Central Venous Blood Samples Research Articles

COMPARAÇÃO ENTRE OS MÉTODOS LABORATORIAL E PORTÁTIL NA ANÁLISE DA GLICEMIA EM FELINOS COM AMOSTRAS DE SANGUE VENOSO CENTRAL E CAPILAR

The objective of this study was to compare the efficacy of portable blood glucose measurement method in relation to the laboratory reference method, using central venous and capillary blood samples from 20 cats. The value obtained by the laboratory method using central venous blood sample was considered as the standard reference value. Other two values were obtained from the portable blood glucose meter, in which a sample from the same central venous blood and another one sample from capillary blood were used. For the 20 cats, the blood glucose results obtained by the laboratory method had an average of 80mg/dL; and the results found by the glucometer had an average of 84.1mg/dL with central venous blood and of 73.1mg/dL with capillary blood. The glycemic averages obtained by the glucometer with both blood samples compared to that achieved by the laboratory method resulted in variations below the maximum established (20%) by associations that regulate portable glucometers and by the organization for standardization, as well as the variation between the glycemic averages obtained by the glucometer using different blood samples. In the comparative analysis, there was no significant difference between the methods (p<0.05). In conclusion, the portable glucometer is effective in measuring blood glucose in cats, both from central venous blood and capillary blood samples. Keywords: cat, glucometer, glucose, measurement.

Effect of dexmedetomidine on intestinal mucosal injury in patients undergoing cardiac valve replacement with CPB

Objective To evaluate the effect of dexmedetomidine on the intestinal mucosal injury in the patients undergoing cardiac valve replacement with cardiopulmonary bypass (CPB). Methods Forty patients of both sexes with rheumatic heart disease, aged 32-64 yr, weighing 40-75 kg, of ASA physical status Ⅱ or Ⅲ(NYHA class Ⅱ or Ⅲ), scheduled for elective cardiac valve replacement with CPB, were randomly divided into 2 groups (n=20 each) using a random number table: control group (group C) and dexmedetomidine group (group D). After induction of anesthesia, the patients were endotracheally intubated and mechanically ventilated. Anesthesia was maintained with 0.8%-2.0% sevoflurane inhalation and intermittent iv boluses of sufentanil 0.5-1.0 μg/kg and vecuronium 0.04-0.06 mg/kg. Before routine induction of anesthesia, a loading dose of dexmedetomidine 1 μg/kg was injected intravenously over 10 min, followed by continuous infusion at 0.3 μg·kg-1·h-1 until the end of surgery in group D, while the equal volume of normal saline was given in group C. Before CPB, at 30 min after aortic clamping, at the termination of CPB, at the end of surgery and at 6 and 24 h after surgery, central venous blood samples were taken for determination of concentrations of tumor necrosis factor-alpha, interleukin-6(IL-6) and IL-10 and intestinal fatty acid binding protein in plasma (by ELISA), and the plasma concentration of endotoxin (using turbidimetry). The time of postoperative mechanical ventilation and duration of ICU stay were recorded. Results Compared with group C, the concentrations of tumor necrosis factor-alpha, IL-6, IL-10 and endotoxin and intestinal fatty acid binding protein in plasma were significantly decreased, and the time of postoperative mechanical ventilation and duration of ICU stay were shortened in group D. Conclusion Dexmedetomidine infused continuously at 0.3 μg·kg-1·h-1(until the end of surgery) after a loading dose of 1 μg/kg before routine induction of anesthesia can reduce intestinal mucosal injury in the patients undergoing cardiac valve replacement with CPB. Key words: Dexmedetomidine; Cardiopulmonary bypass; Intestinal mucosa; Heart valve prosthesis implantation

Challenges of inpatient blood glucose monitoring: standards, methods, and devices to measure blood glucose.

Glucose control in the hospital setting is very important. There is a high incidence of hyperglycemia, hypoglycemia, and glycemic variability in hospitalized patients. Safe insulin delivery and glucose control is dependent on reliable glucose meters and monitoring systems in the hospital. Different glucose monitoring systems use arterial, venous, central venous, and capillary blood samples. It is important for clinicians to be aware that there are limitations of specific point-of-care (POC) glucose meters and that situations exist whereby POC glucose meters as the sole measurement device should be avoided. POC meter devices are not approved by the Food and Drug Administration for use in critical care, although POC meter devices are commonly used in critical care settings and elsewhere. This review focuses on glucose assay principles, instrument technology, influences on glucose measurement, standards for glucose measurement, and an evaluation of different methods to measure blood glucose in the hospital setting.

