Prediction of arterial blood gas values from venous blood gas values in patients with acute exacerbation of chronic obstructive pulmonary disease

Arterial blood gas analysis or venous blood gas analysis for adult hospitalised patients with respiratory presentations: a systematic review

BACKGROUND

Identification of hypoxaemia and hypercapnia is essential for the diagnosis and treatment of acute respiratory failure. While arterial blood gas (ABG) analysis is standard for PO2 and PCO2 measurement, venous blood gas (VBG) analysis is increasingly used as an alternative. Previous systematic reviews established that VBG reporting of PO2 and PCO2 is less accurate, but the impacts on clinical management and patient outcomes are unknown.

AIMS

This study aimed to systematically review available evidence of the clinical impacts of using ABGs or VBGs and examine the arteriovenous difference in blood gas parameters.

METHODS

A comprehensive search of the MEDLINE, Embase and Cochrane Library databases since inception was conducted. Included studies were prospective or cross-sectional studies comparing peripheral ABG to peripheral VBG in adult non-critical care inpatients presenting with respiratory symptoms.

RESULTS

Of 15 119 articles screened, 15 were included. No studies were found that examined clinical impacts resulting from using VBG compared to ABG. Included studies focused on the agreement between ABG and VBG measurements of pH, PO2, PCO2 and HCO3 -. Due to the heterogeneity of the included studies, qualitative evidence synthesis was performed. While the arteriovenous difference in pH and HCO3 - was generally predictable, the difference in PO2 and PCO2 was more significant and less predictable.

CONCLUSIONS

Our study reinforces the notion that VBG is not comparable to ABG for physiological measurements. However, a key revelation from our research is the significant lack of data regarding the clinical implications of using VBG instead of ABG, a common scenario in clinical practice. This highlights a critical knowledge gap.

Midline catheters for blood gas and acid/base monitoring in critical patients: A prospective observational study

BACKGROUND

Arterial lines and central venous catheter (CVC) allow to monitor patients' acid-base status and gas exchange. Their placement and maintenance may however be burdened by severe complications. Midline Catheters (MC) are peripheral venous accesses that are less invasive and easier to insert compared to CVC and arterial lines.

METHODS

A prospective observational study was performed including stabilized critical patients with clinical indication to midline positioning before intensive care unit (ICU) discharge. The primary aim was to assess if venous sampling from MCs can be a reliable alternative to CVC for pH and CO2 monitoring. The secondary aim was to evaluate the correlation between samplings from MC, CVC and arterial line with regards to pH, carbon dioxide tension (pCO2), lactates and electrolytes. Three samples from CVC, arterial line and MC were collected simultaneously. Agreement and correlation of the studied parameters between different sampling sites were explored.

RESULTS

40 patients were included in the analysis. A good agreement for pH and pCO2 was recorded between MC and CVC: mean differences were 0.001 (95% CI -0.006 to 0.007) and 0.7 (-0.1 to 1.5), percentage error 0.4% and 11.2%, respectively. Correlation between MC and both central venous and arterial samples for pH, pCO2, lactates and electrolytes was found to be moderate-to-strong (Pearson's R coefficient range 0.59-0.99, p < 0.001 for all these parameters).

CONCLUSIONS

In stabilized critical patients, midline catheters represent a reliable alternative to CVC and arterial lines to monitor acid-base disturbances, CO2 levels and electrolytes. The present findings add to the known advantages of MC, which might be considered a first-line vascular access for non-critical or stabilized patients who do not require infusion of vesicant or irritant drugs.

Venous blood gases in the assessment of respiratory failure in patients undergoing sleep studies: a randomized study

STUDY OBJECTIVES

Venous blood gases (VBGs) are not consistently considered suitable surrogates for arterial blood gases (ABGs) in assessing acute respiratory failure due to variable measurement error. The physiological stability of patients with chronic ventilatory failure may lead to improved agreement in this setting.

METHODS

Adults requiring ABGs for sleep or ventilation titration studies had VBGs drawn before or after each ABG, in a randomized order. Veno-arterial correlation and agreement were examined for carbon dioxide tension (PCO2), pH, oxygen tension (PO2), and oxygen saturation (SO2).

RESULTS

We analyzed 115 VBG-ABG pairs from 61 patients. Arterial and venous measures were correlated (P < .05) for PCO2 (r = .84) and pH (r = .72), but not for PO2 or SO2. Adjusted mean veno-arterial differences (95% limits of agreement) were +5.0 mmHg (-4.4 to +14.4) for PCO2; -0.02 (-0.09 to +0.04) for pH; -34.3 mmHg (-78.5 to +10.0) for PO2; and -23.9% (-61.3 to +13.5) for SO2. VBGs obtained from the dorsal hand demonstrated a lower mean PCO2 veno-arterial difference (P < .01). A venous PCO2 threshold of ≥ 45.8 mmHg was > 95% sensitive for arterial hypercapnia, so measurements below this can exclude the diagnosis without an ABG. A venous PCO2 threshold of ≥ 53.7 mmHg was > 95% specific for arterial hypercapnia, so such readings can be assumed diagnostic. The area under the receiver operating characteristic curve of 0.91 indicated high discriminatory capacity.

CONCLUSIONS

A venous PCO2 < 45.8 mmHg or ≥ 53.7 mmHg would exclude or diagnose hypercapnia, respectively, in patients referred for sleep studies, but VBGs are poor surrogates for ABGs where precision is important.

CLINICAL TRIAL REGISTRATION

Registry: Australian New Zealand Clinical Trials Register; Name: A comparison of arterial and blood gas analyses in sleep studies; URL: https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=372717; Identifier: ACTRN12617000562370.

CITATION

Lindstrom SJ, McDonald CF, Howard ME, et al. Venous blood gases in the assessment of respiratory failure in patients undergoing sleep studies: a randomized study. J Clin Sleep Med. 2024;20(8):1259-1266.

Respiratory Acid-Base Disorders

Respiratory acid-base disorders are often not thought of as frequently as their metabolic cousins, which occur more frequently in the emergency department. Although most respiratory and acid-base disturbances are driven by lung pathology, central nervous system and other organ systems can and do play a role as well. Although managing the airway and appropriate mechanical ventilation may be necessary, it is akin to placing a band-aid on a large wound. It is crucial for the emergency clinician to discover the etiology of the disturbance as management depends on treating the underlying etiology to prevent worsening acid-base status.

Arterial Versus Venous Blood Gas Analysis Comparisons, Appropriateness, and Alternatives in Different Acid/Base Clinical Settings: A Systematic Review

Arterial blood gases (ABGs) are routinely done in critical clinical settings to ascertain acid-base status. Due to difficulties and the potential side effects following arterial blood sampling, much research has been done to find the possibility of using venous samples as an alternative. However, this comparison needs to be evaluated in various contexts. Hence, this systematic review aims to explore the differences, appropriateness, and alternatives of arterial versus venous blood gas (VBG) analysis in different acid-base states. A comprehensive literature search was conducted through electronic databases using the terms "ABG," "VBG," "Arterial Blood Gas," "Venous Blood Gas," and "Gas analysis." Studies' qualities were assessed by using Newcastle - Ottawa Quality Assessment Scale. Of 531 articles, 22 were included in the study after title, abstract, and full-text screening. Based on the Newcastle - Ottawa Quality Assessment Scale, 23% of the studies had good quality (score ≥ 7), 77% fair quality (score 2-6), and none of the studies had poor quality (score ≤ 1). Moreover, 22.5% of the included articles found a strong correlation between ABG and VBG. 73% compared arterial and VBG parameters among patients with any clinical contexts, 22.5% in respiratory diseases, and 4.5% in metabolic conditions, and their results had a significant disparity. There was a considerable discrepancy among authors about the appropriateness and utilization of VBG as an alternative to ABG. Our findings suggest that those studies did not consider physiological differences between venous and arterial blood values and obviated the significance of sampling procedures.

Diagnostic Accuracy of Optic Nerve Sheath Diameter Measured With Ocular Ultrasonography in Acute Attack of Chronic Obstructive Pulmonary Disease

OBJECTIVE

The study aimed to evaluate intracranial pressure changes by measuring ONSD before and after treatment in patients with chronic obstructive pulmonary disease (COPD).

