Alcohol Poisoning and Venous Hyperoxia

The effects of continuous and intermittent reduced speed modes on renal and intestinal perfusion in an ovine model

The effects of the continuous-flow output on renal and intestinal microcirculation have not been extensively studied. To address this, the Heartware HVAD pump loaded with continuous and intermittent reduced speed (IRS) modes was implanted in four sheep and then operated at low and high speeds to mimic partial and complete unloading of the left ventricle. Then microsphere and positron emission tomography/computed tomography (PET/CT) studies were used to assess renal and intestinal tissue perfusion at various pump speeds and flow modes as compared with baseline (pump off). Arterial and venous oxygen (T02) and carbon dioxide (TCO2) contents were measured to assess changes in intestinal metabolism. Renal and intestinal regional blood flows did not produce any significant changes compared with baseline values in either continuous or IRS modes and speeds. The venous TO2 and TCO2 significantly increased in continuous and IRS modes and speeds compared with baseline. Our data suggested that renal and intestinal tissue perfusions were not adversely affected by continuous and IRS modes either in partial or complete unloading. Intestinal venous hyperoxia and increased TCO2 may be the evidence of intestinal arteriovenous shunting along with increased intestinal tissue metabolism. Longer-term studies are warranted in chronic heart failure models.

Arterio-venous shunts or low oxygen utilization?

An idea of arteriovenous shunts (AVS) was proposed for explanation of dynamic regulation of oxygenation and venous hyperoxia. A formula enabling calculation of AVS and real CO 2 production has recently been derived by comparing data of arterial and venous blood gases. Regarding venous hyperoxia, there is a need to differentiate capillary to tissue transport defect (low oxygen utilisation-LOU) from AVS, which may exist simultaneously. The AVS may be associated with normal or relatively high oxygen utilization from the capillary vessels and increased CO2 production. AVS is proposed to carry protective and ‘stealing’ properties including renal, cardiac, and pulmonary hemodynamic. Calculations of the AVS may be important for dynamic assessment of vascular and metabolic status and in emergency medicine.