AJP - Heart and Circulatory Physiology, Vol 253, Issue 1 100-H106, Copyright © 1987 by American Physiological Society

ARTICLES

Postnatal changes in critical cardiac output and oxygen transport in conscious lambs

J. T. Fahey and G. Lister

We lowered cardiac output progressively in a controlled, stepwise fashion in conscious, unsedated lambs to determine the critical cardiac output or systemic oxygen delivery (the level at which oxygen consumption decreased abruptly). With the use of incremental inflation of a balloon-tipped catheter placed in the right atrium to lower cardiac output, we examined the response of oxygen consumption, systemic oxygen transport, fractional oxygen extraction, arterial lactate, and blood pressure. We studied lambs at 2 (n = 5), 4 (n = 5), and 8 wk (n = 6) of age and found that the 4-wk-old lambs reached critical values of cardiac output and systemic oxygen transport with the smallest proportional decreases from base-line values. Therefore, the 4-wk-old lambs were the least tolerant of acute decreases in cardiac output. We also found that fractional oxygen extraction was able to increase even after critical systemic oxygen transport was achieved. Furthermore, we found at every age that lactic acid accumulation began when the critical level of cardiac output was reached.

This article has been cited by other articles:

				F. J. Pearce, C. Waasdorp, H. Hufnagel, D. Burris, J. DeFeo, P. Soballe, and W. R. Drucker Subcutaneous PO2 as an index of the physiological limits for hemodilution in the rat J Appl Physiol, September 1, 2005; 99(3): 814 - 821. [Abstract] [Full Text] [PDF]

				B. S. Stonestreet, S. S. Ocampo, and W. Oh Reductions in cardiac output in hypoxic young pigs: systemic and regional perfusion and oxygen metabolism J Appl Physiol, September 1, 1998; 85(3): 874 - 882. [Abstract] [Full Text] [PDF]