Peripheral venous and arterial blood gas analysis in adults: are they comparable? A systematic review and meta‐analysis

Peripheral venous blood gas (PVBG) analysis is increasingly being used as a substitute for arterial blood sampling; however, comparability has not been clearly established. To determine if the pH, PCO₂ and PO₂ obtained from PVBG analysis is comparable with arterial blood gas (ABG) analysis. A search was conducted of electronic databases as well as hand‐searching of journals and reference lists through December 2012 to identify studies comparing PVBG with ABG analysis in adult subjects. A systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta‐Analyses statement. A meta‐analysis using a random effects model was used to calculate the average difference (bias) and the limits of agreement for the venous and arterial pH, PCO₂ and PO₂. A total of 18 studies comprising 1768 subjects were included in the meta‐analysis. There was considerable heterogeneity between studies with I² approaching 100%. There was little difference between the pH obtained from the PVBG and the ABG, with the arterial pH typically 0.03 higher than the venous pH (95% confidence interval 0.029–0.038). The venous and arterial PCO₂ were not comparable because the 95% prediction interval of the bias for venous PCO₂ was unacceptably wide, extending from ?10.7 mm Hg to +2.4 mm Hg. The PO₂ values compared poorly, the arterial PO₂ typically 36.9 mm Hg greater than the venous with significant variability (95% confidence interval from 27.2 to 46.6 mm Hg). PVBG analysis compares well with ABG analysis for pH estimations in adults but not to the PCO₂ or PO₂. These differences are sufficiently large to be of clinical significance.     

An overnight increase in CO2 predicts mortality in sleep disordered breathing

Background and objective: Sleep disordered breathing (SDB) is highly prevalent but under‐recognized. Evidence is accumulating for its role as a predictor of mortality independent of cardiovascular risk factors. The role of hypercapnia in SDB is not known systematically, and between 11 and 43% of patients with SDB develop chronic hypercapnia. Hypercapnia predicts mortality in other respiratory conditions. The role of hypercapnia in independently predicting mortality in patients with SDB after assessing for the presence of airways disease and obesity was investigated. Methods: The records of 396 consecutive patients were examined retrospectively. Univariate and multivariate analyses were performed using Cox proportional hazards regression to determine the association between gas exchange and polysomnography (PSG) variables and all‐cause mortality, adjusted for potential confounders, including age, gender and presence of co‐morbidity and airways disease. Results: The mean age of our patient population was 55 ± 15 years, and the mean body mass index (BMI) was 30.6 ± 6.2 kg/m². Out of the 322 patient population, 258 were men. After 10 years, 25% had died, following a maximum follow‐up of 16.7 years. Mortality among patients with SDB was predicted by a difference between evening and morning PaCO₂ (ΔPaCO₂) of ≥7 mm Hg and evening hypoxaemia (PaO₂ < 65 mm Hg), independent of age and the presence of co‐morbidity and airways disease. There was a significant correlation between minimum oxygen saturation (SpO₂) and ΔPaCO₂ ≥ 7 mm Hg (P = 0.002) and evening PaO₂ < 65 mm Hg (P < 0.001). Conclusions: An overnight increase in CO₂ and evening hypoxaemia are independent mortality predictors in SDB. A low minimum SpO₂ identifies patients in whom morning and evening arterial blood gases are beneficial.     

Assessing PaCO2 in acute respiratory disease: accuracy of a transcutaneous carbon dioxide device

