-year period. Of 107 patients, 97 had simultaneous mixed venous and arterial blood gas measurements available. The CO2 gap was elevated (>6 mmHg) in 51% of the cohort and in 49% of patients with intermediate-risk PE. A reduced CI (≤2.2 L/min/m2) was associated with an increased odds (OR = 7.9; 95% CI 3.49-18.1, p < 0.001) for an elevated CO2 gap. There was an inverse relationship between CI and CO2 gap. For every 1 L/min/m2 decrease in the CI, the CO2 gap increased by 1.3 mmHg (p = 0.001). Among patients with an elevated baseline CO2 gap >6 mmHg, thrombectomy improved CO2 gap, CI, and mixed venous oxygen saturation. When the CO2 gap was dichotomized above and below 6, there was no difference in in-hospital mortality (9% vs. 0%; p = 0.10, HR: 1.24; 95% CI: 0.97-1.60; P = 0.085). Among patients with acute PE undergoing mechanical thrombectomy, the CO2 gap is abnormal in nearly 50% of patients and inversely related to CI. Further studies should examine the relationship between markers of perfusion and outcomes in this population to refine risk stratification.

A total closed chest swine model of acute myocardial infarction-related cardiogenic shock: A critical double coronary sub-occlusion approach

The management of acute myocardial infarction-related cardiogenic shock (AMICS) represents a significant challenge, with mortality rates remaining high (40–60%), despite recent advances. Current animal models of myocardial infarction are either associated with a very high rate of per-procedure malignant arrhythmia, or with very low impairment of hemodynamic parameters, or with the inability to have complete coronary reperfusion. We sought to develop a closed chest and clinically relevant large animal model of severe AMICS, with high survival rate. Adult pigs were anaesthetized and mechanically ventilated. Percutaneous cardiac catheterization was performed under fluoroscopy. Advanced left ventricular dysfunction was induced by 120 minutes of critical sub-occlusion of the proximal left anterior descending coronary artery and the mid circumflex artery. A thorough hemodynamic assessment was obtained by invasive and non-invasive monitoring devices. Repeated blood samples were obtained to determine blood gas parameters, lactate, and haemoglobin concentration. After death, the heart was retrieved for further histological analyses. All animals (n = 12) developed significant circulatory failure associated with AMICS upon reperfusion and beyond. No animal died during the ischemia process. However, all animals that did not benefited from vasopressor support (“sham” group, n = 4) spontaneously died within 30 minutes of reperfusion, confirming the severity of the model. Cardiogenic shock was characterized by a drop in mean arterial pressure below 60 mmHg (58 ± 5 mmHg at 120 min of ischemia), a significant decrease in mean cardiac output (−44% from 5.7 ± 0.4 at baseline to 3.2 ± 0.4 at 120 minutes of ischemia) and SvO2 (−32% from 57 ± 8 at baseline to 39 ± 6 at 120 minutes of ischemia) and a significant increase in left ventricle end-diastolic pressure (LVEDP) (+110% from 10 ± 3 at baseline to 21 ± 3 at 120 minutes of ischemia). CO2 gap and coronary sinus venous oxygen saturation increased significantly upon ischemia and reperfusion and remained elevated throughout (P ≤ 0.001 for all comparisons). Myocardial samples corroborated extensive cellular necrosis and inflammatory infiltrates. We present, for the first time, a stable and clinically relevant model of severe AMICS obtained by critical double coronary sub-occlusion. The greater severity of the model did not lead to an increase in the frequency of malignant arrythmias and per-procedure mortality.

An optimal dietary sodium chloride supplemental level of broiler chicks fed a corn-soybean meal diet from 1 to 21 days of age.