METHODS

The study was designed as a prospective analysis, in which 56 COPD in acute exacerbation and 50 volunteers. COPD severity was determined by the Dyspnea Scale of Modified Medical Research Council (mMRC). Measurements were made with ocular ultrasonography and linear probe in both eyes.

RESULTS

Both the right and left ONSDs were higher in the patient compared to the control (P = .017) and regressed after the treatment (P = .021). In the ROC analysis for the predictability of COPD, right eye ONSDs showed a predictive potential for COPD with %75.7 specificity and %68.1 sensitivity at 0.455 cut-off (AUC: 0.727; P = .0001; %95CI: 0.609-0.833). Similar to the right eye, the left ONSD presented %74.4 specificity and %67 sensitivity at 0.505 cut-off value (AUC: 0.718; P = .0001; %95CI: 0.608-0.841).

CONCLUSION

The ONSD measurement that was with the help of ocular ultrasonography can be a useful diagnostic tool for symptomatic COPD presenting with an acute attack.

The association of admission ionized calcium with outcomes of thrombolysed patients with anterior circulation ischemic stroke

BACKGROUND AND PURPOSE

The relationship between ionized calcium and prognosis of ischemic stroke is controversial. We aim to determine the relationship of admission ionized calcium levels with acute ischemic stroke (AIS) after intravenous thrombolysis (IVT).

METHODS

Consecutive anterior circulation AIS patients treated with recombinant tissue plasminogen activator (rt-PA) were retrospectively enrolled. According to ionized calcium quartiles, the patients were divided into four groups and clinical data were analyzed between groups. Ionized calcium was entered into logistic regression analysis in two models, separately: model 1, calcium as a continuous variable (per 1-mmol/L increase), and model 2, calcium as the four-categorized variable (being collapsed into quartiles: Q1-Q4). Early neurologic improvement (ENI) was defined as improvement of four or more points at 24 h after intravenous rt-PA, while long-term good outcome as the modified Rankin Scale (mRS) 0-1 at 90 days.

RESULTS

A total of 546 patients met the study criteria (mean age was 63.51 ± 11.26 years and 365 [66.8%] were men). The median admission National Institute of Health Stroke Scale was 9 (range 4 to 15). When not adjusted, in model 1: ionized calcium was related to good outcome (odds ratio [OR] 69.061, 95%CI: 1.638-2911.111, p=0.027), but not ENI (OR 14.097, 95%CI: 0.133-1492.596, p=0.266); in model 2: compared with Q4, while good outcome was less common in Q1 (OR 0.623, 95%CI: 0.388-0.999, p=0.049). After adjusting for confounding factors, calcium in Q2 (OR 0.502, 95%CI: 0.253-0.997, p=0.049) was independently associated with ENI, but no matter as a continuous variable or categorized variable, ionized calcium displayed no association with a good outcome.

CONCLUSION

The current results found that ionized calcium might be associated with early neurological improvement, but had no association with 3 months' outcome in anterior circulation AIS patients after IVT.

Pandemic coronavirus disease (Covid-19): World effects analysis and prediction using machine-learning techniques

Pandemic novel Coronavirus (Covid-19) is an infectious disease that primarily spreads by droplets of nose discharge when sneezing and saliva from the mouth when coughing, that had first been reported in Wuhan, China in December 2019. Covid-19 became a global pandemic, which led to a harmful impact on the world. Many predictive models of Covid-19 are being proposed by academic researchers around the world to take the foremost decisions and enforce the appropriate control measures. Due to the lack of accurate Covid-19 records and uncertainty, the standard techniques are being failed to correctly predict the epidemic global effects. To address this issue, we present an Artificial Intelligence (AI)-based meta-analysis to predict the trend of epidemic Covid-19 over the world. The powerful machine learning algorithms namely Naïve Bayes, Support Vector Machine (SVM) and Linear Regression were applied on real time-series dataset, which holds the global record of confirmed, recovered, deaths and active cases of Covid-19 outbreak. Statistical analysis has also been conducted to present various facts regarding Covid-19 observed symptoms, a list of Top-20 Coronavirus affected countries and a number of coactive cases over the world. Among the three machine learning techniques investigated, Naïve Bayes produced promising results to predict Covid-19 future trends with less Mean Absolute Error (MAE) and Mean Squared Error (MSE). The less value of MAE and MSE strongly represent the effectiveness of the Naïve Bayes regression technique. Although, the global footprint of this pandemic is still uncertain. This study demonstrates the various trends and future growth of the global pandemic for a proactive response from the citizens and governments of countries. This paper sets the initial benchmark to demonstrate the capability of machine learning for outbreak prediction.

Correlation of Arterial and Venous pH and Bicarbonate in Patients With Renal Failure

Background and objective

Blood gas analysis plays a pivotal role in the management of various respiratory and metabolic disorders. Both arterial and venous samples can be used for blood gas analysis. Arterial blood sampling is technically difficult and is associated with more complications as compared to venous sampling. Many studies have shown the correlation of arterial and venous pH and bicarbonate levels in sepsis, diabetic ketoacidosis (DKA), chronic obstructive pulmonary disease (COPD), and circulatory failure. But, there is a paucity of data, pertaining specifically to the correlation of arterial blood gas (ABG) analysis and venous blood gas (VBG) analysis in patients with renal failure. The objective of this study was to look for any possible correlation between arterial and venous pH and bicarbonate values in patients with renal failure.

Methods

This cross-sectional study was carried out at a large tertiary care hospital in Rawalpindi, Pakistan. Over a period of eight months, 101 patients with renal failure were enrolled after obtaining informed consent. Arterial and venous samples from the patients were obtained, analyzed, and compared.

Results

Out of the total 101 patients, 53 (52.5%) were male while 48 (47.5%) were female. The mean age of the patients was 46.23 ±15.54 years. Mean arterial pH and venous pH were 7.35 and 7.28 respectively. The Pearson correlation coefficient between arterial and venous pH was found to be 0.857 (p<0.001). The mean arterial and venous bicarbonate values were 14.47 mEq/L and 15.51 mEq/L respectively. And the Pearson correlation coefficient between arterial and venous bicarbonate was found to be 0.842 (p<0.001). 

Conclusion

Venous pH and bicarbonate levels correlate strongly with arterial pH and bicarbonate levels, respectively, in patients with renal failure.

German S3 Guideline: Oxygen Therapy in the Acute Care of Adult Patients

BACKGROUND

Oxygen (O2) is a drug with specific biochemical and physiological properties, a range of effective doses and may have side effects. In 2015, 14% of over 55,000 hospital patients in the UK were using oxygen. 42% of patients received this supplemental oxygen without a valid prescription. Health care professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

A national S3 guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. A literature search was performed until February 1, 2021, to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for assessing the quality of evidence and for grading guideline recommendation, and a formal consensus-building process was performed.

RESULTS

The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O2 therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are based depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

This is the first national guideline on the use of oxygen in acute care. It addresses health care professionals using oxygen in acute out-of-hospital and in-hospital settings.

[German S3 Guideline - Oxygen Therapy in the Acute Care of Adult Patients]

BACKGROUND

 Oxygen (O₂) is a drug with specific biochemical and physiologic properties, a range of effective doses and may have side effects. In 2015, 14 % of over 55 000 hospital patients in the UK were using oxygen. 42 % of patients received this supplemental oxygen without a valid prescription. Healthcare professionals are frequently uncertain about the relevance of hypoxemia and have low awareness about the risks of hyperoxemia. Numerous randomized controlled trials about targets of oxygen therapy have been published in recent years. A national guideline is urgently needed.

METHODS

 A S3-guideline was developed and published within the Program for National Disease Management Guidelines (AWMF) with participation of 10 medical associations. Literature search was performed until Feb 1st 2021 to answer 10 key questions. The Oxford Centre for Evidence-Based Medicine (CEBM) System ("The Oxford 2011 Levels of Evidence") was used to classify types of studies in terms of validity. Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used and for assessing the quality of evidence and for grading guideline recommendation and a formal consensus-building process was performed.

