Skin blood flow influences the transcutaneous PCO2 (tc PCO2) during stress in the guinea pig.
The transcutaneously measured carbon dioxide tension (tc PCO2) allows fetal monitoring in a continuous and non-invasive way. Though tc PCO2 is correlated well with the fetal acid-base balance, rather large variations in tc PCO2 exist. A decreased skin blood flow is known to influence the transcutaneous oxygen tension (tc PO2), and tc PCO2 might be affected in an equal way. During fetal asphyxia skin blood flow is extremely reduced. Thus, tc PCO2 might be affected by fetal asphyxia, which it is supposed to detect. To elucidate the role of reduced skin perfusion on tc PCO2, experiments on acutely instrumented guinea pigs were performed and skin perfusion was changed by injection of catecholamines. During control tc PCO2 was twice as high as the arterial PCO2 due to a reduced skin perfusion. After injection of catecholamines skin blood flow rose, tc PCO2 fell and the arterio-transcutaneous difference in PCO2 decreased. Then skin perfusion decreased and tc PCO2 increased. We conclude, that during stress situations with a low skin perfusion, as the acutely instrumented guinea pig, tc PCO2 is higher than the arterial PCO2 and can be influenced by changes in skin blood flow. These findings are relevant for the interpretation of tc PCO2 recordings during fetal asphyxia, where an extreme vasoconstriction exists.
Braems
G A
GA
Department of Obstetrics and Gynecology, Justus-Liebig-University Giessen, Fed. Rep. of Germany.
Lang
U
U
Künzel
W
W
D000818:Animals; D001783:Blood Flow Velocity; D001785:Blood Gas Monitoring, Transcutaneous; D002245:Carbon Dioxide / Q000097:blood*; D005189:False Positive Reactions; D006168:Guinea Pigs; D010100:Oxygen / Q000097:blood; D012867:Skin / Q000098:blood supply*; D013312:Stress, Physiological / Q000503:physiopathology*
D002245:Carbon Dioxide; D010100:Oxygen