End-Expiratory Occlusion Test During Increase of Vasomotor Tone in a Rabbit Model of Hemorrhage

Abstract

end-expiratory occlusion test (eeot) has been proposed as a preload responsiveness test that overcomes several limitations of pulse pressure (ppV) and stroke volume (SVV) variations. We compared the ability of EEOT versus SVV and PPV to predict fluid responsiveness during the increase of the vasomotor tone in a rabbit model of hemorrhage. ten rabbits were anesthetized, paralyzed, and mechanically ventilated during basal load (BL), after progressive blood withdrawal (BW), and after volume replacement. other two sets of data were obtained during vasomotor increase by phenylephrine (pHe) infusion in BL and BW. We estimated the change of stroke volume (∆SV eeot ) and aortic flow (∆Aof eeot ) during the eeot. ppV and SVV were obtained by the variation of beat-tobeat pp and SV, respectively. Baseline ppV, SVV, ∆SV eeot , and ∆Aof eeot increased significantly after BW, with a decrease of aortic flow (P < 0.05). PHE induced a significant decrease of PPV and SVV, but without affecting ∆SV eeot , and ∆Aof eeot . We conclude that ∆SV and ∆Aof during eeot kept the ability to predict fluid responsiveness during PHE infusion in a rabbit hemorrhage model. This result may suggest the advantage of EEOT with respect to SVV and PPV in predicting fluid responsiveness during vasomotor tone increase.The main goal of fluid therapy is to correct hypovolemia avoiding both under and over-resuscitation, as well as the excessive use of inotropic and vasopressor drugs. Moreover, the comorbidities and type of disease determine that not all patients are volume responsive. The preload responsiveness should be assessed to decide both to administer fluid in the early resuscitation phase of shock states and to stop fluid administration in the de-escalation phase of shock management 1 . Several indices are available at the bedside to predict fluid responsiveness. Dynamic parameters based on heart-lung interactions have been proposed to predict fluid responsiveness and to promote more rational fluid administration 2 . Nevertheless, respiratory variations of stroke volume (SVV), pulse pressure (PPV), and vena cava diameter have numerous limitations that reduce their accuracy and applicability in clinical scenarios 3 . By interrupting cyclic ventilation at end-expiration for a few seconds (end-expiratory occlusion, EEO), abolishing the inspiratory increase in intrathoracic pressure, and by passive leg raising tests, we can produce a self-volume challenge and increase cardiac output (CO) by a rapid and reversible increase of venous return (VR) in those patients preload-responsive 4,5 . Both tests have shown an excellent predictive value keeping their accuracy in patients with cardiac arrhythmias, with spontaneous breathing activity, with low compliance of the respiratory system and independently of positive end-expiratory pressure in acute respiratory distress syndrome patients 6,7 . However, passive leg raising presents some false negatives in patients with intra-abdominal pressure ≥16 mmHg, is contra-indicated to perform in patients with head trauma ...