• Erik Näslund, Lars-Göran Lindberg, Gunnar Strandberg, Catharina Apelthun, Stephanie Franzén, and Robert Frithiof.
• Department of Surgical Sciences, Section of Anaesthesia and Intensive Care, Uppsala University, Uppsala, Sweden. erik.naslund@surgsci.uu.se.
• J Clin Monit Comput. 2023 Jun 1; 37 (3): 847856847-856.

PurposeThis study intended to determine, and non-invasively evaluate, sternal intraosseous oxygen saturation (SsO2) and study its variation during provoked hypoxia or hypovolaemia. Furthermore, the relation between SsO2 and arterial (SaO2) or mixed venous oxygen saturation (SvO2) was investigated.MethodsSixteen anaesthetised male pigs underwent exsanguination to a mean arterial pressure of 50 mmHg. After resuscitation and stabilisation, hypoxia was induced with hypoxic gas mixtures (air/N2). Repeated blood samples from sternal intraosseous cannulation were compared to arterial and pulmonary artery blood samples. Reflection spectrophotometry measurements by a non-invasive sternal probe were performed continuously.ResultsAt baseline SaO2 was 97.0% (IQR 0.2), SsO2 73.2% (IQR 19.6) and SvO2 52.3% (IQR 12.4). During hypovolaemia, SsO2 and SvO2 decreased to 58.9% (IQR 16.9) and 38.1% (IQR 12.5), respectively, p < 0.05 for both, whereas SaO2 remained unaltered (p = 0.44). During hypoxia all saturations decreased; SaO2 71.5% (IQR 5.2), SsO2 39.0% (IQR 6.9) and SvO2 22.6% (IQR 11.4) (p < 0.01), respectively. For hypovolaemia, the sternal probe red/infrared absorption ratio (SQV) increased significantly from baseline (indicating a reduction in oxygen saturation) + 5.1% (IQR 7.4), p < 0.001 and for hypoxia + 19.9% (IQR 14.8), p = 0.001, respectively.ConclusionSternal blood has an oxygen saturation suggesting a mixture of venous and arterial blood. Changes in SsO2 relate well with changes in SvO2 during hypovolaemia or hypoxia. Further studies on the feasibility of using non-invasive measurement of changes in SsO2 to estimate changes in SvO2 are warranted.© 2023. The Author(s).

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