Sodium chloride (NaCl) is usually added to diets to meet the Na and Cl requirements of broilers in the Chinese poultry industry, but the optimal dietary NaCl supplemental level was not well-established. The present study was conducted to estimate the optimal dietary NaCl supplemental level of broilers fed a corn-soybean meal diet from 1 to 21 days of age. A total of 490, 1-day-old Arbor Acres male broilers were fed a NaCl-unsupplemented corn-soybean meal basal diet (control) and the basal diet supplemented with 0.10, 0.20, 0.30, 0.40, 0.50 or 0.60% NaCl for 21 days. Regression analysis was conducted to evaluate the optimal dietary NaCl level using the best fitted broken-line or asymptotic models. As dietary supplemental NaCl levels increased, average daily gain (ADG), average daily feed intake (ADFI), blood partial pressure of CO2, total CO2, base excess and anion gap, blood concentrations of HCO3, Na and Cl, serum Na concentration, jejunal villus height (VH) and tibia ash content increased linearly and quadratically (P < 0.05), while feed/gain ratio, relative weights of heart, liver and kidney, blood K concentration, serum concentrations of K, uric acid and glucose, and osmotic pressure decreased linearly and quadratically (P < 0.05). The estimates of optimal dietary NaCl levels were 0.20-0.22% based on the best fitted broken-line or asymptotic models (P < 0.0001) of ADG, ADFI and feed/gain ratio, and 0.08-0.24% based on the best fitted broken-line or asymptotic models (P < 0.0001) of blood gas indices, serum parameters, jejunal VH, tibia ash content and organ indices. These results suggested that the optimal dietary NaCl supplemental level would be 0.24% for broilers fed the corn-soybean meal diet from 1 to 21 days of age, which is lower than the current dietary NaCl supplemental level (0.30%) in the Chinese broiler production.

Influence of Venoarterial Extracorporeal Membrane Oxygenation Integrated Hemoadsorption on the Early Reversal of Multiorgan and Microcirculatory Dysfunction and Outcome of Refractory Cardiogenic Shock.

Background: The purpose of this investigation was to evaluate the impact of venoarterial extracorporeal membrane oxygenation (VA−ECMO) integrated hemoadsorption on the reversal of multiorgan and microcirculatory dysfunction, and early mortality of refractory cardiogenic shock patients. Methods: Propensity score−matched cohort study of 29 pairs of patients. Subjects received either VA−ECMO supplemented with hemoadsorption or standard VA−ECMO management. Results: There was a lower mean sequential organ failure assessment score (p = 0.04), lactate concentration (p = 0.015), P(v−a)CO2 gap (p < 0.001), vasoactive inotropic score (p = 0.007), and reduced delta C−reactive protein level (p = 0.005) in the hemoadsorption compared to control groups after 72 h. In−hospital mortality was similar to the predictions in the control group (62.1%) and was much lower than the predicted value in the hemoadsorption group (44.8%). There were less ECMO-associated bleeding complications in the hemoadsorption group compared to controls (p = 0.049). Overall, 90-day survival was better in the hemoadsorption group than in controls without statistical significance. Conclusion: VA−ECMO integrated hemoadsorption treatment was associated with accelerated recovery of multiorgan and microcirculatory dysfunction, mitigated inflammatory response, less bleeding complications, and lower risk for early mortality in comparison with controls.

Utility of arterial CO2 - End-tidal CO2 gap as a mortality indicator in the surgical ICU

BackgroundEnd-tidal CO2 (ETCO2) measurements have been an established tool for assessing critically ill patients. We aim to show that PaCO2-ETCO2 gap can be used as a predictor of mortality over a 7-day ICU stay. MethodsA retrospective chart review was performed on intubated surgical/trauma patients with documented ETCO2. We performed a univariate analysis and a receiver operating characteristic (ROC) curve. ResultsThirty-four patients were included. Patients who died were found to have longer days on vasopressors, and higher lactic acid levels on days 2–5, and 7. PaCO2-ETCO2 gap was higher on days 2–4 in those that died. Using ROC, days 2 and 4 PaCO2-ETCO2 gaps had good sensitivities, comparable to lactic acid sensitivity, in predicting mortality. ConclusionsPaCO2-ETCO2 gap was shown to be comparable to lactic acid in predicating mortality. Using this surrogate may aid to predict the clinical course in the ICU.

Cerebral and Systemic Stress Parameters in Correlation with Jugulo-Arterial CO2 Gap as a Marker of Cerebral Perfusion during Carotid Endarterectomy.

