A case report: a 22-year-old septic patient with central venous pO₂ of 198 mmHg

Central venous saturation and central venous pressure can be determined with central venous catheters. Therefore, the tip of the catheter should be located in the superior vena cava. The location can be monitored by electrocardiography or X-ray. The central venous pressure curve is displayed on the monitor. The reference value of central venous saturation is >70%. Venous pO₂ is normally 35-45 mmHg and central venous pressure 1-9 mmHg.

We treated a 22-year-old patient with septic shock. Central venous saturation was 100% with a pO₂ of 198 mmHg. The arterial blood gas analysis was comparatively low with saturation of 98% and pO₂ of 111 mmHg. On chest X-ray, the central venous catheter tip appeared on the left side of the heart. On echocardiography, aortic positioning was not evident. On the monitor, a 'venous pressure-like' curve was seen, that did not stand in exact correlation to the electrocardiogram curve. The computed tomography (CT) image showed placement of the catheter in the upper left pulmonary vein. The patient had a partial anomalous pulmonary venous return.

The C-wave of the central venous pressure curve normally occurs after the R-wave of the electrocardiogram. If C-waves appeared before R-waves, the central venous catheter placement is not central venous and must be checked. In our case, the apparent 'venous' pO₂ in blood gas examination was higher than arterial pO₂. The catheter position had to be in an oxygenated vessel proximal to the left ventricle. A vascular anomaly was a possible diagnosis and was confirmed on CT imaging.