RESULTS

 The guideline includes 34 evidence-based recommendations about indications, prescription, monitoring and discontinuation of oxygen therapy in acute care. The main indication for O₂ therapy is hypoxemia. In acute care both hypoxemia and hyperoxemia should be avoided. Hyperoxemia also seems to be associated with increased mortality, especially in patients with hypercapnia. The guideline provides recommended target oxygen saturation for acute medicine without differentiating between diagnoses. Target ranges for oxygen saturation are depending on ventilation status risk for hypercapnia. The guideline provides an overview of available oxygen delivery systems and includes recommendations for their selection based on patient safety and comfort.

CONCLUSION

 This is the first national guideline on the use of oxygen in acute care. It addresses healthcare professionals using oxygen in acute out-of-hospital and in-hospital settings. The guideline will be valid for 3 years until June 30, 2024.

Comparing Central Venous Blood Gas to Arterial Blood Gas and Determining Its Utility in Critically Ill Patients: Narrative Review

Arterial blood gas (ABG) analysis is used in critical care units to determine the degree of oxygenation, adequacy of ventilation, and the presence and severity of acid-base disturbances in the body. However, arterial puncture may result in complications, and the difficulty in acquiring arterial blood may delay care. Central venous blood gas (VBG) is a potentially more accessible alternative to ABG sampling. Current evidence suggests that pH and Pco2 obtained via peripheral VBG correlate well with ABG measurement. Nevertheless, the value of using central VBG to guide clinical decisions or as a surrogate for ABG is unclear. The purpose of this review is to explore the relationship between ABGs and central VBGs in critically ill patients. We performed a MEDLINE search using the following search terms: venous blood gas, arterial blood gas, and central venous blood gas. We excluded studies that did not involve human subjects, and only pH and Pco2 values were reviewed and examined from the studies included. All cited references from included studies were also reviewed to identify relevant literature. We identified 7 studies that met our criteria. In studies of hemodynamically stable patients, the mean difference between arterial and central venous pH and Pco2 was 0.03 units and 4-6.5 mm Hg, respectively. However, in patients with circulatory failure, the difference between central venous and arterial pH/Pco2 was 4-fold greater. We concluded that central VBG parameters of pH and Pco2 are potentially good surrogates for determining arterial pH and Pco2 in a stable patient without severe acid-base disturbances. Furthermore, central VBG can be used as a useful screening tool for arterial hypercapnia. In addition, we derived an adjustment formula for ABG conversion from central VBG: (1) arterial pH = venous pH + 0.05 units and (2) arterial Pco2 = venous Pco2 - 5 mm Hg.

Reference intervals for venous blood gas measurement in adults

OBJECTIVES

Venous blood gas (VBG) analysis is becoming a popular alternative to arterial blood gas (ABG) analysis due to reduced risk of complications at phlebotomy and ease of draw. In lack of published data, this study aimed to establish reference intervals (RI) for correct interpretation of VBG results.

METHODS

One hundred and 51 adult volunteers (101 females, 50 males, 18-70 years) were enrolled after completion of a health questionnaire. Venous blood was drawn into safePICO syringes and analysed on ABL827 blood gas analyser (Radiometer Pacific Pty. Ltd.). A non-parametric approach was used to directly establish the VBG RI which was compared to a calculated VBG RI based on a meta-analysis of differences between ABG and VBG.

RESULTS

After exclusions, 134 results were used to derive VBG RI: pH 7.30-7.43, partial pressure of carbon dioxide (pCO₂) 38-58 mmHg, partial pressure of oxygen (pO₂) 19-65 mmHg, bicarbonate (HCO₃-) 22-30 mmol/L, sodium 135-143 mmol/L, potassium 3.6-4.5 mmol/L, chloride 101-110 mmol/L, ionised calcium 1.14-1.29 mmol/L, lactate 0.4-2.2 mmol/L, base excess (BE) -1.9-4.5 mmol/L, saturated oxygen (sO₂) 23-93%, carboxyhaemoglobin 0.4-1.4% and methaemoglobin 0.3-0.9%. The meta-analysis revealed differences between ABG and VBG for pH, HCO₃-, pCO₂ and pO₂ of 0.032, -1.0 mmol/L, -4.2 and 39.9 mmHg, respectively. Using this data along with established ABG RI, calculated VBG RI of pH 7.32-7.42, HCO₃- 23 - 27 mmol/L, pCO₂ 36-49 mmHg (female), pCO₂ 39-52 mmHg (male) and pO₂ 43-68 mmHg were formulated and compared to the VBG RI of this study.

CONCLUSIONS

An adult reference interval has been established to assist interpretation of VBG results.

Can Venous Blood Gas Be Used as an Alternative to Arterial Blood Gas in Intubated Patients at Admission to the Emergency Department? A Retrospective Study

Objective

Blood gas analysis plays an important role in both diagnosis and subsequent treatment of critically ill patients in the emergency department and the ICU. Historically, arterial blood is predominantly used for blood gas analysis. The puncture is painful and complications may occur. The purpose of the present study was to evaluate the agreement between arterial and venous blood gas analysis and whether the sole use of venous blood gas analysis would have changed therapy.

Methods

Adult patients who were intubated in the field and received an arterial and venous blood gas analysis within 15 mins after admission to the ED were eligible for inclusion. The values for pH, pCO₂, HCO₃-, base excess and lactate levels were collected retrospectively. Mean differences were calculated by subtracting venous from arterial values. The agreement between venous and arterial measurements was assessed using the method of Bland and Altman. Blood gases were assessed by two independent physicians using a standardized questionnaire to determine whether the use of venous blood gases would have led to a different interpretation of the situation (other diagnostic path) or a change of therapy (eg. respirator adjustment). Acceptable limits were defined before the collection of data started.

Results

Fifty patients (62% male, median age 63years) who were treated at the Emergency Department between June 1, 2014 and December 31, 2014 were included in the study. Following average differences and limits of agreement (LOA) were documented: pH 0.02312 with LOA from −0.048 to 0.094; pCO₂ −3.612 mmHg with LOA from −15 to 8.1 mmHg; BE −0.154 mmol/l with LOA from −3.7 to 3.4 mmol/l; HCO₃−0.338 mmol/l with LOA from −2.27 to 2.9 mmol/l; Lactate −0.124 mg/dl with LOA from −2.28 to 2.03 mg/dl. Using venous blood gas results 100% of the patients with metabolic alkalosis were correctly diagnosed. Metabolic acidosis was detected with a high sensitivity (80.64%), specificity (89.47%) and positive predictive value (92.59%). The answers to lactate and acidosis due to AKI showed a specificity and positive predictive value of 100%. The respiratory adjustment showed a high sensitivity (91.89%) but a low specificity (38.46%).

Conclusion

For pH, bicarbonate, BE and lactate venous blood gases can be used as surrogates for arterial measurements. Venous pCO₂ can be used for screening of hypercapnia and trending. Respirator adjustments may be done too often if the venous blood gas is used.

Proof of Concept Study to Assess the Influence of Oxygen Partial Pressure in Capillary Blood on SMBG Measurements

BACKGROUND

Measurement results provided by blood glucose monitoring systems (BGMS) can be affected by various influencing factors. For some BGMS using glucose oxidase (GOx)-based test strips, one of these factors is the oxygen partial pressure (pO₂) of the applied blood sample. Because assessing the potential influence of pO₂ when measuring capillary blood samples is not straight-forward, we performed a proof of concept study.

METHOD

Influence of pO₂ was investigated for two GOx-based BGMS (BGMS A and B). Measurement results of the GOx-based BGMS were compared with measurement results from a pO₂-independent BGMS (BGMS C). A total of 119 samples from 60 subjects were measured, twice with BGMS C, then 6 times each with BGMS A and BGMS B or vice versa, and again twice with BGMS C. Immediately afterward, pO₂ was determined. Linear regression analysis based on relative differences between results from BGMS A or BGMS B and results from BGMS C was performed to estimate the degree of pO₂ influence.

RESULTS

The relative bias between the lowest and highest pO₂ values differed by 14.3% for BGMS A, indicating a pO₂ influence that might be clinically relevant, and by 9.7% for BGMS B, indicating that pO₂ influence may be too small to be reliably detected because of the BGMS' imprecision.

CONCLUSIONS

This proof of concept study showed that with the procedures used, a potentially clinically relevant influence of pO₂ in capillary blood samples on GOx-based BGMS could be detected. Further larger-scale studies are needed to verify this influence.