Intraoperative stress is common to patients undergoing carotid endarterectomy (CEA); thus, impaired oxygen and metabolic balance may appear. In this study, we aimed to identify new markers of intraoperative cerebral ischemia, with predictive value on postoperative complications during CEA, performed in regional anesthesia. A total of 54 patients with significant carotid stenosis were recruited and submitted to CEA. Jugular and arterial blood samples were taken four times during operation, to measure the jugulo-arterial carbon dioxide partial pressure difference (P(j-a)CO2), and cortisol, S100B, L-arginine, and lactate levels. A positive correlation was found between preoperative cortisol levels and all S100B concentrations. In addition, they are positively correlated with P(j-a)CO2 values. Conversely, postoperative cortisol inversely correlates with P(j-a)CO2 and postoperative S100B values. A negative correlation was observed between maximum systolic and pulse pressures and P(j-a)CO2 after carotid clamp and before the release of clamp. Our data suggest that preoperative cortisol, S100B, L-arginine reflect patients’ frailty, while these parameters postoperatively are influenced by intraoperative stress and injury. As a novelty, P(j-a)CO2 might be an emerging indicator of cerebral blood flow during CEA.

The Value of Combining Carbon Dioxide Gap and Oxygen-Derived Variables with Lactate Clearance in Predicting Mortality after Resuscitation of Septic Shock Patients.

Background Achieving hemodynamic stabilization does not prevent progressive tissue hypoperfusion and organ dysfunction during resuscitation of septic shock patients. Many indicators have been proposed to judge the optimization of oxygen delivery to meet tissue oxygen consumption. Methods A prospective observational study was conducted to evaluate and validate combining CO2 gap and oxygen-derived variables with lactate clearance during early hours of resuscitation of adults presenting with septic shock. Results Our study included 456 adults with a mean age of 63.2 ± 6.9 years, with 71.9% being males. Respiratory and urinary infections were the origin of about 75% of sepsis. Mortality occurred in 164 (35.9%) patients. The APACHE II score was 18.2 ± 3.7 versus 34.3 ± 6.8 (p < 0.001), the initial SOFA score was 5.8 ± 3.1 versus 7.3 ± 1.4 (p=0.001), while the SOFA score after 48 hours was 4.2 ± 1.8 versus 9.4 ± 3.1 (p < 0.001) in the survivors and nonsurvivors, respectively. Hospital mortality was independently predicted by hyperlactatemia (OR: 2.47; 95% CI: 1.63–6.82, p=0.004), PvaCO2 gap (OR: 2.62; 95% CI: 1.28–6.74, p=0.026), PvaCO2/CavO2 ratio (OR: 2.16; 95% CI: 1.49–5.74, p=0.006), and increased SOFA score after 48 hours of admission (OR: 1.86; 95% CI: 1.36–8.13, p=0.02). A blood lactate cutoff of 40 mg/dl at the 6th hour of resuscitation (T6) had a 92.7% sensitivity and 75.3% specificity for predicting hospital mortality (AUROC = 0.902) with 81.6% accuracy. Combining the lactate cutoff of 40 mg/dl and PvaCO2/CavO2 ratio cutoff of 1.4 increased the specificity to 93.2% with a sensitivity of 75.6% in predicting mortality and with 86.8% accuracy. Combining the lactate cutoff of 40 mg/dl and PvaCO2 gap of 6 mmHg increased the sensitivity to 93% and increased the specificity to 98% in predicting mortality with 91% accuracy. Conclusion Combining the carbon dioxide gap and arteriovenous oxygen difference with lactate clearance during early hours of resuscitation of septic shock patients helps to predict hospital mortality more accurately.

End-tidal to arterial carbon dioxide gradient is associated with increased mortality in patients with traumatic brain injury: a retrospective observational study