Background: Pulse oximetry non‐invasively assesses the arterial oxygen saturation of patients with acute respiratory disease; however, measurement of the arterial partial pressure of carbon dioxide (PaCO₂) requires an arterial blood gas. The transcutaneous partial pressure of carbon dioxide (PtCO₂) has been used in other settings with variable accuracy. We investigated the accuracy of a PtCO₂ device in the assessment of PaCO₂ in patients with asthma and suspected pneumonia attending the emergency department. Methods: Patients with severe asthma (FEV₁ < 50% predicted) or suspected pneumonia (fever, cough and respiratory rate >18/min) were enrolled. Subjects were excluded if they had a history of chronic obstructive pulmonary disease or other conditions associated with respiratory failure. Arterial blood gases were taken at the discretion of the investigator according to clinical need, and paired with a simultaneous reading from the PtCO₂ probe. Results: Twenty‐five patients were studied with one set of data excluded because of poor PtCO₂ signal quality. The remaining 24 paired samples comprised 12 asthma and 12 pneumonia patients. The range of PaCO₂ was 19–64 mmHg with a median of 36.5 mmHg. Bland–Altman analysis showed a mean (SD) PaCO₂– PtCO₂ difference of ?0.13 (1.9) mmHg with limits of agreement of plus or minus 3.8 mmHg (?3.9 to +3.7). Conclusion: A PtCO₂ device was accurate in the assessment of PaCO₂ in patients with acute severe asthma and suspected pneumonia when compared with an arterial blood gas. These bedside monitors have the potential to improve patient care by non‐invasively monitoring patients with acute respiratory disease at risk of hypercapnia.     

Prognostic significance of PaO2/PaCO2 ratio in normotensive patients with pulmonary embolism

Introduction: Risk stratification remains controversial in patients with normotensive pulmonary embolism (PE). The debate has recently focused right ventricular dysfunction detected by echocardiography or spiral computed tomography (CT) and cardiac biomarkers. Objectives: The utility of the PaO₂/PaCO₂ ratio to predict the short‐term prognosis of PE is not currently known and that is the aim of the present study. Materials and Methods: This study retrospectively enrolled 99 (34 males, 65 females, 67 ± 15 years) consecutive patients with acute PE, diagnosed by spiral chest tomography pulmonary angiography (CTPA).On admission, cardiac troponin T (cTn‐T) was measured and on CTPA both right ventricle diameter and left ventricle diameter was calculated (RV/LV ratio). During the first 24 h after admission, all the patients had initial arterial blood gas collected under room air. Receiver‐operating characteristic (ROC) analysis was performed to determine the optimal PaO₂/PaCO₂, RV/LV ratio and cTn‐T cutoff level with regard to prognosis. Results: In‐hospital mortality was 12.1% and all‐cause 90‐day mortality was 15.2%. Ten of 15 patients who died had a PaO₂/PaCO₂ ≤ 1.8 based on ROC analysis (P < 0.014).The cutoff level of PaO₂/PaCO₂ ≤ 1.8 had a high negative predictive value of 93% for mortality. Multivariable analysis revealed that PaO₂/PaCO₂ ≤ 1.8 Hazard Ratio (HR): 16.8 [95% CI: 2.6–108, P < 0.003] was the most significant independent predictor, whereas cTn‐T, pO₂ < 60 mmHg and cardiac failure were nonsignificant factors. In addition, PaO₂/PaCO₂ ≤ 1.8 showed significant survival differences for overall mortality rates in Kaplan–Meier analysis (P < 0.012). Conclusion: The PaO₂/PaCO₂ measurement is a highly useful and practical measurement to predict prognosis in patients with acute PE. Moreover, it appears to be a more accurate predictor than RV/LV ratio and cTn‐T levels in patients with normotensive PE. Please cite this paper as: Ozsu S, Abul Y, Yilmaz I, Ozsu A, Oztuna F, Bulbul Y and Ozlu T. Prognostic significance of PaO₂/PaCO₂ ratio in normotensive patients with pulmonary embolism. Clin Respir J 2012; 6: 104–111.     

