Gastrointestinal blood flow and oxygen delivery during environmental cold stress: Effect of anaemia

We studied the effect of environmental cold stress with and without isovolaemic anaemia on blood flow and oxygen delivery to the stomach, small intestine, and colon. The purpose of the study was to investigate the independent and combined effects of an increased oxygen demand (cold stress) and decreased oxygen availability (anaemia). Six, 3-4 days-old, awake piglets having normal haematocrit (26%), were studied in a warm environment (31.7 ± 0.4°C) and 30 min after reaching the nadir of cold stress (19.9 ± 0.4°C). Subsequently, a warm environment was reestablished and a partial volume, plasma exchange transfusion was done to lower the haematocrit to approximately 15%. Piglets were then studied as before in warm (32 ± 0.5°C) and cold (19.3 · 0.3°C) environments. In the non-anaemic study phase, cold stress provoked a decrease in blood flow (ml · 100 g^-1 · min^-1) to the small intestine (226 ± 22 vs. 134 ± 22) while oxygen delivery (ml O₂ · 100 g^-1 · min^-1) was decreased to the stomach (13.6 ± 1.4 vs 9.3 ± 1.7), small intestine (19.6 ± 0.6 vs. 11.2 ± 1.1) and colon (9.6 ± 1.7 vs. 6.1 ± 1.0). Following plasma exchange transfusion (anaemic study phase), warm environment values for gastrointestinal blood flow did not differ from non-anaemic warm environment values. However, mean oxygen delivery while in a warm environment was decreased to the stomach (-45%), small intestine (-49%) and colon (-42%). Among anaemic piglets, cold stress provoked a further decrease in oxygen delivery to the small intestine (9.9 ± 1.2 vs. 6.5 ± 0.9). During cold stress the oxygen delivery to the stomach and small intestine was lower in the anaemic study phase than in the non-anaemic study phase (-47% and -42%, respectively). Oxygen delivery was ≤ 6.5 ml O₂ · 100 g^-1 · min^-1 to the stomach, small intestine and colon during anaemia-cold stress. We conclude that compensatory increases in intestinal blood flow do not occur when oxygen availability is reduced by isovolaemic anaemia. Moreover, imposition of cold stress, creating an increased oxygen demand, further decreases oxygen delivery to the small intestine.