Early definitive airway protection and normoventilation are key principles in the treatment of severe traumatic brain injury. These are currently guided by end tidal CO2 as a proxy for PaCO2. We assessed whether the difference between end tidal CO2 and PaCO2 at hospital admission is associated with in-hospital mortality. We conducted a retrospective observational cohort study of consecutive patients with traumatic brain injury who were intubated and transported by Helicopter Emergency Medical Services to a Level 1 trauma center between January 2014 and December 2019. We assessed the association between the CO2 gap—defined as the difference between end tidal CO2 and PaCO2—and in-hospital mortality using multivariate logistic regression models. 105 patients were included in this study. The mean ± SD CO2 gap at admission was 1.64 ± 1.09 kPa and significantly greater in non-survivors than survivors (2.26 ± 1.30 kPa vs. 1.42 ± 0.92 kPa, p < .001). The correlation between EtCO2 and PaCO2 at admission was low (Pearson's r = .287). The mean CO2 gap after 24 h was only 0.64 ± 0.82 kPa, and no longer significantly different between non-survivors and survivors. The multivariate logistic regression model showed that the CO2 gap was independently associated with increased mortality in this cohort and associated with a 2.7-fold increased mortality for every 1 kPa increase in the CO2 gap (OR 2.692, 95% CI 1.293 to 5.646, p = .009). This study demonstrates that the difference between EtCO2 and PaCO2 is significantly associated with in-hospital mortality in patients with traumatic brain injury. EtCO2 was significantly lower than PaCO2, making it an unreliable proxy for PaCO2 when aiming for normocapnic ventilation. The CO2 gap can lead to iatrogenic hypoventilation when normocapnic ventilation is aimed and might thereby increase in-hospital mortality.

Clinical assessment of acid-base balance in Netherland Dwarf rabbit.

Pet rabbits have increased their popularity in a lot of countries. However, most of the laboratory profiles in rabbit medicine come from the observations made in rabbit as biomodels or meat production. So that further researches are necessary to obtain reference values for hematology and biochemical profiles in pet rabbits and the different breeds, especially, in relation to acid-base balance. The aim of this report was to offer the mean values of the main parameters connected with acid-base profile in Netherland Dwarf breed. Thirty-five healthy rabbits (15 males and 20 females) were studied. Venous blood sample from lateral saphenous vein was analyzed to measure: haematocrit, haemoglobin, blood urea nitrogen, glucose, blood pH, partial pressure of CO2 (pCO2), total CO2, ions bicarbonate, chloride, sodium, potassium, base excess and anion Gap. Results showed a shorter range that those reported by different researchers. Moreover, differences between genders were showed in pCO2, its values were higher in males. It may be associated with a greater cellular metabolism. Values obtained in this research should be taken into account by veterinary clinicians for this breed in their clinical assessments. Besides, these values provide new results in parameters with few reference values.

High venous to arterial CO2 gap is related to cardiovascular death in cardiogenic shock

Abstract Funding Acknowledgements Type of funding sources: None. Background Venous to arterial CO2 gap (CO2gap) is calculated by subtracting partial pressure of arterial CO2 to central venous partial pressure of CO2 (ScvCO2). This marker has been studied in septic shock and indicates hypoperfusion when exceeds 6mmHg. Its kinetics and applicability in cardiogenic shock (CS) are unclear, being mixed/central venous saturation and lactate more commonly used. Purpose The objective of the study is to describe CO2gap kinetics in patients with CS. Secondary objective is to analyze if CO2gap is as marker of prognosis in CS. Methods Prospective observational study that included patients admitted for CS in the Acute Cardiovascular Care Unit of a tertiary hospital. Gasometric samples were obtained at admission, 6, 12, 24 and 48 hours from the onset of shock. In-hospital mortality was registered. Results We included 40 patients with CS during 1 year. Most patients were male (80%), average age was 68 years. There was a high incidence of cardiac arrest (58%), most frequent cause of CS was STEMI (45%), in-hospital mortality was 45%, most cases from non-cardiovascular causes (61%). Refractory shock was frequent (28%). Average lactate peak was 6.02 mmol / L. CO2gap kinetics consisted in a peak at admission (8.8mmHg), a valley 6h (7.7mmHg), new peak at 12h (8.5mmHg) and progressive decrease at at 24 (6.8mmHg) and 48h (5.7 mmHg). Significantly, higher CO2gap values at admission (10.97mmHg vs 8.16mmHg, p = 0.007) was predictor of cardiovascular mortality. Lactate values at 6, 12 and 48 hours were also predictors of cardiovascular mortality, as well as ScvO2 at admission. Conclusions Patients with CS present with high CO2gap values during first hours of admission. The kinetics of this marker consists in two peaks at admission and 12 hours from CS onset, a valley at 6 hours and a progressive decrease at 24 and 48 hours. Its determination at admission is associated with cardiovascular mortality. We suggest the potential benefit of combining this marker, along with lactate and ScvO2 values, to guide management of patients with CS. Abstract Figure. CO2 gap and cardiovascular mortality

Central venous-to-arterial CO2 difference is a poor tool to predict adverse outcomes after cardiac surgery: a retrospective study.