Patterns of central venous oxygen saturation, lactate and veno-arterial CO 2 difference in patients with septic shock

Background and Aims:Tissue hypoperfusion is reflected by metabolic parameters such as lactate, central venous oxygen saturation (ScvO2) and the veno-arterial CO2 (vaCO2) difference. We studied the relation of these parameters over time and with outcome in patients with severe septic shock.Materials and Methods:In this single-center, prospective observational cohort study, adult patients (≥18 years) with circulatory shock were included. Echocardiography and simultaneous arterial and venous blood gases were done on enrolment (0 h) and at 24, 48 and 72 h. The partial pressure of CO2, lactate and ScvO2 were recorded from the central venous blood samples. The vaCO2 was calculated as the difference in CO2 between paired venous and arterial blood gas samples.Results:Of the 104 patients with circulatory shock, 79 patients (44 males) with septic shock aged 49.8 (standard deviation ± 14.6) years and with sequential organ failure assessment (SOFA) score of 11.0 ± 3.4 were included. 71 patients (89.9%) were ventilated (11.4 ± 12.3 ventilator-free days). The duration of hospitalization was 16.6 ± 12.8 days and hospital mortality 50.6%. Lactate significantly decreased over time with a greater decrement in survivors than nonsurvivors (−0.35 vs. −0.10, P < 0.001). For every l/min increase in cardiac output, vaCO2 decreased by 0.34 mmHg (P = 0.006). There was no association between ScvO2 and mortality (P = 0.930). 0 h SOFA and vaCO2 ≤6 mmHg were strongly associated (P = 0.005, P = 0.018, respectively) with higher odds of mortality. However, this association was evident only in those with ScvO2 >70% and not in ScvO2 ≤70%.Conclusion:In septic shock, vaCO2 ≤6 mmHg is independently associated with mortality, particularly in those with normalized ScvO2 consistent with metabolic microcirculatory abnormalities in these patients.

Repeatability of blood gas parameters, PCO2 gap, and PCO2 gap to arterial-to-venous oxygen content difference in critically ill adult patients.

The objective of this study was to examine the repeatability of blood gas (BG) parameters and their derived variables such as the central venous-to-arterial carbon dioxide tension difference (▵PCO2) and the ratio of ▵PCO2 over the central arteriovenous oxygen content difference (▵PCO2/C(a-cv)O2) and to determine the smallest detectable changes in individual patients.A total of 192 patients with arterial and central venous catheters were included prospectively. Two subsequent arterial and central venous blood samples were collected immediately one after the other and analyzed using the same point-of-care BG analyzer. The samples were analyzed for arterial and venous BG parameters, ▵PCO2, and ▵PCO2/C(a-cv)O2 ratio. Repeatability was expressed as the smallest detectable difference (SDD) and the least significant change (LSC). A change in value of these parameters exceeding the SDD or the LSC should be regarded as real.The SDDs for arterial carbon dioxide tension, arterial oxygen saturation, central venous oxygen saturation (ScvO2), and ▵PCO2 were small: ±2.06 mm Hg, ±1.23%, 2.92%, and ±1.98 mm Hg, respectively, whereas the SDDs for arterial oxygen tension (PaO2) and ▵PCO2/C(a-cv)O2 were high: ±9.09 mm Hg and ±0.57 mm Hg/mL, respectively. The LSCs (%) for these variables were 5.06, 1.27, 4.44, 32.4, 9.51, and 38.5, respectively.The repeatability of all these variables was good except for PaO2 and ▵PCO2/C(a-cv)O2 ratio for which we observed an important inherent variability. Expressed as SDD, a ScvO2 change value of at least ±3% should be considered as true. The clinician must be aware that an apparent change in these variables in an individual patient might represent only an inherent variation.

Central venous blood gas and acid-base status in conscious dogs and cats.

To determine the reference level of central venous oxygen saturation (ScvO2) and clinical efficacy of central venous blood gas analysis, partial pressures of oxygen and carbon dioxide, pH, oxygen saturation, base excess (B.E.) and HCO3 concentration were compared between simultaneously obtained central venous and arterial blood samples from conscious healthy 6 dogs and 5 cats. Comparisons between arteriovenous samples were performed by a paired t-test and Bland-Altman analysis. Between arteriovenous samples, B.E. showed good agreement, but there were significant differences in other parameters in the dogs, and no good agreement was detected in cats. The ScvO2 in dogs and cats were 82.3 ± 3.5 and 62.4 ± 13.5%, respectively. Central venous blood gas analysis is indispensable, especially in cats.

The feasibility and applications of non-invasive cardiac output monitoring, thromboelastography and transit-time flow measurement in living-related renal transplantation surgery: results of a prospective pilot observational study.