Acid-Base and Electrolyte Changes Drive Early Pathology in Ischemic Stroke

Emergent large vessel occlusion accounts for 20-40% of ischemic strokes and is the most debilitating form of stroke. Some of the earliest changes in response to ischemic stroke occur in blood gases and electrolytes. These biochemical changes occur within minutes after occlusion in experimental models of stroke and can be utilized to predict stroke outcomes. The majority of ELVO stroke patients are middle-aged to elderly and are of both sexes, revealing that there is an age and sex mismatch between ischemic stroke patients and animal models, since most experimental studies use young male rats. Rethinking of the animal models should be considered, especially in encouraging the use of aged male and female rats with comorbidities to more closely mirror human populations. Mechanical thrombectomy provides a unique opportunity for researchers to further this work by expanding the collection and analysis of blood samples that are adjacent to the thrombus. To understand the complexity of stroke, researchers can analyze these tissues for different molecular targets that occur in response to ischemic stroke. This information may aid in the reduction of symptom burden for individuals diagnosed with ischemic stroke. Investigators should also focus on data from ischemic stroke patients and attempt to discover target molecules and then in animal models to establish mechanism, which will aid in the development of new stroke therapies. This review discusses the translation of these studies to the human patient to develop the capability to predict stroke outcomes. Future studies are needed to identify molecular targets to predict the risk of worsened long-term outcomes and/or increased risk for mortality.

Evaluation of Sevoflurane Anesthesia in Donkeys (Equus asinus) Premedicated With Xylazine and Induced With Thiopental

Sevoflurane is a volatile anesthetic agent that has become popular in the field of large animal anesthesia. The aim of this study was to evaluate the use of sevoflurane in adult healthy donkeys. Six male, adult, healthy donkeys were premedicated with xylazine (1 mg/kg IV), induced with thiopental (5 mg/kg IV), and then maintained for 90 minutes with sevoflurane in 100% oxygen at a flow rate of 6 L/min with spontaneous breathing. Rectal temperature (RT), respiratory rate, heart rate (HR), oxygen hemoglobin saturation (OHS), and mean arterial blood pressure (MBP) were measured before and 20 minutes after the administration of xylazine, 10 minutes after the injection of thiopental, and then continuously every 10 minutes until recovery. Times for various signs of recovery, total duration of recovery, and quality of recovery were recorded. Jugular blood samples were collected from each donkey and complete blood counts and venous blood gases including concentrations of oxygen (PO₂) and carbon dioxide (PCO₂) were measured. In addition, the concentrations of sodium, potassium, calcium, lactate, bicarbonate, and glucose in venous blood were measured. Results showed that during the anesthesia maintained with sevoflurane, there was a significant decrease in HR, MBP, RT, red blood corpuscles, hematocrit, total white blood cells, neutrophils, and lymphocytes, whereas the levels of OHS and glucose significantly increased. The concentrations of PO₂, PCO₂, and lactate in venous blood significantly increased, whereas the pH significantly decreased. The levels of calcium significantly decreased immediately following the recovery. Sternal recumbency and standing occurred 15.8 ± 2.6 minutes and 28.2 ± 2.2 minutes, respectively, after turning off the vaporizer. Overall, the quality of recovery was good and relatively quick. It was concluded that sevoflurane appears to provide safe and effective anesthesia in donkeys, with relatively rapid induction and recovery.

The Relationship between Arterial and Central Venous Blood Gases Values in Patients Undergoing Mechanical Ventilation after Cardiac Surgery

Background

The most straightforward method of ascertaining arterial PO₂, PCO₂, and other components of blood gas is to measure them directly from a blood sample. In situations in which arterial puncture cannot be achieved or may be technically difficult, the venous blood sample can be used.

Methods

In a prospective analytical study, 80 patients undergoing mechanical ventilation after open-heart surgery in the intensive care unit were evaluated. Simultaneous, matched arterial and central venous blood gas samples were taken from radial artery line and central vein, respectively, when the ABG (arterial blood gases) assessment was needed. Arterial and central venous blood samples were analyzed and data were expressed as mean and ± SD.

Results

The Pearson correlation coefficient for pH, PCO₂, HCO₃, and SatO₂ was 0.898, 0.940, 0.840, and 0.567, respectively. There was a significant correlation between arterial and central venous values of pH, PCO₂, and HCO₃ (P < 0.0001). The mean difference between arterial and central venous PCO₂ was -2.44 ± 2.6 mmHg, and the mean venous pH value was only 0.021 ± 0.037 units lower than the mean arterial value. In addition, the calculated mean bicarbonate concentration in venous blood was only about 0.06 ± 1.5 mEq.L higher than the mean arterial value.

Conclusions

The central venous PCO₂, pH, and HCO₃ measured during mechanical ventilation in the intensive care unit approximate arterial values closely enough to permit the estimation of the adequacy of ventilation and acid-base status. The central venous Sat O₂ does not reliably parallel the arterial Sat O₂. In conclusion, venous blood sampling can potentially reduce the requirement for ABG sampling in special situations.

Differences in the intrinsic chondrogenic potential of equine umbilical cord matrix and cord blood mesenchymal stromal/stem cells for cartilage regeneration

Umbilical cord blood mesenchymal stromal/stem cells (UCB-MSCs) and umbilical cord matrix MSCs (UCM-MSCs) have chondrogenic potential and are alternative sources to standard surgically derived bone marrow or adipose tissue collection for cartilage engineering. However, the majority of comparative studies explore neonatal MSCs potential only on ISCT benchmark assays accounting for some bias in the reproducibility between in vitro and in clinical studies. Therefore, we characterized equine UCB-MSCs and UCM-MSCs and investigated with particular attention their chondrogenesis potential in 3D culture with BMP-2 + TGF-ß1 in normoxia or hypoxia. We carried out an exhaustive characterization of the extracellular matrix generated by both these two types of MSCs after the induction of chondrogenesis through evaluation of hyaline cartilage, hypertrophic and osteogenic markers (mRNA, protein and histology levels). Some differences in hypoxia sensitivity and chondrogenesis were observed. UCB-MSCs differentiated into chondrocytes express an abundant, dense and a hyaline-like cartilage matrix. By contrast, despite their expression of cartilage markers, UCM-MSCs failed to express a relevant cartilage matrix after chondrogenic induction. Both MSCs types also displayed intrinsic differences at their undifferentiated basal status, UCB-MSCs expressing higher levels of chondrogenic markers whereas UCM-MSCs synthesizing higher amounts of osteogenic markers. Our results suggest that UCB-MSCs should be preferred for ex-vivo horse cartilage engineering. How those results should be translated to in vivo direct cartilage regeneration remains to be determined through dedicated study.

Mathematical arterialisation of peripheral venous blood gas for obtainment of arterial blood gas values: a methodological validation study in the clinical setting

Arterial blood gas (ABG) analysis is an essential tool in the clinical assessment of acutely ill patients. Venous to arterial conversion (v-TAC), a mathematical method, has been developed recently to convert peripheral venous blood gas (VBG) values to arterialized VBG (aVBG) values. The aim of this study was to test the validity of aVBG compared to ABG in an emergency department (ED) setting. Twenty ED patients were included in this study. ABG and three aVBG samples were collected from each patient. The aVBG samples were processed in three different ways to investigate appropriate sample handling. All VBG samples were arterialized using the v-TAC method. ABG and aVBG samples were compared using Lin's concordance correlation coefficient (CCC), Bland-Altman plots and misclassification analysis. Clinical acceptable threshold of aVBG value deviance from ABG values were ± 0.05 pH units, ± 0.88 kPa pCO₂ and ± 0.88 kPa pO₂. CCC revealed an agreement in pH and pCO₂ parameters for both aVBG in comparison to ABG. In all aVBG samples, an overestimation of pO₂ compared to ABG was observed. Bland-Altman plot revealed clinically acceptable mean difference and limits-of-agreement intervals between ABG and aVBG pH and pCO₂, but not between ABG and aVBG pO₂. Arterialization of VBG using v-TAC is a valid method for measuring pH and pCO₂, but not for pO₂. Larger clinical studies are required to evaluate the applicability of v-TAC in different patient subpopulations.