PurposeThe venous-to-arterial carbon dioxide partial pressure difference (CO2 gap) has been reported to be a sensitive indicator of cardiac output adequacy. We aimed to assess whether the CO2 gap can predict postoperative adverse outcomes after cardiac surgery.MethodsA retrospective study was conducted of 5,151 patients from our departmental database who underwent cardiac surgery from 1 January 2008 to 31 December 2018. Lactate level (mmol·L−1), central venous oxygen saturation (ScVO2) (%), and the venous-to-arterial carbon dioxide difference (CO2 gap) were measured at intensive care unit (ICU) admission and on days 1 and 2 after cardiac surgery. The following postoperative adverse outcomes were collected: ICU mortality, hemopericardium or tamponade, resuscitated cardiac arrest, acute kidney injury, major bleeding, acute hepatic failure, mesenteric ischemia, and pneumonia. The primary outcome was the presence of at least one postoperative adverse outcome. Logistic regression was used to assess the association between ScVO2, lactate, and the CO2 gap with adverse outcomes. Their diagnostic performance was compared using a receiver operating characteristic (ROC) curve.ResultsThere were 1,933 patients (38%) with an adverse outcome. Cardiopulmonary bypass (CPB) parameters were similar between groups. The CO2 gap was slightly higher for the “adverse outcomes” group than for the “no adverse outcomes” group. Arterial lactate at admission, day 1, and day 2 was also slightly higher in patients with adverse outcomes. Central venous oxygen saturation was not significantly different between patients with and without adverse outcomes. The area under the ROC curve to predict outcomes after CPB for the CO2 gap at admission, day 1, and day 2 were 0.52, 0.55, and 0.53, respectively.ConclusionAfter cardiac surgery with CPB, the CO2 gap at ICU admission, day 1, and day 2 was associated with postoperative adverse outcomes but showed poor diagnostic performance.

The Impact of Early Goal Directed Therapy and PCO2 Gap Protocol on Outcomes of High-Risk Surgical Patients Admitted to ICU: A Prospective Study

Objectives: High risk surgical patients are prone to experience complicated outcomes that directly lead to longer days on ventilators and consequently longer ICU and hospital stay. PCO2 gap has elicited an increasing interest in directing resuscitation towards optimizing CO2 gap. Thus, we aimed to compare the impact of PCO2 gap targeting protocol to a classical Goal Directed Therapy Protocol (GDT) on ICU stay Ventilator day and length of hospital stay, in high-risk surgical patients admitted to ICU. Design: Blinded prospective randomized clinical trial. Settings: Qena University Hospital. Patients: 80 patients who have high risk surgical criteria adopted from Shoemacker et al score and were admitted to ICU postoperatively, were divided into two groups: in group (A) PCO2 gap algorithm was applied 12 h postoperative with end point PCO2 gap 2-6 mm Hg ,and in group (B) goal directed therapy protocolwas applied 12 postoperative targeting endpoints: MAP >65mmHg, CVP between 8-12 cmH2O, Haematocrite value more than 30, SvO2 >75% and urine output more than >0.5 ml/kg/hr. Measurements and results: Regarding duration of ventilator dependency, ICU stay and hospital stay, all values were lower in group a compared to group B although it was statistically insignificant. Conclusion: In high risk surgical patients in ICU, targeting PCO2 values has no significant difference to early goal directed therapy regarding the decrease in ventilation days, ICU stay or hospital stay.

Diabetic ketoacidosis in patients treated with SGLT2 inhibitors: experience at a tertiary hospital.