Fluorescence optical fibre sensor provides accurate continuous oxygen detection in rabbit model with acute lung injury

Background and objective: Continuous monitoring of PaO₂ in seriously ill patients is an important aspect of clinical management, especially for patients with acute lung injury (ALI) or acute respiratory distress syndrome. We have developed a fibreoptic sensor to detect PaO₂in vivo based on fluorescence quenching technology. In this study we evaluated the sensitivity of this sensor in monitoring PaO₂ in a rabbit model with ALI. Methods: The oxygen sensor is a membrane made of Ru(dpp)₃(PF6)₂, poly‐2‐methacryloyloxyethyl phosphorylcholine and butylmethacylate copolymer p‐(MPC‐co‐BMA) located at the tip of the optical fibre. The sensor was inserted into the carotid artery of the animals and monitored PaO₂ continuously. Oleic acid was intravenously injected to induce lung injury. Simultaneous comparisons were made between PaO₂ measured by blood gas analysis and PaO₂ measured by the fibreoptic sensor, both before and after lung injury. Results: The fluorescence intensity decreased gradually following ALI, reflecting increasing hypoxia. Correlation coefficients between measurements by the oxygen sensor and by the blood gas analysis were 0.995 ± 0.003, 0.994 ± 0.002 and 0.993 ± 0.005 (P < 0.05) for control animals, animals with ALI and animals with electrolyte disturbance, respectively. The bias and precision for normal animals was ?1.5 ± 10.8 mm Hg, for animals with ALI was ?1.2 ± 11.2 mm Hg and for animals with electrolyte disturbance was ?1.4 ± 9.2 mm Hg. Conclusions: The oxygen sensor showed high accuracy and stability for continuous monitoring of PaO₂ in normal animals, in animals with ALI and in animals with electrolyte disturbance, suggesting that it may be clinically useful in the continuous measurement of oxygen partial pressure.     

Nitroprusside therapy in acute and chronic coronary heart disease

To elucidate the effects of nitroprusside on the relations between systemic pressure, coronary blood flow and regional myocardial ischemia, dogs were subjected to constriction of the proximal left anterior descending (LAD) artery to induce ischemia determined by intramyocardial S-T segments and intramyocardial mass spectrometric oxygen tension (PO₂) and carbon dioxide tension (PCO₂). Nitroprusside was infused to incrementally lower mean blood pressure from 137 to 62 mm Hg. A decrease in mean blood pressure to 87 mm Hg lowered (p < 0.05) intramyocardial S-T segment elevations and diminished left ventricular filling pressure, but it did not alter (p > 0.05) poststenotic flow in the LAD artery, intramyocardial PCO₂ and PO₂, and cardiac oxygen uptake. With a further decrease in systemic arterial blood pressure below normal, S-T segments rose, LAD artery flow decreased, intramyocardial PCO₂ increased and intramyocardial PO₂ decreased. In addition, 12 patients with acute anterior infarction had 35-lead S-T segment maps before and after a 10 minute infusion of nitroprusside. Heart rate was unchanged, left ventricular pressure decreased from 139/19 to 115/11 mm Hg (p < 0.01), cardiac index was maintained, S-T segment sum was lowered from 42 to 29 mm (p < 0.001) and mean S-T segment elevation declined from 1.6 to 1.2 mm/lead (p < 0.001). Thus, modest nitroprusside-induced reduction in blood pressure has beneficial effects on multiple indices of experimental and clinical regional ischemia. In contrast, a further decrease in blood pressure below normal lowers poststenotic coronary blood flow and thereby ischemia worsens.     

End-tidal estimates of arterial PCO2 for cardiac output measurement by CO2 rebreathing: A study in patients with cystic fibrosis and healthy controls

