Is Venous to Arterial Conversion (v-TAC) of Blood Gas Reliable in Critical Ill Patients in the ICU?

• Conditions: Alkalosis; Sepsis; Respiratory Insufficiency; Acidosis; Abdomen, Acute; Metabolic Disease
• Interventions: Diagnostic Test: venous to arterial conversion (v-TAC)

• Registration Number: NCT03309423
• Lead Sponsor: Aalborg University

Brief Summary

Objective: Arterial blood gas (ABG) is essential in the clinical assessment of potential acutely ill patients venous to arterial conversion (v-TAC), a mathematical method, has recently been developed to convert peripheral venous blood gas (VBG) values to arterialized VBG (aVBG) values. The aim of this study is to test the reliability of aVBG compared to ABG in an intensive care unit (ICU) setting.

Method: Consecutive patients admitted to the ICU with pH values \<7,35 or \>7,45 are included in this study. Paired ABG and aVBG samples are drawn from patients via arterial catheter, central venous catheter and/or peripheral venous catheter and compared.

Detailed Description

Arterial blood gas (ABG) analysis is essential in assessment of respiratory and metabolic status in acutely ill patients. In comparison to peripheral venous blood (PVG) sampling, the ABG sampling procedure is more painful for the patient and technically more challenging for the clinician to perform. Other drawbacks of ABG sampling include adverse events such as subcutaneous hematoma, arterial thrombosis or embolization, and pseudoaneurysms.

Peripheral venous blood gas (VBG) sampling has been suggested as an alternative to the ABG procedure. This procedure causes less patient discomfort and the sample can be analysed in combination with other venous blood tests. Studies have revealed that pH and bicarbonate have good correlation, whereas venous and arterial blood gasses (pO2 and pCO2) show low agreement.

However, a new method has been developed to calculate ABG values mathematically from peripheral venous blood by use of venous to arterial conversion (v-TAC) software (Obimedical, Denmark), supplemented with oxygen saturation measured by pulse oximetry. The principle of the method is a mathematical transformation of VBG values to arterialized values (aVBG) by simulating the transport of blood back through the tissue. Initial testing of the method in an emergency department setting showed acceptable clinical congruence between arterial and mathematically arterialized pH and pCO2 with a small difference (+/- SD) on 0.001 +/- 0.024 and 0.00 0.46 kPa, respectively. However, inaccurate values of pO2 were seen when oxygen saturation measured by pulse oximetry was above 96%, due to the flat shape of the oxygen dissociation curve (ODC).

Although most patients in the ICU have arterial catheters therefrom ABG can be drawn, applying arterial catheter is difficult or even impossible in some patients. In relation to step-down some patients get arterial catheters removed and in the event of deterioration in patients acid-base or respiratory disease aVBG could prove useful as a minimally invasive tool to assess patients status.

The aim of this study is to investigate if v-TAC is reliable and safe to use in patients with critically respiratory or metabolic disease admitted to the ICU.

Study Timeline

• Status Verified: 2017-10
• Study First Submitted: 2017-10-04
• Study Start: 2017-10-09
• Study First Submitted QC: 2017-10-12
• Last Update Submitted: 2017-10-12
• Study First Posted: 2017-10-13
• Last Update Posted: 2017-10-13
• Primary Completion: 2018-01-30
• Study Completion: 2018-03-30

Recruitment & Eligibility

• Status: UNKNOWN
• Sex: All
• Target Recruitment: 50

Inclusion Criteria

• All patients admitted to the intensive care with the following:
• Arterial catheter for other purpose.
• Peripheral venous catheter or central venous catheter for other purpose.

Exclusion Criteria

• Normal pH in arterial blood gas.

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Respiratory disease	venous to arterial conversion (v-TAC)	Patients with acute respiratory insufficiency admitted to the ICU and with pH \<7,35 or \>7,45
Metabolic disease	venous to arterial conversion (v-TAC)	Patients with acute metabolic disease admitted to the ICU and with pH \<7,35 or \>7,45
Sepsis	venous to arterial conversion (v-TAC)	Patients with acute sepsis admitted to the ICU and with pH \<7,35 or \>7,45

Primary Outcome Measures

Name	Time	Method
Lin's Concordance correlation coefficient (CCC)	1. january 2018	Comparison of pO2 (Unit of Measurement: kilopascal) between ABG and aVBG (from central venous catheter). The closer CCC is to 1 the better correlation.
Bland and Altman's plot	1. january 2018	Mean difference and 95% limits-of-agreement of pO2 (Unit of Measurement: kilopascal) between ABG and aVBG (from central venous catheter).

Secondary Outcome Measures

Name	Time	Method
Number of patients with sepsis group.	1. january 2018	Number and percentage of patients in 'sepsis' group.
Number of patient with metabolic disease	1. january 2018	Number and percentage of patients in 'metabolic disease' group.
Number of patient with acute respiratory insufficiency	1. january 2018	Number and percentage of patients in 'respiratory disease group' group.
Mean number of days until pH neutrality in sepsis group	1. january 2018	Mean number of days until patients ABG pH was within the range 7.35-7.45 in 'sepsis' group.
Mean number of days until pH neutrality in patients with metabolic disease.	1. january 2018	Mean number of days until patients ABG pH was within the range 7.35-7.45 in 'metabolic disease' group.
Mean number of days until pH neutrality in patients with respiratory disease.	1. january 2018	Mean number of days until patients ABG pH was within the range 7.35-7.45 in 'respiratory disease' group.

Trial Locations

Locations (1)

Faculty of Medicine, Doctoral School, Ph.d. study; 🇩🇰 Aalborg, North Denmark, Denmark