Diabetic ketoacidosis (DKA) is a rare and life-threatening complication in patients with diabetes. Sodium-glucose co-transporter-2 inhibitors (SGLT2i) have rarely been associated with ketoacidosis. The aim of this retrospective study was to investigate DKA episodes occurring after SGLT2i treatment and to compare them to DKA episodes due to other causes. The medical records of the years 2018-2020 related to clinical and biochemical characteristics and to treatment of six patients with DKA due to SGLT2i were reviewed. They were compared to those of 12 patients with DKA due to other causes. On admission, the most common symptom was abdominal pain. Glucose levels (median, min-max) were lower in patients with SGLT2i-induced DKA compared to those with DKA due to other causes (229 (150-481) vs. 458.5 (332-695) mg/dl, p = 0.007), whereas no statistical difference was observed in HbA1c and in the severity of DKA (pH, HCO3, CO2, and anion gap). The duration of insulin infusion (41 (33-124) vs. 21.50 (11-32) h, p < 0.001) and the time required until DKA resolution (39 (31-120) vs. 19 (9-28) h, p < 0.001) were higher in patients with SGLT2i-induced DKA than those with DKA due to other causes. In addition, there were increased fluid requirements (14 (8-22.75) vs. 5.5 (2-24) L, p = 0.013) and longer hospitalization time (11 (6-22) vs. 5.5 (2-14) days, p = 0.024) in patients with SGLT2i-induced DKA. No statistically significant differences were observed in total intravenous insulin and potassium administration until DKA resolution. Patients with SGLT2i-induced DKA had lower serum glucose levels on admission and required increased fluid administration and longer time to recover from acidosis compared to patients with DKA from other causes.

How to narrow the CO2 gap from growth-optimal to flue gas levels by using microalgae for carbon capture and sustainable biomass production

Microalgae can serve as a ‘green bio-cleanser’ for carbon mitigation and simultaneous production of sustainable biomass, especially when using the flue gas as a carbon-rich source. However, there is a CO2 gap from the growth-optimal (2–6%) to the flue gas (10–25%) levels. To narrow this gap, several gas manipulation strategies have been tested in this study, including constant elevated CO2 levels, O2 removal, gradual increases in CO2 concentration, and pH control by adjusting the CO2 dosing. Results show that the growth of Dunaliella salina could be enhanced by increasing CO2 from the ambient level to 6% (in air) but was significantly inhibited by the further increase to 20% CO2 (in air). The CO2 fixation capacity at 20% CO2 in air could be improved by 2.7-fold via O2 removal from the inlet gas, which could be further improved by 2.5-fold through gradual increases in CO2 concentration, reaching an overall enhancement of 6.6-fold. Extremely high CO2 concentration of 100% completely inhibited the growth, but the negative effect could be recovered by timely switch to air-aeration. Growth inhibition by excess CO2 was associated with the medium acidification and pigment reduction, accompanied by a decrease of carbohydrates and slight lipid accumulation. When using the flue gas as a carbon source, pH control by adjusting the CO2 dosing is important to avoid dramatic changes in both dissolved inorganic carbon and pH.

The Use of Central Venous to Arterial Carbon Dioxide Tension Gap for Outcome Prediction in Critically Ill Patients: A Systematic Review and Meta-Analysis.

In this systematic review and meta-analysis, we assessed whether a high CO2 gap predicts mortality in adult critically ill patients with circulatory shock. A systematic search of MEDLINE and EMBASE electronic databases from inception to October 2019. Studies from adult (age ≥ 18 yr) ICU patients with shock reporting CO2 gap and outcomes of interest. Case reports and conference abstracts were excluded. Data extraction and study quality assessment were performed independently in duplicate. We used the Newcastle-Ottawa Scale to assess methodological study quality. Effect sizes were pooled using a random-effects model. The primary outcome was mortality (28 d and hospital). Secondary outcomes were ICU length of stay, hospital length of stay, duration of mechanical ventilation, use of renal replacement therapy, use of vasopressors and inotropes, and association with cardiac index, lactate, and central venous oxygen saturation. We included 21 studies (n = 2,155 patients) from medical (n = 925), cardiovascular (n = 685), surgical (n = 483), and mixed (n = 62) ICUs. A high CO2 gap was associated with increased mortality (odds ratio, 2.22; 95% CI, 1.30-3.82; p = 0.004) in patients with shock, but only those from medical and surgical ICUs. A high CO2 gap was associated with higher lactate levels (mean difference 0.44 mmol/L; 95% CI, 0.20-0.68 mmol/L; p = 0.0004), lower cardiac index (mean difference, -0.76 L/min/m; 95% CI, -1.04 to -0.49 L/min/m; p = 0.00001), and central venous oxygen saturation (mean difference, -5.07; 95% CI, -7.78 to -2.37; p = 0.0002). A high CO2 gap was not associated with longer ICU or hospital length of stays, requirement for renal replacement therapy, longer duration of mechanical ventilation, or higher vasopressors and inotropes use. Future studies should evaluate whether resuscitation aimed at closing the CO2 gap improves mortality in shock.