Translational Evaluation of Acid/Base and Electrolyte Alterations in Rodent Model of Focal Ischemia

BACKGROUND AND PURPOSE

Acid/base and electrolytes could provide clinically valuable information about cerebral infarct core and penumbra. We evaluated associations between acid/base and electrolyte changes and outcomes in 2 rat models of stroke, permanent, and transient middle cerebral artery occlusion.

METHODS

Three-month old Sprague-Dawley rats underwent permanent or transient middle cerebral artery occlusion. Pre- and post-middle cerebral artery occlusion venous samples for permanent and transient models provided pH, carbon dioxide, oxygen, glucose, and electrolyte values of ionized calcium, potassium, and sodium. Multiple regression determined predictors of infarct volume from these values, and Kaplan-Meier curve analyzed morality between permanent and transient middle cerebral artery occlusion models.

RESULTS

Analysis indicated significant differences in the blood gas and electrolytes between pre- to post-middle cerebral artery occlusion. A decrease in pH and sodium with increases in carbon dioxide, potassium, ionized calcium, and glucose changes were found in both middle cerebral artery occlusion models; while hematocrit and hemoglobin were significant in the transient model. pH and ionized calcium were predictors of infarct volume in the permanent model, as changes in pH and ionized calcium decreased, infarct volume increased.

CONCLUSIONS

There are acute changes in acid/base balance and electrolytes during stroke in transient and permanent rodent models. Additionally, we found pH and ionized calcium changes predicted stroke volume in the permanent middle cerebral artery occlusion model. These preliminary findings are novel, and warrant further exploration in human conditions.

Utility of venous blood gases in severe sepsis and septic shock

Acid-base status is frequently assessed in severe sepsis and septic shock. Venous blood gas sampling is proposed as a less-invasive modality but lacks evidence within this population. The objective of this study was to evaluate the correlation and agreement between arterial blood gas (ABG), peripheral venous blood gas (pVBG), and central venous blood gas (cVBG) in severe sepsis and septic shock. We conducted a prospective, observational cohort study in subjects admitted to the medical intensive care unit. Simultaneous blood gas samples, including ABG, pVBG, and cVBG, were analyzed for correlation and agreement. Severity of illness scores revealed a mean (±SD) Sequential Organ Failure Assessment score of 7.9 ± 3.3, Simplified Acute Physiology II score of 49.3 ± 16.5, and a mortality rate of 11.9% in the intensive care unit and 16.4% in the hospital. We found a strong intraclass correlation (>0.85) for pH, partial pressure of carbon dioxide (pCO₂), bicarbonate, and base excess for ABG/pVBG, ABG/cVBG, and pVBG/cVBG comparisons. Agreement by the Bland-Altman method was found for pH (bias ± SD, 0.03 ± 0.04, 0.03 ± 0.02, and 0.00 ± 0.03) but not for pCO₂, partial pressure of oxygen, bicarbonate, base excess, and oxyhemoglobin saturation. In conclusion, adequate correlation and agreement between ABG/pVBG, ABG/cVBG, and pVBG/cVBG comparisons was found only for pH. The current level of evidence does not support the use of venous blood gas sampling in this setting.

Estimating Arterial Partial Pressure of Carbon Dioxide in Ventilated Patients: How Valid Are Surrogate Measures?

The arterial partial pressure of carbon dioxide (Pa_CO2) is an important parameter in critically ill, mechanically ventilated patients. To limit invasive procedures or for more continuous monitoring of Pa_CO2, clinicians often rely on venous blood gases, capnography, or transcutaneous monitoring. Each of these has advantages and limitations. Central venous Pco₂ allows accurate estimation of Pa_CO2, differing from it by an amount described by the Fick principle. As long as cardiac output is relatively normal, central venous Pco₂ exceeds the arterial value by approximately 4 mm Hg. In contrast, peripheral venous Pco₂ is a poor predictor of Pa_CO2, and we do not recommend using peripheral venous Pco₂ in this manner. Capnography offers measurement of the end-tidal Pco₂ (Pet_CO2), a value that is close to Pa_CO2 when the lung is healthy. It has the advantage of being noninvasive and continuously available. In mechanically ventilated patients with lung disease, however, Pet_CO2 often differs from Pa_CO2, sometimes by a large degree, often seriously underestimating the arterial value. Dependence of Pet_CO2 on alveolar dead space and ventilator expiratory time limits its value to predict Pa_CO2. When lung function or ventilator settings change, Pet_CO2 and Pa_CO2 can vary in different directions, producing further uncertainty. Transcutaneous Pco₂ measurement has become practical and reliable. It is promising for judging steady state values for Pa_CO2 unless there is overt vasoconstriction of the skin. Moreover, it can be useful in conditions where capnography fails (high-frequency ventilation) or where arterial blood gas analysis is burdensome (clinic or home management of mechanical ventilation).

Assessing Acid–Base Status in Circulatory Failure: Relationship Between Arterial and Peripheral Venous Blood Gas Measurements in Hypovolemic Shock

Background and Objectives:

In severe circulatory failure agreement between arterial and mixed venous or central venous values is poor; venous values are more reflective of tissue acid–base imbalance. No prior study has examined the relationship between peripheral venous blood gas (VBG) values and arterial blood gas (ABG) values in hemodynamic compromise. The objective of this study was to examine the correlation between hemodynamic parameters, specifically systolic blood pressure (SBP) and the arterial–peripheral venous (A-PV) difference for all commonly used acid–base parameters (pH, Pco 2, and bicarbonate).

Design, Setting, Participants, and Measurements:

Data were obtained prospectively from adult patients with trauma. When an ABG was obtained for clinical purposes, a VBG was drawn as soon as possible. Patients were excluded if the ABG and VBG were drawn >10 minutes apart.

Results:

The correlations between A-PV pH, A-PV Pco 2, and A-PV bicarbonate and SBP were not statistically significant ( P = .55, .17, and .09, respectively). Although patients with hypotension had a lower mean arterial and peripheral venous pH and bicarbonate compared to hemodynamically stable patients, mean A-PV differences for pH and Pco 2 were not statistically different ( P = .24 and .16, respectively) between hypotensive and normotensive groups.

Conclusions:

In hypovolemic shock, the peripheral VBG does not demonstrate a higher CO2 concentration and lower pH compared to arterial blood. Therefore, the peripheral VBG is not a surrogate for the tissue acid–base status in hypovolemic shock, likely due to peripheral vasoconstriction and central shunting of blood to essential organs. This contrasts with the selective venous respiratory acidosis previously demonstrated in central venous and mixed venous measurements in circulatory failure, which is more reflective of acid–base imbalance at the tissue level than arterial blood. Further work needs to be done to better define the relationship between ABG and both central and peripheral VBG values in various types of shock.

Surrogate scale for evaluating respiratory function based on complete blood count parameters

BACKGROUND

In this study, we aimed to identify a simple method for evaluating respiratory function using complete blood count parameters.

METHODS

The complete blood count parameters, including red blood cell (RBC) count, hemoglobin (Hb) level, lymphocyte (Lym) and platelet (Plt) count, and partial pressure of oxygen (PO₂ ) level, were measured using automated analyzers in patients with chronic obstructive pulmonary disease (COPD), aged subjects, and young subjects (control group). The red cell index (RCI) was calculated using the following equation: (RBC × Hb)/(Lym × Plt); in theory, the RCI is inversely proportional to the respiratory function.

RESULTS

We observed a significant relationship between the RCI and PCO₂ values, and between the RCI and FEV1/FVC values (P < .05). The RCI in the COPD, and aged subject groups were all significantly higher than that in the control group (P < .05). The cutoff value for normal respiratory function was 2.3. The positive rates for an abnormal increase in RCI were also considerably higher in each observation group than in the control group (P < .05).

CONCLUSION

The RCI can be considered as a simple and effective tool for evaluating respiratory function.

Agreement between Arterial and Venous Blood Gases In Emergency Medical Care: A Systematic Review

Aim

The objectives of this review are to describe the agreement between arterial and venous blood gas values for pH, pCO2, bicarbonate and base excess.

Methods

MEDLINE search of papers published 1966-September 2012 for studies comparing arterial and peripheral venous blood gas values for any of pH, pCO2, bicarbonate and base excess in adult patients with any condition in an emergency department setting. The outcome of interest was mean difference weighted for study sample size.