IntroductionDelayed graft function (DGF) remains a significant and detrimental postoperative phenomenon following living-related renal allograft transplantation, with a published incidence of up to 15%. Early therapeutic vasodilatory interventions have been shown to improve DGF, and modifications to immunosuppressive regimens may subsequently lessen its impact. This pilot study assesses the potential applicability of perioperative non-invasive cardiac output monitoring (NICOM), transit-time flow monitoring (TTFM) of the transplant renal artery and pre-/perioperative thromboelastography (TEG) in the early prediction of DGF and perioperative complications.MethodsTen consecutive living-related renal allograft recipients were studied. Non-invasive cardiac output monitoring commenced immediately following induction of anaesthesia and was maintained throughout the perioperative period. Doppler-based TTFM was performed during natural haemostatic pauses in the transplant surgery: immediately following graft reperfusion and following ureteric implantation. Central venous blood sampling for TEG was performed following induction of anaesthesia and during abdominal closure.ResultsA single incidence of DGF was seen within the studied cohort and one intra-operative (thrombotic) complication noted. NICOM confirmed a predictable trend of increased cardiac index (CI) following allograft reperfusion (mean CI - clamped: 3.17 ± 0.29 L/min/m2, post-reperfusion: 3.50 ± 0.35 L/min/m2; P < 0.05) mediated by a significant reduction in total peripheral resistance. Reduced TTFM at the point of allograft reperfusion (227 ml/min c.f. mean; 411 ml/min (95% CI: 358 to 465)) was identified in a subject who experienced intra-operative transplant renal artery thrombosis. TEG data exhibited significant reductions in clot lysis (LY30 (%): pre-op: 1.0 (0.29 to 1.71), post reperfusion 0.33 (0.15 to 0.80); P = 0.02) and a trend towards increased clot initiation following allograft reperfusion.ConclusionsReduced renal arterial blood flow (falling without the 95% CI of the mean), was able to accurately predict anastomotic complications within this pilot study. TEG data suggest the emergence of a prothrombotic state, of uncertain clinical significance, following allograft reperfusion. Abrogation of characteristic haemodynamic trends, as determined by NICOM, following allograft reperfusion may permit prediction of individuals at risk of DGF. The findings of this pilot study mandate a larger definitive trial to determine the clinical applications and predictive value of these technologies.

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

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

Prognostic value of lactate clearance in severe community acquired pneumonia

IntroductionSevere community acquired pneumonia (SCAP) occurs in approximately 18–36% of all CAP and the mortality rate could be as high as 67% in patients with SCAP. Several studies have described a correlation between baseline lactate concentration and mortality of ICU patients. Aim of the workTo follow lactate clearance after admission for 24h which could be an indicator of outcome in severe community acquired pneumonia. Patients and methodsForty-six consecutively admitted adult patients were diagnosed as severe community acquired pneumonia. Lactate was measured at the time of admission (H0), reassessment of lactate level was done after 8h and also another lactate measurement done after 24h. In a trial to follow the guideline for management and to optimize oxygen delivery (DO2) and reach a ScvO2⩾70%, ScvO2 was measured through a central venous blood sample done at the same time with lactate. During the study resuscitation by inotropic medications and patient’s physiological parameters were measured routinely. All data needed to calculate the Acute Physiology and Chronic Health Evaluation (APACHE II) score were recorded. ResultsMost of patients in the current study were above the age of 60years. Twenty-five patients had lactate clearance of more than 40%, those patients were included in group 1, whereas 21 had lactate clearance of 40% or less and they were included in group II. There was no significant difference in the age and sex distribution between both groups. Out of 21 patients included in group II, inotropic drugs were used in 8 patients (38%), whereas there was one patient only in group 1. The rate of intubation in addition to the mean APACHE II score and ICU length of stay was significantly higher in group II compared to group I. Over the first 24h three readings for mixed venous oxygen were recorded and included in the analysis. The reading of mixed venous oxygen recorded after 24h of ICU admission was significantly high in group 1. All indices of blood lactate clearance over the first 24h were higher in group 1 compared to group II, however it was only significantly high after 24h (p-value 0.01). ConclusionOur study suggests that lactate clearance could be used as a useful biomarker which is inexpensive and a reliable predictor of patient outcome in critically ill patients admitted to ICU with severe community-acquired pneumonia.

Blood transfusion and oxygen extraction ratio in patients admitted to the general intensive care unit: A quasi experimental study