We set out to determine the effects of various estimates of arterial PCO₂ (PaCO₂) on calculation of cardiac output (Q) by the indirect Fick (CO₂) method in healthy children and children with cystic fibrosis (CF), and to develop a prediction equation for children for PaCO₂, based on end-tidal PCO₂ (PetCO₂). The study had 3 parts: 1) Twenty-three healthy children exercised lightly and moderately while arterialized capillary blood gases and PetCO₂ were measured simultaneously so that a prediction equation for PaCO₂ could be derived from PetCO₂. Cardiac output was measured by CO₂ rebreathing at each workload; different values for PaCO₂ (measured in arterialized capillary blood, end-tidal, and PaCO₂ derived from the Bohr equation assuming normal dead space) were used to calculate Q; 2) our equation PaCO₂ = 0.647 PetCO₂ + 12.4 was tested prospectively to measure Q in 9 healthy children; and 3) cardiac output based on arterialized capillary PaCO₂ was compared with that based on Jones-corrected PetCO₂ during light and moderate exercise in 16 CF patients whose forced expiratory volume in 1 second (FEV₁) range from normal to 37% predicted. Our results have shown that in health children end tidal based-estimates of PaCO₂ tended to overestimate Q, whereas PaCO₂ values derived by the Bohr equation and assuming normal dead space tended to underestimate Q, compared with Q calculated from directly measured PaCO₂. Our prediction equation resulted in good agreement compared with directly measured PaCO₂ when used to calculate Q (mean difference, +1.3%; range, +9% to −13%). CF patients with little or no airway obstruction had results similar to healthy controls, but those with severe airway obstruction had lower values for Q when PetCO₂ was used instead of directly measured PaCO₂. We conclude that estimates of PaCO₂ from PetCO₂ are not reliable in patients with moderately severe pulmonary disease due to CF. In healthy children, the prediction equation for PaCO₂ from PetCO₂ derived in the present study gives results superior to other bloodless methods currently in use for computation of Q by the indirect Fick (CO₂) method. Pediatr Pulmonol. 1996; 22:154–160. © 1996 Wiley-Liss, Inc.     

Safety and efficacy of carbon dioxide insufflation during gastric endoscopic submucosal dissection

AIM: To compare the safety and efficacy of carbon dioxide (CO₂) and air insufflation during gastric endoscopic submucosal dissection (ESD).METHODS: This study involved 116 patients who underwent gastric ESD between January and December 2009. After eliminating 29 patients who fit the exclusion criteria, 87 patients, without known pulmonary dysfunction, were randomized into the CO₂ insufflation (n = 36) or air insufflation (n = 51) groups. Standard ESD was performed with a CO₂ regulation unit (constant rate of 1.4 L/min) used for patients undergoing CO₂ insufflation. Patients received diazepam for conscious sedation and pentazocine for analgesia. Transcutaneous CO₂ tension (PtcCO₂) was recorded 15 min before, during, and after ESD with insufflation. PtcCO₂, the correlation between PtcCO₂ and procedure time, and ESD-related complications were compared between the two groups. Arterial blood gases were analyzed after ESD in the first 30 patients (12 with CO₂ and 18 with air insufflation) to assess the correlation between arterial blood CO₂ partial pressure (PaCO₂) and PtcCO₂.RESULTS: There were no differences in respiratory functions, median sedative doses, or median procedure times between the groups. Similarly, there was no significant difference in post-ESD blood gas parameters, including PaCO₂, between the CO₂ and air groups (44.6 mmHg vs 45 mmHg). Both groups demonstrated median pH values of 7.36, and none of the patients exhibited acidemia. No significant differences were observed between the CO₂ and air groups with respect to baseline PtcCO₂ (39 mmHg vs 40 mmHg), peak PtcCO₂ during ESD (52 mmHg vs 51 mmHg), or median PtcCO₂ after ESD (50 mmHg vs 50 mmHg). There was a strong correlation between PaCO₂ and PtcCO₂ (r = 0.66; P < 0.001). The incidence of Mallory-Weiss tears was significantly lower with CO₂ insufflation than with air insufflation (0% vs 15.6%, P = 0.013). CO₂ insufflation did not cause any adverse events, such as CO₂ narcosis or gas embolisms.CONCLUSION: CO₂ insufflation during gastric ESD results in similar blood gas levels as air insufflation, and also reduces the incidence of Mallory-Weiss tears.     