Results

The weighted mean arterio-venous difference in pH was 0.034 pH units (n=2087), with narrow limits of agreement. The weighted mean arterio-venous difference for pCO2 was 6.2 mmHg (n=1043), but with 95% limits of agreement up to the order of ±20mmHg. Venous pCO2<45 mmHg has 100% sensitivity and negative predictive value for prediction of arterial hypercarbia (n=529). For bicarbonate, the weighted mean difference between arterial and venous values was −1.20 mEq/L (n=1403), with 95% limits of agreement of the order of ±5 mmol/L. Regarding base excess, the mean arterio-venous difference was 0.4 (n=295) but data are conflicting regarding the width of 95% limits of agreement.

Conclusion

For patients who are not in shock, venous pH and bicarbonate have sufficient agreement to be clinically interchangeable for arterial values. Agreement between arterial and venous pCO2 is too poor and unpredictable to be clinically useful as a one-off test but venous pCO2 may be useful to screen for arterial hypercarbia.

Prediction of arterial blood gas values from venous blood gas values in Asiatic black bears (Ursus thibetanus) anesthetized with intramuscular medetomidine and zolazepam-tiletamine

The objective of this study was to measure differences between arterial and venous blood gas parameters and to evaluate whether arterial blood gas values can be estimated from venous blood in Asiatic black bears (ABBs). Twelve healthy captive ABBs (8 males and 4 females; 8-16 years; 76.8-220 kg) were included in this study. The bears were immobilized with medetomidine and zolazepam-tiletamine using a dart gun. Arterial and venous samples were collected simultaneously at 5 and 35 min after recumbency (5- and 35-min points). Partial pressure of oxygen (PO2), partial pressure of carbon dioxide (PCO2), pH, bicarbonate (HCO3-), total carbon dioxide (TCO2), oxygen saturation of hemoglobin (SO2) and base excess (BEecf) were analyzed using a portable blood gas analyzer. There was no marked difference in measured and calculated variables over time in both venous and arterial blood except for PO2. However, arterial PO2, SO2 and pH were significantly higher and arterial PCO2, TCO2 and HCO3- were lower than those of venous samples at both 5- and 35-min points. In the regression analysis to estimate arterial values from venous values, PCO2, TCO2, HCO3-, BEecf and pH significantly showed over 0.45 in coefficient of determination value (R2), and there were little differences between actual and predicted arterial values. Although there were limits in venous gas values replaced those of arterial blood, if we could not get the arterial samples, the regression formulas for arterial values from venous blood in this study would be useful clinically, except for PO2 and SO2.

Capillary blood for point-of-care testing

Clinically, blood sample analysis has been widely used for health monitoring. In hospitals, arterial and venous blood are utilized to detect various disease biomarkers. However, collection methods are invasive, painful, may result in injury and contamination, and skilled workers are required, making these methods unsuitable for use in a resource-limited setting. In contrast, capillary blood is easily collected by a minimally invasive procedure and has excellent potential for use in point-of-care (POC) health monitoring. In this review, we first discuss the differences among arterial blood, venous blood, and capillary blood in terms of the puncture sites, components, sample volume, collection methods, and application areas. Additionally, we review the most recent advances in capillary blood-based commercial products and microfluidic instruments for various applications. We also compare the accuracy of microfluidic-based testing with that of laboratory-based testing for capillary blood-based disease diagnosis at the POC. Finally, we discuss the challenges and future perspectives for developing capillary blood-based POC instruments.

Agreement and Correlation between Arterial and Central Venous Blood Gas Following Coronary Artery Bypass Graft Surgery

INTRODUCTION

Arterial blood sampling, used to assess patients in acute conditions, may result in complications such as thrombosis and embolism. However, it can be replaced by venous blood sampling, but there is a dearth of information on this.

AIM

To assess the correlation and agreement between the arterial and central venous blood gases analyses in patients undergoing elective Coronary Artery Bypass Graft (CABG) surgery.

MATERIALS AND METHODS

In this cross-sectional study, 100 ICU patients undergoing elective CABG surgery were recruited. 2 mm arterial and a 2 mm venous blood samples were obtained from each patient's arterial and central venous lines, respectively. To predict Arterial Blood Gas (ABG) values based on central Venous Blood Gas (VBG) values, the linear regression analysis was used and for evaluating their agreement Bland-Altman method was used.

RESULTS

In total of 200 samples were obtained. The mean and Standard Deviation (SD) of age was 58.9±9.1 years and 51% of the participants were female. There was a strong correlation between ABG and central VBG values regarding pH, partial Pressure of Carbon Dioxide (PCO₂), Bicarbonate (HCO₃) and Base Excess (BE) (r= 0.73, r=0.74, r=0.67 and r=0.71, respectively; p<0.001); however, the correlation between the arterial and venous Partial Pressure of Oxygen (PO₂) and Oxygen Saturation (SO₂) was moderate (r=0.29, p=0.005 and r=0.27, p=0.006, respectively). The Bland-Altman analysis showed an excellent agreement between all the variables (p<0.001).

CONCLUSION

Central VBG analysis cannot replace ABG analysis in measuring exact PO₂ status, necessitating arterial sampling in some matters, but with respect to the accuracy of pulse oximetry measurements in determining the exact PO₂ status, for the rest of the indices a central VBG rather than an ABG can be utilised for determining patient's acid-base status. Particularly in patients who are hospitalised for a long time and have a central venous catheter in place like patients who have undergone CABG, thus reducing the risk and need for invasive arterial sampling.

Correlation of Venous Blood Gas and Pulse Oximetry With Arterial Blood Gas in the Undifferentiated Critically Ill Patient

RATIONALE

Blood gas analysis is often used to assess acid-base, ventilation, and oxygenation status in critically ill patients. Although arterial blood gas (ABG) analysis remains the gold standard, venous blood gas (VBG) analysis has been shown to correlate with ABG analysis and has been proposed as a safer less invasive alternative to ABG analysis.

OBJECTIVE

The purpose of this study was to evaluate the correlation of VBG analysis plus pulse oximetry (SpO₂) with ABG analysis.

METHODS

We performed a prospective cohort study of patients in the emergency department (ED) and intensive care unit (ICU) at a single academic tertiary referral center. Patients were eligible for enrollment if the treating physician ordered an ABG. Statistical analysis of VBG, SpO₂, and ABG data was done using paired t test, Pearson χ², and Pearson correlation.

MAIN RESULTS

There were 156 patients enrolled, and 129 patients completed the study. Of the patients completing the study, 53 (41.1%) were in the ED, 41 (31.8%) were in the medical ICU, and 35 (27.1%) were in the surgical ICU. The mean difference for pH between VBG and ABG was 0.03 (95% confidence interval: 0.03-0.04) with a Pearson correlation of 0.94. The mean difference for pCO₂ between VBG and ABG was 4.8 mm Hg (95% confidence interval: 3.7-6.0 mm Hg) with a Pearson correlation of 0.93. The SpO₂ correlated well with PaO₂ (the partial pressure of oxygen in arterial blood) as predicted by the standard oxygen-hemoglobin dissociation curve.

CONCLUSION

In this population of undifferentiated critically ill patients, pH and pCO₂ on VBG analysis correlated with pH and pCO₂ on ABG analysis. The SpO₂ correlated well with pO₂ on ABG analysis. The combination of VBG analysis plus SpO₂ provided accurate information on acid-base, ventilation, and oxygenation status for undifferentiated critically ill patients in the ED and ICU.

Management of Acute Exacerbation of Asthma and Chronic Obstructive Pulmonary Disease in the Emergency Department

Acute asthma and chronic obstructive pulmonary disease (COPD) exacerbations are the most common respiratory diseases requiring emergent medical evaluation and treatment. Asthma and COPD are chronic, debilitating disease processes that have been differentiated traditionally by the presence or absence of reversible airflow obstruction. Asthma and COPD exacerbations impose an enormous economic burden on the US health care budget. In daily clinical practice, it is difficult to differentiate these 2 obstructive processes based on their symptoms, and on their nearly identical acute treatment strategies; major differences are important when discussing anatomic sites involved, long-term prognosis, and the nature of inflammatory markers.