Blood transfusion is commonly undertaken in critically ill patients; and studies have suggested the use of oxygen extraction ratio (O 2 ER) as an additional transfusion trigger in critically ill patients. The aim of this study was to establish the relationship between blood transfusion and oxygen extraction ratio in adult patients admitted to the general intensive care unit, using central venous oxygen saturation instead of mixed venous oxygen saturation. Arterial and central venous blood samples were drawn and a blood gas analysis immediately before commencement of blood transfusion was undertaken. At least 15 min after completion of the transfusion, similar samples were drawn and the blood gas analysis was repeated. The O 2 ER before and after transfusion was then calculated. Using paired student’s t -test, we checked whether the mean difference between the two O 2 ERs was statistically significant. We enrolled 58 patients in the study, the mean (±SD) haemoglobin concentration before transfusion was 7.38 g/dl (±1.71). The mean change in haemoglobin concentration following blood transfusion was 2.29 g/dl (±1.18), after transfusing an average of 1.95 (±0.83) units of packed cells. Mean O 2 ER was 0.27 (±0.11) before, and 0.25 (±0.12) after RBC transfusion. The mean change in O 2 ER was −0.018 SD ± 0.10 (95% CI, −0.043–0.007; P = 0.15). Linear regression analysis showed no statistically significant relationship between change in haemoglobin concentration and change in O 2 ER; p -value = 0.12. The change in oxygen extraction ratio was not statistically significant following blood transfusion in adult patients admitted to the general ICU at a tertiary teaching hospital. Further studies are required especially in patients with increased pre transfusion O 2 ER to evaluate the usefulness of this measurement as a possible transfusion trigger. La transfusion sanguine est effectuée de façon courante chez les patients en état critique ; et des études ont suggéré l’utilisation du ratio d’extraction de l’oxygène (REO 2 ) comme déclencheur supplémentaire d’une transfusion chez les patients en état critique. Le but de cette étude était de déterminer le lien entre transfusion sanguine et ratio d’extraction de l’oxygène chez les patients adultes admis en unité de soins intensifs généraux en utilisant la saturation veineuse centrale en oxygène au lieu de la saturation veineuse mixte en oxygène. Des échantillons sanguins artériels et veineux centraux ont été prélevés et une analyse des gaz du sang a été effectuée juste avant le commencement de la transfusion sanguine. Au moins 15 min après l’achèvement de la transfusion, des échantillons similaires ont été prélevés et l’analyse des gaz du sang à nouveau effectuée. Le REO 2 avant et après la transfusion a ensuite été calculé. En utilisant des tests de Student appariés, nous avons vérifié si la différence moyenne entre les deux REO 2 était statistiquement significative. Nous avons inclus 58 patients dans l’étude, le taux moyen (±écart-type) d’hémoglobine avant la transfusion était de 7.38 g/dl (±1.71). Le changement moyen de taux d’hémoglobine à la suite de la transfusion sanguine était de 2.29 g/dl (±1.18), après avoir transfusé une moyenne de 1.95 (±0.83) unités de globules concentrés. Le REO 2 moyen était de 0.27 (±0.11) avant, et de 0.25 (±0.12) après la transfusion de globules rouges. Le changement moyen de REO 2 était de −0.018, l’écart-type de ±0.10 (intervalle de confiance de 95%, −0.043–0.007; P = 0.15). Une analyse de régression linéaire n’a montré aucun lien statistiquement significatif entre le changement du taux d’hémoglobine et le changement de REO 2 ; p = 0.12. Le changement du ratio d’extraction de l’oxygène suite à une transfusion sanguine n’était pas statistiquement significatif chez les patients adultes admis aux soins intensifs généraux dans un centre hospitalier universitaire. Des études supplémentaires sont nécessaires surtout chez les patients dont le REO 2 avant la transfusion a augmenté afin d’évaluer l’utilité de cette mesure comme déclencheur possible d’une transfusion.

Analysis: New Point-of-Care Blood Glucose Monitoring System for the Hospital Demonstrates Satisfactory Analytical Accuracy Using Blood from Critically Ill Patients—An Important Step toward Improved Blood Glucose Control in the Hospital

Patients managed in the intensive care units (ICUs) and general wards of the hospital experience a high incidence of hyperglycemia, hypoglycemia, and glycemic variability, despite significant hospital resources devoted to glucose control. Optimized glucose meters and monitoring systems are required to improve the safety and efficacy of insulin delivery and glucose control in the hospital. Safe insulin dosing requires timely and accurate glucose measurements, especially during dynamic changes in nutrition, insulin sensitivity, and physiological stress. In the current issue of Journal of Diabetes Science and Technology, Mitsios and coauthors describe the analytical accuracy of the new Accu-Check® Inform II blood glucose (BG) monitoring system commercialized by F. Hoffmann-La Roche Ltd. The point-of-care glucose meter achieved the desired degree of accuracy and precision, as defined by Clinical and Laboratory Standards Institute POCT12-A3 guidelines when evaluated using venous blood from 600 critically ill patients from multiple ICUs at two medical centers. Venous whole blood samples were used to obtain glucose meter results in duplicate. The remaining blood sample was centrifuged to obtain plasma for central hospital laboratory testing using the hexokinase method within 5 min of meter testing. A total of 98.8% of the 1200 Accu-Check Inform II meter's glucose values were within ± 12.5% (± 12 mg/dl) of the mean laboratory glucose value, and 99.8% were within ± 20% (± 20 mg/dl), thus meeting the Clinical and Laboratory Standards Institute criteria. Future studies are required to evaluate the clinical performance of the new BG monitoring system in the intended-use patient populations and critical care environments, using arterial, peripheral venous, central venous, and capillary blood samples.

