Abstracts and Programme: EUROANAESTHESIA 2011: The European Anaesthesiology Congress: ESA Best Abstract Prize Competition (BAPC)
Background and Goal of Study: Norepinephrine (NE) infusion increases the arterial tone and the venous return through vasoconstriction. Thus, an improvement in cardiac output (CO) in preload dependant patients can be observed. The effects of NE on vascular tone may alter the reliability of the “fluid responsiveness dynamic indicators” which are usually beat-to-beat estimated with the pulse contour methods (PCM).
We examined the ability of pulse pressure variation (PPV) in discerning fluid responders and non responders in trauma brain injury (TBI) patients supported with NE infusion.
Materials and Methods: 24 TBI patients (18 male, mean age 54±22, weight 75±18 Kg) were prospectively enrolled. Inclusion criteria were: mechanical controlled ventilation (tidal volume ≥8ml/kg), absence of arrhythmias, absence of inotropes infusions, invasive arterial blood pressure monitoring, intracranial pressure monitoring. In all patients a cerebral perfusion pressure ≥ 70 mmHg was maintained with NE infusion.
After starting NE, patients were divided into two groups according to PPV values (baseline time): group 1 = PPV≤13% (unlikely responders to fluid load), and group 2 = PPV>13%.
When the NE dosage reached the value of 0.25 μg/kg/min (NEmax time), a fluid challenge of 5 ml/kg colloids was performed in the group 2 (likely responders to fluid load) to evaluate how many patients would have been responders (increase in CO ≥10%). CO was assessed by echocardiography and PPV was monitored by an uncalibrated PCM (MostCare, Vygon, Padova, Italy).
Results and Discussion: See data in Table.
With respect to baseline time, CO didn't change significantly compared to NEmax time. Conversely, NEmax time was significantly associated with a reduction of PPV in both the groups, with a greater extent in the group 2. After the fluid challenge in group 2, PPV and CO did not show a further significantly change as only two patients were responders.
Conclusion(s): The ability of PPV in discerning fluid responders and non responders is affected by norepinephrine. PPV guided therapy cannot be considered reliable during medium-high dose vasopressors therapy.