Extreme hypocapnia in the critically ill patient

Respiratory alkalosis was the most common acid-base disturbance observed in a computer analysis of 8,607 consecutive arterial blood gas studies collected over an 18 month period in a large intensive care unit.Through a retrospective review of the randomly selected hospital records of 114 patients, we defined four groups based upon arterial carbon dioxide tension (PaCO₂) and mode of ventilation. Group 1, with a PaCO₂ of 15 mm Hg or less, consisted of 25 patients with an over-all mortality of 88 per cent. Group II, with a PaCO₂ of 20 to 25 mm Hg, consisted of 35 patients with a mortality of 77 per cent. Group III, with a PaCO₂ of 25 to 30 mm Hg, consisted of 33 patients with a mortality of 73 per cent, and Group IV, with a PaCO₂ of 35 to 45 mm Hg, consisted of 21 patients with a mortality of 29 per cent (p <0.001). Shock and sepsis were most common in group I patients.These findings suggest that extreme hypocapnia in the critically ill patient has serious prognostic implications and is indicative of the severity of the underlying disease.     

Prostaglandin E2 and aggressive factors increase the gland luminal pressure in the rat gastric mucosa in vivo

Background & Aims: The gastroprotective properties of prostaglandins in low concentrations are still unclear. In this study, we investigated the effects of prostaglandin E₂ (PGE₂), indomethacin, and intraluminally applied HCl or ethanol on intraglandular pressure, mucus thickness, acid secretion, and gastric mucosal blood flow. Methods: Glandular pressure and mucous gel thickness were measured with microelectrodes during intravital microscopy in thiobutabarbital sodium–anesthetized rats. Gastric blood flow was measured with laser Doppler flowmetry. Results: In pentagastrin-treated rats, glandular pressure increased significantly in response to topical (1 μg/mL) or intra-arterial (12 μg · kg⁻¹ · h⁻¹) PGE₂ from approximately 17 to 69 and 18 to 57 mm Hg, respectively, whereas blood flow, mucus thickness, and acid secretion were unaltered. Indomethacin (3 mg/kg intravenously) significantly decreased glandular pressure from approximately 20 to 11 mm Hg. Intraluminal application of 10 and 100 mmol/L HCl or 20% and 40% ethanol significantly increased glandular pressure but had no effect after indomethacin pretreatment. Conclusions: Endogenous PGE₂ is important for maintaining a high glandular pressure, and exogenous PGE₂ potently increases glandular pressure at concentrations not altering blood flow, mucus thickness, or acid secretion. This suggests that high intraglandular pressures might be involved in gastroprotection.GASTROENTEROLOGY 1998;114:1276-1286     

Serial Measurements of Arterial Oxygen Tension are Associated with Mortality in COPD

Background: Knowledge on factors associated with mortality can help identify patients with COPD that might benefit from close monitoring and intervention. Arterial blood gases (ABGs) are related to mortality, but both arterial tension of oxygen (PaO₂) and arterial tension of carbon dioxide (PaCO₂) vary over time. The aim of our study was to investigate the association between repeatedly measured ABGs and mortality in men and women with COPD. Methods: A cohort of 419 Norwegian subjects with COPD, GOLD stage II-IV, aged 40–75, was followed up with up to seven ABGs, measured during stable phase for three years. Cox proportional hazard models were used to quantify the relationship between both single and repeatedly measured ABGs and all-cause mortality after five years, adjusting for age, sex, and the updated BODE index. Results: A total of 64 subjects died during follow-up. Mean initial arterial oxygen tension (standard deviation) was significantly higher in survivors compared to deceased, with PaO₂ (in kPa) 9.4 (1.1) versus 8.8 (1.2), p<0.001. Corresponding numbers for PaCO₂ were 5.3 (0.5) and 5.5 (0.7), p < 0.001. In analyses adjusting for age, sex, and the updated BODE index hazard ratios – HR(95% confidence intervals) - for all-cause mortality were 0.73 (0.55, 0.97) and 1.58 (0.90, 2.76) for repeated measures of PaO₂ and PaCO₂, respectively. Conclusion: Both arterial oxygen and carbon dioxide tension were related to mortality in this study, and arterial oxygen tension added prognostic information to the updated BODE index in COPD.     

