Intraosseous blood gases during hypothermia: correlation with arterial, mixed venous, and sagittal sinus blood

Analysing blood from intraosseous access: a systematic review

Intraosseous (IO) access is used widely as an optional vascular route for critically ill patients. It is still unclear whether the IO access can be used as a source for emergency blood samples. The aim of this study was to systematically review the existing literature on the usability of IO blood samples for analysing the parameters relevant to emergency care. We performed a data search from the Medline and Embase databases, the Cochrane Library and the Clinical trials registry. Animal studies and studies with healthy and ill adults and children were included in the search. The data were collected and reported following the PRISMA guidelines. The PROSPERO database registration number of this review is CRD42017064194. We found 27 studies comparing the blood samples from the IO space with arterial or venous samples, but only three of them followed the recommended guidelines for method comparison studies. The study populations were heterogeneous, and the sample sizes were relatively small (14, 17 and 20 individuals) in the three studies. The results of specific laboratory parameters were scarce and discordant. The evidence on the agreement between IO and arterial and venous samples is still weak. Existing studies with healthy volunteers and animal models provide important insight into the analyses of IO samples, but more evidence, especially from haemodynamically unstable patients, is needed for wider implementation of IO blood sampling in critically ill patients.

Intraosseous blood samples for point-of-care analysis: agreement between intraosseous and arterial analyses

Background

Point-of-care (POC) testing is highly useful when treating critically ill patients. In case of difficult vascular access, the intraosseous (IO) route is commonly used, and blood is aspirated to confirm the correct position of the IO-needle. Thus, IO blood samples could be easily accessed for POC analyses in emergency situations. The aim of this study was to determine whether IO values agree sufficiently with arterial values to be used for clinical decision making.

Methods

Two samples of IO blood were drawn from 31 healthy volunteers and compared with arterial samples. The samples were analysed for sodium, potassium, ionized calcium, glucose, haemoglobin, haematocrit, pH, blood gases, base excess, bicarbonate, and lactate using the i-STAT® POC device. Agreement and reliability were estimated by using the Bland-Altman method and intraclass correlation coefficient calculations.

Results

Good agreement was evident between the IO and arterial samples for pH, glucose, and lactate. Potassium levels were clearly higher in the IO samples than those from arterial blood. Base excess and bicarbonate were slightly higher, and sodium and ionised calcium values were slightly lower, in the IO samples compared with the arterial values. The blood gases in the IO samples were between arterial and venous values. Haemoglobin and haematocrit showed remarkable variation in agreement.

Discussion

POC diagnostics of IO blood can be a useful tool to guide treatment in critical emergency care. Seeking out the reversible causes of cardiac arrest or assessing the severity of shock are examples of situations in which obtaining vascular access and blood samples can be difficult, though information about the electrolytes, acid-base balance, and lactate could guide clinical decision making.

The analysis of IO samples should though be limited to situations in which no other option is available, and the results should be interpreted with caution, because there is not yet enough scientific evidence regarding the agreement of IO and arterial results among unstable patients.

Conclusions

IO blood samples are suitable for analysis with the i-STAT® point-of-care device in emergency care. The aspirate used to confirm the correct placement of the IO needle can also be used for analysis. The results must be interpreted within a clinical context while taking the magnitude and direction of bias into account.

Evaluation of intraosseous pressure in a hypovolemic animal model

BACKGROUND

In emergent situations, access to the vascular bed is frequently required for fluid and medication administration. Central venous catheter placement is associated with risk and may slow resuscitation in the unstable patient. The purpose of this study was to determine whether intraosseous pressure (IOP) could be consistently recorded and how similar this pressure was to central venous and arterial pressure in a porcine hemorrhagic shock model.

MATERIALS AND METHODS

After sedation, eight female swine had catheters placed in the femoral vein, aorta via femoral artery, and superior vena cava. IOP lines were placed in the proximal humerus, distal femur, and proximal tibia. Pressure readings were recorded continuously through the five stages of progressive hypovolemia. Pressure data were descriptively summarized, with the percent of change of IOP at each stage compared with arterial pressure using a multilevel mixed effects linear model with log transformation.

RESULTS

The IOP baseline values were between 16 and 18 mm Hg, approximately 22% of baseline arterial pressure. The intraosseous (IO) waveform mostly closely resembled the arterial pressure waveform, including the presence of a dichroitic notch. Pressure variations caused by ventilation (respiratory variability) were also identified in all the tracings. The rate of pressure change in the humeral IO most closely matched the change in arterial pressure rate. IO blood gas analysis showed gas composition to most closely match venous blood.

CONCLUSIONS

IOP was reliably obtained in this porcine model and suggests potential for clinical application in humans.