The Use of Point-of-Care Blood Gases for Critically Injured Patients at a Level 1 Trauma Center.

Dear Editor,

Current trauma guidelines recommend arterial blood gases (ABGs) as a part of routine shock assessment.[1] In other clinical contexts, venous blood gases (VBGs) are frequently relied on to guide clinician decision-making.[234] In injured patients, serial measurement of the ABG base deficit and lactate is recognized as a useful indicator of hemorrhagic shock and serial marker of response to therapy.[25]

Despite an increased uptake of VBG use, reliance on venous sampling has been questioned due to limitations in the levels of agreement with ABGs.[4] However, many venous parameters are well correlated with the notable advantages of “ease of VBG sampling” and “reduced complications.”[46] As a result, we require further knowledge of how ABGs and VBGs are used by our trauma teams in a clinical context.[67] A recent relevant study examined the utility of venous sampling in trauma patients, concluding: “(sic) while correlations between ABG and VBG and trauma are strong, the agreement is not acceptable to universally recommend VBG among all trauma patients.”[7]

Following ethical approval by the local ethics committee, we completed a small observational study of blood gas use at our Level 1 trauma center. We included admitted trauma patients over 16 years presenting with an Injury Severity Score (ISS) ≥12. Patient exclusions included: deceased in emergency department (ED), discharged from ED, admission to the short stay unit, and electronic medical record (EMR) not available. A cohort of 9 months of consecutive patients was derived by the trauma data manager, and the EMR was reviewed for ABG and VBG use within 4 h of arrival.

During the study window, 455 trauma cases had ISS ≥12. All included patients had complete data available. The overall inpatient mortality was 8.6%. The mean age of nonsurvivors was 70.84 years (standard deviation [SD] 20.4) and survivors was 51.45 years (SD 22.1) (P < 0.001). A total of 377 (74.1%) were male and the median ISS was 17. The results for blood gas sampling are summarized in Table 1, with VBG-only sampling occurred in 243 (53.4%).

Table 1

Utilization of point-of-care blood gases within 4 h of emergency department arrival in trauma patients (Injury Severity Score ≥12)

Recorded blood gas sampling <4 h of ED presentation	n (%)	30-day mortality, n (%)	Intensive care LOS, days (SD)
No ABG or VBG performed	83 (18.2)	2 (2.4)	2.1 (1.8)
VBG only performed	243 (53.4)	23 (9.5)	2.9 (2.4)
ABG only performed	63 (13.8)	9 (14.2)	3.1 (2.9)
ABG and VBG performed	12 (2.6)	1 (8.3)	2.7 (2.1)
ABG and VBG performed*	54 (11.9)*	4 (7.4)	3.0 (2.4)

*Patients enrolled into concurrent ABG versus VBG correlation study. LOS: Intensive care unit length of stay, ABG: Arterial blood gas, VBG: Venous blood gas, ED: Emergency department, SD: Standard deviation

Despite a preference in the literature for ABGs, the majority of trauma patients with ISS >12 in this small study received VBG sampling in the first 4 h following admission (53.4%).[36] This observation may suggest that VBGs have been adopted as an initial screening tool. This practice is likely to be viewed by some readers as a significant extrapolation of the existing evidence for using VBG sampling.[56]

As outlined in the opening paragraph, lactate and base deficit are commonly used to diagnose the presence of absence of significant shock.[4] Lactate is favored in many nontrauma contexts, but base excess has historically been used by most trauma clinicians.[78] We note that while base deficit has been shown to inadequately correlated between ABG and VBG samples in trauma, lactate has been widely demonstrated to have a reliable equivalence and be a consistent marker of shock.[689] Therein, it may be a reasonable to be cautiously reassured if the VBG is normal (for both lactate and base excess), but that an ABG should be taken for any clinical concern or changes.[49]

In conclusion, most injured patients in this study received at least one blood gas within 4 h. VBG-only sampling was a commonly observed practice despite guidelines recommending the routine use of ABGs. Within the limitations of this small observational study, it appears that the practice of using VBGs in trauma has been partially adopted. Therefore, given the controversy of VBG use in trauma, further correlation studies and direct derivation of VBG parameters are now required to ensure the appropriateness of this practice.

Yours Sincerely,

Financial support and sponsorship

Nil.

Conflicts of interest

The study was funded by trauma and emergency department resources only.