The effect of high-frequency oscillatory ventilator combined with pulmonary surfactant in the treatment of neonatal respiratory distress syndrome

Objective:To investigate the efficacy of high-frequency oscillatory ventilation (HFOV) combined with pulmonary surfactant (PS) in the treatment of neonatal respiratory distress syndrome (NRDS).Methods:This study is a retrospective clinical study. Seventy-two NRDS neonates were selected as the subjects from November 2019 to November 2020, and divided into observation group (40 cases, HFOV treatment) and control group (32 cases, conventional mechanical ventilation treatment). All cases were treated with PS and comprehensive treatment. The therapeutic effect, arterial partial pressure of oxygen (PaO₂), arterial partial pressure of carbon dioxide (PaCO₂), Percentage of inhaled oxygen concentration (FiO₂), mean arterialpressure, oxygenation index (OI), and complications were compared in the 2 groups.Results:The total effective rate of the observation group was 90.0%, significantly higher than that of the control group. After treatment, the observation group has higher PaO₂ levels and lower levels of PaCO₂, mean arterial pressure, FiO₂, and OI than the control group. There was no significant difference in the incidence of complications between the 2 groups.Conclusion:HFOV combined with PS has a significant effect on NRDS, which can improve the arterial blood gas index without increasing the incidence of complications.     

Arteriolar Contribution to Microcirculatory CO2/O2 Exchange

The role of arterioles and capillaries in microcirculatory gas exchange was evaluated using a multicompartmental model for O₂-CO₂ transport in the rat skeletal microcirculation. Model predictions were examined to investigate the effects of model formulation and model parameter values. The factors in model formulation included radial blood diffusion resistance, the discrete nature of capillary blood, and the method of determining compartmental fluxes. A comparison with earlier models in the literature indicated that, by refining the method for determining compartmental fluxes, the CO₂ flux contribution ratio of arterioles versus capillaries (F_a/F_c) increased by 52% during rest and diminished by 34% during moderate exercise. It also resulted in negative venular fluxes during exercise. Incorporating radial blood diffusion resistance into the model lead to a decrease of up to 43% in F_a /F_c. It also resulted in a decrease in central arteriole-venule shunt. Including the discrete nature of capillary blood into the model caused a small increase in F_a /F_c. Results indicated similar effects of these factors on oxygen F_a/F_c. Model parameters whose effects were investigated included metabolic rate (M), blood flow rate (Q), ratio of arteriolar diffusion conductance versus capillary diffusion conductance (E_a/E_c), the magnitude of arteriolar diffusion conductances (E_a), and the CO₂/O₂ respiratory quotient (Qu). Simulation results suggested that Q was a major factor responsible for the variations in F_a /F_c when the rest/exercise state of rat skeletal muscle changes. E_a and Qu were also responsible for differences in model predictions for different body organs or animal species. Our model predicts capillary dominance in both CO₂ and O₂ exchange and reveals the existence, under certain conditions, of negative venular flux contribution.     

The influence of fresh gas flow and inspiratory/expiratory ratio on tidal volume and arterial CO2 tension in mechanically ventilated surgical patients

The relative importance of fresh gas flow and inspiretory/expiratory ratio in determining delivered tidal volume and PaCO₂ was studied in anesthetized adult patients ventilated with a fixed ventilator bellows volume. The fresh gas flows studied were 2, 6, and 10 L/min, and inspiratory/expiratory ratio was either 1:2 or 1:4.5. Bellows volume and respiratory rate were held constant throughout the study. At the lowest fresh gas flow and smallest inspiratory/expiratory ratio, PaCO₂ was 43 ± 2 mm Hg. The PaCO₂ decreased progressively and significantly with each increase in fresh gas flow during ventilation with either inspiratory/expiratory ratio setting. PaCO₂ averaged 30 ± 3 during ventilation with the highest fresh gas flow and largest inspiratory/expiratory ratio. As fresh gas flow increased, PaCO₂ and tidal volume changed to a significantly greater degree in response to changes in inspiratory/expiratory ratio. These data demonstrate that altering either fresh gas flow or inspiratory/expiratory ratio can produce clinically significant perturbations in PaCO₂ and tidal volume during anesthesia. These perturbations occur even if bellows volume is held constant. Furthermore, changes in inspiratory/expiratory ratio will affect these parameters to a greater degree as fresh gas flow is increased.     

