Abstract
Background: The role of pulsatile (PP) versus non-pulsatile (NP) flow during a cardiopulmonary bypass (CPB) is still debated. This study’s aim was to analyze hemodynamic effects, endothelial reactivity and erythrocytes response during a CPB with PP or NP. Methods: Fifty-two patients undergoing an aortic valve replacement were prospectively randomized for surgery with either PP or NP flow. Pulsatility was evaluated in terms of energy equivalent pressure (EEP) and surplus hemodynamic energy (SHE). Systemic (SVRi) and pulmonary (PVRi) vascular resistances, endothelial markers levels and erythrocyte nitric-oxide synthase (eNOS) activity were collected at different perioperative time-points. Results: In the PP group, the resultant EEP was 7.3% higher than the mean arterial pressure (MAP), which corresponded to 5150 ± 2291 ergs/cm3 of SHE. In the NP group, the EEP and MAP were equal; no SHE was produced. The PP group showed lower SVRi during clamp-time (p = 0.06) and lower PVRi after protamine administration and during first postoperative hours (p = 0.02). Lower SVRi required a higher dosage of norepinephrine in the PP group (p = 0.02). Erythrocyte eNOS activity results were higher in the PP patients (p = 0.04). Renal function was better preserved in the PP group (p = 0.001), whereas other perioperative variables were comparable between the groups. Conclusions: A PP flow during a CPB results in significantly lower SVRi, PVRi and increased eNOS production. The clinical impact of increased perioperative vasopressor requirements in the PP group deserves further evaluation.
Highlights
Despite continuous technological improvements in cardiac anesthesia, perfusion technique and myocardial protection, the conventional cardiopulmonary bypass (CPB) still remains a non-physiological scenario [1]
The mean arterial pressure (MAP) values within the circuit were comparable between the two groups and dropped progressively when measured at the pump outlet (219 ± 17 mm Hg in the PP group and 213 ± 38 mm Hg in the NP group, p = 0.57), at the post-oxygenator site (190 ± 22 and 172 ± 30 mmHg, respectively, p = 0.04) and at the entrance of the aortic cannula (107 ± 18 and 101 ± 17 mmHg, respectively, p = 0.31)
From the PP group, an 83-year-old patient died on the 57th postoperative day because of sepsis; the other patient from the NP group died on the 25th postoperative day because of pneumonia and respiratory failure
Summary
Despite continuous technological improvements in cardiac anesthesia, perfusion technique and myocardial protection, the conventional cardiopulmonary bypass (CPB) still remains a non-physiological scenario [1]. The shortcoming of a non-pulsatile flow consists of lower mechanical energy transmission to the vascular wall that results in decreased endothelial shear stress. The mechanical unloading of arterial baroreceptors leads to a marked increase in sympathetic activity with further progressive vasoconstriction and worsening of peripheral blood flow [2]. The lower mechanical energy of non-pulsatile flow reduces the synthesis of shear-responsive, endothelial-derived vasodilators such as nitric oxide. The role of pulsatile (PP) versus non-pulsatile (NP) flow during a cardiopulmonary bypass (CPB) is still debated. Systemic (SVRi) and pulmonary (PVRi) vascular resistances, endothelial markers levels and erythrocyte nitric-oxide synthase (eNOS) activity were collected at different perioperative time-points. Lower SVRi required a higher dosage of norepinephrine in the PP group (p = 0.02). Conclusions: A PP flow during a CPB results in significantly lower SVRi, PVRi and increased eNOS production. The clinical impact of increased perioperative vasopressor requirements in the PP group deserves further evaluation
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