Evaluation of the shock index in dogs presenting as emergencies

To (1) determine a reference interval for shock index (SI) [defined as heart rate (HR)/systolic blood pressure (SBP)], in a group of healthy dogs, and (2) compare SI in healthy dogs with dogs presenting to the emergency room (ER) deemed to be in or not in a state of shock. Prospective study. Sixty-eight clinically normal dogs, 18 dogs that were presented to the ER deemed to be in shock and 19 dogs presenting to the ER not deemed to be in shock. University teaching hospital. Peripheral or central venous blood sampling. Heart rate and SBP were recorded on simulated presentation (healthy dogs), and emergency presentations for both dogs deemed to be in shock and dogs not deemed in shock. Dogs in shock had a median SI of 1.37 (0.87-3.13), which was significantly higher than both other groups; dogs not deemed in shock had median SI 0.73 (0.56-1.20), P < 0.0001 and healthy dogs had median SI 0.78 (0.37-1.30) P < 0.0001), respectively. Receiver operator characteristic curve analysis suggested a SI cut-off of 1.0, yielding an area under the receiver operator characteristic (AUROC) of 0.89 (Specificity (Sp) 89, Sensitivity (Sn) 90) when comparing dogs deemed in shock with healthy dogs, and 0.92 (Sp 95, Sn 89) when comparing dogs in shock with to dogs not deemed in shock. The SI is an easy and noninvasive patient parameter that is higher in dogs that are deemed to be in shock than both healthy dogs and dogs presented as emergencies but not deemed to be in a state of shock. The measurement of SI may have some benefit in clinical assessment of emergency patients.

Evaluation of portable blood glucose meters for measurement of blood glucose concentration in ferrets (Mustela putorius furo)

To evaluate agreement of 3 models of portable blood glucose meters (PBGMs; 2 designed for use with human samples and 1 designed for veterinary use) with a laboratory analyzer for measurement of blood glucose concentrations in ferrets (Mustela putorius furo). Evaluation study. 52 ferrets. Samples were analyzed with 4 PBGMs (whole blood) and a laboratory analyzer (plasma). Two PBGMs of the model designed for veterinary use were tested; each was set to a code corresponding to canine or feline sample analysis throughout the study. Agreement and bias between measurements obtained with the PBGMs and the laboratory analyzer were assessed with Bland-Altman plots. Linear regression analysis was performed to evaluate associations with venipuncture site by comparison of central (jugular) and peripheral (lateral saphenous or cephalic) venous blood samples. Plasma glucose concentrations measured with the laboratory analyzer ranged from 41 to 160 mg/dL. Results from the PBGM for veterinary use coded to test a canine blood sample had the greatest agreement with the laboratory analyzer (mean bias, 1.9 mg/dL); all other PBGMs significantly underestimated blood glucose concentrations. A PBGM designed for use with human samples had the least agreement with the laboratory analyzer (mean bias, -34.0 mg/dL). Blood glucose concentration was not significantly different between central and peripheral venous blood samples for any analyzer used. Significant underestimation of blood glucose concentrations as detected for 3 of the 4 PBGMs used in the study could have a substantial impact on clinical decision making. Verification of blood glucose concentrations in ferrets with a laboratory analyzer is highly recommended.

Are Central Venous Lactate and Arterial Lactate Interchangeable? A Human Retrospective Study

In critically ill patients, arterial blood lactate concentration (Lact(a)) and Lact(a) clearance are used for the diagnosis of shock, for prognosis assessment, and to guide therapy. In recent years, central venous oxygen saturation (ScvO(2)), a surrogate for mixed venous blood saturation, either measured by fiberoptic catheters or from central venous blood samples, was used in shock to estimate the global balance between oxygen delivery and consumption. When central venous blood is drawn for ScvO(2) measurement, it also could be used to measure central venous lactate concentration (Lact(cv)). In this study, we evaluated the utility of Lact(cv) and Lact(cv) clearance as predictors of Lact(a) and Lact(a) clearance, respectively, in critically ill patients. This retrospective study was performed in an intensive care unit of a regional and teaching hospital. Using the electronic registry of our blood gas analyzer from March 2007 to December 2009, we identified patients with circulatory or respiratory failure who had pairs of Lact(cv) and Lact(a) obtained within a 30-minute interval. To assess the utility of Lact(cv) as a predictor of Lact(a) above 2 and 4 mmol/L, we calculated the area under receiver operating characteristic curves (AUCs) for these thresholds. We also calculated AUC of Lact(cv) clearance to detect a Lact(a) clearance <10% or >10%. Six hundred seventy-three Lact(cv)/Lact(a) pairs in 188 patients were analyzed. AUC of Lact(cv) to predict a Lact(a) above 2 and 4 mmol/L was 0.98 (95% confidence interval: 0.97-0.99) and 0.98 (95% confidence interval: 0.96-0.99), respectively. Lact(cv) with the cutoff value of 2 mmol/L can predict a Lact(a) above 2 mmol/L with sensitivity >92% and specificity >90%. AUC for Lact(cv) clearance to detect a Lact(a) clearance <10% or >10% was 0.93 or 0.94, respectively. Lact(cv) and Lact(a) collected within a 30-minute range are interchangeable for clinical practice.