Blood gas and acid-base balance during cardiopulmonary resuscitation by intrathroacic and abdominal pressure variations

Summary The blood gases and acid-base balance in a modified cardiopulmonary resuscitation (CPR) technique, based on intrathoracic and abdominal pressure variations by means of circumferential chest and abdominal balloon inflation, were examined in seven mongrel dogs. CPR proceeded for pcriods lasting 30 min or more and was monitored by measurements of aortic and right ventricular pressures and carotid blood flow during the compression (artificial systole) and the relaxation phase (artificial diastole). The carotid blood flow was 21.7±7.8 (mean±SD) ml/min, which was 0.18±0.6 (mean±SD) of the baseline mean carotid flow. Arterial blood was well oxygenated throughout the experiments, and low PCO₂ levels (5–9 mm Hg) caused an initial severe alkalosis (pH=7.94). However, a gradual decline in the pH was observed, reaching a value of 7.34±0.11 in the arterial blood after 30 min of CPR. The venous blood had a very low oxygen content (less than 25.5%) with a low PO₂ and a normal PCO₂ (43.7±7.3 mm Hg) throughout the experiment. A gradually developing metabolic acidosis was reflected in the pH values, and an increase in base deficit from 2.25±5.6 meq/1 prior to CPR to 16.7±3.2 meq/1 after 30 min of CPR was observed. High arteriovenous differences in oxygen content (greater than 66.4%) and CO₂ tension (30.1–41.5 mm Hg) with a slowly developing metabolic acidosis were noted. Thus, CPR by thoracic and abdominal pressure variations is associated with a slowly developing metabolic acidosis which is the result of the combination of hyperventilation and a low perfusion state.R. J. Matas-Winnipeg, Professor of Biomedical Engineering     

Randomized Pilot Trial Between Prostaglandin I2 Analog and Anti‐Platelet Drugs on Peripheral Arterial Disease in Hemodialysis Patients

The effect of the prostaglandin I₂ analog, beraprost sodium (BPS), on hemodialysis (HD) patients with peripheral arterial disease (PAD) has not been fully elucidated. The effect of BPS was compared to that of PAD drugs in HD patients with PAD in a multicenter randomized prospective interventional pilot study (J‐PADD). Seventy‐two PAD patients on HD were entered and randomly divided into two groups; that is, BPS group (Group A: n = 35) and PAD drug (cilostazol or sarpogrelate) group (Group B: n = 37). Primary endpoint was changes in skin perfusion pressure (SPP). Kidney Disease Quality of Life (KDQOL) score, cardiovascular events, PAD events, and adverse events were also evaluated. SPP increased significantly in both groups at 24 weeks from their basal levels. The absolute increase of SPP in Group A and Group B were 15.4 ± 30.0 mm Hg (P < 0.0001) and 20.2 ± 22.1 mm Hg (P = 0.025) (instep), and 13.8 ± 19.3 mm Hg (P < 0.0001) and 9.2 ± 16.3 mm Hg (P = 0.041) (sole), respectively. Changes of KDQOL score showed significantly better result in the role of physical score in Group A compared with Group B. Although heart rate was unchanged in Group A, 9.3/min increase was seen in Group B patients who received cilostazol. There was no intergroup difference in cardiovascular events and/or PAD events between the two groups during the study period. This exploratory pilot study suggested BPS was as effective as anti‐platelet drugs in improving microcirculation in HD patients.     

Lipoprotein-Associated Phospholipase A2 (Lp-PLA2) in Acute Coronary Syndrome: Relationship With Low-Density Lipoprotein Cholesterol

Background

Lipoprotein-associated phospholipase A₂ (Lp-PLA₂) might play a role in the formation of vulnerable atherosclerotic plaques. Its plasma distribution and mass in subjects with acute coronary syndrome (ACS) has yet to be characterized.

Methods

We compared plasma levels of Lp-PLA₂ in 24 patients within 48 hours of an ACS (acute) and 12 weeks after (recovery), in 26 patients with stable coronary artery disease and in 10 normal healthy control subjects. Lp-PLA₂ mass was determined using enzyme-linked immunosorbent assay.

