NRNP 6567 Week 6 Hemodynamic Case Analysis Example

Hemodynamic Case Analysis: A Central Venous Pressure of 16 Against a Positive Passive Leg Raise, in Pancreatitis With Rising Abdominal Pressure

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College of Nursing, Walden University

NRNP 6567: Critical Care Immersion: Advanced Skills and Patient Management

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Month Day, Year

Hemodynamic Case Analysis: A Central Venous Pressure of 16 Against a Positive Passive Leg Raise, in Pancreatitis With Rising Abdominal Pressure

The Numbers in Conflict

Composite case, the same patient: 52 years old, gallstone pancreatitis with ARDS, ICU day 2, 10 hours after intubation. Ventilated with tidal volume 6 mL/kg of predicted body weight, positive end-expiratory pressure (PEEP) 12 cm of water, inspired oxygen 0.6. Norepinephrine 0.08 micrograms/kg per minute. Net fluid balance since admission: positive 7.2 liters.

Central venous pressure (CVP): 16 mm Hg, from a right internal jugular catheter, transduced at the phlebostatic axis, read at end-expiration. Taken at face value: the right heart is full; more fluid will not help.

Passive leg raising (PLR): cardiac output, estimated from the velocity-time integral of the left ventricular outflow tract by bedside echocardiography, rose from 3.9 to 4.5 liters per minute, 15%, within 90 seconds of raising the legs, and fell back when they were lowered. Taken at face value: he is fluid responsive.

Other values: mean arterial pressure 66 mm Hg; lactate 3.4 mmol/L, up from 2.6 four hours ago; urine output 15 to 20 mL per hour for 3 hours; intra-abdominal pressure by bladder transduction 14 mm Hg. The clinical picture matches neither number cleanly: he looks underfilled by lactate and urine output but has lungs full of fluid on imaging and a CVP that says the tank is full.

What Could Make Each Wrong

The CVP. Even when measured correctly, CVP predicts fluid responsiveness poorly: in a meta-analysis of 43 studies, the summary area under the curve for CVP predicting a response to fluid was 0.56, little better than chance (Marik & Cavallazzi, 2013). In this patient, three things raise it without any change in his need for fluid. PEEP of 12 cm of water raises intrathoracic pressure, which is transmitted to the right atrium. His intra-abdominal pressure of 14 mm Hg, which meets the consensus definition of intra-abdominal hypertension at 12 mm Hg or more (Kirkpatrick et al., 2013), pushes the diaphragm up and raises intrathoracic pressure further. And ARDS can raise pulmonary vascular resistance and right ventricular pressures. A CVP of 16 in this setting does not mean the left ventricle is full.

The passive leg raise. PLR-induced changes in cardiac output predicted fluid responsiveness with a pooled sensitivity of 0.85 and specificity of 0.91 in a meta-analysis, with the best threshold near a 10% rise (Monnet et al., 2016). But the test has its own ways to fail. Intra-abdominal hypertension impairs venous return from the legs, and in ventilated patients who did respond to fluid, those whose PLR was falsely negative had a median intra-abdominal pressure of 20 mm Hg, against 11.5 in those whose PLR correctly showed a response (Mahjoub et al., 2010). That failure mode produces false negatives, not false positives. The echocardiographic measurement can also be wrong if the probe angle changes between readings; the same operator took both measurements without moving the probe, and the value returned to baseline when the legs were lowered.

The Measurement Believed

The passive leg raise carries the analysis. It is a dynamic test of whether the heart increases its output when preload rises, which is the question actually being asked, while CVP is a static pressure distorted here by PEEP, abdominal pressure, and possibly the right ventricle. The known failure mode of PLR in intra-abdominal hypertension produces false negatives; his test was positive at an abdominal pressure of 14, so the direction of the error favors believing it. The rising lactate and falling urine output are consistent with a heart that has more to give.

