The lung is usually considered to have one function, namely gas exchange. Another function of lung is pharmacokineti_c function, which the cells and enzymes of pulmonary vascular bed act to change biological activities of a variety of substances transported to them through pulmonary circulation. The pulmonary vasoconstrictor response to hypoxia is a part of a self-regulatory mechanism by which capillary blood flow is automatically adjusted to alveolar ventilation.
Some vasoactive substances mediate the hypoxic pulmonary vascular response, and prostaglandin F2a, which is used for uterine contraction during obstetric surgery, is considered to `potentiate the hypoxic pulmonary vasoconstriction. ,
The author investgated the cardiovascular effects of PF2a during one-long ventilation in Korean mongrel dogs. Dogs were anesthetized with pentobarbital, morphine and pancuronium and intubated with Rush endotracheal tube No. 6.5. One-lung ventilation was induced by deep right endobronchial intubation, which was confirmed by chest movement and abscence of breathing sound in the left lung. Prostaglandin F´2a in dose of 0.5, 1.0, 2.0 pg/kg/min was infused into peripheral vein.
The results were as follows:
I. One-lung ventilation group was compared with control group: The heart rate was decreased and M´PAP, PVR and SVR were increased. In blood gas, pH and P02 were decreased but PVCO2 and shunt were increased.
2. Prostaglandin F2a infusion groups were compared with one-lung ventilation group; The car-
diovascular function and blood gas changes were not effected by prostaglandin. F2a, but MPAP was increased with dose-dependent manner and PVR were increased in prostaglandin F2a in doses of 1.0, 2.0 g/kg/min infusion group. Thus hypoxic pulmonary vasoconstriction was found to be enhanced by usual dose of prostaglandin F2a (0.5 - 2.0 g/kg/min).
|