Does baseline ventriculo-arterial coupling predict stroke volume response to norepinephrine infusion in hypotensive postoperative cardiac surgery patients?
In hypotensive postoperative cardiac surgery patients, norepinephrine increases stroke volume only in those with altered baseline ventriculo-arterial coupling, which can be predicted by the arterial elastance to end-systolic ventricular elastance ratio.
Objectives: The objectives of the present study were to evaluate, in patients with persistent arterial hypotension in the immediate postcardiac surgery period, the effects of norepinephrine infusion on ventriculo-arterial coupling, its determinants: arterial elastance and end-systolic ventricular elastance, and to test the ability of arterial elastance to end-systolic ventricular elastance ratio to predict stroke volume increases. Design: Prospective observational study. Setting: Cardiac-vascular surgical ICU. Patients: Twenty-eight postoperative cardiac surgery patients, in whom physicians decided to administer norepinephrine infusion, were included. Measurements and Main Results: Arterial pressure, stroke volume index, cardiac index, indexed total peripheral resistance, arterial compliance, arterial elastance, and end-systolic ventricular elastance, were measured before and after norepinephrine infusion. We estimated ventriculo-arterial coupling by the arterial elastance to end-systolic ventricular elastance ratio and defined stroke volume responders by a stroke volume increase greater than or equal to 15%. Twenty-two of the 28 subjects had altered ventriculo-arterial coupling (1.87 1.57–2.51 vs 1.1 1–1.18). Fifteen of the 28 subjects (54%) were stroke volume responders. At baseline, stroke volume responders had similar arterial pressure, higher indexed total peripheral resistance, arterial elastance, arterial elastance to end-systolic ventricular elastance ratio (2.21 1.69–2.89 vs 1.33 1.1–1.56; p < 0.05), and lower arterial compliance, indexed total peripheral resistance and cardiac index. Norepinephrine significantly increased arterial pressure in all subjects. In stroke volume responders, norepinephrine increased arterial elastance, end-systolic ventricular elastance, cardiac index, and improved arterial elastance/end-systolic ventricular elastance coupling. The baseline arterial elastance to end-systolic ventricular elastance ratio predicted stroke volume responsiveness (area under the curve 95% CI, 0.87 0.71−1; p < 0.0001). Conclusions: In patients with arterial hypotension norepinephrine increased end-systolic ventricular elastance and arterial elastance. The effects of norepinephrine on stroke volume depend on baseline ventriculo-arterial coupling. Although norepinephrine infusion corrects arterial hypotension in all subjects, increase of stroke volume occurred only in subjects with altered ventriculo-arterial coupling.
Guinot et al. (Wed,) studied this question.