Actions and Their Confirmation

1. A single small bolus, 250 mL of balanced crystalloid over 10 minutes, not a large volume. In acute pancreatitis, aggressive fluid resuscitation increased fluid overload without improving outcomes (de-Madaria et al., 2022), and his lungs are already wet. Confirmation within 15 minutes: velocity-time integral rises by at least 10%, matching the PLR; if it does not, no further fluid.

2. Watch the lungs with the bolus. Confirmation within 1 hour: oxygen saturation and the ratio of arterial oxygen to inspired oxygen do not fall; plateau pressure does not rise.

3. Watch the abdomen. Confirmation within 4 hours: intra-abdominal pressure remains below 16 mm Hg; if it rises, fluid is stopped and abdominal decompression measures begin, such as nasogastric decompression, sedation review, and a neutral fluid balance.

4. Judge perfusion. Confirmation within 2 hours: lactate falls by at least 10% and urine output rises above 0.5 mL/kg per hour; norepinephrine can be weaned toward a mean arterial pressure of 65.

If the Other Number Were True

If the CVP were believed as a sign that he was full, the plan would have been to withhold fluid, increase norepinephrine to raise the mean arterial pressure, and possibly start a diuretic for his lungs. That plan would have avoided adding water to his lungs and abdomen. But if the PLR is right, it would have left a preload-responsive heart underfilled, relied on vasopressor to raise pressure without raising flow, and risked worsening his lactate and his kidneys. The small bolus with a stated confirmation window tests the PLR's claim at the lowest cost, which is why it was chosen over either extreme.

References

de-Madaria, E., Buxbaum, J. L., Maisonneuve, P., García García de Paredes, A., Zapater, P., Guilabert, L., Vaillo-Rocamora, A., Rodríguez-Gandía, M. Á., Donate-Ortega, J., Lozada-Hernández, E. E., Collazo Moreno, A. J. R., Lira-Aguilar, A., Llovet, L. P., Mehta, R., Tandel, R., Navarro, P., Sánchez-Pardo, A. M., Sánchez-Marin, C., Cobreros, M., . . . Bolado, F. (2022). Aggressive or moderate fluid resuscitation in acute pancreatitis. The New England Journal of Medicine, 387(11), 989-1000. https://doi.org/10.1056/NEJMoa2202884

Kirkpatrick, A. W., Roberts, D. J., De Waele, J., Jaeschke, R., Malbrain, M. L., De Keulenaer, B., Duchesne, J., Bjorck, M., Leppaniemi, A., Ejike, J. C., Sugrue, M., Cheatham, M., Ivatury, R., Ball, C. G., Reintam Blaser, A., Regli, A., Balogh, Z. J., D'Amours, S., Debergh, D., . . . Olvera, C. (2013). Intra-abdominal hypertension and the abdominal compartment syndrome: Updated consensus definitions and clinical practice guidelines from the World Society of the Abdominal Compartment Syndrome. Intensive Care Medicine, 39(7), 1190-1206. https://doi.org/10.1007/s00134-013-2906-z

Mahjoub, Y., Touzeau, J., Airapetian, N., Lorne, E., Hijazi, M., Zogheib, E., Tinturier, F., Slama, M., & Dupont, H. (2010). The passive leg-raising maneuver cannot accurately predict fluid responsiveness in patients with intra-abdominal hypertension. Critical Care Medicine, 38(9), 1824-1829. https://doi.org/10.1097/CCM.0b013e3181eb3c21

Marik, P. E., & Cavallazzi, R. (2013). Does the central venous pressure predict fluid responsiveness? An updated meta-analysis and a plea for some common sense. Critical Care Medicine, 41(7), 1774-1781. https://doi.org/10.1097/CCM.0b013e31828a25fd

Monnet, X., Marik, P., & Teboul, J.-L. (2016). Passive leg raising for predicting fluid responsiveness: A systematic review and meta-analysis. Intensive Care Medicine, 42(12), 1935-1947. https://doi.org/10.1007/s00134-015-4134-1