A neonatal-pediatric specialist has inserted a balloon-tip, flow-directed pulmonary artery catheter and has recorded the following measurements: CVP 2 mmHg, PAP 8 mmHg (mean), PCWP 3 mmHg, Qt 2.5 L/min Which of the following is most likely cause of these results?

• A. High PEEP effects
• B. Hemorrhage
• C. Overhydration
• D. Pulmonary hypertension

Answer: (B)

The measurements point to very low preload from intravascular volume loss. Central venous pressure reflects right atrial/preload, and wedge pressure reflects left atrial/preload; both are markedly low here (CVP 2 mmHg, PCWP 3 mmHg), indicating reduced venous return and LV filling. A mean pulmonary artery pressure of 8 mmHg is also on the low side, consistent with diminished circulating volume and decreased overall cardiac output (Qt 2.5 L/min in a neonate/pediatric patient is low for their size). In this context, acute hemorrhage causing hypovolemia best explains the pattern of low filling pressures with a fall in cardiac output. By contrast, high PEEP tends to raise intrathoracic pressures and may elevate or alter filling pressures; pulmonary hypertension would raise pulmonary artery pressures, not produce these low values; and overhydration would raise both CVP and PCWP.