The gastrointestinal tract: An underestimated organ as demonstrated in an experimental LVAD pig model

Background. Although hemodynamic stability and renal function are important and are monitored closely in patients with implanted left ventricular assist devices (LVAD), the gastrointestinal tract may be underestimated in the early postoperative period with regard to adequate perfusion. We investigated renal, intestinal, and whole body metabolic changes in response to variations in LVAD now and inspired oxygen concentration (FiO(2)). Methods. Left ventricular assist devices were implanted in 10 adult pigs (weight, 55 +/- 1.76 kg). Renal vein (RV), superior mesenteric vein (SMV), and pulmonary artery (PA) blood oxygen saturation and lactate concentration were measured and used as tissue perfusion markers. These measurements were made at baseline and after changes in LVAD now or FiO(2). Results. Oxygen saturation in the PA, SMV, and RV decreased significantly after a reduction in LVAD flow (p = 0.05), with a greater reduction in the SMV than in the PA and RV (p < 0.05 at LVAD flow 3.5 L/min; p < 0.01 at LVAD flow 2.0 and 1.0 L/min). The lactate concentration in the PA and SMV increased significantly (p < 0.01) with decreased flow, with a greater increase in the SMV than in the PA (p < 0.05), whereas it remained unchanged in the RV. Oxygen saturation in the PA, SMV, and RV decreased significantly after a reduction in FiO(2) (p < 0.05). Lactate concentration in the PA, SMV, and RV increased significantly at FiO(2) of 0.10 (p < 0.05). Lactate concentration in the PA and SMV was significantly higher than that in the RV at FiO(2) of 0.10 (p < 0.01). Conclusions. The results show that the gastrointestinal tract is at high risk during low perfusion or low FiO(2), whereas the kidneys' metabolic function appears to be less disturbed. In clinical practice, this emphasizes the need to ensure adequate blood now and respiratory function, especially after extubation, in patients with implanted LVAD. This might avoid intestinal ischemia and subsequent endotoxemia. Gastrointestinal tonometry may help in the assessment of intestinal perfusion.