Lung anabolic activity in patients with chronic heart failure: Potential implications for clinical practice

ObjectiveThe proteins in the lungs are in constant flux, undergoing degradation and resynthesis. We investigated pulmonary protein and amino acid metabolism, the biochemical basis of the remodeling process, in individuals with chronic heart failure receiving or not receiving β-blocker therapy with bisoprolol (BIS). MethodsClinically stable rehabilitative patients with chronic heart failure, without metabolic diseases or liver/renal failure, and with a stable weight over the preceding 3 mo underwent right heart catheterization, and radial artery cannulation. Mixed central venous and arterial blood samples were drawn simultaneously to calculate the venous-arterial difference of amino acids (pulmonary uptake and release). ResultsTwenty-two patients on BIS therapy and eight not receiving BIS were analyzed. The two groups showed a net pulmonary protein synthesis (i.e., a positive value of phenylalanine [venous-arterial difference] × cardiac index product) and amino acid extraction, the rates of which were significantly lower in patients on BIS therapy. The two groups had pulmonary hypertension (mean pulmonary artery pressure >19 mmHg). Pulmonary vascular resistance was 57% higher in patients not receiving BIS than in those on BIS therapy (6.65 ± 2.90 versus 4.23 ± 1.49 mmHg/L · min−1 · m−2, P < 0.05). Pulmonary vascular resistance correlated positively with the pulmonary extraction of total essential amino acids (r = +0.4576, P = 0.01) and leucine (r = +0.5083, P = 0.004), the most important amino acid for protein synthesis. ConclusionPatients with chronic heart failure have increased rates of amino acid extraction and pulmonary protein synthesis, suggesting, at least in part, an increased rate of lung remodeling. Therapy with BIS attenuates lung metabolic abnormalities.

Central venous catheter sampling of low molecular heparin levels

The low molecular weight heparin effect in children is monitored using the anti-factor Xa level. Venipuncture is recommended; however, central venous catheter blood sampling is often necessary. Heparin infused through central venous catheters may contaminate central venous catheter blood samples, preventing reliable anti-factor Xa level measurement. Simultaneous anti-factor Xa/partial thromboplastin time measurement with central venous catheter blood sampling may predict anti-factor Xa reliability. To determine the prevalence of heparin contamination as measured by the partial thromboplastin time/anti-factor Xa in central venous catheter blood samples and whether careful sampling could minimize heparin contamination of anti-factor Xa levels from central venous catheter blood sampling. Simultaneous partial thromboplastin time/anti-factor Xa measurements from central venous catheter blood sampling determined the prevalence of heparin contamination of central venous catheter blood samples. In phase II, children receiving low molecular weight heparin had routine central venous catheter blood sampling to measure the peak anti-factor Xa and the simultaneous partial thromboplastin time. Anti-factor Xa levels with a partial thromboplastin time of >40 secs (pair 1) were identified; there was no low molecular weight heparin dose change, and the paired sample was repeated using a careful sampling technique (pair 2). Pairs 1 and 2 were compared to determine the efficiency of the sampling technique in removing heparin from the central venous catheter blood samples. In phase I, 100 children had 485 paired anti-factor Xa/partial thromboplastin time central venous catheter blood samples with 29% ± 4.1% (95% confidence interval 25% to 33%) anti-factor Xa with partial thromboplastin times of >40 secs. In phase II, 43 children had 129 paired anti-factor Xa/partial thromboplastin time samples with partial thromboplastin times of >40 secs. The pair 1 mean partial thromboplastin times/anti-factor Xa levels were 109.8 secs (SD 53.1, range 34.0 to >200 secs) and 1.03 units/mL (SD 0.56, range 0.26-4.2 units/mL). Repeated partial thromboplastin times/anti-factor Xa levels (pair 2) were significantly decreased from those of pair 1 (p < .001) with means of 58.5 secs (SD 21.2, range 22-152 secs) vs. 109.8 secs (SD 53.1, range 34.0 to > 200 secs, p < .001) and 0.63 unit/mL (SD 0.30, range 0.02-1.77 units/mL) vs. 1.03 units/mL (SD 0.56, range 0.26-4.2 units/mL), respectively. Measurement of the partial thromboplastin time performed in combination with that of the anti-factor Xa level can be used to assist health practitioners to identify unfractionated heparin contamination of anti-factor Xa levels drawn from central venous catheters. A careful sampling technique may minimize heparin contamination in central venous catheter blood samples.

Decrease of total antioxidative capacity in developed low cardiac output syndrome.