Prediction of extubation failure in newborns, infants and children: brief report of a prospective (blinded) cohort study at a tertiary care paediatric centre in India

BACKGROUND

Extubation failure (EF), defined as need for re-intubation within 24-72 h, is multifactorial. Factors predicting EF in adults generally are not useful in children.

OBJECTIVE

To determine the factors associated with EF and to facilitate prediction of EF in mechanically ventilated infants and children less than 12 years of age. MATERIAL AND 

METHODS

Design Prospective cohort study. Setting PICU and NICU of a multispecialty tertiary care institute. Patients All consecutive newborns, infants and children, who remained on the ventilator for more than 12 h, were included. Patients with upper airway obstruction, neuromuscular disorders, complex anatomic malformations, accidental extubation, tracheostomy or death before extubation were excluded. Methods The pre-extubation clinical, laboratory and ventilatory parameters were collected for 92 cases over a one and half year period. The EF rate was calculated for each variable using STATA 9. All the treating physicians were blinded to the data collection procedure.

MEASUREMENTS AND RESULTS

Demographics were comparable between the extubation success and EF groups. Respiratory failure was the main cause requiring ventilation (46.74 %, 95 % CI 0.37-0.57) as well as EF (30.23 %, 95 % CI 0.08-0.23). 76.92 % (95 % CI 0.58-0.89) of patients that failed extubation had alterations in respiratory effort, 38.46 % (95 % CI 0.22-0.57) each had either poor or increased respiratory effort. Poor cough reflex (p = 0.001), thick endotracheal secretions (p = 0.02), failed spontaneous breathing trial (SBT) (p = 0.001) and higher rapid shallow breathing index (RSBI) (p = 0.001) were found to be associated with EF.

CONCLUSIONS

Paediatric EF is multifactorial. Increased or poor respiratory effort and failed SBT are potential factors in deciding re-intubation. Increased RSBI, poor cough reflex and thick.

Arterial puncture using insulin needle is less painful than with standard needle: a randomized crossover study

OBJECTIVES

Arterial punctures are important procedures performed by emergency physicians in the assessment of ill patients. However, arterial punctures are painful and can create anxiety and needle phobia in patients. The pain score of radial arterial punctures were compared between the insulin needle and the standard 23-gauge hypodermic needle.

METHODS

In a randomized controlled crossover design, healthy volunteers were recruited to undergo bilateral radial arterial punctures. They were assigned to receive either the insulin or the standard needle as the first puncture, using blocked randomization. The primary outcome was the pain score measured on a 100-mm visual analogue scale (VAS) for pain, and secondary outcomes were rate of hemolysis, mean potassium values, and procedural complications immediately and 24 hours postprocedure.

RESULTS

Fifty healthy volunteers were included in the study. The mean (±standard deviation) VAS score in punctures with the insulin needle was lower than the standard needle (23 ± 22 mm vs. 39 ± 24 mm; mean difference = -15 mm; 95% confidence interval = -22 mm to -7 mm; p < 0.001). The rates of hemolysis and mean potassium value were greater in samples obtained using the insulin needle compared to the standard needle (31.3% vs. 11.6%, p = 0.035; and 4.6 ±0.7 mmol/L vs. 4.2 ±0.5 mmol/L, p = 0.002). Procedural complications were lower in punctures with the insulin needle both immediately postprocedure (0% vs. 24%; p < 0.001) and at 24 hours postprocedure (5.4% vs. 34.2%; p = 0.007).

CONCLUSIONS

Arterial punctures using insulin needles cause less pain and fewer procedural complications compared to standard needles. However, due to the higher rate of hemolysis, its use should be limited to conditions that do not require a concurrent potassium value in the same blood sample.

Effects of Cardiac Hemodynamics on Agreement in the pH, HCO3- and Lactate Levels between Arterial and Venous Blood Samples in Patients with Known or Suspected Chronic Heart Failure

OBJECTIVE

Analyses of arterial blood gas parameters, including pH, HCO3- and lactate, play an important role in assessing the clinical status of patients with heart failure. In the present study, we evaluated the degree of agreement in the pH, HCO3- and lactate levels between arterial and venous blood samples according to the subset of the Forrester classification.

METHODS

The study population consisted of 128 patients with known or suspected heart failure. The subjects were divided into four groups based on the Forrester classification. Arterial blood samples were drawn from the radial or brachial artery, and venous blood samples were drawn from the pulmonary artery.

RESULTS

There were 59 patients with a Forrester subset I status, 32 patients with a subset II status, 21 patients with a subset III status and 16 patients with a subset IV status. The pH and HCO3- levels were similar between the four subsets. In all subsets, the pH values were significantly higher and the HCO3- values were significantly lower in the arterial blood samples than in the venous blood samples. There was good correlation and agreement in the pH and HCO3- levels between the arterial and venous blood samples. In contrast, there was a significant difference in the lactate levels in both the arterial and venous blood samples between the four subsets, and the lactate levels were highest in subset IV. In all subsets, there was good correlation and agreement in the lactate levels between the arterial and venous blood samples.

CONCLUSION

These data suggest that the venous pH, HCO3- and lactate levels are acceptable substitutes for arterial parameters, regardless of the cardiac hemodynamics.

[Concordance between central venous and arterial blood gases in post-surgical myocardial revascularization patients in stable condition]

OBJECTIVE

The concordance between the parameters of arterial and central venous blood gases has not been defined yet. We studied the concordance between both parameters in post-surgical myocardial revascularization patients in stable condition.

METHODS

Consecutive subjects were studied in a cross-sectional design. The position of the central venous catheter was performed and simultaneously we obtained arterial and central venous blood samples prior to discharge from the intensive care unit. Data are expressed according to Bland-Altman statistical method and the intraclass correlation coefficient. Statistical result was accepted at P<.05.

RESULTS

Two hundred and six samples were studied of 103 post-surgical patients, pH and lactate had a mean difference (limits of agreement) 0.029±0.048 (-0018, 0.077) and -0.12±0.22 (-0.57, 0.33) respectively. The magnitude of the intraclass correlation coefficient was 0.904 and 0.943 respectively. The values related to oxygen pressure were 27.86±6.08 (15.9, 39.8) and oxygen saturation 33.02±6.13 (21, 45), with magnitude of 0.258 and 0.418 respectively.

CONCLUSION

The best matching parameters between arterial and central venous blood samples were pH and lactate.

Impact of partial pressure of oxygen in blood samples on the performance of systems for self-monitoring of blood glucose

BACKGROUND

The partial pressure of oxygen (pO2) in blood samples can affect glucose measurements with oxygen-sensitive systems. In this study, we assessed the influence of different pO2 levels on blood glucose (BG) measurements with five glucose oxidase (GOD) systems and one glucose dehydrogenase (GDH) system. All selected GOD systems were indicated by the manufacturers to be sensitive to increased oxygen content of the blood sample.

MATERIALS AND METHODS

Venous blood samples of 16 subjects (eight women, eight men; mean age, 52 years; three with type 1 diabetes, four with type 2 diabetes, and nine without diabetes) were collected. Aliquots of each sample were adjusted to the following pO2 values: ≤45 mm Hg, approximately 70 mm Hg, and ≥150 mm Hg. For each system, five consecutive measurements on each sample were performed using the same test strip lot. Relative differences between the mean BG value at a pO2 level of approximately 70 mm Hg, which was considered to be similar to pO2 values in capillary blood samples, and the mean BG value at pO2 levels ≤45 mm Hg and ≥150 mm Hg were calculated.

RESULTS

The GOD systems showed mean relative differences between 11.8% and 44.5% at pO2 values ≤45 mm Hg and between -14.6% and -21.2% at pO2 values ≥150 mm Hg. For the GDH system, the mean relative differences were -0.3% and -0.2% at pO2 values ≤45 mm Hg and ≥150 mm Hg, respectively.

CONCLUSIONS

The magnitude of the pO2 impact on BG measurements seems to vary among the tested oxygen-sensitive GOD systems. The pO2 range in which oxygen-sensitive systems operate well should be provided in the product information.

Influence of partial pressure of oxygen in blood samples on measurement performance in glucose-oxidase-based systems for self-monitoring of blood glucose

BACKGROUND

Partial pressure of oxygen (pO2) in blood samples can affect blood glucose (BG) measurements, particularly in systems that employ the glucose oxidase (GOx) enzyme reaction on test strips. In this study, we assessed the impact of different pO2 values on the performance of five GOx systems and one glucose dehydrogenase (GDH) system. Two of the GOx systems are labeled by the manufacturers to be sensitive to increased blood oxygen content, while the other three GOx systems are not.

