Abstract
We have developed a method to lower cardiac output (Q) instantaneously, reversibly, and in a controlled, stepwise fashion in conscious lambs, using a balloon tipped (Foley) catheter inflated in the right atrium. The hemodynamic and metabolic effects of selective lowering of Q in the conscious, unsedated lamb has not previously been reported. Under conditions of low Q, we studied lambs at 2 weeks (n=5), 4 weeks (n=6) and 8 weeks (n=5) of age to determine the critical Q necessary to decrease oxygen consumption (VO2) or increase lactate (L) production at each age. At each level of balloon inflation we measured: VO2, CO2 production (VCO2), venous hemoglobin concentration (Hb), heart rate, arterial L, and systemic and pulmonary arterial blood gases, % HbO2 and pressures. The actual critical Q varied between lambs at a given age, although it was lower in the older lambs. However, when Q was normalized to resting cardiac output (Qo), L production increased and VO2 decreased in all lambs whenever Q ≤ .6 Qo, thereby establishing a critical Q which was similar for all ages. Due to the wide differences with age in Hb and Qo, the critical systemic oxygen transport (SOT) also decreased with age from 15 (2 weeks) to 11 (8 weeks) mlO2/min kg. These data provide evidence of a critical Q in the young subject and provide a model for studying the metabolic effects of low Q in the conscious lamb. Furthermore, the relationship between VO2 and SOT determined here for low flow states is similar to that established previously for anemia and hypoxemia.
Article PDF
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Fahey, J., Lister, G. 175 DETERMINATION OF CRITICAL CARDIAC OUTPUT AND OXYGEN TRANSPORT WITH AGE IN THE CONSCIOUS LAMB. Pediatr Res 19, 140 (1985). https://doi.org/10.1203/00006450-198504000-00205
Issue Date:
DOI: https://doi.org/10.1203/00006450-198504000-00205