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

Objective: Especially in pediatric patients with severe hypothermia, intrao sseous access may be more readily available than intravascular access durin g an early phase of treatment and therefore, may be helpful to optimize man agement. The purpose of this study was to determine whether intraosseous bl ood gases are comparable with arterial, mixed venous, and sagittal sinus bl ood gases during different degrees of hypothermia. Design: Prospective, descriptive laboratory investigation using a porcine m odel. Setting: University hospital laboratory. Subjects: Twelve anesthetized, 12- to 16-wk-old domestic pigs weighing 30-3 5 kg. Interventions: Volume-controlled ventilated animals were instrumented with arterial, pulmonary artery, sagittal sinus, and 16-gauge intraosseous cathe ters. Blood samples were obtained from each site every 15 mins during surfa ce cooling with crushed ice until mean +/- SEM core temperature decreased f rom 38.5 +/- 0.1 degrees C [101.3 +/- 0.2 degrees F] to 27 +/- 0.5 degrees C [80.5 +/- 0.9 degrees F] over 2 hrs. Measurements and Main Results: Intraindividual correlation of PCO2 and pH v alues were determined as the difference (Delta) between intraosseous and re ference blood samples. With hypothermia, absolute values of PCO2 decreased and pH increased in samples from all sites. At 27 degrees C, intraosseous - arterial Delta PCO2 and Delta pH (mean +/- 95% confidence intervals) were 2.6 +/- 10.6 torr [0.35 +/- 1.4 kPa] and -0.11 +/- 0.07 units; intraosseous - mixed venous were 0.4 +/- 12.2 torr [0.05 +/- 1.6 kPa] and -0.06 +/- 0.0 8 units; and intraosseous - sagittal sinus were -7.3 +/- 16 torr [-0.97 +/- 2.1 kPa] and 0.001 +/- 0.14 units, respectively. Intraosseous PCO2 was not comparable to end-tidal values (Delta PCO2 17.4 +/- 14.6 torr [2.3 +/- 1.9 kPa]), and intraosseous lactate did not correlate with arterial, mixed ven ous, or sagittal sinus values. Conclusions: During hypothermia, intraosseous PCO2 values were predictable for mixed venous PCO2 and arterial PCO2. Intraosseous pH values also correl ated with mixed venous and sagittal sinus blood samples. Accordingly, inter pretation of blood gas values obtained from bone marrow aspirates may be he lpful to adjust ventilation and optimize fluid and drug therapy during the early treatment of patients with severe hypothermia.