METHODS

Aliquots of 20 venous samples were adjusted to the following pO2 values: <45, ~70, and ≥150 mmHg. For each system, five consecutive measurements on each sample aliquot were performed using the same test strip lot. Relative differences between the mean BG results at pO2 ~70 mmHg, which is considered to be similar to pO2 in capillary blood samples, and the mean BG result at pO2 <45 and ≥150 mmHg were calculated.

RESULTS

For all tested GOx systems, mean relative differences in the BG measurement results were between 6.1% and 22.6% at pO2 <45 mmHg and between -7.9% and -14.9% at pO2 ≥150 mmHg. For both pO2 levels, relative differences of all tested GOx systems were significant (p < .0001). The GDH system showed mean relative differences of -1.0% and -0.4% at pO2 values <45 and ≥150 mmHg, respectively, which were not significant.

CONCLUSIONS

These data suggest that capillary blood pO2 variations lead to clinically relevant BG measurement deviations in GOx systems, even in GOx systems that are not labeled as being oxygen sensitive.

Blood total carbon dioxide content and bicarbonate can be used together to predict blood pH correctly in venous blood samples

Blood gas analyses are needed to reveal any kind of acid-base imbalance in some patients. Traditionally, arterial punctures are performed to obtain the blood samples for blood gas analyses. Arterial puncture is not a completely safe procedure. It may cause serious problems including arterial thrombosis, arteriovenous fistula, pseudoaneurysms and hematoma. In this retrospective reviewing, it was aimed to yield novel formulations to predict the blood pH only from CtCO2 and HCO3 values which can easily be measured in venous blood samples obtained for other diagnostic and follow-up purposes.

Peripheral venous blood gases and pulse-oximetry in acute cardiogenic pulmonary oedema

BACKGROUND

The role of venous blood gases as an alternative to arterial blood gases in patients with severe acute heart failure has not been established.

OBJECTIVE

To assess the correlation between arterial and peripheral venous blood gases together with pulse-oximetry (SpO2), as well as to estimate arterial values from venous samples in the first hours upon admission of patients with acute cardiogenic pulmonary oedema.

METHODS

Simultaneous venous and arterial blood samples were extracted on admission and over the next 1, 2, 3, 4, and 10 hours. SpO2 was also registered at the same intervals.

RESULTS

A total of 178 pairs of samples were obtained from 34 consecutive patients with acute cardiogenic pulmonary oedema. Arterial and venous blood gases followed a parallel course in the first hours, showing high correlation rates at all time intervals. Venous samples underestimated pH (mean difference -0.028) and overestimated CO2 (+5.1 mmHg) and bicarbonate (+1 mEq/l). Conversely, SpO2 tended to underestimate SaO2 (mean±SD: 93.1±9.1 vs. 94.2±8.4). Applying simple mathematical formulae based on these differences, arterial values were empirically calculated from venous samples, showing acceptable agreement in the Bland-Altman test. Likewise, a venous pH <7.32, pCO2 >51.3 mmHg, and bicarbonate <22.8 mEq/l could fairly identify arterial acidosis, either respiratory or metabolic, with a test accuracy of 92, 68, and 91%, respectively.

CONCLUSIONS

In patients with cardiogenic pulmonary oedema, arterial blood gas disturbances may be estimated from peripheral venous samples. By monitoring SpO2 simultaneously, arterial punctures could often be avoided.

Clinicopathologic analysis of Passeriform venous blood reflects transitions in elevation and habitat

Jugular blood samples from 110 Passeriformes collected at several Texas locations were analyzed for multiple clinicopathologic parameters between April 2010 and August 2011. Electrolyte, blood gas, and select erythrocyte parameters were analyzed on site with a point of care analyzer, and gender, age, body condition score, location, and species were recorded. Many analytes exhibited a Gaussian distribution across species and are reported as a single range. Taxon affected electrolyte and red blood cell parameters, but not most blood gas or acid base variables. Migratory status affected select electrolytes but few blood gas variables. Red blood cell parameters were affected the most by variables of age, taxonomic group, and gender, but not migratory life history. We found significant changes in glucose and numerous acid base analytes in birds sampled from habitats with evolutionarily recent ecologic degradation. We advocate the use of these analytes, particularly venous blood gas values, as determined by a point of care analyzer, as reasonable biomarkers for determination of Passeriform population health, but also recommend that red blood cell parameters and electrolyte concentrations be controlled for age, species, and gender in future studies. Further, based on our investigation, venous blood gas values and acid base balance in Passeriformes can assess the health of an ecosystem.

Correlation between peripheral venous and arterial blood gas measurements in patients admitted to the intensive care unit: A single-center study

Background

The objective of this study was to examine the correlation between arterial blood gas (ABG) and peripheral venous blood gas (VBG) samples for all commonly used parameters in patients admitted to a medical intensive care unit (ICU).

Methods

A single-center, prospective trial was carried out in a medical ICU in order to determine the level of correlation of ABG and peripheral VBG measurements. A maximum of five paired ABG–VBG samples were obtained per patient to prevent a single patient from dominating the data set.

Results

Regression equations were derived to predict arterial values from venous values as follows: arterial pH=−1.108+1.145×venous pH+0.008×PCO₂−0.012×venous HCO₃+0.002×venous total CO₂ (R²=0.655), arterial PCO₂=88.6−10.888×venous pH+0.150×PCO₂+0.812×venous HCO₃+0.124×venous total CO₂ (R²=0.609), arterial HCO₃=−89.266+12.677×venous pH+0.042×PCO₂+0.675×venous HCO₃+0.185×venous total CO₂ (R²=0.782). The mean ABG minus peripheral VBG differences for pH, PCO₂, and bicarbonates were not clinically important for between–person heterogeneity.

Conclusion

Peripheral venous pH, PCO₂, bicarbonates, and total CO₂ may be used as alternatives to their arterial equivalents in many clinical contexts encountered in the ICU.

Improving the validity of peripheral venous blood gas analysis as an estimate of arterial blood gas by correcting the venous values with SvO₂

BACKGROUND

Peripheral venous blood gas (pVBG) analysis in replacement of arterial blood gas (ABG) is limited by the unpredictable differences between arterial and venous values, especially for PCO2 and pH (ΔPCO2 and ΔpH).

OBJECTIVES

We hypothesized that, using the theoretical relationship linking SvO2 and blood flow, we could diminish the effect of local circulatory conditions on ΔPCO2 and ΔpH and thereby increase pVBG validity.

METHODS

This was a prospective cross-sectional study performed in emergency patients requiring a blood gas analysis in which ABG and pVBG were performed simultaneously. The data of 50 randomly selected patients (model group) were used for developing two equations to correct PvCO2 and pHv according to the peripheral SvO2 (SpvO2) level. The formulas derived were PvCO2cor = PvCO2 - 0.30 × (75 - SpvO2), and pHvcor = pHv + 0.001 × (75 - SpvO2). The validity of the corrected values was then tested on the remaining population (validation group).

RESULTS

There were 281 patients included in the study, mainly for dyspnea. ΔPCO2 and ΔpH were strongly correlated with SpvO2 (r(2) = 0.62 and r(2) = 0.53, respectively, p < 0.001). Using the data of the model group, we developed equations that we applied on the validation group. We found that the corrected values were more valid than the raw values for detecting a PaCO2 > 45 mm Hg (AUC ROC = 0.96 ± 0.01 vs. 0.89 ± 0.02, p < 0.001), a PaCO2 < 35 mm Hg (AUC = 0.95 ± 0.02 vs. 0.84 ± 0.03, p < 0.001), a pHa < 7.35 (AUC = 0.97 ± 0.01 vs. 0.95 ± 0.02, p < 0.05), or a pHa > 7.45 (AUC = 0.91 ± 0.02 vs. 0.81 ± 0.04, p < 0.001).

CONCLUSIONS

The variability of ΔPCO2 and ΔpH is significantly lowered when the venous values are corrected according to the SpvO2 value, and pVBG is therefore more accurate and valid for detecting an arterial abnormality.