Background. It has been known that cardiac surgery induces an oxidative stress. The persistent oxidative stress during reperfusion may lead to depressed myocardial function resulting in low cardiac output syndrome (LCOS) necessitating inotropic or intra-aortic balloon counterpulsation support. Total antioxidant capacity (TAC) is a measurement of oxidative stress in tissues. The purpose of this study was to examine the TAC differences during coronary artery bypass graft (CABG) operation in patients who have developed LCOS and who have not. Material and Methods. Seventy-nine patients were enrolled in the study. Central venous blood samples were obtained immediately before surgery, during operation, and at the end of surgery to assess TAC. Clinical data regarding patient demographics and operative outcomes were prospectively collected and entered into our clinical database. Results. LCOS developed in 8 patients (10.12%). The TAC has decreased sharply in the LCOS patients compared with those who did not develop LCOS (P < 0.001) during operation. In addition, the receiver operating characteristic (ROC) area was 0.879. Conclusion. TAC has decreased during operation in a significant proportion of patients undergoing isolated CABG, and this is more prominent and serious and might be an independent variable in patients who have developed LCOS. This may be related to intraoperative misadventure or inadequate myocardial antioxidative protection. Routine measurement of the TAC during operation may provide information for assessment of the LCOS development.

Comparison of myocardialprotective effects of isoflurane versus sevoflurane in patients undergoing off pumpcoronary artery bypass grafting

：Objective To compare themyocardial protective effects of isoflurane versus sevoflurane in patients undergoingoff-pump coronary artery bypass grafting (OPCABG). Methods Forty ASA Ⅱ or Ⅲ patients (NYHA Ⅱ or Ⅲ ) of both sexes, aged 40-55yr, weighing 55-94 kg, scheduled for elective OPCABG, were randomly divided into 2 groups( n = 20 each): isoflurane group ( group Ⅰ) and sevoflurane group (group S). Anesthesia was induced with midazolam, sufentanil and vecuronium. Patients weretracheal intubated and mechanically ventilated. Anesthesia was maintained with inhalationof isoflurane or sevoflurane and infusion of sufentanil and vecuronium. In group Ⅰ,the initial end-tidal concentration of isoflurane was 1.2%. In group S, the initialend-tidal concentration of sevoflurane was 1.7 %. BIS value was maintained at 40-50 byadjusting the end-tidal concentration of isoflurane or sevoflurane. The central venousblood samples were collected immediately before skin incision, at the end of surgery, 2and 24 h after surgery for determination of plasma creatine kinase-MB (CK-MB) activity andcardiac troponin Ⅰ (cTnI) concentration. Theadverse cardiovascular events were recorded. Results The incidences of ventricularpremature beat, tachycardia, bradycardia, ventricular fibrillation and S-T segmentelevation ( ＞0.1 mV) during surgery and the plasma CK-MB activity and cTnIconcentration after surgery were significantly higher in group S than in group Ⅰ ( P ＜ 0.05). Conclusion Isoflurane has better myocardialprotective effect than sevoflurane in patients undergoing OPCABG. Key words: Isoflurane; Anesthetics, inhalation; Coronary arterybypass, off-pump

Abstract P3-02-10: Comparison of Circulating Tumour Cells in Peripheral and Central Venous Blood of Patients with Metastatic Breast Cancer: A Pilot Study

Abstract Background: Enumeration of circulating tumour cells (CTC), as performed by the CellSearch System (Veridex, Raritan, NJ, USA), has prognostic significance in patients with metastatic breast cancer (MBC). Questions remain on how these cells - if all - are capable to survive in the circulation and ultimately give rise to distant metastases. Experiments in mouse models have shown that CTC only appear transiently in the circulation after injection in the tail vein or left ventricle. Data on the discrete localisation of CTC in the blood stream and CTC kinetics in human breast cancer is still limited. The aim of this pilot study was to directly compare the amount of CTC measured in peripheral and central venous blood samples of patients with MBC in order to reveal possible differences. Methods: So far, we have included 18 patients with MBC presenting at our hospital with either primary metastatic (N=2) or progressive disease (N=16). Most patients suffered from diffuse metastatic involvement and were extensively pretreated. Clinically evident lung metastases were documented in 4/18 patients. Peripheral venous blood (PVB) - obtained from an antecubital vein - and central venous blood (CVB) samples - obtained from the subcutaneous port catheter - were drawn into CellSave Preservative tubes (Immunicon, Huntingdon Valley, PA) and processed in parallel using the CellSearch Circulating Tumor Cell Test (Veridex, Raritan, NJ, USA). With this test, CTC captured from 7.5 mL whole blood, are defined as EpCAM+, nuclear cells (DAPI+), expressing cytokeratins 8/18/19 and lacking CD45 expression. Results: CTC were detected in both PVB and CVB samples of 16/18 patients. In 2 patients no CTC were detected, neither in PVB nor in CVB. In 16 patients with detectable CTC, the number of CTC was found to be significantly higher in CVB (median: 65; range: 3-4036) than in PVB (median: 45; range: 1-4013) samples (Wilcoxon Signed Ranks Test, P=0.001). When analyzing samples parewise, the number of CTC in CVB was higher than the number of CTC in PVB in 15/16 patients, although marginally in 4 of 15 patients (median ratio CVB/PVB: 1.8; range: 1.0-3.1). Only 1 patient showed a higher number of CTC in PVB (absolute value: 49 CTC/7.5 mL blood) as compared to CVB (absolute value: 41 CTC/7.5 mL blood). Conclusions: In this study, a substantial decrease in the number of CTC was observed between CVB and PVB of patients with MBC. This difference might be relevant in the clinical setting as a quantitative cut off in the number of CTC is used to distinguish between patients with good and worse prognosis. As hand metastases are most uncommon, the lungs are suggested to function as the main sieve, even in the absence of clinically overt lung metastases. However, further research in larger patient populations and - where feasible - including radial arterial blood sampling, is required in order to confirm these results and to investigate human CTC kinetics in depth. Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P3-02-10.

