Superior vena caval and mixed venous oxyhemoglobin saturations in children recovering from open heart surgery
Related Experiment Videos
J Räsänen1, K Peltola, M Leijala
1Department of Anesthesiology, University of South Florida College of Medicine, Tampa, FL 33612-4799.
Insights
Superior vena caval (Scvo2) saturation is consistently lower than mixed venous (Svo2) saturation in children post-heart surgery. Scvo2 is unreliable for monitoring systemic oxygen balance, unlike Svo2.
Area of Science:
- Cardiology
- Pediatric Critical Care
- Physiology
Background:
- Assessing systemic oxygen supply/demand balance is crucial in pediatric post-cardiac surgery patients.
- Superior vena caval (Scvo2) and mixed venous (Svo2) oxyhemoglobin saturation are used to monitor oxygenation.
- The utility of Scvo2 as a surrogate for Svo2 in this population requires clarification.
Purpose of the Study:
- To compare simultaneous Scvo2 and Svo2 values in children recovering from open heart surgery.
- To evaluate the reliability of Scvo2 monitoring for systemic oxygen supply/demand balance.
Main Methods:
- Simultaneous Scvo2 and Svo2 samples were collected from 15 pediatric patients immediately post-operation and daily for 4 days.
- Cardiopulmonary function and support levels were monitored throughout the study period.
Main Results:
- Scvo2 was consistently lower than Svo2 in all patients.
- Immediately post-operation, 6 patients had low Scvo2 but normal Svo2.
- The difference between Scvo2 and Svo2 decreased significantly during the 4-day recovery period (P < 0.001).
Conclusions:
- Scvo2 is an inadequate substitute for Svo2 in calculating cardiopulmonary variables reflecting whole-body function in these patients.
- Scvo2 monitoring alone cannot reliably rule out oxygen supply/demand imbalance during early postoperative recovery.
- Potential causes for the Scvo2-Svo2 difference include intracardiac shunting or altered blood flow distribution.
Abstract:
Simultaneous superior vena caval (Scvo2) and mixed venous (Svo2) oxyhemoglobin saturation values in 15 children recovering from open heart surgery were compared to assess the value of superior vena caval blood samples in monitoring systemic oxygen supply/demand balance. Samples were obtained immediately following the operation and postoperatively every morning for 4 days. During the 4-day study period, the patients' cardiopulmonary functions improved, allowing partial weaning from respiratory and cardiovascular support. The lowest values of superior vena caval (46.7 +/- 8.4%) and mixed venous (63.7 +/- 10.9%) oxyhemoglobin saturation were measured immediately after the operation. At this time, 6 patients had abnormally low Scvo2 values, but normal Svo2 values. Both Scvo2 and Svo2 increased; the difference between them decreasing significantly during the study period (P less than 0.001). The results show that Scvo2 is consistently lower than Svo2 in children recovering from open heart surgery. This difference may be secondary to residual intracardiac left-to-right shunting of blood or to altered distribution of systemic blood flow. The saturation difference between the two venous samples decreases during postoperative recovery, making a superior vena caval blood sample an inadequate substitute for a mixed venous blood sample in calculating derived cardiopulmonary variables intended to reflect the function of the body as a whole. Because Scvo2 was frequently subnormal while Svo2 was in the normal range, monitoring of Svo2 could not be reliably used to rule out oxygen supply/demand imbalance during the early postoperative period in these patients.