Performance of 3 mL versus 5 mL Discarded Volume for Blood Sampling from Central Venous Access Device

Comparison of laboratory results between central venous access devices and venipuncture: A systematic review and meta-analysis

OBJECTIVES

To compare the hematologic, blood chemistry, and coagulation test results between two blood sampling methods via central venous access devices (CVADs) and venipuncture.

METHOD

The authors searched PubMed, Embase, Cochrane, Web of Science, and the Cumulative Index to Nursing and Allied Health Literature (CINAHL) for controlled studies that compared the differences in hematologic, blood chemistry, and coagulation test results between venipuncture and CVADs from the date of database establishment to July 2022. Two researchers independently performed the literature screening, data extraction, and quality assessment. The standardized mean difference was used as the effect size for continuous variables and a 95% confidence interval was provided. The random-effects model was used for an I2 > 50%, otherwise the fixed-effects model was used. Sources of heterogeneity were determined by subgroup analysis or sensitivity analysis, as indicated.

RESULTS

This review ultimately identified 17 studies for systematic review, of which 12 were selected for meta-analysis. A total of 541 adult participants were included in the meta-analysis. With the exception of the activated partial thromboplastin time, there were no significant differences in hematologic, blood chemistry, and coagulation test results between blood sampling via venipuncture and CVADs.

CONCLUSIONS

The results of this study provide substantial evidence that blood sampling via venipuncture and CVADs had equal reliability in most laboratory tests. Serial blood sampling via CVADs will reduce the risk of bleeding episodes and pain at the blood collection site, and safety for healthcare professionals.

Optimal volume for the draw-and-return methods to enhance activated partial thromboplastin time ratio accuracy in hemodialysis patients with central venous catheters

Background

Significant errors of activated partial thromboplastin time (aPTT) ratio were frequently observed in blood sampling from central venous dialysis catheter (CVC) of hemodialysis (HD) patients. Following the draw-and-return methods, initial blood withdrawal from the catheter before sampling can reduce the error, but the optimal withdrawal volume remains undetermined.

Aim

The objective of this study is to determine the optimal blood withdrawal volume for the draw-and-return methods to improve aPTT ratio accuracy in hemodialysis patients with CVC.

Methods

A prospective study was conducted in patients receiving HD via CVC. Four blood samples were collected from each patient, involving a peripheral venipuncture and three draw-and-return samples (10 ml, 20 ml and 25 ml groups). The aPTT ratio of a peripheral sample was used as a reference to determine the aPTT ratio accuracy for each draw-and-return group. Subsequently, the agreement was illustrated using modified Bland-Altman plot.

Results

A total of 1,000 samples were obtained from 250 patients. The patients had a mean age of 59.6 ± 15.4 years, with 17.2% using citrate as the CVC's locking agent. The adjusted accuracies of the aPTT ratio varied significantly among the three withdrawal volumes (p-value <0.001). The 25 ml group demonstrated the highest accuracy (43.2%; 95%CI, 38.0-48.4), followed by the 20 ml group (30.0%; 95%CI, 24.9-35.2), and the 10 ml group (18.0%; 95%CI, 12.8-23.2). Additionally, using citrate as a locking agent provided more than 80.0% aPTT ratio accuracy, whereas heparin demonstrated inferior accuracy even in the 25 ml withdrawal group.

Conclusion

The optimal blood withdraw volume for the draw-and-return methods concluded at 20 ml for citrate locked-CVC and 25 ml for heparin which significantly improved aPTT ratio accuracies. Applying citrate as a locking agent provides clear benefits for aPTT ratio monitoring, while peripheral venipuncture is recommended in cases of heparin-locked CVC.

Is minimising waste volume for drawing blood samples in critically ill patients feasible?

INTRODUCTION

Drawing blood samples through a central venous catheter (CVC) is a customary practice in Intensive Care Units (ICUs). It is indicated to discard a volume of waste blood to avoid interference in the results.

AIM

To determine whether a lower discard volume for obtaining blood samples from temporary CVCs placed into the internal jugular, femoral or subclavian vein offers valid results.

METHOD

A quasi-experimental prospective cross-sectional study for which sixty-five patients of over 18 years of age in ICUs, who had been fitted with a triple lumen central venous catheter, were recruited over a period of eight months. Two consecutive blood samples were extracted with tubes for biochemistry, coagulation and hemogram from each patient from the distal lumen. The first sample was obtained with a discarded waste of 1.5 ml from a total extracted volume of 10.2 ml, similar to the usual waste in our ambit (10 ml). Subsequently the second sample was obtained. The paired t-test was used to analyse the data. The Bland-Altman plot and intraclass correlation coefficient (ICC) were used to measure the agreement between methods. The reference change value (RCV) was established as the admissible limit of variation between the pairs of samples.

RESULTS

A total of 65 sample pairs were drawn (intervention-control). The paired t-test found statistically significant differences with a significance level of α = .05 for chlorine (-.536; .012); prothrombin time (-.092; .019) and prothrombin activity (.284; 1.375).The ICC was greater than .9 in all the variables and the limit determined for the RCV was not surpassed by any value.

CONCLUSIONS

The results show the reliability of the blood samples drawn with a discard volume of 1.5 ml.