Continuous fiberoptic arterial and venous blood gas monitoring in hemorrhagic shock

Study objective: To compare the performance of continuous fiberoptic blood gas monitoring with standard, intermittent blood gas sampling in the measurement of arterial and central venous blood gases during marked hemodynamic changes. Design: Prospective, consecutive, enrollment, experimental study. Setting: Research laboratory at a university medical center. Participants: Seven anesthetized, mechanically ventilated pigs. Interventions: Severe shock was induced by hemorrhage in pigs monitored by a pulmonary artery catheter, an arterial line, and two fiberoptic blood gas sensors: one intra-arterial, and the other inserted into the superior vena cava via right internal jugular vein cutdown. Fiberoptic blood gas monitor measurements were compared with standard intermittent blood gas sampling. Measurements and results: A total of 184 blood gas samples were compared in seven animals at baseline, during shock, and after resuscitation. The baseline mean (±1 SD) cardiac output decreased from 4.0±0.9 to 1.2±0.6 L/min during shock and returned to baseline after retransfusion (3.9±1.3 L/min). The comparison of continuous fiberoptic blood gas monitoring with intermittent blood gas sampling showed a bias±precision of 0.035±0.047 for arterial pH, 0.021 ± 0.031 for central venous pH, -4.09±2.96 mm Hg (- 0.55±0.39 kPa) for arterial PCO₂, -3.67±2.44 mm Hg (-0.49±0.33 kPa) for central venous PCO₂, -5.79±9.64 mm Hg (-0.77±1.29 kPa) for arterial PO₂, and -7.85±8.52 mm Hg (-1.05±1.14 kPa) for central venous PO₂. Conclusions: Continuous fiberoptic blood gas monitoring agrees closely with standard intermittent blood gas sampling during severe hemodynamic shifts and has a comparable accuracy for both arterial and venous blood gas measurements. Changes in venous PCO₂ have recently been shown to correlate with changes in global tissue perfusion (eg, changes in cardiac output). Such data, available immediately via continuous venous blood gas monitoring, may be useful for monitoring shock and the response to resuscitation.