Effects of phenylephrine on systemic and pulmonary artery pressure during sepsis-induced pulmonary hypertension in piglets.

The effects of intravenous phenylephrine (PE) on aortic blood pressure (AOP), pulmonary artery pressure (PAP), and cardiac output (CO) were evaluated in piglets with normal PAP and piglets with sepsis-induced pulmonary hypertension. Anesthetized, ventilated piglets (1-4 weeks; n = 22) were divided into four groups - group 1 (n = 5) received group B beta streptococci (GBS) followed by PE (300 micrograms/kg); group 2 (n = 6) received GBS alone; group 3 (n = 6) received placebo infusion; group 4 (n = 5) received PE alone (300 micrograms/kg). Infusion of GBS in piglets (groups 1 and 2) elevated PAP by 149 and 176%, reduced CO by 34 and 28%, and did not affect AOP. Administration of PE (groups 1 and 4) raised AOP by 30 and 27% without significantly affecting PAP. However, CO fell after PE by 31 and 39%, respectively. If selective elevation of systemic blood pressure is to become an effective strategy for human newborns with right-to-left shunts caused by sepsis-induced pulmonary hypertension, agents other than PE, with less associated reduction of CO, need to be identified.