POC Analysis of IO Blood Samples Within Critically Ill Patients

Intravenous access is sometimes difficult to achieve due to vasoconstriction or centralization of circulation. Feasible IO-access with power-driven device is a standard alternative method of vascular access for critically ill patients. It is still unclear whether results of IO samples agree with venous or arterial blood samples so that they could be used in clinical decision-making.

After intraosseous access has been established for fluid resuscitation or medication, a common practice is to aspirate a small amount of blood to verify the proper location of the IO-needle.

POC-testing can provide emergency physicians or paramedics with important information about the patients. Could bone marrow samples be used for POC-testing instead of arterial or venous blood for emergency treatment decision-making or patient allocation?

Several animal and human studies have been published to investigate the correlation between IO versus venous or arterial blood values. Investigators of this study have performed a study in healthy volunteers and discovered that there is a good agreement for some laboratory parameters (pH, gluc, lact), but for K the agreement is poor. Our study group has as well performed a study in critically ill animals investigating the agreement during cardiac arrest and resuscitation. Te evidence about critically ill people is still week.

Aim of this study is to analyze the reliability of analysis of IO samples compared to arterial blood samples within critically ill adult emergency patients.

The hypotheses of this study are:

• Principally, it is possible to analyze IO blood samples with a POC device.
• The results are reliable enough to guide emergency treatment.

If both hypotheses prove to be true, the method can be immediately used in emergency medical situations, e.g. in searching for reversible causes of cardiac arrest.

Setting

Prospective, observational study with 35 prehospital emergency patients. The IO-samples are collected from the small amount of blood, which is aspirated from intraosseous space to confirm the correct needle placement. The IO needles are inserted to the patients for emergency treatment, not because of the study. Critically ill patients, to whom emergency doctors are inserting an intraosseous needle for emergency fluid or drug treatment, are included in the study.

Samples will be analyzed by using an i-STAT point of care analyzer (i-STAT® handheld, Abbot Point of Care Inc. U.S.A) using CG8+ cartridges to analyse Hb, Na, K, pH, pCO2, pO2, TCO2, HCO3, BE, and SpO2. The reliability of the results comparing the IO and arterial samples will be tested with Bland-Altman method by calculating the bias with 95% confidence intervals.

Ethical issues

The ethical committee of Medical Faculty of University of Helsinki has approved the research. Informed consent is waived.

Time plan

The samples will be collected during years 2017 - 2019. The analysis will be performed in the end of the year 2019.

Inclusion criteria

• need for point-of-care analysis
• need for intraosseous access

Exclusion criteria

• cardiac arrest
• ability to understand the consent issues in Finnish, Swedish or English