Increased Hepatic Microvascular Density, Oxygenation, and VEGF in the Hypertrophic Lobe following Portal Vein Embolization in Rabbits

<b><i>Introduction:</i></b> The microvascular events following portal vein embolization (PVE) are poorly understood despite the pivotal role of the microcirculation in liver regeneration and tumor progression. We aimed to assess the changes in hepatic microvascular perfusion and neo-angiogenesis after experimental PVE. <b><i>Methods:</i></b> PVE of the cranial liver lobes was performed in 12 New Zealand White rabbits divided into 2 groups of permanent (P-PVE) and reversible PVE (R-PVE), respectively. Hepatobiliary scintigraphy and CT were used to evaluate hepatic function and volume. Hepatic microcirculation was assessed using a handheld vital microscope (Cytocam) to measure microvascular density (total vessel density; TVD) before PVE, right after PVE, and 20 min after PVE, as well as at 14 days (D14 post-PVE) and 35 days (D35 post-PVE). Additionally, on D35, microvascular PO₂ and liver parenchymal VEGF were assessed. <b><i>Results:</i></b> Eleven rabbits were included after PVE (R-PVE, <i>n</i> = 5; P-PVE, <i>n</i> = 6). TVD in the nonembo­lized (hypertrophic) lobes was higher than in the embolized (atrophic) lobes of the P-PVE group at D35 post-PVE (36.7 ± 7.2 vs. 23.4 ± 4.9 mm/mm²; <i>p</i> &#x3c; 0.05). In the R-PVE group, TVD in the nonembolized lobes was not increased at D35. Function and volume were increased in the nonembolized lobes of the P-PVE group compared to the embolized lobes, but not in the R-PVE group. Likewise, the mmicrovascular PO₂ and VEGF staining rate were higher in the nonembolized lobes of the P-PVE group at D35 post-PVE. <b><i>Discussion/Conclusion:</i></b> Successful volumetric and functional hypertrophy of the nonembolized lobe was accompanied by microvascular alterations featuring increased neo-angiogenesis, microvascular density, and microvascular oxygen pressure following P-PVE.

Intestinal Mucosal and Serosal Microcirculation at the Planned Anastomosis during Abdominal Surgery

Introduction: Intestinal blood flow is often named as a key factor in the pathophysiology of anastomotic leakage. The distribution between mucosal and serosal microperfusion during surgery remains to be elucidated. Objective: The aim of this study was to assess if the mucosal microcirculation of the intestine is more vulnerable to a surgical hit than the serosal microcirculation during surgery. Methods: In an observational cohort study (n = 9 patients), the microcirculation of the bowel serosa and mucosa was visualized with incident dark-field imaging during surgery. At the planned anastomosis, the following microcirculatory parameters were determined: microvascular flow index (MFI), percentage of perfused vessels (PPV), perfused vessel density (PVD), and total vessel density (TVD). Data are presented as median (interquartile range [IQR]). Results: Perfusion parameters and vessel density were significantly higher for the mucosa than the serosal microcirculation at the planned site for anastomosis or stoma. Mucosal MFI was 3.00 (IQR 3.00–3.00) compared to a serosal MFI of 2.75 (IQR 2.21–2.94), p = 0.03. The PPV was 99% (IQR 98–100) versus 92% (IQR 66–94), p = 0.01. The TVD was 16.77 mm/mm2 (IQR 13.04–18.01) versus 10.42 mm/mm2 (IQR 9.36–11.81), p = 0.01, and the PVD was 15.44 mm/mm2 (IQR 13.04–17.78) versus 9.02 mm/mm2 (IQR 6.43–9.43), p = 0.01. Conclusions: The mucosal microcirculation was preserved, while lower perfusion of the serosa was found at the planned anastomosis or stoma during surgery. Further research is needed to link our observations to the clinically relevant endpoint of anastomotic leakage.

Pregnancy at high altitude in the Andes leads to increased total vessel density in healthy newborns

The developing human fetus is able to cope with the physiological reduction in oxygen supply occurring in utero. However, it is not known if microvascularization of the fetus is augmented when pregnancy occurs at high altitude. Fifty-three healthy term newborns in Puno, Peru (3,840 m) were compared with sea-level controls. Pre- and postductal arterial oxygen saturation (SpO2) was determined. Cerebral and calf muscle regional tissue oxygenation was measured using near infrared spectroscopy (NIRS). Skin microcirculation was noninvasively measured using incident dark field imaging. Pre- and postductal SpO2 in Peruvian babies was 88.1 and 88.4%, respectively, which was 10.4 and 9.7% lower than in newborns at sea level ( P < 0.001). Cerebral and regional oxygen saturation was significantly lower in the Peruvian newborns (cerebral: 71.0 vs. 74.9%; regional: 68.5 vs. 76.0%, P < 0.001). Transcutaneously measured total vessel density in the Peruvian newborns was 14% higher than that in the newborns born at sea level (29.7 vs. 26.0 mm/mm2; P ≤ 0.001). This study demonstrates that microvascular vessel density in neonates born to mothers living at high altitude is higher than that in neonates born at sea level.