Elevated Venous to Arterial Carbon Dioxide Gap and Anion Gap Are Associated with Poor Outcome in Cardiogenic Shock Requiring Extracorporeal Membrane Oxygenation Support

Optimal management of cardiogenic shock requiring extracorporeal membrane oxygenation (ECMO) is still an evolving area in which assessment and optimization of the microcirculation may be critically important. We hypothesized that the venous arterial carbon dioxide gap (P(v-a)CO2 gap); the ratio of this gap to arterio-venous oxygen content (P(v-a)CO2/C(a-v)O2 ratio) and the anion gap would be early indicators of microcirculatory status and useful parameters for outcome prediction during ECMO support. We retrospectively reviewed 31 cardiogenic shock patients requiring veno-arterial ECMO, calculating P(v-a)CO2 gap and P(v-a)CO2/C(a-v)O2 ratios in the first 36 hours and the final 24 hours of ECMO support. Sixteen patients (52%) survived and 15 (48%) died. After 24 hours of ECMO support, the P(v-a)CO2 gap (4.9 ± 1.5 vs. 6.8 ± 1.9 mm Hg; p = 0.004) and anion gap (5.2 ± 1.8 vs. 8.7 ± 2.7 mmol/L; p < 0.001) were significantly higher in non-survivors. In the final 24 hours of ECMO support, the P(v-a)CO2 gap (3.5 ± 1.6 vs. 10.5 ± 3.2 mm Hg; p < 0.001), P(v-a)CO2/C(a-v)O2 ratio (1.1 ± 0.5 vs. 2.7 ± 1.0; p < 0.001), anion gap (5.1 ± 3.0 vs. 9.3 ± 5.9 mmol/L; p = 0.02), and lactate (median 1.0 [interquartile range {IQR}: 0.7-1.5] vs. 2.8 [IQR: 1.7-7.7] mmol/L; p = <0.001) were all significantly lower in survivors. Increasing P(v-a)CO2 gap and increasing anion gap were significantly associated with increased risk of mortality. Optimum cut-points for prediction of mortality were 6 mm Hg for P(v-a)CO2 gap in combination with an anion gap above 6 mmol/L in the first 24 hours of ECMO in patients with cardiogenic shock requiring ECMO.

Influence of Medications Containing Acid Salts on Serum Bicarbonate in CKD

Many medications are formulated with acid salts. Their effect on acid-base balance in CKD is unclear. We calculated the acid load (meq/d) from medications prescribed to 74 United States veterans with diabetes and CKD to identify agents with high potential acid load. We also determined cross-sectional associations between the acid load from medications and acid-base parameters after adjusting for demographics, eGFR, protein intake, and other confounders. Of the 125 medications prescribed, 31 (25%) contained an acid salt. Metformin hydrochloride (15.4 meq/d at 2550 mg/d) and gabapentin hydrochloride (13.0 meq/d at 2700 mg/d) were identified as agents with a high potential acid load. Mean daily acid load from medications was 6.6 meq/d in the overall cohort, 14.2 meq/d in the high medication acid load group (≥7.7 meq/d, n=29), and 1.6 meq/d in the low medication acid load group (<7.7 meq/d, n=45). After adjusting for potential confounders, those in the high acid load group had 1.7 meq/L lower total carbon dioxide (CO2) and 2.2 meq/L higher anion gap than those in the low acid load group. Use of gabapentin alone was not associated with differences in total CO2 or anion gap. Use of metformin alone was associated with 0.7 meq/L lower total CO2 and 1.0 meq/L higher anion gap. Use of metformin with gabapentin was associated with 1.8 meq/L lower total CO2 and 2.4 meq/L higher anion gap. The higher anion gap was not explained by higher serum lactate levels. The acid load from medications was not associated with differences in urinary ammonium, titratable acid, or pH. Medications containing acid salts, particularly metformin hydrochloride and gabapentin hydrochloride, are sources of an exogenous acid load. These agents may influence serum total CO2 levels and serum anion gap in individuals with CKD. Investigations of the Optimum Serum Bicarbonate Level in Renal Disease, NCT01574157.