Paco2 becomes greater than Pvco2 during apnoea testing for brain death diagnosis

The apnoea test is performed to complete the diagnosis of brain death. The most efficient respiratory stimulus is the arterial carbon dioxide partial pressure (Paco2), hence it is used in this test [1, 2]. The patient is disconnected from the ventilator while receiving 100% oxygen via a catheter inserted into the endotracheal tube placed to the level of the carina. The goal of apnoeic oxygenation is to document the absence of breathing once Paco2 arises sufficiently to stimulate the respiratory centre. However, there is no agreement as to what should be the final Paco2 for maximal stimulation. In addition, complications may occur during the performance of the test [3]. As a result of the chance observation of the inversion of Pvco2–Paco2 gradient in a patient with brain death during the apnoea test, we performed simultaneous arterial and central venous gases during the apnoea test in 20 consecutive patients being tested for brain death. We obtained Local Research Ethics approval and relatives’ assent for this. The patients were on two different intensive care units of two university hospitals in Barcelona, between October 2005 and May 2007. They were disconnected from mechanical ventilation while receiving 100% oxygen via a catheter inserted into the tracheal tube to the level of the carina. Simultaneous arterial and central venous blood samples for Paco2 and Pvco2 measurements were obtained before and after the apnoea test. Before the test, mean (SD) Pvco2 (4.67 (0.28)) was greater than Paco2 (4.0 (0.25)) but after the onset of apnoea, this relationship was reversed with Paco2 (7.86 (0.24)) becoming greater than Pvco2 (6.66 (0.24)). This reversal of the venous-arterial CO2 gradient was observed in all the patients and in both hospitals. This finding has been previously reported in arterial and mixed venous samples by Rigg and Cruickshank [4], who investigated CO2 kinetics in two patients undergoing apnoea testing for brain death. They postulated that the reversal of the normal Paco2 and co2 (mixed venous) relationship during apnoea to be a consequence of the Haldane effect: the CO2 dissociation curves are different in reduced and oxygenated haemoglobin. As apnoea testing was performed without oxygenation, it was concluded that reduced haemoglobin was able to carry more CO2 than carbamino compounds explaining how the rise in Paco2 was greater than that in mixed venous co2. However, our patients underwent apnoeic oxygenation and we also observed that the Paco2 became greater than Pvco2, so that reversal of the arterial and venous Pco2 relationship is independent of the absence of oxygen. In two of our patients, blood gas analyses were performed before final disconnection from the ventilator once brain death was diagnosed, and in both cases Paco2 was greater than Pvco2. Fig. 5 shows the changes in one of these patients, with a normal gradient of beginning of the test and inversion from the second minute. Unlike Rigg and Cruikshank [4] we could not take mixed venous samples and our venous samples were from the central venous catheter. The repeated observation of this phenomenon in 20 patients of two hospitals over 18 months suggests that it was not a laboratory mistake. Alterations in Pvco2 (squares; grey line) and Paco2 (circles; black line) over time in a single patient. NB PCO2 given in mmHg. One possible explanation is that the lung parenchyma continues producing CO2 and consuming O2 via the bronchial arteries that empty the bronchial veins into the left auricle. As the patient is apnoeic and not eliminating CO2, an inverse CO2 gradient occurs. Fig. 5 suggests a change in the way in which CO2 is transported, as the Paco2 at 1 min is lower than the Pvco2 at 2 min. There may be an alteration in CO2 transportation from its dissolved form (corresponding to 7% of the total CO2 transported), to transportation linked to the bicarbonate ion or carbamino compounds. Finally, the goal of the apnoea test is to achieve a sufficiently high Paco2 to stimulate respiratory centres in the medulla oblongata. However, in view of a reversed Pvco2 and Paco2 gradient we may have to consider modifying our practice, assessing Pvco2 rather than Paco2 [5].