Low inferior vena caval catheters for hemodynamic and pulmonary function monitoring in pediatric critical care patients

Objective: To assess the value of low inferior vena caval (LIVC) catheters for estimating central venous pressure in pediatric intensive care patients and to assess influences of intra-abdominal pressures and mean airway pressure on these measurements. Design: Prospective cohort of consecutive patients. Setting: Pediatric intensive care unit. Patients: Thirty patients ranging in age (18, 0-1 yrs; four, 1-3 yrs; four, 3-10 yrs; four, ≥10 yrs). Interventions: Interventions included catheterizations via internal jugular, subclavian, and common femoral veins, as well as direct right atrial catheterization during surgery; arterial catheter placement; airway pressure monitoring during mechanical ventilation; indirect intra-abdominal pressure monitoring via bladder catheter pressure readings; and arterial and central venous blood gas analysis. LIVC vein catheters were placed below the origin of the renal veins. Measurements and Main Results: LIVC pressure was highly correlated with central venous pressure (n=30, r²=.965, p=.0001). LIVC pressure did not correlate with intra-abdominal pressure (n=18, r²=.000). Mean airway pressure did not correlate with central venous pressure (n=11, r ²=.106). The pH of LIVC blood was similar to that of central venous blood (n=18, r²=.941, p=.0001). PCO₂ values of inferior vena cava and central venous blood correlated (r2=.945, p=.0001). However, agreement between inferior vena cava and central venous PO2 and oxyhemoglobin saturation was poor (PO2, r²=.066; oxyhemoglobin saturation, r ²=.000). Conclusions: LIVC catheters whose tips lie below the origin of the renal veins predict central venous pressure in pediatric intensive care unit patients. Intra-abdominal pressure and mean airway pressure do not affect this relationship, within the wide range of values for these variables included in this study. Blood samples drawn from femoral venous catheters can be used to monitor acid-base balance and partial pressure of carbon dioxide.