Results

The ACS patients (mean age 57 ± 8.7 years) had high-sensitivity C-reactive protein (hsCRP) levels of 30.46 ± 57.57 mg/L (ACS acute) vs 1.69 ± 1.32 mg/L (ACS recovery). Plasma Lp-PLA₂ levels were significantly higher in ACS acute subjects than in ACS recovery subjects (143.13 ± 60.88 ng/mL vs 88.74 ± 39.12 ng/mL; P < 0.0001). Interestingly, stable coronary artery disease patients had higher Lp-PLA₂ levels than ACS recovery patients (121.72 ± 31.11 ng/mL vs 88.74 ± 39.12 ng/mL; P = 0.0018). There was a strong correlation between Lp-PLA₂ and low-density lipoprotein (LDL) cholesterol (LDL-C) (r = 0.709; P < 0.0001) or changes in LDL (r = 0.449; P = 0.027), suggesting that the major determinant of plasma Lp-PLA₂ is LDL-C. No significant correlations were observed between Lp-PLA₂ and hsCRP or high-density lipoprotein (HDL) cholesterol. When separated using high-performance liquid chromatography, > 65%-70% of Lp-PLA₂ mass was within the apolipoprotein B-containing lipoprotein fraction, with approximately 30%-35% on HDL fraction, with no significant change in distribution between ACS acute and recovery.

Conclusions

Subjects with an ACS have markedly increased Lp-PLA₂ levels acutely related to LDL-C levels.     

Different Alleles Cause an Imbalance in A2 and A2B Phenotypes of the ABO Blood Group

Background and Objectives : In several populations, including the Japanese, the frequency of the A₂B phenotype is significantly higher than expected based on the A₂ phenotype frequency. To understand the genetic basis of this ‘excess’ of A²B, we examined ABO alleles in individuals with A₂-related phenotypes. Materials and Methods : ABO alleles were identified by means of polymerase chain reaction single-strand conformation polymorphism (SSCP) and nucleotide sequence analyses. Results : The frequencies of A₂-related alleles (*A105, *A106, *A107, *A111 and *R101) were clearly different between the A₂ and A₂B phenotypes. In particular, a putative recombinant allele, *R101, was uncommon in the A₂ but common in the A₂B phenotype individuals. This allele was also detected in 4 of 401 (1%) unrelated A₁ phenotype (AO genotype) individuals. Conclusion : *R101 is presumably expressed as phenotype A₁ in *R101/*O heterozygous individuals, but as phenotype A₂ in *R101/*B heterozygotes, thus giving rise to a high A₂B phenotype frequency.     

Simultaneous Compared With Sequential Blood Pressure Measurement Results in Smaller Inter‐Arm Blood Pressure Differences

There are currently few recommendations on how to assess inter‐arm blood pressure (BP) differences. The authors compared simultaneous with sequential measurement on mean BP, inter‐arm BP differences, and within‐visit reproducibility in 240 patients stratified according to age (<50 or ≥60 years) and BP (<140/90 mm Hg or ≥140/90 mm Hg). Three simultaneous and three sequential BP measurements were taken in each patient. Starting measurement type and starting arm for sequential measurements were randomized. Mean BP and inter‐arm BP differences of the first pair and reproducibility of inter‐arm BP differences of the first and second pair were compared between both methods. Mean systolic BP was 1.3±7.5 mm Hg lower during sequential compared with simultaneous measurement (P<.01). However, the first sequential measurement was on average higher than the second, suggesting an order effect. Absolute systolic inter‐arm BP differences were smaller on simultaneous (6.2±6.7/3.3±3.5 mm Hg) compared with sequential BP measurement (7.8±7.3/4.6±5.6 mm Hg, P<.01 for both). Within‐visit reproducibility was identical (both r=0.60). Simultaneous measurement of BP at both arms reduces order effects and results in smaller inter‐arm BP differences, thereby potentially reducing unnecessary referral and diagnostic procedures.